Lateral Ordering of Self-Assembled Ge Islands

Two-dimensionally ordered arrays of Ge islands are realized by molecular beam epitaxy on vicinal Si(001) surfaces with regular ripples. Deposition of a 2.5 nm Si 0.55 Ge 0.45 /10 nm Si multilayer on vicinal Si(001) surfaces gives rise to the formation of regular ripples with a typical period of 100 nm, due to step-bunching. The ripples lead to the long-range line-up of the Ge islands along their direction, while the strong repulsive interaction between the dense Ge islands determines their relative arrangement on different step bunches of a ripple. The ordering pattern can be controlled by the Ge coverage as well as the direction of the ripples. The Ge islands show a narrow size distribution with the lateral size limited by the ripple period