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

The characteristics of Sc2O3/AlGaN/GaN metal-oxide-semiconductor (MOS) diodes as hydrogen gas sensors are reported. At 25degreesC, a change in forward current of similar to6 mA at a bias of 2 V was obtained in response to a change in ambient from pure N-2 to 10% H-2/90% N-2. 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 25degreesC. These devices look promising for applications requiring sensitive, long-term stable detection of combustion gases. (C) 2004 American Institute of Physics.