梁啟德臺灣大學：物理研究所黃健哲Huang, Jian-ZheJian-ZheHuang2007-11-262018-06-282007-11-262018-06-282007http://ntur.lib.ntu.edu.tw//handle/246246/54534Abstract This thesis describes the measurements on the low-temperature electron transport properties in a two-dimensional GaN electron system. This thesis consists of the following two parts: 1. Electron-electron interaction in a perpendicular magnetic field: We report on experimental studies of Al0.15Ga0.85N/GaN high electron mobility transistor (HEMT) structures grown on p-type Si (111) substrates. By introducing an ultra thin SiN layer during the crystal growth, the Hall mobility of the HEMT structure can be greatly enhanced (>3 times). This SiN treatment technique also allows the observation of Shubnikov-de Haas oscillations which is not possible in the untreated HEMT structure. Our experimental results pave way to integration of AlxGa1-xN/GaN HEMT structures with the mature Si technology in industry. 2. Weak localization effect in a perpendicular magnetic field: We can illustrate weak localization by the constructive interference of wave functions which back to the origin after transmitting along time-reversed paths. Electrons will be localized by weal localization. The dephasing time , which determines the time scale kept the constructive interference of wave functions, limits the length of the time-reversed paths. It is known that weak localization causes a negative magnetoresistivity.Contents Chapter 1. Introduction 1 1.1 Two-dimensional electron gas in an AlGaN/GaN heterostructure………………………………………………………...1 1.1.1 The properties of two-dimensional electron gas………………………………1 1.1.2 GaN/AlGaN electron system…………………………………………………..3 1.2 Density of states………………………………………………..…....8 1.2.1 Density of states for a three-dimensional system…………………………….11 1.2.2 Density of states for a two-dimensional system……………………………...13 1.3 References………………………………………………………….15 Chapter 2. Theoretical background 16 2.1 Weak localization……………………………………………………16 2.2 Electron-electron interaction………………………………………..18 2.3 Classical Hall effect…………………………………………………22 2.4 Landau levels and Shubnikov-de Haas oscillations………………...24 2.5 Quantum Hall effect………………………………………………...27 2.6 References…………………………………………………………..31 Chapter 3. Sample Fabrication and Experimental techniques 32 3.1 Sample fabrication…………………………………………………..32 3.2 HelioxTL system……………………………………………………..34 3.3 HelioxTL inserts……………………………………………………...35 3.4 Four-terminal resistance measurements…………………………….36 3.5 References…………………………………………………………..38 Chapter 4. Electron-Electron Interactions in a Two-Dimensional Electron System in an Al0.15Ga0.85N/GaN Heterostructure…………….39 4.1 Introduction…………………………………………………………39 4.2 Theory……………………………………………………………….41 4.3 Experiment………………………………………………………….44 4.4 Results and Discussions…………………………………………….45 4.5 Conclusion…………………………………………………………..53 4.6 References…………………………………………………………..54 Chapter 5. Weak Localization in a Two-Dimensional Electron System in an Al0.15Ga0.85N/GaN Heterostructure 57 5.1 Introduction…………………………………………………………57 5.2 Theory………………………………………………………………58 5.3 Experiment………………………………………………………….64 5.4 Results and Discussions…………………………………………….65 5.5 Conclusion…………………………………………………………..68 5.6 References…………………………………………………………..70 Chapter 6. Conclusions 72en-US二維電子氮化鎵2DESGaNthesis