Two-dimensional lateral ordering of self-assembled Ge islands on patterned substrates

Abstract

Stacks of Ge islands layers, separated by thin Si spacer layers, have been grown on prepatterned Si (0 0 1) substrates. The sample topography, obtained by atomic force microscopy, exhibits a regular two-dimensional island arrangement. The vertical alignment is confirmed in cross-sectional transmission electron microscopy images. X-ray diffraction reciprocal space maps around the (0 0 4) Bragg point reveal exceptional lateral and vertical ordering of the Ge islands. Photoluminescence spectra taken at 5 K show well-separated peaks of the no-phonon and the transverse-optical phonon replica of these ordered islands, which is achieved too, due to the excellent island size uniformity.