THE PHOTOELECTROCHEMICAL ETCHING OF (100) AND (111BAR) P-INP

The photoelectrochemical etching of (100) and (111BAR) p-InP has been investigated in several electrolytes. The reactions involve the photoreduction of the p-InP surface producing an insoluble product, indium, followed by its anodic stripping at a more positive potential. Etch rates in excess of 2-mu-m/min have been obtained. High light to dark selectivity can be obtained with etch rates from 0.1 to 0.5-mu-m/min. The etching is dependent upon crystal face, temperature, electrode potential, and the cycle time of the potential step. The reactions have been investigated by capacitance measurements, cyclic voltammetry, chronoamperometry, and photoetching measurements. The instability of bare InP in regards to its use as a photoanode in hydrogen production is discussed.