Fast pit filling and 3D island formation during Ge deposition on pit-patterned Si(001) substrates

Ge deposition on pit-patterned Si(001) substrates is a viable procedure for obtaining spatially ordered arrays of uniform 3D islands [1]. Despite the impressive literature, some aspects of the process remain unclear. In particular, recent experiments suggest that deposition of a few (2-3) ML of Ge on pit-patterned Si(001) triggers a massive flow of Si atoms inside the pit [2,3], causing strong pit reshaping. Here we show that a continuum model including surface diffusion, elastic relaxation, and surface Si/Ge intermixing, is able to capture such surprising behaviour. The model is a direct extension of the one presented in [4], with the important addition of a term accounting for the dependence of the diffusivity on the local Ge content. Under conditions representative of the typical experimental ones, our simulations predict fast pit filling during the first stages of growth, followed by nucleation of 3D SiGe islands inside the pit, prior to complete pit filling. [1] Z. Zhong and G. Bauer, Appl. Phys. Lett. 84, 1922 (2004). [2] M. Grydlik et al., New J. Phys. 12, 063002 (2010). [3] R. Bergamaschini, J.J. Zhang, G. Bauer, J. Tersoff, and F. Montalenti (in preparation). [4] J. Tersoff, Appl. Phys. Lett. 83, 353 (2003).