SURFACE-STATE BEHAVIOR AND NEUTRALIZATION OF IMPURITIES IN SULFUR-TREATED, HYDROGENATED, AND ANNEALED GAAS

Surface state behavior and neutralization of impurities in sulfur-trea ted, hydrogenated, and annealed Si-doped bulk GaAs and nominally undop ed GaAs layers have been studied. While the intensity of the photolumi nescence (PL) spectra for the sulfur-treated GaAs dramatically increas ed in comparison to that for as-grown GaAs, the signal for the as-grow n GaAs measured by photoreflectance (PR) vanished after sulfur treatme nt. After the GaAs was hydrogenated and annealed, the relative PL inte nsity ratio between the donor-bound exciton and the carbon acceptor in creased, and a variation in the PR broadening parameter was induced by neutralization of the carbon accepters. Variations of the surface sta tes and neutralization of the carbon ions affect the intensity of the PL spectra and the intensity and the broadening parameter of the PR si gnal. These results indicate that the sulfur treatment removes the dan gling bonds at the GaAs surface and that the thermal treatment breaks the bonds between hydrogen atoms and carbon ions in GaAs.