Self-assembling and self-ordering of Ge islands on vicinal Si(001) surfaces

Fabrication of semiconductor quantum dot structures with a regular in-plane spatial distribution and optimum size uniformity is highly desirable for applications of their novel optical and electronic properties. This remains a challenging subject, especially on the nanometer scale. The strain-driven self-assembled formation of Ge islands on Si during molecular beam epitaxy (MBE) in the Stranski-Krastanov mode appears as the most promising method. An ensemble of Ge islands with random spatial distribution develops on flat Si(001) substrates. We have studied the growth of self-assembled Ge islands on vicinal Si(001) surfaces by MBE. Ge islands on vicinal Si(001) surfaces with a <110> miscut direction are compact pyramids with four equivalent {105} facets. Nearly perfect twodimensional ordering is achieved in a single layer of self-assembled Ge islands on vicinal Si(001) surfaces with a regular ripple caused by step-bunching. Islands with regular wellcontrolled size, shape and lateral separation are achieved by this self-assembling and selfordering process without any nanostructuring required.