TIME-RESOLVED EXCITON DYNAMICS AND STIMULATED-EMISSION FROM ZNCDSE ZNSE MULTIPLE-QUANTUM-WELL STRUCTURES/

Time-resolved luminescence has been used to investigate the dynamics o f excitonic recombination and stimulated emission in ZnCdSe/ZnSe multi ple quantum wells where the exciton binding energy is close to the opt ical phonon energy. At low excitation densities strong excitonic recom bination is observed with simple exponential decay kinetics. At densit ies near threshold, however, bilinear recombination kinetics are found with a large rate constant (R = 1.8 x 10(-3) s(-1) cm(2)), and a dram atic reduction in the lifetime is observed. Stimulated emission occurs at an energy similar to 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 r ecombination in a dense exciton system, which gives way at high densit y to a correlated electron-hole plasma.