Electron mobilities and photoelectron lifetimes in AlGaAs/GaAs and InGaAs/GaAs quantum-well infrared detectors

Gain and geometric magnetoresistance electron mobility measurements are presented for quantum-well infrared photoconductors. The electron mobility is found to be identical for both the photocurrent and the dark current and has a value of 2.6×103 cm2 V−1 s−1 in devices made from GaAs/AlxGa1−xAs and 9.4×103 cm2 V−1 s−1 in the InxGa1−xAs/GaAs devices at 77 K. This difference in mobility is associated with the purity of the barrier material which is much greater in GaAs than in AlxGa1−xAs. The photoelectron lifetime before recapture can be deduced from 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.