60-nm GaN/AlGaN DH-HEMTs with 1.0 Ω·mm Ron, 2.0 A/mm Idmax, and 153 GHz fT

GaN-based HEMTs offer a unique combination of high electron velocity and high breakdown field making them the prime candidate for the highest performance millimeter-wave solid-state power amplifiers (PAs). Recently, we have demonstrated GaN MMIC PAs with an output power of 500 mW at W-band frequency range. The device high frequency performance has been significantly improved during the past y ears through vertical epitaxial scaling w ith double-hetero (DH) HEMT structures using an AlGaN back barrier and reduction of gate length (L_g) down to 30 nm. One of technical challenges for further device scaling is reduction of parasitic resistances. Various approaches including alloyed contact to an n⁺-GaN cap layer, ion implantation, and a multichannel structure were attempted. However, a resulting on-resistance (Ron) is typically larger than 1.6 Ω-mm. In this paper, we report on 60-nm gate GaN/Al_0.3Ga_0.7N DH-HEMTs with non-alloyed ohmic contacts and a very short gate recess of 100 nm in length, demonstrating an extremely low R_on of 1.0 Ω-mm, a very high maximum drain current (I_dmax) of 2.0 A/mm, and a cutoff frequency (f_T) of 153 GHz.