Time-resolved exciton dynamics and stimulated emission from [formula omitted] multiple quantum well structures

Abstract

Time-resolved luminescence has been used to investigate the dynamics of excitonic recombination and stimulated emission in ZnCdSe ZnSe multiple quantum wells where the exciton binding energy is close to the optical phonon energy. At low excitation densities strong excitonic recombination is observed with simple exponential decay kinetics. At densities near threshold, however, bilinear recombination kinetics are found with a large rate constant ( R = 1.8 × 10 −3 s −1 cm 2), and a dramatic reduction in the lifetime is observed. Stimulated emission occurs at an energy ∼ 18 meV below the exciton absorption peak, and shifts to lower energy with increasing excitation density up to three times the threshold density. These observations are consistent with recombination in a dense exciton system, which gives way at high density to a correlated electron-hole plasma.