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The mechanism and influence of photogalvanic interactions during localized photoetching of III-V semiconductors have been investigated. Starting from the cyclovoltammograms and etching kinetics in the dark and under uniform illumination, the chemistry of the mixed dark/illuminated system is discussed. Both in terms of current-potential curves and of band-energy diagrams, it is demonstrated how a geometrical separation of partial hole and electron currents can lead to the strong enhancement of etch rates under localized illumination. Some illustrative experiments are discussed, quantitatively. In the present work GaAs in acidic H202 and $2082-solutions are used as model systems, but in addition some results from other III-V compounds and etchants are presented.

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The chemical oxidation of hydrogen-terminated silicon (111) surfaces in water was studied in situ with Fourier transform IR spectroscopy in the multiple total internal reflection mode. On the basis of measurements of the absorbance of the Si-H and Si-O-Si vibrations as a function of time it is concluded that reactions involving the oxidation of silicon hydride and the formation of silicon oxide are coupled. The decrease in the hydride coverage and increase in the oxide coverage are linear functions of ln(t). The time dependence of oxide growth is explained in terms of electrostatic and mechanical changes at the Si/water interface.