Numerical simulation of Bragg-case topographic images of dislocations and precipitates in GaAs epitaxial layers

Abstract

The numerical integration of Takagi-Taupin equations was used for the simulation of double-crystal topographic images of threading dislocations, misfit dislocation crossings and point-like precipitates in silicon and gallium arsenide. The simulations took account of lattice parameter profiles and the finite divergence of the beam. It was found that the images of dislocations, especially those outcropping on the surface, are dominated by a dilation-orientation contrast. Stronger interference effects were present in the images of point-like defects. A similarity was observed between the images of threading dislocations computed for equivalent positions in the layer and substrate maxima. A reasonable correspondence between simulated and experimental images was confirmed in several cases.

The images of misfit dislocations in Bragg-case synchrotron section topography

“…Similarly as in our former papers [2,3] we assumed misfit dislocations of perfect 60 ~ mixed type. The deformation field was calculated in isotropic approximation and the corresponding formulae were obtained by differentiation of those given by Cherns and Stowell [8] and completed by the terms describing the screw component of dislocation.…”

“…The former papers by Riglet et al [1], Wierzchowski [2,3] and Spirkl et al [4] dealt with the misfit dislocation contrast in multi-crystal topography. The former papers by Riglet et al [1], Wierzchowski [2,3] and Spirkl et al [4] dealt with the misfit dislocation contrast in multi-crystal topography.…”

Bragg-case K⃗g and K⃗0 beam double-crystal synchrotron studies of growth sectors and dislocations in synthetic diamonds

“…8͑a͒ is a mixed-type 30°dislocation inclined at 65.7°to the crystal surface. 18,20,29 Here we observe several loops or sectors of fringes, strongly dependent on their positions on the reflexion curve. 10.…”

Observation of individual dislocations in 6H and 4H SiC by means of back‐reflection methods of X‐ray diffraction topography

“…The present simulations were realised with slightly modified programs used previously for performing the simulations described by Wierzchowski et al [11][12][13] The algorithms both with constant and variable step of integration were used. The integration grids corresponding to the present cases are shown in figure 1.…”