Theoretical analysis of the response time of MWIR InAs/InAsSb T2SL barrier detector

The InAs/InAsSb type-II superlattice (T2SL) detector with wide-gap AlGaAsSb electron barrier was made and analyzed. The epitaxial layer with a design of n+nBnN+ was deposited on a GaAs (1 0 0) substrate using the molecular beam epitaxy. The detector's spectral response and current–voltage characteristics were measured at temperatures of 230 K and 300 K. Experimental data were compared with numerical simulations carried out using the commercial APSYS program. The good fit has provided output parameters for further simulations carried out to optimize the structure for response time. Then, the influence of the bias voltage and the thickness and doping level of the absorber on the detector time constant was examined. The optimal structure allows to obtain a time constant of about 47 ns at 300 K and 27 ns at 230 K in the voltage range where the dark current is saturated and limited by the diffusion mechanism. The critical condition for achieving a short detector time constant is a zero offset in the valence band.