Study of Relationship between Size Distribution and Energy Levels in InAs Self-assembled Quantum Dots

• Main Authors: Chia-Ching Chen, 陳佳慶
• Other Authors: 詹國禎
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/03309643155394387167

碩士 === 國立臺灣大學 === 光電工程學研究所 === 92 === In this thesis, we use photoreflectance (PR) and the temperature dependent photoluminescence (PL) techniques to study the optical properties of self-assembled InAs quantum dot (QDs). In the PR experiments, the energy values of the QD optical transitions could be obtained. Compared with PL experiments, we defined clearly the effect of the lower energy levels. In order to understand the relation between the size of quantum dos and energy levels, we use scanning electron microscope (SEM) and atomic force microscope (AFM) to measure the size distribution of quantum dots. At last, we performed the temperature dependent PL experiments to measure optical energy and broadening parameter. In these experiments, we observed that the intensity of ground state decreased with increasing temperature. However, the broadening parameter show different trend with varying temperature. The broadening parameter of the QDs of the first group isn’t affected at different temperature. But, for the second group, the broadening parameter decreased with increasing temperature at low temperature. It’s caused the higher-energy carriers of QDs escape from the confine state and induce repopulation effect. Then, due to lattice vibration, broadening parameter increased from 100 K to 250 K. Finally, it decreased again. It reveals that this abnormal behavior of broadening parameter closely relate to the temperature. In summary, the thermal effect and sample structure play an important role in the optical properties of QDs.