AlGaN/GaN HEMT Based Hydrogen Sensors With Gate Absorption Layers Formed by High Temperature Oxidation

Abstract

We present a new approach in design of high temperature stable AlGaN/GaN HEMT gate absorption layers for hydrogen sensing at elevated temperature. To suppress undesirable chemical interaction of Pt on the gate interface, a thin conductive IrO2 oxide layer (t ∼ 10 nm) is formed by high temperature oxidation (T= 800 ̊C for 1min in O2 ambience) before Pt catalytic metal deposition. The comparative study of the hydrogen detection on AlGaN/GaN HEMT device with the Pt and Pt-IrO2 based gate absorption layers is shown. The sensitivity of the Pt gate Schottky diode is significantly enhanced with the insertion of IrO2 gate interfacial layer. The proposed Pt-IrO2 gate based diode exhibits a maximum sensing response value of 70%/ppm at 100 ̊C under a 0.1% H2/N2 gas. As comparing with the conventional Pt diode it is increased by more than 12 times. Additionally, the operating temperature for the maximum sensing response is decreased from 150 ̊C to 100 ̊C with the insertion of IrO2 interfacial layer. Moreover, the Schottky gate barrier height lowering at is found to be 254 meV and 100 meV for the IrO2 and Pt gate based diodes, respectively.