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At least 307 records · Page 17

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NASA NTRS1977

Solid state Ku-band spacecraft transmitters

A transmitter is considered that consists of GaAs IMPATT and Read diodes operating in a microstrip circuit environment to provide amplification with a minimum of 63 db small signal gain and a minimum compressed gain at 5 W output of 57 db. Reported are Schottky-Read diode design and fabrication, microstrip and circulator optimization, preamplifier development, power amplifier development, dc-to-dc converter design, and integration of the breadboard transmitter modules. A four-stage power amplifier in cascade with a three-stage preamplifier had an overall gain of 56.5 db at 13.5 GHz with a power output of 4.5 W. A single-stage Read amplifier delivered 5.9 W with 4 db gain at 22% efficiency.

Wisseman, W. R.↗

NASA NTRS1976

A 230-GHz radiometer system employing a second-harmonic mixer

A radiometer system for use in the 1.3 mm region has been constructed and used for radio astronomical observations. A second-harmonic mixer employing a single Schottky diode downconverts the incident power to an IF frequency of about 1400 MHz. The measured double-sideband system noise temperature is 6000 K (noise figure = 13 dB) and the double-sideband mixer conversion loss is calculated to be 10 dB. The mixer is tunable over a range of at least 15 GHz.

Goldsmith, P. F.↗

NASA NTRS1977

Vacuum UV performance of silicon detectors

The sensitivity, time-varying response, and spatial sensitivity of four silicon detectors of vacuum UV were measured by passing a typical flux of 3 x 10 photons/s at the Lyman alpha line of 1215.7 A through an exit aperture of 0.55 mm x 0.8 mm. The detectors tested were: (1) a Fairchild FPM 200 silicon planar passivated photodiode with the window removed so that radiation could directly impinge on the center of the 1.0 mm square silicon chip, (2) a Fairchild FPM 100 silicon NPN planar passivated phototransistor, (3) the Hewlett-Packard 5082-4204 silicon planar PIN photodiode, and (4) the United Detector Technology PIN Spot/2 special sensitive silicon Schottky surface photodiode with the window removed.

Ohlhaber, R. L.↗

NASA NTRS1977

Laser probe for measuring 2-D wave slope spectra of ocean capillary waves

A laser-optical instrument for use in determining the two-dimensional wave-slope spectrum of ocean capillary waves is described. The instrument measures up to a 35-deg tip angle of the surface normal by measuring the position of a refracted laser beam directed vertically upward through a water surface. A telescope, a continuous two-dimensional Schottky barrier photodiode, and a pair of analog dividers render the signals independent of water height and insensitive to laser-beam intensity fluctuations. Calibration is performed entirely in the laboratory before field use. Sample records and wave-slope spectra are shown for one-dimensional wave-tank tests and for two-dimensional ocean tests. These are presented along with comparison spectra for calm and choppy water conditions. A mechanical wave follower was used to adjust the instrument position in the presence of large ocean swell and tides.

Palm, C. S.↗

NASA NTRS1977

A new mixer design for 140-220 GHz

A new Schottky-diode mixer is described which has low noise and conversion loss in the 140-220-GHz band. At 170 GHz mixer noise temperatures of 1100-1300 K have been measured, with 6.2-7.2-dB single sideboard conversion loss. The design should be usable up to about 300 GHz with appropriate scaling. The mixer has been successfully used in airborne radiometers on the NASA Convair 990 and C-141 aircraft.

Kerr, A. R.↗

NASA NTRS1977

High efficiency thin-film GaAs solar cells

Several oxidation techniques are discussed which have been found to increase the open circuit (V sub oc) of metal-GaAs Schottky barrier solar cells, the oxide chemistry, attempts to measure surface state parameters, the evolving characteristics of the solar cell as background contamination (has been decreased, but not eliminated), results of focused Nd/YAG laser beam recrystallization of Ge films evaporated onto tungsten, and studies of AMOS solar cells fabricated on sliced polycrystalline GaAs wafers. Also discussed are projected materials availability and costs for GaAs thin-film solar cells.

Stirn, R. J.↗

NASA NTRS1978

Study of electronic properties in proton- and electron-irradiated GaAlAs and GaAs solar cell materials

Diagnostical measurement techniques such as dark I-V, C-V, the thermally insulated capacitance, and the deep level transient spectroscopy methods were employed to study defect properties in the proton-irradiated n-GaAs materials. Defect energy levels, thermal emission rates, and capture cross sections of electrons as well as trap densities were deduced from these measurements and the results are presented. Correlations between the measured defect parameters and the dark I-V characteristics of the n-GaAs Schottky barrier diodes are also discussed. Defect energy levels (i.e., electron traps) determined are also compared with published data in order to identify their physical origins.

Li, S. S.↗

NASA NTRS1978

Contact Whiskers for Millimeter Wave Diodes

Several techniques are investigated for making short conical tips on wires (whiskers) used for contacting millimeter-wave Schottky diodes. One procedure, using a phosphoric and chromic acid etching solution (PCE), is found to give good results on 12 microns phosphor-bronze wires. Full cone angles of 60 degrees-80 degrees are consistently obtained, compared with the 15 degrees-20 degrees angles obtained with the widely used sodium hydroxide etch. Methods are also described for cleaning, increasing the tip diameter (i.e. blunting), gold plating, and testing the contact resistance of the whiskers. The effects of the whisker tip shape on the electrical resistance, inductance, and capacitance of the whiskers are studied, and examples given for typical sets of parameters.

Kerr, A. R.↗

NASA NTRS1977

Annual Conference on Nuclear and Space Radiation Effects, 14th, College of William and Mary, Williamsburg, Va., July 12-15, 1977, Proceedings

Topics related to processing and hardness assurance are considered, taking into account the radiation hardening of CMOS technologies, technological advances in the manufacture of radiation-hardened CMOS integrated circuits, CMOS hardness assurance through process controls and optimized design procedures, the application of operational amplifiers to hardened systems, a hard off-the-shelf SG1524 pulse width modulator, and the gamma-induced voltage breakdown anomaly in a Schottky diode. Basic mechanisms are examined, giving attention to chemical and structural aspects of the irradiation behavior of SiO2 films on silicon, experimental observations of the chemistry of the SiO2/Si interface, leakage current phenomena in irradiated SOS devices, the avalanche injection of holes into SiO2, the low-temperature radiation response of Al2O3 gate insulators, and neutron damage mechanisms in silicon at 10 K. Other subjects discussed are related to radiation effects in devices and circuits, space radiation effects, and aspects of simulation, energy deposition, and dosimetry.

Stahl, R. H.↗

NASA NTRS1977

Detection of upper atmospheric constituents using submillimeter wave /SMMW/ heterodyne radiometry

Submillimeter wave heterodyne radiometry has been applied to the detection and sounding of upper atmospheric constituents. The use of room-temperature Schottky-diode mixers for the receivers has yielded measurements of 70,000 K noise temperature. Coupling losses into the diode and matching of the IF output limit are observed to limit noise temperature. The technique is evaluated by calculating spectra with assumed temperature and constituent profiles. Vertical integrations are made with a multilayer atmosphere and the direct summation of absorption coefficients for the individual spectral lines is used. Results are presented for tangent path parameters for a mid-latitude summer model and the fractional parts of upper atmospheric constituents as a function of altitude.

Mcavoy, N.↗

NASA NTRS1978

Defect distribution near the surface of electron-irradiated silicon

The surface-defect distributions of electron-irradiated n-type silicon have been investigated using a transient capacitance technique. Schottky, p-n junction, and MOS structures were used in profiling the defect distributions. Surface depletions of defects observed were attributed to the vacancy distribution, but not that of oxygen, and other capture centers' distributions. The vacancy diffusion length at 300 K was estimated to be about 3-6 microns.

Wang, K. L.↗

NASA NTRS1978

Back wall solar cell

A solar cell is disclosed which comprises a first semiconductor material of one conductivity type with one face having the same conductivity type but more heavily doped to form a field region arranged to receive the radiant energy to be converted to electrical energy, and a layer of a second semiconductor material, preferably highly doped, of opposite conductivity type on the first semiconductor material adjacent the first semiconductor material at an interface remote from the heavily doped field region. Instead of the opposite conductivity layer, a metallic Schottky diode layer may be used, in which case no additional back contact is needed. A contact such as a gridded contact, previous to the radiant energy may be applied to the heavily doped field region of the more heavily doped, same conductivity material for its contact.

Brandhorst, H. W., Jr.↗

NASA NTRS1979

The low-noise 115-GHz receiver on the Columbia-GISS 4-ft radio telescope

The superheterodyne millimeter-wave radiometer on the Columbia-GISS 4-ft telescope is described. This receiver uses a room-temperature Schottky diode mixer, with a resonant-ring filter as LO diplexer. The diplexer has low signal loss, efficient LO power coupling, and suppresses most of the LO noise at both sidebands. The receiver IF section has a parametric amplifier as its first stage with sufficient gain to overcome the second-stage amplifier noise. A broad-banded quarter-wave impedance transformer minimizes the mismatch between mixer and paramp. At 115 GHz, the SSB receiver noise temperature is 860 K, which is believed to be the lowest figure so far reported for a room-temperature receiver at this frequency.

Cong, H.-I.↗

NASA NTRS1978

Progress towards high efficiency polycrystalline thin-film GaAs AMOS solar cells

Results of Ge film recrystallization using focused laser beams and GaAs film growth on such layers in the making of high efficiency thin-film AMOS solar cells are discussed. Since a conversion efficiency of 14% was obtained for an AMOS cell fabricated on sliced bulk polycrystalline GaAs, high efficiency cells are being developed by chemically vapor-depositing GaAs films on previously recrystallized evaporated Ge films to minimize the grain boundary (GB) effects. Schottky barrier solar cells made on sliced polycrystalline GaAs wafers were studied to investigate the effects of grain boundaries on cell properties and the potential efficiency of GaAs thin-film cells. Ge film recrystallization and the chemical vapor deposition (CVD) of the 2 to 3 micron thick GaAs films are described. AMOS solar cells with 100 Angstrom thick Ag metallization were made on CVD GaAs/recrystallized Ge/W substrates with an energy conversion efficiency of 8%.

Yeh, Y. C. M.↗

NASA NTRS1980

RAM-Based frame synchronizer

Frame synchronizer for serial telemetry is rapidly reconfigured for changing formats. Synchronizer generates signals marking data-word boundaries, beginning of each frame, and beginning of each paragraph. Also derived are search, check, and lock status signals. Existing unit is assembled from standard random-access memory elements and MOS and low-power-Schottky logic.

Niswander, J. K.↗

NASA NTRS1979

Semiconductor millimeter and centimeter wave radiometer for the study of the radiation of an underlying surface

A theoretical and experimental investigation of a superheterodyne radiometer system with input frequency converter and intermediate frequency modulation is presented. Conditions are found, at which the temperature sensitivity of the device does not deteriorate. A sensitivity function to external parameters (temperature, heterodyne power) of a radiometer system with intermediate frequency modulation and a Schottky diode frequency converter is presented and calculated. Use of a frequency converter at the second harmonic of the heterodyne permitted simplication of the radiometer design and the use of a semiconductor heterodyne. A 3 cm range intermediate frequency amplifier permitted the use of centimeter wave radiometer signals. Fluctuation sensitivity of radiometers with a 1 sec time constant is 0.3 K at 3.4 mm and 0.06 K at 3 cm.

Bordonskiy, G. S.↗

NASA NTRS1979

InP and GaAs characterization with variable stoichiometry obtained by molecular spray

Both InP and GaAs surfaces were studied in parallel. A molecular spray technique was used to obtain two semiconductor surfaces with different superficial compositions. The structures of these surfaces were examined by electron diffraction. Electron energy loss was measured spectroscopically in order to determine surface electrical characteristics. The results are used to support conclusions relative to the role of surface composition in establishing a Schottky barrier effect in semiconductor devices.

Massies, J.↗

NASA NTRS1980

Crystal growth of device quality GaAs in space

The apparatus and techniques used in effort to determine the relationships between crystal growth and electronic properties are described with emphasis on electroepitaxy and melt-grown gallium aresenide crystal. Applications of deep level transient spectroscopy, derivative photocapitance spectroscopy, and SEM-cathodoluminescene in characterizing wide bandgap semiconductors; determining photoionization in MOS, Schottky barriers, and p-n junctions; and for identifying inhomogeneities are examined, as well as the compensation of indium phosphide.

Gatos, H. C.↗