SURFACE-POTENTIAL INVERSION OF THERMAL ANNEALED GAAS (001) OBSERVED BY REFLECTANCE-DIFFERENCE SPECTROSCOPY

Reflectance-difference spectroscopy measurements in the 2.5-3.5 eV energy range have been used to study surface potential inversion in semiinsulating GaAs (001), as induced by thermal annealing in a H-2 atmosphere at temperatures up to 600-degrees-C. The electro-optic component of the reflectance difference spectra is dependent of both, magnitude and direction of the GaAs surface electric-field. Taking this into account, the surface potential inversion process is followed through the evolution of the linear electro-optic component of the reflectance-difference spectrum. The technique described in this paper turns out to be sensitive to atomic layers in a depth of 100-200 angstrom, which allows us to follow the first stages of the surface potential inversion process.