Local responsivity in quantum well infrared photodetectors

This article presents a theoretical and computational study of physical effects in quantum well infrared photodetectors (QWIPs) under localized excitation. The steady-state photoresponse involves the formation of the dipole layer near the photoexcited QW. The nonequilibrium (fast transient) responsivity is associated with the photoexcitation and sweep out of carriers from the QW region. Both steady-state and nonequilibrium local responsivities depend on coordinate across the QWIP, and decrease from emitter to collector. The nonequilibrium responsivity decreases to zero over a distance equal to the drift length near the collector. The proposed analytical models of the steady-state and nonequilibrium responsivities are in excellent agreement with the results of numerical simulation. (C) 1999 American Institute of Physics. [S0021-8979(99)04923-3].