We report on a combination of lithography and self-assembly techniques which results in long-range two-dimensionally ordered Ge islands. Island lattices with perpendicular but also with obliquely oriented unit vectors were realized. Quantitative analysis of the island topographies demonstrates that the size dispersion of these islands is smaller than that found on flat substrates. Furthermore, island formation on the patterned substrates is observed for a smaller amount of Ge deposition. However, with further Ge deposition an increasing amount is incorporated into the sidewalls.

Two-dimensional (2D) periodic arrays of Ge islands were realized on prepatterned Si (001) substrates by solid-source molecular-beam epitaxy. Atomic-force microscopy images demonstrate that the Ge islands are formed in the 2D laterally ordered pits of patterned substrates. The 2D periodicity of the substrate pattern is replicated throughout a stack of Ge island layers by strain-driven vertical ordering. Photoluminescence spectra of the ordered Ge islands show well-resolved peaks of the no-phonon signal and the transverse-optical phonon replica. These peaks are observed at nearly the same energy as those of random Ge islands deposited under the same conditions on unpatterned Si substrates.

Self-assembled Ge islands were grown on stripe-patterned Si(001) substrates by solid source molecular beam epitaxy. The surface morphology obtained by atomic force microscopy and cross-sectional transmission electron microscopy images shows that the Ge islands are preferentially grown at the sidewalls of pure Si stripes along the [−110] direction at 650 °C or along the trenches, whereas most of the Ge islands are formed on the top terrace when the patterned stripes are covered by a strained GeSi buffer layer. Reducing the growth temperature to 600 °C results in a nucleation of Ge islands both on the top terrace and at the sidewall of pure Si stripes. A qualitative analysis, based on the growth kinetics, demonstrates that the step structure of the stripes, the external strain field, and the local critical wetting layer thickness for the islands formation contribute to the preferential positioning of Ge islands on the stripes.

Self-assembled Ge islands were grown by solid-source molecular-beam epitaxy on the submicron stripe-patterned Si(001) substrates at $\text{650\hspace{0.05em}°}\mathrm{C}.$ Atomic-force microscopy shows that the Ge islands grow preferentially at the sidewall of the Si stripes, oriented along the $\text{[−110]}$ direction. The migration of the Ge adatoms from the top terrace down to the sidewall accounts for the island formation at the sidewall of the stripes. However, most of the Ge islands are formed on the top terraces when the patterned stripes are covered by a strained GeSi multilayer buffer prior to Ge island growth. Apparently, the strained buffer layer acts as a stressor and contributes to the preferential growth of islands on the top terrace.

A silicon light emitter in telecom-band based on a single germanium quantum dot precisely embedded in a silicon photonic crystal nanocavity is fabricated by a scalable method. A sharp resonant luminescence peak is observed at 1498.8 nm, which is enhanced by more than three orders of magnitude. The Purcell factor for the fundamental resonant mode is estimated from enhancement factor and increased collection efficiency. The cavity modes coupled to the ground state and excited state emission of germanium quantum dot are identified in the luminescence spectrum. Our devices provide a CMOS-compatible way of developing silicon-based low-power consuming light emitters, and are promising for realizing on-chip single photon sources.