PHOTOELECTROCHEMICAL ETCHING OF P-INP IN NITRIC-ACID SOLUTIONS

Photoelectrochemical (PEC) studies of p-InP in various nitric acid sol utions demonstrated that the semiconductor undergoes etching with favo rable etch rates in the negative potential region. The etch rate incre ases with decreasing potentials to -1.0 V and exhibits a small decreas e with still lower potentials. Etch rates are proportional to light in tensity. The values of etch rate for p-InP biased at -1.0 V vary from 0.07 to 1.24 mu m/min for HNO3 solutions with concentrations ranging f rom 1.0 to 5.0 M. With acid concentrations greater than 5 M, the etch rates were inconsistent. Little or no PEC etching was observed with ni tric acid concentrations greater than 7.5 M. Voltammetry shows that ph otoreduction of protons and possibly nitric acid takes precedence over the photoreduction of InP to In in higher HNO3 concentrations.