Self-Ordering of Ge Islands on Si Substrates Mediated by Local Strain Fields

We have fabricated linear chains and two-dimensional arrays of Ge islands by self-assembling and self-ordering processes on vicinal Si substrates. Step bunches and stripe-like strain fields caused by underlying Si/SiGe multilayers with periodic wire-like accumulations at step edges induce an alignment of Ge islands. Repulsion of neighboring islands is caused by overlapping short-ranged strain fields surrounding partially strain relaxed dots and defines a minimum island separation. A periodic array of wires forming within the multilayer serves as a self-organized template for two-dimensionally ordered Ge islands with a lateral period of 120 nm which is comparable to the island size.