The role of surface charging and potential redistribution on the kinetics of hole injection reactions at n-GaAs

The dissolution rate of GaAs in alkaline solutions in the pH range 11–14 was shown to be limited by OH- diffusion in the solution. The kinetics of the hole injection from an oxidizing agent in solution into the valence band of n-GaAs changes when the hole injection rate is larger than the dissolution rate. In this study Fe(CN)3-6 was used as an oxidizing agent. From the results of impedance measurements it was shown that, due to interface charging effects, a shift of the semiconductor band edges of more than 0.5 V reduces drastically the overlap between the valence band and the distribution function of Fe(CN)3-6; the hole injection reaction becomes kinetically controlled. Photoanodic dissolution of n-GaAs also influences the kinetics of the hole injection from solution. At higher light intensities the rate of reduction of the oxidizing agent can be reduced almost to zero.