Hydrogen sensors based on GaN diodes: The sensing mechanism

In this paper, interaction mechanism of hydrogen with GaN metal-insulator-semiconductor (MIS) diodes has been investigated, focusing on the metal/semiconductor interfaces. As a result, the following three points are revealed: First, MIS Pt-SiO₂-GaN diodes show a marked improvement in detection sensitivity, suggesting that the device interface plays a critical role in sensing. Second, exposure of the diodes to hydrogen is found to change the conduction mechanisms from Fowler-Nordheim tunneling to Pool-Frenkel emission. Third, interface trap level density of the diodes is found to be reduced by hydrogen exposure even at room temperature. These results support the validity of the hydrogen-induced dipole layer model.