Heteroepitaxy of ε-Ga₂O₃ thin film for artificial synaptic device

Abstract

Emerging-wide bandgap semiconductor Ga₂O₃ shows distinct characteristics for optoelectronic applications and a stable crystal phase of Ga₂O₃ is highly desired. Herein, we have first reported a metal-semiconductor-metal structure photonic synaptic device based on the ε-Ga₂O₃ thin film. The ε-Ga₂O₃ epilayer is grown on the c-sapphire with a low temperature nucleation layer, which presents a crystal orientation relationship with the c-sapphire (ε-Ga₂O₃ <010> // c-sapphire <1-100> and ε-Ga₂O₃ <001> // c-sapphire <0001>). The ε-Ga₂O₃ photonic device was stimulated by UV pulses at different pulse widths, pulse intervals, and reading voltages. Under the UV pulse excitation, the photonic device exhibits primary synaptic functions including excitatory postsynaptic current, short term memory, pair pulse facilitation, long term memory, and STM-to-LTM conversion. In addition, stronger and repeated stimuli can naturally contribute to the higher learning capability, thus prolonging the memory time.

Keywords

heteroepitaxy / MOCVD / photonic synaptic device / ε-Ga₂O₃

References

[1] Wang YF, Lin ZH, Ma JL, et al. Multifunctional solar-blind ultraviolet photodetectors based on p-PCDTBT/n-Ga₂O₃ heterojunction with high photoresponse. InfoMat. 2024; 6(2):e12503.

[2] Sasaki K, Higashiwaki M, Kuramata A, Masui T, Yamakoshi S. MBE grown Ga₂O₃ and its power device applications. J Cryst Growth. 2013; 378: 591-595.

[3] Su LX, Chen SY, Zhao LQ, Zuo YQ, Xie J. Low temperature atomic layer deposition of GaO_xN_y thin film on III-GaN: Mg for UV photodetector. Appl Phys Lett. 2020; 117(21):211101.

[4] Tian W, Sun HX, Chen L, et al. Low-dimensional nanomaterial/Si heterostructure-based photodetectors. InfoMat. 2019; 1(2): 140-163.

[5] Kong WY, Wu GA, Wang KY, et al. Graphene-β-Ga₂O₃ heterojunction for highly sensitive deep UV photodetector application. Adv Mater. 2016; 28(48): 10725-10731.

[6] Chen YC, Lu YJ, Lin CN, et al. Self-powered diamond/β-Ga₂O₃ photodetectors for solar-blind imaging. J Mater Chem C. 2018; 6(21): 5727-5732.

[7] Lu YC, Zhang ZF, Yang X, et al. High-performance solar-blind photodetector arrays constructed from Sn-doped Ga₂O₃ microwires via patterned electrodes. Nano Res. 2022; 15(8): 7631-7638.

[8] Chen YC, Yang X, Zhang Y, et al. Ultra-sensitive flexible Ga₂O₃ solar-blind photodetector array realized via ultra-thin absorbing medium. Nano Res. 2022; 15(4): 3711-3719.

[9] Oshima Y, Víllora EG, Matsushita Y, Yamamoto S, Shimamura K. Epitaxial growth of phase-pure ε-Ga₂O₃ by halide vapor phase epitaxy. J Appl Phys. 2015; 118(8):085301.

[10] Roy R, Hill VG, Osborn EF. Polymorphism of Ga₂O₃ and the system Ga₂O₃-H₂O. J Am Chem Soc. 1952; 74(3): 719-722.

[11] Chen XH, Ren FF, Gu SL, Ye JD. Review of gallium-oxide-based solar-blind ultraviolet photodetectors. Photon Res. 2019; 7(4): 381-415.

[12] Li ZM, Jiao T, Yu JQ, et al. Single crystalline β-Ga₂O₃ homoepitaxial films grown by MOCVD. Vacuum. 2020; 178:109440.

[13] Rafique S, Karim MR, Johnson JM, Hwang J, Zhao HP. LPCVD homoepitaxy of Si doped β-Ga₂O₃ thin films on (010) and (001) substrates. Appl Phys Lett. 2018; 112(5):052104.

[14] Sasaki K, Kuramata A, Masui T, Víllora EG, Shimamura K, Yamakoshi S. Device-quality β-Ga₂O₃ epitaxial films fabricated by ozone molecular beam epitaxy. Appl Phys Express. 2012; 5(3):035502.

[15] Rafique S, Han L, Tadjer MJ, Freitas JA, Mahadik NA, Zhao HP. Homoepitaxial growth of β-Ga₂O₃ thin films by low pressure chemical vapor deposition. Appl Phys Lett. 2016; 108(18):182105.

[16] Schewski R, Lion K, Fiedler A, et al. Step-flow growth in homoepitaxy of β-Ga₂O₃ (100)-the influence of the miscut direction and faceting. Apl Mater. 2019; 7(2):022515.

[17] Hoshikawa K, Ohba E, Kobayashi T, Yanagisawa J, Miyagawa C, Nakamura Y. Growth of β-Ga₂O₃ single crystals using vertical Bridgman method in ambient air. J Cryst Growth. 2016; 447: 36-41.

[18] Reese SB, Remo T, Green J, Zakutayev A. How much will gallium oxide power electronics cost? Joule. 2019; 3(4): 903-907.

[19] McCluskey MD. Point defects in Ga₂O₃. J Appl Phys. 2020; 127(10):101101.

[20] Chen ZM, Li ZQ, Zhuo Y, et al. Layer-by-layer growth of ε-Ga₂O₃ thin film by metal-organic chemical vapor deposition. Appl Phys Express. 2018; 11(10):101101.

[21] Zhang JG, Wang W, Wu SM, et al. Exploratory phase stabilization in heteroepitaxial gallium oxide films by pulsed laser deposition. J Alloy Compd. 2023; 935(2):168123.

[22] Zhang WR, Wang W, Zhang JF, et al. Directional carrier transport in micrometer-thick gallium oxide films for high-performance deep-ultraviolet photodetection. ACS Appl Mater Interfaces. 2023; 15(8): 10868-10876.

[23] Hsu YH, Wu WY, Lin KL, et al. ε-Ga₂O₃ grown on c-plane sapphire by MOCVD with a multistep growth process. Cryst Growth Des. 2022; 22(3): 1-9.

[24] Kracht M, Karg A, Schörmann J, et al. Tin-assisted synthesis of ε-Ga₂O₃ by molecular beam epitaxy. Phys Rev Appl. 2017; 8(5):054002.

[25] Li SQ, Du JG, Lu BJ, et al. Gradual conductance modulation by defect reorganization in amorphous oxide memristors. Mater Horiz. 2023; 10(12): 5643-5655.

[26] Yang RQ, Wang Y, Li SQ, et al. All-optically controlled artificial synapse based on full oxides for low-power visible neural network computing. Adv Funct Mater. 2023; 34(10):2312444.

[27] Yang RQ, Tian Y, Hu LX, et al. Dual-input optoelectronic synaptic transistor based on amorphous ZnAlSnO for multi-target neuromorphic simulation. Mater Today Nano. 2024; 26:100480.

[28] Yin ZG, Zhang XW, Fu Z, et al. Persistent photoconductivity in ZnO nanostructures induced by surface oxygen vacancy. Phys Status Solidi RRL. 2012; 6(3): 117-119.

[29] Wang C, Lu WM, Li FN, Ning HY, Ma F. Persistent photoconductivity in a-IGZO thin films induced by trapped electrons and metastable donors. J Appl Phys. 2022; 131(12):125709.

[30] Brinzari V. Mechanism of band gap persistent photoconductivity (PPC) in SnO nanoscrystalline films: nature of local states, simulation of PPC and comparison with experiment. Appl Surf Sci. 2017; 411: 437-448.

[31] Chen YC, Li Y, Niu SF, et al. High temperature resistant solar-blind ultraviolet photosensor for neuromorphic computing and cryptography. Adv Funct Mater. 2024; 34(24):2315383.

[32] Li P, Shan XY, Lin Y, et al. Tin doping induced high-performance solution-processed Ga₂O₃ photosensor toward neuromorphic visual system. Adv Funct Mater. 2023; 33(46):2303584.

[33] Zhu R, Hang HL, Hu SG, Wang Y, Mei ZX. Amorphous-Ga₂O₃ optoelectronic synapses with ultra-low energy consumption. Adv Electron Mater. 2022; 8(1):2100741.

[34] Yoon Y, Kim Y, Hwang WS, Shin M. Biological UV photoreceptors-inspired Sn-doped polycrystalline β-Ga₂O₃ optoelectronic synaptic phototransistor for neuromorphic computing. Adv Electron Mater. 2023; 9(7):2300098.

[35] Chen XR, Mi W, Li M, et al. Optoelectronic artificial synapses based on β-Ga₂O₃ films by RF magnetron sputtering. Vacuum. 2021; 192:110422.

[36] Li RL, Wang WX, Li Y, Gao S, Yue WJ, Shen GZ. Multi-modulated optoelectronic memristor based on Ga₂O₃/MoS₂ heterojunction for bionic synapses and artificial visual system. Nano Energy. 2023; 111:108398.

[37] Fornari R, Pavesi M, Montedoro V, et al. Thermal stability of ε-Ga₂O₃ polymorph. Acta Mater. 2017; 140: 411-416.

[38] Playford HY, Hannon AC, Barney ER, Walton RI. Structures of uncharacterised polymorphs of gallium oxide from total neutron diffraction. Chem Eur J. 2013; 19(8): 2803-2813.

[39] Parisini A, Bosio A, Bardeleben HJ, et al. Deep and shallow electronic states associated to doping, contamination and intrinsic defects in ε-Ga₂O₃ epilayers. Mater Sci Semicond Process. 2022; 138:106307.

[40] Qin Y, Li LH, Zhao XL, et al. Metal-semiconductor-metal ε-Ga₂O₃ solar-blind photodetectors with a record-high responsivity rejection ratio and their gain mechanism. ACS Photonics. 2020; 7(3): 812-820.

[41] Varley JB, Weber JR, Janotti A, Van Walle CG. Oxygen vacancies and donor impurities in β-Ga₂O₃. Appl Phys Lett. 2010; 97(14):142106.

[42] Ho QD, Frauenheim T, Deák P. Origin of photoluminescence in β-Ga₂O₃. Phys Rev B. 2018; 97(11):115163.

[43] Berencén Y, Xie Y, Wang M, Prucnal S, Rebohle L, Zhou SQ. Structural and optical properties of pulsed-laser deposited crystalline β-Ga₂O₃ thin films on silicon. Semicond Sci Technol. 2019; 34(3):035001.

[44] Scharmann F, Cherkashinin G, Breternitz V, et al. Viscosity effect on GaInSn studied by XPS. Surf Interface Anal. 2004; 36(8): 981-985.

[45] Chen ZM, Lu X, Tu YJ, et al. ε-Ga₂O₃: an emerging wide bandgap piezoelectric semiconductor for application in radio frequency resonators. Adv Sci. 2022; 9(32):2203927.

[46] Su LX. Room temperature growth of CsPbBr₃ single crystal for asymmetric MSM structure photodetector. J Mater Sci Technol. 2024; 187: 113-122.

[47] Lee WCA, Bonin V, Reed M, et al. Anatomy and function of an excitatory network in the visual cortex. Nature. 2016; 532(7599): 370-374.

[48] Zhou HT, Cong LJ, Ma JG, et al. High gain broadband photoconductor based on amorphous Ga₂O₃ and suppression of persistent photoconductivity. J Mater Chem C. 2019; 7(42): 13149-13155.

[49] Wang J, Xiong YQ, Ye LJ, et al. Balanced performance for β-Ga₂O₃ solar blind photodetectors: the role of oxygen vacancies. Opt Mater. 2021; 112:110808.

[50] Yang HR, Cheng TH, Xin Q, et al. Efficient suppression of persistent photoconductivity in β-Ga₂O₃-based photodetectors with square nanopore arrays. ACS Appl Mater Interfaces. 2023; 15(27): 32561-32568.

[51] Liu Z, Du L, Zhang SH, et al. Synergetic effect of photoconductive gain and persistent photocurrent in a high-photoresponse Ga₂O₃ deep-ultraviolet photodetector. IEEE Trans Electron Dev. 2022; 69(10): 5595-5602.

[52] Fang HH, Hu WD. Photogating in low dimensional photodetectors. Adv Sci. 2017; 4(12):1700323.

[53] Hao DD, Liu DP, Zhang JY, Wang Y, Huang J. Lead-free perovskites-based photonic synaptic devices with logic functions. Adv Mater Technol. 2021; 6(12):2100678.

[54] Kim MK, Lee JS. Short-term plasticity and long-term potentiation in artificial biosynapses with diffusive dynamics. ACS Nano. 2018; 12(2): 1680-1687.

RIGHTS & PERMISSIONS

2024 The Author(s). InfoScience published by UESTC and John Wiley & Sons Australia, Ltd.