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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. 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.)
3. Band offsets of (100) β -(Al _x Ga _1−x ) ₂ O ₃ / β -Ga ₂ O ₃ heterointerfaces grown via MOCVD

   https://doi.org/10.1063/5.0031584  

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

   null (Ed.)
4. Spatially Resolved Investigation of the Bandgap Variation across a β-(Al _x Ga _1–x ) ₂ O ₃ /β-Ga ₂ O ₃ Interface by STEM–VEELS

   https://doi.org/10.1021/acsaelm.1c00824  

   Chmielewski, Adrian; Deng, Ziling; Moradifar, Parivash; Miao, Leixin; Zhang, Yuewei; Mauze, Akhil; Lopez, Kleyser A.; Windl, Wolfgang; Alem, Nasim (February 2022, ACS Applied Electronic Materials)
5. NiO/β-(Al _x Ga _1−x ) ₂ O ₃ /Ga ₂ O ₃ heterojunction lateral rectifiers with reverse breakdown voltage >7 kV

   https://doi.org/10.1116/6.0002393  

   Wan, Hsiao-Hsuan; Li, Jian-Sian; Chiang, Chao-Ching; Xia, Xinyi; Ren, Fan; Masten, Hannah N.; Lundh, James Spencer; Spencer, Joseph A.; Alema, Fikadu; Osinsky, Andrei; et al (May 2023, Journal of Vacuum Science & Technology A)

   NiO/β-(Al x Ga 1− x ) 2 O 3 /Ga 2 O 3 heterojunction lateral geometry rectifiers with diameter 50–100  μm exhibited maximum reverse breakdown voltages >7 kV, showing the advantage of increasing the bandgap using the β-(Al x Ga 1− x ) 2 O 3 alloy. This Si-doped alloy layer was grown by metal organic chemical vapor deposition with an Al composition of ∼21%. On-state resistances were in the range of 50–2180 Ω cm 2 , leading to power figures-of-merit up to 0.72 MW cm −2 . The forward turn-on voltage was in the range of 2.3–2.5 V, with maximum on/off ratios >700 when switching from 5 V forward to reverse biases up to −100 V. Transmission line measurements showed the specific contact resistance was 0.12 Ω cm 2 . The breakdown voltage is among the highest reported for any lateral geometry Ga 2 O 3 -based rectifier. 

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