應變矽/矽鍺量子井之磁光效應研究

Abstract

近年來，應變矽/矽鍺異質接面在高速元件及光電元件中已經有了重要的應用。然而，對於有些基本的材料特性還不是很清楚，像是應變所帶來的複雜能帶結構改變，使得定義能帶接面變的相當困難。在光電元件應用上，因為不同的震盪耦合，第一型或第二型能帶接面對元件光電效率有相當大的影響。在本篇論文中，我們對不同應變分佈下的應變矽/矽鍺多量子井結構做了磁光實驗，在磁場下，量子井的光學訊號開始移動。從磁場下的能量移動，兩種形式的激子都被觀察到。我們也做了磁場下迴旋能及黎曼效應的理論模擬，發現與實驗結果相當一致。所以我們認為，只要能夠適當的調整應變分布及鍺含量，我們可以製造出第一型異質接面，進而擁有更好的光電特性。

Strained Si/SiGe heterostructure has attracted great attention recently for its application in high speed and optoelectronic devises. However, the basic parameters such as band alignment are still not so clear due to the complexity of the band shifting and splitting as a result of strain effect between Si/SiGe lattice mismatch. For optoelectronic applications, band alignment (type-I and type-II) with different oscillation strength can cause extreme different optical transition efficiency. In this thesis, magneto-luminescence measurement was performed for Si/SiGe multi-quantum wells with different strain distribution. Under magnetic fields, the transitions associated with quantum well begin to shift. From the behavior of energy shifting, two kinds of excitons (type-I and type-II) are observed. Theoretical modeling of the diamagnetic shifting both considering cyclotron energy and Zeeman effect was performed, and the agreement between observation and calculation is quite well. With a proper strain manipulation, it is possible to form type-I band alignment which in principle has larger oscillation strength for more efficient light emission than the type-II alignment.