Analysis of reciprocal space maps of GaN(0001) films grown by molecular beam epitaxy

Abstract

The reciprocal space map of a heteroepitaxial single‐crystal GaN(0001) film on 6H‐SiC(0001) is analyzed. The film contains a high density of threading dislocations which intersect the film parallel to the surface normal. The strain field associated with these dislocations is expected to broaden all reciprocal lattice points to discs perpendicular to the dislocation lines, i.e. parallel to the surface. Experimentally, however, the reflection is observed to be broadened also perpendicular to the surface and is rotated towards the surface normal. Using Monte Carlo simulations, it is shown that both of these features are a natural consequence of the presence of misfit dislocations at the film/substrate interface.

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.…”

Diffuse X-ray scattering from local chemical inhomogeneities in InGaN layers

“…In the cases of misfit dislocations or mosaic structure, the prevailing type of lattice deformation is local random rotation, which keeps constant the atomic plane distance (and consequently the Bragg angle); this gives rise to the elongation of the diffuse maximum along a small arc of the Debye ring, i.e. in the direction perpendicular to the diffraction vector (see Pietsch et al, 2004;Kaganer et al, 2005;Barchuk et al, 2010;Kopp, Kaganer, Jenichen & Brandt, 2014;Kopp, Kaganer, Baidakova et al, 2014;Barchuk et al, 2018). On the other hand, local In inhomogeneities change the lattice parameter and consequently the Bragg angle, which causes the elongation of the diffuse maximum mainly along the diffraction vector (see Figs.…”

Characterization of dislocations in germanium layers grown on (011)- and (111)-oriented silicon by coplanar and noncoplanar X-ray diffraction

“…Because of this fact we will neglect fine effects due to modification of the displacement fields related to the presence of the boundary and will use the solution for an infinite medium. In papers by Kopp and co-workers (Kopp, Kaganer, Baidakova et al, 2014;Kopp, Kaganer, Jenichen & Brandt, 2014) the effect of boundary terms on the X-ray diffraction profile was accounted for using the direct assumption-free Monte Carlo approach and it was shown to be subtle. For the mentioned reasons we will use the displacement fields for an infinite medium,…”