OBSERVATION OF GA SEGREGATION IN THE GROWTH OF INAS OVERLAYERS ON GAAS(110) USING CORE-LEVEL PHOTOELECTRON-SPECTROSCOPY

We have investigated the molecular-beam epitaxy of InAs on GaAs(110) b y in situ soft x-ray photoelectron spectroscopy using synchrotron radi ation, Core-level spectra from InAs overlayers show Ga emission for ov erlayer thicknesses far beyond the electron mean free path. It is conc luded that this emission reflects Ga segregated from the substrate. Th is interpretation is supported by observations of strongly reduced Ga signals for samples grown at lower temperature. Since Ga segregation i s known not to occur for In(Ga)As growth on GaAs(100), our findings im ply strong orientation dependence in the segregation process. To our k nowledge this is the first time that this kind of dependence is observ ed on semiconductors.