Electrochemistry and photoetching of n-GaN

The (photo)electrochemical behavior of n-GaN[0001] in various aqueous solutions was studied using rotating-disk voltammetry, cyclic voltammetry, and electrical impedance measurements. it was found that the bandedges of the semiconductor shift over 60 mV/pH unit, indicating acid-base equilibria at the interface. In H2SO4 and KOH solutions, the photocurrent under anodic bias is associated with the oxidation of the semiconductor according to a three-equivalent reaction, leading to dissolution and roughening of the surface. In 1.2 M HCl solutions, n-GaN is stabilized for anodic decomposition due to the competing oxidation of Cl- ions. in the presence of oxalic acid and citric acid, anodic photocurrent multiplication was observed. Under cathodic polarization in the dark, Fe3+, Ce4+, HIO3, in acid medium and Fe(CN)(6)(3-) in alkaline medium are electrochemically reduced at a diffusion-limited rate. In I M KOH a high reactivity for O-2/H2O reduction is observed, explaining why n-GaN can be photoetched under open-circuit conditions in this solution. (C) 2000 The Electrochemical Society. S0013-4651(99)05-098-3. All rights reserved.