Optical characterization of indium-terminated GaAs(001) surfaces

We have investigated the growth of thin indium layers on As- and Ga-terminated GaAs(001) surfaces by reflectance anisotropy spectroscopy (RAS), low energy electron diffraction (LEED), and auger electron spectroscopy. Room temperature deposition of indium on the (2 X 4)/c(2 X 8) surface and subsequent annealing at 450 degrees C leads to the formation of an In-terminated surface showing a (4X2) LEED pattern, accompanied with strong changes in the measured surface optical anisotropy. When indium is deposited onto the (4X2)/c(8 X2) surface, on the contrary, the (4X2) In-terminated surface is already formed at room temperature deposition without needing annealing, as demonstrated by the RAS spectra. The finding that almost identical RAS spectra and (4X2) LEED patterns are obtained in both cases shows that the same final atomic structure is achieved. Finally, we conclude that the structure of the In-terminated surface is similar to that of the clean Ga-rich surface, although a more detailed model would need accurate calculations of the microscopic origin of the measured anisotropy.