量子點雷射之研究

Abstract

以量子點當作主動層的半導體雷射，稱為量子點雷射，由於是三維方向都被侷限的形況，理論上會有分離(discrete)的能態密度，有很高的差動增益(differential gain)，所以我們可以預期量子點雷射會有很低的起始電流，很高的特徵溫度，很窄的光譜，和很大的調變頻寬，有很好的雷射特性。 本實驗我們以InAs/GaAs材料拿來做成自聚性的量子點，實驗主要研究了基底厚度對光頻譜的影響，實際上量子點雷射的頻譜是非常複雜的，有了這樣的一個認知，我們能夠在去除基底厚度對頻譜的影響條件下，再更進一步深入的的研究量子點頻譜的特性。且量子點雷射對溫度及電流也極為敏感，這也是值得研究的，同時藉由量測雷射其他特性的變化，能更進一步了解複雜的量子點結構。

The quantum-dot lasers are semiconductor lasers which use Quantum-dot as their active region medium. Because electrons in quantum-dots are confined in three dimensions and have discrete energy density of state theoretically , quantum dot lasers are predicted to have very low threshold current density , high characteristic temperature and narrow bandwith ..etc. In this paper , we mainly investgate the effect of the thickness of the GaAs substrste to quantum dot lasers . Besides, we investgate the factors which affect the characters of QD lasers like cavity length and temperature..etc. The results indicate that the dominant mechanism leading to the regular modulation of the emission spectra in these quantum-dot lasers is related to the device thickness,although there some additional features present in some of the measured spectra that do not appear to be related to the cavity length or thickness. It may be that in quantum-dot devices where substrate effects are suppressed that other mechanism cause regular or quasiregular mode distribution.