Study on electronic properties of diamond/SiNx-coated AlGaN/GaN high electron mobility transistors operating up to 500 °C

• Published in: Diamond and related materials 2018-10, Vol.89, p.266-272
• Main Authors: Babchenko, Oleg, Vanko, Gabriel, Gerboc, Michal, Ižák, Tibor, Vojs, Marian, Lalinský, Tibor, Kromka, Alexander
• Format: Article
• Language: English
• Subjects: AlGaN/GaN heterostructure; Diamond film; Electronic properties; High electron mobility transistor; High temperature operation; Hybrid device
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/j.diamond.2018.09.014

We report on the research related to integration and characterization of AlGaN/GaN heterostructure-based circular high electron mobility transistors (c-HEMTs) with diamond thin films. Prior to diamond deposition the transistors were coated by thin SiNx layer in order to protect AlGaN/GaN heterostructure from deposition process impact. The diamond thin film was selectively grown on the top of SiNx-coated c-HEMTs using low-pressure low-temperature microwave plasma deposition equipment with substrate table 20 × 30 cm2 from C/O/H gas mixture. We demonstrate the functionality of the diamond/SiNx-coated and the SiNx-coated AlGaN/GaN-based c-HEMTs in the temperature range from room temperature to 500 °C. The electrical measurements revealed increase of c-HEMTs' leakage currents at reversed gate voltages after diamond deposition, although the transistors remained operable in the tested temperature range. The increase of gate leakage currents and thus more negative pinch-off voltages were attributed to hydrogen penetrated towards AlGaN/GaN interface during the 60 h deposition process despite the SiNx protection. The influence of temperature rise on electronic properties of the diamond/SiNx-coated and the SiNx-coated AlGaN/GaN-based c-HEMTs is discussed. [Display omitted] •Diamond film is selectively grown on AlGaN/GaN heterostructure based circular HEMTs.•Intermediate SiNx layer protection was used in the low-pressure low-temperature CVD.•Diamond-covered c-HEMTs were capable to operate from room temperature to 500 °C.•The positive effect of diamond is more significant at high bias load of VGS.•The heat sink role of diamond cover is weakened at temperatures above 300 °C.