Al Coordination and Ga Interstitial Stability in a β-(Al0.2Ga0.8)2O3 Thin Film

Adrian E. Chmielewski, Ziling Deng, Daniel Duarte-Ruiz, Parivash Moradifar, Leixin Miao, Yuewei Zhang, Akhil Mauze, Caterina Cocchi, Wolfgang Windl, Nasim Alem

Research output: Contribution to journalArticlepeer-review

Abstract

Alloying Al2O3 with Ga2O3 to form β-(AlxGa1-x)2O3 opens the door to a large number of new possibilities for the fabrication of devices with tunable properties in many high-performance applications such as optoelectronics, sensing systems, and high-power electronics. Often, the properties of these devices are impacted by defects induced during the growth process. In this work, we uncover the crystal structure of a β-(Al0.2Ga0.8)2O3/β-Ga2O3 interface grown by molecular beam epitaxy. In particular, we determine Al coordination and the stability of Al and Ga interstitials and their effect on the electronic structure of the material by means of scanning transmission electron microscopy combined with density functional theory. Al atoms can substitutionally occupy both octahedral and tetrahedral sites. The atomic structure of the β-(Al0.2Ga0.8)2O3/β-Ga2O3 interface additionally shows Al and Ga interstitials located between neighboring tetrahedrally coordinated cation sites, whose stability will depend on the number of surrounding Al atoms. The presence of Al atoms near interstitials leads to structural distortions in the lattice and creates interstitial-divacancy complexes that will eventually form deep-level states below the conduction band (Ec) at Ec −1.25 eV, Ec −1.68 eV, Ec −1.78 eV, Ec −1.83 eV, and Ec −1.86 eV for a Ga interstitial surrounded by zero, one, two, three, and four Al atoms, respectively. These findings bring new insight toward the fabrication of tunable β-(AlxGa1-x)2O3 heterostructure-based devices with controlled electronic properties.

Original languageEnglish (US)
Pages (from-to)8601-8608
Number of pages8
JournalACS Applied Materials and Interfaces
Volume15
Issue number6
DOIs
StatePublished - Feb 15 2023

All Science Journal Classification (ASJC) codes

  • General Materials Science

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