Quantum dots (QDs)-embedded photodiodes have demonstrated great potential on detectors. A modulation of QD charging opens intriguing possibilities for adaptive sensing with bias-tunable detector characteristics. Here, we report on a p-i-n GaAs photodiode with InAs QDs whose charging is tunable due to unintentional Be diffusion and trap-assisted tunneling of holes, from bias- and temperature (T)-dependent photocurrent spectroscopy. For the sub-bandgap spectra, the T-dependent relative intensities "QD-s/WL" and "WL/GaAs" (WL: wetting layer) reflect a dominant tunneling under -0.9 V (trap-assisted tunneling from the top QDs) and a dominant thermal escape under -0.2 ~ 0.5 V (from the bottom QDs since the top ones are charged and inactive for optical absorption) from QD s-state, a dominant tunneling from WL and an enhanced QD charging at > 190 K (related to trap level ionization). For the above-bandgap spectra, the degradation of the spectral profile (especially that near GaAs bandedge) as the bias and T tune (especially under -0.2 ~ 0.2 V and at > 190 K) can be well explained by the enhanced photoelectron capture in QDs with tunable charging; the dominant spectral profile with no degradation under 0.5 V is due to a saturated electron capture in charged QDs (i.e. charging neutralization). QD level simulation and schematic bandstructures help to understand these effects. © 2015 AIP Publishing LLC