MAPPING OF CDZNTE SUBSTRATES AND CDHGTE EPITAXIAL LAYERS BY X-RAY-DIFFRACTION

A simple procedure is described for mapping of lattice parameter and X -ray rocking curve width across Cd1-yZnyTe (CZT) substrates and CdxHg1 -xTe (CMT) epitaxial layers. It is shown how screening of the crystall inity and composition of CZT substrates can be utilized to make subseq uent X-ray characterizations of epitaxial layers more reliable. This a lso allows selection of substrates with a close lattice matching to a given CMT composition, to reduce or avoid layer relaxation. Substrates with laterally Varying Zn content give a Varying lattice mismatch on a single epitaxial layer. Correlation of the lattice parameter maps of substrate and layer shows the resulting variations in layer strain, a nd the onset of relaxation can be clearly identified. Mapping of rocki ng curve peak widths on good quality CZT substrates and closely lattic e matched CMT layers shows that the peak width can be below 6 arcsec, limited essentially by the intrinsic peak width of the materials. Addi tional broadening of the layer peaks is introduced primarily by substr ate defects and misfit dislocations, unless epitaxial growth condition s deviate significantly from their optimum.