ALIGNMENT OF GE 3-DIMENSIONAL ISLANDS ON FACETED SI(001) SURFACES

Arrays of Ge three-dimensional (3D) islands were grown on a Si(001) su bstrate by molecular beam epitaxy without any lithographic process. Di slocation-free islands 50 nm in diameter were aligned to the [1 (1) ov er bar 0] direction of a vicinal Si(001) substrate tilted 4 degrees to ward [110]. Surface undulations consisting of (001) and(11x), x = 8-10 , facets with a 360-nm period were self-organized on the Si buffer lay er. Ge 3D islands were then preferentially grown on the upper edge of the (001) facets and were arranged in line accordingly. Nucleation of Ge islands on the surface at atomic-layer steps and deformation of nea r-surface layers in the Si substrate induced by misfit strain are stro ngly related to the self-alignment of the islands. (C) 1998 Elsevier S cience S.A. All rights reserved.