Hydrogen sensing performances of Pt/i-ZnO/GaN metal-insulator-semiconductor diodes

In light of the same wurtzite structure and the similar lattice constant and band gap energy between ZnO and GaN-based semiconductors, a high quality intrinsic ZnO film is used as the insulating layer for the Pt/i-ZnO/GaN metal-insulator-semiconductor (MIS) hydrogen gas sensors. When the MIS hydrogen gas sensors are exposed to dilute hydrogen ambience, hydrogen dipoles are formed at the Pt/i-ZnO interface with electrons released back to the ZnO. The hydrogen adsorbed reaction leads to the reduction of the barrier height and the series resistance. When the Pt/i-ZnO(10 nm)/GaN hydrogen gas sensors are exposed to 10,000 ppm H₂ at a room temperature, the resultant barrier height change is 211.9 meV and the series resistance is reduced from 21.4 kΩ to 13.4 kΩ. When the operation temperature increases to 500 K, the corresponding barrier height change is 124.5 meV while the series resistance reduces from 2.5 kΩ to 2.3 kΩ. The hydrogen absorption enthalpy at the interface is about -11.8 kJ/mol, which is the characteristic of exothermic reaction.