ELECTRON-CAPTURE TIME MEASUREMENTS IN GAAS/ALGAAS QUANTUM-WELL INFRARED PHOTODETECTORS - PHOTORESPONSE SATURATION BY A FREE-ELECTRON LASER

The intersubband photoresponse in GaAs/AlGaAs quantum-well detectors has been measured with a free-electron laser delivering picosecond pulses. The saturation of the detector photocurrent with increasing power was observed. A model is presented that takes the absorption saturation and transport properties into account and allows the electron lifetime determination from the photocurrent saturation. The electron lifetime is found to increase with the electric field applied in the detector from 1 ps at low field up to 10 ps or more at high field (15 kV/cm). Effects of doping and well asymmetry are discussed. © 1995 American Institute of Physics.