ORIGIN OF SHARP LINES IN PHOTOLUMINESCENCE EMISSION FROM SUBMONOLAYERS OF INAS IN GAAS

Very sharp and intense low-temperature photoluminescence (PL) emission is reported from submonolayers of InAs in GaAs grown by flow modulati on epitaxy at 50 Torr using trimethylindium and tertiarybutylarsine. I nAs coverages from 0.25 to 1.0 monolayers were systematically studied using low temperature FL, and photoluminescence excitation spectroscop y and temperature-dependent, time-resolved FL. The observed PL linewid ths and energies are satisfactorily explained within a two-dimensional (2D) quantum well picture over all coverages. In these ultrathin stru ctures we see confirmation of existing models which predict a smooth t ransition of the PL linewidth to zero in the limit of extremely thin w ells. The possibility of weak OD localization of excitons by thickness variations in the submonolayer samples is discussed.