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-SiO ₂ 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.