SiGe/Si(001) Stranski-Krastanow islands by liquid-phase epitaxy: Diffuse x-ray scattering versus growth observations

Abstract

Ex situ observed growth stages of LPE-SiGe/Si͑001͒ Stranski-Krastanow islands with a germanium content of 10% give clear evidence of a rapid shape transition at one third of the final island height. The island shape changes from a lenslike type without a top facet to truncated pyramids with ͕111͖ side facets and an ͑001͒ top facet. High-resolution x-ray diffraction has been applied to islands with higher germanium content of about 30%. Experimental results are compared with respective kinematical scattering simulations based on finite element calculations for the strain field. From these simulations the three-dimensional germanium composition profile inside the islands can be extracted and it substantiates a similar growth scenario with a distinct shape transition at one third of the final island height also for this germanium concentration range. We attribute the observed finite island size to a distinct nucleation problem at the island bottom caused by exceptional high strain energy around the island corners in combination with a strain driven wetting layer depression.

Beyond the ensemble average: X-ray microdiffraction analysis of single SiGe islands

“…3 In our analysis, we did not include lateral variations of the Ge content. 9,[30][31][32] It has been shown 21,24 that lateral composition gradients are rather negligible in LPE, where growth occurs close to thermodynamic equilibrium, and diffusion processes in the melt are dominant instead of surface diffusion, which prevails in molecular beam epitaxy. In the FEM model, we consider the nonlinear lattice parameter variation with Ge content as obtained in Ref.…”

“…Similar results have been obtained also for LPE-grown island ensembles with much higher Ge contents in previous experiments. 6,21,24 In order to explain the different intensity distribution observed in Figs. 2͑e͒ and 2͑f͒, the aspect ratio of the island needs to be lowered.…”

Liquid phase epitaxy set‐up designed for in situ X‐ray study of SiGe island growth on (001) Si substrates

“…Such samples have been characterized by a variety of methods like scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy [1], electron energy loss spectroscopy [2], micro-Raman investigation [3], grazing incidence X-ray diffraction [4], and high-resolution X-ray diffraction (HRXRD) [5].…”

“…The second advantage of Bi solvent consists in the comparable low surface free energy that promotes three-dimensional growth in favor to two-dimensional layer growth [8]. The evolution of pyramid morphology, preserved by interrupting the growth prior to the final stage, has been investigated by AFM [5]. Concerning the morphology the hereby-attained results point to a growth process starting with high indexed facets that convert finally into {111} planes.…”

A second-order finite volume scheme for three dimensional truncated pyramidal quantum dot

“…In this paper, we focus on truncated pyramidal QDs that have been studied intensively in, for example, [3][4][5][6]11,12,[14][15][16].…”