Ammonia Sensing Properties of a Pt/AlGaN/GaN Schottky Diode

An interesting Pt/AlGaN/GaN Schottky-type ammonia gas sensor is fabricated and studied. Both the steady-and transient-state behaviors of ammonia adsorption reactions are investigated. At 150°C, significant ammonia detection is observed under a low ammonia concentration of 35-ppm NH₃/air. Moreover, a high ammonia sensing response of 18300% and the large Schottky barrier variation ratio A.φ_b/φ_b, air of 13.8% are observed upon exposure to a 1% NH₃/air gas at 150°C. The presence of dipoles at the metal-semiconductor interface leads to a lowering effect of Schottky barrier height and a larger current. In addition, based on thermodynamics, in contrast with a hydrogen adsorption reaction, the ammonia adsorption reaction is an endothermic reaction. Consequently, the studied NH₃ sensor structure provides the promise to integrate high-performance AlGaN/ GaN-based optoelectronic and microwave devices on a single chip.