Crystalline interlayers for reducing the effective thermal boundary resistance in GaN-on-diamond

Field, D. E., Cuenca, J. A., Smith, M., Fairclough, S. M., Massabuau, F. C.-P., Pomeroy, J. W., Williams, O., Oliver, R. A., Thayne, I. and Kuball, M. (2020) Crystalline interlayers for reducing the effective thermal boundary resistance in GaN-on-diamond. ACS Applied Materials and Interfaces, 12(48), pp. 54138-54145. (doi: 10.1021/acsami.0c10129) (PMID:33196180)

Abstract

Integrating diamond with GaN high electron mobility transistors (HEMTs) improves thermal management, ultimately increasing the reliability and performance of high-power high-frequency radio frequency amplifiers. Conventionally, an amorphous interlayer is used before growing polycrystalline diamond onto GaN in these devices. This layer contributes significantly to the effective thermal boundary resistance (TBR ) between the GaN HEMT and the diamond, reducing the benefit of the diamond heat spreader. Replacing the amorphous interlayer with a higher thermal conductivity crystalline material would reduce TBR and help to enable the full potential of GaN-on-diamond devices. In this work, a crystalline Al Ga N interlayer has been integrated into a GaN/AlGaN HEMT device epitaxy. Two samples were studied, one with diamond grown directly on the AlGaN interlayer and another incorporating a thin crystalline SiC layer between AlGaN and diamond. The TBR , measured using transient thermoreflectance, was improved for the sample with SiC (30 ± 5 m K GW ) compared to the sample without (107 ± 44 m K GW ). The reduced TBR is thought to arise from improved adhesion between SiC and the diamond compared to the diamond directly on AlGaN because of an increased propensity for carbide bond formation between SiC and the diamond. The stronger carbide bonds aid transmission of phonons across the interface, improving heat transport.

• Item Type: Articles
• Additional Information: The authors would like to acknowledge financial support from the Engineering and Physical Sciences Research Council (EPSRC) under the program Grant GaN-DaME (grant no. EP/P00945X/1). D.Field’s PhD studentship is co-funded by the EPSRC Centre for Doctoral Training in Diamond Science & Technology (EP/L015315/1) and Element-Six Technologies.
• Keywords: AlGaN, AlN, GaN, GaN-on-diamond, SiC, diamond, thermal boundary resistance, thermal management.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Smith, Dr Matthew and Thayne, Prof Iain
• Authors: Field, D. E., Cuenca, J. A., Smith, M., Fairclough, S. M., Massabuau, F. C.-P., Pomeroy, J. W., Williams, O., Oliver, R. A., Thayne, I., and Kuball, M.
• College/School: College of Science and Engineering > School of Engineering
• Journal Name: ACS Applied Materials and Interfaces
• Publisher: American Chemical Society
• ISSN: 1944-8244
• ISSN (Online): 1944-8252
• Published Online: 16 November 2020