砷化銦量子點尺寸與能階躍遷之研究

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

陳佳慶(Chia-Ching Chen)

指導教授 ： 詹國禎

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2004年)

https://doi.org/10.6342/NTU.2004.00936

摘要

本論文探討三種不同結構的固態分子束磊晶成長的自我組成砷化銦量子點，作為本論文主軸。我們利用光調制反射率光譜實驗來探索各樣品中量子點在50 K下的光學能階特性。同時利用雷射必v變化之光致螢光光譜實驗可以找出基態與激發態的躍遷能階，進一步可以吻合至光調制反射率光譜上。我們也以掃描式電子顯微術(scanning electron microscope；SEM)與原子力式顯微鏡(atomic force microscope ,AFM)來觀測量子點2D與3D的形態，進而推估出量子點尺寸的分布情形，以了解躍遷能階與量子點大小的關係。我們進行溫度低溫至室溫之光致螢光光譜實驗可以發現，能階隨著溫度上升會有紅移現象，特別是當量子點覆誘FInGaAs(9ML)，將使量子點能階比未覆貌漣C、同時半高寬縮減，隨著溫度變化分布的情況可以發現樣品A、B與C的第一群基態之半高全寬值幾乎不隨著溫度改變而產生變化，是因為熱效應所造成的響應。反觀當有第二群量子點時，則溫度超過200K後而有逐漸下降的趨勢。利用熱效應使得載子在高能階的量子點不容易被侷限住而放光，反而會脫離出去後，再重新分布來加以解釋此現象。

關鍵字

光致螢光光譜術 ； 量子點 ； 光調制反射率光譜術 ； 砷化銦�砷化鎵 ； 原子力顯微術

並列摘要

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.

並列關鍵字

PR ； PL ； quantum dots ； AFM

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