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The role of planar symmetry and scattering-enhanced tunneling in resonant transport.

机译：平面对称和散射增强隧穿在共振传输中的作用。

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摘要

Although there has been active research on resonant transport in planar semiconductor structures for more than 30 years, there still is no general framework for understanding when resonant transport will dominate a structure. Here we present the development of such a framework.;Our technique is based on capacitance-voltage spectroscopy, and it allows us to directly determine whether the transport is dominated by resonant, momentum-conserved tunneling or scattering-enhanced tunneling. We measure the timeconstant associated with tunneling in and out of a given 2D system, and we relate this timeconstant to the quasi-bound state lifetime. The key feature of our method is the ability to measure the lifetime while varying the energy of the quasi-bound state. This is achieved by applying a DC bias to the sample and varying the carrier concentration of the two-dimensional electron gas. The response of the lifetime to changes in DC bias indicates which transport mechanism dominates in a given device. By measuring the transport characteristics of several different sample structures, we are able to determine which structures are more or less sensitive to disrupted planar symmetry and scattering-enhanced tunneling.;Within certain sample structures, the dominant transport mechanism can switch from resonant tunneling to scattering-enhanced tunneling. One way to cause this change is by varying the carrier concentration within the two-dimensional electron gas. A less obvious way is to apply a magnetic field perpendicular to the layers. Increasing the magnetic field sweeps the chemical potential alternately through the cyclotron orbitals of Landau Levels and the edge states that surround defects. As the chemical potential crosses a Landau Level, the quasi-bound state lifetime jumps by nearly two orders of magnitude. This, we suggest, is a planar-tunneling analogue of the Integer Quantum Hall effect.;After identifying the relevant sample parameters, a simple scaling allows us to map out a diagram of transport regimes dominated by resonant or scattering-enhanced tunneling. This provides a simple framework to predict which mechanism will dominate in a given sample and which sample structures provide the most robust resonant-tunneling dominated transport.
机译：尽管人们已经对平面半导体结构中的共振传输进行了积极的研究超过30年，但仍没有一个普遍的框架来理解何时共振传输将主导结构。在这里，我们介绍这种框架的开发。我们的技术基于电容-电压谱，它使我们能够直接确定传输是由共振，动量守恒的隧穿还是散射增强的隧道主导。我们测量与进入和退出给定2D系统的隧道关联的时间常数，并将该时间常数与准绑定状态寿命相关联。我们方法的关键特征是能够在改变准约束态能量的同时测量寿命。这是通过向样品施加直流偏置并改变二维电子气的载流子浓度来实现的。寿命对直流偏置变化的响应表明，在给定器件中，哪种传输机制起主导作用。通过测量几种不同样品结构的传输特性，我们可以确定哪些结构对破坏的平面对称性和散射增强的隧穿或多或少敏感。在某些样品结构中，主要的输运机理可以从共振隧穿转变为散射。增强隧道。引起这种变化的一种方法是通过改变二维电子气中的载流子浓度。一种不太明显的方法是垂直于各层施加磁场。磁场的增加交替通过朗道能级的回旋加速器轨道和围绕缺陷的边缘状态扫掠化学势。当化学势超过朗道能级时，准束缚态寿命将跃升近两个数量级。我们建议，这是整数量子霍尔效应的平面隧道模拟。在确定了相关的样本参数之后，简单的缩放就可以使我们绘制出以共振或散射增强隧穿为主的传输机制图。这提供了一个简单的框架，可以预测在给定样本中哪种机制将占主导地位，以及哪种样本结构将提供最可靠的共振隧道主导的传输。

著录项

  • 作者

    Russell, Kasey Joe.;

  • 作者单位

    Harvard University.;

  • 授予单位 Harvard University.;
  • 学科 Physics Condensed Matter.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 141 p.
  • 总页数 141
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 O49;
  • 关键词

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