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NOTICEThis report was prepared as an account of work sponsored by the United States Government. Neither the United States, nor the United States Department of Energy, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liabfity or responsibility for the accuracy, completeness or usefulness of any information, apparatus, product or process disclosed, or represents that its use would not infringe privately owned rights. they remain in the emitter for a much longer bulk-recombination time, and therefore, they are more likely to recombine at the interface. A factor of 2.2 increase in S from 5 to 11 x 10' a n / s produces a 25-mV decrease in V , a 12-% decrease in J, or quantum efficiency, and a factor of two increase in J,. This work points out the critical importance of interfacial recombination even in efficient TPV cells.

Abstract. Thermophotovoltaic (TPV) diodes fabricated from 0.52eV lattice-matched InGaAsSb alloys are grown by Metal Organic Vapor Phase Epitaxy (MOVPE) on GaSb substrates. 4cm 2 multi-chip diode modules with front-surface spectral filters were tested in a vacuum cavity and attained measured efficiency and power density of 19% and 0.58 W/cm 2 respectively at operating at temperatures of T radiator = 950 °C and T diode = 27 °C. Device modeling and minority carrier lifetime measurements of double heterostructure lifetime specimens indicate that diode conversion efficiency is limited predominantly by interface recombination and photon energy loss to the GaSb substrate and back ohmic contact. Recent improvements to the diode include lattice-matched p-type AlGaAsSb passivating layers with interface recombination velocities less than 100 cm/s and new processing techniques enabling thinned substrates and back surface reflectors. Modeling predictions of these improvements to the diode architecture indicate that conversion efficiencies from 27-30% and ~0.85 W/cm 2 could be attained under the above operating temperatures.

The creation of curved CCD's and the mosaicing of contoured CCD's mounted within the curved focal planes of telescopes and stereo panoramic imaging cameras introduces a revolution in optical design that greatly enhances the scientific potential of such instruments. In the alteration of the primary detection surface within the instrument's optical system from flat to curved, and precisely matching the applied CCD's shape to the contour of the curved focal plane, a major increase in the amount of transmittable light at various wavelengths through the system is achieved, thereby enabling multi-spectral ultrasensitive imaging for a variety of experiments simultaneously, including autostereoscopic image acquisition. For earth-based and space-borne optical telescopes, the advent of curved CCD's as the principle detectors provides a simplification of the telescope's adjoining optics, reducing the number of optical elements and the occurrence of optical aberrations associated with large corrective optics used to conform to flat detectors. New astronomical experiments may be devised in the presence of curved CCD applications, including 3 dimensional imaging spectroscopy conducted over multiple wavelengths simultaneously, wide field real-time stereoscopic tracking of remote objects within the solar system at high resolution, and deep field mapping of distant objects such as galaxies with much greater precision and over larger sky regions. Stereo panoramic cameras equipped with arrays of curved CCD's will require less optical glass and no mechanically moving parts to maintain proper stereo convergence over wider perspective viewing fields than their flat CCD counterparts, making the cameras lighter and faster in their ability to scan and record 3 dimensional objects moving within an industrial or terrain environment. Preliminary experiments conducted at the Sarnoff Corporation indicate the feasibility of curved CCD imagers with acceptable electro-optic integrity. Currently, we are in the process of evaluatingthe electro-optic performance of a curved wafer scale CCD imager. Detailed ray trace modeling and experimental electro-optical data performance obtained from the curved imager will be presented at the conference.