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Comparative study of infrared photodetectors based on quantum wells (QWIPs) and quantum dots (QDIPs)
Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE).
Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE).
2006 (English)Independent thesis Advanced level (degree of Master (One Year))Student thesis
Abstract [en]

This master’s thesis deals with studies of lateral and vertical carrier transport Dot-in-

a-Well (DWELL) Quantum Dot Infrared Photodetectors (QDIPs). During the pro ject,

devices have been developed and tested using a Fourier Transform Infrared (FTIR) spec-

trometer with the purpose to find the processes governing the flow of photocurrent in

the different kinds of detectors, the dark current magnitude in the vertical Quantum Dot

Infrared Photodetector (QDIP) and the Quantum Well Infrared Photodetector (QWIP)

and the light polarization dependences for the vertical QDIP and the QWIP.

The lateral carrier transport DWELL QDIP was found to have poor conduction

in the well mainly due to re-trapping of electrons in this region. The main process gov-

erning the flow of photocurrent for this type of device at 77K is photo-excitation from

the Quantum Dot (QD)s to the excited state in the Quantum Well (QW) and further

thermal excitation. If the electrons are mainly transported in the matrix or the well at

77K is presently not clear.

For the vertical carrier transport DWELL QDIP at 77K, the wavelength response

could be tuned by altering the applied voltage. At higher voltages, the dominant process

was found to be photo-excitation from the QDs to the excited state in the QW followed

by thermal assisted tunneling into the GaAs-matrix. At lower voltages, photo-excitation

from the QDs directly into the the GaAs-matrix was the predominant process. The dark

current level in the vertical QDIPs was found to be 1.5 to 5 orders of magnitude smaller

than for the QWIP measured at 77K. Furthermore, the QDIP was found to be close to

polarization independent. As expected the QWIP had a reduced sensitivity to normal

incident light. The existence of this signal was attributed to interface scattering of light

inside the device.

Place, publisher, year, edition, pages
Högskolan i Halmstad/Sektionen för Informationsvetenskap, Data- och Elektroteknik (IDE) , 2006. , p. 1231508 bytes
Keywords [en]
Dot-in-a-Well, DWELL, Quantum Dot Infrared Photodetectors, QDIPs, Lateral carrier transport
Identifiers
URN: urn:nbn:se:hh:diva-234Local ID: 2082/529OAI: oai:DiVA.org:hh-234DiVA, id: diva2:237412
Uppsok
Technology
Available from: 2006-11-24 Created: 2006-11-24 Last updated: 2007-01-08

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