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采用低温缓冲层技术,在Si衬底上生长了质量优良的Ge薄膜。利用原子力显微镜(AFM)、双晶X射线衍射(XRD)和拉曼散射等研究了薄膜的晶体质量。结果表明,由于无法抑制三维岛状生长,低温Ge缓冲层的表面是起伏的。然而,Ge与Si间的压应变几乎完全弛豫。当缓冲层足够厚时,后续高温Ge外延层的生长能够使粗糙的表面变得平整。在90 nm低温Ge缓冲层上生长的210 nm高温Ge外延层,表面粗糙度仅为1.2 nm,位错密度小于5×105cm-2,XRD的峰形对称,峰值半高宽为460 arc sec。
Low-temperature buffer layer technology is used to grow a good quality Ge film on a Si substrate. The crystal quality of the films was investigated by atomic force microscopy (AFM), double crystal X-ray diffraction (XRD) and Raman scattering. The results show that the surface of the low-temperature Ge buffer layer is undulating due to the inability to inhibit the three-dimensional island growth. However, the compressive strain between Ge and Si is almost completely relaxed. When the buffer layer is thick enough, the growth of the subsequent high temperature Ge epitaxial layer can smooth the rough surface. The 210 nm high-temperature Ge epitaxial layer grown on 90-nm low-temperature Ge buffer layer has a surface roughness of only 1.2 nm and a dislocation density of less than 5 × 105 cm-2. The peak shape of the XRD is symmetrical with a peak full width at half maximum of 460 arcsec.