Nanocrystalline diamond capped AlGaN/GaN high electron mobility transistors via a sacrificial gate process

• Published in: Physica status solidi. A, Applications and materials science Vol. 213; no. 4; pp. 893 - 897
• Main Authors: Tadjer, Marko J., Anderson, Travis J., Feygelson, Tatyana I., Hobart, Karl D., Hite, Jennifer K., Koehler, Andrew D., Wheeler, Virginia D., Pate, Bradford B., Eddy Jr, Charles R., Kub, Fritz J.
• Format: Journal Article
• Language: English
• Published: Weinheim Blackwell Publishing Ltd 01.04.2016; Wiley Subscription Services, Inc
• Subjects: AlGaN; Aluminum gallium nitrides; Capping; Diamonds; Drains; Etching; Gallium nitrides; GaN; Gates; High electron mobility transistors; nanocrystalline materials; Plasma etching; self-heating; Transistors
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.201532570

Top‐side integration of nanocrystalline diamond films in the fabrication sequence of AlGaN/GaN high electron mobility transistors is demonstrated. Reliable oxygen plasma etching of the diamond capping layer, required for a diamond‐before‐gate process, was implemented by using a sacrificial SiN “dummy” gate. Hall characterization showed minimal (∼6%) reduction in sheet carrier density and commensurate increase in sheet resistance, while maintaining mobility and on‐state drain current density. Off‐state drain current and threshold voltage were increased, likely by fluorination of the AlGaN surface after removal of the sacrificial gate, even though a 20 nm thick Al2O3 layer was used as a SF6‐plasma etch stop. Pulsed IDS and on‐resistance were improved, indicating that a 10 nm SiN/500 nm NCD could offer improved AlGaN surface passivation compared to a more conventional 100 nm thick PECVD SiN film.