News from Nanotechjapan

加工技術

Successful metalorganic vapor phase epitaxy of β-gallium oxide crystals ---Accelerating the realization of a carbon-free society through next-generation power de-vices---

 On April 1, 2021, Tokyo University of Agriculture and Technology (TUAT), Gas-Phase Growth Ltd., and Taiyo Nippon Sanso Corporation jointly announced that the research group led by Professor Yoshinao Kumagai of TUAT succeeded in demonstrating the growth of high-purity beta-gallium oxide(β-Ga2O3)crystals by metalorganic vapor phase epitaxy (MOVPE) method. Details were published in Japanese Journal of Applied Physics (JJAP)*.

 Realization of a carbon-free society is a global concern and an efficient power semiconductor devices will be a key component in power control systems to reduce carbon emission. Ultimate performance of power devices depends on the material properties. β-Ga2O3 is expected to have a large dielectric breakdown field of ca. 8 MV cm-1 from a large bandgap of 4.4-4.9 eV and lower power loss as compared to current material Si by 1/3000. Most fabrication processes of power devices utilize epitaxial crystal growth, however, MOVPE of β-Ga2O3 has never been examined because of high oxygen reactivity against organometallic compounds.

 The research group carried out thermodynamic analysis of MOVPE using triethylgallium (TEG) and oxygen (O2) precursors. The analysis revealed that the use of high growth temperatures and high input VI(O)/III(Ga) ratios is essential for β-Ga2O3 growth and the use of an inert gas as the carrier gas was also necessary. Based on these results, a smooth β-Ga2O3 layer with bandgap of 4.84 eV was successfully grown on a c-plane sapphire substrate at 900℃ with a growth rate of 1.4μm h-1 at an input VI/III ratio of 100.

 This success will contribute to accelerate the realization of a carbon-free society through the devel-opment of superior power devices using the next generation material β-Ga2O3.
 
*Ken Goto, Kazutada Ikenaga, Nami Tanaka, Masato Ishikawa, Hideaki Machida, and Yoshinao Kumagai, "Thermodynamic and experimental studies of β-Ga2O3 growth by metalorganic vapor phase epitaxy", Japanese Journal of Applied Physics, 2021, Vol. 60, No. 4, p. 045505, DOI: 10.35848/1347-4065/abec9d; Published 29 March 2021