Comparison of MOS and Schottky W/Pt-GaN diodes for hydrogen detection

W/Pt contacted GaN Schottky diodes show forward current changes of >1 mA at low bias(3 V) in the temperature range 350-600 degreesC when the measurement ambient is changed from pure N-2 to 10%H-2/90%N,). In this paper we show that use of a metal-oxide-semiconductor (MOS) diode structure with S2O3 gate dielectric and the same W/Pt metallization show these same reversible changes in forward current upon exposure to H-2-containing ambients over a much broader temperature range (90 to > 625 degreesC). The increase in current in both cases is the result of a decrease in effective barrier height of the MOS and Schottky gates of 30-50 mV 10%H-2/90%N? ambients relative to pure N-2 and is due to catalytic dissociation of the H-2 on the Pt contact, followed by diffusion to the W/GaN or Sc2O3/GaN interface. The presence of the oxide lowers the temperature at the hydrogen which can be detected and in conjunction with the use of the high temperature stable W metallization enhances the potential applications of these wide bandgap sensors. (C) 2004 Elsevier B.V. All rights reserved.