Ultrafast Dynamics of Electronic Capture and Intersubband Relaxation in GaAs Quantum Well

Abstract

The dynamics of carrier capture and intersubband relaxation in GaAs quantum well have been measured, using a time-resolved photoluminescence technique. At low carrier densities (≤ 2×1010 cm -2), electron capture times are shown to oscillate as a function of well width and a quantum-mechanical resonance is observed when one confined level is 36 meV below the barrier edge. Holes capture times are fast (< 10 ps), and depend weakly on the structure. No significant changes of the carrier capture times are observed for carrier densities up to 1×1011 cm-2. For well widths < 150 A, a fast intersubband (2→ 1) relaxation time (of typically 3 ps) is measured. This relaxation time is shown to increase by an order of magnitude at longer well width (220 A). The observed variation of both the electron capture times and the intersubband relaxation times with well width, demonstrate the importance of LO phonon quantum-mechanical scattering processes.