ON THE EFFECT OF SURFACE PRETREATMENT UPON THE ELECTRONIC STRUCTURE OF n-GaN SURFACES

摘要

Charge transfer reactions and recombination processes were studied at the jvGaN/electrolyte interface at electrodes which were either "new"(i.e. not subjected to any pretreatment besides a 6 M HC1 dip) or photoanodieally etched in 1 M H2SO4 solutions prior to the experiments. Photocurrent multiplication studies show that that etching leads to an increase of the photocurrent multiplication factor at n-GaN in formic acid containing solutions. From impedance measurements it follows that the surface treatment provokes an irreversible shift of the flat-band potential and a curving of the Mott-Schottky plots. Electroluminescence spectra recorded in aqueous solutions containing persulfate ions at etched electrodes show a different spectral distribution as compared to spectra, recorded at new electrodes. These results can be explained by an effect of photoanodic etching upon the nature and/or concentration of intrinsic surface states at or in the vicinity of the n-GaN surface.