Interface properties of metal/n- and p-GaN Schottky diodes are studied by I-V-T and C-V-T measurements, and simulation of their characteristics. On the basis of the previously pro-posed "surface patch" model, the gross behavior of I-V-T characteristics, which includes Richardson plots together with temperature dependence of the effective Schottky barrier heights (SBHs) and n-values, can be well reproduced. Furthermore, the dependence of the true SBH on the metal work function was also deduced from high-temperature I-V curves, giving S-values of 0.28 and 0.20 for n- and p-GaN samples, respectively, and the interface Fermi level tends to be pinned at a characteristic energy of about two-third of the bandgap. (C) 2002 Elsevier Science B.V. All rights reserved.