STRUCTURAL AND OPTICAL CHARACTERIZATION OF INP GAINP ISLANDS GROWN BYSOLID-SOURCE MBE/

We report on the growth of InP/GaInP islands on GaAs substrates by sol id-source molecular beam epitaxy. It is shown by reflection high energ y electron diffraction and atomic force microscopy that a rapid change from a two-dimensional to a three-dimensional growth mode occurs at a bout nominally 1.5 monolayers (MLs) InP. Transmission electron microsc opy measurements demonstrate the coherent incorporation of InP islands in an GaInP matrix for nominally 2.5 MLs InP. The energy of the InP p hotoluminescence (PL) shifts to lower energies (100 meV) when the grow th interruption time between the island and cap layer growth is increa sed from 1 to 300 s in case of nominally 3 MLs InP. Simultaneously, an increase of the PL linewidth is observed from 30 to 60 meV. Room temp erature photoreflectance measurements on samples with various InP thic kness have been performed. Compared to PL measurements, an additional feature in the photoreflectance spectra is observed for samples with m ore than 7 MLs InP, which is attributed to a transition between excite d electron and hole states of the islands.