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Growth and characterization of β-Ga2O3 thin films grown on off-angled Al2O3 substrates by metal-organic chemical vapor deposition

Yabao Zhang1, 2, Jun Zheng1, 2, , Peipei Ma1, 2, Xueyi Zheng1, 3, Zhi Liu1, 2, Yuhua Zuo1, 2, Chuanbo Li3 and Buwen Cheng1, 2

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 Corresponding author: Jun Zheng, zhengjun@semi.ac.cn

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Abstract: Beta-gallium oxide (β-Ga2O3) thin films were deposited on c-plane (0001) sapphire substrates with different mis-cut angles along <$11\bar{2}0$> by metal-organic chemical vapor deposition (MOCVD). The structural properties and surface morphology of as-grown β-Ga2O3 thin films were investigated in detail. It was found that by using thin buffer layer and mis-cut substrate technology, the full width at half maximum (FWHM) of the ($ \bar{2}01$) diffraction peak of the β-Ga2O3 film is decreased from 2° on c-plane (0001) Al2O3 substrate to 0.64° on an 8° off-angled c-plane (0001) Al2O3 substrate. The surface root-mean-square (RMS) roughness can also be improved greatly and the value is 1.27 nm for 8° off-angled c-plane (0001) Al2O3 substrate. Room temperature photoluminescence (PL) was observed, which was attributed to the self-trapped excitons formed by oxygen and gallium vacancies in the film. The ultraviolet–blue PL intensity related with oxygen and gallium vacancies is decreased with the increasing mis-cut angle, which is in agreement with the improved crystal quality measured by high resolution X-ray diffraction (HR-XRD). The present results provide a route for growing high quality β-Ga2O3 film on Al2O3 substrate.

Key words: β-Ga2O3heteroepitaxymis-cut Al2O3 substratesMOCVD



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Fig. 1.  (Color online) XRD patterns of β-Ga2O3 films deposited on c-plane Al2O3 substrates with different off-axis angles toward <$11\bar{2}0 $>.

Fig. 2.  (Color online) (a) XRD rocking curves of the ($\bar{2}01 $) diffraction peaks of β-Ga2O3 films deposited on c-plane Al2O3 substrates with different off-axis angles toward <$11\bar{2}0 $>, (b) FWHM as a function of off-axis angles of Al2O3 substrates.

Fig. 3.  Cross-sectional TEM of the film deposited on an 8° off-axis sapphire substrate with a thickness of 300 nm. (a) Image of the whole film. (b) HRTEM micrograph of the interface. (c) Selected area electron diffraction (SAED) obtained by Fourier transform of area B. (d) Selected area electron diffraction (SAED) obtained by Fourier transform of area A.

Fig. 4.  (Color online) 10 × 10 μm2 AFM patterns of β-Ga2O3 films deposited on (a) 0°, (b) 4°, (c) 6° and (d) 8° off-axis Al2O3 substrates. All films were annealed in-situ for 10 min under an oxygen atmosphere.

Fig. 5.  SEM of β-Ga2O3 thin films on Al2O3 substrates with (a) 0°, (b) 4°, (c) 6°, and (d) 8° off-angles toward <$ 11\bar{2}0$>.

Fig. 6.  (Color online) (a) Room temperature PL spectra of all films grown on off-angled Al2O3 substrates. The broad emission band from ultraviolet to blue of the β-Ga2O3 film deposited on (b) 4°, (c) 6°, and (d) 8° can be divided into two emission peaks near 365 and 410 nm.

[1]
Jeong Y J, Yang J Y, Lee C H, et al. Fluorine-based plasma treatment for hetero-epitaxial β-Ga2O3 MOSFETs. Appl Surf Sci, 2021, 558, 149936 doi: 10.1016/j.apsusc.2021.149936
[2]
Jubu P R, Yam F K. Development and characterization of MSM UV photodetector based on gallium oxide nanostructures. Sens Actuator A, 2020, 312, 112141 doi: 10.1016/j.sna.2020.112141
[3]
Lv Y J, Zhou X Y, Long S B, et al. Enhancement-mode β-Ga2O3 metal-oxide-semiconductor field-effect transistor with high breakdown voltage over 3000 V realized by oxygen annealing. Phys Status Solidi RRL, 2020, 14, 1900586 doi: 10.1002/pssr.201900586
[4]
Dong H, Xue H W, He Q M, et al. Progress of power field effect transistor based on ultra-wide bandgap Ga2O3 semiconductor material. J Semicond, 2019, 40, 011802 doi: 10.1088/1674-4926/40/1/011802
[5]
Tippins H H. Optical absorption and photoconductivity in the band edge of β-Ga2O3. Phys Rev, 1965, 140, A316 doi: 10.1103/PhysRev.140.A316
[6]
Ueda N, Hosono H, Waseda R, et al. Anisotropy of electrical and optical properties in β-Ga2O3 single crystals. Appl Phys Lett, 1997, 71, 933 doi: 10.1063/1.119693
[7]
Kohn J A, Broder J D. Characterization of β-Ga2O3 and its alumina isomorph, θ-Al2O3. Am Mineral, 1957, 42, 398
[8]
Stepanov S I, Nikolaev V I, Bougrov V E, et al. Gallium oxide: Properties and applications - A review. Rev Adv Mater Sci, 2016, 44, 63
[9]
Pearton S J, Yang J C, Cary P H, et al. A review of Ga2O3 materials, processing, and devices. Appl Phys Rev, 2018, 5, 011301 doi: 10.1063/1.5006941
[10]
Wang D, He L N, Le Y, et al. Characterization of single crystal β-Ga2O3 films grown on SrTiO3 (100) substrates by MOCVD. Ceram Int, 2020, 46, 4568 doi: 10.1016/j.ceramint.2019.10.185
[11]
Cao Q, He L N, Xiao H D, et al. β-Ga2O3 epitaxial films deposited on epi-GaN/sapphire (0001) substrates by MOCVD. Mater Sci Semicond Process, 2018, 77, 58 doi: 10.1016/j.mssp.2018.01.010
[12]
Mi W, Ma J, Luan C N, et al. Characterization of β-Ga2O3 epitaxial films grown on MgO (111) substrates by metal-organic chemical vapor deposition. Mater Lett, 2012, 87, 109 doi: 10.1016/j.matlet.2012.07.106
[13]
Mi W, Luan C N, Li Z, et al. Ultraviolet-green photoluminescence of β-Ga2O3 films deposited on MgAl6O10 (100) substrate. Opt Mater, 2013, 35, 2624 doi: 10.1016/j.optmat.2013.07.030
[14]
Qian C, Sun J, Zhang L, et al. Crystal-domain orientation and boundary in highly ordered organic semiconductor thin film. J Phys Chem C, 2015, 119, 14965 doi: 10.1021/acs.jpcc.5b03727
[15]
Nakagomi S, Kokubun Y. Crystal orientation of β-Ga2O3 thin films formed on c-plane and a-plane sapphire substrate. J Cryst Growth, 2012, 349, 12 doi: 10.1016/j.jcrysgro.2012.04.006
[16]
Boschi F, Bosi M, Berzina T, et al. Hetero-epitaxy of ε-Ga2O3 layers by MOCVD and ALD. J Cryst Growth, 2016, 443, 25 doi: 10.1016/j.jcrysgro.2016.03.013
[17]
Zhuo Y, Chen Z M, Tu W B, et al. β-Ga2O3 versus ε-Ga2O3: Control of the crystal phase composition of gallium oxide thin film prepared by metal-organic chemical vapor deposition. Appl Surf Sci, 2017, 420, 802 doi: 10.1016/j.apsusc.2017.05.241
[18]
Hu D Q, Wang Y, Zhuang S W, et al. Surface morphology evolution and optoelectronic properties of heteroepitaxial Si-doped β-Ga2O3 thin films grown by metal-organic chemical vapor deposition. Ceram Int, 2018, 44, 3122 doi: 10.1016/j.ceramint.2017.11.079
[19]
Wu J W, Mi W, Yang Z C, et al. Influence of annealing on the structural and optical properties of gallium oxide films deposited on c-sapphire substrate. Vacuum, 2019, 167, 6 doi: 10.1016/j.vacuum.2019.05.034
[20]
Wei J Q, Kim K, Liu F, et al. β-Ga2O3 thin film grown on sapphire substrate by plasma-assisted molecular beam epitaxy. J Semicond, 2019, 40, 012802 doi: 10.1088/1674-4926/40/1/012802
[21]
Oshima Y, Vίllora E G, Shimamura K. Quasi-heteroepitaxial growth of β-Ga2O3 on off-angled sapphire (0001) substrates by halide vapor phase epitaxy. J Cryst Growth, 2015, 410, 53 doi: 10.1016/j.jcrysgro.2014.10.038
[22]
Xu W L, Shi J C, Li Y W, et al. Study of β-Ga2O3 films hetero-epitaxially grown on off-angled sapphire substrates by halide vapor phase epitaxy. Mater Lett, 2021, 289, 129411 doi: 10.1016/j.matlet.2021.129411
[23]
Rafique S, Han L, Neal A T, et al. Towards high-mobility heteroepitaxial β-Ga2O3 on sapphire–dependence on the substrate off-axis angle. Phys Status Solidi A, 2018, 215, 1700467 doi: 10.1002/pssa.201700467
[24]
Zhang T, Hu Z G, Li Y F, et al. Investigation on the β-Ga2O3 deposited on off-angled sapphire (0001) substrates. J Lumin, 2021, 233, 117928 doi: 10.1016/j.jlumin.2021.117928
[25]
Bryan I, Bryan Z, Mita S, et al. Surface kinetics in AlN growth: A universal model for the control of surface morphology in III-nitrides. J Cryst Growth, 2016, 438, 81 doi: 10.1016/j.jcrysgro.2015.12.022
[26]
Xie M H, Cheung S H, Zheng L X, et al. Step bunching of vicinal GaN(0001) surfaces during molecular beam epitaxy. Phys Rev B, 2000, 61, 9983 doi: 10.1103/PhysRevB.61.9983
[27]
Varley J B, Janotti A, Franchini C, et al. Role of self-trapping in luminescence andp-type conductivity of wide-band-gap oxides. Phys Rev B, 2012, 85, 081109 doi: 10.1103/PhysRevB.85.081109
[28]
Ho C H, Tseng C Y, Tien L C. Thermoreflectance characterization of beta-Ga2O3 thin-film nanostrips. Opt Express, 2010, 18, 16360 doi: 10.1364/OE.18.016360
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    Received: 13 January 2022 Revised: 08 April 2022 Online: Accepted Manuscript: 15 May 2022Uncorrected proof: 18 May 2022Published: 02 September 2022

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      Yabao Zhang, Jun Zheng, Peipei Ma, Xueyi Zheng, Zhi Liu, Yuhua Zuo, Chuanbo Li, Buwen Cheng. Growth and characterization of β-Ga2O3 thin films grown on off-angled Al2O3 substrates by metal-organic chemical vapor deposition[J]. Journal of Semiconductors, 2022, 43(9): 092801. doi: 10.1088/1674-4926/43/9/092801 Y B Zhang, J Zheng, P P Ma, X Y Zheng, Z Liu, Y H Zuo, C B Li, B W Cheng. Growth and characterization of β-Ga2O3 thin films grown on off-angled Al2O3 substrates by metal-organic chemical vapor deposition[J]. J. Semicond, 2022, 43(9): 092801. doi: 10.1088/1674-4926/43/9/092801Export: BibTex EndNote
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      Yabao Zhang, Jun Zheng, Peipei Ma, Xueyi Zheng, Zhi Liu, Yuhua Zuo, Chuanbo Li, Buwen Cheng. Growth and characterization of β-Ga2O3 thin films grown on off-angled Al2O3 substrates by metal-organic chemical vapor deposition[J]. Journal of Semiconductors, 2022, 43(9): 092801. doi: 10.1088/1674-4926/43/9/092801

      Y B Zhang, J Zheng, P P Ma, X Y Zheng, Z Liu, Y H Zuo, C B Li, B W Cheng. Growth and characterization of β-Ga2O3 thin films grown on off-angled Al2O3 substrates by metal-organic chemical vapor deposition[J]. J. Semicond, 2022, 43(9): 092801. doi: 10.1088/1674-4926/43/9/092801
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      Growth and characterization of β-Ga2O3 thin films grown on off-angled Al2O3 substrates by metal-organic chemical vapor deposition

      doi: 10.1088/1674-4926/43/9/092801
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      • Author Bio:

        Yabao Zhang received his BSci degree from Jilin University, China in 2019. He is currently a master's student at the Institute of Semiconductors, Chinese Academy of Sciences. His research interest is the epitaxial growth mechanism of gallium oxide

        Jun Zheng received the BSci degree from Beijing Institute of Technology, China in 2006 and PhD degree in physical electronics from Graduated University of Chinese Academy of Sciences, China in 2011. He is now an associate researcher in Institute of Semiconductors, Chinese Academy of Sciences, China. His research interest is silicon photonics and gallium oxide devices

      • Corresponding author: zhengjun@semi.ac.cn
      • Received Date: 2022-01-13
      • Revised Date: 2022-04-08
      • Available Online: 2022-05-15

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