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Investigation of carrier transport in semiconductor nanowires by scanning probe techniques.

机译：通过扫描探针技术研究半导体纳米线中的载流子传输。

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摘要

In this work, electron beam induced current (EBIC) and scanning photocurrent microscopy (SPCM) were used to quantitatively investigate the electronic properties of silicon nanowire devices. For the first time, it was shown that minority carrier diffusion lengths in phosphorous-doped silicon nanowires are significantly reduced from their bulk values because of nonradiative recombination at the nanowire surface. Diffusion lengths were measured quantitatively by EBIC analysis of nanowire Schottky diodes.;SPCM analysis of two-terminal ohmic n-type silicon nanowire devices revealed a nonuniform electric field along the channel length suggesting an increased resistivity toward the nanowire tip. Etching of the nanowire surface eliminated the gradient indicating that the origin was a surface doping profile. Using four-terminal device geometries, it was shown that quantitative one-dimensional potential profiles and effective carrier concentrations may be obtained. The surface etching process was also used to fabricate high-performance n-Si nanowire FETs that operate based on the n+-n junctions introduced by the etch. SPCM confirms that, in the subthreshold regime, the dominant resistance in the device becomes the n+-n junctions at the edges of the etched region while in the on-state modulation of the carrier concentration in the etched channel determines the device transfer characteristics.;The effect of nanowire nonuniformity on FET performance was investigated using tapered boron-doped silicon nanowires. The transistor threshold voltages and subthreshold slopes were shown to change monotonically along the length of the nanowire with improved transistor characteristics at the tip. SPCM analysis indicated the relative contribution from contact resistance increased toward the nanowire tip where the carrier concentration is reduced in the absence of significant surface doping.;A combination of current-voltage analysis and SPCM was used to investigate silicon nanowire Schottky diodes. Schottky barrier properties obtained by the two methods show good agreement and were used to estimate the internal electric field at the metal-semiconductor junction as well as the effective carrier concentration of the semiconductor.
机译：在这项工作中，电子束感应电流（EBIC）和扫描光电流显微镜（SPCM）用于定量研究硅纳米线器件的电子性能。首次表明，由于纳米线表面的非辐射复合，磷掺杂的硅纳米线中的少数载流子扩散长度从其体值显着降低。扩散长度通过纳米线肖特基二极管的EBIC分析进行定量测量;;对两端欧姆n型硅纳米线器件的SPCM分析显示，沿着沟道长度的电场不均匀，表明朝向纳米线尖端的电阻率增加。纳米线表面的蚀刻消除了梯度，表明起点是表面掺杂轮廓。使用四端子装置的几何形状，已表明可以获得定量的一维电势分布和有效载流子浓度。表面蚀刻工艺还用于制造基于蚀刻引入的n + -n结而工作的高性能n-Si纳米线FET。 SPCM证实，在亚阈值范围内，器件中的主要电阻变为蚀刻区域边缘的n + -n结，而在蚀刻通道中载流子浓度的导通状态调制中确定器件的传输特性。使用锥形掺硼硅纳米线研究了纳米线不均匀性对FET性能的影响。晶体管阈值电压和亚阈值斜率显示为沿着纳米线的长度单调变化，尖端的晶体管特性得到改善。 SPCM分析表明，在没有明显的表面掺杂的情况下，接触电阻朝着纳米线尖端增加的相对贡献，在纳米线尖端，载流子浓度降低了；电流电压分析和SPCM的组合被用于研究硅纳米线肖特基二极管。通过两种方法获得的肖特基势垒性能显示出良好的一致性，并被用于估算金属-半导体结处的内部电场以及半导体的有效载流子浓度。

著录项

  • 作者

    Allen, Jonathan E.;

  • 作者单位

    Northwestern University.;

  • 授予单位 Northwestern University.;
  • 学科 Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2008
  • 页码 191 p.
  • 总页数 191
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 工程材料学;
  • 关键词

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