Al₂O₃-passivated graded-barrier Al_xGa_1-xN/AlN/GaN/Si heterostructure field-effect transistor by hydrogen peroxide oxidization method

This letter reports a novel Al₂O₃-passivated graded-barrier (GB) Al_xGa_1-xN/AlN/GaN/Si heterostructure field-effect transistor (HFET) formed by using hydrogen peroxide (H₂O₂) oxidization method. Different from the Al_0.26Ga_0.74N conventional barrier (CB), a compositionally graded Al_xGa_1-xN (x = 0.22∼0.3) barrier was devised to increase the Schottky-barrier height (_B) and improve the interfacial quality at the same time. Reduced gate leakage and enhanced device gain are further achieved by the Al₂O₃ passivation. The present Al₂O₃-passivated/unpassivated GB-HFETs (unpassivated CB-HFET) has demonstrated improved maximum drain-source current density (I_{DS, max}) of 708/699 (654) mA/mm at V_DS = 7 V, maximum extrinsic transconductance (gm, _max) of 139/126 (113) mS/mm, subthreshold swing (SS) of 176/253 (274) mV/dec, on/off-current ratio (I_on/I_off) of 3.8 × 10⁶/1.4 × 10⁴ (7.1 × 10³), two-terminal off-state gate-drain breakdown voltage (BV_GD) of −126.4/−96.8 (−89.3) V, turn-on voltage (V_on) of 1.1/0.7 (0.3) V, and three-terminal on-state drain-source breakdown voltage (BV_DS) of 109/89 (71) V.