低溫下高成分錫之鍺錫成長研究

Abstract

我們的實驗研究內容為利用分子束磊晶技術，成長厚度超過臨界厚度之鍺錫薄 膜。一系列鍺錫薄膜樣品是於接近錫熔點之低溫條件下，成長於鍺緩衝層之上， 內含最高可達百分之十四之相異的錫成份。特別的是，一層低溫鍺緩衝層被成長 於鍺錫薄膜與鍺基板之間，用以捕捉晶格缺陷。數個量測分析展現了在穿透式電 子顯微鏡橫截面影像裡，鍺錫薄膜幾無缺陷，而且在錫成份低於百分之九點三的 樣品裡錫非常均勻地分布在鍺錫薄膜當中。我們所成長的鍺錫合金內含之錫成分， 超過了理論預測裡鍺可由非直接能隙轉變為直接能隙的錫成分。因此，此份研究 目的為提供一個可成長出直接能隙鍺錫薄膜的方法，亦可被應用於光電元件技術 之中。

We report on experimental investigations of the growth of Ge1-xSnx film with thickness above the critical thickness using Molecular Beam Epitaxy. A series of Ge1-xSnx films with various Sn compositions up to 14% are deposited on a Ge buffer layer for growth at low temperatures close to the melting point of Sn. Especially, a low temperature Ge buffer layer was grown between GeSn film and Ge substrate for trapping defects. Analysis of various measurements shows that the Ge1-xSnx film is defect free in the XTEM image and that Sn is distributed almost uniformly in the film for Sn compositions up to 9.3%. The Sn composition of the films is higher than the Sn composition that is theoretically predicted to cause the energy band of Ge to change from an indirect to a direct bandgap; thus, the present nvestigation provides a method for growing direct bandgap GeSn film, which is desired for use in applications involving optoelectronic devices.