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Ballistic transport in two-subband two-dimensional carrier systems at GaAs/AlGaAs heterojunctions.

机译：GaAs / AlGaAs异质结处两子带二维载波系统中的弹道传输。

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摘要

We have investigated ballistic transport phenomena of two-dimensional carrier systems that are confined to AlGaAs/GaAs heterostructures and occupy two electric subbands. Two types of two-subband systems, classified by the origin of their subband splitting, are studied in this thesis. They are the confinement-subband and spin-subband systems. The confinement-subband system studied here is a two-dimensional electron system (2DES) confined to a wide GaAs quantum well with two electric subbands occupied. As for spin-subband systems, a two-dimensional hole system (2DHS) is confined to either an AlGaAs/GaAs interface or a GaAs quantum well with a single occupied confinement-subband. The spin-degeneracy of the single confinement-subband is then lifted, at zero-magnetic field, by the crystal as well as the structural inversion asymmetry of the system. In this thesis, we report the first quantitative study of the 2DHSs evolving from spin-degenerate systems to spin-split systems. The measured spin splitting agrees reasonably well with the results of calculations that employ essentially no adjustable parameters.; We use both the transverse magnetic focusing (TMF) and commensurability oscillations (COs) measurements to study the ballistic transport properties of these two-subband systems in this thesis. We find that a standard TMF device is not able to detect the ballistic transport of upper subband electrons. By adding a tunable barrier, we are able to improve the energy resolution of the simple TMF device and use it to observe the USE ballistic transport. We then demonstrate that COs provide for a more powerful technique for studying ballistic transport. We are able to use COs measurement to deduce the ballistic scattering times for both the upper and the lower subband electrons. We find that the lower subband electrons have longer scattering time and we discuss the dominant scattering processes for both the upper and lower subband electrons. By studying the COs in a spin-subband system, we find clear evidence for spin-resolved ballistic transport.
机译：我们研究了局限于AlGaAs / GaAs异质结构并占据两个电子带的二维载波系统的弹道传输现象。本文研究了两种类型的两子带系统，按子带分割的起源分类。它们是限制子带和自旋子带系统。这里研究的约束子带系统是一个二维电子系统（2DES），被限制在一个宽GaAs量子阱中，并占据两个电子子带。对于自旋子带系统，二维空穴系统（2DHS）被限制在AlGaAs / GaAs界面或具有单个被占用子带的GaAs量子阱中。单个约束子带的自旋简并性随后在零磁场下被晶体以及系统的结构反转不对称性所提升。在本文中，我们报道了从自旋简并系统到自旋分裂系统的2DHS的首次定量研究。所测得的自旋分裂与基本上不采用可调参数的计算结果相当吻合。本文使用横向磁聚焦（TMF）和可比性振荡（COs）测量来研究这两个子带系统的弹道传输特性。我们发现标准的TMF设备无法检测上子带电子的弹道传输。通过添加可调屏障，我们能够提高简单TMF设备的能量分辨率，并使用它来观察USE弹道运输。然后，我们证明CO可以为研究弹道运输提供更强大的技术。我们能够使用COs测量推论上下子带电子的弹道散射时间。我们发现较低的子带电子具有更长的散射时间，并且我们讨论了较高和较低子带电子的主要散射过程。通过研究自旋子带系统中的CO，我们找到了自旋分辨弹道运输的清晰证据。

著录项

  • 作者

    Lu, JengPing.;

  • 作者单位

    Princeton University.;

  • 授予单位 Princeton University.;
  • 学科 Engineering Electronics and Electrical.; Physics Condensed Matter.
  • 学位 Ph.D.
  • 年度 1998
  • 页码 135 p.
  • 总页数 135
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 无线电电子学、电信技术;
  • 关键词

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