A picosecond photoluminescence and electrochemical study of the n-gallium arsenide/electrolyte interface in a nonaqueous photoelectrochemical cell

Anodic photocorrosion and cathodic photowashing of n-GaAs (100) in a nonaqueous photoelectrochemical cell have been studied using photoluminescence decays and the voltage dependence of both photoluminescence intensity and photocurrent. The electrochemistry occurring at the solid/nonaqueous liquid junction is found to have a strong influence on the observed photoluminescence as seen by photoluminescence vs. voltage scans and by trends in the time resolved photoluminescence decays. Photocorrosion of the cell surface due to trace water contamination, results in an increased surface recombination velocity and an overall loss in photoluminescence intensity, but does not affect the photocurrent. The stability of the photocurrent upon corrosion of the cell implies that the photoinduced surface states resulting from the corrosion are intrinsically different from those observed in all other systems studied previously in this laboratory. The effect of corrosion of the cell on the PL-V profile is examined in detail. It is found that the inclusion of the redox couple gives some protection from corrosion. The techniques listed above were also used to monitor changes in the n-GaAs/methanol interface with incremental water additions to the cell to study the effects of water contamination. XPS measurements are used to explore the effects of photocorrosion on the GaAs surface by monitoring changes in the chemical environment of GaAs surface species.