360 GHz f MAX Graded-Channel AlGaN/GaN HEMTs for mmW Low-Noise Applications

We report scaled, graded-channel AlGaN/GaN HEMTs with an extrinsic f _T and f _MAX of 170 GHz and 363 GHz, which is the highest in emerging graded-channel GaN HEMTs. At 50-nm gate length, the f _T *Lg of 8.5 GHz $\ast \mu \text{m}$ is comparable to that of conventional scaled AlGaN/GaN HEMTs fabricated together. At low DC power, the scaled graded-channel AlGaN/GaN HEMTs show a higher f _MAX than the scaled AlGaN/GaN HEMT with the same gate length. The devices also exhibit a 2 dB improvement in gain at low DC bias, and the measured minimum noise figure was as low as 0.5 dB at 30 GHz. This is comparable to state-of-the-art device noise figure from a 20-nm gate length AlGaN/GaN HEMT. The combination of improved f _T , f _MAX , and minimum noise figure at low DC power for the graded-channel AlGaN/GaN HEMTs shows great promise for ultra-low-power, low-noise amplifiers.