Impact of selective thermal etching in mixed H 2 /NH 3 atmosphere on crystal quality of AlGaN/GaN heterostructures

• Published in: Japanese Journal of Applied Physics 2021-05, Vol.60 (SB), p.SBBK11
• Main Authors: Yoshiya, Yuki, Hoshi, Takuya, Sugiyama, Hiroki, Matsuzaki, Hideaki
• Format: Article
• Language: English
• ISSN: 0021-4922; 1347-4065
• DOI: 10.35848/1347-4065/abdf72

We investigated the impact of selective thermal etching in a mixed hydrogen and ammonia atmosphere on the crystal quality and electrical characteristics of Ga- and N-polar AlGaN/GaN heterostructures. It was revealed that the etching rate of N-polar GaN is lower than that of Ga-polar GaN under our experimental conditions, and they showed a similar dependence on process temperature with almost the same activation energies. We demonstrated the use of a thin AlGaN layer as a selective etching stopper for both Ga- and N-polarity. The AlGaN stoppers exhibited a smooth surface after etching the GaN layer above them. As for the electrical characteristics, there was no significant degradation in the mobility of the two-dimensional electron gas. The results indicate that selective thermal etching is a promising technique for device fabrication and is especially suitable for precise GaN layer removal when GaN-based devices are fabricated with an epitaxial layer transfer technique.