High-quality Ge epitaxial film based on dislocation trapping mechanism in patterned Si substrate

Threading dislocation density (TDD) in a Ge heteroepitaxial film on Si is reduced based on a dislocation trapping mechanism in a patterned substrate. An array of V-shaped grooves on the submicron scale is patterned in the [110] direction on a (001) Si substrate. Epitaxial growth of Ge with a thickness of 1 μ m by CVD realizes a reasonable flat surface despite the non-flat starting surface. The TDD in Ge for a V-shaped groove pattern of 0.5 μ m in width with an inter-groove distance of 0.3 μ m is obtained as low as 4 × 10 7 cm –2 , which is lower than about 6 × 10 7 cm –2 for the rectangular one with the same groove width and inter-groove distance and about 22 × 10 7 cm –2 for the unpatterned one. The reduction is attributed to the dislocation trapping at the groove regions, as observed by cross-sectional transmission electron microscopy.