Monte Carlo modeling of electron velocity overshoot effect in quantum well infrared photodetectors

Transient response of n-type AlGaAs/GaAs and InP/InGaAs quantum well infrared photodetectors (QWIPs) has been studied using an ensemble Monte Carlo particle method. It has been shown that the photocurrent initiated by an ultrashort pulse of infrared radiation reveals a sharp peak associated with the electron velocity overshoot effect. The existence of the photocurrent peak results in a plateaulike region in the QWIP frequency-dependent responsivity in the terahertz range. This effect can be used for heterodyne detection in QWIP-based mixers at terahertz frequencies and for generation of terahertz radiation. Larger intervalley separation and, consequently, more pronounced electron velocity overshoot in InP-based QWIPs in comparison with QWIPs with AlGaAs barriers lead to higher performance of the former in the terahertz range of spectrum. (C) 1998 American Institute of Physics.