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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Seed substrate pulled under InGaAsP wipe melt at temperature of 650 degrees C for approximately 15 to 60 seconds. After pullthrough and meltback, surface has high smoothness and luster without meniscus lines, exaggerated erosion, pits, and pearls characteristic of other wipe melts. Layer-to-substrate interface structure is more planar and of better quality. New combination of elements leaves smooth high luster surface.
Major industry is beginning to be devoted to indium phosphide and its potential applications. Key to these applications are high speed and radiation tolerance; however the high cost of indium phosphide may be an inhibitor to progress. The broad applicability of indium phosphide to many devices will be discussed with an emphasis on photovoltaics. Major attention is devoted to radiation tolerance and means of reducing cost of devices. Some of the approaches applicable to solar cells may also be relevant to other devices. The intent is to display the impact of visionary leadership in the field and enable the directions and broad applicability of indium phosphide.
A program to develop a monolithic W-band low noise amplifier (a critical element in any W-band communications, sensors, or radar application) is described. Goals of the program include a completely monolithic low noise amplifier, less than a 3.5 dB noise figure, and a monolithic mixer suitable for integration with the LNA.
The Earth Observing System (EOS), which is part of the International Mission to Planet Earth, is NASA's main contribution to the Global Change Research Program which opens a new era in international cooperation to study the Earth's environment. Five large platforms are to be launched into polar orbit, two by NASA, two by ESA, and one by the Japanese. In such an orbit the radiation resistance of indium phosphide solar cells combined with the potential of utilizing five micron cell structures yields an increase of 10 percent in the payload capability. If further combined with the advanced photovoltaic solar array the payload savings approaches 12 percent.
Heteroepitaxial (InP/GaAs) and homo-epitaxial (InP/InP) cells were irradiated by 1-MeV electrons and their performance, temperature dependencies and carrier removal rates determined. The radiation resistances of the InP/GaAs cells were significantly higher than that of the InP/InP cells. This was attributed to the high dislocation density present in the heteroepitaxial cells. In addition, the effects of dislocations in these latter cells were dominant in determining the temperature dependence of open-circuit voltage.
Experimental characteristics of monolithic InAlAs/InGaAs HEMT mixers are presented together with a theoretical analysis. Experiments at W-band show a maximum conversion gain of 0.9 dB with 2 dBm of LO power level. This is the first demonstration of a monolithic HEMT mixer with conversion gain at W-band. The conversion gain dependence on LO power, RF frequency and gate bias is measured and compared with the theoretical predictions. Good agreement between the theory and experiment could be found.
Research has shown that with proper choice of material, low-resistance contact pads deposited on solar cells and other devices by improved technique that does not involve sintering. Research directed at understanding mechanisms involved in contact-sintering process has resulted in identification of special group of materials that includes phosphides of gold, silver, and nickel; specifically, Au(2)P(3), AgP(2), and Ni(3)P. Incorporation of phosphide interlayer substantially reduces resistivity between gold current-carrying layer and indium phosphide substrate. Further research indicated only very thin interlayer of any of these compounds needed to obtain low contact resistance, without subjecting contact to destructive sintering process.
As part of a continuing program to determine the space radiation resistance of InP/ln(0.53)Ga(0.47)As tandem solar cells, n/p In(0.53)Ga(0. 47)As solar cells fabricated by RTI were irradiated with 1 MeV electrons and with 3 MeV protons. The cells were grown with a 3 micron n-lnP window layer to mimic the top cell in the tandem cell configuration for both AMO solar absorption and radiation effects. The results have been plotted against 'displacement damage dose' which is the product of the nonionizing energy loss (NIEL) and the particle fluence. A characteristic radiation damage curve can then be obtained for predicting the effect of all particles and energies. AMO, 1 sun solar illumination IV measurements were performed on the irradiated InGaAs solar cells and a characteristic radiation degradation curve was obtained using the solar cell conversion efficiency as the model parameter. Also presented are data comparing the radiation response of both n/p and p/n (fabricated by NREL) InGaAs solar cells as a function of base doping concentration. For the solar cell efficiency, the radiation degradation was found to be independent of the sample polarity for the same base doping concentration.
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This paper presents the designs and measurement results of a three-stage and a four-stage W-band monolithic microwave integrated circuits (MMIC) including a three-stage and a four-stage low noise amplifiers.
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With operational spacecraft in excess of 10 astronomical units from Earth, NASA's Deep Space Network requires sensitive receivers for detection of weak spacecraft signals.
This paper presents an overview of this development process with emphasis on comparison between modeled and measured, LNA modules, front-end receiver packages employing these modules, and antennae employing these packages.
We have demonstrated red-shifting of the wavelength response of a bound-to-continuum p-type ultra-thin InGaAs/Inp quantum well infrared photodetector after growth via rapid thermal annealing. Compared to the as-grown detector, the peak spectral response of the annealed detector was shifted to longer wavelength without any major degradation in responsivity characteristics.
Alternative approaches for developing 2.0- 2.5 um single frequency semicondoctor lasers are reviewed.
In this paper the emphasis is on accurate majority carrier concentration EC-V profiling of structures based on Indium Phosphide and Gallium Arsenide, using a newly developed electrolyte based on Hydrogen Flouride, Acetic Acid, Phosphoric Acid, 1-phenyl-2-propanamine and Ammonia Diflouride. Some preliminary data on the use of this electrolyte for determining the energy distribution of surface and deep states of these structures, applicable to fabrication process optimization and radiation induced defects studies of solar cells, are also provided.