Hydrogen sensing characteristics of a Pt/AlGaN/GaN heterostructure field-effect transistor (HFET) prepared by sensitization, activation, and electroless plating (EP) approaches

A Pt/AlGaN/GaN heterostructure field-effect transistor (HFET), based on sensitization, activation, and electroless plating (EP) deposition approaches, is fabricated and studied. Utilizing the sensitization and activation processes, a dense and uniform Pd seed layer could be implanted on the AlGaN layer prior to Pt-gate formation. In addition, a dense Pt-gate morphology and excellent Schottky contact properties are obtained. This causes significant improvement in DC performance and thermal stabilities as compared with a thermal evaporation (TE)-based one. For a used gate dimension of 1 × 100 μm2, the lower gate leakage current of 0.9 (8.4) nA, higher maximum extrinsic transconductance of 90.1 (52.1) mS/mm, and maximum drain saturation current of 325 (178) mA/mm are found for an EP Pt-gate HFET at 300 (600) K. Moreover, as a hydrogen gas sensor, the maximum drain current response (13.7%), high on/off ratio (8 × 105), and fast response (28 s) and recovery (36 s) time constants in 10,000, 50, and 5 ppm H2/air gases are obtained at 400 K, respectively. Therefore, the studied EP Pt-gate HFET shows promise for a high-performance electronic device and hydrogen gas sensing applications.