On an Electroless Plating (EP)-Based Pd/AlGaN/GaN Heterostructure Field-Effect Transistor (HFET)-Type Hydrogen Gas Sensor

A Pd/AlGaN/GaN heterostructure field-effect transistor (HFET)-type hydrogen gas sensor, based on the sensitization, activation, and electroless plating (EP) deposition processes, is fabricated and studied. Due to the used sensitization and activation approaches, a dense and uniform EP seed layer could be achieved. Good dc and microwave characteristics, including the higher turn-on voltage, lower reverse leakage current, improved thermal stability of drain current, enhanced unity current gain cutoff frequency, and maximum oscillation frequency, are obtained for a 1-m-gate-length device. Moreover, the significant hydrogen gas sensing performance, such as larger drain current variation and higher hydrogen detection sensitivity, are found under 1% and 5 ppm H₂/air ambiences, respectively. Consequently, the studied EP-based Pd/AlGaN/GaN HFET gives the promise for high-performance electronic device and hydrogen gas sensor applications.