GaN DHFETs Having 48% Power Added Efficiency and 57% Drain Efficiency at $V$ -Band

We report the state-of-the-art V-band power performance of a scaled 40-nm gate length Al
_0.23
Ga
_0.77
N/AlN/GaN/Al
_0.08
Ga
_0.92
N double heterojunction field effect transistor (DHFET). The 200 μm (4 × 50 μm) wide GaN DHFETs pre-matched for V-band (57-64 GHz) have demonstrated an output power of 376 mW (1.88 W/mm) with 48% power-added efficiency (PAE), 57% drain efficiency, and more than 8 dB of associated gain measured at a frequency of 59 GHz. These results represent to the best of our knowledge the best combination of power and PAE reported to date at this frequency for a solid-state device. These results were achieved through optimization of the GaN heterostructure, which incorporates a low aluminum content back-barrier for electron confinement through polarization effects, a vertically scaled Al
_0.23
Ga
_0.77
N/AlN gate barrier stack for minimization of short-channel effects, and a selective n+ GaN ohmic re-growth process by molecular beam epitaxy for reduction of parasitic resistance.