Strain-driven alloying in Ge/Si(100) coherent islands

Ge/Si(100) island size distributions were monitored for coverages between 3.5 and 14.0 monolayers at growth temperatures from 450 to 600 degrees C. Features in these distributions are correlated with characteristic island morphologies. The mean dome cluster size increased and the onset of island dislocation was delayed as the growth temperature increased. At 600 degrees C, very large hut clusters are formed. This behavior is attributed to strain-assisted alloying of the Ge clusters. Energy dispersive x-ray analysis confirms Si diffusion into the Ge clusters at 600 degrees C. An atomistic elastic model supports the interpretation that alloying is driven by strain energy enhancement near the island perimeters.