Interface states in metal-insulator-semiconductor Pt-GaN diode hydrogen sensors

Abstract

Exposure of Pt-SiO2-GaN metal-insulator-semiconductor (MIS) diodes to hydrogen at room temperature is found not only to shift the flat-band voltage toward negative bias values as compared with that in nitrogen, which results in significant sensitivity of the devices to hydrogen, but also to reduce the interface state density (Dit) dramatically for the first time. Pt-SiO2-GaN MIS diodes in nitrogen yields the Dit of ∼8 × 1011 cm−2 eV−1 at 0.4 eV from the conduction band edge (Ec), and hydrogen exposure reduces the Dit by more than one order of magnitude to the low 1010 cm−2 eV−1 range. In sharp contrast to Pt-SiO2-GaN MIS diodes, neither flat-band voltage shift nor Dit (∼1 × 1013 cm−2 eV−1 at 0.4 eV) reduction is observed for Pt-SixNy-GaN MIS diodes upon hydrogen exposure. These results suggest that atomic hydrogen interacts with MIS interface in Pt-SiO2-GaN MIS diodes even at room temperature. In addition, hydrogen treatment would be a promising method in order to reduce the Dit in GaN metal-oxide-semiconductor field-effect transistors using SiO2 as the gate dielectric, leading to the mobility enhancement of the devices.