Origin of sharp lines in photoluminescence emission from submonolayers of InAs in GaAs

Abstract

Very sharp and intense low-temperature photoluminescence (PL) emission is reported from submonolayers of InAs in GaAs grown by flow modulation epitaxy at 50 Torr using trimethylindium and tertiarybutylarsine. InAs coverages from 0.25 to 1.0 monolayers were systematically studied using low temperature PL, and photoluminescence excitation spectroscopy and temperature-dependent, time-resolved PL. The observed PL linewidths and energies are satisfactorily explained within a two-dimensional (2D) quantum well picture over all coverages. In these ultrathin structures we see confirmation of existing models which predict a smooth transition of the PL linewidth to zero in the limit of extremely thin wells. The possibility of weak 0D localization of excitons by thickness variations in the submonolayer samples is discussed.