[1] [1] PEARTON S J, YANG J C, CARY P H, et al. A review of Ga2O3 materials, processing, and devices[J]. Applied Physics Reviews, 2018, 5(1): 011301.

[2] [2] ROCCAFORTE F, FIORENZA P, GRECO G, et al. Emerging trends in wide band gap semiconductors (SiC and GaN) technology for power devices[J]. Microelectronic Engineering, 2018, 187: 66-77.

[3] [3] TSAO J Y, CHOWDHURY S, HOLLIS M A, et al. Ultrawide-bandgap semiconductors: research opportunities and challenges[J]. Advanced Electronic Materials, 2018, 4(1): 1600501.

[5] [5] ZHANG J Y, SHI J L, QI D C, et al. Recent progress on the electronic structure, defect, and doping properties of Ga2O3[J]. APL Materials, 2020, 8(2): 020906.

[6] [6] AHMADI E, KOKSALDI O S, KAUN S W, et al. Ge doping of -Ga2O3 films grown by plasma-assisted molecular beam epitaxy[J]. Applied Physics Express, 2017, 10(4): 041102.

[7] [7] SASAKI K, KURAMATA A, MASUI T, et al. Device-quality -Ga2O3 epitaxial films fabricated by ozone molecular beam epitaxy[J]. Applied Physics Express, 2012, 5(3): 035502.

[8] [8] BOSI M, MAZZOLINI P, SERAVALLI L, et al. Ga2O3 polymorphs: tailoring the epitaxial growth conditions[J]. Journal of Materials Chemistry C, 2020, 8(32): 10975-10992.

[9] [9] ALEMA F, SERYOGIN G, OSINSKY A, et al. Ge doping of -Ga2O3 by MOCVD[J]. APL Materials, 2021, 9: 091102.

[10] [10] FENG Z X, ANHAR UDDIN BHUIYAN A F M, KARIM M R, et al. MOCVD homoepitaxy of Si-doped (010) -Ga2O3 thin films with superior transport properties[J]. Applied Physics Letters, 2019, 114(25): 250601.

[11] [11] FENG Z X, BHUIYAN A F M A U, XIA Z B, et al. Probing charge transport and background doping in metal-organic chemical vapor deposition-grown (010) -Ga2O3[J]. Physica Status Solidi-Rapid Research Letters, 2020, 14(8): 2000145.

[12] [12] SASAKI K, HIGASHIWAKI M, KURAMATA A, et al. MBE grown Ga2O3 and its power device applications[J]. Journal of Crystal Growth, 2013, 378: 591-595.

[13] [13] OKUMURA H, KITA M, SASAKI K, et al. Systematic investigation of the growth rate of -Ga2O3(010) by plasma-assisted molecular beam epitaxy[J]. Applied Physics Express, 2014, 7(9): 095501.

[14] [14] KALARICKAL N K, XIA Z B, MCGLONE J, et al. Mechanism of Si doping in plasma assisted MBE growth of -Ga2O3[J]. Applied Physics Letters, 2019, 115(15): 152106.

[15] [15] MAUZE A, ZHANG Y W, ITOH T, et al. Sn doping of (010) -Ga2O3 films grown by plasma-assisted molecular beam epitaxy[J]. Applied Physics Letters, 2020, 117(22): 222102.

[16] [16] ZHANG F B, SAITO K, TANAKA T, et al. Structural and optical properties of Ga2O3 films on sapphire substrates by pulsed laser deposition[J]. Journal of Crystal Growth, 2014, 387: 96-100.

[17] [17] GARTEN L M, ZAKUTAYEV A, PERKINS J D, et al. Structure property relationships in gallium oxide thin films grown by pulsed laser deposition[J]. MRS Communications, 2016, 6(4): 348-353.

[18] [18] KHARTSEV S, NORDELL N, HAMMAR M, et al. High-quality Si-doped -Ga2O3 films on sapphire fabricated by pulsed laser deposition[J]. Physica Status Solidi (B), 2021, 258(2): 2000362.

[19] [19] ZHANG J Y, WILLIS J, YANG Z N, et al. Direct determination of band-gap renormalization in degenerately doped ultrawide band gap -Ga2O3 semiconductor[J]. Physical Review B, 2022, 106(20): 205305.

[20] [20] FENG Z X, QIN P X, YANG Y L, et al. A two-dimensional electron gas based on a 5s oxide with high room-temperature mobility and strain sensitivity[J]. Acta Materialia, 2021, 204: 116516.

[21] [21] ZHANG Y W, NEAL A, XIA Z B, et al. Demonstration of high mobility and quantum transport in modulation-doped -(AlxGa1-x)2O3/Ga2O3 heterostructures[J]. Applied Physics Letters, 2018, 112(17): 173502.

[23] [23] VARLEY J B, WEBER J R, JANOTTI A, et al. Oxygen vacancies and donor impurities in -Ga2O3[J]. Applied Physics Letters, 2010, 97(14): 142106.

[24] [24] JANOWITZ C, SCHERER V, MOHAMED M, et al. Experimental electronic structure of In2O3 and Ga2O3[J]. New Journal of Physics, 2011, 13(8): 085014.

[25] [25] MOHAMED M, JANOWITZ C, UNGER I, et al. The electronic structure of -Ga2O3[J]. Applied Physics Letters, 2010, 97(21): 211903.

[26] [26] MOCK A, KORLACKI R, BRILEY C, et al. Band-to-band transitions, selection rules, effective mass, and excitonic contributions in monoclinic -Ga2O3[J]. Physical Review B, 2017, 96(24): 245205.

[27] [27] ASEL T J, STEINBRUNNER E, HENDRICKS J, et al. Reduction of unintentional Si doping in -Ga2O3 grown via plasma-assisted molecular beam epitaxy[J]. Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2020, 38(4): 043403.

[28] [28] JEON H M, LEEDY K D, LOOK D C, et al. Homoepitaxial -Ga2O3 transparent conducting oxide with conductivity =2323 S cm-1[J]. APL Materials, 2021, 9(10): 101105.

[29] [29] LANY S. Defect phase diagram for doping of Ga2O3[J]. APL Materials, 2018, 6(4): 046103.

[30] [30] IRMSCHER K, GALAZKA Z, PIETSCH M, et al. Electrical properties of -Ga2O3 single crystals grown by the Czochralski method[J]. Journal of Applied Physics, 2011, 110: 063720.

[31] [31] WANG X L, LIU T Y, LU Y Z, et al. Thermodynamic of intrinsic defects in -Ga2O3[J]. Journal of Physics and Chemistry of Solids, 2019, 132: 104-109.

[32] [32] PTER D, DUY H Q, FLORIAN S, et al. Choosing the correct hybrid for defect calculations: a case study on intrinsic carrier trapping in -Ga2O3[J]. Physical Review B, 2017, 95: 11.

[33] [33] KURAMATA A, KOSHI K, WATANABE S, et al. High-quality -Ga2O3 single crystals grown by edge-defined film-fed growth[J]. Japanese Journal of Applied Physics, 2016, 55(12): 1202A2.

[34] [34] LIU X T, WANG S Q, HE L, et al. Growth characteristics and properties of Ga2O3 films fabricated by atomic layer deposition technique[J]. Journal of Materials Chemistry C, 2022, 10(43): 16247-16264.

[35] [35] KUANG S L, YANG Z N, ZHANG Z Q, et al. Transport and electronic structure properties of MBE grown Sn doped Ga2O3 homo-epitaxial films[J]. Materials Today Physics, 2024, 48: 101555.

[36] [36] ZHANG J Y, YANG Z N, KUANG S L, et al. Electronic structure and surface band bending of Sn-doped -Ga2O3 thin films studied by X-ray photoemission spectroscopy and ab initio calculations[J]. Physical Review B, 2024, 110(11): 115120.

[37] [37] KING P D C, MCKENZIE I, VEAL T D. Observation of shallow-donor muonium in Ga2O3: evidence for hydrogen-induced conductivity[J]. Applied Physics Letters, 2010, 96(6): 062110.

[38] [38] XIANG X Q, LI L H, CHEN C, et al. Unintentional doping effect in Si-doped MOCVD -Ga2O3 films: shallow donor states[J]. Science China Materials, 2023, 66(2): 748-755.

[39] [39] ZHANG K, XU Z W, ZHAO J L, et al. Temperature-dependent Raman and photoluminescence of -Ga2O3 doped with shallow donors and deep acceptors impurities[J]. Journal of Alloys and Compounds, 2021, 881: 160665.

[40] [40] NEAL A T, MOU S, RAFIQUE S, et al. Donors and deep acceptors in -Ga2O3[J]. Applied Physics Letters, 2018, 113(6): 062101.

[41] [41] MENG L Y, FENG Z X, BHUIYAN A F M A U, et al. High-mobility MOCVD -Ga2O3 epitaxy with fast growth rate using trimethylgallium[J]. Crystal Growth & Design, 2022, 22(6): 3896-3904.

[42] [42] MA N, TANEN N, VERMA A, et al. Intrinsic electron mobility limits in -Ga2O3[J]. Applied Physics Letters, 2016, 109(21): 212101.

[43] [43] MOTT N F. The transition to the metallic state[J]. Philosophical Magazine, 1961, 6(62): 287-309.

[44] [44] PARISINI A, FORNARI R. Analysis of the scattering mechanisms controlling electron mobility in -Ga2O3 crystals[J]. Semiconductor Science and Technology, 2016, 31(3): 035023.

[45] [45] NEAL A T, MOU S, LOPEZ R, et al. Incomplete ionization of a 110 meV unintentional donor in -Ga2O3 and its effect on power devices[J]. Scientific Reports, 2017, 7(1): 13218.

[46] [46] ORITA M, OHTA H, HIRANO M, et al. Deep-ultraviolet transparent conductive -Ga2O3 thin films[J]. Applied Physics Letters, 2000, 77(25): 4166-4168.

[47] [47] OISHI T, HARADA K, KOGA Y, et al. Conduction mechanism in highly doped -Ga2O3 single crystals grown by edge-defined film-fed growth method and their Schottky barrier diodes[J]. Japanese Journal of Applied Physics, 2016, 55(3): 030305.

[48] [48] SHKLOVSKII B I, EFROS A L. Electronic properties of doped semiconductors[M]. Springer Science & Business Media, 2013.