0.25 μm self-aligned AlGaN/GaN high electron mobility transistors

Self-aligned AlGaN/GaN high electron mobility transistors grown on semiinsulating SiC substrates with a 0.25 μm gate-length were fabricated using a single-step ohmic process. Our recently developed Mo/ Al/Mo/Au-based ohmic contact requiring annealing temperatures between 500 °C and 600 °C was utilized. Ohmic contact resistances between 0.35-0.6 Ω · mm were achieved. These 0.25 μm gate-length devices exhibited drain current density as high as 1.05 A/mm at a gate bias of 0 V and a drain bias of 10 V. A knee voltage of less than 2 V and a peak extrinsic transconductance (g_m) of 321 mS/ mm were measured. For their microwave characteristics, a unity gain cutoff frequency (f_m) of 82 GHz and maximum frequency of oscillation (f_max) of 103 GHz were measured.