We have grown a single-crystal beryllium oxide (BeO) thin film on a gallium nitride (GaN) substrate by atomic-layer deposition (ALD) for the first time. BeO has a higher thermal conductivity, bandgap energy, and dielectric constant than SiO2. As an electrical insulator, diamond is the only material on earth whose thermal conductivity exceeds that of BeO. Despite these advantages, there is no chemical-vapor-deposition technique for BeO-thin-film deposition, and thus, it is not used in nanoscale-semiconductor-device processing. In this study, the BeO thin films grown on a GaN substrate with a single crystal showed excellent interface and thermal stability. Transmission electron microscopy showed clear diffraction patterns, and the Raman shifts associated with soft phonon modes verified the high thermal conductivity. The X-ray scan confirmed the out-of-plane single-crystal growth direction and the in-plane, 6-fold, symmetrical wurtzite structure. Single-crystalline BeO was grown on GaN despite the large lattice mismatch, which suggested a model that accommodated the strain of hexagonal-on-hexagonal epitaxy with 5/6 and 6/7 domain matching. BeO has a good dielectric constant and good thermal conductivity, bandgap energy, and single-crystal characteristics, so it is suitable for the gate dielectric of power semiconductor devices. The capacitance-voltage (C-V) results of BeO on a GaN-metal-oxide semiconductor exhibited low frequency dispersion, hysteresis, and interface-defect density.
Bibliographical noteFunding Information:
This research was supported by the Ministry of Science and ICT (MSIT), Korea, under the ICT Consilience Creative program (IITP-2017-2017-0-01015) supervised by the IITP (Institute for Information & Communications Technology Promotion). It was also supported by the Future Semiconductor Device Technology Development Program (10044735, 10048536), which is funded by the Ministry of Trade, Industry & Energy and the Korea Semiconductor Research Consortium. We are indebted to Gong Gu and Lifen Wang for their insightful discussions and suggestions. J.H.Y., E.S.L., and C.W.B. are grateful to the Institute for Basic Science (IBS-R019-D1) as well as to the BK21 Plus Program funded by the Ministry of Education and the National Research Foundation of Korea for their support. The work at the University of Houston was supported by the IT R&D program of MOTIE/KEIT (Grant No. 10048933, Development of epitaxial structure design and epitaxial growth system for high- voltage power semiconductors). J.H.R. also acknowledges partial support from the Texas Center for Superconductivity at the University of Houston (TcSUH).
All Science Journal Classification (ASJC) codes
- Materials Science(all)