Pt/n-GaN and Pd/n-GaN Schottky diodes were characterized for their response to hydrogen as a function of measurement temperature. Even at modest temperatures (80-140 °C), an 80 μm diameter diode shows a large increase (≥0.5 mA) in forward current upon introduction of ∼10% H2 into a N2 ambient. The change in current increases with measurement temperature and begins essentially immediately upon introduction of the hydrogen. Cycling the ambient from N2 to 10% H2 in N2 and back to N2 produces reproducible cycling of the forward current at fixed forward bias. The decrease in barrier height of Pt on GaN was 50 mV at 25 °C and 70 mV at 150 °C upon introduction of H2 into the ambient, with lower values for Pd. At high temperature, the time response of the sensors appears to be controlled by hydrogen diffusion to the metal/GaN interface, while at low temperatures (<100 °C), dissociation of the gas appears to be the rate-determining step.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering
- Materials Chemistry