Epitaxial growth and solar-blind photoelectric properties of corundum-structured α -Ga 2 O 3 thin films

Guo, Daoyou; Zhao, Xiaolong; Zhi, Yusong; Cui, Wei; Huang, Yonghui; An, Yarui; Li, P.G.; Wu, Zhenping

doi:10.1016/j.matlet.2015.11.001

Cited by 109 publications

(65 citation statements)

References 21 publications

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“…Experimental and theoretical studies on phases other than the β phase are limited. Among the metastable phases, α-Ga 2 O 3 has been extensively studied [33][34][35] and its alloy with α-Al 2 O 3 has attracted attention in band-gap engineering [36,37]. In addition, doping of α-Ga 2 O 3 with Sn leads to high n-type conductivity [38], as in the case of β-Ga 2 O 3 [2,9].…”

Section: Introductionmentioning

confidence: 99%

First-principles study of self-trapped holes and acceptor impurities in Ga2O3 polymorphs

Gake

Kumagai

Oba

2019

Phys. Rev. Materials

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We investigate the stability of self-trapped holes (STHs) and the acceptor levels of substitutional Mg and N impurities in α-, β-, δ-, and ε-Ga 2 O 3 using first-principles calculations based on the hybrid functional approach to assess their p-type dopability. When Fock-exchange and screening parameter values in the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional are optimized to satisfy the generalized Koopmans' theorem for a STH level in β-Ga 2 O 3 , the band gap is slightly overestimated, while functionals that well reproduce the band gap show slight convex behavior against the fractional electron number. However, the absolute position of the STH level at a fixed geometry is nearly independent of the parameter value, showing that the results are robust as long as the STH geometry and localized electronic nature are appropriately described and the band edges are well reproduced. In all of the polymorphs, holes localize with high self-trapping energies rather than being delocalized. Furthermore, both Mg and N impurities introduce polaronic acceptor states, and their acceptor levels lie far above the valence band maximum in all the polymorphs. Thus, the p-type doping of the four Ga 2 O 3 polymorphs seems unfeasible in terms of the STH formation and the related deep, polaronic acceptor nature of the Mg and N impurities.

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Section: Introductionmentioning

confidence: 99%

First-principles study of self-trapped holes and acceptor impurities in Ga2O3 polymorphs

Gake

Kumagai

Oba

2019

Phys. Rev. Materials

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“…Sometimes a disordered structure with P6 3 mc space-group symmetry is labeled as ε-Ga 2 O 3 , which is comprised of domains of an ordered phase labeled κ-Ga 2 O 3 that is the same as the ordered orthorhombic ε-Ga 2 O 3 with Pna2 1 space-group symmetry [16]. These four phases are considered metastable [17,18], but the α- [19,20], γ - [21][22][23], and ε-Ga 2 O 3 [24][25][26] phases can be grown on various kinds of substrates. In particular, α-Ga 2 O 3 has been studied as a wide-gap semiconductor.…”

Section: Introductionmentioning

confidence: 99%

Band alignment at surfaces and heterointerfaces ofAl2O3,Ga2O3,
Hinuma
¹
,
Gake
²
,
Oba
³

2019
Phys. Rev. Materials
38
4
21
0
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The band alignments at nonpolar surfaces and heterointerfaces of Al 2 O 3 , Ga 2 O 3 , and In 2 O 3 polymorphs, and three related group-III oxides, namely, Sc 2 O 3 , Y 2 O 3 , and La 2 O 3 , are investigated by using first-principles calculations. A non-self-consistent dielectric-dependent hybrid functional approach is adopted on top of semilocal density-functional calculations by using the Perdew-Burke-Ernzerhof functional tuned for solids (PBEsol) to accelerate the band alignment evaluation that involves surface and interface calculations. Among the five crystal structures considered, namely, corundum, β-gallia, κ-alumina, bixbyite (C-type rare earth), and A-type rare earth, the lowest energy phases are corundum, β-gallia, A-type rare earth, and bixbyite for Al 2 O 3 , Ga 2 O 3 , La 2 O 3 , and the others, respectively, within PBEsol calculations. The ionization potential typically decreases in the order Al 2 O 3 , Ga 2 O 3 , In 2 O 3 , Sc 2 O 3 , Y 2 O 3 , and La 2 O 3 within the same crystal structure and surface termination. This tendency is enhanced by the atomic relaxation-induced surface dipoles, where smaller cations tend to relax toward the bulk side compared to O ions, while larger cations tend to relax toward the vacuum side. The ionization potential and electron affinity differences at unrelaxed surfaces are good indicators of the interfacial valence-and conduction-band offsets, respectively, for Al 2 O 3 /Ga 2 O 3 with a relatively small mismatch in the lattice parameters of the two phases.

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“…Among all ve phases of Ga 2 O 3 (a, b, g, d and 3), the b-Ga 2 O 3 with monoclinic crystal structure is the thermally and chemically most stable phase, has been widely studied in solar-blind photodetectors. [13][14][15][16][17][18][19] So far, b-Ga 2 O 3 -based photodetectors mainly fall into three categories: lm type, single crystals and nanorod arrays (NRAs) type. Compared to thin lms, vertical nanowire array structures display more superior optical absorption ability and higher carrier generation, resulting from high surface-to-volume ratio and effective optical coupling, which can further improve the performance of photodetectors.…”

Section: Introductionmentioning

confidence: 99%

β-Ga₂O₃ nanorod arrays with high light-to-electron conversion for solar-blind deep ultraviolet photodetection

et al. 2019

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Epitaxial growth and solar-blind photoelectric properties of corundum-structured α -Ga 2 O 3 thin films

Cited by 109 publications

References 21 publications

First-principles study of self-trapped holes and acceptor impurities in Ga2O3 polymorphs

First-principles study of self-trapped holes and acceptor impurities in Ga2O3 polymorphs

Band alignment at surfaces and heterointerfaces ofAl2O3,Ga2O3,
Hinuma
¹
,
Gake
²
,
Oba
³

2019
Phys. Rev. Materials
38
4
21
0
View full text Add to dashboard Cite

β-Ga₂O₃ nanorod arrays with high light-to-electron conversion for solar-blind deep ultraviolet photodetection

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Epitaxial growth and solar-blind photoelectric properties of corundum-structured α -Ga 2 O 3 thin films

Cited by 109 publications

References 21 publications

First-principles study of self-trapped holes and acceptor impurities in Ga2O3 polymorphs

First-principles study of self-trapped holes and acceptor impurities in Ga2O3 polymorphs

Band alignment at surfaces and heterointerfaces ofAl2O3,Ga2O3,Hinuma1, Gake2, Oba3 2019Phys. Rev. Materials384210View full textAdd to dashboardCite

β-Ga2O3 nanorod arrays with high light-to-electron conversion for solar-blind deep ultraviolet photodetection

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Band alignment at surfaces and heterointerfaces ofAl2O3,Ga2O3,
Hinuma
¹
,
Gake
²
,
Oba
³

2019
Phys. Rev. Materials
38
4
21
0
View full text Add to dashboard Cite

β-Ga₂O₃ nanorod arrays with high light-to-electron conversion for solar-blind deep ultraviolet photodetection