Growth of α-Ga2O3 on α-Al2O3 by conventional molecular-beam epitaxy and metal–oxide-catalyzed epitaxy

McCandless, Jonathan P.; Rowe, Derek; Pieczulewski, Naomi A.; Protasenko, Vladimir; Alonso-Orts, Manuel; Williams, Martin S.; Eickhoff, Martin; Xing, Huili Grace; Muller, David A.; Jena, Debdeep; Vogt, Patrick

doi:10.35848/1347-4065/acbe04

Cited by 9 publications

(1 citation statement)

References 32 publications

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“…The underlying mechanism has been described as metal exchange catalysis (MEXCAT) or metal-oxide-catalyzed epitaxy (MOCATAXY) in which the catalyst element (Sn/In) or its suboxide (SnO, In 2 O) is preferably oxidized on the growth surface and exchanged subsequently by Ga due to the stronger Ga–O than catalyst-O bonds, thus forming the Ga 2 O 3 layer. ,− This metal exchange leads to a segregation and/or desorption of the catalyst during the growth process, with the possibility to deposit α-, β-, ,,, and κ-Ga 2 O 3 layers ,, (depending on the used substrate) with just limited amounts of the catalyst being incorporated. Consequently, the incorporation of In for the formation of phase-pure β-(In x Ga 1– x ) 2 O 3 alloys is particularly challenging in MBE.…”

Section: Introductionmentioning

confidence: 99%

Molecular Beam Epitaxy of β-(In_xGa_1–x)₂O₃on β-Ga₂O₃(010): Compositional Control, Layer Quality, Anisotropic Strain Relaxation, and Prospects for Two-Dimensional Electron Gas Confinement

Mazzolini,

Wouters,

Albrecht

et al. 2024

ACS Appl. Mater. Interfaces

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In this work, we investigate the growth of monoclinic β-(In x Ga1–x )2O3 alloys on top of (010) β-Ga2O3 substrates via plasma-assisted molecular beam epitaxy. In particular, using different in situ (reflection high-energy electron diffraction) and ex situ (atomic force microscopy, X-ray diffraction, time-of-flight secondary ion mass spectrometry, and transmission electron microscopy) characterization techniques, we discuss (i) the growth parameters that allow for In incorporation and (ii) the obtainable structural quality of the deposited layers as a function of the alloy composition. In particular, we give experimental evidence of the possibility of coherently growing (010) β-(In x Ga1–x )2O3 layers on β-Ga2O3 with good structural quality for x up to ≈ 0.1. Moreover, we show that the monoclinic structure of the underlying (010) β-Ga2O3 substrate can be preserved in the β-(In x Ga1–x )2O3 layers for wider concentrations of In (x ≤ 0.19). Nonetheless, the formation of a large amount of structural defects, like unexpected ( ) oriented twin domains and partial segregation of In is suggested for x > 0.1. Strain relaxes anisotropically, maintaining an elastically strained unit cell along the a* direction vs plastic relaxation along the c* direction. This study provides important guidelines for the low-end side tunability of the energy bandgap of β-Ga2O3-based alloys and provides an estimate of its potential in increasing the confined carrier concentration of two-dimensional electron gases in β-(In x Ga1–x )2O3/(Al y Ga1–y )2O3 heterostructures.

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Section: Introductionmentioning

confidence: 99%

Molecular Beam Epitaxy of β-(In_xGa_1–x)₂O₃on β-Ga₂O₃(010): Compositional Control, Layer Quality, Anisotropic Strain Relaxation, and Prospects for Two-Dimensional Electron Gas Confinement

Mazzolini,

Wouters,

Albrecht

et al. 2024

ACS Appl. Mater. Interfaces

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Growth of β-Ga2O3 and ϵ/κ-Ga2O3 on AlN(0001) by molecular-beam epitaxy

Raghuvansy,

McCandless,

Schowalter

et al. 2023

APL Materials

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The heteroepitaxial growth and phase formation of Ga2O3 on Al-polar AlN(0001) templates by molecular-beam epitaxy (MBE) are studied. Three different MBE approaches are employed: (i) conventional MBE, (ii) suboxide MBE (S-MBE), and (iii) metal-oxide-catalyzed epitaxy (MOCATAXY). We grow phase-pure β-Ga2O3(2̄01) and phase-pure ϵ/κ-Ga2O3(001) with smooth surfaces by S-MBE and MOCATAXY. Thin film analysis shows that the crystallographic and surface features of the β-Ga2O3(2̄01)/AlN(0001) and ϵ/κ-Ga2O3(001)/AlN(0001) epilayers are of high crystalline quality. Growth and phase diagrams are developed to synthesize Ga2O3 on AlN by MBE and MOCATAXY and to provide guidance to grow Ga2O3 on several non-oxide surfaces, e.g., AlN, GaN, and SiC, by MBE, S-MBE, and MOCATAXY.

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Growth, catalysis, and faceting of α-Ga2O3 and α-(InxGa1−x)2O3 on m-plane α-Al2O3 by molecular beam epitaxy

Williams,

Alonso-Orts,

Schowalter

et al. 2024

APL Materials

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The growth of α-Ga2O3 and α-(InxGa1−x)2O3 on m-plane α-Al2O3(101̄0) by molecular beam epitaxy (MBE) and metal-oxide-catalyzed epitaxy (MOCATAXY) is investigated. By systematically exploring the parameter space accessed by MBE and MOCATAXY, phase-pure α-Ga2O3(101̄0) and α-(InxGa1−x)2O3(101̄0) thin films are realized. The presence of In on the α-Ga2O3 growth surface remarkably expands its growth window far into the metal-rich flux regime and to higher growth temperatures. With increasing O-to-Ga flux ratio (RO), In incorporates into α-(InxGa1−x)2O3 up to x ≤ 0.08. Upon a critical thickness, β-(InxGa1−x)2O3 nucleates and, subsequently, heteroepitaxially grows on top of α-(InxGa1−x)2O3 facets. Metal-rich MOCATAXY growth conditions, where α-Ga2O3 would not conventionally stabilize, lead to single-crystalline α-Ga2O3 with negligible In incorporation and improved surface morphology. Higher TTC further results in single-crystalline α-Ga2O3 with well-defined terraces and step edges at their surfaces. For RO ≤ 0.53, In acts as a surfactant on the α-Ga2O3 growth surface by favoring step edges, while for RO ≥ 0.8, In incorporates and leads to a-plane α-(InxGa1−x)2O3 faceting and the subsequent (2̄01) β-(InxGa1−x)2O3 growth on top. Thin film analysis by scanning transmission electron microscopy reveals highly crystalline α-Ga2O3 layers and interfaces. We provide a phase diagram to guide the MBE and MOCATAXY growth of single-crystalline α-Ga2O3 on α-Al2O3(101̄0).

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Growth of α-Ga₂O₃ on α-Al₂O₃ by conventional molecular-beam epitaxy and metal–oxide-catalyzed epitaxy

Cited by 9 publications

References 32 publications

Molecular Beam Epitaxy of β-(In_xGa_1–x)₂O₃on β-Ga₂O₃(010): Compositional Control, Layer Quality, Anisotropic Strain Relaxation, and Prospects for Two-Dimensional Electron Gas Confinement

Molecular Beam Epitaxy of β-(In_xGa_1–x)₂O₃on β-Ga₂O₃(010): Compositional Control, Layer Quality, Anisotropic Strain Relaxation, and Prospects for Two-Dimensional Electron Gas Confinement

Growth of β-Ga2O3 and ϵ/κ-Ga2O3 on AlN(0001) by molecular-beam epitaxy

Growth, catalysis, and faceting of α-Ga2O3 and α-(InxGa1−x)2O3 on m-plane α-Al2O3 by molecular beam epitaxy

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Growth of α-Ga2O3 on α-Al2O3 by conventional molecular-beam epitaxy and metal–oxide-catalyzed epitaxy

Cited by 9 publications

References 32 publications

Molecular Beam Epitaxy of β-(InxGa1–x)2O3on β-Ga2O3(010): Compositional Control, Layer Quality, Anisotropic Strain Relaxation, and Prospects for Two-Dimensional Electron Gas Confinement

Molecular Beam Epitaxy of β-(InxGa1–x)2O3on β-Ga2O3(010): Compositional Control, Layer Quality, Anisotropic Strain Relaxation, and Prospects for Two-Dimensional Electron Gas Confinement

Growth of β-Ga2O3 and ϵ/κ-Ga2O3 on AlN(0001) by molecular-beam epitaxy

Growth, catalysis, and faceting of α-Ga2O3 and α-(InxGa1−x)2O3 on m-plane α-Al2O3 by molecular beam epitaxy

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Growth of α-Ga₂O₃ on α-Al₂O₃ by conventional molecular-beam epitaxy and metal–oxide-catalyzed epitaxy

Molecular Beam Epitaxy of β-(In_xGa_1–x)₂O₃on β-Ga₂O₃(010): Compositional Control, Layer Quality, Anisotropic Strain Relaxation, and Prospects for Two-Dimensional Electron Gas Confinement

Molecular Beam Epitaxy of β-(In_xGa_1–x)₂O₃on β-Ga₂O₃(010): Compositional Control, Layer Quality, Anisotropic Strain Relaxation, and Prospects for Two-Dimensional Electron Gas Confinement