Abstract
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 
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 
ions. In the presence of oxalic acid and citric acid, anodic photocurrent multiplication was observed. Under cathodic polarization in the dark, 
, 
, 
, in acid medium and 
in alkaline medium are electrochemically reduced at a diffusion‐limited rate. In 1 M KOH a high reactivity for 
reduction is observed, explaining why n‐GaN can be photoetched under open‐circuit conditions in this solution. © 2000 The Electrochemical Society. All rights reserved.