High performance ultra-thin quaternary InAlGaN barrier HEMTs with fT > 260 GHz

We fabricated the depletion-mode high-electron mobility transistors (HEMTs) based on a quaternary barrier InAlGaN/AlN/GaN heterostructure on SiC substrate. A 60-nm rectangular-shape gate was defined through e-beam lithography and subsequent Ni/Au (20 nm/80 nm) metal evaporation. Our device shows a high DC drain current density of 2.5 A/mm, a low on-resistance Ron of 0.94 Ω•mm in the linear region, a high peak extrinsic transconductance of 0.97 S/mm, and a high current-gain cutoff frequency of 261 GHz. Besides, a high fT • Lg product of 15.7 GHz•μm was achieved. The drain-induced barrier lowering (DIBL) is calculated to be 200 mV/V at ID=1 mA/mm, implying moderate short-channel effect in our device. To our knowledge, this is among the best fT performance for GaN-based HEMTs with a gate length of around 60 nm.