Analysis of Extended Threshold Wavelength Photoresponse in Nonsymmetrical p-GaAs/AlGaAs Heterostructure Photodetectors

We analyze the extended threshold wavelength photoresponse beyond the standard threshold limit (λ
_t
= 1.24/Δ, where Δ is the activation energy) in nonsymmetrical pGaAs/AlGaAs heterostructure photodetectors with a barrier energy offset. We propose that hot-cold hole carrier interactions in the p-GaAs absorber are responsible for the threshold wavelength extension. Experimental results are analyzed by considering a quasi-Fermi distribution of hot holes at a hot hole temperature (T
_H
), which is much higher than the lattice temperature (T
_L
). The experimental photoresponse is fitted using an escape cone model, modified with a quasi-Fermi level (E
_quasiF
). The simulated results are found to be in good agreement with experimental data, justifying the model used.