RADIATIVE RECOMBINATION IN GAAS ALXGA1-XAS QUANTUM-WELLS/

An experimental study at room temperature of the rate of radiative rec ombination in a range of p-type GaAs/Al0.33Ga0.67As quantum-well sampl es using both transient photoluminescence (PL) and photoconductivity ( PC) techniques is reported. The PL measurements provided the small-sig nal time constant and the PC measurements probed the nonlinear excitat ion regime, providing quantitative evidence of excitonic involvement a t hole densities less than about 3 x 10(11) cm-2. The intensity depend ence of the PC gave the variation of effective mobility with excitatio n density. This mobility variation was used to successfully relate the PL and PC time constants. These time constants, corrected for photon recycling, had the same values as bulk material over a volume-hole-den sity range 8 x 10(16) to 3 x 10(18) cm-3, described by a recombination coefficient B = 1.8 x 10(-10) cm3 s-1. A comparison with a theoretica l model, which included excitonic effects, photon recycling, and reduc ed electron-hole overlap in the well, highlighted the importance of th e magnitude of the effective density-of-states mass in the valence sub bands. Experimental evidence suggests that the latter is 0.32 m, which is over twice the value of the heavy-hole mass at the band edge. For degenerate excited populations the time constant, corrected for photon recycling, was found to be 0.8 ns, which is in reasonable agreement w ith the theoretical prediction of 0.7 ns.