PHOTOELECTROCHEMICAL ETCHING OF N-GAAS(001) ELECTRODES STUDIED USING REFLECTANCE ANISOTROPY

We demonstrate here that the novel ''epioptic'' technique of reflectance anisotropy (RA) is capable of detecting in real time, variations in the optical anisotropy of an GaAs(001) electrode surface during anodic oxidation in aqueous KCl solutions. A novel system is described in which the exciting probe laser beam also excites minority charge carriers (boles) in the n-type materials thus giving rise to the photoelectrochemical oxidation reaction. The influence of the neutral additive pyridine upon the etching kinetics is described while the nature of the changes in surface structural anisotropy are discussed in terms of possible surface reconstruction in aqueous solution, the appearance of highly oriented macroscopic etch features and the possible formation of oriented surface layers.