Formation of Ge Nanoripples on Vicinal Si (1110): From Stranski-Krastanow Seeds to a Perfectly Faceted Wetting Layer

Abstract

Ge growth on high-indexed Si (1110) is shown to result in the spontaneous formation of a perfectly {105} faceted one-dimensional nanoripple structure. This evolution differs from the usual Stranski-Krastanow growth mode because from initial ripple seeds a faceted Ge layer is formed that extends down to the heterointerface. Ab initio calculations reveal that ripple formation is mainly driven by lowering of surface energy rather than by elastic strain relief and the onset is governed by the edge energy of the ripple facets. Wavelike ripple replication is identified as an effective kinetic pathway for the transformation process.

Dramatically enhanced self-assembly of GeSi quantum dots with superior photoluminescence induced by the substrate misorientation

“…Such PWL can be consumed during the further growth of QDs since it is energetically unfavorable. 18 By optimizing the growth conditions, extremely dense GeSi QDs without the defects, the impurities and the wetting layer on slightly miscut Si (001) substrates can be realized. The dense QDs on miscut substrates have been observed previously.…”

Influence of composition and substrate miscut on the evolution of {105}-terminated in-plane Si1−xGex quantum wires on Si(001)

“…1(b) shows that these edges result from the intersection of two adjacent {105} facets, whose RS-reconstruction 29 is not commensurable, presumably resulting in a high density of defects along the 551 intersection line. 31,33 In contrast, the RS reconstructions of opposite {105} facets are mirror symmetric with respect to the 100 intersection line that defines the ridge of in-plane wires on Si(001). This geometrical argument is corroborated by reported 100 edge energies 41 that are by almost a factor of 40 smaller than the ones used in Refs.…”

“…1(b), the 551 and 100 intersection lines differ substantially in their atomic configuration. 31 The hut clusters on Si(001) are therefore also different from the {105}-terminated SiGe wire bundles into which a Ge wetting layer on (1 1 10) oriented Si substrates disintegrates, 32,33 because their ridges are 551 oriented. Accordingly, the base angles of the triangular cross sections amount to 11.3…”

“…34 They took into account the volumetric strain energy, ab initio surface energies of the strained {105} facets, and estimated edge energies taken from their earlier work on 551 oriented wire bundles on Si(1 1 10). 33 They calculated the energy differences E between wires with different base widths b and a two-dimensional film of the same volume and found a shallow E minimum for wires with b min = 16 nm. Here, we study the influence of the composition x of the initially deposited Si 1−x Ge x layer on wire growth during annealing.…”

Continuum modelling of semiconductor heteroepitaxy: an applied perspective

“…The most striking example is given by Ge{105} whose surface energy is stabilized by compression [43][44][45] to the point that the (001) wetting layer can spontaneously break into {105} faceting [7,46]. Micron-long, horizontal Ge wires delimited by {105} facets, have been recently observed [24,47] and shown to display peculiar electronic properties.…”