Graded AlGaN Channel Transistors for Improved Current and Power Gain Linearity

Bajaj S., Yang Z., Akyol F. , PARK P. S. , Zhang Y., Price A. L. , ...More

IEEE TRANSACTIONS ON ELECTRON DEVICES, vol.64, no.8, pp.3114-3119, 2017 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 64 Issue: 8
  • Publication Date: 2017
  • Doi Number: 10.1109/ted.2017.2713784
  • Page Numbers: pp.3114-3119
  • Keywords: Graded AlGaN, constant f(T), gain linearity, GaN, graded AlGaN, high-electron-mobility transistor (HEMT), polarization-doped field-effect transistor (PolFET), ELECTRON-MOBILITY TRANSISTORS, MOLECULAR-BEAM EPITAXY, OHMIC CONTACTS, HEMTS, F(T)


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.