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1. Thermal Conductivity of β-Phase Ga 2 O 3 and (Al x Ga 1– x ) 2 O 3 Heteroepitaxial Thin Films

   https://doi.org/10.1021/acsami.1c08506  

   Song, Yiwen ; Ranga, Praneeth ; Zhang, Yingying ; Feng, Zixuan ; Huang, Hsien-Lien ; Santia, Marco D. ; Badescu, Stefan C. ; Gonzalez-Valle, C. Ulises ; Perez, Carlos ; Ferri, Kevin ; et al ( August 2021 , ACS Applied Materials & Interfaces)
2. MOCVD epitaxy of β -(Al x Ga 1−x ) 2 O 3 thin films on (010) Ga 2 O 3 substrates and N-type doping

   https://doi.org/10.1063/1.5123495  

   Anhar Uddin Bhuiyan, A F ; Feng, Zixuan ; Johnson, Jared M. ; Chen, Zhaoying ; Huang, Hsien-Lien ; Hwang, Jinwoo ; Zhao, Hongping ( September 2019 , Applied Physics Letters)
3. Epitaxial growth of Mg x Ca 1−x O on 4H–SiC(0001) and β-Ga 2 O 3 wide band gap semiconductors with atomic layer deposition

   https://doi.org/10.1557/jmr.2019.376  

   Lou, Xiabing ; Gong, Xian ; Kim, Sang Bok ; Gordon, Roy G. ( April 2020 , Journal of Materials Research)

   SiC and Ga 2 O 3 are promising wide band gap semiconductors for applications in power electronics because of their high breakdown electric field and normally off operation. However, lack of a suitable dielectric material that can provide high interfacial quality remains a problem. This can potentially lead to high leakage current and conducting loss. In this work, we present a novel atomic layer deposition process to grow epitaxially Mg x Ca 1− x O dielectric layers on 4H-SiC(0001) and β-Ga 2 O 3 $\left( {\bar 201} \right)$ substrates. By tuning the composition of Mg x Ca 1− x O toward the substrate lattice constant, better interfacial epitaxy can be achieved. The interfacial and epitaxy qualities were investigated and confirmed by cross-sectional transmission electron microscopy and X-ray diffraction studies. Mg 0.72 Ca 0.28 O film showed the highest epitaxy quality on 4H-SiC(0001) because of its closest lattice match with the substrate. Meanwhile, highly textured Mg 0.25 Ca 0.75 O films can be grown on β-Ga 2 O 3 $\left( {\bar 201} \right)$ with a preferred orientation of (111). 

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4. Dielectric function tensor (1.5 eV to 9.0 eV), anisotropy, and band to band transitions of monoclinic β -(Al x Ga 1– x ) 2 O 3 ( x ≤ 0.21) films

   https://doi.org/10.1063/1.5097780  

   Hilfiker, Matthew ; Kilic, Ufuk ; Mock, Alyssa ; Darakchieva, Vanya ; Knight, Sean ; Korlacki, Rafał ; Mauze, Akhil ; Zhang, Yuewei ; Speck, James ; Schubert, Mathias ( June 2019 , Applied Physics Letters)
5. In situ MOCVD growth and band offsets of Al 2 O 3 dielectric on β-Ga 2 O 3 and β-(Al x Ga 1−x ) 2 O 3 thin films

   https://doi.org/10.1063/5.0104433  

   Bhuiyan, A F ; Meng, Lingyu ; Huang, Hsien-Lien ; Hwang, Jinwoo ; Zhao, Hongping ( October 2022 , Journal of Applied Physics)

   The in situ metalorganic chemical vapor deposition (MOCVD) growth of Al 2 O 3 dielectrics on β-Ga 2 O 3 and β-(Al x Ga 1−x ) 2 O 3 films is investigated as a function of crystal orientations and Al compositions of β-(Al x Ga 1−x ) 2 O 3 films. The interface and film qualities of Al 2 O 3 dielectrics are evaluated by high-resolution x-ray diffraction and scanning transmission electron microscopy imaging, which indicate the growth of high-quality amorphous Al 2 O 3 dielectrics with abrupt interfaces on (010), (100), and [Formula: see text] oriented β-(Al x Ga 1−x ) 2 O 3 films. The surface stoichiometries of Al 2 O 3 deposited on all orientations of β-(Al x Ga 1−x ) 2 O 3 are found to be well maintained with a bandgap energy of 6.91 eV as evaluated by high-resolution x-ray photoelectron spectroscopy, which is consistent with the atomic layer deposited (ALD) Al 2 O 3 dielectrics. The evolution of band offsets at both in situ MOCVD and ex situ ALD deposited Al 2 O 3 /β-(Al x Ga 1−x ) 2 O 3 is determined as a function of Al composition, indicating the influence of the deposition method, orientation, and Al composition of β-(Al x Ga 1−x ) 2 O 3 films on resulting band alignments. Type II band alignments are determined at the MOCVD grown Al 2 O 3 /β-(Al x Ga 1−x ) 2 O 3 interfaces for the (010) and (100) orientations, whereas type I band alignments with relatively low conduction band offsets are observed along the [Formula: see text] orientation. The results from this study on MOCVD growth and band offsets of amorphous Al 2 O 3 deposited on differently oriented β-Ga 2 O 3 and β-(Al x Ga 1−x ) 2 O 3 films will potentially contribute to the design and fabrication of future high-performance β-Ga 2 O 3 and β-(Al x Ga 1−x ) 2 O 3 based transistors using MOCVD in situ deposited Al 2 O 3 as a gate dielectric. 

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