- 學位論文
砷化銦量子點光學躍遷之量測
Optical characterization of InAs Self-Assembled Quantum Dots
摘要
本論文利用溫變的光致螢光光譜術(photoluminescence)、光調制反射率光譜術(photoreflectance)和光激發的溫度和必v變化的實驗來研究分子束磊晶成長(MBE)的砷化銦(InAs)自我組成量子點的光激發的光學性質。以掃描式電子顯微術(scanning electron microscopy;SEM)和原子力顯微鏡(atomic force microscopy:AFM)來觀測量子點的密度和尺寸大小。樣品中，多了一層砷化銦鎵的緩衝層(buffer layer)會使得量子點的密度增加，也降低了量子點的平均大小。螢光光譜術的實驗中，使用高斯函數吻合，吻合的特徵來自於量子點的光學躍遷(optical transition)，並且可以與光調制光譜術的實驗吻合資料相互做個對應。我們觀察並討論到不尋常且特殊的線寬隨溫度縮窄和光致螢光光譜術的強度隨溫度增強現象。我們認為這種強度增強的現象是由溼層(wetting layer)引起的載子儲存效應所造成的。我們提出載子分佈速率方程式(rate equations)的模型來模擬這一個不規則的溫度變化現象。
並列摘要
The optical properties are researched with temperature dependent photoluminescence (PL) and photoreflectance (PR) and power dependent experiments on MBE grown InAs self-assembled quantum dots. The density and size uniformity of quantum dots was measured by the instrument of scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively. The density and average size of InAs QDs was affected by covering buffer layer of InGaAs. The experiment data was fitted by Gaussian profile in the PL experiment, and the features of the fitted result comes from optical transition of QDs, which correlated with the features observed in the PR spectra. Anomalous temperature dependence of PL in broadening parameter and integrated intensity is also discussed. We attributed the enhancement of PL intensity signal to be carrier releasing from potential fluctuation in the wetting layer (WL). The model of the rate equations was proposed and simulated.