In this study, a novel Pd/native nitride/n-GaAs structure was developed and investigated as hydrogen sensor. Thin layers of native nitride on n-GaAs (100) epitaxial crystals was grown by anodic nitridation, and I'd thin layer as gate electrode was evaporated on the native nitride film in high vacuum. Electrical and hydrogen sensing properties of the structures were obtained from the current-voltage (I-V), capacitance-voltage (C-V) and capacitance-time (C-t) characteristics measured in a computer controlled flow set-up at temperatures of 50, 90 and 130 degrees C, respectively. The samples show a behavior like a Schottky diode. The thicker sample has smaller leakage current and greater breakdown voltage. The sensor responses are totally reversible with response and recovery times, 35 and 40 s, respectively. The device with the thickest native nitride film showed better sensitivity, and the detection limit was lower than 20 ppm for H-2. (C) 2007 Elsevier B.V. All rights reserved.