Two-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. We have found that the inhomogeneous broadening of the PL from InAs layers can be well described by the quantum-well model with InAs islands coupling to each other and being regarded as a quasiwell. From the temperature dependence of the exciton linewidth, the exciton–LO-phonon scattering coefficient was found to be comparable to that in conventional two-dimensional quantum wells. In the TRPL measurements, the PL decay time increases linearly with temperature, which is a typical characteristic 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. @S0163-1829~96!01647-5#