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DESIGN AND ANALYSIS OF AN INTEGRATED PULSE MODULATED S-BAND POWER AMPLIFIER IN GALLIUM NITRIDE PROCESS

Description: The design of power amplifiers in any semi-conductor process is not a trivia exercise and it is often encountered that the simulated solution is qualitatively different than the results obtained. Phenomena such as oscillation occurring either in-band or out of band and sometimes at subharmonic intervals, continuous spectrum noticed in some frequency bands, often referred to as chaos, and jumps and hysteresis effects can all be encountered and render a design useless. All of these problems might… more
Date: April 4, 2012
Creator: SEDLOCK, STEVE
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries Government Documents Department
open access

High sensitivity resonance frequency measurements of individualmicro-cantilevers using fiber optical interferometry

Description: We describe a setup for the resonance frequency measurement of individual microcantilevers. The setup displays both high spatial selectivity and sensitivity to specimen vibrations by utilizing a tapered uncoated fiber tip. The high sensitivity to specimen vibrations is achieved by the combination of optical Fabry-Perot interferometry and narrow band RF detection. Wave fronts reflected on the specimen and on the fiber tip end face interfere, thus no reference plane on the specimen is needed, as … more
Date: March 4, 2009
Creator: Duden, Thomas & Radmilovic, Velimir
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Enhancing RHIC luminosity capabilities with in-situ beam piple coating

Description: Electron clouds have been observed in many accelerators, including the Relativistic Heavy Ion Collider (RHIC) at the Brookhaven National Laboratory (BNL). They can limit the machine performance through pressure degradation, beam instabilities or incoherent emittance growth. The formation of electron clouds can be suppressed with beam pipe surfaces that have low secondary electron yield. At the same time, high wall resistivity in accelerators can result in levels of ohmic heating unacceptably hi… more
Date: May 4, 2009
Creator: Herschcovitch,A.; Blaskiewicz, M.; Fischer, W. & Poole, H. J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Laser Gain and Threshold Properties in Compressive-Strained and Lattice-Matched GaInNAs/GaAs Quantum Wells

Description: The optical gain spectra for compressive-strained and lattice-matched GaInNAs/GaAs quantum wells are computed using a microscopic laser theory. From these spectra, the peak gain and carrier radiative decay rate as functions of carrier density are determined. These dependences allow the study of lasing threshold current density for different GAInNAs/GaAs laser structures.
Date: August 4, 1999
Creator: Chow, W. W.; Jones, E. D.; Modine, N. A.; Allerman, A. A. & Kurtz, S. R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Optical calibration of pressure sensors for high pressures and temperatures

Description: We present the results of Raman scattering measurements of diamond ({sup 12}C) and of cubic boron nitride (cBN), and fluorescence measurements of ruby, Sm:YAG, and SrB{sub 4}O{sub 7}:Sm{sup 2+} in the diamond anvil cell (DAC) at high pressures and temperatures. These measurements were accompanied by synchrotron x-ray diffraction measurements on gold. We have extended the room-temperature calibration of Sm:YAG in a quasihydrostatic regime up to 100 GPa. The ruby scale is shown to systematically … more
Date: October 4, 2004
Creator: Goncharov, A F; Gregoryanz, E; Zaug, J M & Crowhurst, J C
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Wet Chemical Etching Survey of III-Nitrides

Description: Wet chemical etching of GaN, InN, AlN, InAlN and InGaN was investigated in various acid and base solutions at temperatures up to 75 C. Only KOH-based solutions were found to etch AlN and InAlN. No etchants were found for the other nitrides, emphasizing their extreme lack of chemical reactivity. The native oxide on most of the nitrides could be removed in potassium tetraborate at 75 C, or HCl/H{sub 2}O at 25 C.
Date: February 4, 1999
Creator: Abernathy, C. R.; Cho, H.; Hays, D. C.; MacKenzie, J. D.; Pearton, S.J.; Ren, F. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

High-temperature compressive deformation of Si{sub 3}N{sub 4}/BN fibrous monoliths.

Description: Fibrous monolithic Si{sub 3}N{sub 4}/BN ({approx}85 vol.% Si{sub 3}N{sub 4}/15 vol.% BN) and monolithic Si{sub 3}N{sub 4} ceramics were compressed at a nearly constant strain rate ({var_epsilon}) at 1200-1400 C in N{sub 2}. The {var_epsilon} range was {approx}1 x 10{sup {minus}6} to 5 x 10{sup {minus}6} s{sup {minus}1}; the stress ({sigma}) range was 37-202 MPa. The Si{sub 3}N{sub 4} and the unidirectional fibrous monoliths that were oriented with the long axis of the Si{sub 3}N{sub 4} cells pa… more
Date: February 4, 1999
Creator: Routbort, J. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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DC characteristics of OMVPE-grown N-p-n InGaP/InGaAsN DHBTs

Description: The authors demonstrate, for the first time, a functional N-p-n heterojunction bipolar transistor using a novel material, InGaAsN, with a bandgap energy of 1.2eV as the p-type base layer. A 300{angstrom}-thick In{sub x}Ga{sub 1-x}As graded layer was introduced to reduce the conduction band offset at the p-type InGaAsN base and n-type GaAs collector junction. For an emitter size of 500 {mu}m{sup 2}, a peak current gain of 5.3 has been achieved.
Date: January 4, 2000
Creator: Li, N. Y.; Chang, P. C.; Baca, A. G.; Xie, X. M.; Sharps, P. R. & Hou, H. Q.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Properties of low residual stress silicon oxynitrides used as a sacrificial layer

Description: Low residual stress silicon oxynitride thin films are investigated for use as a replacement for silicon dioxide (SiO{sub 2}) as sacrificial layer in surface micromachined microelectrical-mechanical systems (MEMS). It is observed that the level of residual stress in oxynitrides is a function of the nitrogen content in the film. MEMS film stacks are prepared using both SiO{sub 2} and oxynitride sacrificial layers. Wafer bow measurements indicate that wafers processed with oxynitride release layer… more
Date: January 4, 2000
Creator: Habermehl, S. D.; Glenzinski, A. K.; Halliburton, W. M. & Sniegowski, J. J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

AlGaAs/InGaAsN/GaAs PnP double heterojunction bipolar transistor

Description: The authors demonstrated a functional PnP double heterojunction bipolar transistor (DHBT) using AlGaAs, InGaAsN, and GaAs. The band alignment between InGaAsN and GaAs has a large {triangle}E{sub c} and negligible {triangle}E{sub v}, this unique characteristic is very suitable for PnP DHBT applications. The metalorganic vapor phase epitaxy (MOCVD) grown Al{sub 0.3}Ga{sub 0.7}As/In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01}/GaAs PnP DHBT is lattice matched to GaAs and has a peak current gain of… more
Date: January 4, 2000
Creator: Chang, P. C.; Baca, A. G.; Li, N. Y.; Sharps, P. R.; Hou, H. Q.; Laroche, J. R. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

NOVEL SUPPORTED BIMETALLIC CARBIDE CATALYSTS FOR COPROCESSING OF COAL WITH WASTE MATERIALS

Description: A new family of bimetallic oxynitride compounds, M<SUB>I</SUB>-M<SUB>II</SUB>-O-N (M<SUB>I</SUB>, M<SUB>II</SUB> = Mo, W, V, Nb, Cr, Mn and Co), has been synthesized by nitriding bimetallic oxide precursors with ammonia gas via a temperature programmed reaction. The oxide precursors are prepared by conventional solid state reaction between two appropriate monometallic oxides. The synthesis involves passing NH<SUB>3</SUB> gas over the oxide precursors at a flow rate of 6.80x10<SUP>2</SUP> {micro… more
Date: November 4, 1998
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Stress and Defect Control in GaN Using Low Temperature Interlayers

Description: In organometallic vapor phase epitaxial growth of Gail on sapphire, the role of the low- temperature-deposited interlayers inserted between high-temperature-grown GaN layers was investigated by in situ stress measurement, X-ray diffraction, and transmission electron microscopy. Insertion of a series of low temperature GaN interlayers reduces the density of threading dislocations while simultaneously increasing the tensile stress during growth, ultimately resulting in cracking of the GaN film. L… more
Date: December 4, 1998
Creator: Akasaki, I.; Amano, H.; Chason, E.; Figiel, J.; Floro, J.A.; Han, J. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Testing and Lubrication for Single Race Bearings

Description: Three ES and H-compatible lubricants (Environment, Safety and Health) for single race bearing applications and one hybrid-material single race bearings were evaluated and compared against single race bearings with trichlorotrifluoroethane (Freon) deposition of low molecular weight polytetrafluoroethylene (PTFE) bearing lubricant extracted from Vydax{trademark}. Vydax is a product manufactured by DuPont consisting of various molecular weights of PTFE suspended in trichlorotrifluoroethane (Freon)… more
Date: March 4, 1998
Creator: Steinhoff, R.G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Neutron scattering studies of industry-relevant materials : connecting microscopic behavior to applied properties.

Description: Certain systems of oxides, nitrides and carbides have been recognized as the basic components of advanced materials for applications as engineering and electronic ceramics, catalysts, sensors, etc. under extreme environments. An understanding of the basic atomic and electronic properties of these systems will benefit enormously the industrial development, of new materials featuring tailored properties. We present an overview of neutron-scattering studies of the crystal phases, microstructure, p… more
Date: January 4, 1999
Creator: Loong, C.-K.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Deep Level Defect Studies in MOCVD-Grown In(x)Ga(1-x)As(1-y)N(y) Films Lattice-Matched to GaAs

Description: Deep level defects in MOCVD-grown, unintentionally doped p-type InGaAsN films lattice matched to GaAs were investigated using deep level transient spectroscopy (DLTS) measurements. As-grown p-InGaAsN showed broad DLTS spectra suggesting that there exists a broad distribution of defect states within the band-gap. Moreover, the trap densities exceeded 10{sup 15} cm{sup {minus}3}. Cross sectional transmission electron microscopy (TEM) measurements showed no evidence for threading dislocations with… more
Date: March 4, 1999
Creator: Allerman, A. A.; Boeckl, J. J.; Jones, E. D.; Kaplar, R. J.; Kurtz, S. R.; Kwon, D. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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