APPLICATION OF ANGLE-RESOLVED X-RAY PHOTOELECTRON-SPECTROSCOPY TO THE STUDY OF GAAS(001) SURFACES AND METAL GAAS(001) INTERFACES

GaAs (001) surfaces and metal/GaAs (001) interfaces were investigated by angle resolved X-ray photoelectron spectroscopy and these studies are presented as examples of the application of this technique. By analysing the photoemission mean intensity from normal to grazing incidence on a GaAs (001) substrate decapped and annealed, it was possible to determine the arsenic concentration in the topmost layers at the surface as a function of the annealing temperature. This technique is also a structural probe since photoelectron diffraction effects in monocrystalline samples give rise to modulations in the intensity when scanning the emission angle. Evidence was thus obtained of the lattice registry of a YbAs overlayer with respect to a GaAs (001) substrate. The mixed (Yb-As) (010) crystallographic planes of YbAs position themselves in the prolongation of the pure As planes of GaAs. In the case of Ni depositions performed on a GaAs (001) substrate, it was shown that Ni reacts with GaAs to form two distinct reaction products, one Ga rich and the other As rich.