Transient photoconductivity in quantum well infrared photodetectors

Transient photoconductivity in quantum well infrared photodetectors (QWIPs) is studied using numerical modeling. Transient photocurrent in QWIPs illuminated by steplike infrared radiation consists of two components. A fast component, representing the primary photocurrent, is determined by the processes of the carrier capture to the QWs and transit through the QW structure. Its amplitude can be lower than the steady-state photocurrent due to the sweep-out of the photoexcited carriers. A slow component, comprising the multiplied photocurrent, is governed by the recharging of the QWs. The QWIPs can exhibit high photocurrent gain only at frequencies of harmonic infrared radiation lower than the inverse characteristic time of establishing equilibrium at the injecting contact. (C) 1996 American Institute of Physics.