A new application for heteropolyanions:: etching of III-V semiconductor compounds

This paper deals with the behaviour of two Keggin-type heteropolyanions: SiMo12O404- and SiW12O404- dissolved in aqueous acidic solution, towards semiconductors, at rest potential. Two III-V semiconductors are studied, GaAs and InP. At the material/solution interface, GaAs undergoes an oxidation/dissolution process while the heteropolyanions are reduced. These reactions lead to the growth of a film on the GaAs surface, its composition was determined by X-ray photoelectron spectroscopy. In the dark, at the InP/solution interface no reaction occurs whatever the heteropolyanion used. However, in the presence of SiMo12O404-, when an n-type InP semiconductor is illuminated (hupsilon > 1.35 eV) the heteropolyanions are reduced and the photodissolution of the material is achieved, no surface film is present on the etched surface. The difference of behaviour between GaAs and InP is primarily due to the difference of the positions of the semiconductor energy-band edges with respect to the first redox potential of the heteropolyanions.