Power Performance at 40 GHz on Quaternary Barrier InAlGaN/GaN HEMT

Depletion-mode high-electron mobility transistors (HEMTs) based on a quaternary barrier In_0.11Al_0.72Ga_0.17N/GaN heterostructure on sapphire substrate are fabricated and characterized. This structure shows a very high Hall electron mobility of 2200 cm²/V·s, which is the highest value ever reported on In-containing GaN-based HEMTs. For T-shaped gate transistor with a gate length of 75 nm, current gain (f_t) and power gain (f_max) cutoff frequencies of 113 and 200 GHz are extracted from S-parameter measurements, respectively. Nonlinear characterization of a T-shaped gate device with a gate length of 225 nm gives an output power density of 2 W/mm at 40 GHz. These results clearly demonstrate the capabilities of such quaternary barrier-based devices.