LEAD-SALT MATERIALS DEVELOPMENT FOR LONG WAVELENGTH DIODE LASER

LEAD-SALTS HAVE BEEN THE ONLY SEMICONDUCTOR ALLOYS OF CAPABLE OF DIODE LASER EMISSION IN THE MID-INFRARED (3-30 UM). THESE DEVICES WERE HOMOSTRUCTURE DIFFUSED DIODE LASERS WHICH OPERATED CONTINUOUSLY ONLY AT CRYOGENIC TEMPERATURES. SUBSTANTIAL IMPROVEMENTS IN LEAD-SALT DIODE LASER PERFORMANCE HAVE BEEN REALIZED IN THE LAST DECADE FOLLOWING THE INTRODUCTION OF MOLECULAR BEAM EPITAXY (MBE) TECHNOLOGY. THE ABILITY TO CONTROL PRECISELY THE EPITAXIAL GROWTH ENABLED THE DEVELOPMENT OF BURIED DOUBLE HETEROSTRUCTURE AND QUANTUM WELL LASERS WITH CONTINUOUS OPERATION ABOVE 200 K. FURTHER PROGRESS IN LEAD-SALT TECHNOLOGY REQUIRES BOTH OPTIMIZATION OF DEVICE PARAMETERS AND IMPROVEMENT IN DEVICE PROCESSING. WE PROPOSE TO CONDUCT A COMPREHENSIVE THEORETICAL ANALYSIS WHICH WILL ENABLE US TO PREDICT THE TEMPERATURE LIMITS OF CONTINUOUS WAVE OPERATION WHILE DETERMINING OPTIMAL LASER PARAMETERS SUCH AS DOPING PROFILES, CLADDING LAYER COMPOSITION AND THICKNESS AND ACTIVE LAYER THICKNESS AND SHAPE. THESE PARAMETERS WILL BE DETERMINED BY CONDUCTING OPTIMIZATION CALCULATIONS ON THE MINORITY CARRIERS LIFETIME, INFLUENCE ON THE FREE CARRIER ABSORPTION ON MINORITY CARRIERS INJECTION LEVEL AND THE INFLUENCE OF THE THERMAL CONDUCTIVITY ON LAYER THICKNESS AND DEVICE STRUCTURE. THE STATE-OF-THE-ART LEAD-SALT LASER TECHNOLOGY WILL BE ANALYZED IN ORDER TO RECOMMEND MATERIAL PROCESSING IMPROVEMENTS INTENDED TO REDUCE DISLOCATIONS WHICH ARE MAJOR CONTRIBUTOR TO NONRADIATIVE RECOMBINATIONS AND THEREFORE TO LOW DIFFERENTIAL QUANTUM EFFICIENCIES. THE DEVELOPMENT OF MID-IR DIODE LASERS CAPABLE OF OPERATION AT OR NEAR ROOM TEMPERATURE WILL LEAD TO MANY APPLICATIONS WHICH HAVE BEEN PREVIOUSLY PRECLUDED BY STRINGENT CRYOGENIC COOLING REQUIREMENTS. THESE INCLUDE MILITARY APPLICATIONS IN THE AREAS OF COMMUNICATIONS, IR SENSING, AND IR SYSTEM TEST AND CALIBRATION. COMMERCIAL APPLICATIONS INCLUDE LOW COST, HIGH PERFORMANCE SYSTEMS FOR INDUSTRIAL AND AIR POLLUTION MONITORING, MEDICAL DIAGNOSTICS, AND OTHER ANALYTICAL APPLICATIONS.9116703WE PROPOSE TO FABRICATE DOUBLE HETEROJUNCTION (DH) PBS/PBSSE/PBS LASER DIODES USING MOLECULAR BEAM EPITAXY (MBE). USING MBE BANDGAP ENGINEERING, THE PBSSE EPITAXIAL LAYER WILL BE TAILORED FOR A SPECIFI