(Invited) Growth and Characterization ofα-,β-, andε-Ga2O3Epitaxial Layers on Sapphire

Yao, Yao; Lyle, Luke A. M.; Rokholt, Johanne A.; Okur, Serdal; Tompa, Gary S.; Salagaj, T.; Sbrockey, Nick M.; Davis, R. F.; Porter, Lisa M.

doi:10.1149/08007.0191ecst

Cited by 29 publications

(9 citation statements)

References 24 publications

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“…Figure 1(b,c) shows the XRD spectra of two samples (#105 and #114) also grown at 650 • C containing α-and ε-Ga 2 O 3 as the respective dominant phases. For sample #105 (Figure 1(b) Figure 1 [34].…”

Section: Resultsmentioning

confidence: 99%

Growth and characterization of α-, β-, and ϵ-phases of Ga₂O₃ using MOCVD and HVPE techniques

Yao

Okur

Lyle

et al. 2018

Materials Research Letters

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177

109

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Heteroepitaxial films of Ga 2 O 3 were grown on c-plane sapphire (0001). The stable phase β-Ga 2 O 3 was grown using the metalorganic chemical vapor deposition technique, regardless of precursor flow rates, at temperatures between 500 • C and 850 • C. Metastable α-and ε-phases were grown when using the halide vapor phase epitaxy (HVPE) technique, at growth temperatures between 650 • C and 850 • C, both separately and in combination. XTEM revealed the better lattice-matched α-phase growing semi-coherently on the substrate, followed by ε-Ga 2 O 3 . The epitaxial relationship was determined to be [1100] IMPACT STATEMENTThis study demonstrates one of the first epitaxial growths of multiple polymorphs of Ga 2 O 3 on sapphire (0001) substrates, including its β-, α-, and ε-phases. Epitaxial relationship is confirmed through HRTEM. ARTICLE HISTORY

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Section: Resultsmentioning

confidence: 99%

Growth and characterization of α-, β-, and ϵ-phases of Ga₂O₃ using MOCVD and HVPE techniques

Yao

Okur

Lyle

et al. 2018

Materials Research Letters

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177

109

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“…The large number of structural phases and the strong anisotropy of β-Ga 2 O 3 present difficulties for theoretical approaches. Nevertheless, previous theoretical work carried out on Ga 2 O 3 polymorphs focuses on various properties, for example, optical response, electron transport, electronic structure, and X-ray absorption spectra, calculated at different levels of computational expense and accuracy. − Experimental studies predominantly consider material growth and optical properties with more extensive information available for the β-phase. ,− Very few studies to date combine theory and experiment, thus leaving some doubt over the accuracy of calculations and uncertainty in the understanding and interpretation of experimental data. ,,− Overall, little information is available for the polymorphs of Ga 2 O 3 and studies considering a set or subset of the polymorphs are extremely rare. However, comparative studies of the polymorphs are invaluable for discerning trends between the different structures and advancing our understanding of the material.…”

Section: Introductionmentioning

confidence: 99%

Influence of Polymorphism on the Electronic Structure of Ga₂O₃

et al. 2020

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The search for new wide-band-gap materials is intensifying to satisfy the need for more advanced and energy-efficient power electronic devices. Ga2O3 has emerged as an alternative to SiC and GaN, sparking a renewed interest in its fundamental properties beyond the main β-phase. Here, three polymorphs of Ga2O3, α, β, and ε, are investigated using X-ray diffraction, X-ray photoelectron and absorption spectroscopy, and ab initio theoretical approaches to gain insights into their structure–electronic structure relationships. Valence and conduction electronic structure as well as semicore and core states are probed, providing a complete picture of the influence of local coordination environments on the electronic structure. State-of-the-art electronic structure theory, including all-electron density functional theory and many-body perturbation theory, provides detailed understanding of the spectroscopic results. The calculated spectra provide very accurate descriptions of all experimental spectra and additionally illuminate the origin of observed spectral features. This work provides a strong basis for the exploration of the Ga2O3 polymorphs as materials at the heart of future electronic device generations.

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“…Studies of successfully heteroepitaxial growth of metastable ε-Ga 2 O 3 on sapphire mainly use the HVPE technique which has fast growth rate (a few μm/h). Researchers were able to achieve phase-pure ε-Ga 2 O 3 on c -plane sapphire, GaN (0001), AlN (0001), and β-Ga 2 O 3 (−201) by this technique at 550 °C. , Since the ε-Ga 2 O 3 is a highly symmetric hexagonal structure, , close to the III-nitrides, there is the implication that it should be possible to integrate ε-Ga 2 O 3 with nitrides to form heterojunctions for optoelectronic devices. Thus, a precise control of the growth rate of ε-Ga 2 O 3 by using MOCVD is necessary.…”

Section: Introductionmentioning

confidence: 99%

HCl Flow-Induced Phase Change of α-, β-, and ε-Ga₂O₃ Films Grown by MOCVD

Sun

Castanedo

et al. 2018

Crystal Growth & Design

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156

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Precise control of the hetero-epitaxy on a low-cost foreign substrate is often the key to drive the success of fabricating semiconductor devices in scale when a large low-cost native substrate is not available. Here, we successfully synthesized three different phases of Ga2O3 (α, β, and ε) films on c-plane sapphire by only tuning the flow rate of HCl along with other precursors in an MOCVD reactor. A threefold increase in the growth rate of pure β-Ga2O3 was achieved by introducing only 5 sccm of HCl flow. With continuously increased HCl flow, a mixture of βand ε-Ga2O3 was observed, until the Ga2O3 film transformed completely to a pure ε-Ga2O3 with a smooth surface and the highest growth rate (~1 µm/hour) at a flow rate of 30 sccm. At 60 sccm, we found that the film tended to have a mixture of αand ε-Ga2O3 with a dominant α-Ga2O3, while the growth rate dropped significantly (~0.4 µm/hour). The film became rough as a result of the mixture phases since the growth rate of ε-Ga2O3 is much higher than α-Ga2O3. In this HClenhanced MOCVD mode, the Cl impurity concentration was almost identical among the investigated samples. Based on our density functional theory calculation, we found that the relative energy between β-, ε-, and α-Ga2O3 became smaller thus inducing the phase change by increasing the HCl flow in the reactor. Thus, it is plausible that the HCl acted as a catalyst during 2 the phase transformation process. Furthermore, we revealed the microstructure and the epitaxial relationship between Ga2O3 with different phases and the c-plane sapphire substrates. Our HClenhanced MOCVD approach paves the way to achieving highly controllable hetero-epitaxy of Ga2O3 films with different phases for device applications.

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(Invited) Growth and Characterization ofα-,β-, andε-Ga₂O₃Epitaxial Layers on Sapphire

Cited by 29 publications

References 24 publications

Growth and characterization of α-, β-, and ϵ-phases of Ga₂O₃ using MOCVD and HVPE techniques

Growth and characterization of α-, β-, and ϵ-phases of Ga₂O₃ using MOCVD and HVPE techniques

Influence of Polymorphism on the Electronic Structure of Ga₂O₃

HCl Flow-Induced Phase Change of α-, β-, and ε-Ga₂O₃ Films Grown by MOCVD

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(Invited) Growth and Characterization ofα-,β-, andε-Ga2O3Epitaxial Layers on Sapphire

Cited by 29 publications

References 24 publications

Growth and characterization of α-, β-, and ϵ-phases of Ga2O3 using MOCVD and HVPE techniques

Growth and characterization of α-, β-, and ϵ-phases of Ga2O3 using MOCVD and HVPE techniques

Influence of Polymorphism on the Electronic Structure of Ga2O3

HCl Flow-Induced Phase Change of α-, β-, and ε-Ga2O3 Films Grown by MOCVD

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Resources

About

(Invited) Growth and Characterization ofα-,β-, andε-Ga₂O₃Epitaxial Layers on Sapphire

Growth and characterization of α-, β-, and ϵ-phases of Ga₂O₃ using MOCVD and HVPE techniques

Growth and characterization of α-, β-, and ϵ-phases of Ga₂O₃ using MOCVD and HVPE techniques

Influence of Polymorphism on the Electronic Structure of Ga₂O₃

HCl Flow-Induced Phase Change of α-, β-, and ε-Ga₂O₃ Films Grown by MOCVD