Formation of GeSn layers on Si (001) substrates at high growth temperature and high deposition rate by sputter epitaxy method
Formation of GeSn layers on Si (001) substrates at high growth temperature and high deposition rate by sputter epitaxy method
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DOI：
10.1007/s10853-015-8990-4
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发表时间：
2015-04
影响因子：
4.5
通讯作者：
T. Tsukamoto;N. Hirose;A. Kasamatsu;T. Mimura;T. Matsui;Y. Suda
中科院分区：
文献类型：
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作者：
T. Tsukamoto;N. Hirose;A. Kasamatsu;T. Mimura;T. Matsui;Y. Suda
采用溅射外延法在Si衬底上生长GeSn层。获得了Sn含量为11.5%的平整GeSn层。在523 K下生长的Sn含量为11.5%的GeSn层的X射线衍射谱中，Ge（004）峰在64.5306°附近出现，半高宽为0.0984°。然而，在本研究中，在548 K及以上的生长温度下，在锡含量为11.5%的GeSn层中观察到锡的表面偏聚，这增加了表面粗糙度。在Si衬底上形成的GeSn层的结晶度强烈地依赖于生长温度，但降低结晶度的主要因素是Si和GeSn之间的大的晶格失配。根据透射电子显微镜图像，一些位错出现在界面处生长在523 K和Si由于大的晶格失配，但没有Sn表面偏析和高度有序的原子排列观察到在上部区域。据认为，高沉积速率限制了Sn表面偏析，并使GeSn层能够在相对较高的温度下生长，从而提高了结晶度。具有8.4%Sn含量的GeSn层的带隙通过傅里叶变换红外光谱测量确定并且为约0.52eV，这表明发生带隙变窄。
GeSn layers are formed on Si substrates by the sputter epitaxy method. Flat GeSn layers with 11.5 % Sn content are obtained. In the X-ray diffraction spectra of the GeSn layers with 11.5 % Sn content grown at 523 K, a sharp Ge (004) peak appears at about 64.5306° and the full width at half maximum is about 0.0984°. However, the surface segregation of Sn is observed in the GeSn layers with 11.5 % Sn content at growth temperatures of 548 K and above in this study, which increases the surface roughness. The crystallinity of the GeSn layers formed on Si substrates strongly depends on the growth temperature, but the primary factor degrading the crystallinity is the large lattice mismatch between Si and GeSn. According to a transmission electron microscope image, some dislocations appear at the interface of the GeSn layer grown at 523 K and Si owing to the large lattice mismatch, but there is no Sn surface segregation and a highly ordered atomic arrangement is observed in the upper region. It is considered that a high deposition rate limits Sn surface segregation and enables the growth of GeSn layers at relatively high temperatures, resulting in improved crystallinity. The band gap of the GeSn layers with 8.4 % Sn content is determined by Fourier transform infrared spectroscopy measurement and is about 0.52 eV, which indicates that band gap narrowing occurs.