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1. Orientation-dependent band offsets at MOCVD grown β-(AlxGa1−x)2O3/β-Ga2O3 heterointerfaces

   A F M A. U. Bhuiyan, Z. Feng (June 2021, 2021 EMC)

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2. MOCVD growth of (010) β-(AlxGa1−x)2O3 thin films

   https://doi.org/10.1557/s43578-021-00354-8  

   Bhuiyan, A F; Feng, Zixuan; Meng, Lingyu; Zhao, Hongping (December 2021, Journal of Materials Research)
3. Metalorganic chemical vapor deposition in situ etching of β-Ga2O3 and β-(AlxGa1−x)2O3

   https://doi.org/10.1116/6.0004620  

   Meng, Lingyu; Thirupakuzi_Vangipuram, Vijay Gopal; Yu, Dong Su; Hu, Chenxi; Zhao, Hongping (September 2025, Journal of Vacuum Science & Technology B)

   This study presents a comprehensive analysis of the etching effects on β-Ga2O3 using two methods: H2_N2 (a mixture of hydrogen and nitrogen) etching and triethylgallium (TEGa) in situ etching performed in a metal-organic chemical vapor deposition system. By employing a mix of H2 and N2 gases at varying chamber pressures and maintaining a constant etching temperature of 750 °C, we investigated the etching dynamics across three different β-Ga2O3 orientations: (010), (001), and (2¯01). Field emission scanning electron microscopy analysis showed that the etching behavior of β-Ga2O3 depends on the crystal orientation, with the (010) orientation showing notably uniform and smooth surfaces, indicating its suitability for vertical device applications. High-aspect-ratio β-Ga2O3 fin arrays were fabricated on (010) substrates using H2_N2 etching, yielding fin structures with widths of 2 μm and depths of 3.1 μm, along with smooth and well-defined sidewalls. The etching process achieved exceptionally high etch rates (>18 μm/h) with a strong dependence on pressure and sidewall orientation, revealing the trade-off between etch depth and surface smoothness. Separately, TEGa in situ etching was investigated as an alternative etching technique for both β-Ga2O3 and β-(AlxGa1−x)2O3 films. The results revealed that the (010) orientation exhibited relatively high etching rates while maintaining smoother sidewalls and top surfaces, making it favorable for device processing. In contrast, the (001) orientation showed strong resistance to TEGa etching. Furthermore, Al-incorporated β-(AlxGa1−x)2O3 films showed substantially lower etch rates compared to pure β-Ga2O3, suggesting their potential use as an effective etch-stop layer in advanced device fabrication. 

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4. Electrical and structural characterization of in situ MOCVD Al2O3/β-Ga2O3 and Al2O3/β-(AlxGa1−x)2O3 MOSCAPs

   https://doi.org/10.1063/5.0256525  

   Bhuiyan, A_F_M_Anhar Uddin; Meng, Lingyu; Yu, Dong Su; Dhara, Sushovan; Huang, Hsien-Lien; Vangipuram, Vijay_Gopal Thirupakuzi; Hwang, Jinwoo; Rajan, Siddharth; Zhao, Hongping (May 2025, Journal of Applied Physics)

   This study investigates the electrical and structural properties of metal–oxide–semiconductor capacitors (MOSCAPs) with in situ metal-organic chemical vapor deposition-grown Al2O3 dielectrics deposited at varying temperatures on (010) β-Ga2O3 and β-(AlxGa1−x)2O3 films with different Al compositions. The Al2O3/β-Ga2O3 MOSCAPs exhibited a strong dependence of electrical properties on Al2O3 deposition temperature. At 900 °C, reduced voltage hysteresis (∼0.3 V) with improved reverse breakdown voltage (74.5 V) was observed, corresponding to breakdown fields of 5.01 MV/cm in Al2O3 and 4.11 MV/cm in β-Ga2O3 under reverse bias. In contrast, 650 °C deposition temperature resulted in higher voltage hysteresis (∼3.44 V) and lower reverse breakdown voltage (38.8 V) with breakdown fields of 3.69 and 2.87 MV/cm in Al2O3 and β-Ga2O3, respectively, but exhibited impressive forward breakdown field, increasing from 5.62 MV/cm at 900 °C to 7.25 MV/cm at 650 °C. High-resolution scanning transmission electron microscopy (STEM) revealed improved crystallinity and sharper interfaces at 900 °C, contributing to enhanced reverse breakdown performance. For Al2O3/β-(AlxGa1−x)2O3 MOSCAPs, increasing Al composition (x) from 5.5% to 9.2% reduced net carrier concentration and improved reverse breakdown field contributions from 2.55 to 2.90 MV/cm in β-(AlxGa1−x)2O3 and 2.41 to 3.13 MV/cm in Al2O3. The electric field in Al2O3 dielectric under forward bias breakdown also improved from 5.0 to 5.4 MV/cm as Al composition increased from 5.5% to 9.2%. The STEM imaging confirmed the compositional homogeneity and excellent stoichiometry of both Al2O3 and β-(AlxGa1−x)2O3 layers. These findings demonstrate the robust electrical performance, high breakdown fields, and excellent structural quality of Al2O3/β-Ga2O3 and Al2O3/β-(AlxGa1−x)2O3 MOSCAPs, highlighting their potential for high-power electronic applications. 

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5. Effective electronic band structure of monoclinic β−(AlxGa1−x)2O3 alloy semiconductor

   https://doi.org/10.1063/5.0134155  

   Sharma, Ankit; Singisetti, Uttam (January 2023, AIP Advances)

   In this article, the electronic band structure of a β−(AlxGa1−x)2O3 alloy system is calculated, with β−Ga2O3 as the bulk crystal. The technique of band unfolding is implemented to obtain an effective band structure for aluminum fractions varying between 12.5% and 62.5% with respect to gallium atoms. A 160-atom supercell is used to model the disordered system that is generated using the technique of special quasi-random structures, which mimics the site correlation of a truly random alloy by reducing the number of candidate structures that arise due to the large number of permutations possible for alloy occupation sites. The impact of the disorder is then evaluated on the electron effective mass and bandgap, which is calculated under the generalized gradient approximation. 

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