GaN SLCFET Technology for Next Generation mmW Systems, Demonstrating P out of 10.87 W/mm With 43% PAE at 94 GHz

We report on the development of the super-lattice castellated field effect transistor (SLCFET) technology as a candidate for the next generation of mmW and $W$ -band systems, leveraging the high carrier density and a high degree of charge control offered by this device topology for mmW and $W$ -band power amplification. The SLCFET is built using a superlattice of stacked AlGaN/gallium nitride (GaN) heterostructures that are etched into nanoribbons between epitaxial regrown n+ GaN source and drain contacts and controlled with a 100 nm length T-gate that electrostatically actuates the stacked channels from the sidewalls. The $2\times 20\,\,\mu \text{m}$ amplifier cells of SLCFET devices were measured using load–pull at 94 GHz using a 12-V bias, demonstrating amplifier output power densities of 10.87 W/mm with 43% power added efficiency (PAE) at peak power and a maximum linear gain of 5.4 dB. The SLCFET amplifier process attains this power density due to its extremely high current density, with an IMAX of 4.8 A/mm, along with its minimal dispersion, with current collapse measured using pulsed $I$ – $V$ at < 7%. The SLCFET technology, with its previously demonstrated world-class RF switch performance and now record $W$ -band amplifier performance, is ideal for use in next-generation mmW and $W$ -band systems.