Exposure of Pt/GaN and Pt/AlGaN/GaN Schottky diodes to H-2 gas at moderately high temperatures around 100 degrees C resulted in marked increase of forward and reverse currents. Increase was much larger in the Pt/AlGaN/GaN diode than in the Pt/GaN diode. Rapid turn-on responses and somewhat slower turn-off responses were observed with reproducible response magnitudes. A rigorous computer simulation of I-V curves indicated that current changes are due to changes in the Schottky barrier height caused either by H-induced formation of interfacial dipole or by hydrogen passivation of interface states. (c) 2005 Published by Elsevier B.V.