Initial stage of the 2D-3D transition of a strained SiGe layer on a pit-patterned Si(001) template

TL;DR

This study explores how strained Ge layers transition from 2D to 3D on pit-patterned Si(001) templates, revealing the role of strain-driven instabilities and surface morphology in island nucleation.

Contribution

It demonstrates the influence of geometrical restrictions and facet formation on the initial 2D-3D transition of Ge layers on patterned silicon surfaces.

Findings

Strain-driven step-meandering and step-bunching instabilities coexist in pits.

Morphological transformation into low-energy facets affects Ge island nucleation.

Facetted side-walls influence the nucleation site at the pit bottom.

Abstract

We investigate the initial stage of the 2D-3D transition of strained Ge layers deposited on pit-patterned Si(001) templates. Within the pits, which assume the shape of inverted, truncated pyramids after optimized growth of a Si buffer layer, the Ge wetting layer develops a complex morphology consisting exclusively of {105} and (001) facets. These results are attributed to a strain-driven step-meandering instability on the facetted side-walls of the pits, and a step-bunching instability at the sharp concave intersections of these facets. Although both instabilities are strain-driven, their coexistence becomes mainly possible by the geometrical restrictions in the pits. It is shown that the morphological transformation of the pit surface into low-energy facets has strong influence on the preferential nucleation of Ge islands at the flat bottom of the pits.