AlN/GaN MOS-HEMTs With Thermally Grown [Formula Omitted] Passivation

• Published in: IEEE transactions on electron devices Vol. 58; no. 5; p. 1418
• Main Authors: Taking, Sanna, MacFarlane, Douglas, Wasige, Edward
• Format: Journal Article
• Language: English
• Published: New York The Institute of Electrical and Electronics Engineers, Inc. (IEEE) 01.05.2011
• Subjects: Radio frequency; Studies
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2011.2114665

This paper reports on the processing and characterization of AlN/GaN metal-oxide-semiconductor high-electron mobility transistors (MOS-HEMTs). The devices employ thermally grown [Formula Omitted] as a gate dielectric and surface protection and passivation, which is an approach that provides an opportunity to define the ohmic contact areas by wet etching of Al (and optimization of this processing step) prior to the formation of [Formula Omitted] and ohmic metal deposition. The devices also employ a new process technique that significantly suppresses leakage currents on the mesa sidewalls. Fabricated devices exhibited good direct current and radio frequency performance. A high peak current, i.e., [Formula Omitted]1.5 A/mm, at [Formula Omitted] and a current-gain cutoff frequency [Formula Omitted] and maximum oscillation frequency [Formula Omitted] of 50 and 40 GHz, respectively, were obtained for a device with 0.2-[Formula Omitted] gate length and 100- [Formula Omitted] gate width. Additionally, a robust method for the extraction of the small-signal equivalent circuit suitable for process optimization is described. It relies on intimate process knowledge and device geometry to determine equivalent circuit elements of the fabricated AlN/GaN MOS-HEMTs.