Optical characterization of indium-terminated GaAs(001) surfaces

We have investigated the growth of thin indium layers on As- and Ga-termina ted GaAs(001) surfaces by reflectance anisotropy spectroscopy (RAS), low en ergy electron diffraction (LEED), and auger electron spectroscopy. Room tem perature deposition of indium on the (2 X 4)/c(2 X 8) surface and subsequen t annealing at 450 degrees C leads to the formation of an In-terminated sur face showing a (4X2) LEED pattern, accompanied with strong changes in the m easured surface optical anisotropy. When indium is deposited onto the (4X2) /c(8 X2) surface, on the contrary, the (4X2) In-terminated surface is alrea dy formed at room temperature deposition without needing annealing, as demo nstrated by the RAS spectra. The finding that almost identical RAS spectra and (4X2) LEED patterns are obtained in both cases shows that the same fina l 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 micr oscopic origin of the measured anisotropy.