Observation of picosecond carrier lifetimes in GaAs/AlGaAs single quantum wells grown at 630 °C

We report short carrier lifetimes for GaAs/AlGaAs isolated single quantum wells (35, 50, and 90 Å) grown via molecular beam epitaxy at 630 °C. Photoluminescence (PL) measured at 14–150 K show defect transitions that significantly thermalize at ~77 K. Carrier lifetimes of the quantum wells, measured via time-resolved PL (TRPL), are ~21 ps (35 Å), ~39 ps (50 Å) and ~48 ps (90 Å). Carrier lifetimes and fluence-dependence measurements suggest that at 77 K where the shallow levels have thermalized, deeper level defects are still present and act as effective carrier traps. The defect density appears to vary inversely with well-width, and this observed behavior is explained on the basis of interface roughness.