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Results for “ohmic contacts”

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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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Effect of counterions on the formation of ohmic contact between p-Si and poly(pyrrole) film - An ac impedance analysis

Conditions under which poly(pyrrole) (PP) films form ohmic contact with single-crystal p-Si are described. Counterions affect both the conductivity and flatband potential, V(FB), values of poly(pyrrole). While paratoluene-sulfonate-doped PP acts like a switch, the impedance behavior of PP films doped with ClO4(-), BF4(-), or PF6(-) allows evaluation of the V(FB) of these films. The formation of 'quasi-ohmic' and 'nonohmic' contacts, respectively, of PP (ClO4) and PP films doped with other counterions, with p-Si, are explained in terms of conductivity of these films and V(FB) of PP films with respect to that of p-Si. PP film seems to passivate or block intrinsic surface states present on p-Si surface.

Nagsubramanian, G.↗
NASA NTRS1980

Ohmic contact for P type indium phosphide

A body including P type indium phosphide has an ohmic contact thereon of an alloy of by weight 81% to 86% gold (Au), 11% to 14% germanium (Ge) and 2% to 5% zinc (Zn). This contact has a low resistance and good adhesion to the indium phosphide body.

Hawrylo, Frank Z.↗
NASA NTRS1977

Semiconductor ohmic contact

A semiconductor device has one surface of P type conductivity material having a wide energy bandgap and a large crystal lattice parameter. Applied to the P type surface of the semiconductor device is a degenerate region of semiconductor material, preferably a group III-V semiconductor material, having a narrower energy bandgap. The degenerate region is doped with tin to increase the crystal lattice of the region to more closely approximate the crystal lattice of the one surface of the semiconductor device. The degenerate region is compensatingly doped with a P type conductivity modifier. An electrical contact is applied to one surface of the degenerate region forming an ohmic contact with the semiconductor device.

Hawrylo, Frank Zygmunt↗
NASA NTRS2018

Single Conductor Alloy as Diffusion Barrier System and Simulataneous OHMIC Contact to N- and P-Type Silicon Carbide

Use of a single alloy conductor to form simultaneous ohmic contacts (SOC) to n- and p-type 4H-SiC. The single alloy conductor also is an effective diffusion barrier against gold (AU) and oxygen (O.sub.2) at high temperatures (e.g., up to 800.degree. C.). The innovation may also provide an effective interconnecting metallization in a multi-level metallization device scheme.

Okojie, Robert S.↗
NASA NTRS2001

Low Temperature Ohmic Contact Formation of Ni2Si on N-type 4H-SiC and 6H-SiC

Nickel Silicide (Ni2Si) is investigated as possible ohmic contact to heavily nitrogen-doped N-type 4H-SiC and 6H-SiC. Nickel Silicide was deposited via electron gun with various thicknesses on both Si and C faces of the SiC substrates. The Ni2Si contacts were formed at room temperature as well as at elevated temperatures (400 to 1000 K). Contact resistivities and I-V characteristics were measured at temperatures between 100 and 700 C. To investigate the electric properties, I-V characteristics were studied and the Transmission Line Method (TLM) was used to determine the specific contact resistance for the samples at each annealing temperature. Both Rutherford Backscattering Spectroscopy (RBS) and Auger Electron Spectroscopy (AES) were used for depth profiling of the Ni2Si, Si, and C. X-ray Photoemission Spectroscopy (XPS) was used to study the chemical structure of the Ni2Si/SiC interface.

Elsamadicy, A. M.↗
NASA NTRS2005

Carbon nanotube Schottky diodes using Ti-Schottky and Pt-ohmic contacts for high frequency applications

We have demonstrated Schottky diodes using semiconducting single-walled nanotubes (s-SWNTs) with titanium Schottky and platinum Ohmic contacts for high-frequency applications. The diodes are fabricated using angled evaporation of dissimilar metal contacts over an s-SWNT. The devices demonstrate rectifying behavior with large reverse bias breakdown voltages of greater than 15 V. To decrease the series resistance, multiple SWNTs are grown in parallel in a single device, and the metallic tubes are burnt-out selectively. At low biases these diodes showed ideality factors in the range of 1.5 to 1.9. Modeling of these diodes as direct detectors at room temperature at 2.5 terahertz (THz) frequency indicates noise equivalent powers (NEP) potentially comparable to that of the state-of-the-art gallium arsenide solid-state Schottky diodes, in the range of 10-13 W(square root)xHz.

semiconducting↗
NASA NTRS1980

Ohmic contact to GaAs semiconductor

Multimetallic layers produce stable, low-resistance contacts for p-type GaAs and p-type GaAlAs devices. Contacts present no leakage problems, and their series resistance is too small to measure at 1 Sun intensity. Ohmic contacts are stable and should meet 20-year-life requirement at 150 C for GaAs combined photothermal/photovoltaic concentrators.

Hovel, H. J.↗
NASA NTRS2007

Flexible carbon-based ohmic contacts for organic transistors

The present invention relates to a system and method of organic thin-film transistors (OTFTs). More specifically, the present invention relates to employing a flexible, conductive particle-polymer composite material for ohmic contacts (i.e. drain and source).

Brandon, Erik↗
NASA NTRS1992

Effects of ultra-vacuum and space environment on contact ohmic resistance: LDEF experiment AO 138-11

The FRECOPA experimentation of chemical resistance of electrical connector contacts, as described, has evidenced the detrimental time variations of nickel plated conductors and gilded copper contacts, irrespective of crimping storage or metal peening conditions. With a view to reorient aluminum technology a silvered aluminum conductor/gilded aluminum contact solution was evaluated.

Assie, Jean-Pierre↗
NASA NTRS1991

Effects of ultravacuum and space environment on contact ohmic resistance (AO 138-11)

The experiment was aimed at checking compatibility of the aluminum conductors with conventional conductors and contacts under different conditions of manufacturing (mechanical or magnetostrictive crimping) and storage in laboratory or in long-duration space environment. The electrical characteristics of connections built from nickel-plated conductors and glided copper contacts were noted to vary over the duration of the experiment. These variations are unrelated with the crimping or storage conditions or with metal pairing (nickel-plated aluminum/tinned or silver copper). Such evolutions, even slight, are detrimental to connection quality. The same observations hold for some like connections subjected to long-duration thermal cycles. Therefore, work on aluminum technology was reoriented toward a silver aluminum conductor/ golded aluminum contact solution. The first evaluation test performed according to this definition have yielded satisfactory results.

Assie, Jean Pierre↗
NASA NTRS1977

Semiconductor ohmic contact

Contact formed on p-type surface of semiconductor laser has several advantages: highly conductive degenerate region and narrow band gap provides surface for good metal-to-semiconductor contact; lattice parameter of GaAs is 5.6533 A; improved lattice match eases interface strain which reduces interface cracking of semiconductor material.

Hawrylo, F. Z.↗
NASA NTRS1979

Intercell ohmic contacts for high efficiency multijunction solar converters

The monolithic multijunction converter is an attractive approach to achieving solar/electric conversion with greater than 30% efficiency. A major technical challenge in the development of such devices is the requirement for low resistance, optically transparent intercell contacts between adjacent junctions. These contacts should transmit, without significant loss, the spectral fraction of the incident sunlight which is not absorbed and converted in the overlying junction materials. Their contact resistances must be low enough to prevent significant I to the 2d power R loss at the designed current density levels. They should also exhibit adequate thermal conductivity to prevent device overheating when subjected to the designed illumination level. Recent encouraging results for the development of such contacts are presented.

Zehr, S. W.↗
NASA NTRS1988

Extremely low resistance nonalloyed ohmic contacts on GaAs using InAs/InGaAs and InAs/GaAs strained-layer superlattices

Employing a structure consisting of n(+)-InAs/InGaAs and InAs/GaAs strained-layer superlattices (SLSs) grown by molecular beam epitaxy on GaAs films, nonalloyed contact resistances less than 8.5 x 10 to the -8th ohm sq cm have been obtained. Self-consistent simulations show that these extremely small nonalloyed contact resistances are due to the suppression of the depletion depth in the GaAs channel and tunneling through the SLS layer. Similar structures on InGaAs channels have led to nonalloyed specific contact resistances of about 1.5 x 10 to the -8th ohm sq cm. These results represent the smallest figures reported for these important material systems.

Peng, C. K.↗
NASA NTRS2001

Thermally Stable Ohmic Contacts on Silicon Carbide Developed for High- Temperature Sensors and Electronics

The NASA aerospace program, in particular, requires breakthrough instrumentation inside the combustion chambers of engines for the purpose of, among other things, improving computational fluid dynamics code validation and active engine behavioral control (combustion, flow, stall, and noise). This environment can be as high as 600 degrees Celsius, which is beyond the capability of silicon and gallium arsenide devices. Silicon-carbide- (SiC-) based devices appear to be the most technologically mature among wide-bandgap semiconductors with the proven capability to function at temperatures above 500 degrees Celsius. However, the contact metalization of SiC degrades severely beyond this temperature because of factors such as the interdiffusion between layers, oxidation of the contact, and compositional and microstructural changes at the metal/semiconductor interface. These mechanisms have been proven to be device killers. Very costly and weight-adding packaging schemes that include vacuum sealing are sometimes adopted as a solution.

Okojie, Robert S.↗