EFFECTS OF SULFUR TREATMENT AND HYDROGEN PLASMA TREATMENT ON GAAS

Photoluminescence (PL) and photoreflectance (PR) measurements have bee n carried out to investigate the surface state behavior for sulfur-tre ated GaAs as well as the neutralization effect on the carbon accepters for hydrogen- or nitrogen-plasma-treated GaAs. Whereas the intensity of the PL signal for the sulfur-treated GaAs increased monotonically a s the sulfur-treatment time increased, the intensity of the PR signal increased until the sulfur treatment time of 110 min, and thereafter d ecreased. These results indicate that a decrease in the number of the surface states and the formation of a quasi-flat band as a result of t he sulfur treatment nt. After the GaAs was hydrogen-plasma-treated and annealed at 400 degrees C, the relative PL intensity ratio between th e donor-bound exciton and the carbon acceptor increased by a factor of 2, and a variation in the PR broadening parameter was induced by neut ralization of the carbon accepters due to the combination of the hydro genic ions and the carbon ions in the GaAs. Variation in the surface s tates and neutralization of the ions affect the intensity of the PL sp ectra and the intensity and the broadening parameter of the PR signal.