以分子束磊晶成長矽鍺應變超晶格及其光學性質之研究

Abstract

運用拉曼光譜分析以分子束磊晶成長短週期Si/Si1-xGex應變超晶格之應變弛豫度。探測到幾個來自於虛擬基材、超晶格之矽鍺合金層和超晶格之應變矽晶層的聲子信號，藉分析聲子峰位可求得合金成份比和晶格弛豫度。 基於應變的檢測結果，考慮應變對能帶結構的調制效應，藉以求出樣品的能帶結構，以推論出激子之躍遷能量。經由比對自磁光光譜中觀察到的激子躍遷信號，獲得契合之結果。

The molecular-beam-epitaxial-grown short-period strained-layer Si/Si1-xGex superlattices were examined by Raman spectroscopy. By using several excitation sources, the Raman depth probe reveals the phonon signals from the virtual substrate, the Si1-xGex alloy of superlattices, strained Si-layer of superlattices, and unstrained Si-substrate separately. The Ge composition of virtual substrate and Si1-xGex alloy of superlattices can be determined, and the degree of relaxation of virtual substrate and strained Si-layer are found as well. On the basis of the results of strain examination and consideration for the influence of the band structure, we know that the band structure of the sample belongs to type-II band alignment. It gives the preliminary explanation about the source of exciton transition observed from Magneto-optics spectra.