高溫下之巨大正磁阻及電阻率定律

Large positive magnetoresistance and resistivity law at high temperatures

江育廷(Yu-Ting Jiang)

指導教授 ： 梁啟德

國立臺灣大學/理學院/物理研究所/碩士(2006年)

https://doi.org/10.6342/NTU.2006.01365

摘要

無資料

關鍵字

量子霍爾效應 ； 二維電子氣體 ； 電阻率定律

並列摘要

Abstract

This dissertation describes the measurement on the electron transport in two-dimensional GaAs electron systems. We report on the transport properties of electron gas systems of AlGaAs/GaAs heterostructure in the presence of a perpen-dicular magnetic field B.

1. Resistivity law in high-mobility two-dimensional GaAs electron systems:
There are many physical quantities that may be studied in a two-dimensional elec-tron gas (2DEG), and one of the most popular characteristics is magnetoresistance (MR). The two components of quantum Hall transport coefficient ρxx and ρxy in high-mobility 2DEG had been found to be related by ρxx=αB(dρxy /dB), called “resis-tivity law”. The work we do is to study the temperature and mobility effects on scal-ing parameter α at high temperatures in a standard 2DEG system of GaAs/AlGaAs heterostructure. The high mobility samples (sample T475-2 with a mobility μ =239 m2/Vs and sample T479-4 with a mobilityμ =512 m2/Vs at 0.3 K) we used are fab-ricated by molecular beam epitaxy (MBE). The measurement was performed in a top-loading 3He cryostat over the temperature 0.3K~80 K. Four-terminal magnetore-sistance was measured by using standard phase-sensitive lock-in techniques with Hall bar and Ohmic contact technique. We estimate the scaling factor α of the resistivity law at temperature T= 20~80 K under the magnetic field not too low (B> 0.5 T) and find it varying with temperature, consistent with the work of Simon and Halperin in 1994.

2. The explanation and the transport behavior of resistivity law in two-dimensional electron gas system:
Since we have investigated the high-temperature properties of resistivity law in high-mobility 2DEG systems, another work we do is to study resistivity law in a low-mobility 2DEG system. The low-mobility 2DEG system (sample C1335 with a mobility μ=0.804 m2/Vs at T=0.3 K) is formed at the interface of GaAs/AlGaAs heterostructure with self-assemble InAs quantum dots. Furthermore, we discuss the theoretical explanation and details of electron transport of resistivity law that also suggested by Simon and Halperin in 1994. Their argument is based on high-mobility 2DEG systems, i.e. ρxy is much larger than ρxx with percolation network. We compare our result with their conclusion.

並列關鍵字

Quantum Hall Effect ； two-dimensional electron gas ； resistivity law

參考文獻

Chapter 1 Introduction

[1] K. v. Klitzing, G. Dorda, and M. Pepper, Phys. Rev. Lett. 45, 494 (1980).

[3] J. Singh, Physics of Semiconductors and Their Heterostructures, McGraw-Hill (1993)

Chapter 2 Theoretical background

[1] K. von Klitzing, G. Dorda, and M. Pepper, Phys. Rev. Lett. 45, 494 (1980).