ELECTRON MOBILITIES AND PHOTOELECTRON LIFETIMES IN ALGAAS GAAS AND INGAAS GAAS QUANTUM-WELL INFRARED DETECTORS

Gain and geometric magnetoresistance electron mobility measurements ar e presented for quantum-well infrared photoconductors. The electron mo bility is found to be identical for both the photocurrent and the dark current and has a value of 2.6 X 10(3) CM2 V-1 s-1 in devices made fr om GaAs/AlxGa1-xAs and 9.4 X 10(3) cM2 V-1 S-1 in the InxGa1-xAs/GaAs devices at 77 K. This difference in mobility is associated with the pu rity of the barrier material which is much greater in GaAs than in Alx Ga1-As. The photoelectron lifetime before recapture can be deduced fro m the combination of the gain and mobility measurements. This lifetime is found to be 7.2 ps in the AlxGa1-xAs/GaAs detectors and 5.5 ps in the InxGa1-xAs/GaAs devices.