A combination of high-resolution X-ray diffractometry and diffraction imaging techniques applied to the study of MOVPE-grown Cd xHg 1−xTe/CdTe on GaAs

Abstract

We have applied a range of high-resolution X-ray diffractometry and diffraction imaging techniques to study the structural properties of Cd x Hg 1- x Te (CMT) grown epitaxially on GaAs by MOVPE. In this paper we specifically describe three such techniques and evaluate and compare the results from each. Automated double crystal diffractometry with a mapping facility provides information on the quality and uniformity of the layers. 004 rocking curve widths vary from < 70 arc seconds on the best samples to substantially higher values on poorer material. Study of non-uniform layers shows that lattice tilts are a dominant influence on rocking curve widths and large (up to 2°) misorientations between epilayer and substrate (100) planes are found on some samples. These characteristics are further investigated using triple crystal diffractometry. X-ray topography of the layers shows orientation-contrast features which correlate directly with the GaAs substrate dislocation distribution. A number of layers with varying degrees of structural quality have been examined using a combination of the above techniques. Recent results are reported illustrating the value of each technique and we demonstrate how the application of a combination of X-ray diffraction techniques can be a powerful tool for investigating the nature of structural defects in this highly mismatched heteroepitaxial system.