Synchrotron White Beam X-Ray Topography Analysis of MBE Grown CdTe/CdTe (111)B

The structural quality of CdTe(111)B substrates and MBE grown CdTe epilayers is examined with synchrotron white beam x-ray topography (SWBXT). Reflection SWBXT indicates that CdTe substrates with comparable x-ray double crystal rocking curve full width at half maximum values can have radically different defect microstructures, i.e. dislocation densities and the presence of inclusions. Dislocation mosaic structures delineated by SWBXT are consistent with the distribution of etch pits revealed by destructive chemical etch pit analysis. Direct one-to-one correspondence between distinct features of the topographic image and individual etch pits is demonstrated. Clearly resolved images of individual dislocations are obtained by carrying out transmission SWBXT. Our investigation demonstrates how, the extent of twinning in a CdTe epilayer is strongly influenced by the quality of the defect microstructure, and how dislocations propagate from an inclusion.