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  • 1.
    Adam, Rania E.
    et al.
    Department of Sciences and Technology, Linköping University, Norrköping, Sweden.
    Chalangar, Ebrahim
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Halmstad University, School of Business, Innovation and Sustainability, The Rydberg Laboratory for Applied Sciences (RLAS). Department of Sciences and Technology, Linköping University, Norrköping, Sweden.
    Pirhashemi, Mahsa
    Department of Chemistry, Faculty of Sciences, University of Mohaghegh Ardabili, Ardabil, Iran.
    Pozina, Galia
    Department of Physics, Chemistry, and Biology (IFM), Linköping University, Linköping, Sweden.
    Liu, Xianjie
    Department of Physics, Chemistry, and Biology (IFM), Linköping University, Linköping, Sweden.
    Palisaitis, Justinas
    Department of Physics, Chemistry, and Biology (IFM), Linköping University, Linköping, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Halmstad University, School of Business, Innovation and Sustainability, The Rydberg Laboratory for Applied Sciences (RLAS). Department of Sciences and Technology, Linköping University, Norrköping, Sweden & Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Willander, Magnus
    Department of Sciences and Technology, Linköping University, Norrköping, Sweden.
    Nur, Omer
    Department of Sciences and Technology, Linköping University, Norrköping, Sweden.
    Graphene-based plasmonic nanocomposites for highly enhanced solar-driven photocatalytic activities2019In: RSC Advances, E-ISSN 2046-2069, Vol. 9, no 52, p. 30585-30598Article in journal (Refereed)
    Abstract [en]

    High-efficiency photocatalysts are crucial for the removal of organic pollutants and environmental sustainability. In the present work, we report on a new low-temperature hydrothermal chemical method, assisted by ultrasonication, to synthesize disruptive plasmonic ZnO/graphene/Ag/AgI nanocomposites for solar-driven photocatalysis. The plasmonic nanocomposites were investigated by a wide range of characterization techniques, confirming successful formation of photocatalysts with excellent degradation efficiency. Using Congo red as a model dye molecule, our experimental results demonstrated a photocatalytic reactivity exceeding 90% efficiency after one hour simulated solar irradiation. The significantly enhanced degradation efficiency is attributed to improved electronic properties of the nanocomposites by hybridization of the graphene and to the addition of Ag/AgI which generates a strong surface plasmon resonance effect in the metallic silver further improving the photocatalytic activity and stability under solar irradiation. Scavenger experiments suggest that superoxide and hydroxyl radicals are responsible for the photodegradation of Congo red. Our findings are important for the fundamental understanding of the photocatalytic mechanism of ZnO/graphene/Ag/AgI nanocomposites and can lead to further development of novel efficient photocatalyst materials. © 2019 Elsevier B.V.

  • 2.
    Aghaeipour, Mahtab
    et al.
    Lund University, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Lund University, Lund, Sweden.
    Enhanced broadband absorption in nanowire arrays with integrated Bragg reflectors2018In: Nanophotonics, E-ISSN 2192-8614, Vol. 7, no 5, p. 819-825Article in journal (Refereed)
    Abstract [en]

    A near-unity unselective absorption spectrum is desirable for high-performance photovoltaics. Nanowire arrays are promising candidates for efficient solar cells due to nanophotonic absorption resonances in the solar spectrum. The absorption spectra, however, display undesired dips between the resonance peaks. To achieve improved unselective broadband absorption, we propose to enclose distributed Bragg reflectors (DBRs) in the bottom and top parts of indium phosphide (InP) nanowires, respectively. We theoretically show that by enclosing only two periods of In0.56Ga0.44As/InPDBRs, an unselective 78% absorption efficiency (72% for nanowires without DBRs)is obtained at normal incidence in the spectral range from 300 nm to 920 nm. Under oblique light incidence, the absorption efficiency is enhanced up to about 85% at an incidence angle of 50º. By increasing the number of DBR periods from two to five, the absorption efficiency is further enhanced up to 95% at normal incidence. In this work we calculated optical spectra for InP nanowires, but the results are expected to be valid for other direct band gap III-V semiconductor materials. We believe that our proposed idea of integrating DBRs in nanowires offers great potential for high-performance photovoltaic applications. ©2018 Håkan Pettersson et al., published by De Gruyter, Berlin/Boston.

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  • 3.
    Aghaeipour, Mahtab
    et al.
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS).
    Enhanced optical absorption in nanowires over a desire range of wavelengths2017In: MOC2017 : technical digest of the Twenty-Second Microoptics Conference: November 19-22, 2017, Institute of Industrial Science, The University of Tokyo, Japan, IEEE, 2017, Vol. 2017-November, p. 360-361Conference paper (Refereed)
    Abstract [en]

    Engineering optical absorption in nanowires, over a desire range of wavelengths is of importance to design high-performance nanowire-based photovoltaics. To this end, we integrate the nanowires with distributed Bragg reflectors to enhance absorption spectra of the nanowires and relate the consequent enhancement to increasing the optical path lengths of the modes. © 2017 The Japan Society of Applied Physics.

  • 4.
    Aghaeipour, Mahtab
    et al.
    Lund University, Lund, Sweden.
    Pistol, Mats-Erik
    Lund University, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Lund University, Lund, Sweden.
    Comparative study of absorption efficiency of inclined and vertical InP nanowires2017In: Physics, Simulation, and Photonic Engineering of Photovoltaic Devices VI / [ed] A. Freundlich, L. Lombez, M. Sugiyama, Bellingham, WA: SPIE - International Society for Optical Engineering, 2017, Vol. 10099, article id UNSP 100990SConference paper (Refereed)
    Abstract [en]

    Geometrically designed III-V nanowire arrays are promising candidates for optoelectronics due to their possibility to excite nanophotonic resonances in absorption spectra. Strong absorption resonances can be obtained by proper tailoring of nanowire diameter, length and pitch. Such enhancement of the light absorption is, however, accompanied by undesired resonance dips at specific wavelengths. In this work, we theoretically show that tilting of the nanowires mitigates the absorption dips by exciting strong Mie resonances. In particular, we derive a theoretical optimum inclination angle of about 30 degrees at which the inclined nanowires gain 8% in absorption efficiency compared to vertically standing nanowires in a spectral region matching the intensity distribution of the sun. The enhancement is due to engineering the excited modes inside the nanowires regarding the symmetry properties of the nanowire/light system without increasing the absorbing material. We expect our results to be important for nanowire-based photovoltaic applications. © 2017 SPIE.

  • 5.
    Aghaeipour, Mahtab
    et al.
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Pistol, Mats-Erik
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Considering Symmetry Properties of InP Nanowire/Light Incidence Systems to Gain Broadband Absorption2017In: IEEE Photonics Journal, E-ISSN 1943-0655, Vol. 9, no 3, article id 4501310Article in journal (Refereed)
    Abstract [en]

    Geometrically designed III-V nanowire arrays are promising candidates for disruptive optoelectronics due to the possibility of obtaining a strongly enhanced absorption resulting from nanophotonic resonance effects. With normally incident light on such vertical nanowire arrays, the absorption spectra exhibit peaks that originate from excitation of HE1m waveguide modes in the constituent nanowires. However, the absorption spectra typically show dips between the absorption peaks. Conventionally, such weak absorption has been counteracted by either making the nanowires longer or by decreasing the pitch of the array, both alternatives effectively increasing the volume of absorbing material in the array. Here, we first study two approaches for compensating the absorption dips by exciting additional Mie resonances: 1) oblique light incidence on vertical InP nanowire arrays and 2) normal light incidence on inclined InP nanowire arrays. We then show that branched nanowires offer a novel route to achieve broadband absorption by taking advantage of simultaneous excitations of Mie resonances in the branches and guided HE1m modes in the stem. Finite element method calculations show that the absorption efficiency is enhanced from 0.72 for vertical nanowires to 0.78 for branched nanowires under normal light incidence. Our work provides new insight for the development of novel efficient photovoltaics with high efficiency and reduced active material volume.

  • 6.
    Anokhina, Ksenia
    et al.
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Lund, Sweden.
    Graczyk, Mariousz
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Lund, Sweden.
    Kvennefors, Anders
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Lund, Sweden.
    Montelius, Lars
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Lund, Sweden.
    Maximov, Ivan
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Metal-assisted chemical etching of Si for fabrication of nanoimprint stamps2011Conference paper (Refereed)
  • 7.
    Bordag, Michael
    et al.
    Leipzig University, Institute for Theoretical Physics, Leipzig, Germany.
    Jede, Ralf
    Raith GmbH, Dortmund, Germany.
    Montelius, Lars
    Lunds University, Physics Department, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Riu, Jordi
    University Rovira i Vergili, Taragona, Spain.
    Schmucker, Ulrich
    University Rovira i Vergili, Taragona, Spain.
    Zubtsov, Michael
    Fraunhofer Institute for Factory Automation, Magdeburg, Germany.
    Parallel nano-assembly directed by short-range field forces2006In: Proceedings of the 1st IEEE International Conference on Nano/Micro Engineered and Molecular Systems, Piscataway, United States: IEEE Press, 2006, p. 620-622, article id 4135031Conference paper (Refereed)
    Abstract [en]

    We present the ECs Sixth Framework Programme PARNASS project, which stands for 'Parallel nano assembling directed by short-range field forces' and represents a radical innovative approach to fabricating large volumes of hybrid nano electronic devices. The project combines in a synergy the 'top-down' and 'bottom-up' methods addressing one of the challenging physical and engineering problems of the very high accuracy over a large area. An array of specially designed nano-scale force field sources has to be a key part of this innovative approach to large-scale nano manufacturing. © 2006 IEEE.

  • 8.
    Bordag, Michael
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Applied Mathematics and Physics (CAMP).
    Ribayrol, Aline
    Lund University.
    Conache, Gabriela
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Applied Mathematics and Physics (CAMP).
    Fröberg, Linus E.
    Lund University.
    Gray, Struan
    Lund University.
    Samuelson, Lars
    Lund University.
    Montelius, Lars
    Lund University.
    Pettersson, Håkan
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Applied Mathematics and Physics (CAMP).
    Shear stress measurements on InAs nanowires by AFM manipulation2007In: Small, ISSN 1613-6810, Vol. 3, no 8, p. 1398-1401Article in journal (Refereed)
    Abstract [en]

    On an upward curve? The curvature of an elastically deformed nanowire pinned to a flat surface contains information about the maximum static friction force, and hence the shear stress, between the nanowire and the surface. Here, InAs nanowires are bent in a controlled manner using the tip of an atomic force microscope (see image). The shear stress can be obtained from a simple analysis according to the standard theory of elasticity.

  • 9.
    Borschel, Christian
    et al.
    Institute for Solid State Physics, Jena University, Max-Wien-Platz 1, 07743 Jena, Germany.
    Messing, Maria
    Avd. f. Fasta tillståndets fysik, Lunds Universitet.
    Borgström, Magnus T.
    Avd. f. Fasta tillståndets fysik, Lunds Universitet.
    Paschoal, Waldomiro
    Avd. f. Fasta tillståndets fysik, Lunds Universitet / Tillämpad matematik och fysik (MPE-lab), MPE-lab.
    Wallentin, Jesper
    Avd. f. Fasta tillståndets fysik, Lunds Universitet.
    Kumar, Sandeep
    Avd. f. Fasta tillståndets fysik, Lunds Universitet.
    Mergenthaler, Kilian
    Avd. f. Fasta tillståndets fysik, Lunds Universitet.
    Deppert, Knut
    Avd. f. Fasta tillståndets fysik, Lunds Universitet.
    Canali, C. M.
    Högskolan i Kalmar.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Samuelson, Lars
    Avd. f. Fasta tillståndets fysik, Lunds Universitet.
    Ronning, Carsten
    Institute for Solid State Physics, Jena University, Max-Wien-Platz 1, 07743 Jena, Germany.
    A New Route toward Semiconductor Nanospintronics: Highly Mn-Doped GaAs Nanowires Realized by Ion-Implantation under Dynamic Annealing Conditions2011In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 11, no 9, p. 3935-3940Article in journal (Refereed)
    Abstract [en]

    We report on highly Mn-doped GaAs nanowires (NWs) of high crystalline quality fabricated by ion beam implantation, a technique that allows doping concentrations beyond the equilibrium solubility limit. We studied two approaches for the preparation of Mn-doped GaAs NWs: First, ion implantation at room temperature with subsequent annealing resulted in polycrystalline NWs and phase segregation of MnAs and GaAs. The second approach was ion implantation at elevated temperatures. In this case, the single-crystallinity of the GaAs NWs was maintained, and crystalline, highly Mn-doped GaAs NWs were obtained. The electrical resistance of such NWs dropped with increasing temperature (activation energy about 70 meV). Corresponding magnetoresistance measurements showed a decrease at low temperatures, indicating paramagnetism. Our findings suggest possibilities for future applications where dense arrays of GaMnAs nanowires may be used as a new kind of magnetic material system.

  • 10.
    Borschel, Christian
    et al.
    Institute for Solid State Physics, University of Jena, Jena, Germany.
    Messing, Maria
    Lund University, Lund, Sweden.
    Mergenthaler, Kilian
    Lund University, Lund, Sweden.
    Borgström, Magnus T.
    Lund University, Lund, Sweden.
    Paschoal, Waldomiro
    Lund University, Lund, Sweden.
    Wallentin, Jesper
    Lund University, Lund, Sweden.
    Kumar, Sandeep
    Lund University, Lund, Sweden.
    Deppert, Knut
    Lund University, Lund, Sweden.
    Canali, Carlo
    Linnaeus University, Kalmar, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Samuelson, Lars
    Lund University, Lund, Sweden.
    Ronning, Carsten
    Institute for Solid State Physics, University of Jena, Jena, Germany.
    A New Route towards Semiconductor Nanospintronics: Highly Mn-Doped GaAs Nanowires Realized by Ion-Implantation under Dynamic Annealing Conditions2011Conference paper (Refereed)
  • 11.
    Chalangar, Ebrahim
    et al.
    Halmstad University. Linköping University, Linköping, Sweden.
    Björk, Emma M.
    Linköping University, Linköping, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology. Linköping University, Linköping, Sweden; Nanolund, Lund, Sweden.
    Electrochemical investigation of carbon paper/ZnO nanocomposite electrodes for capacitive anion capturing2022In: Scientific Reports, E-ISSN 2045-2322, Vol. 12, no 1, article id 11843Article in journal (Refereed)
    Abstract [en]

    In this work, we demonstrate an effective anion capturing in an aqueous medium using a highly porous carbon paper decorated with ZnO nanorods. A sol–gel technique was first employed to form a thin and compact seed layer of ZnO nanoparticles on the dense network of carbon fibers in the carbon paper. Subsequently, ZnO nanorods were successfully grown on the pre-seeded carbon papers using inexpensive chemical bath deposition. The prepared porous electrodes were electrochemically investigated for improved charge storage and stability under long-term operational conditions. The results show effective capacitive deionization with a maximum areal capacitance of 2 mF/cm2, an energy consumption of 50 kJ per mole of chlorine ions, and an excellent long-term stability of the fabricated C-ZnO electrodes. The experimental results are supported by COMSOL simulations. Besides the demonstrated capacitive desalination application, our results can directly be used to realize suitable electrodes for energy storage in supercapacitors. © 2022, The Author(s).

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  • 12.
    Chalangar, Ebrahim
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Linköping University, Norrköping, Sweden.
    Machhadani, Houssaine
    Linköping University, Linköping, Sweden.
    Lim, Seung-Hyuk
    Linköping University, Linköping, Sweden.
    Karlsson, K. Fredrik
    Linköping University, Linköping, Sweden.
    Nur, Omer
    Linköping University, Norrköping, Sweden.
    Willander, Magnus
    Linköping University, Norrköping, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Linköping University, Norrköping, Sweden & Lund University, Lund, Sweden.
    Influence of morphology on electrical and optical properties of graphene/Al-doped ZnO-nanorod composites2018In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 29, no 41, article id 415201Article in journal (Refereed)
    Abstract [en]

    The development of future 3D-printed electronics relies on the access to highly conductive inexpensive materials that are printable at low temperatures (<100 C). The implementation of available materials for these applications are, however, still limited by issues related to cost and printing quality. Here, we report on the simple hydrothermal growth of novel nanocomposites that are well suited for conductive printing applications. The nanocomposites comprise highly Al-doped ZnO nanorods grown on graphene nanoplatelets (GNPs). The ZnO nanorods play the two major roles of (i) preventing GNPs from agglomerating and (ii) promoting electrical conduction paths between the graphene platelets. The effect of two different ZnO-nanorod morphologies with varying Al-doping concentration on the nanocomposite conductivity and the graphenedispersity are investigated. Time-dependent absorption, photoluminescence and photoconductivity measurements show that growth in high pH solutions promotes a better graphene dispersity, higher doping levels and enhanced bonding between the graphene and the ZnO nanorods. Growth in low pH solutions yields samples characterized by a higher conductivity and a reduced number of surface defects. These samples also exhibit a large persistent photoconductivity attributed to an effective charge separation and transfer from the nanorods to the graphene platelets. Our findings can be used to tailor the conductivity of novel printable composites, or for fabrication of large volumes of inexpensive porous conjugated graphene-semiconductor composites. © 2018 IOP Publishing Ltd.

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  • 13.
    Chalangar, Ebrahim
    et al.
    Halmstad University. Linköping University, Linkoping, Sweden.
    Mustafa, Elfatih
    Linköping University, Linkoping, Sweden.
    Nur, Omer
    Linköping University, Linkoping, Sweden.
    Willander, Magnus
    Linköping University, Linkoping, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology. Linköping University, Linkoping, Sweden; Nanolund, Lund, Sweden.
    Nanopatterned rGO/ZnO: Al seed layer for vertical growth of single ZnO nanorods2023In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 34, no 25, p. 1-7, article id 255301Article in journal (Refereed)
    Abstract [en]

    In this work, we demonstrate a novel low-cost template-assisted route to synthesize vertical ZnO nanorod arrays on Si (100). The nanorods were grown on a patterned double seed layer comprised of reduced graphene oxide (rGO) and Al-doped ZnO nanoparticles. The seed layer was fabricated by spray-coating the substrate with graphene and then dip-coating it into a Al-doped ZnO sol-gel solution. The growth template was fabricated from a double-layer resist, spin-coated on top of the rGO/ZnO:Al seed layer, and patterned by colloidal lithography. The results show a successful chemical bath deposition of vertically aligned ZnO nanorods with controllable diameter and density in the nanoholes in the patterned resist mask. Our novel method can presumably be used to fabricate electronic devices on virtually any smooth substrate with a thermal budget of 1 min at 300 °C with the seed layer acting as a conductive strain-relieving back contact. The top contact can simply be made by depositing a suitable transparent conductive oxide or metal, depending on the specific application. © 2023 The Author(s). Published by IOP Publishing Ltd.

  • 14.
    Chalangar, Ebrahim
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Department of Science and Technology, Linköping University, Norrköping, Sweden.
    Nur, Omer
    Department of Science and Technology, Linköping University, Norrköping, Sweden.
    Willander, Magnus
    Department of Science and Technology, Linköping University, Norrköping, Sweden.
    Gustafsson, Anders
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Department of Science and Technology, Linköping University, Norrköping, Sweden & Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Synthesis of Vertically Aligned ZnO Nanorods Using Sol-gel Seeding and Colloidal Lithography Patterning2021In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 16, no 1, article id 46Article in journal (Refereed)
    Abstract [en]

    Different ZnO nanostructures can be grown using low-cost chemical bath deposition. Although this technique is cost-efficient and flexible, the final structures are usually randomly oriented and hardly controllable in terms of homogeneity and surface density. In this work, we use colloidal lithography to pattern (100) silicon substrates to fully control the nanorods' morphology and density. Moreover, a sol-gel prepared ZnO seed layer was employed to compensate for the lattice mismatch between the silicon substrate and ZnO nanorods. The results show a successful growth of vertically aligned ZnO nanorods with controllable diameter and density in the designated openings in the patterned resist mask deposited on the seed layer. Our method can be used to fabricate optimized devices where vertically ordered ZnO nanorods of high crystalline quality are crucial for the device performance. © 2021 BioMed Central Ltd

  • 15.
    Conache, Gabriela
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Gray, Struan M.
    Avd. f. Fasta tillståndets fysik, Lunds Universitet.
    Bordag, Michael
    Institute for Theoretical Physics, Leipzig University.
    Ribayrol, Aline
    Avd. f. Fasta tillståndets fysik, Lunds Universitet.
    Fröberg, Linus
    Avd. f. Fasta tillståndets fysik, Lunds Universitet.
    Samuelson, Lars
    Avd. f. Fasta tillståndets fysik, Lunds Universitet.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Montelius, Lars
    Avd. f. Fasta tillståndets fysik, Lunds Universitet.
    AFM-based manipulation of InAs nanowires2008In: Proceedings of the IVC-17 (17th International Vacuum Congress) [also] ICSS-13 (13th International Conference on Surface Science) [also] ICN+T-2007 (International Conference on Nanoscience and Technology): 2-6 July 2007, Stockholm, Sweden, Bristol: Institute of Physics (IOP), 2008, Vol. 100, no 5, 1, p. 052051-052051-4Conference paper (Refereed)
    Abstract [en]

    A controlled method of manipulation of nanowires was found using the tip of an Atomic Force Microscope (AFM). Manipulation is done in the ‘Retrace Lift’ mode, where feedback is turned off for the reverse scan and the tip follows a nominal path. The effective manipulation force during the reverse scan can be changed by varying an offset in the height of the tip over the surface. Using this method, we have studied InAs nanowires on different substrates. We have also investigated interactions between wires and with gold features patterned onto the substrates.

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  • 16.
    Conache, Gabriela
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Applied Mathematics and Physics (CAMP).
    Gray, Struan M.
    Solid State Physics/Nanometer Consortium, Lund University, Box 118, S-221 00, Lund, Sweden.
    Ribayrol, Aline
    Solid State Physics/Nanometer Consortium, Lund University, Box 118, S-221 00, Lund, Sweden.
    Fröberg, Linus E.
    Solid State Physics/Nanometer Consortium, Lund University, Box 118, S-221 00, Lund, Sweden.
    Samuelson, Lars
    Solid State Physics/Nanometer Consortium, Lund University, Box 118, S-221 00, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Applied Mathematics and Physics (CAMP).
    Montelius, Lars
    Solid State Physics/Nanometer Consortium, Lund University, Box 118, S-221 00, Lund, Sweden.
    Friction measurements of InAs nanowires on Silicon nitride by AFM manipulation2009In: Small, ISSN 1613-6810, Vol. 5, no 2, p. 203-207Article in journal (Refereed)
    Abstract [en]

    A study was conducted to perform friction measurements of InAs nanowires (NW) on silicon nitride (Si 3N 4) through atomic force microscopy (AFM) manipulation. The investigations revealed the friction force per unit length for sliding and static friction over a range of nanowire diameters. It was found that there is a significant difference between the coefficients of the two sliding modes for large wires. It was also found that the difference between the two sliding modes disappears at smaller diameters and the sliding friction becomes equal with the static friction. The AFM investigations were performed on a Nanoscope IIIa Dimension 3100, using rectangular cantilevers, with a nominal spring constant of 30 N m -1. The nanowires were manipulated, using the 'Retrace Lift' mode of the AFM controller. The friction force per unit length was gathered from the local curvature of the NWs, using standard elasticity theory.

  • 17.
    Conache, Gabriela
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Gray, Struan M.
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Sweden.
    Ribayrol, Aline
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Sweden.
    Fröberg, Linus
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Sweden.
    Samuelson, Lars
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Sweden.
    Montelius, Lars
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Comparative friction measurements of InAs nanowires on three substrates2010In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 108, no 9, p. 094307-094307-5Article in journal (Refereed)
    Abstract [en]

    We have investigated friction between InAs nanowires and three different substrates: SiO2, fluorosilanized SiO2, and Si3N4. The nanowires were pushed laterally with the tip of an atomic force microscope and the friction force per unit length for both static and sliding friction was deduced from the equilibrium shape of the bent wires. On all three substrates, thick wires showed a difference between sliding and static friction of up to three orders of magnitude. Furthermore, all substrates display a transition to stick-slip motion for nanowires with a diameter of less than about 40 nm. Hydrophobic and hydrophilic substrates display similar friction behavior suggesting that a condensed water layer does not strongly influence our results. The patterns and trends in the friction data are similar for all three substrates, which indicates that they are more fundamental in character and not specific to a single substrate. ©2010 American Institute of Physics.

  • 18.
    Conache, Gabriela
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Lund University, Solid State Physics/Nanometer Consortium, Box 118, S-221 00, Lund, Sweden.
    Gray, Struan M.
    Lund University, Solid State Physics/Nanometer Consortium, Box 118, S-221 00, Lund, Sweden.
    Ribayrol, Aline
    Lund University, Solid State Physics/Nanometer Consortium, Box 118, S-221 00, Lund, Sweden.
    Fröberg, Linus
    Lund University, Solid State Physics/Nanometer Consortium, Box 118, S-221 00, Lund, Sweden.
    Samuelson, Lars
    Lund University, Solid State Physics/Nanometer Consortium, Box 118, S-221 00, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Montelius, Lars
    Lund University, Solid State Physics/Nanometer Consortium, Box 118, S-221 00, Lund, Sweden.
    Nanowire friction with an applied bias2009Conference paper (Refereed)
    Abstract [en]

    Recently, we have shown how the friction acting on nanowires pushed across a surface by an AFM tip can be determined by measuring the radius of curvature of the bent wire aŸer manipulation. This technique allows us to study the friction properties of an extended mesoscale contact. Our main focus has been to determine whether such contacts behave like macroscopic objects, in which dišerences between the 'true' and 'apparent' contact areas play a key role and friction varies linearly with the applied normal force, or whether they are more like atomic-scale point contacts, wheremore fundamental processes dominate and friction oŸen is independent of the normal force. In this work we show how the friction between InAs nanowires and an insulating silicon nitride layer on a conductive silicon substrate varies when a DC voltage is applied to the AFM tip during manipulation. e tip charges the capacitor formed by the wire and the grounded silicon back contact, giving rise to attractive Coulomb forces and thus increasing the contact pressure between the wire and the silicon nitride. In this way we can vary the normal force on the sliding surfaces using a single wire, with a constant structure and contact geometry. Using nanowires of about 40-50 nm diameter and a few microns in length we have applied tip voltages in the range +12 to -12 V. Simplemodeling indicates that these voltages su›ce to give similar levels of band-lling and depletion to when the same wires are used in working wrap-gate or back-gate devices. A monotonic increase of the sliding friction with the voltage applied on the tip was observed. is implies that the friction increases with the normal force and that this mesoscopic system behaves more like a macroscopic contact, despite the nanometer size of the contact in the direction of motion.

  • 19.
    Conache, Gabriela
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Ribayrol, Aline
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Sweden.
    Fröberg, Linus
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Sweden.
    Borgström, Magnus T.
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Sweden.
    Samuelson, Lars
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Sweden.
    Montelius, Lars
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Gray, Struan M.
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Sweden.
    Bias-controlled friction of InAs nanowires on a silicon nitride layer studied by atomic force microscopy2010In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 82, no 3Article in journal (Refereed)
    Abstract [en]

    By studying how nanowires lying on a surface bend when pushed by an atomic force microscopy tip we are able to measure the friction between them and the substrate. Here, we show how the friction between InAs nanowires and an insulating silicon nitride layer varies when a dc voltage is applied to the tip during manipulation. The bias charges the capacitor formed by the wire and the grounded silicon back contact. Electrostatic forces increase the contact pressure and allow us to tune the friction between the wire and the silicon nitride surface. Using nanowires of about 40-70 nm diameter and a few microns in length we have applied biases in the range +12 to -12 V. A monotonic increase of the sliding friction with voltage was observed. This increase in friction with the normal force implies that the mesoscopic nanowire-surface system behaves like a macroscopic contact, despite the nanometer size of the contact in the direction of motion. The demonstrated bias-controlled friction has potential applications in MEMS/NEMS devices.

  • 20.
    Corrêa Jr, Gregório B.
    et al.
    Instituto Federal de Educação, Ciência e Tecnologia do Pará, Abaetetuba, PA, Brazil & Programa de Pós-Graduação em Física, Universidade Federal do Pará, Belém, PA, Brazil & .
    Kumar, Sandeep
    Department of Physics, Central University of Rajasthan, Ajmer, India.
    Paschoal Jr, Waldomiro
    Programa de Pós-Graduação em Física, Universidade Federal do Pará, Belém, PA, Brazil.
    Devi, Chandni
    Department of Physics, Central University of Rajasthan, Ajmer, India.
    Jacobsson, Daniel
    Department of Chemistry, Lund University, Lund, Sweden.
    Johannes, Andreas
    Institut für Festkörperphysik, Friedrich-Schiller-Universität Jena, Jena, Germany.
    Ronning, Carsten
    Institut für Festkörperphysik, Friedrich-Schiller-Universität Jena, Jena, Germany.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Halmstad University, School of Business, Engineering and Science, The Rydberg Laboratory for Applied Sciences (RLAS). Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Paraguassu, Waldeci
    Programa de Pós-Graduação em Física, Universidade Federal do Pará, Belém, PA, Brazil.
    Raman characterization of single-crystalline Ga0.96Mn0.04As:Zn nanowires realized by ion-implantation2019In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 30, no 33, article id 335202Article in journal (Refereed)
    Abstract [en]

    Recent progress in the realization of magnetic GaAs nanowires (NWs) doped with Mn has attracted a lot of attention due to their potential application in spintronics. In this work, we present a detailed Raman investigation of the structural properties of Zn doped GaAs (GaAs:Zn) and Mn-implanted GaAs:Zn (Ga0.96Mn0.04As:Zn) NWs. A significant broadening and redshift of the optical TO and LO phonon modes are observed for these NWs compared to as-grown undoped wires, which is attributed to strain induced by the Zn/Mn doping and to the presence of implantation-related defects. Moreover, the LO phonon modes are strongly damped, which is interpreted in terms of a strong LO phonon-plasmon coupling, induced by the free hole concentration. Moreover, we report on two new interesting Raman phonon modes (191 and 252 cm −1) observed in Mn ion-implanted NWs, which we attribute to Eg (TO) and A1g (LO) vibrational modes in a sheet layer of crystalline arsenic present on the surface of the NWs. This conclusion is supported by fitting the observed Raman shifts for the SO phonon modes to a theoretical dispersion function for a GaAs NW capped with a dielectric shell. © 2019 IOP Publishing Ltd.

  • 21.
    Devi, Chandni
    et al.
    Central University of Rajasthan, Ajmer, India.
    Gellanki, Jnaneswari
    Central University of Rajasthan, Ajmer, India.
    Pettersson, Håkan
    Halmstad University, School of Business, Innovation and Sustainability, The Rydberg Laboratory for Applied Sciences (RLAS). Lund University, Lund, Sweden.
    Kumar, Sandeep
    Central University of Rajasthan, Ajmer, India.
    High sodium ionic conductivity in PEO/PVP solid polymer electrolytes with InAs nanowire fillers2021In: Scientific Reports, E-ISSN 2045-2322, Vol. 11, no 1, article id 20180Article in journal (Refereed)
    Abstract [en]

    Solid-state sodium ion batteries are frequently referred to as the most promising technology for next-generation energy storage applications. However, developing a suitable solid electrolyte with high ionic conductivity, excellent electrolyte–electrode interfaces, and a wide electrochemical stability window, remains a major challenge. Although solid-polymer electrolytes have attracted great interest due to their low cost, low density and very good processability, they generally have significantly lower ionic conductivity and poor mechanical strength. Here, we report on the development of a low-cost composite solid polymer electrolyte comprised of poly(ethylene oxide), poly(vinylpyrrolidone) and sodium hexafluorophosphate, mixed with indium arsenide nanowires. We show that the addition of 1.0% by weight of indium arsenide nanowires increases the sodium ion conductivity in the polymer to 1.50 × 10−4 Scm−1 at 40 °C. In order to explain this remarkable characteristic, we propose a new transport model in which sodium ions hop between close-spaced defect sites present on the surface of the nanowires, forming an effective complex conductive percolation network. Our work represents a significant advance in the development of novel solid polymer electrolytes with embedded engineered ultrafast 1D percolation networks for near-future generations of low-cost, high-performance batteries with excellent energy storage capabilities. © 2021, The Author(s).

  • 22.
    Devi, Chandni
    et al.
    Department of Physics, Central University of Rajasthan, Ajmer, India.
    Singhal, Rahul
    Department of Physics, Malaviya National Institute of Technology, Jaipur, India.
    Silva, Kleber Da
    Centro de Ciências Naturais e Tecnologia;, Universidade Do Estado Do Pará, Belém, PA, Brazil.
    Paschoal, Waldomiro
    Programa de Pós-Graduação em Física, Universidade Federal Do Pará, Belém, PA, Brazil.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Kumar, Sandeep
    Department of Physics, Central University of Rajasthan, Ajmer, India.
    Electrical transport properties of InAs nanowires synthesized by a solvothermal method2020In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 31, no 23, article id 235709Article in journal (Refereed)
    Abstract [en]

    Nanowires are widely considered to be key elements in future disruptive electronics and photonics. This paper presents the first detailed study of transport mechanisms in single-crystalline InAs nanowires synthesized by a cheap solvothermal wet chemical method. From detailed analyses of temperature-dependent current-voltage characteristics, it was observed that contacted nanowires operate in a linear transport regime at biases below a critical cross-over voltage. For larger biases, the transport changes to space-charge-limited conduction assisted by traps. The characteristic parameters such as free electron concentration, trap concentration and energy distribution, and electron mobility were all calculated. It was demonstrated that the nanowires have key electrical properties comparable to those of InAs nanowires grown by molecular beam epitaxy. Our results might pave the way for cheap disruptive low-dimensional electronics such as resistive switching devices. © 2020 IOP Publishing Ltd.

  • 23.
    Fu, Y.
    et al.
    Physical Electronics and Photonics, Department of Physics, Chalmers University of Technology and Gothenburg University, Göteborg, Sweden.
    Willander, M.
    Physical Electronics and Photonics, Department of Physics, Chalmers University of Technology and Gothenburg University, Göteborg, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS).
    Reduced effective temperature of hot electrons in nano-sized metal-oxide-semiconductor field-effect transistors2003In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 77, no 6, p. 799-803Article in journal (Refereed)
    Abstract [en]

    Hot electron effects have been extensively studied in metal-oxide-semiconductor field-effect transistors (MOSFETs). The importance of these effects when the dimensions are drastically reduced has so far not been thoroughly investigated. The scope of this paper is therefore to present a detailed study of the effective temperature of excess electrons in nanoscale MOSFETs by solving coupled Schrödinger and Poisson equations. It is found that the increased doping levels and reduced junction depths lead to substantially higher local Fermi levels in the source and drain regions. As a result, the temperature difference between electrons injected into the drain and local electrons is reduced. The scaling of the gate oxide thickness, as well as the drain voltage furthermore reduces the electron temperature in the drain. The detrimental effects of hot electron injection are therefore expected to be decreased by scaling the MOSFET.

  • 24.
    Gooth, Johannes
    et al.
    Institute of Nanostructure and Solid State Physics, Universität Hamburg, Hamburg, Germany & IBM Research-Zurich, Rüschlikon, Switzerland.
    Zierold, Robert
    Institute of Nanostructure and Solid State Physics, Universität Hamburg, Hamburg, Germany.
    Sergelius, Philip
    Institute of Nanostructure and Solid State Physics, Universität Hamburg, Hamburg, Germany.
    Hamdou, Bacel
    Institute of Nanostructure and Solid State Physics, Universität Hamburg, Hamburg, Germany.
    Garcia, Javier
    Institute for Metallic Materials, IFW Dresden, Dresden, Germany.
    Damm, Christine
    Institute for Metallic Materials, IFW Dresden, Dresden, Germany.
    Rellinghaus, Bernd
    Institute for Metallic Materials, IFW Dresden, Dresden, Germany.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Division of Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Pertsova, Anna
    Department of Physics and Electrical Engineering, Linnaeus University, Kalmar, Sweden.
    Canali, Carlo
    Department of Physics and Electrical Engineering, Linnaeus University, Kalmar, Sweden.
    Borg, Mattias
    IBM Research-Zurich, Rüschlikon, Switzerland.
    Nielsch, Kornelius
    Institute of Nanostructure and Solid State Physics, Universität Hamburg, Hamburg, Germany & Institute for Metallic Materials, IFW Dresden, Dresden, Germany.
    Local Magnetic Suppression of Topological Surface States in Bi2Te3 Nanowires2016In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 10, no 7, p. 7180-7188Article in journal (Refereed)
    Abstract [en]

    Locally induced, magnetic order on the surface of a topological insulator nanowire could enable room-temperature topological quantum devices. Here we report on the realization of selective magnetic control over topological surface states on a single facet of a rectangular Bi2Te3 nanowire via a magnetic insulating Fe3O4 substrate. Low-temperature magnetotransport studies provide evidence for local time-reversal symmetry breaking and for enhanced gapping of the interfacial 1D energy spectrum by perpendicular magnetic-field components, leaving the remaining nanowire facets unaffected. Our results open up great opportunities for development of dissipation-less electronics and spintronics. © 2016 American Chemical Society.

  • 25.
    Hussain, Laiq
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Karimi, Mohammad
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Berg, Alexander
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Jain, Vishal
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Borgström, Magnus T.
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Gustafsson, Anders
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Samuelson, Lars
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Defect-induced infrared electroluminescence from radial GaInP/AlGaInP quantum well nanowire array light- emitting diodes2017In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 28, no 48, article id 485205Article in journal (Refereed)
    Abstract [en]

    Radial GaInP/AlGaInP nanowire array light-emitting diodes (LEDs) are promising candidates for novel high-efficiency solid state lighting due to their potentially large strain-free active emission volumes compared to planar LEDs. Moreover, by proper tuning of the diameter of the nanowires, the fraction of emitted light extracted can be significantly enhanced compared to that of planar LEDs. Reports so far on radial growth of nanowire LED structures, however, still point to significant challenges related to obtaining defect-free radial heterostructures. In this work, we present evidence of optically active growth-induced defects in a fairly broad energy range in vertically processed radial GaInP/AlGaInP quantum well nanowire array LEDs using a variety of complementary experimental techniques. In particular, we demonstrate strong infrared electroluminescence in a spectral range centred around 1 eV (1.2 μm) in addition to the expected red light emission from the quantum well. Spatially resolved cathodoluminescence studies reveal a patchy red light emission with clear spectral features along the NWs, most likely induced by variations in QW thickness, composition and barriers. Dark areas are attributed to infrared emission generated by competing defect-assisted radiative transitions, or to trapping mechanisms involving non-radiative recombination processes. Possible origins of the defects are discussed. © 2017 IOP Publishing Ltd

  • 26.
    Hussain, Laiq
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS).
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Wang, Q.
    Acreo Swedish ICT AB, Kista, Sweden.
    Karim, A.
    Acreo Swedish ICT AB, Kista, Sweden.
    Anderson, J.
    Acreo Swedish ICT AB, Kista, Sweden.
    Jafari, Mehrdad
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Song, J.
    Center for Opto-Electronic Convergence Systems, Korea Institute of Science and Technology, Seoul, South Korea.
    Choi, W. J.
    Center for Opto-Electronic Convergence Systems, Korea Institute of Science and Technology, Seoul, South Korea.
    Han, I. K.
    Center for Opto-Electronic Convergence Systems, Korea Institute of Science and Technology, Seoul, South Korea.
    Lim, J. Y.
    Center for Opto-Electronic Convergence Systems, Korea Institute of Science and Technology, Seoul, South Korea.
    SWIR-LWIR Photoluminescence from Sb-based Epilayers Grown on GaAs Substrates by using MBE2018In: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 73, no 11, p. 1604-1611Article in journal (Refereed)
    Abstract [en]

    Utilizing Sb-based bulk epilayers on large-scale low-cost substrates such as GaAs for fabricating infrared (IR) photodetectors is presently attracting significant attention worldwide. For this study, three sample series of GaAsxSb1−x, In1−xGaxSb, and InAsxSb1x with different compositions were grown on semi-insulating GaAs substrates by using molecular beam epitaxy (MBE) and appropriate InAs quantum dots (QDs) as a defect-reduction buffer layer. Photoluminescence (PL) signals from these samples were observed over a wide IR wavelength range from 2 μm to 12 μm in agreement with the expected bandgap, including bowing effects. In particular, interband PL signals from InAsxSb1−x and In1−xGaxSb samples even at room temperature show promising potential for IR photodetector applications.

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  • 27.
    Höglund, Linda
    et al.
    Acreo AB, Kista, Sweden.
    Asplund, Carl
    Acreo AB, Kista, Sweden.
    Wang, Qin
    Acreo AB, Kista, Sweden.
    Almqvist, Susanne
    Acreo AB, Kista, Sweden.
    Malm, Hedda L.
    Acreo AB, Kista, Sweden.
    Petrini, Erik
    Acreo AB, Kista, Sweden.
    Andersson, Jan Y.
    Acreo AB, Kista, Sweden.
    Holtz, Per Olof
    Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, Sweden .
    Pettersson, Håkan
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Origin of photocurrent in lateral quantum dots-in-a-well infrared photodetectors2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 88, no 21, p. 213510-Article in journal (Refereed)
    Abstract [en]

    Interband and intersubband transitions of lateral InAs/In0.15Ga0.85As dots-in-a-well quantum dot infrared photodetectors were studied in order to determine the origin of the photocurrent. The main intersubband transition contributing to the photocurrent (PC) was associated with the quantum dot ground state to the quantum well excited state transition. By a comparison between intersubband PC measurements and the energy level scheme of the structure, as deduced from Fourier transform photoluminescence (FTPL) and FTPL excitation spectroscopies, the main transition contributing to the PC was identified.

  • 28.
    Höglund, Linda
    et al.
    Acreo AB.
    Holtz, Per Olof
    Linköping University.
    Pettersson, Håkan
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Applied Mathematics and Physics (CAMP).
    Asplund, C.
    IRnova.
    Wang, Q.
    Acreo AB.
    Almqvist, S.
    Acreo AB.
    Smuk, S.
    IRnova.
    Petrini, E.
    Acreo AB.
    Andersson, J. Y.
    Acreo AB.
    Bias and temperature dependence of the escape processes in quantum dots-in-a-well infrared photodetectors2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 93, no 10, p. 103501-Article in journal (Refereed)
    Abstract [en]

    The performance of quantum dots-in-a-well infrared photodetectors (DWELL IPs) has been studied by means of interband and intersubband photocurrent measurements as well as dark current measurements. Using interband photocurrent measurements, substantial escape of electrons from lower lying states in the DWELL structure at large biases was revealed. Furthermore, a significant variation in the escape probability from energy states in the DWELL structure with applied bias was observed. These facts can explain the strong temperature and bias dependence of both photocurrent and dark currents in DWELL IPs.

  • 29.
    Höglund, Linda
    et al.
    Acreo AB.
    Holtz, Per Olof
    Linköping University.
    Pettersson, Håkan
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Applied Mathematics and Physics (CAMP).
    Asplund, C.
    IRnova.
    Wang, Q.
    Acreo AB.
    Malm, H.
    IRnova.
    Almqvist, S.
    Acreo AB.
    Petrini, E.
    Acreo AB.
    Andersson, J. Y.
    Acreo AB.
    Bias mediated tuning of the detection wavelength in asymmetrical quantum dots-in-a-well infrared photodetectors2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 93, no 20, p. 203512-Article in journal (Refereed)
    Abstract [en]

    Bias-mediated tuning of the detection wavelength within the infrared wavelength region is demonstrated for quantum dots-in-a-well and dots-on-a-well infrared photodetectors. By positioning the InAs quantum dot layer asymmetrically in an 8 nm wide In0.15Ga0.85As/GaAs quantum well, a shift in the peak detection wavelength from 8.4 to 10.3 μm was observed when reversing the polarity of the applied bias. For a dots-on-a-well structure, the peak detection wavelength was tuned from 5.4 to 8 μm with small changes in the applied bias. These tuning properties could be essential for applications such as modulators and dual-color infrared detection.

  • 30.
    Höglund, Linda
    et al.
    Acreo AB.
    Holtz, Per Olof
    Linköping University.
    Pettersson, Håkan
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Applied Mathematics and Physics (CAMP).
    Asplund, C.
    IRnova.
    Wang, Q.
    Acreo AB.
    Malm, H.
    IRnova.
    Almqvist, S.
    Acreo AB.
    Petrini, E.
    Acreo AB.
    Andersson, J. Y.
    Acreo AB.
    Optical pumping as artificial doping in quantum dots-in-a-well infrared photodetectors2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 94, no 5, p. 053503-Article in journal (Refereed)
    Abstract [en]

    Resonant optical pumping across the band gap was used as artificial doping in InAs/In0.15Ga0.85As/GaAs quantum dots-in-a-well infrared photodetectors. A selective increase in the electron population in the different quantum dot energy levels enabled the low temperature photocurrent peaks observed at 120 and 148 meV to be identified as intersubband transitions emanating from the quantum dot ground state and the quantum dot excited state, respectively. The response was increased by a factor of 10 through efficient filling of the quantum dot energy levels by simultaneous optical pumping into the ground states and the excited states of the quantum dots.

  • 31.
    Höglund, Linda
    et al.
    Acreo AB, Kista, Sweden.
    Holtz, Per-Olof
    Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, Sweden.
    Asplund, Carl
    IRnova, Kista, Sweden.
    Wang, Qin
    Acreo AB, Kista, Sweden.
    Almqvist, Susanne
    Acreo AB, Kista, Sweden.
    Malm, Hedda
    IRnova, Kista, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Andersson, Jan Yngve
    Acreo AB, Kista, Sweden.
    Dual source optical pumping experiments revealing the origin of low temperature photocurrent peaks in quantum dots-in-a-well infrared photodetectors2008Conference paper (Refereed)
  • 32.
    Höglund, Linda
    et al.
    Acreo AB, Kista, Sweden & Linköping University, Linköping, Sweden.
    Holtz, Per-Olof
    Linköping University, Linköping, Sweden.
    Asplund, Carl
    IRnova, Kista, Sweden.
    Wang, Qin
    Acreo AB, Kista, Sweden.
    Almqvist, Susanne
    Acreo AB, Kista, Sweden.
    Petrini, Erik
    Acreo AB, Kista, Sweden.
    Andersson, Jan Y.
    Acreo AB, Kista, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Lund University, Lund, Sweden.
    Tuning of the detection wavelength in quantum dots-in-a-well infrared photodetectors2008In: Proceedings of SPIE, 6940, Infrared Technology and Applications XXXIV, 694002, 2008, Vol. 6940, no 1-2, article id 694002Conference paper (Refereed)
    Abstract [en]

    In this study, bias mediated tuning of the detection wavelength within the infrared wavelength region is demonstrated for quantum dots-in-a-well (DWELL) infrared photodetectors. In DWELL structures, intersubband transitions in the conduction band occur from a discrete state in the quantum dot to a subband inthe quantum well. Compared to "conventional" quantum dot infrared photodetectors, where the transitions take place between different discrete bands in thequantum dots, new possibilities to tune the detection wavelength window are opened up, partly by varying the quantum dot energy levels and partly by adjusting the width and composition of the quantum well. In the DWELL structure used, an asymmetric positioning of the InAs quantum dot layer in a 8 nm wide In0.15Ga0.85As/GaAs QW has been applied which enables tuning of the peak detection wavelength within the long wavelength infrared (LWIR; 8 - 14 gm) region. When the applied bias was reversed, a wavelength shift from 8.5 to 9.5 mu m was observed for the peak position in the spectral response. For another DWELL structure, with a well width of 2 nm, the tuning range of the detector could be shifted from the medium wavelength infrared (MWIR; 3-5 mu m) region to the LWIR region. With small changes in the applied bias, the peak detection wavelength could be shifted from 5.1 to 8 mu m. These tuning properties ofDWELL structures could be essential for applications such as modulators and two-colour infrared detection. © (2008) COPYRIGHT SPIE--The International Society for Optical Engineering.

  • 33.
    Höglund, Linda
    et al.
    Acreo AB, Kista, Sweden.
    Holtz, Per-Olof
    IFM, Linköping University, Linköping, Sweden.
    Asplund, Carl
    IRnova AB, Kista, Sweden.
    Wang, Qin
    Acreo AB, Kista, Sweden.
    Almqvist, Susanne
    Acreo AB, Kista, Sweden.
    Petrini, Erik
    Acreo AB, Kista, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Andersson, Jan Y.
    Acreo AB, Kista, Sweden.
    Voltage mediated tuning of the detection wavelength in quantum dots-in-a-well infrared photodetectors2008Conference paper (Refereed)
  • 34.
    Höglund, Linda
    et al.
    Industrial Nano- and Microtechnology, Acreo AB, Kista, Sweden.
    Holtz, Per-Olof
    Department of Physics, Chemistry and Biology (LFM), Linköping University, Linköping, Sweden.
    Ouattara, L.
    Synchrotron Radiation Research, Lund University, Lund, Sweden.
    Asplund, Carl
    IRnova, Kista, Sweden.
    Wang, Qin
    Industrial Nano- and Microtechnology, Acreo AB, Kista, Sweden.
    Almqvist, Susanne
    Industrial Nano- and Microtechnology, Acreo AB, Kista, Sweden.
    Petrini, Erik
    Industrial Nano- and Microtechnology, Acreo AB, Kista, Sweden.
    Malm, Hedda
    IRnova, Kista, Sweden.
    Borglind, J.
    Industrial Nano- and Microtechnology, Acreo AB, Kista, Sweden.
    Smuk, S.
    Industrial Nano- and Microtechnology, Acreo AB, Kista, Sweden.
    Mikkelsen, A.
    Synchrotron Radiation Research, Lund University, Lund, Sweden.
    Lundgren, E.
    Synchrotron Radiation Research, Lund University, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Solid State Physics and the Nanometer Consortium, Lund University, Lund, Sweden.
    Andersson, Jan Y.
    Industrial Nano- and Microtechnology, Acreo AB, Kista, Sweden.
    Quantum dots-in-a-well infrared photodetectors for long wavelength infrared detection2006In: Proceedings of SPIE: The International Society for Optical Engineering / [ed] James G. Grate, Francois Kajzar & Mikael lindgren, Bellingham, Wash.: SPIE - International Society for Optical Engineering, 2006, p. U51-U63Conference paper (Refereed)
    Abstract [en]

    We report on a quantum dots-in-a-well infrared photodetector (DWELL QDIP) grown by metal organic vapor phase epitaxy. The DWELL QDIP consisted of ten stacked InAs/In0.5Ga0.85As/GaAs QD layers embedded between n-doped contact layers. The density of the QDs was about 9 × 10 10 cm-2 per QD layer. The energy level structure of the DWELL was revealed by optical measurements of interband transitions, and from a comparison with this energy level scheme the origin of the photocurrent peaks could be identified. The main intersubband transition contributing to the photocurrent was associated with the quantum dot ground state to the quantum well excited state transition. The performance of the DWELL QDIPs was evaluated regarding responsivity and dark current for temperatures between 15 K and 77 K. The photocurrent spectrum was dominated by a LWIR peak, with a peak wavelength at 8.4 μm and a full width at half maximum (FWHM) of 1.1 μm. At an operating temperature of 65 K, the peak responsivity was 30 mA/W at an applied bias of 4 V and the dark current was 1.2×10-5 A/cm2. Wavelength tuning from 8.4 μm to 9.5 μm was demonstrated, by reversing the bias of the detector.

  • 35.
    Höglund, Linda
    et al.
    Acreo AB.
    Holtz, Per-Olof
    IFM, Linköping University.
    Pettersson, Håkan
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Asplund, Carl
    IRnova.
    Wang, Qin
    Acreo AB.
    Almqvist, Susanne
    Acreo AB.
    Malm, Hedda
    IRnova.
    Petrini, Erik
    Acreo AB.
    Andersson, Jan
    Acreo AB.
    Selective optical doping to predict the performance and reveal the origin of photocurrent peaks in quantum dots-in-a-well infrared photodetectors2009In: Infrared physics & technology, ISSN 1350-4495, E-ISSN 1879-0275, Vol. 52, no 6, p. 272-275Article in journal (Refereed)
    Abstract [en]

    Resonant optical pumping across the band gap was used as artificial doping in InAs/In0.15Ga0.85As/GaAs quantum dots-in-a-well infrared photodetectors. Through efficient filling of the quantum dot energy levels by simultaneous optical pumping into the ground states and the excited states of the quantum dots, the response was increased by a factor of 10. Low temperature photocurrent peaks observed at 120 and 148 meV were identified as intersubband transitions emanating from the quantum dot ground state and the quantum dot excited state, respectively by a selective increase of the electron population in the different quantum dot energy levels.

  • 36.
    Höglund, Linda
    et al.
    Acreo AB.
    Karlsson, Fredrik
    IFM, Linköping University.
    Holtz, Per-Olof
    IFM, Linköping University.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Pistol, Mats-Erik
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet.
    Wang, Qin
    Acreo AB.
    Almqvist, Susanne
    Acreo AB.
    Asplund, Carl
    IRnova.
    Malm, Hedda
    IRnova.
    Petrini, Erik
    Acreo AB.
    Andersson, Jan
    Acreo AB.
    Energy level scheme of InAs/InxGa1-xAs/GaAs quantum-dots-in-a-well infrared photodetector structures2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 82, no 3, p. 035314-Article in journal (Refereed)
    Abstract [en]

    A thorough investigation of quantum-dots-in-a-well structures for infrared photodetector applications has been performed employing different experimental techniques. The electronic structure of self-assembled InAs quantum dots embedded in an In0.15Ga0.85As/GaAs quantum well (QW) was deduced from photoluminescence (PL) and PL excitation (PLE) spectroscopy. From polarization-dependent PL it was revealed that the quantum dots hold two electron energy levels and two heavy-hole levels. Tunnel capacitance spectroscopy confirmed an electron energy level separation of about 50 meV, and additionally, that the conduction-band ground state and excited state of the dots are twofold and fourfold degenerates, respectively. Intersubband photocurrent spectroscopy, combined with simultaneous interband pumping of the dots, revealed a dominant transition at 150 meV (8.5 mu m) between the ground state of the quantum dots and the excited state of the QW. Results from detailed full three-dimensional calculations of the electronic structure, including effects of composition intermixing and interdot interactions, confirm the experimentally unravelled energy level scheme of the dots and well.

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  • 37.
    Iakovleva, Natalia
    et al.
    Petrozavodsk State University, Russia.
    Kokatev, Alexander
    Petrozavodsk State University.
    Pettersson, Håkan
    Petrozavodsk State University, Russia.
    Savchenko, O.
    Petrozavodsk State University, Russia.
    Iakovlev, A.
    Petrozavodsk State University, Russia.
    Chupakhina, E.
    Petrozavodsk State University, Russia.
    Suomolajnen, K.
    Petrozavodsk State University, Russia.
    Stepanova, K.
    Petrozavodsk State University, Russia.
    Khanina, E.
    Petrozavodsk State University, Russia.
    Self-organized porous anodic oxide matrix and nanocomposite materials on their base2011Conference paper (Refereed)
  • 38.
    Jafari Jam, Reza
    et al.
    Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Heurlin, Magnus
    Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Jain, Vishal
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Kvennefors, Anders
    Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Graczyk, Mariusz
    Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Maximov, Ivan
    Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Borgström, Magnus T.
    Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Samuelson, Lars
    Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    III-V nanowire synthesis by use of electrodeposited gold particles2015In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 15, no 1, p. 134-138Article in journal (Refereed)
    Abstract [en]

    Semiconductor nanowires are great candidates for building novel electronic devices. Considering the cost of fabricating such devices, substrate reuse and gold consumption are the main concerns. Here we report on implementation of high throughput gold electrodeposition for selective deposition of metal seed particles in arrays defined by lithography for nanowire synthesis. By use of this method, a reduction in gold consumption by a factor of at least 300 was achieved, as compared to conventional thermal evaporation for the same pattern. Because this method also facilitates substrate reuse, a significantly reduced cost of the final device is expected. We investigate the morphology, crystallography, and optical properties of InP and GaAs nanowires grown from electrodeposited gold seed particles and compare them with the properties of nanowires grown from seed particles defined by thermal evaporation of gold. We find that nanowire synthesis, as well as the material properties of the grown nanowires are comparable and quite independent of the gold deposition technique. On the basis of these results, electrodeposition is proposed as a key technology for large-scale fabrication of nanowire-based devices.

  • 39.
    Jafari Jam, Reza
    et al.
    Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Heurlin, Magnus
    Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Kvennefors, Anders
    Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Graczyk, Mariusz
    Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Jain, Vishal
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Borgström, Magnus T.
    Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Samuelson, Lars
    Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Maximov, Ivan
    Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Nanoimprint Lithography and Gold Electroplating for Nanowire Seed Particle Definition2013Conference paper (Refereed)
  • 40.
    Jain, Vishal
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Heurlin, Magnus
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Barrigon, Enrique
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Bosco, Lorenzo
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Nowzari, Ali
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Schroff, Shishi
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Boix, Virginia
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Karimi, Mohammad
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Jafari Jam, Reza
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Berg, Alexander
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Samuelson, Lars
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Borgström, Magnus T.
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Capasso, Federico
    School of Engineering and Applied Sciences, Harvard University, Cambridge, United States.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    InP/InAsP Nanowire-Based Spatially Separate Absorption and Multiplication Avalanche Photodetectors2017In: ACS Photonics, E-ISSN 2330-4022, Vol. 4, no 11, p. 2693-2698Article in journal (Refereed)
    Abstract [en]

    Avalanche photodetectors (APDs) are key components in optical communication systems due to their increased photocurrent gain and short response time as compared to conventional photodetectors. A detector design where the multiplication region is implemented in a large band gap material is desired to avoid detrimental Zener tunneling leakage currents, a concern otherwise in smaller band gap materials required for absorption at 1.3/1.55 μm. Self-assembled III-V semiconductor nanowires offer key advantages such as enhanced absorption due to optical resonance effects, strain-relaxed heterostructures, and compatibility with mainstream silicon technology. Here, we present electrical and optical characteristics of single InP and InP/InAsP nanowire APD structures. Temperature-dependent breakdown characteristics of p+-n-n+ InP nanowire devices were investigated first. A clear trap-induced shift in breakdown voltage was inferred from I-V measurements. An improved contact formation to the p+-InP segment was observed upon annealing, and its effect on breakdown characteristics was investigated. The band gap in the absorption region was subsequently varied from pure InP to InAsP to realize spatially separate absorption and multiplication APDs in heterostructure nanowires. In contrast to the homojunction APDs, no trap-induced shifts were observed for the heterostructure APDs. A gain of 12 was demonstrated for selective optical excitation of the InAsP segment. Additional electron-beam-induced current measurements were carried out to investigate the effect of local excitation along the nanowire on the I-V characteristics. Simulated band profiles and electric field distributions support our interpretation of the experiments. Our results provide important insight for optimization of avalanche photodetector devices based on III-V nanowires. © 2017 American Chemical Society

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  • 41.
    Jain, Vishal
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Solid State Physics and Nano, Lund University, Lund, Sweden.
    Heurlin, Magnus
    Solid State Physics and Nano, Lund University, Lund, Sweden.
    Karimi, Mohammad
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Solid State Physics and Nano, Lund University, Lund, Sweden.
    Hussain, Laiq
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Solid State Physics and Nano, Lund University, Lund, Sweden.
    Aghaeipour, Mahtab
    Solid State Physics and Nano, Lund University, Lund, Sweden.
    Nowzari, Ali
    Solid State Physics and Nano, Lund University, Lund, Sweden.
    Berg, Alexander
    Solid State Physics and Nano, Lund University, Lund, Sweden.
    Nylund, Gustav
    Solid State Physics and Nano, Lund University, Lund, Sweden.
    Capasso, Federico
    Harvard University, Cambridge, United States of America.
    Samuelson, Lars
    Solid State Physics and Nano, Lund University, Lund, Sweden.
    Borgström, Magnus T.
    Solid State Physics and Nano, Lund University, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Solid State Physics and Nano, Lund University, Lund, Sweden.
    Bias-dependent spectral tuning in InP nanowire-based photodetectors2017In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 28, no 11, article id 114006Article in journal (Refereed)
    Abstract [en]

    Nanowire array ensembles contacted in a vertical geometry are extensively studied and considered strong candidates for next generations of industrial scale optoelectronics. Key challenges in this development deal with optimization of the doping profile of the nanowires and the interface between nanowires and transparent top contact. Here we report on photodetection characteristics associated with doping profile variations in InP nanowire array photodetectors. Bias-dependent tuning of the spectral shape of the responsivity is observed which is attributed to a Schottky-like contact at the nanowire-ITO interface. Angular dependent responsivity measurements, compared with simulated absorption spectra, support this conclusion. Furthermore, electrical simulations unravel the role of possible self-gating effects in the nanowires induced by the ITO/SiOx wrap-gate geometry. Finally, we discuss possible reasons for the observed low saturation current at large forward biases.  

  • 42.
    Jain, Vishal
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Heurlin, Magnus
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Lindgren, David
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Nowzari, Ali
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Hussein, Laiq
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Wallentin, Jesper
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Capasso, Federico
    School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA.
    Borgström, Magnus T.
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Gustafsson, Anders
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Samuelson, Lars
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Large area photodetectors based on InP NWs with InAs/InAsP QWs2014Conference paper (Refereed)
    Abstract [en]

    Focal plane arrays have a widespread use in infrared imaging, which often rely on cryogenic cooling to curtail the dark current level necessary for a reasonable signal-to-noise ratio. Quantum well (QW) infrared photodetectors are uniform over large areas, but suffer from a severe drawback related to the selection rules for intersubband absorption. An interesting alternative is self-assembled III-V nanowires offering a key advantage owing to the enhanced absorption by optical resonance effects and strain relaxation.We present electrical and optical results from large ensembles of n+-i-n+ InP NWs, axially grown on InP substrates with InAs/InAsP QWs embedded within the i-segment, designed for both interband and intersubband detection. The NWs are contacted in a vertical geometry using 50 nm SiO2 as the insulating layer and ITO as the top contact. We first investigate the crystal quality of the InAsP QWs grown in 180 nm diameter NWs, using PL, CL and TEM. To achieve more abrupt InAs/InAsP QWs, we grow 130 nm diameter NWs and deplete the In present in the Au catalysts. The effect of n-doping on the device performance is studied by fabricating two different NW geometries, with and without an n+-segment grown before the nominal i-segment in the NW. In addition, the position of the QWs within the i-segment is varied to further scrutinize effects related to doping and crystal structure. Finally, we report spectrally resolved photocurrent results from the QWs in the near-infrared region and discuss about the further developments needed for intersubband detection.

  • 43.
    Jain, Vishal
    et al.
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Heurlin, Magnus
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Nowzari, Ali
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Lindgren, David
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Borgström, Magnus T.
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Capasso, Federico
    School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA.
    Samuelson, Lars
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Pettersson, Håkan
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Large Area Photodetectors at 1.3/1.55 μm Based on InP/InAsP NWs2014Conference paper (Refereed)
    Abstract [en]

    Optical communication systems benefit a lot from APDs due to their increased photocurrent gain as compared to conventional photodetectors. An avalanche region in a high bandgap material is especially useful to avoid the tunneling leakage currents in smaller bandgap materials needed for absorption at 1.3/1.55 µm wavelengths. Self-assembled III-V semiconductor nanowires have a key advantage owing to the enhanced absorption due to optical resonance effects and the strain relaxation in NWs, thus facilitating monolithic integration of different heterostructures on cheaper substrates. Here, we present electrical and optical results from large ensembles of InP/InAsP NWs, axially grown on p+ InP substrates. The NW base consists of an InP p-n junction acting as the avalanche region followed by an InP/InAsP absorption region, and ending with a top InP n+-segment. The 130nm diameter NW arrays are contacted in a vertical geometry using SiO2 as the insulating layer and ITO as the top contact. The n-doping in the avalanche region is varied to study it’s influence on the avalanche mechanism. Also the bandgap in the absorption region is varied from pure InP to smaller bandgap InAsP by varying the As content. Clear interband signals from different crystal phases of InP/InAsP are observed in photocurrent spectroscopy. Moreover, the photocurrent spectra are consistent with spatially resolved photoluminescence signals. We also report on polarization and angle dependent photocurrent response of the NW array.

  • 44.
    Jain, Vishal
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Nowzari, Ali
    Lund University, Lund, Sweden.
    Wallentin, Jesper
    Lund University, Lund, Sweden.
    Borgström, Magnus T.
    Lund University, Lund, Sweden.
    Messing, Maria E.
    Lund University, Lund, Sweden.
    Asoli, Damir
    Ideon Science Park, Sol Voltaics AB, Lund, Sweden.
    Graczyk, Mariusz
    Lund University, Lund, Sweden.
    Witzigmann, Bernd
    University of Kassel, Kassel, Germany .
    Capasso, Federico
    Harvard University, Cambridge, Massachusetts, USA.
    Samuelson, Lars
    Lund University, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Study of photocurrent generation in InP nanowire-based p+–i–n+ photodetectors2014In: Nano Reseach, ISSN 1998-0124, E-ISSN 1998-0000, Vol. 7, no 4, p. 544-552Article in journal (Refereed)
    Abstract [en]

    We report on electrical and optical properties of p+-i-n+ photodetectors/solar cells based on square millimeter arrays of InP nanowires grown on InP substrates. The study includes a sample series where the p+-segment length was varied between 0 and 250nm, as well as solar cells with 9.3% efficiency with similar design. The electrical data for all devices display clear rectifying behavior with an ideality factor between 1.8 and 2.5 at 300K. From spectrally resolved photocurrent measurements, we conclude that the photocurrent generation process depends strongly on the p+-segment length. Without p+-segment, photogenerated carriers funneled from the substrate into the NWs contribute strongly to the photocurrent. Adding a p+-segment decouples the substrate and shifts the depletion region, and collection of photogenerated carriers, to the nanowires, in agreement with theoretical modeling. In optimized solar cells, clear spectral signatures of interband transitions in the ZB and WZ InP layers of the mixed-phase i-segments are observed. Complementary electroluminescence, TEM as well as measurements of the dependence of the photocurrent on angle of incidence and polarization, support our interpretations. © 2014 Tsinghua University Press and Springer-Verlag Berlin Heidelberg.

  • 45.
    Jain, Vishal
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Wallentin, Jesper
    Physics Department, Lund University, Lund, Sweden.
    Borgström, Magnus
    Physics department, Lund university, Lund, Sweden.
    Storm, Kristian
    Physics Department, Lund University, Lund, Sweden.
    Landin, Lars
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Wickert, Peter
    Sol Voltaics AB, Lund, Sweden.
    Capasso, Federico
    Harvard University, Cambridge, Massachusetts, USA.
    Samuelson, Lars
    Physics Department, Lund university, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    A comparative study of nanowire based infrared p+-i-n+ photodetectors2012Conference paper (Refereed)
    Abstract [en]

    We present a comparative study of electrical and optical properties of two types of p+-i-n+ photodetectors based on self-assembled ensembles of vertical InP nanowires (NWs) monolithically grown on InP. The detectors differ in the type of p+ contact, one detector geometry has p+-i-n+ segments integrated into the NWs (type A) while the other detector has i-n+ NW segments grown directly on a p+ substrate(type B). The samples were prepared by first depositing 80 nm Au nanoparticles on a p+ InP substrate using an aerosol technique and subsequently growing NWs using MOVPE. The NWs have a polytypecrystal structure of alternating wurtzite and zincblende segments. The processing of the detectors include deposition of SiO2, followed by an etching step to remove the oxide from the tip of the NWs, and finally sputtering of ITO on 1x1 mm2 device areas. The two most prominent differences between the detectors concern the current-voltage (I-V) characteristics and the spatial location of generated photocurrent. From spectrally resolved photocurrent measurements, we conclude that the photocurrent in detector type A is primarily generated in the NWs, whereas the photocurrent in type B detectors mainly stems from the substrate. Photogenerated carriers in the substrate diffuse to the NWs where they are effectively funnelled into the NWs. The I-V characteristics of the type A detector displays a non-trivial transport behaviour for forward biases, whereas type B shows excellent rectifying behavior with an ideality factor of about 2.5. We will discuss detailed analysis of the spectral fingerprints of the two detector types revealing the mixed crystal phase of the polytype NWs and bandstructure effects, temperature dependence of the I-V characteristics and typical photodetector parameters.

  • 46.
    Jain, Vishal
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Wallentin, Jesper
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Nowzari, Ali
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Heurlin, Magnus
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Asoli, Damir
    Sol Voltaics AB, Lund, Sweden.
    Borgström, Magnus T.
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Capasso, Federico
    School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA.
    Samuelson, Lars
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Processing and Characterization of Nanowire Arrays for Photodetectors2015In: Nano-Structures for Optics and Photonics: Optical Strategies for Enhancing Sensing, Imaging, Communication and Energy Conversion / [ed] Baldassare Di Bartolo, John Collins & Luciano Silvestri, Dordrecht: Springer, 2015, p. 511-512Conference paper (Refereed)
    Abstract [en]

    We present a fabrication scheme of contacting arrays of vertically standing nanowires (NW) for LEDs (Duan et al. Nature 409:66–69, 2001), photodetectors (Wang et al. Science (NY) 293:1455–1457, 2001) or solar cell applications (Wallentin et al. Science (NY) 339:1057–1060, 2013). Samples were prepared by depositing Au films using nano-imprint lithography (Må rtensson et al. Nano Lett 4:699–702, 2004) which are used as catalysts for NW growth in a low-pressure metal organic vapour phase epitaxy system where III-V precursors and dopant gases are flown at elevated temperatures which lead to the formation of NWs with different segments (Borgström et al. Nano Res 3:264–270, 2010). An insulating SiO2 layer is then deposited and etched from the top segments of the NWs followed by sputtering of a transparent top conducting oxide and opening up 1 × 1 mm2 device areas through a UV lithography step and etching of the top contact from non-device areas. A second UV lithography step was subsequently carried out to open up smaller windows on the ITO squares for bond pad definition, followed by metallization and lift-off; and the substrate is used as back contact. We also report on the electrical and optical properties of near-infrared p+−i−n+ photodetectors/solar cells based on square millimeter ensembles of InP nanowires grown on InP substrates. The study includes a sample series where the p +-segment length was varied between 0 and 250 nm, as well as solar cell samples with 9.3 % efficiency with similar design. The NWs have a complex modulated crystal structure of alternating wurtzite and zincblende segments, a polytypism that depends on dopant type. The electrical data for all samples display excellent rectifying behavior with an ideality factor of about 2 at 300 K. From spectrally resolved photocurrent measurements, we conclude that the photocurrent generation process depends strongly on the p +-segment length. Without p +-segment in the NWs, photogenerated carriers funneled from the substrate into the NWs contribute significantly to the photocurrent. Adding a p +-segment shifts the depletion region up into the i-region of the NWs reducing the substrate contribution to photocurrent while strongly improving the collections of carriers generated in the NWs, in agreement with theoretical modeling (Fig. 48.1). © Springer Science+Business Media Dordrecht 2015.

  • 47.
    Jam, R. Jafari
    et al.
    Division of Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Beech, Jason P.
    Division of Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Zeng, Xulu
    Division of Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Johansson, Jonas
    Division of Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Samuelson, Lars
    Division of Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Division of Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Borgström, Magnus T.
    Division of Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Embedded sacrificial AlAs segments in GaAs nanowires for substrate reuse2020In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 31, no 20, article id 204002Article in journal (Refereed)
    Abstract [en]

    We report on the use of a sacrificial AlAs segment to enable substrate reuse for nanowire synthesis. A silicon nitride template was deposited on a p-type GaAs substrate. Then a pattern was transferred to the substrate by nanoimprint lithography and reactive ion etching. Thermal evaporation was used to define Au seed particles. Metalorganic vapour phase epitaxy was used to grow AlAs-GaAs NWs in the vapour-liquid-solid growth mode. The yield of synthesised nanowires, compared to the number expected from the patterned template, was more than 80%. After growth, the nanowires were embedded in a polymer and mechanically removed from the parent substrate. The parent substrate was then immersed in an HCl:H2O (1:1) mixture to dissolve the remaining stub of the sacrificial AlAs segment. The pattern fidelity was preserved after peeling off the nanowires and cleaning, and the semiconductor surface was flat and ready for reuse. Au seed particles were then deposited on the substrate by use of pulse electrodeposition, which was selective to the openings in the growth template, and then nanowires were regrown. The yield of regrowth was less optimal compared to the first growth but the pattern was preserved. Our results show a promising approach to reduce the final cost of III-V nanowire based solar cells. © 2020 The Author(s). Published by IOP Publishing Ltd.

  • 48.
    Jam, Reza Jafari
    et al.
    Lund Univ, Div Solid State Phys & NanoLund, Box 118, SE-21100 Lund, Sweden..
    Persson, Axel R.
    Lund Univ, Centr & Anal & Synth & NanoLund, POB 124, SE-21100 Lund, Sweden..
    Barrigon, Enrique
    Lund Univ, Div Solid State Phys & NanoLund, Box 118, SE-21100 Lund, Sweden..
    Heurlin, Magnus
    Lund Univ, Div Solid State Phys & NanoLund, Box 118, SE-21100 Lund, Sweden..
    Geijselaers, Irene
    Lund Univ, Div Solid State Phys & NanoLund, Box 118, SE-21100 Lund, Sweden..
    Gomez, Victor J.
    Lund Univ, Div Solid State Phys & NanoLund, Box 118, SE-21100 Lund, Sweden..
    Hultin, Olof
    RISE Res Inst Sweden, Scheelevagen 17, S-22370 Lund, Sweden..
    Samuelson, Lars
    Lund Univ, Div Solid State Phys & NanoLund, Box 118, SE-21100 Lund, Sweden..
    Borgstrom, Magnus T.
    Lund Univ, Div Solid State Phys & NanoLund, Box 118, SE-21100 Lund, Sweden..
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Lund Univ, Div Solid State Phys & NanoLund, Box 118, SE-21100 Lund, Sweden.;Halmstad Univ, Sch Informat Technol, Box 823, S-30118 Halmstad, Sweden..
    Template-assisted vapour-liquid-solid growth of InP nanowires on (001) InP and Si substrates2020In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 12, no 2, p. 888-894Article in journal (Refereed)
    Abstract [en]

    We report on the synthesis of vertical InP nanowire arrays on (001) InP and Si substrates using template-assisted vapour-liquid-solid growth. A thick silicon oxide layer was first deposited on the substrates. The samples were then patterned by electron beam lithography and deep dry etching through the oxide layer down to the substrate surface. Gold seed particles were subsequently deposited in the holes of the pattern by the use of pulse electrodeposition. The subsequent growth of nanowires by the vapour-liquid-solid method was guided towards the [001] direction by the patterned oxide template, and displayed a high growth yield with respect to the array of holes in the template. In order to confirm the versatility and robustness of the process, we have also demonstrated guided growth of InP nanowire p-n junctions and InP/InAs/InP nanowire heterostructures on (001) InP substrates. Our results show a promising route to monolithically integrate III-V nanowire heterostructure devices with commercially viable (001) silicon platforms.

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  • 49.
    Jeddi Abdarloo, Hossein
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Lund University, Lund, Sweden.
    Karimi, Mohammad
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Lund University, Lund, Sweden.
    Witzigmann, Bernd
    University of Kassel, Kassel, Germany.
    Zeng, Xulu
    Lund University, Lund, Sweden.
    Hrachowina, Lukas
    Lund University, Lund, Sweden.
    Borgström, Magnus T.
    Lund University, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Lund University, Lund, Sweden.
    Gain and bandwidth of InP nanowire array photodetectors with embedded photogated InAsP quantum discs2021In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 13, no 12, p. 6227-6233Article in journal (Refereed)
    Abstract [en]

    Here we report on the experimental results and advanced self-consistent real device simulations revealing a fundamental insight into the non-linear optical response of n+-i-n+ InP nanowire array photoconductors to selective 980 nm excitation of 20 axially embedded InAsP quantum discs in each nanowire. The optical characteristics are interpreted in terms of a photogating mechanism that results from an electrostatic feedback from trapped charge on the electronic band structure of the nanowires, similar to the gate action in a field-effect transistor. From detailed analyses of the complex charge carrier dynamics in dark and under illumination was concluded that electrons are trapped in two acceptor states, located at 140 and 190 meV below the conduction band edge, at the interface between the nanowires and a radial insulating SiOx cap layer. The non-linear optical response was investigated at length by photocurrent measurements recorded over a wide power range. From these measurements were extracted responsivities of 250 A W-1 (gain 320)@20 nW and 0.20 A W-1 (gain 0.2)@20 mW with a detector bias of 3.5 V, in excellent agreement with the proposed two-trap model. Finally, a small signal optical AC analysis was made both experimentally and theoretically to investigate the influence of the interface traps on the detector bandwidth. While the traps limit the cut-off frequency to around 10 kHz, the maximum operating frequency of the detectors stretches into the MHz region. © The Royal Society of Chemistry

  • 50.
    Jeddi Abdarloo, Hossein
    et al.
    Halmstad University, School of Information Technology. Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Witzigmann, Bernd
    Institute for Optoelectronics, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany.
    Adham, Kristi
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Hrachowina, Lukas
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Borgström, Magnus T.
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology. Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Spectrally Tunable Broadband Gate-All-Around InAsP/InP Quantum Discs-in-Nanowire Array Phototransistors with a High Gain-Bandwidth Product2023In: ACS Photonics, E-ISSN 2330-4022, Vol. 10, no 6, p. 1748-1755Article in journal (Refereed)
    Abstract [en]

    High-performance broadband photodetectors offering spectral tunability and a high gain-bandwidth product are crucial in many applications. Here, we report on a detailed experimental and theoretical study of three-terminal phototransistors comprised of three million InP nanowires with 20 embedded InAsP quantum discs in each nanowire. A global, transparent ITO gate all around the nanowires facilitates a radial control of the carrier concentration by more than two orders of magnitude. The transfer characteristics reveal two different transport regimes. In the subthreshold region, the photodetector operates in a diffusion mode with a distinct onset at the bandgap of InP. At larger gate biases, the phototransistor switches to a drift mode with a strong contribution from the InAsP quantum discs. Besides an unexpected spectral tunability, the detector exhibits a state-of-the-art responsivity, reaching around 100 A/W (638 nm/20 μW) @ VGS = 1.0 V/VDS = 0.5 V with a gain-bandwidth product of around 1 MHz, in excellent agreement with a comprehensive real-device model. © 2023 The Authors. Published by American Chemical Society.

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