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β-phase gallium oxide (Ga2O3) is an emerging ultrawide bandgap (UWBG) semiconductor with a bandgap energy of ∼ 4.8 eV and a predicted high critical electric field strength of ∼8 MV/cm, enabling promising applications in next generation high power electronics and deep ultraviolet optoelectronics. The advantages of Ga2O3 also stem from its availability of single crystal bulk native substrates synthesized from melt, and its well-controllable n-type doping from both bulk growth and thin film epitaxy. Among several thin film growth methods, metalorganic chemical vapor deposition (MOCVD) has been demonstrated as an enabling technology for developing high-quality epitaxy of Ga2O3 thin films, (AlxGa1−x)2O3 alloys, and heterostructures along various crystal orientations and with different phases. This tutorial summarizes the recent progresses in the epitaxial growth of β-Ga2O3 thin films via different growth methods, with a focus on the growth of Ga2O3 and its compositional alloys by MOCVD. The challenges for the epitaxial development of β-Ga2O3 are discussed, along with the opportunities of future works to enhance the state-of-the-art device performance based on this emerging UWBG semiconductor material system.
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Flexible single-crystalline GaN substrate by direct deposition of III-N thin films on polycrystalline metal tape
Flexible electronics and mechanically bendable devices based on Group III-N semiconductor materials are emerging; however, there are several challenges in manufacturing, such as cost reduction, device stability and flexibility, and device-performance improvement. To overcome these limitations, it is necessary to replace the brittle and expensive semiconductor wafers with single-crystalline flexible templates for a new-bandgap semiconductor platform. The substrates in the new concept of semiconductor materials have a hybrid structure consisting of a single-crystalline III-N thin film on a flexible metal tape substrate which provides a convenient and scalable roll-to-roll deposition process. We present a detailed study of a unique and simple direct epitaxial growth technique for crystallinity transformation to deliver single-crystalline GaN thin film with highly oriented grains along both a -axis and c -axis directions on a flexible and polycrystalline copper tape. A 2-dimensional (2D) graphene having the same atomic configuration as the (0001) basal plane of wurtzite structure is employed as a seed layer which plays a key role in following the III-N epitaxy growth. The DC reactive magnetron sputtering method is then applied to deposit an AlN layer under optimized conditions to achieve preferred-orientation growth. Finally, single-crystalline GaN layers (∼1 μm) are epitaxially grown using metal organic chemical vapor deposition (MOCVD) on the biaxially-textured buffer layer. The flexible single-crystalline GaN film obtained using this method provides a new way for a wide-bandgap semiconductor platform pursuing flexible, high-performance, and versatile device technology.
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- Award ID(s):
- 1907626
- PAR ID:
- 10310327
- Date Published:
- Journal Name:
- Journal of Materials Chemistry C
- Volume:
- 9
- Issue:
- 7
- ISSN:
- 2050-7526
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1039/d0tc04634e
