HETEROSTRUCTURE INFRARED DETECTORS FOR USE AT WAVELENGTHS LONGER THAN 14 MICRONS

THE PROJECT WILL INVOLVE THE DEVELOPMENT OF HETEROSTRUCTURE INFRARED DETECTORS FOR USE AT WAVELENGTHS GREATER THAN 14 MICRONS AND AT OPERATING TEMPERATURES BETWEEN 40K AND 80K. THE HETEROSTRUCTURES ARE SUPERLATTICE DETECTORS OPERATED IN A PHOTOVOLTAIC MODE. A KEY FEATURE OF THE DETECTORS IS THATTHEY RELY ON INTRABAND TRANSITIONS. THIS PERMITS THE USE OFWIDE BANDGAP MATERIALS WHICH HAVE FEWER MATERIALS PROBLEMS THAN INTRINSIC, NARROW BANDGAP MATERIALS LIKE HGCDTE. THE HETEROSTRUCTURE APPROACH WILL PERMIT THE PARAMETERS CONTROLLING THE DETECTOR RESPONSE AND THE OPERATING TEMPERATURE TO BE CONTINUOUSLY ADJUSTED AND OPTIMIZED IN A WAY WHICH IS NOT POSSIBLE WITH EXTRINSIC DETECTORS. PHASE IRESEARCH WILL DEAL WITH MODELING AND CALCULATIONS OF RESPONSIVITY, DARK CURRENT, NOISE, AND DETECTIVITY AS FUNCTIONS OF THE HETEROSTRUCTURE DEVICE PARAMETERS. THE PARAMETERS WILL BE VARIED IN ORDER TO OPTIMIZE PERFORMANCE AND OPERATING TEMPERATURE. TRADEOFFS ARE ANTICIPATED BETWEEN THE MAXIMUM OPERATING TEMPERATURE AND THE LONGEST WAVELENGTH WITH USEFUL RESPONSE. THESE TRADEOFFS WILL BE QUANTITATIVELY ANALYZED. UNDER PHASE II, PROTOTYPE A1GAAS/GAAS DEVICES AND ARRAYS WILL BE FABRICATED USING MOLECULAR BEAM EPITAXY. THESE PROTOTYPE DEVICES AND ARRAYS WILL BE TESTED AND THE RESULTS WILL BE COMPARED WITH THE CALCULATIONS AND MODELING DONE UNDER PHASE I.