Cadmium Telluride Modulator Material.
Annual technical rept. 1 Dec 70-30 Apr 71,
HUGHES RESEARCH LABS MALIBU CALIF
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The growth of single-crystal cadmium telluride by a modified Bridgman technique is being investigated to improve the material for use in infrared modulator devices. This investigation also provides evaluation criteria for use as an infrared window. A systematic variation of selected crystal growth parameters, together with quench and post-growth thermal anneal parameters, is being performed to accomplish this goal. Variation in crucible configuration, utilizing a ball-shaped tip, has shown promise for improved crystallinity of CdTe ingots all runs using this crucible showed single crystal starts. Installation of a new furnace with increased hot zone promises greater modulator rod yield and longer lengths. Two types of defects - inclusions and random planar 111 imperfections - have been observed in some CdTe crystals. Heat treatment improves absorption properties of crystals with in-grown inclusions, but measured values of absorption coefficient of these crystals do not attain the range of 0.001 to 0.005cm, typical of material with no initial defects. The technique used for measurement of the electro-optic coefficient is described. Author