DEVELOPMENT OF LONG WAVELENGTH INFRARED DETECTORS FOR TRACE GAS DETECTION

LONG WAVELENGTH INFRARED (IR) DETECTORS WILL BE PRODUCED FOR APPLICATION IN TRACE GAS ANALYSIS. THE DETECTOR IS FORMED BY AN InAs/InxGa1xSb STRAINED LAYER SUPERLATTICE (SLS). IT WILL BE DEMONSTRATED IN THIS PROJECT THAT InAs/InxGa1xSb SLSs WITH EFFECTIVE BAND GAPS OVER A WIDE RANGE OF THE IR SPECTRUM CAN BE GROWN AND LATTICE-MATCHED TO GaSb SUBSTRATES (aGaSb=6.0959A) BY PROPERLY DESIGNING THE ALLOY COMPOSITIONS AND LAYER THICKNESSES OF THE SLSs. THE USE OF LATTICE-MATCHED STRUCTURES WILL ELIMINATE OR SIGNIFICANTLY MINIMIZE THE FORMATION OF MISFIT DISLOCATIONS IN THE ACTIVE LAYERS WHICH ACT AS SCATTERING CENTERS AND CONSEQUENTLY DEGRADE THE ELECTRICAL PROPERTIES OF THE DETECTORS. HENCE, HIGH STRUCTURAL AND ELECRICAL QUALITY WILL BE MAINTAINED BY ELIMINATING THE DOMINANT DISLOCATION SCATTERING. IN PHASE I MOLECULAR BEAM EPITAXY WILL BE USED TO DEPOSIT InAs/InxGa1xSb SLSs CORRESPONDING TO A CUTOFF WAVELENGTH OF ABOUT 8u ON GaSb SUBSTRATES. THE STRUCTURAL PARAMETERS AND PHOTORESPONSE OF THE GROWN FILMS WILL BE STUDIED. FILMS DEMONSTRATING GOOD STRUCTURAL QUALITY AND DESIRED PHOTORESPONSE WILL BE PROCESSED INTO DEVICES WHICH, IN TURN, WILL BEELECTRICALLY AND OPTICALLY CHARACTERIZED. IN PHASE II, THE DESIGN AND GROWTH OF InAs/InxGa1xSbSLSs AS WELL AS DEVICE PROCESSING WILL BE REFINED BASED ON THE RESULTS OBTAINED IN PHASE I,AND A PROTOTYPE TRACE GAS ANALYZER WILL BE DEMONSTRATED.