硅纳米线的掺杂工艺与检测

掺杂硅纳米线有可能成为一种重要的硅纳米电子器件材料。因而,硅纳米线的掺杂工艺与检测很重要。半导体的掺杂工艺主要为扩散法,而硅纳米半导体线的掺杂检测方法主要包括电流-电压法、拉曼光谱、光致发光(PL)光谱、X-射线光电子能谱(XPS)及近边X-射线吸收精细结构光谱(NEXAFS)等。该文介绍了可引入到硅纳米线研究的现有半导体的掺杂工艺及检测方法,并就硅纳米线的掺杂工艺及检测的最新进展做作了详细的讨论。     

Novel Type‐II InAs/AlSb Core–Shell Nanowires and Their Enhanced Negative Photocurrent for Efficient Photodetection

The control of optical and transport properties of semiconductor heterostructures is crucial for engineering new nanoscale photonic and electrical devices with diverse functions. Core–shell nanowires are evident examples of how tailoring the structure, i.e., the shell layer, plays a key role in the device performance. However, III–V semiconductors bandgap tuning has not yet been fully explored in nanowires. Here, a novel InAs/AlSb core–shell nanowire heterostructure is reported grown by molecular beam epitaxy and its application for room temperature infrared photodetection. The core–shell nanowires are dislocation‐free with small chemical intermixing at the interfaces. They also exhibit remarkable radiative emission efficiency, which is attributed to efficient surface passivation and quantum confinement induced by the shell. A high‐performance core–shell nanowire phototransistor is also demonstrated with negative photoresponse. In comparison with simple InAs nanowire phototransistor, the core–shell nanowire phototransistor has a dark current two orders of magnitude smaller and a sixfold improvement in photocurrent signal‐to‐noise ratio. The main factors for the improved photodetector performance are the surface passivation, the oxide in the AlSb shell and the type‐II bandgap alignment. The study demonstrates the potential of type‐II core–shell nanowires for the next generation of photodetectors on silicon.     

激光烧蚀法制备半导体纳米丝的研究进展

简要介绍了当前国内外激光烧蚀法制备半导体纳米丝的研究现状。介绍了目前激光烧蚀法制备的实验装置及所采用的激光束参数。比较了不同实验结果中在纳米丝结构和生长方向等方面的差异，并分析了半导体纳米丝生长的VLS金属催化机理和氧化物辅助生长模型，我们认为Si-金属混合物作靶时金属催化作用对纳米丝的生长起主要作用，而在Si-氧化物混合物作靶时，氧化物辅助作用将占主导地位。     

硅纳米线纳米器件的研究进展

硅纳米线作为一类重要的一维半导体纳米材料,在纳米器件方面具有很好的应用前景,可以用于高性能场效应晶体管、单电子探测器和场发射显示器件等纳米器件的制备.介绍了近两年来硅纳米线作为检测细胞、葡萄糖、过氧化氢、牛类血清蛋白和DNA杂交方面的纳米传感器、纳米晶体管、光电探测器等纳米器件的最新进展,并对其研究前景做了展望.     

硅基Ⅲ-Ⅴ族纳米线及其若干半导体器件

综述了硅基Ⅲ-Ⅴ族纳米线与异质结制备技术的研究进展.针对基于Ⅲ-Ⅴ族纳米线的半导体器件,重点介绍了硅基Ⅲ-Ⅴ族纳米线场效应晶体管的研究现状,详细介绍了硅基Ⅲ-Ⅴ族纳米线场效应晶体管和隧穿场效应晶体管的制备流程、工艺技术和器件的电学性能,并对影响器件电学性能的因素进行了分析.概括介绍了硅基Ⅲ-Ⅴ族纳米线激光器和硅基Ⅲ-Ⅴ族纳米线太阳电池的研究成果,基于硅衬底的Ⅲ-Ⅴ族纳米线太阳电池为低成本、高效能的太阳电池领域开辟了新途径.研究结果表明,采用硅基Ⅲ-Ⅴ族纳米线制备的场效应晶体管、激光器及太阳电池等半导体器件相对于Si,Ge等传统半导体材料制备的器件有着巨大的优势,在未来集成电路技术中具有越来越大的影响力.     

锗纳米线的性能与应用

重点分析讨论了锗纳米线在电学、光学、光电导等特性及其在场效应晶体管制造方面的研究应用现状与最新进展。综合分析表明,未经处理的锗纳米线表面存在一层氧化物及缺陷,与电极连接时欧姆接触性能较差,在制备锗纳米线器件以前必须对锗纳米线表面进行钝化以便沉积电极;对锗纳米线进行掺杂可以改善Ge纳米线的性能,制造出实用Ge纳米线器件。指出在一根纳米线上生长硅/锗半导体纳米线形成硅/锗半导体界面,直接用单根纳米线制造具有完整功能的电子器件是将来重要的研究方向。     

III–V semiconductor nanowires for optoelectronic device applications

Semiconductor nanowires have recently emerged as a new class of materials with significant potential to reveal new fundamental physics and to propel new applications in quantum electronic and optoelectronic devices. Semiconductor nanowires show exceptional promise as nanostructured materials for exploring physics in reduced dimensions and in complex geometries, as well as in one-dimensional nanowire devices. They are compatible with existing semiconductor technologies and can be tailored into unique axial and radial heterostructures. In this contribution we review the recent efforts of our international collaboration which have resulted in significant advances in the growth of exceptionally high quality III–V nanowires and nanowire heterostructures, and major developments in understanding the electronic energy landscapes of these nanowires and the dynamics of carriers in these nanowires using photoluminescence, time-resolved photoluminescence and terahertz conductivity spectroscopy.     

Orientation‐Controlled Selective‐Area Epitaxy of III–V Nanowires on (001) Silicon for Silicon Photonics

Monolithic integration of III–V nanowires on silicon platforms has been regarded as a promising building block for many on‐chip optoelectronic, nanophotonic, and electronic applications. Although great advances have been made from fundamental material engineering to realizing functional devices, one of the remaining challenges for on‐chip applications is that the growth direction of nanowires on Si(001) substrates is difficult to control. Here, catalyst‐free selective‐area epitaxy of nanowires on (001)‐oriented silicon‐on‐insulator (SOI) substrates with the nanowires aligned to desired directions is proposed and demonstrated. This is enabled by exposing {111} planes on (001) substrates using wet chemical etching, followed by growing nanowires on the exposed planes. The formation of nanowire array‐based bottom‐up photonic crystal cavities on SOI(001) and their coupling to silicon waveguides and grating couplers, which support the feasibility for on‐chip photonic applications are demonstrated. The proposed method of integrating position‐ and orientation‐controllable nanowires on Si(001) provides a new degree of freedom in combining functional and ultracompact III–V devices with mature silicon platforms.     

ZnSe–Si Bi‐coaxial Nanowire Heterostructures

We report on the fabrication, structural characterization, and luminescence properties of ZnSe/Si bi‐coaxial nanowire heterostructures. Uniform ZnSe/Si bi‐coaxial nanowire heterostructures are grown on silicon substrates by the simple one‐step thermal evaporation of ZnSe powder in the presence of hydrogen. Both ZnSe and silicon are single‐crystalline in the bi‐coaxial nanowire heterostructures, and there is a sharp interface along the nanowire axial direction. Furthermore, secondary nanostructures of either ZnSe nanobrushes or a SiO_x sheath are also grown on the primary bi‐coaxial nanowires, depending on the ratio of the source materials. The experimental evidence strongly suggests that bi‐coaxial nanowires are formed via a co‐growth mechanism, that is, ZnSe terminates specific surfaces of silicon and leads to anisotropic, one‐dimensional silicon growth, which simultaneously serves as preferential nucleation sites for ZnSe, resulting in the bi‐coaxial nanowire heterostructures. In addition, the optical properties of ZnSe/Si nanowires are investigated using low‐temperature photoluminescence spectroscopy.     

Nanowire Transistor Performance Limits and Applications

Semiconductor nanowires represent unique materials for exploring phenomena at the nanoscale. Developments in nanowire growth have led to the demonstration of a wide range of nanowire materials with precise control of composition, morphology, and electrical properties, and it is believed that this excellent control together with small channel size could yield device performance exceeding that obtained using top–down techniques. Here, we review advances in chemically synthesized semiconductor nanowires as nanoelectronic devices. We first introduce basic nanowire field-effect transistor structures and review results obtained from both p- and n-channel homogeneous composition nanowires. Second, we describe nanowire heterostructures, show that by using nanowire heterostructures, several limiting factors in homogeneous nanowire devices can be mitigated, and demonstrate that nanowire transistor performance can reach the ballistic limit and exceed state-of-the-art planar devices. Third, we discuss basic methods for organization of nanowires necessary for fabricating arrays of device and circuits. Fourth, we introduce the concept of crossbar nanowire circuits, discuss results for both transistor and nonvolatile switch devices, and describe unique approaches for multiplexing/demultiplexing enabled by synthetically coded nanowire. Fifth, we discuss the unique application of thin-film nanowire transistor arrays on low-cost substrates and illustrate this with results for relatively high-frequency ring oscillators and completely transparent device arrays. Finally, we describe 3-D heterogeneous integration that is uniquely enabled by multifunctional nanowires within a bottom–up approach.      

基于半导体纳米线的环形激光器

针对微光电子机械系统(MOMES)传感器件对微型片上光源的需求与当前半导体纳米线结构制备的进展,设计了一种基于Ⅱ-Ⅵ族半导体纳米线的激光器.将生长出来的纳米线在纯净水中超声制备均匀分布的悬浊液,再滴至载玻片表面,在显微镜50×物镜下观测得到纳米线呈现稀疏分布,约2～3根,选择尺寸较长的纳米线作为制备环形谐振腔的材料.首...     

An Evanescent Coupling Approach for Optical Characterization of ZnO Nanowires

使用纳米氧化硅光纤探针,利用倏逝波耦合方法,将紫外到红外的激光成功地耦合进单根ZnO纳米线,耦合效率可达25%.实验观测了单根纳米线的荧光特性,发现ZnO纳米线光传输损耗很低.研究证明:采用透镜聚焦激发纳米线发光的传统耦合方法,只能使用特殊激发波长的光;而倏逝波耦合方法具有高效、适用性强的特点,在半导体纳米线和纳米带的光学特性研究中有广泛的应用前景.     

Title: Using Alignment and 2D Network Simulations to Study Charge Transport Through Doped ZnO Nanowire Thin Film Electrodes

Factors affecting charge transport through ZnO nanowire mat films were studied by aligning ZnO nanowires on substrates and coupling experimental measurements with 2D nanowire network simulations. Gallium doped ZnO nanowires were aligned on thermally oxidized silicon wafer by shearing a nanowire dispersion in ethanol. Sheet resistances of nanowire thin films that had current flowing parallel to nanowire alignment direction were compared to thin films that had current flowing perpendicular to nanowire alignment direction. Perpendicular devices showed ～5 fold greater sheet resistance than parallel devices supporting the hypothesis that aligning nanowires would increase conductivity of ZnO nanowire electrodes. 2‐D nanowire network simulations of thin films showed that the device sheet resistance was dominated by inter‐wire contact resistance. For a given resistivity of ZnO nanowires, the thin film electrodes would have the lowest possible sheet resistance if the inter‐wire contact resistance was one order of magnitude lower than the single nanowire resistance. Simulations suggest that the conductivity of such thin film devices could be further enhanced by using longer nanowires.     

ZnO纳米线光学特性测试的倏逝波耦合

使用纳米氧化硅光纤探针,利用倏逝波耦合方法,将紫外到红外的激光成功地耦合进单根ZnO纳米线,耦合效率可达25%.实验观测了单根纳米线的荧光特性,发现ZnO纳米线光传输损耗很低.研究证明:采用透镜聚焦激发纳米线发光的传统耦合方法,只能使用特殊激发波长的光;而倏逝波耦合方法具有高效、适用性强的特点,在半导体纳米线和纳米带的光学特性研究中有广泛的应用前景.     

Top down fabrication of long silicon nanowire devices by means of lateral oxidation

The process for the fabrication of devices based on a single silicon nanowire with a triangular section is presented and discussed. The top down fabrication process exploits the properties of silicon anisotropic etching for the realization of very regular trapezoidal structures, that can be uniformly reduced in controlled way by means of lateral oxidation. This allows the reproducible realization of nanowires smaller than 20 nm, and with a length of several micrometers, starting from relatively big structures that, even if electron beam lithography has been used in the present work, could be realized also by other (as optical) lithographic techniques. Nanowires are already placed between silicon contacts for electrical transport characterization. The process, compatible with the actual MOS technology, is suitable for a massive, large-scale production of silicon nanowire based devices and it allows a flexible platform for multigate and more complex structures and devices. The nanowire triangular section is a step toward the integration of three-dimensional devices. Electrical characteristics of silicon nanowire FETs, both p- and n-doped, will be reported and discussed.     

纳米线、纳米管器件在逻辑电路中的应用

本文报导了几种以碳纳米管和半导体纳米线为基础的电子器件和逻辑电路，如：碳纳米管场效应管、纳米线逻辑门电路等。同时，通过比较传统半导体器件和纳米器件，分析了这些纳米器件的特点。在室温下，这几种纳米电子器件和电路均有良好的电学特性。     

Lateral growth and shape of semiconductor nanowires

The lateral growth of semiconductor nanowires and its influence on the nanowire shape in the case of nanocrystal formation according to the diffusion mechanism is theoretically studied. Possible types of the dependence of the adatom concentration at the lateral faces of the nanowires on the vertical coordinate are found. A self-consistent model is developed within the linear approximation in the adatom concentration, which makes it possible to describe simultaneously both vertical and lateral nanowire growth. The possible shapes of the nanowires, depending on the growth conditions, are described within this model and compared with the experimental data on different III–V systems.     

Dual layer semiconducting nanocomposite of silicon nanowire and polythiophene for organic-based field effect transistors

We investigate a dual layer active channel of random distributed intrinsic silicon nanowires and solution processing semiconducting polythiophene polymers for organic-based field effect transistors. Primary results show that low density silicon nanowire networks could enhance the effective charge carrier mobility of polythiophene transistors by a factor of six, suggesting that these nanowires act as rapid one-dimensional charge transport bridges in the active channel. Moreover, increasing the nanowire loading in the dual layer nanocomposite could further lessen the transistor hysteresis. The lifetime test of nanowire-polythiophene devices is found to be more sustainable with respect to that of pristine polythiophene in ambient air. These results indicate that semiconducting nanowires should be considered as a viable additive to active channel for next-generation organic field effect transistors.     

Nanowire and nanohole silicon solar cells: a thorough optoelectronic evaluation

Photovoltaic devices with nanostructured active layers have attracted considerable attention for their outstanding light‐trapping capability. Although with the promise of an efficient light‐conversion, the realistic performance is still far from expectation. This is because the detailed electrical mechanisms have seldom been included into the design, leading to a substantial discrepancy between prediction and reality. This paper reports a complete optoelectronic simulation for nanowire and nanohole solar cells by addressing electromagnetic and carrier‐transport response in a coupled finite‐element method. The effects of surface/bulk recombination are quantified and compared for nanowire and nanohole solar cells with radial and axial doping profiles. Our results reveal that the axially doped silicon cells are extremely sensitive to surface recombination because of the large surface‐to‐volume ratio and lateral recombination loss, eventually reducing the photocurrent and light‐conversion efficiency. Relatively, radially doped silicon cells with a moderate nanowire length show some improvement relative to axially doped cells, but nevertheless remain very sensitive to recombination losses. Comparison of the light‐trapping and electrical performance between nanowire and nanohole solar cells is also given. The methodology is applicable for nanostructured solar cells based on various semiconductor materials and system configurations, and is expected to play a promising role in accurately predicting the performance of the new‐generation light‐conversion devices. Copyright © 2015 John Wiley & Sons, Ltd.     

The Ferroelectric Field Effect within an Integrated Core/Shell Nanowire

The synthesis of cylindrical silicon‐core and ferroelectric oxide perovskite‐shell nanowires and their response characteristics as individual three‐terminal nanoscale electronic devices is reported. The co‐axial nanowire geometry facilitates large ferroelectric field‐effect modulation (>10⁴) of nanowire conductivity following sequential application and removal of an applied dc field. Source‐drain current–voltage traces collected during sweeps of ferroelectric gate potential and switching of the component of shell outward and inward polarization provide direct evidence of ferroelectric coupling on nanowire channel conductance. Despite a very small (1:20) ferroelectric‐to‐semiconductor channel thickness ratio, an unexpectedly strong electrostatic coupling of ferroelectric polarization to channel conductance is observed because of the co‐axial gate geometry and curvature‐induced strain enhancement of ferroelectric polarization.