Study of Si/Ge Strain-Controlled Atomic-Laver Super-Lattices

异质原子层外延（ALE）方法已经被开发用于在Ge衬底上的Si和在Si衬底上的Ge。并通过各种表面敏感性评价方法阐明了ALE的生长特性。在此基础上，制备了应变控制的Si/Ge原子层超晶格。主要研究结果如下：1.通过DCS（SiH_2Cl_2）和原子氢（AH）的交替曝光，建立了一种在（100）和（111）表面上都具有理想的1 ML/周期生长速率的Si同质ALE工艺。利用表面形貌变化研究了微观生长动力学，在最佳ALE条件下获得了非常平整的生长表面，表面粗糙度增加小于0.1A.通过交替暴露DMG（GeH 2（CH 3）2）和AH，Ge-ALE工艺在430 ℃ ~ 520 ℃的宽温度范围内以1 ML/cycle的速率生长薄膜，但由于薄膜中存在大量的C残留，当温度高于445 ℃时，生长的表面平整度变差. GeH 2Cl 2似乎是较宽温度窗口的所需源材料.用SiH_4在Ge表面进行了1 ML厚的Si吸附。通过对这种1 ML厚的Ge on Si结构进行Si ALE，制备了原子突变的Si/Ge异质界面。这种原子突变的异质结构在550 ℃以下是热稳定的。4.通过在Si表面上交替暴露GTC（GeCl 4），形成1 ML厚的Ge层。该结构是一种理想的1 MLGe/Si异质结结构，无团簇和混合。用Ge的连续自对准外延（ALE）方法制备了Ge/Si原子突变异质界面。利用这些异质ALE方法制备了具有内应变的Si_7/Ge_3原子层超晶格，并利用透射电子显微镜观察了其微观精细结构。

Hetero atomic-layer epitaxy (ALE) methods have been developed for both Si on the Ge substrate and Ge on the Si substrate. And the ALE-growth characteristics were clarified by using various surface-sensitive evaluation methods. Base on these results, strain-controlled Si/Ge atomic layer super-lattices have been fabricated. The major results are listed below.1. By alternative exposure of DCS (SiH2Cl2) and atomic hydrogen, AH, a Si homo-ALE procedure has been established with an ideal 1ML/cycle growth rate on both (100) and (111) surfaces. An ALE-window was from 530oC to 610oC.Microscopic growth kinetics has been investigated by using surface morphology change, and the extremely flat grown surface with increased surface roughness of less than 0.1A was obtained under the optimum ALE conditions.2. By alternating exposure of DMG (GeH2(CH3)2) and AH, Ge-ALE procedure has been established with the 1ML/cycle growth rate over a wide temperature window from 430oC to 520oC.But due to large amount of residual C in the grown film, the grown surface flatness was deteriorated for temperatures more than 445oC.GeH2Cl2 seems the desired source material to the wider temperature window for the flat surface.3. 1ML-thick adsorption of Si has been done on the Ge surface by using SiH4. The atomically abrupt Si/Ge hetero interface has been fabricated by carrying out the Si ALE on this 1ML-thick Ge on Si structure. This atomically abrupt hetero structure was thermally stable up to 550oC..4. By alternating exposure of GTC (GeCl4) on the Si surface, 1ML-thick Ge layer was formed. This structure was concluded to be an ideal 1MLGe/Si hetero structure without clustering and intermixing. Atomically abrupt Ge/Si hetero interface has been fabricated by successive home ALE of Ge.5. By using these hetero ALE methods, Si7/Ge3 atomic-layer super-lattices with internal stain has been fabricated and their microscopically fine structures were observed by a transmission electron microscope.