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.