Surface chemistry and Fermi level movement during the self-cleaning of GaAs by trimethyl-aluminum

The removal of the native oxides from NH(4)OH-cleaned p-GaAs (100) by exposure to trimethyl-aluminum (TMA) was studied by in situ photoelectron spectroscopy using synchrotron radiation. The reduction of high-valence As- and Ga-oxides occurred through different routes: while As(3+) was reduced to As((1 +/-Delta)+) suboxides (with 0 <= Delta <= 1), Ga(3+) was directly removed. The surface Fermi level was shifted by about 100 meV towards the valence band edge upon TMA exposure. This indicates that removing the native oxide of GaAs by TMA is insufficient to create interfaces between GaAs and Al(2)O(3) with defects densities below the 10(12) cm(-2) range. (C) 2011 American Institute of Physics. [doi:10.1063/1.3615784]