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

Abstract

Strained germanium grown on silicon with nonstandard surface orientations like (011) or (111) is a promising material for various semiconductor applications, for example complementary metal-oxide semiconductor transistors. However, because of the large mismatch between the lattice constants of silicon and germanium, the growth of such systems is challenged by nucleation and propagation of threading and misfit dislocations that degrade the electrical properties. To analyze the dislocation microstructure of Ge films on Si(011) and Si(111), a set of reciprocal space maps and profiles measured in noncoplanar geometry was collected. To process the data, the approach proposed by Kaganer, Kö hler, Schmidbauer, Opitz & Jenichen [Phys. Rev. B, (1997), 55, 1793-1810 has been generalized to an arbitrary surface orientation, arbitrary dislocation line direction and noncoplanar measurement scheme.

Bunches of misfit dislocations on the onset of relaxation of Si0.4Ge0.6/Si(001) epitaxial films revealed by high-resolution x-ray diffraction

“…However, the dislocations are still much less ordered than typically observed in other systems, where the correlation parameter c occurs much smaller than 1. 16,[38][39][40] Less correlated dislocation distribution in the present case can also be a consequence of the low growth temperature.…”

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.…”

“…While this value is marginally lower than the measured -broadening of sample F (~ 0.07), it is up to an order of magnitude larger for the rest of the series. The estimate of the TDD is therefore likely to change only by a small factor, essentially via a change in the contrast factor (more appropriately, the 2x2 contrast matrix [21]). On the other hand, we have verified that both instrument-broadening and broadening due to the finite thickness of the samples are insignificant compared to the broadening introduced by the dislocations.…”

“…While it is possible to perform rigorous Monte Carlo simulations of reciprocal space maps (or fittings of rocking curves) to determine the (relative) densities of misfit and threading dislocations (considering all the four orientations of the threading arms [21]), an estimate of the misfit dislocation density, and the resultant broadening of the -rocking curves, may be obtained from the degree of strain relaxation and the expected width of the intensity profile, in the direction perpendicular to the diffraction vector (-diffractogram) [17,22]. For both samples A and F, we estimated the misfit dislocation density to be ~ 10 6 cm -1 , and the -broadening to be ~ 0.05.…”

“…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.…”