GROWTH AND CHARACTERIZATION OF CD(1-X)ZN(X)TE SINGLE CRYSTALS

MERCURY CADMIUM TELLURIDE (MCT) HAS EMERGED AS THE SUPERIOR MATERIAL FOR INFRARED APPLICATIONS IN IMPORTANT 3-5 MICROMETER AND 8-13 MICROMETER RANGES CORRESPONDING TO ATMOSPHERIC WINDOWS. BULK GROWTH METHODS CANNOT PROVIDE DEVICE GRADE LARGE AREA CRYSTALS OF THIS MATERIAL. HENCE, IN ORDER TO REALIZE THE STATE-OF-THE-ART LARGE AREA DEVICES, EPITAXIAL GROWTH IS THE ONLY PLAUSIBLE TECHNIQUE AT THE PRESENT. FOR PRODUCING DEVICE GRADE EPITAXIAL ALYERS, GOOD QUALITY SUBSTRATES IS THE ESSENTIAL REQUIREMENT. CDTE IS THE COMMONLY USED SUBSTRATE MATERIAL FOR MCT EPITAXY. IT IS EXTREMELY DIFFICULT TO GROW LARGE, TWIN FREE CDTE CRYSTALS WITH LOW DISLOCATION DENSITY. THE ALTERNATIVE SUBSTRATE MATERIAL IS CD(1-X)ZN(X)TE WHICH CAN BE GROWN WITH BETTER CRYSTALLOGRAPHIC PERFECTION. HOWEVER, GROWTH OF COMPOSITIONALLY UNIFORM CRYSTAL IS VERY DIFFICULT DUE TO METALLURGICAL NATURE OF CD(1-X)ZN(X)TE. IN THIS PROPOSAL A TECHNIQUE TO GROW LARGE,SUBSTRATE QUALITY CRYSTAL OF CD(1-X)ZN(X)TE USING ZONE LEVELING/ MELTING IS SUGGETED. THE GROWTH SYSTEM HAS A VERTICAL CONFIGURATION. GROWTH AMPOULE HAS PRACTICALLY NO FREE VOLUME OVER THE STOICHIOMETRIC CHARGE WHICH IS IN FORM OF SOLID INGOT. THIS WILL PREVENT FORMATION OF VOIDS AND LOSS OF MATERIAL BY SUBLIMATION/EVAPORATION DURING THE GROWTH PROCESS. MULTIPLE ZONE LEVELING PASSES WILL HOMOGENIZE THE COMPOSITION OVER THE ENTIRE INGOT AND A FINAL ZONE MELTING PASS WITH PREDETERMINED SPEED WILL GROW THE SINGLE CRYSTAL. THESE CRYSTALS WILLBE COMPLETELY CHARACTERIZED WITH RESPECT TO MICRO-STRUCTURE USING MICROSCOPIC AND ADVANCED X-RAY DIFFRACTION TECHNIQUES AND ELECTRICAL CHARACTERIZATION WILL BE CARRIED OUT USING HALL MEASUREMENTS AND PHOTOLUMINESCENCE SPECTROSCOPY. FROM THE CORRELATION BETWEEN GROWTH CONDITIONS AND CRYSTAL QUALITY, TECHNIQUE TO GROW DEVICE GRADE CRYSTALS WILL BE DEVELOPED.