New Transport Phenomena from Communication of Multiple Edge Channels

这个实验研究项目集中在量子霍尔效应中位于准二维电子气周长附近的“边缘态”形成的导电系统。从根本上说，对于将多个边缘状态引入通信的样本几何形状，预测了新的传输行为。本项目中将采用两个几何样例。它们是具有在2D表面鞘上传输的边态的GaAs/AlGaAs超晶格柱；以及具有跨过又长又窄的“线栅”势垒的边缘态传输的门控GaAs/AlGaAs异质结。现有的理论预测将通过使用高场(19特斯拉)、低温(20mK)装置在分子束外延生长的GaAs/AlGaAs异质结样品上进行测量来验证。这一结果有望促进人们对准一维和各向异性三维材料中电子输运的全面理解。这个实验研究项目基于微电子学中最先进的器件技术之一--基于GaAsGaAlAs系统的新型器件中的电子输运行为。该系统被用于一些用于计算机的先进电子设备中，因为它可以导致比硅制的同等设备更快的操作。这些实验将基于GaAlAs技术制造的薄导电层，它提供了一种受限的二维“电子气”，其中来自杂质和缺陷的残余散射被减少到极低的水平，从而可以观察到在极低温度和高磁场下的固有电子气行为，并与最近的理论模型进行了比较。这项研究的结果可能包括不同寻常的新效应或材料，可能会在技术上找到新的应用。这项研究项目本质上是跨学科的，涉及将接受良好培训以进入工业、政府或教育职位的研究生。***

w:\awards\awards96\num.doc 9700767 Gwinn This experimental research project focuses on conducting systems formed by the "edge states" that lie near the perimeter of quasi- two dimensional electron gases in the quantum Hall effect (QHE). Fundamentally new transport behavior is predicted for sample geometries that bring multiple edge states into communication. Two sample geometries will employed in this project. These are a GaAs/AlGaAs superlattice pillar with edge states communicating on a 2D surface sheath; and a gated GaAs/AlGaAs heterojunction with edge states communicating across a long, narrow "line gate" barrier. Existing theoretical predictions in these cases will be tested with measurements to be made using a high-field (19Tesla), low temperature (20mK) apparatus on samples fabricated from MBE- grown GaAs/AlGaAs heterostructures. It is expected that the results will advance general understanding of electronic transport in quasi-1D- and in anisotropic 3D- materials. %%% This experimental research project probes electron transport behavior in novel devices based on one of the most advanced device technologies in microelectronics; that based on the GaAs- GaAlAs system. This system is used in some advanced electron devices for computer use because it can lead to faster operation than equivalent devices made of silicon. The experiments will be based on thin conducting layers fabricated in the GaAlAs technology which give a confined two-dimensional "electron gas" in which the residual scattering from impurities and imperfections is reduced to extremely low levels, so that inherent electron gas behavior at very low temperatures and at high magnetic fields can be observed, and compared to recent theoretical models. Results from this research may include unusual new effects or materials which may find new application in tech nology. This research project is interdisciplinary in nature and involves graduate students who will be excellently trained to enter positions in industry, government or education. ***