Crystal orientation dictated epitaxy of ultrawide-bandgap 5.4- to 8.6-eV α-(AlGa)2O3 on m-plane sapphire

• Published in: Science advances Vol. 7; no. 2
• Main Authors: Jinno, Riena, Chang, Celesta S, Onuma, Takeyoshi, Cho, Yongjin, Ho, Shao-Ting, Rowe, Derek, Cao, Michael C, Lee, Kevin, Protasenko, Vladimir, Schlom, Darrell G, Muller, David A, Xing, Huili G, Jena, Debdeep
• Format: Journal Article
• Language: English
• Published: American Association for the Advancement of Science 08.01.2021
• Subjects: Engineering; SciAdv r-articles
• ISSN: 2375-2548
• DOI: 10.1126/sciadv.abd5891

Crystalline oxides spanning very broad 5.4- to 8.6-eV bandgaps are successfully grown on sapphire by MBE. Ultrawide-bandgap semiconductors are ushering in the next generation of high-power electronics. The correct crystal orientation can make or break successful epitaxy of such semiconductors. Here, it is found that single-crystalline layers of α-(AlGa) 2 O 3 alloys spanning bandgaps of 5.4 to 8.6 eV can be grown by molecular beam epitaxy. The key step is found to be the use of m-plane sapphire crystal. The phase transition of the epitaxial layers from the α- to the narrower bandgap β-phase is catalyzed by the c-plane of the crystal. Because the c-plane is orthogonal to the growth front of the m-plane surface of the crystal, the narrower bandgap pathways are eliminated, revealing a route to much wider bandgap materials with structural purity. The resulting energy bandgaps of the epitaxial layers span a broad range, heralding the successful epitaxial stabilization of the largest bandgap materials family to date.