Photoelectrochemical etching of <i>p</i>-GaAs

Abstract

A photoelectrochemical method for etching p-GaAs is reported. The method overcomes the apparent stability of GaAs to reductive decomposition by switching the potential of the p-GaAs between a value at which photogenerated electrons reduce the surface to Ga and As3−, and a more positive value at which the majority carrier holes oxidize the Ga to Ga3+. Etching has been observed in a variety of acidic and basic solutions in which As3− and Ga3+ are soluble. With a 633-nm He-Ne laser beam having a peak intensity of 0.75 W cm−2, a maximum etch rate of 1300 Å/min has been obtained in a 0.1-M H2SO4–0.1-M NaSCN solution. The rate of etching appears to be limited by the rate of dissolution and transport of the products away from the surface. The method is potentially useful for producing anisotropic etching in a variety of GaAs devices.