Modeling the Electrical Response of Hydrogen Sensors Based on AlGaN/GaN High-Electron-Mobility Transistors

Abstract

The electrical response of hydrogen sensors based on Al0.30Ga0.70N/GaN high-electron-mobility transistors (HEMTs) with Pt catalytic gate electrodes was measured in a flowing gaseous stream consisting of hydrogen in a pure nitrogen diluent at ambient and elevated temperatures. The sensor response was found to monotonically increase for a wide range of hydrogen concentrations (500 ppb to 5 vol%). Various models based upon Langmuir adsorption were investigated to describe the sensor response in this regime. A simple two-state model involving two distinct hydrogen binding states that have previously been observed in surface studies was found to adequately describe sensor response from 500 ppb to 5 vol% hydrogen in nitrogen. The relevance of other modified Langmuir models to adequately describe the sensor response as a function of hydrogen concentration is also discussed.