2-DIMENSIONAL EXCITONIC EMISSION IN INAS SUBMONOLAYERS

Photoluminescence (PL) and time-resolved photoluminescence (TRPL) were used to study optical emissions of ultrathin InAs layers with average layer thickness ranging from 1/12 to 1 ML grown on GaAs substrates. W e have found that the inhomogeneous broadening of the PL from InAs lay ers can be well described by the quantum-well model with InAs islands coupling to each other and being regarded as a quasiwell. From the tem perature dependence of the exciton linewidth, the exciton-LO-phonon sc attering coefficient was found to be comparable to that in conventiona l two-dimensional quantum wells. In the TRPL measurements, the PL deca y time increases linearly with temperature, which is a typical charact eristic of free excitons in quantum wells. All these results indicate that the excitons localized in InAs exhibit two-dimensional properties of quantum wells, despite the topographical islandlike structure.