Si-capping-induced surface roughening, accompanying Si–Ge alloying, is reported for strip structures of Ge selectively grown on Si via ultrahigh vacuum chemical vapor deposition. A 0.7-μm-wide strip structure of Ge running in the [110] direction, as well as a 100-μm-wide mesa structure, is selectively grown on an Si (001) surface exposed in an SiO₂-masked Si substrate. In contrast to a wide mesa structure with a Ge thickness of 0.5 μm, composed of a (001) plane at the top and {113} facet planes at the sidewalls, the (001) top plane almost disappears for the narrow strip structure. The strip is mainly surrounded with inclined {113} planes near the top and adjacent {111} planes at the side, while the structure near the bottom edges depends on the growth temperature (600/700 °C). An Si cap layer with a thickness of 10 nm or larger is subsequently grown at 600 °C to protect the fragile Ge surface. The scanning electron microscopy observations reveal a roughened surface on the {113} planes, with depressions specifically induced near the boundary with the {111} planes. The Raman spectra indicate that an SiGe alloy is formed on the strip and the wide mesa sidewalls due to the Si–Ge interdiffusion. There is no such SiGe alloy on the (001) plane of the wide mesa top. The Si cap layer with a misfit strain probably works as a stressor for the underlying Ge, applying stress concentrated around the facet boundaries and inducing a mass transport alongside the Si–Ge interdiffusion for strain relaxation. In terms of the fabrication of practical devices, it is important to suppress the roughening and alloying significantly by decreasing the growth temperature for the Si cap layer from 600 to 530 °C.

中文翻译：

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在 Si 衬底上选择性生长的 Ge 条带结构上的 Si 封盖诱导表面粗糙化

据报道，通过超高真空化学气相沉积在 Si 上选择性生长的 Ge 条状结构，伴随 Si-Ge 合金化，Si-capping 诱导的表面粗糙化。甲0.7- μ Ge的[110]方向上延伸，以及一个100-米宽的条形结构μ米宽的台面结构，在暴露的Si（001）表面上选择性地生长的SiO ₂ -masked硅基质。与 Ge 厚度为 0.5 μ的宽台面结构相比 m，由顶部的 (001) 平面和侧壁的 {113} 小平面组成，对于窄带结构，(001) 顶平面几乎消失。带材主要被顶部附近的倾斜{113}面和侧面相邻的{111}面包围，而底部边缘附近的结构取决于生长温度（600/700°C）。随后在 600 °C 下生长厚度为 10 nm 或更大的 Si 帽层，以保护脆弱的 Ge 表面。扫描电子显微镜观察显示 {113} 平面上的表面粗糙，在与 {111} 平面的边界附近特别诱发凹陷。拉曼光谱表明，由于 Si-Ge 相互扩散，在带材和宽的台面侧壁上形成了 SiGe 合金。宽台面顶部的（001）平面上没有这种SiGe合金。具有失配应变的 Si 帽层可能作为底层 Ge 的应力源，施加集中在小平面边界周围的应力，并在 Si-Ge 相互扩散的同时诱导质量传输以实现应变松弛。在实际器件的制造方面，重要的是通过将 Si 帽层的生长温度从 600°C 降低到 530°C 来显着抑制粗糙化和合金化。