Comparative study of E- and D-mode InAlN/AlN/GaN HEMTs with fT near 200 GHz

We report on the 172/180 GHz (f
T
/f
max
) E-mode InAlN/AlN/GaN HEMTs with a recess-etched gate footprint of 33 nm. To develop further scaling strategies [1], comparative studies were carried out on E- and D-mode HEMTs with f
T
near 200 GHz at both room (RT) and cryogenic temperatures (LT). Delay component analysis indicates that the speed of the E-mode device is dominated by parasitic delays, and that the electron velocity in the E-mode is about 2/3 of that in D-mode, most likely steming from mobility degradation during gate recess etch.