基于新型二维材料及异质结光电探测器的研究

发布时间：2018-03-05 06:03

本文选题：二维材料　切入点：石墨烯　出处：《南京大学》2017年博士论文　论文类型：学位论文

【摘要】：近些年来,二维材料的广泛研究是继石墨烯(graphene)的发现并证实它能够在室温下稳定存在之后。人们相继发现其他多种二维材料,例如氮化硼(BN)、过渡金属硫族化合物(TMDs)、黑磷(b-P)及黑磷合金等,这些新型二维材料的发现引起了人们极大的关注。由于这些新型二维层状材料具有不同的带隙大小,因而可以将其分为绝缘体、半导体和半金属。这些新型二维材料分别具有各自的优异性质和不足。所幸运的是,便捷的二维材料异质结制作和组装技术的发展,使得这些二维材料相互弥补不足和发挥优势。可以通过任意堆叠次序不同的二维材料形成的异质结。从而我们能够使用异质结研究一些基础物理和器件性能。从而使得人们能够在研究人工结构材料上获得重大的突破。石墨烯具有线性色散关系、无质量狄拉克费米子、高迁移率和无带隙性质。更重要的是石墨烯具有相对较强的光吸收,单原子层吸收2.3%并与层数无关。这些优异的物理性质使得石墨烯材料在光探测尤其是红外波段光探测和高频器件具有很好的应用前景。最近新发现的黑磷(b-P)和黑砷磷(b-AsP)合金块体材料带隙在0.3-0.1电子伏,同时黑磷晶体的结构对称性较低,具有较强的各向异性和对偏振光的偏振角度的灵敏依赖。另外黑磷是p-型的二维半导体材料,具有较高的空穴迁移率,使得黑磷是中波红外光探测的和偏振光灵敏探测的理想材料。然而,目前研究最为广泛的过渡金属硫族化合物,由于其具有中等带隙主要的光电响应波段位于可见波段和近红外波段,而且过渡金属硫族化合物具有很强的光与物质相互作用、较大的开关比和比较稳定的性质等。有望被用于下一代新型逻辑器件和光电子器件。人们在TMDs中发现了很多新奇的物理现象和潜在的器件应用价值。氮化硼具有较大带隙～6.0 eV,对应深紫外波段,属于二维绝缘体材料,具有较好的介电性能和原子级平整的衬底,是其他二维半导体材料的很好的保护层,能够屏蔽散射获得较高的电子迁移率。随着研究的深入,有更多的二维材料等待我们研究发现,有更优异的性质需要开发利用为人们更好的服务。本论文主要研究二维材料及其异质结光电探测,通过设计和制作异质结器件,实现光探测中的新的功能和提高探测器的综合性能。目前研究最广泛的半导体二维材料主要是过渡金属硫族化合物,由于硫族元素易形成空位,从而容易实现电子型掺杂,因此过渡金属硫族化合物大部分是n-型半导体和双极性材料。P-n结具有本征的内建电场是逻辑器件和实现高灵敏光探测的最基本的需求。目前p-型掺杂的二维材料过渡金属硫族化合物还很少,形成能带结构匹配较好的p-n结,实现p-型掺杂是目前需要解决的重点之一。对于高灵敏的光电探测,p-n结的内建电场能够有效降低暗电流和有效分离光生载流子。制作高质量的p-n在光电探测领域是迫切需要的。我们通过掺杂Ta实现WSe2载流子类型的调控。较强的p-型二维半导体材料是实现原子层厚度p-n结的技术关键。高质量的p-n结是实现逻辑器件和光伏型探测的基础。通过设计p-g-n型异质结器件,实现宽波段红外探测,利用石墨烯的无带隙性质,实现宽波段吸收。通常石墨烯内光生载流子的寿命比较短,在内建电场作用下可以有效实现两种载流子的快速分离。空间上的分离能够有效提高载流子的寿命,同时内建电场有效减低暗电流,从而减小噪声。因而p-g-n实现高灵敏宽波段光电探测。中波红外在红外探测在军事和导弹制导追踪等具有重要应用价值。目前,所使用的中波红外探测器需要在低温下工作,需要液氮制冷,使用成本增加和条件苛刻不利于便捷使用。迫切需要发展和研究室温便捷的中波红外探测器。应用窄带隙b-AsP场效应管和b-AsP-MoS2异质结实现高灵敏室温中波红外探测。在窄带隙二维层状材料的合成如PtSe2等和器件应用做了一些探索。在第三章中,首先我们设计p-g-n型异质结宽波段光电探测器。结合包括拉曼(Raman)、光致发光(PL)、原子力显微镜(AFM)和光学显微镜对样品的层数和薄膜质量进行了表征。通过微区定点转移技术,实现多层异质结器件的制作。使用具有较大功函数金属,例如金属钯、铂、金等实现WSe2的p-型掺杂调控。与费米面钉扎较强的MoS2形成很好的p-n结。中间层的无带隙的石墨烯可以有效扩展响应的带宽。同时p-g-n异质结还可以使用高迁移率石墨烯作为透明电极,实现分离后的载流子快速分离。通过设计这种p-g-n异质结,我们实现室温下探测波段从400nm-2400nm的宽波段探测。光电响应率高达4250AW-1,比探测了高达1015 Jones。这些高灵敏的光探测可以实现光电流成像,较高分辨率的图像获得。同时我们还研究了光电响应机制研究,通过可见光和近红外光电流空间成像,得出我们器件的光响应是主要来自p-g-n的内建电场的结区。另外,背栅和偏置电压对光电响应具有较好的调制作用。第四章中我们深入研究了窄带隙、高迁移率的黑砷磷合金(b-As0.83P0.17)场效应器件和黑磷砷合金与硫化钼(b-Aso.83P0.17-MoS2)异质结器件的中波红外光探测性能。重点研究b-As0.83P0.17场效应管器件从可见光到中波红外的光电响应的机制,得出光伏效应是红外波段光电探测的主要机制。通过在黑磷材料中掺杂砷元素并进行砷成分调控,实现83%的砷掺杂的黑砷磷样品。通过样品吸收光谱的研究发现b-As0.83Po.17带隙为～0.15 eV,光学吸收边位于1250 cm-1。探测的探测波段从可见波段到中波红外400 nm-8.05 um。我们研究了 b-As0.83P0.17-MoS2异质结的光电响应,异质结有效降低了暗电流。另外我们研究了异质结器件的噪声谱,在异质结器件中噪声功率比b-As0.83P0.17的场效应器件噪声功率密度小两个数量级。这说明异质结器件能够有效降低暗电流和噪声功率,有效提高器件的灵敏度。同时b-As0.83P0.17的样品具有较强的电学和光电响应的各向异性,因而对偏振光的偏振角度有灵敏的依赖。我们得到的b-AS0.83P0.17的场效应器件比探测率在所测波段400 nm-8.05 um都高于108 Jones。对于异质结器件从400 nm-4.3 um比探测率高于4.9×1 09 Jones。第五章新型过渡金属硫族化合物生长的探索和窄带隙材料的合成主要包括以下几个部分内容,其一,通过Ta掺杂实现本征P-型WSe2;其二,CVT合成WSe2纳米线;其三,探索窄带隙低维材料生长合成,主要包含掺杂的黑磷样品、CVT方法生长窄带隙PtSe2和CVD法硒化金属铂获得PtSe2。采用CVT的方法生长出了 p-型的Ta掺杂的WSe2单晶,具有良好的p-型导电性质。通过微区定点转移制备的Ta0.01W0.99Se2-MoS2异质结和Tao.01W0.99Se2-WSe2同质结,这些器件表现出理想的二极管性能,理想因子～1,整流比达到105。光电响应实验进一步证明异质结界面质量良好。组内合作研究了新型二维材料异质结ReS2-BN高灵敏弱光探测器和WSe2-graphene异质结光电探测器表现出很好的光电响应。最后一章中,我们总结了一下前面论文中的一些重要结果,对目前已取得的进展及面临的一些问题进行讨论与分析,并且希望来能够继续推进未完成的工作,在二维材料光电探测的研究方向做出更大的贡献。
[Abstract]:In recent years, extensive research material is the two-dimensional graphene (graphene) after the discovery and confirmed that it can exist stably at room temperature. People have been found in a variety of other two-dimensional materials such as boron nitride (BN), transition metal chalcogenides (TMDs), black phosphorus (b-P) and black phosphorus alloy and so on, these a novel two-dimensional material discovery has aroused great attention. Because of these new 2D layered materials with different band gap size, which can be divided into insulators, semiconductors and Semimetals. These new materials are two-dimensional with excellent characteristics and disadvantages of each other. Fortunately, the two-dimensional material heterogeneity and convenient node development and assembly technology, the two-dimensional material and each make up for lack of advantage. Can the formation of heterojunction two-dimensional materials through arbitrary stacking sequence different. Thus we can use of a heterojunction Some basic physics and device performance. So that people can obtain the significant breakthrough in the research of artificial material structure. Graphene has a linear dispersion relation, massless Dirac fermions, high mobility and band gap properties. More importantly graphene has relatively strong light absorption, absorption and a single atomic layer 2.3% the number of independent. These excellent physical properties make graphene materials in optical detection especially light detection and high frequency infrared device has good application prospects. The recently discovered black phosphorus (b-P) and black arsenic phosphorus (b-AsP) alloy blocks the band gap in the 0.3-0.1 electron volts, and the crystal structure of black phosphorus low symmetry with strong anisotropy and polarization angle of polarized light sensitive dependence. In addition is a two-dimensional black phosphorus p- type semiconductor material, with high hole mobility, the black phosphorus is mid infrared light detection The ideal material and polarized light sensitive detection. However, the present study of transition metal chalcogenides widely, because of its moderate band gap main photoelectric response band in the visible band and near infrared band, but also has a strong interaction of light and matter transition metal chalcogenides, larger than the switch and the nature relatively stable. It could be used for the next generation of new logic devices and optoelectronic devices. People find a lot of interesting physical phenomena and potential application value in TMDs. Boron nitride has a larger band gap to 6 eV, corresponding to the deep ultraviolet band, belongs to two-dimensional insulator materials, substrate having better dielectric properties and the atomic level, is a good protective layer of other two-dimensional semiconductor material, can obtain higher shielding scattering electron mobility. With the in-depth study, there are two more dimensional materials Wait for our study found that the nature of the need for the development and utilization of more excellent people better service. This thesis mainly studies the two-dimensional heterostructure materials and photoelectric detection, through the design and fabrication of heterojunction devices, to achieve the overall performance of the new light detection function and improve detector. Currently the most widely studied two-dimensional semiconductor material is mainly transition metal chalcogenides, because the sulfur vacancy is easy to form, which is easy to realize the electron doped transition metal chalcogenides, so most of the n- type semiconductor material.P-n and bipolar junction with the built-in electric field is logic devices and high sensitive optical detection of the most basic needs. There are few p- the two-dimensional material doped transition metal chalcogenides, can form good matching with p-n junction structure, the realization of p- type doping is one of the key to be solved at present. High sensitivity photoelectric detection, p-n junction built-in electric field can effectively reduce the dark current and effective separation of photogenerated carriers. The production of high quality p-n is urgently needed in the field of photoelectric detection. We realize the regulation of the WSe2 carrier type by doping Ta. P- type two-dimensional semiconductor material is the key technology to realize the strong atomic layer thickness p-n. High quality p-n node is based on logic devices and photovoltaic detector. Through the design of p-g-n type heterojunction devices, wide band infrared detection, without band gap properties using graphene, wide band absorption. Usually in graphene photocarrier relatively short life span, the effective realization of fast separation two kinds of carriers can be built under the electric field. The spatial separation can effectively improve the carrier lifetime, while the built-in electric field can effectively reduce the dark current, thereby reducing the noise. Therefore p-g-n high Wide band sensitive photoelectric detection. Infrared in infrared detection has important application value in military and missile tracking. At present, MWIR detectors used to work at low temperature, need to increase the cost of using liquid nitrogen refrigeration, and harsh conditions not conducive to convenient use. There is an urgent need to develop and research the medium wave infrared detector at room temperature is convenient application of narrow band gap b-AsP FET and b-AsP-MoS2 heterojunction high sensitive infrared detection at room temperature. In the narrow band gap of two-dimensional layered materials such as PtSe2 and devices used to do some exploration. In the third chapter, we first design a p-g-n type heterojunction wide band photodetector. With Raman (Raman), light the photoluminescence (PL), atomic force microscopy (AFM) and the quality of the film layers of samples and optical microscope were characterized by micro area fixed transfer technology, realize multi different Production quality node devices. With larger work function metals, such as palladium, platinum, gold, p- type doping control WSe2. The Fermi level pinning and strong MoS2 well formed p-n junction. The middle layer graphene without band gap can effectively extend the response bandwidth. At the same time heterogeneous p-g-n nodes can also use the high mobility of graphene as a transparent electrode, separate the carrier separation after. Through the design of the p-g-n heterojunction, we detect from the wide band 400nm-2400nm detection band at room temperature. The photoelectric response rate is as high as 4250AW-1, the ratio of detection up to 1015 Jones. these high sensitive optical detection of light can be realized current imaging, high resolution image is obtained. At the same time we also studied the photoelectric response mechanism, through the visible and near-infrared imaging devices that our current space, the light response is mainly from the p-g-n The junction electric field. In addition, the back gate bias voltage and modulation has better effect on photoelectric response. In the fourth chapter, we deeply study the narrow band gap, black arsenic phosphorus alloy high mobility (b-As0.83P0.17) field effect devices and black phosphorus arsenic alloy and molybdenum sulfide (b-Aso.83P0.17-MoS2) heterojunction device of medium wave infrared detection the mechanism of performance. Focus on b-As0.83P0.17 FET devices from visible to infrared photoelectric response, the photovoltaic effect is the main mechanism of infrared photoelectric detection. By doping in black phosphorus arsenic and arsenic in material composition regulation, black arsenic phosphorus samples with arsenic doped 83%. Through the sample absorption spectrum the study found that the band gap of b-As0.83Po.17 ~ 0.15 eV, detection wavelength optical absorption edge at 1250 cm-1. detection from visible to infrared 400 nm-8.05 um. we studied b-As0.83P0.17-M The photoelectric response of oS2 heterojunction heterojunction, effectively reduce the dark current. Also we study the noise spectrum in heterojunction devices, heterojunction device noise power ratio b-As0.83P0.17 FET noise power density is two orders of magnitude. This shows that the heterojunction device can effectively reduce the dark current and noise power, effectively improve the sensitivity of the device. At the same time, b-As0.83P0.17 samples with strong anisotropic electrical and photoelectric response, and polarization angle on polarized light sensitive dependence. We obtained b-AS0.83P0.17 field effect devices than the detection rate in the band 400 nm-8.05 um higher than 108 Jones. for heterojunction devices from 400 nm-4.3 um than the detection rate is higher than the 4.9 x 109 Jones. fifth new transition metal chalcogenides growth and exploration of narrow gap material synthesis mainly consists of the following parts, the Through the implementation of Ta doped, the intrinsic P- type WSe2; second, CVT synthesis of WSe2 nanowires; third, to explore the growth of synthesis of narrow band gap of low dimensional materials, including black phosphorus doped samples, CVT method and PtSe2 CVD method for growth of narrow band gap metal selenide platinum obtained by PtSe2. CVT WSe2 single crystals were grown by p- Ta doped, p- type with good conductive properties. Through the micro point preparation of transfer Ta0.01W0.99Se2-MoS2 heterostructure and Tao.01W0.99Se2-WSe2 homojunctions, these devices exhibit ideal diode performance, ideal factor rectification ratio reached 105. ~ 1, photoelectric response experiments prove that the heterojunction interface quality. Good cooperation in the group of new the two-dimensional material heterojunction ReS2-BN high sensitive weak light detector and WSe2-graphene heterojunction photodetectors exhibit good photoelectric response. In the last chapter, we sum up in front of the Some important results are discussed and analyzed for the progress and problems currently facing, and we hope that we can continue to push ahead with the unfinished work and make greater contributions to the research direction of two-dimensional material photoelectric detection.

【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TN15

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