High frequency N-polar GaN planar MIS-HEMTs on sapphire with high breakdown and low dispersion

N-polar planar GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) grown by metal-organic chemical vapor deposition on sapphire substrate with a high combination of power cutoff frequency (f
max
) and three-terminal breakdown voltage (BV
DS
) as well as a decent DC-to-RF dispersion control are demonstrated. Compared to previously reported N-polar planar HEMTs, devices presented in this letter not only maintain comparable f
max
/BV
DS
of 221 GHz/116 V, but also exhibit a mitigation of drain current collapse and ON-resistance dispersion. In addition, a higher output power of 5.43 W/mm at the same V
DS,Q
= 25 V and a reduction of efficiency drop with increasing V
DS,Q
were achieved by load-pull measurements at 10 GHz.