Diffuse x-ray scattering from misfit dislocations in SiGe epitaxial layers with graded Ge content

Abstract

A theory has been developed describing x-ray diffuse scattering from misfit dislocations in epitaxial layers. This approach has been used for explaining the origins of diffuse x-ray scattering from SiGe layers with linearly graded Ge content. The distribution of the diffusely scattered intensity in reciprocal plane measured by triple-axis x-ray diffractometry has been compared with theoretical predictions and a good agreement has been achieved. It is demonstrated that the main part of the diffusely scattered intensity originates from random strains caused by misfit dislocations at the substrate–epilayer interface or in the relaxed part of the compositionally graded layers. The contribution of the threading dislocation segments to the diffuse scattering is rather small.

X-ray diffraction study of plastic relaxation in Ge-rich SiGe virtual substrates

“…Equation (13) shows that the peak position of a j th layer is affected only by the dislocations laying at and under the j th interface, since for z > d the integrals…”

“…10,12 The x-ray scattering theory has been also extended to epitaxial films consisting of layers with different composition and relaxation degree, and to graded layers. [13][14][15][16][17] These works use additional approximations that simplify the scattering intensity calculation. Particularly, they assume that dislocations of only one type (the 60 • dislocations) are present in the film and that the positional correlations are absent.…”

Growth of high quality Ge∕Si1−xGex on nano-scale patterned Si structures

“…Such tilts have been reported to originate from substrate miscut, 52 which applies a different stress on each slip system and also promotes glide process. [53][54][55] The FWHM of the peak determines the quality of the layer in the bulk. The x-ray RSM shows that the FWHM is significantly reduced in the nanopatterned structures, suggesting a reduction in defect density.…”

High Resolution X-ray Reciprocal Space Mapping

“…In our case, the dominant defects are misfit dislocations. We have shown recently that misfit dislocations cause randomly distributed strain fields in the epilayer [22]. These random strains lead to the diffuse scattered intensity around the coherent diffraction peaks.…”

“…Therefore, by calculating the scattering from the random strains distributed in the SiGe epilayers using a kinematic theory based on considerations previously suggested by Krivoglaz [23], we reproduce theoretically the intensity distribution in the reciprocal space maps. This analysis provides furthermore information cm the in-depth distribution of dislocations [18,22].…”