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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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Low-power devices susceptible to cosmic-ray particles. Five MSI device technologies, including TTL, low power TTL, Schottky, CMOS, and low-power Schottky, subjected to 120-MeV krypton-ion beam from cyclotron and monitored for single-event upset. Results find terrestrial application for radiation hardening of electronic devices and systems.
Results of an ongoing research program into the reliability of terrestrial solar cells are presented. Laboratory accelerated testing procedures are used to identify failure/degradation modes which are then related to basic physical, chemical, and metallurgical phenomena. In the most recent tests, ten different types of production cells, both with and without encapsulation, from eight different manufacturers were subjected to a variety of accelerated tests. Results indicated the presence of a number of hitherto undetected failure mechanisms, including Schottky barrier formation at back contacts and loss of adhesion of grid metallization. The mechanism of Schottky barrier formation is explained by hydrogen, formed by the dissociation of water molecules at the contact surface, diffusing to the metal semiconductor interface. This same mechanism accounts for the surprising increase in sensitivity to accelerated stress conditions that was observed in some cells when encapsulated.
A single drift gallium arsenide (GaAs) Schottky barrier IMPATT diode and related components were developed. The IMPATT diode reliability was assessed. A proof of concept solid state transmitter design and a technology assessment study were performed. The transmitter design utilizes technology which, upon implementation, will demonstrate readiness for development of a POC model within the 1982 time frame and will provide an information base for flight hardware capable of deployment in a 1985 to 1990 demonstrational 30/20 GHz satellite communication system. Life test data for Schottky barrier GaAs diodes and grown junction GaAs diodes are described. The results demonstrate the viability of GaAs IMPATTs as high performance, reliable RF power sources which, based on the recommendation made herein, will surpass device reliability requirements consistent with a ten year spaceborne solid state power amplifier mission.
Interest in high resolution spectrometers for the submillimeter wavelength range from 100 micron to 1,000 micron is mostly stimulated by molecular spectroscopy in radioastronomy and atmospheric physics, and by plasma diagnostic experiments. Schottky diodes in waveguide mixer technology and InSb-hot electron bolometers are successfully used in the 0.5 to a few millimeter range whereas tandem Fabry-Perot spectrometers combined with photoconductive detectors (Ge:Sb and Ge:Ga) are used for the 100 micron range. Recent research on heterodyne spectrometers, with Schottky diodes in an open structure mixer and a molecular laser as local oscillators, which can be used over the whole wavelength range is summarized.
Plasma-grown GaAs oxides and their interfaces have been characterized by measuring the electrical properties of metal-oxide-semiconductor capacitors and of Schottky junctions. The current transport mechanism in the oxide at high electrical field was found to be Frankel-Poole emission, with an electron trap center at 0.47 eV below the conduction band of the oxide. The interface-state density, evaluated from capacitance and conductance measurements, exhibits a U-shaped interface-state continuum extending over the entire band gap. Two discrete deep states with high concentration are superimposed on this continuum at 0.40 and 0.70 eV below the conduction band. The results obtained from measurements on Schottky junctions have excluded the possibility that these two deep states originate from plasma damage. Possible origins of these states are discussed in this paper.
Three specific devices were investigated: the sheet resistance device, the Schottky-barrier diode and the PIN diode. Several sheet resistance devices were fabricated and tested. Based on the encouraging results from these devices, a mask was designed and sent to a vendor and is expected to be received very soon. A set of masks for fabricating transparent cathode Schottky-barrier diodes was designed. These masks were given to NASA Goddard Space Flight Center for fabrication of the diodes. A mask set was designed to fabricate PIN diodes with transparent electrodes. With slight modifications, the same mask set also can be used to fabricate other devices, such as MESFET and the IMPATT diode.
The program had two general objectives. The first objective was to develop the two plane rectenna format for space application at 2.45 GHz. The resultant foreplane was a thin-film, etched-circuit format fabricated from a laminate composed of 2 mil Kapton F sandwiched between sheets of 1 oz copper. The thin-film foreplane contains half wave dipoles, filter circuits, rectifying Schottky diode, and dc bussing lead. It weighs 160 grams per square meter. Efficiency and dc power output density were measured at 85% and 1 kw/sq m, respectively. Special testing techniques to measure temperature of circuit and diode without perturbing microwave operation using the fluoroptic thermometer were developed. A second objective was to investigate rectenna technology for use at 20 GHz and higher frequencies. Several fabrication formats including the thin-film scaled from 2.45 GHz, ceramic substrate and silk-screening, and monolithic were investigated, with the conclusion that the monolithic approach was the best. A preliminary design of the monolithic rectenna structure and the integrated Schottky diode were made.
The Galileo probe will be subject to radiation fields and energetic particle bombardment during its outward bound journey and in orbit around Jupiter and its moons. To avoid the occurrence and propagation of effects of single event upset (SEU) bit state changes induced by the bombardments attempts were made to harden the Galileo electronics against SEUs. The hazards are especially acute for Schottky diode and low-power Schottky TTL parts. The preventive action options which were scheduled are reviewed, noting the selection of CMOS chips as replacements for SEU-susceptible devices. The simulation and risk assessment that were performed to evaluate the potential success of the replacements are summarized, with emphasis on the data employed to ensure the accuracy of the assessments and the predicted effects of SEUs in the various Galileo subsystems.
Selective doping of silicon in proposed metal silicide/silicon Schottky-barrier infrared photodetector increases maximum detectable wavelength. Stacking layers to form multiple Schottky barriers increases quantum efficiency of detector. Detectors of new type enhance capabilities of far-infrared imaging arrays. Grows by molecular-beam epitaxy on silicon waferscontaining very-large-scale integrated circuits. Imaging arrays of detectors made in monolithic units with image-preprocessing circuitry.
It is shown that large format PtSi Schottky diode infrared arrays, the Hughes 256 X 256 hybrid Schottky array in particular, are competitive alternatives to the smaller format photovoltaic arrays for ground-based astronomy. The modest quantum efficiency of the PtSi compared to the photovoltaic devices is more than compensated for by the larger format. The use of hybrid technology yields effective fill factors of nearly 100 percent, and the low dark current, noise, excellent imaging characteristics, cost, and solid nitrogen operating temperature add to the effectiveness of this array for ground-based imaging. In addition to discussing the characteristics of this array, researchers present laboratory test data and astronomical results achieved at Kitt Peak.
Buried interfaces have traditionally been inaccessible to direct investigation by surface-sensitive techniques. A unique and novel electronic probe, which is sensitive to subsurface electronic structure, has been utilized to probe Schottky barrier interfaces. The method, ballistic electron emission microscopy (BEEM), is based on scanning tunnelling microscopy (STM) techniques. A theoretical treatment has been developed to describe the ballistic electron spectra obtained by BEEM and this treatment is applied to data obtained on the Au-Si Schottky barrier interface system. Excellent agreement between experiment and theory is obtained. In addition, the treatment predicts nanometer spatial resolution for interface imaging by BEEM.
The application of ballistic-electron-emission microscopy (BEEM) to a study of the influence of GaAs(100) substrate conditions on the formation of a multidefect structure at the Au-GaAs(100) Schottky barrier interface is described. Interfaces prepared on both melt-grown GaAs(100) wafer substrates and MBF-deposited GaAs(100) buffer layers are considered. As a comparison to the study of Au-GaAs(100) interfaces, BEEM imaging is performed on Au-Si(100) interfaces. It is noted that Au-GaAs(100) interface formation is relatively insensitive to the effects of substrate surface condition and substrate bulk defect density, and that the combination of BEEM imaging and BEEM spectroscopy indicates that the heterogeneous interface defects are the result of diffusion between the Schottky barrier electrodes.
Problems, proposed solutions, and recent results related to the development of solid-state oscillators, detectors, mixers, diode multipliers, and antennas at THz frequencies are addressed. Individual topics considered include: submillimeter heterodyne remote sensing of upper atmospheric gases, planar dipole array antenna with an elliptical lens, twin slot antenna structures integrated with microbolometer detectors for 94-GHz imaging. Also discussed are: quantum-well and quantum-barrier diodes for generating submillimeter wave power, planar Schottky barrier mixer diodes for space applications at submillimeter wavelengths, GaAs Schottky barrier varactor diodes for submillimeter wavelength power generation, planar doped barrier devices for subharmonic mixers.
A theoretical comparison of various low and high order multipliers for 200 GHz and 1 THz has been carried out. Novel diodes including single barrier varactors, barrier-intrinsic-n(+)diodes and high electron mobility varactors are shown to have excellent theoretical performance, comparable or better than the conventional Schottky varactors for single and double diode frequency multipliers at millimeter and submillimeter wavelengths, whereas quantum well diodes, since they suffer from high resistive losses, are shown to be less attractive. In comparison to the conventional Schottky varactor, these new diodes have some potential advantages in their characteristics such as a stronger nonlinearity or a special symmetry. For future optimization some general comments on these advantages as well as other factors affecting multiplication are given.
Whisker-contacted GaAs Schottky barrier varactor diodes are the most common high-frequency multiplier element in use today. They are inherently simple devices that have very high frequency response and have been used to supply local oscillator power for Schottky heterodyne receivers to frequencies approaching 700 GHz. This paper discusses the development of improved varactor diode technology for space based applications at millimeter and submillimeter wavelengths.
The GaAs Schottky varactor diode is the nonlinear device most commonly used for submillimeter wave harmonic generation. Output power adequate to serve as a local oscillator source for SIS tunnel junctions has been demonstrated with whisker-contacted GaAs Schottky varactor multipliers in waveguide mounts up to about 800 GHz. In this paper, we present results for a tripler to 200 GHz using a new multiplier device, the single barrier varactor (SBV). This new varactor has a potential advantages such as stronger nonlinearities or special symmetry, which make it attractive for submillimeter wave frequency multiplication. The performance of a tripler using a SBV over a output frequency range from 186 to 207 GHz has been measured in a crossed waveguide mount. The theoretical performance of the device has been calculated using large signal analysis. A comparison of theoretical and measured results and a discussion of various losses in the mount and the varactor have also been presented.
By incorporating a 1-nm-thick p(+) doping spike at the PtSi/Si interface, we have successfully demonstrated extended cutoff wavelengths of PtSi Schottky infrared detectors in the long wavelength infrared (LWIR) regime for the first time. The extended cutoff wavelengths resulted from the combined effects of an increased electric field near the silicide/Si interface due to the p(+) doping spike and the Schottky image force. The p(+) doping spikes were grown by molecular beam epitaxy at 450 C, using elemental boron as the dopant source, with doping concentrations ranging from 5 x 10 exp 19 to 2 x 10 exp 20/cu cm. Transmission electron microscopy indicated good crystalline quality of the doping spikes. The cutoff wavelengths were shown to increase with increasing doping concentrations of the p(+) spikes. Thermionic emission dark current characteristics were observed and photoresponses in the LWIR regime were demonstrated.
The GaAs Schottky varactor diode is the nonlinear device most commonly used for submillimeter wave harmonic generation. Output power adequate to serve as a local oscillator source for SIS tunnel junctions has been demonstrated with whisker-contacted GaAs Schottky varactor multipliers in waveguide mounts up to about 800 GHz. In this paper, we present results for a tripler to 200 GHz using a new multiplier device, the single barrier varactor (SBV). This new varactor has potential advantages such as stronger nonlinearities or special symmetry, which make it attractive for submillimeter wave frequency multiplication. The performance of a tripler using a SBV over a output frequency range from 186 to 207 GHz has been measured in a crossed waveguide mount. The theoretical performance of the device has been calculated using large signal analysis. A comparison of theoretical and measured results and a discussion of various losses in the mount and the varactor have also been presented.