CAPTURE TIME VERSUS BARRIER THICKNESS IN QUANTUM-WELL STRUCTURES MEASURED BY INFRARED PHOTOCONDUCTIVE GAIN

Photoconductive gain measurements in quantum-well (QW) infrared detectors are used to determine the variation of the capture time of electrons in QWs as a function of barrier thickness. The capture time is shown to be proportional to the multi-quantum-well period, which is consistent with a quantum mechanical description of the capture process. The measured values are far higher than the ones measured by time-resolved photoluminescence, ranging from 8 to 150 ps, depending on the applied electric field and barrier thickness. The reasons for this discrepancy are discussed.