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

Abstract

""We report on the experimental and theoretical investigation of the relaxation in Ge-rich SiGe\\\/Ge\\\/Si heterostructures. The experimental x-ray diffraction data are interpreted with the help of a model including both edge and 60 degrees misfit dislocations in the calculated x-ray scattering intensity. Our results show that highly positionally correlated edge dislocations dominate in the relaxation of the compressive strain at the Ge\\\/Si interface, while a smaller tensile strain at the SiGe\\\/Ge interfaces released by uncorrelated\\\/little correlated 60 degrees dislocations."

Dislocation density and strain-relaxation in Ge 1−x Sn x layers grown on Ge/Si (0 0 1) by low-temperature molecular beam epitaxy

“…In order to determine the dislocation density, analysis of the rocking curves shown in Figures 4 (a) -4(d) has been performed following the approach due to Kaganer et al [16,17]. This approach has been shown in previous works to yield very reliable estimates of dislocation density for GaN [18][19][20] and SiGe [21][22][23] epitaxial layers. Unlike in the more-widely-used Dunn and Koch method [35] (or the Williamson-Hall method [36]), which relies solely upon the FWHM value of a Gaussian distribution of the diffracted intensity, to determine the TDD by the Kaganer approach, the -rocking curves are fitted by [16] ( ) = ∫ (− 2 + ) cos( ) + ∞ 0 … … … (5) where and are the integrated peak intensity and the background intensity, respectively.…”

“…Here, we study the molecular-beamepitaxy (MBE)-growth of Ge1-xSnx layers on Ge/Si(001) substrates and investigate the threading dislocation densities (TDD) in these layers, by the approach developed by Kaganer et al [16,17]. We demonstrate that this high-resolution-X-ray-diffraction (HRXRD)-based technique, which has been successfully used to estimate dislocation densities in GaN [18][19][20] and SiGe [21][22][23] in previous works, also provides very reliable estimate of the same, for large area Ge1-xSnx epilayers. We observe that the relaxation of the Ge1-xSnx epilayers is predominantly driven by dislocations threading from the underlying Ge buffer layers.…”

Onset of plastic relaxation in the growth of Ge on Si(001) at low temperatures: Atomic-scale microscopy and dislocation modeling

“…In particular, introducing the Ge Young modulus under biaxial stress Y and defining the x axis oriented along the [1][2][3][4][5][6][7][8][9][10] the solid line is drawn as a reference for the printed version and for the graphs in Fig. 3), the σ RSS maximum position (star), the relative glide plane (blue online; the dashed line is drawn as a reference for the printed version and for the graphs in Fig.…”

“…Several mechanisms have been proposed to explain the presence and the abundance of edge dislocations in high-misfit SiGe systems. [12][13][14][15] One of the most credited hypotheses concerns an induced nucleation mechanism promoting the nucleation and junction of two 60 • dislocations, usually called complementary dislocations, characterized by having Burgers vectors giving rise to Lomer dislocation if joined (e.g., b 1 = a/2 [1][2][3][4][5][6][7][8][9][10]). 10 In particular, it has been suggested that the stress field of a first dislocation already existing at the interface induces the nucleation of a complementary 60 • dislocation that has as a glide plane the mirrorlike symmetric glide plane of the first, intersecting it exactly at the interface (ML plane in the following).…”

“…10 Burgers vector analyses (g·b technique) evidenced the presence of edge dislocations at the interface, with their density increasing with a further rise in Ge content and becoming dominant in pure Ge depositions. 10,11 Edge misfit dislocations (often called Lomer dislocations) are characterized by Burgers vectors b = ±a/2 [1][2][3][4][5][6][7][8][9][10] or b = ±a/2[110] lying in the interface plane. Therefore, they release twice the misfit strain with respect to 60 • dislocation segments.…”