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

Abstract

We analyze the extended threshold wavelength photoresponse beyond the standard threshold limit ( ${\lambda _t} = 1.24/\Delta $ , where $\Delta $ is the activation energy) in nonsymmetrical p-GaAs/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 ( $E_{{\rm{quasiF}}}$ ). The simulated results are found to be in good agreement with experimental data, justifying the model used.