“…When an insulator is placed between the gate metal and semiconductor, i.e., metal-insulator-semiconductor field-effect transistor, an electric field generated by the gate voltage is strongly formed in the insulator having a large resistance, such that the input impedance becomes very large and the gate leakage current can be reduced. Gate leakage current in GaN-based HEMTs can be reduced using structures similar to metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs), where high-k materials, such as Si 3 N 4 and Al 2 O 3 , are deposited under the gate metal [11][12][13][14][15][16][17][18]. MIS-HEMTs have been studied by adding a high quality single dielectric layer, such as Si 3 N 4 , Al 2 O 3 , SiO 2 , HfO 2 , Sc 2 O 3 , GaO 3 , or ZrO 2 , to suppress current collapse, improve current flow, and reduce gate leakage current [14][15][16][17]19,20].…”