Diffraction Space Mapping Research Articles

The simulation and interpretation of diffraction profiles from partially relaxed layer structures

A procedure for modelling the Bragg-case dynamical diffraction profiles from crystals with defects has been developed. This simulation of profiles has been applied to partially relaxed semiconductor layer structures whose lattice parameter and layer thickness were sufficient to induce interfacial defects. The procedure has a minimum of input parameters and is therefore applicable to routine use and has been shown to give good agreement with experimental data and also can predict the extent of the strain fields generated at the interfaces. The evaluation of the relaxation parameters in these strained layer structures is presented for some examples making use of high-resolution diffraction-space mapping and topography.

Multicrystal X-ray diffraction of heteroepitaxial structures

An appraisal of high-resolution multi-crystal multi-reflection diffractometry (HRMCMRD) and topography is presented to illustrate its potential for structure analysis. Examples of methods for extracting lateral interface roughness, studying layered structures with imperfect epitaxy (including strained layer structures) are given to show the wealth of information available from X-ray techniques. The advantages of diffraction space mapping are discussed in addition to the use of topography to interpret the diffuse and Bragg scattering. The HRMCMRD has a dynamic range of 10 6 and can record topographs with intensities less than 1 count/s.

Combining high-resolution X-ray diffractometry and topography

Multiple-crystal diffraction profiles and multiple-crystal topography have been combined to characterize semiconductor materials. X-ray topographs have been measured on the same region of the sample as the diffraction profiles and diffraction space maps, by insetting a film cassette in the diffracted beam path of a high-resolution diffractometer. This has proved to be a very powerful combination for providing a deeper understanding of the structural features that give rise to the high-resolution diffraction profiles. The data collection mode is discussed and the problems associated with interpreting `rocking curves' of imperfect materials. The misorientation and nature of the mosaic blocks in semi-insulating GaAs have been revealed by this method.