On an Ammonia Gas Sensor Based on a Pt/AlGaN Heterostructure Field-Effect Transistor

A new and interesting Pt/AlGaN heterostructure field-effect transistor (HFET)-based ammonia gas sensor is fabricated and investigated. The related ammonia-sensing mechanisms, including direct dissociation of ammonia gas and triple-point model, are presented. Experimentally, the maximum transconductance variation Δg
_m
and threshold voltage variation ΔV
_th
are 16.63 mS/mm and 318.1 mV, respectively, upon exposing to a 10 000-ppm NH
₃
/air gas. In addition, the maximum sensing response and rectification ratio of 113.4 and 2.1 × 10
³
, respectively, are obtained when 10 000- and 35-ppm NH
₃
/air gases are introduced. Therefore, the studied Pt/AlGaN HFET shows the promise for ammonia-gas-sensing applications.