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.