留言板

尊敬的读者、作者、审稿人, 关于本刊的投稿、审稿、编辑和出版的任何问题, 您可以本页添加留言。我们将尽快给您答复。谢谢您的支持!

姓名
邮箱
手机号码
标题
留言内容
验证码

Fabrication and Optoelectronic Characterization of Suspended In2O3 Nanowire Transistors

JIANG Yi-yang CHEN Yan WANG Xu-dong ZHAO Dong-yang LIN Tie SHEN Hong MENG Xiang-jian WANG Lin WANG Jian-lu

姜亦杨, 陈艳, 王旭东, 赵东洋, 林铁, 沈宏, 孟祥建, 汪琳, 王建禄. 悬空氧化铟纳米线晶体管制备与光电性能表征[J]. 中国光学. doi: 10.37188/CO.2020-0062
引用本文: 姜亦杨, 陈艳, 王旭东, 赵东洋, 林铁, 沈宏, 孟祥建, 汪琳, 王建禄. 悬空氧化铟纳米线晶体管制备与光电性能表征[J]. 中国光学. doi: 10.37188/CO.2020-0062
JIANG Yi-yang, CHEN Yan, WANG Xu-dong, ZHAO Dong-yang, LIN Tie, SHEN Hong, MENG Xiang-jian, WANG Lin, WANG Jian-lu. Fabrication and Optoelectronic Characterization of Suspended In2O3 Nanowire Transistors[J]. Chinese Optics. doi: 10.37188/CO.2020-0062
Citation: JIANG Yi-yang, CHEN Yan, WANG Xu-dong, ZHAO Dong-yang, LIN Tie, SHEN Hong, MENG Xiang-jian, WANG Lin, WANG Jian-lu. Fabrication and Optoelectronic Characterization of Suspended In2O3 Nanowire Transistors[J]. Chinese Optics. doi: 10.37188/CO.2020-0062

悬空氧化铟纳米线晶体管制备与光电性能表征

doi: 10.37188/CO.2020-0062
详细信息
  • 中图分类号: O472+.8; O472+.4

Fabrication and Optoelectronic Characterization of Suspended In2O3 Nanowire Transistors

More Information
    Author Bio:

    Yi-yang JIANG (1995—), M.Sc, School of Materials Science & Engineering, Shanghai University. His place of birth is Jiangsu. His research interests are on nanowire-based photodetectors. E-mail: Jiangyiyang95@163.com

    Jian-lu WANG (1981—), Dr, Professor, Shanghai Institute of Technical Physics, Microelectronics and Solid-state Electronics, Chinese Academy of Sciences. His place of birth is Shanxi. His research interests currently focus on ferroelectrics, 2D materials and their related electronic and optoelectronic devices. E-mail: jlwang@sitp.ac.cn

    Corresponding author: jlwang@sitp.ac.cn
  • 摘要: 一维(1D)半导体纳米线在纳米电子学和纳米光子学中表现出出色的性能。然而,纳米线晶体管的电特性对纳米线与衬底之间的相互作用非常敏感。优化器件结构可以改善纳米线晶体管的电学和光电检测性能。在这里,我们报道了通过一步式光刻技术制造的悬浮式In2O3纳米线晶体管,显示出54.6 cm2v−1s−1的高迁移率和241.5 mVdec−1的低亚阈值摆幅。作为紫外光电探测器,光电晶体管显示出极低的暗电流(~10−13 A)和高响应度1.6×105 AW−1。悬浮晶体管的沟道材料的这种简单而有效的方法可广泛用于制造高性能微纳米器件。
  • Figure  1.  Design and characterization of the single In2O3 nanowire device. (a) TEM of a single In2O3 nanowire. (b) Dark-field microscopy image of an In2O3 nanowire FET. (c) Three-dimensional schematic view of a suspended single In2O3 nanowire photodetector. (d) SEM of the suspended single In2O3 nanowire photodetector.

    Figure  2.  Fabrication process of suspended nanowire devices.

    Figure  3.  Electric performance of the single In2O3 nanowire devices under dark conditions. (a) I-V curves of the nanowire-based photodetector in different atmospheres. (b) output characteristics of the nanowire-based photodetector under different gate voltages with transfer curve switch at different source-drain biases ranging from 0.1 V to 1 V (c) in the air and (d) in vacuum state.

    Figure  4.  Photoresponse properties of the single In2O3 nanowire devices. (a) Ids-Vds characteristics of the photodetector in the dark and different wavelengths of light. (b) Photocurrent and responsivity of the photodetector under different wavelengths of light. (c) Ids-Vds characteristics of the photodetector in the dark and different intensities of light (450 nm). (d) Photoresponsivity and detectivity of the photodetector under the different intensities of light (450 nm).

    Figure  5.  Time-response characterizations of the In2O3 single-nanowire photodetector. (a) Photocurrent response of the device, where the laser light is switched on/off at an interval of 20 s (520 nm, 2.6 mW cm−2 at Vds = 1 V. (b) Enlargement of the curve in the 53−72 s range outlined in (a). (c) one single UV photocurrent response of the device (375 nm, 1.56 mW cm−2). (d) Time-resolved photoresponse of the device showing the rise and fall time of the photocurrent at Vds =0.1 V.

  • [1] HEO Y W, VARADARAJAN V, KAUFMAN M, et al. Site-specific growth of ZnO nanorods using catalysis-driven molecular-beam epitaxy[J]. Applied Physics Letters, 2002, 81(16): 3046-3048. doi:  10.1063/1.1512829
    [2] JIANG W, WANG X D, CHEN Y, et al. Large‐area high quality PtSe2 thin film with versatile polarity[J]. InfoMat, 2019, 1(2): 260-267.
    [3] YAN R X, GARGAS D, YANG P D. Nanowire photonics[J]. Nature Photonics, 2009, 3(10): 569-576. doi:  10.1038/nphoton.2009.184
    [4] WU G J, TIAN B B, LIU L, et al. Programmable transition metal dichalcogenide homojunctions controlled by nonvolatile ferroelectric domains[J]. Nature Electronics, 2020, 3(1): 43-50. doi:  10.1038/s41928-019-0350-y
    [5] APPENZELLER J, KNOCH J, BJORK M T, et al. Toward nanowire electronics[J]. IEEE Transactions on Electron Devices, 2008, 55(11): 2827-2845. doi:  10.1109/TED.2008.2008011
    [6] HONG W K, SOHN J I, HWANG D K, et al. Tunable electronic transport characteristics of surface-architecture-controlled ZnO nanowire field effect transistors[J]. Nano Letters, 2008, 8(3): 950-956. doi:  10.1021/nl0731116
    [7] CUI Y, WEI Q Q, PARK H, et al. Nanowire nanosensors for highly sensitive and selective detection of biological and chemical species[J]. Science, 2001, 293(5533): 1289-1292. doi:  10.1126/science.1062711
    [8] ZHENG G F, PATOLSKY F, CUI Y, et al. Multiplexed electrical detection of cancer markers with nanowire sensor arrays[J]. Nature Biotechnology, 2005, 23(10): 1294-1301. doi:  10.1038/nbt1138
    [9] HUANG M H, MAO S, FEICK H, et al. Room-temperature ultraviolet nanowire nanolasers[J]. Science, 2001, 292(5523): 1897-1899. doi:  10.1126/science.1060367
    [10] WAN Q, LI Q H, CHEN Y J, et al. Fabrication and ethanol sensing characteristics of ZnO nanowire gas sensors[J]. Applied Physics Letters, 2004, 84(18): 3654-3656. doi:  10.1063/1.1738932
    [11] GOMES U P, ERCOLANI D, ZANNIER V, et al. Controlling the diameter distribution and density of InAs nanowires grown by Au-assisted methods[J]. Semiconductor Science and Technology, 2015, 30(11): 115012. doi:  10.1088/0268-1242/30/11/115012
    [12] ROCCI M, DEMONTIS V, PRETE D, et al. Suspended InAs nanowire-based devices for thermal conductivity measurement using the 3ω method[J]. Journal of Materials Engineering and Performance, 2018, 27(12): 6299-6305. doi:  10.1007/s11665-018-3715-x
    [13] SU M, ZOU X M, GONG Y N, et al. Sub-kT/q switching in In2O3 nanowire negative capacitance field-effect transistors[J]. Nanoscale, 2018, 10(40): 19131-19139. doi:  10.1039/C8NR06163G
    [14] KONG Y C, YU D P, ZHANG B, et al. Ultraviolet-emitting ZnO nanowires synthesized by a physical vapor deposition approach[J]. Applied Physics Letters, 2001, 78(4): 407-409. doi:  10.1063/1.1342050
    [15] YANG M, PANG G SH, JIANG L F, et al. Hydrothermal synthesis of one-dimensional zinc oxides with different precursors[J]. Nanotechnology, 2006, 17(1): 206-212. doi:  10.1088/0957-4484/17/1/034
    [16] ZOU X M, LIU X Q, WANG C L, et al. Controllable electrical properties of metal-doped In2O3 nanowires for high-performance enhancement-mode transistors[J]. ACS Nano, 2013, 7(1): 804-810. doi:  10.1021/nn305289w
    [17] LIU Z W, ONG C, YU T, et al. Catalyst-free pulsed-laser-deposited ZnO nanorods and their room-temperature photoluminescence properties[J]. Applied Physics Letters, 2006, 88(5): 053110. doi:  10.1063/1.2168675
    [18] ZHANG D H, LI C, HAN S, et al. Electronic transport studies of single-crystalline In2O3 nanowires[J]. Applied Physics Letters, 2003, 82(1): 112-114. doi:  10.1063/1.1534938
    [19] MENG M, WU X L, JI X L, et al. Ultrahigh quantum efficiency photodetector and ultrafast reversible surface wettability transition of square In2O3 nanowires[J]. Nano Research, 2017, 10(8): 2772-2781. doi:  10.1007/s12274-017-1481-y
    [20] SHAO D L, QIN L Q, SAWYER S. Near ultraviolet photodetector fabricated from polyvinyl-alcohol coated In2O3 nanoparticles[J]. Applied Surface Science, 2012, 261: 123-127. doi:  10.1016/j.apsusc.2012.07.111
    [21] ZHU H Y, WANG Y, XIAO J, et al. Observation of piezoelectricity in free-standing monolayer MoS2[J]. Nature Nanotechnology, 2015, 10(2): 151-155. doi:  10.1038/nnano.2014.309
    [22] SU M, YANG ZH Y, LIAO L, et al. Side-Gated In2O3 nanowire ferroelectric FETs for high-performance nonvolatile memory applications[J]. Advanced Science, 2016, 3(9): 1600078. doi:  10.1002/advs.201600078
    [23] KONSTANTATOS G, SARGENT E H. Nanostructured materials for photon detection[J]. Nature Nanotechnology, 2010, 5(6): 391-400. doi:  10.1038/nnano.2010.78
    [24] ZHENG D SH, WANG J L, HU W D, et al. When nanowires meet ultrahigh ferroelectric field–high-performance full-depleted nanowire photodetectors[J]. Nano Letters, 2016, 16(4): 2548-2555. doi:  10.1021/acs.nanolett.6b00104
    [25] GUO N, HU W D, LIAO L, et al. Anomalous and highly efficient InAs nanowire phototransistors based on majority carrier transport at room temperature[J]. Advanced Materials, 2014, 26(48): 8203-8209. doi:  10.1002/adma.201403664
    [26] SOCI C, ZHANG A, XIANG B, et al. ZnO nanowire UV photodetectors with high internal gain[J]. Nano Letters, 2007, 7(4): 1003-1009. doi:  10.1021/nl070111x
    [27] GONG X, TONG M H, XIA Y J, et al. High-detectivity polymer photodetectors with spectral response from 300 nm to 1450 nm[J]. Science, 2009, 325(5948): 1665-1667. doi:  10.1126/science.1176706
    [28] DAS K, MUKHERJEE S, MANNA S, et al. Single Si nanowire (diameter ≤ 100 nm) based polarization sensitive near-infrared photodetector with ultra-high responsivity[J]. Nanoscale, 2014, 6(19): 11232-11239. doi:  10.1039/C4NR03170A
    [29] LU J F, XU C X, DAI J, et al. Improved UV photoresponse of ZnO nanorod arrays by resonant coupling with surface plasmons of Al nanoparticles[J]. Nanoscale, 2015, 7(8): 3396-3403. doi:  10.1039/C4NR07114J
    [30] LOPEZ-SANCHEZ O, LEMBKE D, KAYCI M, et al. Ultrasensitive photodetectors based on monolayer MoS2[J]. Nature Nanotechnology, 2013, 8(7): 497-501. doi:  10.1038/nnano.2013.100
    [31] ZHU X T, ZHU ZH X, YE M Y, et al. Photocatalytic degradation of organic phosphorus in microreactor and on-line detection of total phosphorus[J]. Chinese Journal Of Analytical Chemistry, 2019, 47(1): 106-111.
    [32] HUANG S Y, OU G, CHENG J, et al. Ultrasensitive visible light photoresponse and electrical transportation properties of nonstoichiometric indium oxide nanowire arrays by electrospinning[J]. Journal of Materials Chemistry C, 2013, 1(39): 6463-6470. doi:  10.1039/c3tc31051e
    [33] WANG ZH, WANG F F, WANG Z X, et al. A novel titania nanowire fiber for selective solid-phase microextraction of ultraviolet filters in environmental water samples[J]. Chinese Journal of Analytical Chemistry, 2019, 47(8): 1276-1282.
    [34] XIA H L, HUA X, LONG Y T, et al. Coupled time-of-flight secondary ion mass spectrometry-electrochemical analysis of electrode-electrolyte interface at high vacuum of 10-5 Pa[J]. Chinese Journal Of Analytical Chemistry, 2019, 47(12): 1887-1892. doi:  10.1016/S1872-2040(19)61204-1
  • [1] 孙智国, 吴晔, 魏昌庭, 耿冬苓, 李晓明, 曾海波.  Ni2+掺杂和卤素空位填充协同抑制CsPbBr3纳米晶体中的离子迁移 . 中国光学, doi: 10.37188/CO.2020-0060
    [2] Hui-wen LIU, Dong YAO, Yi LIU, Hao ZHANG.  Mn2+-doped CsPbX3 (X=Cl, Br and I) perovskite nanocrystals and their applications . 中国光学, doi: 10.3788/CO.20191205.0933
    [3] 李晓晓, 李蕴乾, 汪欣, 杨艳民.  高灵敏度下转换光学测温材料:NaGd(WO4)2:Yb3+/Er3+ . 中国光学, doi: 10.3788/CO.20191203.0596
    [4] 祝波, 高永为, 刘芷晨, 罗亚楠.  [Cd(对硝基苯甲酸)2(乙二胺)H2O]配合物的结构及荧光性能 . 中国光学, doi: 10.3788/CO.20191202.0302
    [5] 庹娟, 叶颖, 赵海琴, 王林香.  Li+、Na+共掺(YxGdyLu1-x-y)2O3:0.5%Pr3+荧光粉的制备及发光特性研究 . 中国光学, doi: 10.3788/CO.20191206.1279
    [6] 孙桂芳, 王雅丽, 孟现柱, 史强, 杨冰.  Na5[B2P3O13]晶体的紫外-远红外光谱分析 . 中国光学, doi: 10.3788/CO.20191205.1118
    [7] 王林香, 庹娟, 叶颖, 赵海琴.  Li+, Zn2+, Mg2+掺杂Lu2O3:Er3+荧光粉的制备及发光特性 . 中国光学, doi: 10.3788/CO.20191201.0112
    [8] 杨晶, 龚诚, 赵佳宇, 田浩琳, 孙陆, 陈平, 林列, 刘伟伟.  利用3D打印技术制备太赫兹器件 . 中国光学, doi: 10.3788/CO.20171001.0077
    [9] 段佩华, 张继森, 张立国, 任建岳, 骆永石, 吕少哲.  YAG粉末材料中Cr3+敏化的Yb3+近红外发光性质 . 中国光学, doi: 10.3788/CO.20150804.0603
    [10] 徐嘉林, 金维召, 刘旺, 彭海益, 刘贺, 李春, 林海, 刘景和, 曾繁明.  Ho,Yb: Tb3Ga5O12纳米粉体制备及发光性能研究 . 中国光学, doi: 10.3788/CO.20150804.0608
    [11] 曾蔚, 王汇源, 刘莹奇, 王斌, 张振铎, 曾子晗.  基于IR-SFS算法空间目标红外影像3D重建 . 中国光学, doi: 10.3788/CO.20140703.0376
    [12] 徐艳, 谢冀江, 李殿军, 杨贵龙, 陈飞.  CO2激光调Q技术 . 中国光学, doi: 10.3788/CO.20140702.0196
    [13] 时光, 梅林, 张立超.  球面元件表面AlF3薄膜的光学特性和微观结构表征 . 中国光学, doi: 10.3788/CO.20130606.906
    [14] 张家骅, 吕伟, 郝振东, 张霞, 骆永石.  利用能量传递实现可调全色单一白光 BaMg2 Al6 Si9 O30 ∶ Eu2+ , Tb3+ , Mn2+ 荧光粉(特邀) . 中国光学, doi: 10.3788/CO.20120503.0203
    [15] 张健, 张雷, 曾飞, 王旭, 赵嘉鑫, 田海英, 任航, 李俊峰.  机载激光3D探测成像系统的发展现状 . 中国光学,
    [16] 李慧, 杨魁胜, 祁宁, 左周.  Yb3+/Er3+ 掺杂氟氧化物微晶玻璃的制备与发光性能 . 中国光学,
    [17] 卫耀伟, 刘志超, 陈松林.  TiO2/Al2O3薄膜的原子层沉积和光学性能分析 . 中国光学,
    [18] 卢歆, 田坚.  Yb3+∶Y2O3超细粉体的低温燃烧法合成及发光性能 . 中国光学,
    [19] 成永杰, 邱英, 何军, 张天才, 王军民.  光学偶极阱中铷原子5S1/2及5P3/2态的AC Stark频移 . 中国光学,
    [20] 苑冰冰, 刘艳红, 丛妍, 李斌.  基于磷光配合物Re(CO)3Cl-dipyrido[3,2-a:2',3'-c] phenazine有机光伏器件 . 中国光学,
  • 加载中
图(5)
计量
  • 文章访问数:  13
  • HTML全文浏览量:  10
  • PDF下载量:  0
  • 被引次数: 0
出版历程

Fabrication and Optoelectronic Characterization of Suspended In2O3 Nanowire Transistors

doi: 10.37188/CO.2020-0062
    通讯作者: jlwang@sitp.ac.cn
  • 中图分类号: O472+.8; O472+.4

摘要: 一维(1D)半导体纳米线在纳米电子学和纳米光子学中表现出出色的性能。然而,纳米线晶体管的电特性对纳米线与衬底之间的相互作用非常敏感。优化器件结构可以改善纳米线晶体管的电学和光电检测性能。在这里,我们报道了通过一步式光刻技术制造的悬浮式In2O3纳米线晶体管,显示出54.6 cm2v−1s−1的高迁移率和241.5 mVdec−1的低亚阈值摆幅。作为紫外光电探测器,光电晶体管显示出极低的暗电流(~10−13 A)和高响应度1.6×105 AW−1。悬浮晶体管的沟道材料的这种简单而有效的方法可广泛用于制造高性能微纳米器件。

English Abstract

姜亦杨, 陈艳, 王旭东, 赵东洋, 林铁, 沈宏, 孟祥建, 汪琳, 王建禄. 悬空氧化铟纳米线晶体管制备与光电性能表征[J]. 中国光学. doi: 10.37188/CO.2020-0062
引用本文: 姜亦杨, 陈艳, 王旭东, 赵东洋, 林铁, 沈宏, 孟祥建, 汪琳, 王建禄. 悬空氧化铟纳米线晶体管制备与光电性能表征[J]. 中国光学. doi: 10.37188/CO.2020-0062
JIANG Yi-yang, CHEN Yan, WANG Xu-dong, ZHAO Dong-yang, LIN Tie, SHEN Hong, MENG Xiang-jian, WANG Lin, WANG Jian-lu. Fabrication and Optoelectronic Characterization of Suspended In2O3 Nanowire Transistors[J]. Chinese Optics. doi: 10.37188/CO.2020-0062
Citation: JIANG Yi-yang, CHEN Yan, WANG Xu-dong, ZHAO Dong-yang, LIN Tie, SHEN Hong, MENG Xiang-jian, WANG Lin, WANG Jian-lu. Fabrication and Optoelectronic Characterization of Suspended In2O3 Nanowire Transistors[J]. Chinese Optics. doi: 10.37188/CO.2020-0062
    • Recently, as device processing enters the nanometer scale, device development based on nano-materials has received increasing attention.[1-4] Among various technical approaches, the "bottom-up" method emphasizes the rational construction of nano-functional devices based on atoms and molecules, which is regarded as the core of nanotechnology. Nanowire-based devices have shown great application potential in field effect transistors (FETs), light-emitting diodes, sensors, nano-lasers and nano-generators, among others [3, 5-10]. In particular, III-V semiconductor nanowires are attracting great attention due to their excellent electrical and optical properties [11-12]. Among the many potential nanowire materials, In2O3 nanowires possess a wide bandgap of 2.8 eV and high field-effect mobility [13]. In2O3 nanowires are easy to prepare and can be produced in various ways including physical vapor deposition [14], hydrothermal methods [15], chemical vapor deposition [16], pulsed laser deposition [17] and molecular beam epitaxy [1]. Many previous studies mainly focused on the preparation and electrical properties of nanowires due to their beneficial properties such as chemical stability, excellent crystallinity, easily doping, low-cost synthesis, quantum confinement effect, and high quantum efficiency [1]. However, few studies have focused on their optoelectronic properties since the first report on the ultraviolet (UV) photodetection capabilities of In2O3 nanowires [18]. Despite recent advances, the performance of photodetectors still cannot meet practical demand.

      This work presents a strategy to fabricate and suspend In2O3 nanowire devices. Through its unique design and relatively simple manufacturing process, an In2O3 nanowire channel can be separated from its substrate. The source and drain patterns are also defined by only one electron beam lithography (EBL) step. Utilizing this device’s structure, we conducted an intrinsic study on the electrical characteristics of In2O3 nanowire FETs, exhibiting an on/off current ratio larger than 103, a subthreshold swing (SS) of 241.5 mV/dec and a low dark current of ~10-13 A. The calculated carrier mobility is approximately 54.6 cm2V−1s−1. The In2O3 nanowire photodetector exhibits a high photoconductive gain of 4.3 × 103, a responsivity of 1.6 × 105 A W-1, and a specific detectivity of (D*) up to 9.3 × 1010 Jones at a low power density of 0.06 mW cm-2(λ = 450 nm). The response time (rise time τr), which is defined as the time for the photocurrent to increase from 10% to 90% Ipeak, is about 150 ms. It is faster than In2O3 nanowire-based photodetectors that have been reported previously.[19-20]

    • The In2O3 nanowires used in this study were synthesized by chemical vapor deposition (CVD) through a vapor-liquid-solid (VLS) growth mechanism. A mixture of high-purity In2O3 powder and graphite powder with a weight ratio of 5:1 was put into a quartz boat. A silicon substrate with a pre-deposition of 1-nm and an Au catalyst was placed downstream in the quartz tube to collect the products. A furnace was set to 1100 °C in 22 min and maintained for 1 hour under a constant flow of gas (argon/oxygen = 100:1, flow rate = 200 sccm). Finally, the system was left to naturally cool to room temperature [33]. The TEM image in Fig. 1(a) shows that a large quantity of wire-like In2O3 microcrystals with good uniformity was fabricated by the CVD method. The diameter of the nanowire is approximately 50 nm. Fig. 1(b) and (c) show a dark-field microscopy image of the In2O3 nanowire FET and three-dimensional schematic view of the suspended single In2O3 nanowire photodetector. In2O3 nanowires used in this research were characterized by field-emission scanning electron microscopy and high-resolution transmission electron microscopy (HR-TEM, HT7700). The SEM result is shown in Fig. 1(d), confirming that the In2O3 nanowire is free of the substrate.

      Figure 1.  Design and characterization of the single In2O3 nanowire device. (a) TEM of a single In2O3 nanowire. (b) Dark-field microscopy image of an In2O3 nanowire FET. (c) Three-dimensional schematic view of a suspended single In2O3 nanowire photodetector. (d) SEM of the suspended single In2O3 nanowire photodetector.

      To fabricate suspended nanowire devices, the key part is to find a feasible way to fabricate a structure that is both suspended and stable. We found inspiration from previous work, which wrote about electron beam lithography on both poly-methyl-methacrylate (PMMA) and hydrogen silsesquioxane (HSQ) [21]. The process flow for preparing the suspended In2O3 nanowire FET is shown in Fig.2. Specific steps are as follows: Firstly, a layer of 280-nm-thick PMMA is spin-coated onto the Si/SiO2 substrate. Secondly, In2O3 nanowires are drop-casted onto the temporary layer of the spin-coated photoresist. The N-doped In2O3 nanowires produced by CVD have a typical length of 10 μm and a diameter of less than 100 nm. Thirdly another photoresist layer is spin-coated. Standard e-beam lithography is performed to define the electrodes on a marked In2O3 nanowire. Then, 15 nm chromium (Cr) and 300 nm gold (Au) are deposited using thermal evaporation. Finally, the fabrication of the device is finished after the lift-off process. To improve ohmic contacts, devices were annealed at 200 °C in Ar atmosphere for 2 hours.

      Figure 2.  Fabrication process of suspended nanowire devices.

    • The electrical properties of fabricated suspended In2O3 transistors are investigated with a Lake Shore Probe Station together with an Agilent B1500 (Agilent Technologies, Santa Clara, CA, USA) semiconductor parameter analyzer. The IV curves of the nanowire-based photodetector are shown in Fig. 3(a) and indicate that different atmospheres can affect electrical conductivity. The annealing process can effectively improve the contact of metal electrodes. Under dark conditions, oxygen molecules tend to chemisorb onto the surface of In2O3 nanowire by trapping free electrons from the conduction band and then becoming negative ions O2, which reduces the system’s free electron density. The larger current in a vacuum is a result of the lack of oxygen in such a test environment. Fig. 3(b) shows the typical output characteristics of the device. The liner behavior suggests good ohmic contact between the nanowires and electrodes. As shown in Fig. 3(c) and (d), low dark current (approximately 10-13 A) in both transfer curves can be attributed to the design of the suspended structure, which can effectively avoid the limitation of gate leakage current. Transfer curves of the same device in a different atmospheres show a similar clockwise hysteresis performance. It can be confirmed that the curve does not significantly shift with an increase in drain bias for a static Vgs sweep range, which suggests ideal transistor characteristics for these suspended devices in a vacuum [22]. Compared with the sharp shift of transfer curves and higher turn-off voltage in air, this suspended design suggests applications in vacuum transistors are possible. The electron mobility μFE of a single In2O3 nanowire device can be calculated by using the expression μFE= gmL2/(CgVds), where the channel length L = 2.0 μm, and gm = dIds/dVgs is the transconductance of the NANOWIRE device. Cg is the back-gate capacitance including the two parts that can be deduced based on the cylinder on-plane model: Cg1 = 2πε1εrL/[ln(4h1/d)] [22], where ε1εr is the dielectric constant of the air, h1(200 nm) is the height of suspension, and d(50 nm) is the In2O3 nanowire’s diameter. Cg2 =2πε2εrL/[ln(4h/d)], where ε2 is the permittivity of the SiO2, and h2 (280 nm) is the thickness of the SiO2 substrate. The calculated carrier mobilities of the device in air and a vacuum are 12.4 cm2 V−1 s−1and 54.6 cm2 V−1 s−1, respectively. The system may be influenced by contact between nanowires and metal electrodes. The SS can be expressed by the equation SS = ∂Vg/∂(lgId), where Vg is the applied gate voltage and Id is the drain current. The SS value calculated in the different atmospheres is 324.7 mV/dec and 241.5 mV/dec, respectively. Previous work found that performance degradation is mainly attributed to the charge accumulation in the In2O3/SiO2 interface, and the gate coupling in the non-suspended structure is not as desirable as that in suspended couplings [13]. It is necessary to design gate dielectric and electrode systems to make a breakthrough in SS value limitation (60 mVdec−1). The device shows a high on/off ratio that is larger than 103, which implies that this suspended device has immense potential in high-performance FETs.

      Figure 3.  Electric performance of the single In2O3 nanowire devices under dark conditions. (a) I-V curves of the nanowire-based photodetector in different atmospheres. (b) output characteristics of the nanowire-based photodetector under different gate voltages with transfer curve switch at different source-drain biases ranging from 0.1 V to 1 V (c) in the air and (d) in vacuum state.

      The spectral responsivity is measured using a series of laser sources (250,375,450,520,637 nm; Thorlabs, Inc) combined with Agilent B2902. The Ids-Vds characteristics of the photodetector were measured in the dark and different wavelengths of light, as shown in Fig. 4(a). The dark current of the device is 0.12 μA. The light wavelengths of 637 nm and 520 nm (~1.10 mW cm-2) have little influence on the device’s photocurrent compared to the dark current. Contrarily, as shown in Fig. 4(b), the photocurrent increases drastically when the wavelength of incident light reaches to 450 nm, which has comparable energy to the bandgap of In2O3 (2.8 eV). The responsivity (R) can be defined as Iph/(PA), where Iph is the photocurrent, P is the incident power density, and A is the effective irradiated area on the nanowire. Fig. 4(b) also shows the dramatic responsivity difference (about three orders of magnitude) on either side of the wavelength corresponding to In2O3 bandgap. The value of R is as large as 1.6 × 105 AW−1when incident light reaches the UV band with an applied voltage of 0.1 V. The results demonstrate the excellent photoresponsivity and wavelength selectivity of the In2O3 nanowire-based photodetector. The photoconductive gain (G), responsivity (R), and specific detectivity (D*) are the key parameters for evaluating the sensitivity of the photodetectors [23].

      Figure 4.  Photoresponse properties of the single In2O3 nanowire devices. (a) Ids-Vds characteristics of the photodetector in the dark and different wavelengths of light. (b) Photocurrent and responsivity of the photodetector under different wavelengths of light. (c) Ids-Vds characteristics of the photodetector in the dark and different intensities of light (450 nm). (d) Photoresponsivity and detectivity of the photodetector under the different intensities of light (450 nm).

      The corresponding external quantum efficiency (EQE) is defined as the ratio between the number of collected electrons and the number of incident photons [19]. It can be expressed by the following equation, EQE =Rhc/. The EQE of the device is calculated to be as high as 9.9 × 107% with irradiation of UV light (~ 200 nm). The high EQE is related to the exposure of the nanowire surface via the chemisorption/photodesorption of oxygen [34] It has been mentioned above that by trapping free electrons from the conduction band to becoming negative O2 ions, oxygen molecules tend to chemisorb onto the surface of an In2O3 nanowire in dark conditions, thereby reducing the free electron density O2(g) + e→ O2(ad) [19,31]. Electron–hole pairs are created in the bulk when illuminated with short-wavelength light. Due to the existence of new valence subbands, the photogenerated holes move from the bulk to the surface and these accumulated holes will react with the adsorbed oxygen ions then release a captured free electron, h+ + O2- (ad) → O2 (g) [19]. Furthermore, separation of the structure between In2O3 nanowire and substrate caused ultrahigh surface-to-volume ratios and a free-standing interface, which played an important role in high R and EQE. Figure 4(c) shows the Ids-Vds characteristics for different power intensities at a wavelength of 450 nm. The Ids-Vds curve shows a linear regime with increasing Vds. It could be predicted that there will be photon-generated carrier saturation and electron-hole recombination under strong light illumination if the bias and light intensity is large enough [24-26].

      The specific detectivity is an important figure-of-merit characterizing the capability of the smallest detectable signal for a photodetector. Considering that the shot noise from the dark current is the major factor limiting the detectivity, the specific detectivity can be given by D* = RA1/2/(2eIdark)1/2, where R is the responsivity, A is the effective area of the detector (A = L × d, L is the channel length, d is the nanowire diameter), e is the unit charge, and Idarkis the dark current. Figure 4(d) shows the calculated values of responsivity and detectivity at different power intensities. The incident light’s power is calibrated with a PM100D power meter. It shows that R and D* increase dramatically with a decreasing light intensity, which can be caused by the trap states of the In2O3 nanowires. The R and D* of the photodetector are up to 1.6 × 105 AW−1 and 9.2 × 1010 Jones, respectively, under a low light intensity of 0.06 mW cm−2. The highest responsivity is two orders of magnitude larger than that of commercial photodetectors based on Si, GaAs, and InGaAs [27]. Considering the small depletion of the intrinsic carriers in the nanowire channel, D* could be enhanced to up to 1015 Jones if further gate dielectric and electrode structures are built (to drive dark current down from 10-6 μA to 10-10 μA). The photo-conductive gain (G) is defined as the ratio between the number of charges collected by the electrodes per unit of time and the number of photons absorbed by the nanowire per unit of time (G = Ne/Nph). It can be calculated as G = (Iph/e)/(PA/), where Iph is the photocurrent, e is the electronic charge, P is the incident power density, A is the effective irradiated area, and is the energy of an incident photon. The G of the photodetector is up to 4.34 × 105 under a low light intensity of 0.062 mW/cm-2, which is due to the long photon-generated carrier lifetime in the nanowire compared to the short carrier transit time between the electrodes [24, 26, 28]. High gain shows that large photocurrent output signals can be achieved with relatively low optical input.

      The repeatability and response speed are also important parameters for photodetection [29]. Time-resolved photoresponse measurements were performed to characterize the response speed of the photodetector when switching a green light on and off repeatedly (520 nm). The photocurrent responses under 520 nm of illumination with a back gate voltage of -30 V are shown in Fig. 5(a). The response time (rise time τr) and the recovery time (fall time τf), defined as the time for the photocurrent increasing (decreasing) from 10% to 90% (90% to 10%) of Ipeak (photocurrent peak), is 0.912 s and 8 s, respectively. This data is extracted with a Tektronix MDO3014. It shows high stability and reliability with the on/off photoswitching behavior at Vds = 1 V. As for the response speed characterization of UV light (375 nm) [25], a high-speed oscilloscope was used to monitor the fast-varying optical signal. Its longer recovery time may be related to the influence of the surface states [30]. The recombination of electrons and holes may be affected by the surface trap state of the nanowire after high-energy ultraviolet radiation. The rise time τr drops sharply to 150 ms, which is faster than previous reports for In2O3 nanowires photodetectors, to our best knowledge [19-20, 32]. This can be attributed to the reduction of the interaction effect between the nanowire and the substrate.

      Figure 5.  Time-response characterizations of the In2O3 single-nanowire photodetector. (a) Photocurrent response of the device, where the laser light is switched on/off at an interval of 20 s (520 nm, 2.6 mW cm−2 at Vds = 1 V. (b) Enlargement of the curve in the 53−72 s range outlined in (a). (c) one single UV photocurrent response of the device (375 nm, 1.56 mW cm−2). (d) Time-resolved photoresponse of the device showing the rise and fall time of the photocurrent at Vds =0.1 V.

    • In summary, we have fabricated a suspended In2O3 nanowire transistor based on one-step EBL micro-nano processing technology that can stable and complete separation between a nanowire and a substrate. The intrinsic electrical transportation and photoresponse properties of In2O3 nanowire FETs are studied. The In2O3 nanowire transistors achieve a stable electrical property in a vacuum. Furthermore, this type of photodetector exhibits excellent optoelectronic performance including broad spectral responsivity, good repeatability, and fast response. Suspended nanowire structures provide an ideal way to investigate the intrinsic properties of nano-materials and broadens their applications in flexible and thermal isolation devices.

参考文献 (34)

目录

    /

    返回文章
    返回