IMPACT OF TRANSIT-TIME AND CAPTURE EFFECTS ON HIGH-FREQUENCY PERFORMANCE OF MULTIPLE-QUANTUM-WELL INFRARED PHOTODETECTORS

An analytical model of multiple quantum-well photodetectors (QWIP's) i s proposed and used to evaluate their high-frequency performance, The model accounts for the electron photoexcitation from the QW's, capture into them and drift of the photoexcited electrons across the barriers , The frequency-dependent responsivity and the gain-bandwidth efficien cy are derived as functions of the QWIP parameters, It is shown that t he responsivity roll-off and 3 dB bandwidth are determined by the elec tron transit-time and capture effects, so that the main factors limiti ng the QWIP high-frequency performance are the number of the QW's and the rate of the electron capture into them, It is predicted that the g ain-bandwidth efficiency weakly depends on the number of the QW's and capture parameter.