Studies of Electron Beam Evaporated SiO2/AlGaN/GaN Metal–Oxide–Semiconductor High-Electron-Mobility Transistors

The metal–oxide–semiconductor high-electron-mobility transistors (MOSHEMTs) have been demonstrated and its dc characteristics were examined and compared with the conventional AlGaN/GaN HEMTs. The electron beam (EB) evaporated SiO2 layers were used as a gate-insulator. Capacitance–voltage plot of MOS contacts revealed the existence of injection type complete accumulation up to +4.0 V. The fabricated MOSHEMTs have exhibited better dc characteristics when compared with the conventional AlGaN/GaN HEMTs. The MOSHEMTs could operate at positive gate-biases as high as +4.0 V. The 2.0-µm-gate-length EB-SiO2 MOSHEMTs exhibited higher drain current density and extrinsic transconductance of 856 mA/mm and 145 mS/mm when compared to the conventional AlGaN/GaN HEMTs. The gate leakage current (I gLeak) was three orders of magnitude lower than that of the conventional AlGaN/GaN HEMTs. The stable device operations at high operating voltages with low I gLeak and high g mmax values leads to the occurrence of low trap density at EB-SiO2/AlGaN interface.