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1. 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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2. First-principles surface energies for monoclinic Ga 2 O 3 and Al 2 O 3 and consequences for cracking of (Al x Ga 1−x ) 2 O 3

   https://doi.org/10.1063/5.0019915  

   Mu, Sai ; Wang, Mengen ; Peelaers, Hartwin ; Van de Walle, Chris G. ( September 2020 , APL Materials)

   null (Ed.)
3. A review of band structure and material properties of transparent conducting and semiconducting oxides: Ga 2 O 3 , Al 2 O 3 , In 2 O 3 , ZnO, SnO 2 , CdO, NiO, CuO, and Sc 2 O 3

   https://doi.org/10.1063/5.0078037  

   Spencer, Joseph A. ; Mock, Alyssa L. ; Jacobs, Alan G. ; Schubert, Mathias ; Zhang, Yuhao ; Tadjer, Marko J. ( March 2022 , Applied Physics Reviews)

   This Review highlights basic and transition metal conducting and semiconducting oxides. We discuss their material and electronic properties with an emphasis on the crystal, electronic, and band structures. The goal of this Review is to present a current compilation of material properties and to summarize possible uses and advantages in device applications. We discuss Ga 2 O 3 , Al 2 O 3 , In 2 O 3 , SnO 2 , ZnO, CdO, NiO, CuO, and Sc 2 O 3 . We outline the crystal structure of the oxides, and we present lattice parameters of the stable phases and a discussion of the metastable polymorphs. We highlight electrical properties such as bandgap energy, carrier mobility, effective carrier masses, dielectric constants, and electrical breakdown field. Based on literature availability, we review the temperature dependence of properties such as bandgap energy and carrier mobility among the oxides. Infrared and Raman modes are presented and discussed for each oxide providing insight into the phonon properties. The phonon properties also provide an explanation as to why some of the oxide parameters experience limitations due to phonon scattering such as carrier mobility. Thermal properties of interest include the coefficient of thermal expansion, Debye temperature, thermal diffusivity, specific heat, and thermal conductivity. Anisotropy is evident in the non-cubic oxides, and its impact on bandgap energy, carrier mobility, thermal conductivity, coefficient of thermal expansion, phonon modes, and carrier effective mass is discussed. Alloys, such as AlGaO, InGaO, (Al x In y Ga 1− x− y ) 2 O 3 , ZnGa 2 O 4 , ITO, and ScGaO, were included where relevant as they have the potential to allow for the improvement and alteration of certain properties. This Review provides a fundamental material perspective on the application space of semiconducting oxide-based devices in a variety of electronic and optoelectronic applications. 

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4. MOCVD growth of β-phase (Al x Ga 1−x ) 2 O 3 on ( 2 ¯01) β-Ga 2 O 3 substrates

   https://doi.org/10.1063/5.0025478  

   Bhuiyan, A F ; Feng, Zixuan ; Johnson, Jared M. ; Huang, Hsien-Lien ; Hwang, Jinwoo ; Zhao, Hongping ( October 2020 , Applied Physics Letters)

   null (Ed.)
5. Optical and electrical properties of Ti-doped β-Ga 2 O 3 (Ti 3+ :β-Ga 2 O 3 ) bulk crystals grown by floating zone method

   https://doi.org/10.1088/1361-6463/aba3eb  

   Wang, Buguo ; Look, David ; Farlow, Gary ( August 2020 , Journal of Physics D: Applied Physics)