GAAS VERTICAL SUPERLATTICES FOR MONOLITHICALLY INTEGRATABLE LWIR DETECTOR ARRAYS

ONE PROMISING APPROACH TO THE FABRICATION OF LONG-WAVELENGTH INFRARED (LWIR) DETECTORS IS THE USE OF GAAG-A1GAAS MULTIPLE-QUANTUM-WELL (MQW) STRUCTURES, ALTHOUGH A MAJOR DIFFICULTY IS CAUSED BY THE FACT THAT, TO BE DETECTED, THE RADIATION MUST BE PARALLEL TOTHE HETEROINTERFACES. THIS IS THE PROBLEM ADDRESSED. WE PROPOSE THEDEVELOPMENT OF A TECHNOLOGY TO ACCOMPLISH ATOMIC-SACALE GROWTH OF NEARLY VERTICAL SUPERLATTICE (NVSL) STRUCTURES CONTAINING GAAS MULTIPLE QUANTUM WELLS WITH INTERFACE PLANES PERPENDICULAR TO THE GAAS WAFER SURFACE. THIS WILL PERMIT THE FABRICATION OF LWIR GAAS-A1GAAS MQW DETECTORS WHICH FUNCTION WITH IR RADIATION THAT IS NORMAL TO THE WAFER SURFACE, ALLOWING FOR THE EASY FABRICATION OF MANY-ELEMENT DETECTOR ARRAYS AND MONOLITHIC INTEGRATION OF DETECTORS WITH OTHER GAAS-BASED SIGNAL PROCESSING COMPONENTS. OUR BASIC APPROACH IS TO USE THE REGULARLY SPACED ATOMIC STEPS ON A GAAS SUBSTRATE SURFACE ORIENTED A FEW DEGREES OFFTHE (100) AXIS TO NUCLEATE AND CONTROL THE GROWTH OF NEARLY VERTICAL SUPERLATTICES; DEPOSITION WILL BE BY LOW-PRESSURE METALORGANIC CHEMICAL VAPOR DEPOSITION (MOCVD). PHASE I WILL ESTABLISH THE MOCVD TECHNOLOGY NEEDED TO PRODUCE NVSL STRUCTURES USING GAAS AND ALAS REGIONS, WILLCHARACTERIZE THE PROPERTIES OF SUCH STRUCTURES, AND WILL ATTEMPT TO DEMONSTRATE A SIMPLE NVSL LWIR PHOTOCONDUCTIVE DETECTOR. PHASE II WILLSEEK TO OPTIMIZE CONTROL OF THE GROWTH AND DOPING OF NVSL REGIONS, TODEVELOP A METHOD FOR OPTICAL CONFINEMENT, TO FABRICATE AND TEST LWIR DETECTORS AND ARRAYS, AND TO MONOLITHICALLY INTEGRATE DETECTORS WITH OTHER CIRCUIT ELEMENTS. ANTICIPATED BENEFITS/POTENTIAL COMMERCIAL APPLICATIONS - SUCCESSFUL DEVELOPMENT OF THE PROPOSED TECHNOLOGY WILL LEAD TO THE ESTABLISHMENT OF A PRODUCTION-SCALE SOURCE OF HIGH-QUALITY MANUFACTURABLE,