Electron auger spectroscopy and reflectance anisotropy spectroscopy of monolayer nitride films on (001) surfaces of GaAs and GaSb crystals

The methods of electron Auger spectroscopy and reflectance anisotropy spectroscopy are used to study monolayer films of gallium nitride formed on the (001) surface of GaAs by chemical nitridization in hydrazine-sulfide solutions. It is found that the Auger signal for nitrogen N KLL from the nitride film is shifted to higher kinetic energies by $\sim$17.2 eV in comparison with its position for the same signal for a bulk GaN crystal. The observed shift is caused by the specific configuration of the valence orbitals of nitrogen atoms terminating the nitridized GaAs (001) surface. One of the valence orbitals for these atoms does not form a chemical bond and is occupied by an uncoupled pair of electrons. The suggested configuration is confirmed by the results of an analysis of the spectra of anisotropic reflectance from the nitridized GaAs (001) surface. Experiments with chemical nitridization of a GaSb surface have been performed for the first time. The Auger spectra for a nitridized GaSb (001) surface are found to be similar to those for a nitridized GaAs (001) surface. This is indicative of the similar character of chemical processes on these surfaces and the formation of a monolayer nitride film on the GaSb surface.