Structure of GaAs:Be crystals studied by X-ray quasi-forbidden reflections

Abstract

The X-ray quasi-forbidden reflection method (XQFR) employs for example (002) and (006) reflections in the GaAs structure. They are called quasi-forbidden because of very small differences in scattering factors between gallium and arsenic. These reflections are very sensitive to the chemical composition and hardly sensitive to large crystal lattice defects. The method is based on the comparison of quasi-forbidden reflection intensities for the investigated crystal with the intensities obtained for a reference, quasi-ideal crystal. One can build theoretical models of lattice point defects distributions and local distortions and calculate appropriate structure factors. The kinematical theory of X-ray diffraction then allows comparison with the experimental data obtained with the XQFR method. In our preliminary study we employed only the 006 reflection to verify positions of the beryllium atoms and how they are incorporated into gallium arsenide lattice and to study the local microscopic structures around them.