Evolution of strain relaxation in compositionally graded Si1−xGex films on Si(001)

Abstract

High-resolution x-ray reciprocal space mapping was employed to determine the in-depth strain distribution of Si1−xGex films with linear composition gradings between 4.2% and 15% Ge per μm, and thicknesses between 0.4 and 1.7 μm. The variation of grading and thickness parameters of the samples provides a complete picture of the overall relaxation behavior of linearly graded epilayers. The x-ray data show a top layer of grading-dependent residual strain whereas the lower parts of the films are completely and/or partly relaxed with respect to the Si substrate.

Strain relaxation of Ge1−xSix buffer systems grown on Ge (001)

“…From this model, it turns out that the topmost part of the linearly graded epilayer remains free of misfit dislocations, and thus fully strained, whereas the underlying part relaxes completely by means of spreading homogeneously misfit dislocations in this region. In our previous work on the graded Si 1Ϫy Ge y buffer layers on Si ͑001͒ substrates, 19 was shown that except for the difference on the numerical values caused by kinetic limitations, this model explains quite well the observed phenomenon. However, the Tersoff model does not explain the partial relaxation in the top part of the Ge 1Ϫx Si x graded buffer observed in this study.…”

Thin relaxed SiGe virtual substrates grown by low-energy plasma-enhanced chemical vapor deposition

“…The method used for this determination of the strain state and the composition of the layers is described in Ref. [26]. The lattice parameters were obtained from the positions corresponding to maximum intensity of the scattered radiation of the buffers in the RSMs.…”

Strain relaxation in compositionally graded epitaxial layers

“…A variety of graded layers have been studied for this purpose, such as Si x Ge 1Ϫx on Si, [1][2][3][4] AlGaSb graded superlattices on GaSb, 5 InAS x Sb 1Ϫx on InSb, 6 In x Ga 1Ϫx P on GaP, 7 and In x Ga 1Ϫx As on GaAs. This effort has been most frustrating in the system with large lattice mismatch between epitaxial layers and substrates, particularly those that are readily available such as GaAs and Si.…”