Nonresonant electron capture in GaAs/AlAs/AlGaAs double-barrier quantum well infrared detectors.

We have investigated electron and hole capture times in n-type double-barrier quantum well (DBQW) infrared (3-5 mym) detector structures. Photoluminescence upconversion allows us to observe the relaxation of photoexcited carriers from AlAs/(AlGa)As/AlAs barriers into GaAs quantum wells. For 2 nm AlAs, 25 nm Alsub0.3Gasub0.7As and 5 nm GaAs, the electron capture process is non-resonant, with a capture time of 47 ps at the temperature of 5 K and 28 ps at 77 K. Theoretical calculations show that electron tunneling across the 2 nm AlAs layers mainly occurs via the Gamma-minimum, and that the Gamma-X contributin is negligible.