PHOTOLUMINESCENCE STUDIES OF CURRENT-INDUCED NONEQUILIBRIUM STATES INMAGNETICALLY QUANTIZED 2-DIMENSIONAL ELECTRON GASES

We report studies by optical techniques of current-induced nonequilibr ium electron populations in magnetically quantized two-dimensional ele ctron gases. Increasingly marked current-dependent changes with magnet ic field are observed in both the energy and the intensity of the main photoluminescence features. The magnetic-field dependence of the rela xation time of nonequilibrium population following a current pulse is qualitatively in line with the severe momentum constraints on one-phon on emission. However, a theoretical treatment of this mechanism shows stronger field dependence, proportional to B-4, than that found experi mentally proportional to B-2, indicating the importance of parallel re laxation channels. We suggest these may involve the diffusion of excit ed electrons via intra-Landau-level transitions to centers in the Hall bar where relaxation can occur via inter edge-state transitions.