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

We demonstrate here that the novel ''epioptic'' technique of reflectan ce anisotropy (RA) is capable of detecting in real time, variations in the optical anisotropy of an GaAs(001) electrode surface during anodi c oxidation in aqueous KCl solutions. A novel system is described in w hich the exciting probe laser beam also excites minority charge carrie rs (boles) in the n-type materials thus giving rise to the photoelectr ochemical oxidation reaction. The influence of the neutral additive py ridine upon the etching kinetics is described while the nature of the changes in surface structural anisotropy are discussed in terms of pos sible surface reconstruction in aqueous solution, the appearance of hi ghly oriented macroscopic etch features and the possible formation of oriented surface layers.