EFFECT OF IN SEGREGATION ON THE STRUCTURAL AND OPTICAL-PROPERTIES OF ULTRATHIN INAS FILMS IN GAAS

We study the segregation of In during the overgrowth of an InAs monolayer (ML) with GaAs by molecular beam epitaxy. The presence of segregating In adatoms (In floating layer) at the growth surface is observed in situ by reflection high-energy electron diffraction. We demonstrate (i) that the segregation process causes a spatial spread-out of 0.4 ML of In into the first 4-5 ML of the GaAs overlayer and (ii) that this spread-out can be inhibited by the thermal desorption of the In floating layer in the initial stage of overgrowth (flash-off). The flash-off approach creates in fact a single InAs ML in the GaAs matrix.