ARSENIC PRESSURE-DEPENDENCE OF THE SURFACE-DIFFUSION IN MOLECULAR-BEAM EPITAXY ON (111)B-(001) MESA-ETCHED GAAS SUBSTRATES STUDIED BY IN-SITU SCANNING MICROPROBE REFLECTION HIGH-ENERGY ELECTRON-DIFFRACTION

The arsenic pressure dependence of surface diffusion of Ga adatoms in molecular beam epitaxy (MBE) on (111) B-(001) mesa-etched substrates was investigated by means of in situ scanning microprobe reflection high-energy electron diffraction (mu-RHEED). It was observed for the first time that the direction of Ga adatom migration from or to the (111)B sidewall is changed depending on the arsenic pressure. Furthermore, the diffusion length of Ga adatoms on the (001) surface along the [110BAR] direction was found to vary with arsenic pressures exponentially; however, it was independent of the direction of lateral migration. The diffusion length of Ga adatoms on the (001) surface along the [110BAR] direction varied from about 0.25 mum to 1.2 mum at 600-degrees-C within our arsenic pressure range. This suggests that the lifetime of Ga adatoms before incorporation into the crystal on each surface depends strongly on arsenic pressure.