CHARACTERIZATION OF SOME QUATERNARY DEFECT CHALCOPYRITES AS USEFUL NONLINEAR OPTICAL AND SOLAR-CELL MATERIALS

The ternary chalcopyrite semiconductors together with a few ternary defect compounds have emerged as useful nonlinear materials for nonlinear laser devices. We have studied some quaternary defect compounds and evaluated the dielectric constant as well as refractive indices and optical nonlinearities of these materials (since compounds with high value of refractive indices have higher nonlinearity) using the quantum dielectric theory of Phillips and Van Vechten and the bond-charge model of Levine and its modification for multinary compounds by Samanta et al. Other important band-structure parameters such as crystal-field splitting (CF) and spin-orbit splitting (s.o.) have been evaluated and the contribution of tetragonal distortion to birefringence has been discussed. We have been able for the first time to show a correlation between the band-gap energy and tetragonal distortion, and finally the importance of these crystals in context to nonlinear laser devices and solar cells has been pointed out. © 1990 The American Physical Society.