A Systematic Analysis on the Applications of AlGaN/GaN HEMT for High-Performance Sensing

High-electron-mobility transistors (HEMTs) are revolutionary breakthrough in the field of sensor technology due to their high sensitivity, short-response time, and versatility depending upon the working environment and function. In gas sensing, HEMTs show great selectivity and sensitivity to hydrogen, ammonia, and volatile organic compounds based on the highly developed surface charge modulation processes. The biosensing applications show an example of the incorporation of functionalized gate structures for improved accuracy in biomolecular binding, employed for diagnostic and monitoring purposes in clinical and environmental fields. The pH sensor design uses AlGaN/GaN hetero-structures and Au functional layers for real time and monitoring of ions and improved sensing in challenging operating conditions. Au-gated HEMTs measure pH with near-ideal sensitivity (around 58 mV/pH) and millisecond response times across pH 2–12. These devices work reliably from cryogenic temperatures to around 500 $^{\circ }$C while keeping signal-to-noise ratios above 50 dB. Due to the combined effort of material sciences and device engineering HEMT sensors have demonstrated a level of performance that creates the way for their usages in sensitive industrial, environmental, and medical applications. This review presents a detailed state-of-the-art analysis of GaN HEMT-based sensor applications.