Room-temperature bonding of GaN and diamond via a SiC layer

Abstract

A GaN-on-diamond structure is the most promising candidate for improving the heat dissipation efficiency of GaN-based power devices. Room-temperature bonding of GaN and diamond is an efficient technique for fabricating this structure. However, it is extremely difficult to polish diamond to an average roughness (Ra) below 0.4 nm, especially for polycrystalline diamond. In this work, Room-temperature bonding of GaN and rough-surfaced diamond with a SiC layer was successfully achieved by a surface-activated bonding (SAB) method. The diamond surface’s initial Ra value was 0.768 nm, but after deposition of the SiC layer, the Ra decreased to 0.365 nm. The SiC layer formed at the as-bonded GaN/diamond interface was amorphous, with a thickness of about 7 nm. After annealing at 1000-°C, the amorphous SiC layer became polycrystalline, and its thickness increased to approximately 12 nm. These results indicate that the deposition of a SiC layer on diamond can efficiently lower the diamond surface’s roughness and thus facilitate room-temperature bonding.

Keywords:

• GaN/diamond interface
• SiC layer
• heat dissipation
• thermal management
• surface-activated bonding

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the ‘Research and development of high thermal stability interface by direct bonding of diamond’ project in the Feasibility Study Program of New Energy and Industrial Technology Development Organization (NEDO) (Contract Number: 19101240-0), JSPS KAKENHI Grant Number JP20K04581, and the Osaka City University (OCU) Strategic Research Grant 2020 for top basic research. The fabrication of the TEM samples was performed at The Oarai Center and at the Laboratory of Alpha-Ray Emitters in IMR under the Inter-University Cooperative Research in IMR of Tohoku University (NO. 202112-IRKMA-0016). The observation of the TEM samples was supported by Kyoto University Nano Technology Hub in the ‘Nanotechnology Platform Project’ sponsored by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.