INVESTIGATION ON THE ELECTROCHEMISTRY AND ETCHING AT THE (100)GAAS-VERTICAL-BAR-HIO3 INTERFACE

The electrochemical and etching behaviour of n- and p-(100)GaAs in aqu eous iodic acid solutions (pH 0) was studied by rotating-(ring)-disk v oltammetry, impedance measurements and etch rate measurements. Under a ll circumstances, a competition for HIO3 exists between electrochemica l and etching reactions, the supply of HIO3 to the surface being diffu sion-controlled. A particularly interesting effect is the cathodic pho tocurrent enhancement, up to a factor of about 6, which is observed at the p-GaAs electrode. ?The experimental results allow us to propose m echanisms for the various processes under investigation. Differences i n electrochemical and etching behaviour compared with the systems GaAs /IO3- (pH 14) and InP/HIO3 (pH 0) are discussed.