Ge/Si heterostructure with fully strain-relaxed Ge film was grown on a Si (001) substrate by using a two-step process by ultra-high vacuum chemical vapor deposition. The dislocations in the Ge/Si heterostructure were experimentally investigated by high-resolution transmission electron microscopy (HRTEM). The dislocations at the Ge/Si interface were identified to be 90° full-edge dislocations, which are the most efficient way for obtaining a fully relaxed Ge film. The only defect found in the Ge epitaxial film was a 60° dislocation. The nanoscale strain field of the dislocations was mapped by geometric phase analysis technique from the HRTEM image. The strain field around the edge component of the 60° dislocation core was compared with those of the Peierls–Nabarro and Foreman dislocation models. Comparison results show that the Foreman model with a = 1.5 can describe appropriately the strain field around the edge component of a 60° dislocation core in a relaxed Ge film on a Si substrate.
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机译:通过两步工艺,通过超高真空化学气相沉积,在Si(001)衬底上生长具有完全应变松弛的Ge膜的Ge / Si异质结构。 Ge / Si异质结构中的位错通过高分辨率透射电子显微镜(HRTEM)进行了实验研究。 Ge / Si界面的位错被确定为90°全边缘位错,这是获得完全松弛的Ge膜的最有效方法。在Ge外延膜中发现的唯一缺陷是60°位错。通过几何相位分析技术从HRTEM图像中绘制了位错的纳米级应变场。将60°位错核心边缘分量周围的应变场与Peierls–Nabarro和Foreman位错模型的应变场进行了比较。比较结果表明,a = model1.5的Foreman模型可以恰当地描述Si衬底上松弛Ge膜中60°位错核的边缘分量周围的应变场。
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