Influence of electron velocity overshoot effect on high-frequency characteristics of quantum well infrared photodetectors

We have studied the transient response of AlxGa1-xAs/GaAs quantum well infrared photodetectors (QWIPs) and their high-frequency performance using a self-consistent ensemble Monte Carlo particle method. It has been shown that the photocurrent caused by the electron intersubband transitions under the influence of an ultra-short pulse of infrared radiation reveals a sharp peak followed by relatively slow decay. This is associated with the electron velocity overshoot and the electron transit time and capture effects. The velocity overshoot results in the existence of an additional plateau-like region in the QWIP frequency-dependent responsivity which can correspond to the terahertz range.