IEEE TRANSACTIONS ON ELECTRON DEVICES, vol.64, no.8, pp.3114-3119, 2017 (SCI-Expanded)
We report on the small-signal high frequency characteristics of highly scaled graded AlGaN channel polarization-doped field-effect transistors (PolFETs) that show constant current gain cutoff frequency (f(T)) and maximum oscillation frequency (f(max)) profiles as a function of current density or gate bias. The device design includes upward and downward Al composition grading to induce a distributed 3-D charge profile, and eliminate abrupt heterojunction band offsets to achieve nonalloyedohmic contacts with low resistance. The highest extrinsic f(T) of 52 GHz and fmax of 67 GHz weremeasured at V-GS = -1.5 V andVDS = 9 V, and constant fT and fmax over wide input voltage (VGS) and output current range (IDS) were achieved.