Suspended AlGaN/GaN HEMT NO₂ Gas Sensor Integrated With Micro-heater

Abstract

We developed an AlGaN/GaN high electron mobility transistor (HEMT) sensor with a tungsten trioxide (WO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) nano-film modified gate for nitrogen dioxide (NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) detection. The device has a suspended circular membrane structure and an integrated micro-heater. The thermal characteristic of the Platinum (Pt) micro-heater and the HEMT self-heating are studied and modeled. A significant detection is observed for exposure to a low concentration of 100 ppb NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> at ~300 °C. For a 1 ppm NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gas, a high sensitivity of 1.1% with a response (recovery) time of 88 second (132 second) is obtained. The effects of relative humidity and temperature on the gas sensor response properties in air are also studied. Based on the excellent sensing performance and inherent advantages of low power consumption, the investigated sensor provides a viable alternative high performance NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> sensing applications. It is suitable for continuous environmental monitoring system or high temperature applications.