High-Performance AlN/GaN MISHEMTs on Si With In-Situ SiN Enhanced Ohmic Contacts for Mobile mm-Wave Front-End Applications

In this letter, we demonstrated an AlN/GaN metal-insulator-semiconductor high electron mobility transistor (MISHEMT) on a Si substrate with in-situ SiN as gate dielectric with excellent mm-wave performance at low supply voltages. Benefited from the thin in-situ SiN, a low ohmic contact resistanceR Cof0.2 Ω · mmwas obtained. The device with a T-shape gate featuring 80 nm gate foot length (L G) and 620 nm total gate metal thickness shows a maximum drain current (I D) of 1.95 A/mm, a peak transconductance (g ₘₘₐₓ) of 500 mS/mm, and a cut-off frequency/a maximum oscillation frequency (f T/f ₘₐₓ) of 165/255 GHz. To the best of our knowledge, thef Tandf ₘₐₓare the highest among the reported AlN/GaN transistors on Si substrates. 28 GHz load-pull measurements at low drain voltages of 3.5/5/6 V show maximum output power densities (P out,max) of 0.36/0.73/1.04 W/mm and peak power-added efficiencies (PAE) of 40%/42%/43%, respectively. These excellent results show that AlN/GaN HEMTs on Si have a great potential for power amplifiers (PAs) in mobile mm-wave front-end applications.