IMPROVED GROWTH OF CRYSTALS FOR INFRARED DETECTORS

CDTESE HAS RECENTLY BEEN SHOWN TO HAVE EPD (ETCH PIT DENSITY) LEVELS IN THE MID-10(4)/CM(2) RANGE, AND DUE TO THEDISTRIBUTION COEFFICIENT OF SE (1.03) IN CDTE, LARGE CRYSTALS WITH UNIFORM COMPOSITIONS AND LATTICE CONSTANTS HAVE BEEN PRODUCED BY THE VERTICAL BRIDGMAN (VB) METHOD. THESE FEATURES MAKE CDTESE SUBSTRATES AN ATTRACTIVE CHOICE FOR IMPROVED LARGE AREA, LATTICE MATCHED HGCDTE EPITAXY. LOW STRESS HORIZONTAL BRIDGMAN (HB) GROWTH PROCESSING WILL BE UTILIZED TO GROW HIGH PURITY CDTESE SINGLE CRYSTALS. THEPROCESS WILL BE TAILORED TO ELIMINATE EPD VLUSTERING AND DRIVE EPD LEVELS INTO THE 10(3)/CM(2) RANGE. GROWTH CYCLE IMPURITY CONTAMINATION, ESPECIALLY FROM CANDIDATE LOW STRESSCONTAINER MATERIALS, WILL BE INVESTIGATED. THE FEASIBILITY OF LOW STRESS HB GROWN CDTESE WILL BE INVESTIGATED. PRINCIPAL AREAS OF INTEREST WILL BE: A) UNCLUSTERED EPD LEVELS IN THE LOW 10(3)/CM(2) RANGE, B) UNIFORM SE DISTRIBUTION, THEREFORE CONSTANT LATTICE PARAMETER, C) NARROW (15 ARCSEC) X-RAY ROCKING CURVES AND MACROSCOPICALLY UNIFORM X-RAY TOPOGRAPHS OVER USEFUL SUBSTRATE AREAS, D) RETAINED HIGH PURITY OF STARTING MATERIALS, AND E) UNDERSTANDING OF PROCESS SCALABILITY TO ACHIEVE 3 X 4 CM OR LARGER SIZES.