The β-(AlxGa1−x)2O3 alloy represents an emerging ultrawide bandgap semiconductor material for applications in high-power electronics and deep ultraviolet optoelectronics. The recent demonstrations of orientation-dependent epitaxial growth of high quality β-(AlxGa1−x)2O3 films have unlocked prospects for the development of ultrahigh frequency β-(AlxGa1−x)2O3/Ga2O3 based transistors with high-power tolerance. To control the electronic and optical properties of β-(AlxGa1−x)2O3/Ga2O3 heterostructure-based devices, an understanding of the band offsets between β-(AlxGa1−x)2O3 and β-Ga2O3 is crucial. However, there have been no systematic experimental studies on the evolution of the band offsets between differently oriented β-(AlxGa1−x)2O3/Ga2O3 heterointerfaces as a function of Al compositions. This work presents the valence and conduction band offsets at (010) and oriented β-(AlxGa1−x)2O3/Ga2O3 interfaces using x-ray photoelectron spectroscopy. β-(AlxGa1−x)2O3 films with x ≤ 0.35 and x ≤ 0.48 were grown by metalorganic chemical vapor deposition on (010) and oriented β-Ga2O3 substrates, respectively. The determined band offsets reveal the formation of a type-II (staggered) band alignment at (010) oriented β-(AlxGa1−x)2O3/Ga2O3 and a type-I (straddling) heterojunction between β-(AlxGa1−x)2O3 and β-Ga2O3. For both crystalline orientations, the valence and conduction band offsets are found to increase with increasing Al content with a much weaker variation in the valence band offsets as compared to the conduction band offsets. Among different orientations investigated, such as (010), , and (100), the largest conduction band offset occurs at a β-(AlxGa1−x)2O3/Ga2O3 interface with (100) orientation, providing opportunities for excellent electron confinement with a high-density two-dimensional electron gas. Results from this study on the tunable and orientation-dependent band offsets with the variation of the Al alloy fraction will provide guidance for the design of heterostructures in future β-(AlxGa1−x)2O3/Ga2O3 based devices.
Band offsets at metalorganic chemical vapor deposited β-(AlxGa1−x)2O3/β-Ga2O3 interfaces—Crystalline orientation dependence
A F M Anhar Uddin Bhuiyan, Zixuan Feng, Hsien-Lien Huang, Lingyu Meng, Jinwoo Hwang, Hongping Zhao; Band offsets at metalorganic chemical vapor deposited β-(AlxGa1−x)2O3/β-Ga2O3 interfaces—Crystalline orientation dependence. J. Vac. Sci. Technol. A 1 December 2021; 39 (6): 063207. https://doi.org/10.1116/6.0001260
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