Graded AlGaN Channel Transistors for Improved Current and Power Gain Linearity

• Published in: IEEE transactions on electron devices Vol. 64; no. 8; pp. 3114 - 3119
• Main Authors: Bajaj, Sanyam, Zhichao Yang, Akyol, Fatih, Pil Sung Park, Yuewei Zhang, Price, Aimee L., Krishnamoorthy, Sriram, Meyer, David J., Rajan, Siddharth
• Format: Journal Article
• Language: English
• Published: IEEE 01.08.2017
• Subjects: Aluminum gallium nitride; constant f<italic xmlns:ali="http://www.niso.org/schemas/ali/1.0/" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">T; Current measurement; gain linearity; GaN; Graded AlGaN; HEMTs; high-electron-mobility transistor (HEMT); Logic gates; polarization-doped field-effect transistor (PolFET); Transconductance; Wide band gap semiconductors
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2017.2713784

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 nonalloyed ohmic contacts with low resistance. The highest extrinsic f T of 52 GHz and f ma x of 67 GHz were measured at V GS = -1.5 V and V DS = 9 V, and constant f T and f max over wide input voltage (V GS ) and output current range (IDS) were achieved.