THE EFFECT OF STIMULATED-EMISSION ON THE COOLING RATE OF HOT CARRIERS IN GAAS

The effect of a short carrier lifetime due to stimulated emission on the cooling rate of nearly resonantly excited carriers in bulk GaAs has been investigated using picosecond time-resolved photoluminescence. It has been found that intense photoexcitation of carriers results in very short carrier density decay times of about 20 ps, as opposed to common carrier lifetimes of about 1 ns observed for low excitation levels. Furthermore a considerable reduction of the cooling rate has been found. The rapid density decay and the significant cooling reduction can be well described by an energy relaxation model, only when stimulated recombination is taken into account in addition to the usual carrier-phonon interactions. Within this model the short carrier lifetime considerably reduces the carrier cooling in nice agreement with the experimental results.