AlGaN/GaN-based metal–oxide–semiconductor diode-based hydrogen gas sensor

Abstract

The characteristics of Sc2O3/AlGaN/GaN metal–oxide–semiconductor (MOS) diodes as hydrogen gas sensors are reported. At 25 °C, a change in forward current of ∼6 mA at a bias of 2 V was obtained in response to a change in ambient from pure N2 to 10% H2/90% N2. This is approximately double the change in forward current obtained in Pt/GaN Schottky diodes measured under the same conditions. The mechanism of the change in forward gate current appears to be formation of a dipole layer at the oxide/GaN interface that screens some of the piezo-induced channel charge. The MOS-diode response time is limited by the mass transport of gas into the test chamber and not by the diffusion of atomic hydrogen through the metal/oxide stack, even at 25 °C. These devices look promising for applications requiring sensitive, long-term stable detection of combustion gases.