ULTRAFAST INTERSUBBAND PHOTOCURRENT RESPONSE IN QUANTUM-WELL INFRAREDPHOTODETECTORS

We report on a high bandwidth measurement of the transient intersubban d photocurrent of a GaAs/AlGaAs multiple quantum-well infrared photode tector (QWIP). The photocurrent is excited via tunable subpicosecond i nfrared pulses. The response time of the detector has a full width at half-maximum of 18.5 ps and a rise time of 14.5 ps, which is limited b y the electrical circuit. The decay time of the photocurrent response exhibits a significant dependence on the applied voltage, with increas ing decay times for increasing bias voltages. From the experimental da ta, we conclude that the intrinsic response time of a QWIP is less tha n 7 ps. (C) 1997 American Institute of Physics.