Growth Mode of Coherent Si1-xGexIslands on Si

Coherent Si
1-x
Ge
x
island growth by molecular beam epitaxy is studied for a fixed growth temperature but for different Ge concentrations x in the range 0.37-0.56. A combined transmission electron microscope, x-ray diffraction, and Raman spectroscopy characterization of the samples showed that during growth the Ge migrates towards the center of the large islands to maintain epitaxial growth and that the most uniform structures are obtained at higher Ge composition when the built-in strain is also higher.