KINETICS OF GAAS(100) SURFACE PASSIVATION IN AQUEOUS-SOLUTIONS OF SODIUM SULFIDE

The photoluminescence intensity variation of GaAS (100) after surface passivation in aqueous solutions of sodium sulfide has been studied as a function of the processing time, the temperature, and the compositi on of the sulfide solution. It is shown that, as the processing time i n the sulfide solution increases, the intensity of the photoluminescen ce peak first increases and then saturates. The time required to attai n saturation depends on the alkalinity of the solution and on the sulf ide-ion concentration in it. For fixed processing time, the intensity of the photoluminescence peak increases as the sulfidation temperature increases. X-ray photoelectron spectroscopy data for the sulfided sur faces, first, shows the presence of Ga-S bonds and, second, indicates that the concentration of arsenic oxides on the semiconductor surface decreases as the sulfidation temperature increases. The increase in th e photoluminescence intensity accompanying sulfide passivation is attr ibuted principally to the decrease in the concentration of these oxide s. (C) 1996 American Institute of Physics.