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 Δ g m and threshold voltage variation Δ V th are 16.63 mS/mm and 318.1 mV, respectively, upon exposing to a 10000-ppm NH 3air gas. In addition, the maximum sensing response and rectification ratio of 113.4 and 2.1 ×10 3, respectively, are obtained when 10000-and 35-ppm NH 3air gases are introduced. Therefore, the studied Pt/AlGaN HFET shows the promise for ammonia-gas-sensing applications.
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