Operation of Pt/AlGaN/GaN-Heterojunction Field-Effect-Transistor Hydrogen Sensors With Low Detection Limit and High Sensitivity

To enhance the device sensitivity and detection limit, a gate bias is applied to the catalytic metal of AlGaN/GaN- heterojunction field-effect-transistor (HFET) hydrogen sensors to control the carrier concentration in the channel at operation. The sensors exhibit a good sensitivity at temperatures up to 800degC and a detection limit of 10-ppb H₂ in N₂. The dependence of the device sensitivity on gate and drain biases has been investigated. The sensitivity peaks at the gate bias of threshold voltage and the drain bias of knee voltage in sensing gas. At high temperatures and H₂ concentrations, specifically from 300degC and 1000-ppm H₂/N₂, respectively, the sensitivity of HFETs at V_gs = -3.5 V and V_ds = 1V is more than three orders higher than their sensitivity at V_gs = 0 V and the sensitivity of Schottky diodes.