Intermixing-promoted scaling of Ge/Si(100) island sizes

Abstract

The shape evolution and the effect of deposition temperature on size and composition of chemical vapor deposition grown Ge/Si(100) islands have been investigated in the deposition temperature range 450–850 °C. It is found that the increase of the growth temperature above 600 °C entails a strong island enlargement due to an increased Si/Ge intermixing. The crystallographic structure of the islands was investigated by transmission electron microscopy. The analysis of the resulting Moiré pattern reveals that the island lattice deformation decreases with increasing island size and that the effective mismatch ε between the silicon substrate and the epilayer decreases with increasing deposition temperature. The island nucleation size, the mean size of coherent islands and the critical size for the insertion of misfit dislocations have been found to scale as ε−2, ε−2, and ε−1, respectively. The agreement of our experimental scaling results with the predictions of theoretical calculation performed for homogeneous heterostructures suggests that, although the Si distribution inside the islands is not homogeneous, the island growth is driven by the mean effective strain.