Ordering of Si_(0.55)Ge_(0.45) islands on vicinal Si(001) substrates: Interplay between kinetic step bunching and strain-driven island growth

摘要

We synchronized the kinetic and the strain-driven growth instabilities in the SiGe/Si(001) heterosystem to implement a two-stage self-organization scheme for the fabrication ' of long-range-ordered SiGe islands. In the first step, a homoepitaxial Si buffer is grown under optimized step-bunching conditions on a 4° miscut Si(001) substrate. In the second step, SiGe is deposited under conditions that yield three-dimensional island growth in registry with the underlying step-bunching template. By varying the deposition temperature of the SiGe layer, the nucleation phase of the islands could be resolved: At 4° miscut along [110] the slope of the step-bunching areas is most favorable for their disintegration into trains of adjacent (105) and (O15) facets upon pseudomorphic overgrowth with SiGe. This strain-driven step meandering instability is a precursor of the SiGe islands, which evolve during further coarsening. At high enough deposition temperatures, we find face-centered, rectangular island ordering that is entirely based on self-organization.