鍺錫合金之光學特性與含錫的四族半導體共振穿隧二極體之研究

Optical Characteristics of Ge1-xSnx alloys and Sn-based Group IV Structure for Resonant Tunneling Diode

蔡秉宏(Bing-Hung Tsai)

指導教授 ： 鄭鴻祥

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.10518

摘要

近年來，含有錫的四族半導體材料受到各界的關注，並希望這種材料能夠用來製做新穎的光電元件。加入錫之後，能夠改變IV-IV族半導體合金的能隙，並且有機會讓IV-IV族半導體合金從間接能隙變成直接能隙的材料，提升其光電效率。在此，我們利用低溫分子束磊晶技術，在非平衡狀態下成功的將具有高錫濃度的鍺錫薄膜成長在鍺基板(14%)與矽基板(17%)上，克服了錫在鍺中的低溶解度難題(<1%)。我們更進一步利用傅立葉轉換紅外光譜儀、橢圓儀、及光致螢光光譜儀量測鍺錫合金的光學性質，並分析不同濃度鍺錫樣品的能隙。在傅立葉轉換紅外光譜儀分析中，可以獲得鍺錫樣品的直接能隙位置。並且藉由介電常數ε1 和ε2，
可以獲得能隙臨界點E1、E1+Δ1、及E0’的變化。隨著錫濃度的增加，在E1 和E1+Δ1
的能量位置也隨著往低能量移動。進而我們能夠利用這些鍺錫薄膜的光學性質，
來設計新的光電元件與電子元件。
在理論計算方面，我們也提出利用具有直接能隙的鍺錫IV-IV 族合金來發展新
型的共振穿隧二極體，我們設計了具有直接能隙的鍺錫/矽鍺錫量子井結構，並能
夠直接成長於矽基板上。藉由最佳化量子井結構的成分與應變，可將峰谷值比大
幅的提升至7.96 以上，此結果能夠整合到互補式金氧半導體電路中，並有所運用。

關鍵字

分子束磊晶 ； 鍺錫合金 ； 臨界點 ； 直接能隙 ； 共振穿隧二極體

並列摘要

In a recent development, tin (Sn)-based group-IV semiconductor compounds has attracted research attention for new electronic and photonic devices. The incorporation of Sn modulates the bandgap of the host IV-IV compounds, and, above a certain Sn composition, the energy band of the IV-IV compounds changes from an indirect to a direct band gap. Here, we investigate a series of Ge1-xSnx alloy with various Sn compositions up to 14% and 17% grown on Ge and Si wafer respectively using low-temperature Molecular Beam Epitaxy. To characterize band structure and optical properties of these GeSn samples, we performed spectroscopic Fourier Transform Infra-Red (FTIR), ellipsometer, and photoluminescence (PL) measurements. The Γ-to-Γ optical energy gap of Ge1-xSnx alloys can be determined by FTIR. Several critical point features, corresponding to E1, E1+Δ1, and E0’ transitions, are observed in ε1 and ε2. The
positions of E1 and E1+Δ1 shift toward to lower energy as Sn composition increases.
Furthermore, the optoelectronic and electronic devices can be designed for applications by those analyzed.
We propose a new design of Sn-based group-IV structure for resonant tunneling diode (RTD). The proposed RTD is composed of direct-bandgap Ge1-xSnx/SiyGezSn1-y-z quantum well which can be directly grown on Si. By optimizing the composition and strain in the quantum well, a high peak-to-valley ratio of 7.69 is obtained. Those results suggest our proposed RTD design can be integrated into CMOS circuits for useful applications.

並列關鍵字

MBE ； GeSn alloy ； critical point ； direct band gap ； resonant tunneling diode

參考文獻

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