First Demonstration of Four-Finger N-polar GaN HEMT Exhibiting Record 712-mW Output Power With 31.7% PAE at 94 GHz

In this letter, the first four-finger (4 $\times25\,\,\mu \text{m}$ ) N-polar GaN high-electron-mobility transistor (HEMT) with an outstanding large signal performance of 712-mW (7.1 W/mm) with 31.7% power-added efficiency (PAE) is demonstrated at 94 GHz. To the best of our knowledge, this is a record output power from a single device cell in any semiconductor technology at $W$ -band. An equivalent two-finger device (2 $\times37.5\,\,\mu \text{m}$ ) exhibits 6.9 W/mm with 30.6% PAE, demonstrating no degradation of either power density or efficiency with increased number of fingers and gate width. Additionally, the design considerations for multifinger devices are presented with the simulations of airbridge parasitics using COMSOL Multiphysics and Ansys high-frequency structure simulator (HFSS), along with the exploration of the design space in number and width of fingers for the best gain performance for >1 W. Simultaneous high-output power with high efficiency (>30%) shows the great potential of multifinger N-polar GaN HEMT technology for the state-of-the-art $W$ -band power amplifiers.