GaAsSb緩衝層對於InAs/GaAs系統中量子點結構與性質之效應

Abstract

本研究目的在於了解InAs/GaAs系統中GaAsSb緩衝層對InAs量子點的光學及結構性質之影響。以分子束磊晶法(MBE)先成長1nm厚的三組不同Sb濃度的GaAs1-XSbX緩衝層於GaAs基材上，其緩衝層的組成分別為 (X=0%、5.72%、11.44%)，接著成長InAs量子點，最後再成長GaAs覆蓋層於InAs/GaAsSb結構上。利用二次離子質譜儀(SIMS)及附加於TEM的X光能量散佈光譜儀(EDS)分析Sb於量子點結構中的分佈情形；使用光激發光譜(PL)及穿透式電子顯微鏡(TEM)來觀察以先成長GaAsSb緩衝層對InAs量子點光學性質及結構性質的影響。由PL光譜的發光性質可得知量子點的尺寸及分布情形；TEM分析可得知量子點的尺寸及密度。PL的結果發現，成長以GaAsSb做為InAs量子點結構中的緩衝層，造成的發光波長紅移；並由TEM影像觀察得知確實增加了量子點的尺寸，但對於量子點的密度無明顯的改變。此外，本論文亦就光學及結構性質與量子點的尺寸和分布之關係加以討論。

This work studies the effect of GaAsSb buffer layer of different Sb concentrations on the optical and structural properties of InAs quantum dots (QDs) embedded in GaAs. The InAs/GaAs QD structures were grown by molecular beam epitaxy (MBE), which contained the buffers of GaAs1-XSbX (X = 0%, 5.72%, and 11.44%) of 1 nm thickness on the GaAs substrates, and finally capped with a 300-nm-thick GaAs layer. In this thesis, the secondary ion mass spectrometry (SIMS) and energy dispersive X-ray spectroscopy (EDS) were used to investigate the distribution of Sb in the QD structures. Photoluminescence (PL) measurements and transmission electron microscopy (TEM) were performed to investigate the optical and structural properties of QDs. The embedded InAs dots were observed by high-angle annular dark field-scanning TEM (HAADF-STEM). PL spectra show the size and distribution of QDs, and TEM images show that the dots size and density. PL spectra reveal that the GaAsSb buffer layer in InAs QD structures has a wavelength redshift. TEM images exhibit the dots size increases with the concentration of Sb in the buffer layer, but with an insignificant increase in density. There is a further discussion about the relation between the optical and structural properties of QDs and the size and distribution.