INTELLIGENT CONTROL OF BRIDGMAN CDZNTE CRYSTAL GROWTH

LARGE, HIGH QUALITY CDZNTE SINGLE CRYSTALS AREREQUIRED AS HGCDTE EPITAXIAL SUBSTRATES IN THE MANUFACTURE OF INFRARED FOCAL PLANE ARRAYS. BRIDGMAN GROWTH PROCESSES ARE CURRENTLY EMPLOYED TO PRODUCE MATERIALS WHICH MEET SOME APPLICATION REQUIREMENTS, BUT FALL SHORT IN MANY STATE-OF-THE-ART EPITAXIAL HGCDTE DEVICES. BRIDGMANTECHNIQUES, BEING MELT PROCESSES, ARE STRONGLY INFLUENCED BY INTRICATE COUPLING BETWEEN HEAT AND MASS TRANSFER AND METAL FLOW. THE PROCESSES ARE CONTROLLED BY REGULATING SYSTEM GEOMETRIES, GROWTH RATES, AMBIENT ATMOSPHERES AND APPLIED THERMAL GRADIENTS. PROCESS INTRICACIES ANDDEVIATIONS HAVE A PARTICULARLY LARGE EFFECT ON CDTE FAMILY CRYSTAL QUALITY DUE TO PARTICULARLY LARGE EFFECT ON CDTE FAMILY CRYSTAL QUALITY DUE TO THE LOW THERMAL CONDUCTIVITIES, STACKING FAULT ENERGIES AND YIELD STRENGTHS OF THESE MATERIALS. THIS PROJECT WILL STUDY THE APPLICATION OF INTELLIGENT PROCESSING OF MATERIALS (IPM) TECHNIQUES TO BRIDGMAN CDZNTE CRYSTAL GROWTH. THE OBJECTIVES OF HIGHER QUALITY, HIGHER YIELD AND LOWER COST WILL BE SOUGHT THROUGH THE APPLICATION OF ADVANCED SENSORS, INTELLIGENT ASSESSMENT AND ADAPTIVE CONTROL. IN PHASE I, AN ADVANCED TEMPERATURE SENSOR SYSTEM WILL BE DEVELOPED AND DEMONSTRATED AND THE CONCEPTUAL DESIGN OF AN IPM SYSTEM WILL BE PERFORMED. DURING PHASE II, IPM CONTROL OF METAL CONVECTION, LIQUID/SOLID INTERFACE SHAPE, GROWN-IN STRESS, DISLOCATION GENERATION, PRECIPITATE FORMATION AND/OR IMPURITY SEGREGATION WILL BE DEMONSTRATED. ANTICIPATED BENEFITS/POTENTIAL COMMERCIAL APPLICATIONS - IPM ENHANCED PRODUCIBILITY OF CDZNTESUBSTRATES WILL DRIVE HIGHER QUALITY, HIGHER YIELD HGCDTE EPITAXIAL MATERIALS LEADING TO HIGHER PERFORMANCE, LOWER COST IR FOCAL PLANE ARRAYS. THESE DEVICES WILL ENHANCE MANY DOD INFRARED SYSTEMS AND, IF COSTS ARE LOW ENOUGH, ENABLE COMMERCIAL IR