COMPOSITIONAL, STRAIN CONTOUR AND PROPERTY MAPPING OF CDZNTE BOULES AND WAFERS

We have developed detailed non-destructive mapping and spatial imaging techniques for comparing boule and wafer properties with analytical p redictions from high-fidelity process models for seeded vertical Bridg man-Stockbarger growth of CdZnTe crystals. We have emphasized the pred iction of the magnitude and distribution of residual stress and strain , as well as longitudinal and radial segregation within the boules and across wafers cut from the boules. Boule and wafer compositional dist ributions were mapped using photoreflectance, precision lattice parame ter measurements and FTIR spectroscopy. Defect and strain distribution s within the boules and wafers were imaged using synchrotron topograph y, synchrotron strain contour mapping, and double-crystal rocking-curv e mapping Thermomechanical and thermosolutal models specifically addre ssing the seeded vertical Bridgman-Stockbarger growth of CdZnTe crysta ls were developed and empiricized. These models addressed solute redis tribution and stress generation as a result of the interface shape, as pect ratio and growth parameters during the seeding, initial transient (including the shoulder), steady-state and terminal transient regions of the boule Finally, the stress and strain distributions on specific wafers 'cut' from the processed (modelled) boules were predicted and x-ray synchrotron strain contour, double-crystal rocking-curve, FTIR, and photoreflectance maps were generated on the real wafers for compar ison. Implications of these results with respect to substrate quality, screening, performance and producibility, will be discussed.