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Magnetoresistance and Cyclotron Mass in Extremely-Coupled Double Quantum Wells Under in-Plane Magnetic Fields

Description: The authors experimentally investigate the transport properties of an extremely-coupled AlGaAs/GaAs double quantum well, subject to in-plane magnetic fields (B{sub {parallel}}). The coupling of the double quantum well is sufficiently strong that the symmetric-antisymmetric energy gap ({Delta}{sub SAS}) is larger than the Fermi energy (E{sub F}). Thus for all B{sub {parallel}} only the lower energy branch of the dispersion curve is occupied. In contrast to systems with weaker coupling such that … more
Date: December 1, 1997
Creator: Blount, M. A.; Simmons, J. A.; Lyo, S. K.; Harff, N. E. & Weckwerth, M. V.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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InGaAs monolithic interconnected modules (MIM)

Description: A monolithic interconnected module (MIM) structure has been developed for thermophotovoltaic (TPV) applications. The MIM device consists of many individual InGaAs cells series-connected on a single semi-insulating (S.I.) InP substrate. An infrared (IR) back surface reflector (BSR), placed on the rear surface of the substrate, returns the unused portion of the TPV radiator output spectrum back to the emitter for recycling, thereby providing for high system efficiencies. Also, the use of a BSR ob… more
Date: December 31, 1997
Creator: Fatemi, Navid S.; Jenkins, Philip P.; Weizer, Victor G.; Hoffman, Richard W., Jr.; Wilt, David M.; Scheiman, David et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Materials and process development for the monolithic interconnected module (MIM) InGaAs/InP TPV cells

Description: Four major components of a thermophotovoltaic (TPV) energy conversion system are a heat source, a graybody or a selective emitter, spectrum shaping elements such as filters, and photovoltaic (PV) cells. One approach to achieving a high voltage/low current configuration is to fabricate a device, where small area PV cells are monolithically series connected. The authors have termed this device a monolithic interconnected module (MIM). A MIM device has other advantages over conventional one-juncti… more
Date: June 1, 1997
Creator: Fatemi, Navid S.; Jenkins, Phillip P.; Hoffman, Richard W., Jr.; Weizer, Victor G.; Wilt, David M.; Murray, Christopher S. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Investigations in Gallium Removal

Description: Gallium present in weapons plutonium must be removed before it can be used for the production of mixed-oxide (MOX) nuclear reactor fuel. The main goal of the preliminary studies conducted at Texas A and M University was to assist in the development of a thermal process to remove gallium from a gallium oxide/plutonium oxide matrix. This effort is being conducted in close consultation with the Los Alamos National Laboratory (LANL) personnel involved in the development of this process for the US D… more
Date: November 1, 1997
Creator: Philip, C. V.; Pitt, W. W. & Beard, C. A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Electrical and optical performance characteristics of 0.74eV p/n InGaAs monolithic interconnected modules

Description: There has been a traditional trade-off in thermophotovoltaic (TPV) energy conversion development between system efficiency and power density. This trade-off originates from the use of front surface spectral controls such as selective emitters and various types of filters. A monolithic interconnected module (MIM) structure has been developed which allows for both high power densities and high system efficiencies. The MIM device consists of many individual indium gallium arsenide (InGaAs) cells s… more
Date: June 1, 1997
Creator: Wilt, David M.; Weizer, Victor G.; Fatemi, Navid S.; Jenkins, Philip P.; Hoffman, Richard W., Jr.; Jain, Raj K. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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CIS photovoltaic technology. Annual technical report, January 12, 1996--January 11, 1997

Description: Thin film photovoltaic modules based on Cu(In,Ga)Se{sub 2} have been shown to possess attributes that should enable them to compete effectively with silicon-based modules, and that should ultimately allow realization of a much lower $/Wp cost figure. These attributes are stability, high efficiency, and low materials cost. Energy Photovoltaics has explored novel CIGS formation recipes that can be implemented on a unique pilot line constructed to coat substrates 4300 cm{sup 2} in area. One partic… more
Date: June 1, 1997
Creator: Delahoy, A.E.; Britt, J.S. & Kiss, Z.J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Transport in arrays of submicron Josephson junctions over a ground plane

Description: One-dimensional (1D) and two-dimensional (2D) arrays of Al islands linked by submicron Al/Al{sub x}O{sub y}/Al tunnel junctions were fabricated on an insulating layer grown on a ground plane. The arrays were cooled to temperatures as low as 20 mK where the Josephson coupling energy E{sub J} of each junction and the charging energy E{sub C} of each island were much greater than the thermal energy k{sub B}T. The capacitance C{sub g} between each island and the ground plane was much greater than t… more
Date: December 1, 1997
Creator: Ho, Teressa Rae
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries Government Documents Department
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Interfaces and defects in opto-electronic semiconductor films studies by atomic resolution stem

Description: The growth of thin films on dissimilar substrates is of great technological importance for modern optoelectronic devices. However, device applications are currently limited by lattice mismatches between the film and substrate that invariably lead to defects detrimental to device performance. It is therefore of key importance that the mechanisms leading to the formation of these defects are understood on the fundamental atomic level. Correlated atomic resolution Z-contrast imaging and EELS in th… more
Date: April 1, 1997
Creator: Xin, Y.; Wallis, D. J. & Browning, N. D.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Ion exchange separation of plutonium and gallium (1) resource and inventory requirements, (2) waste, emissions, and effluent, and (3) facility size

Description: The following report summarizes an effort intended to estimate within an order-of-magnitude the (1) resource and inventory requirements, (2) waste, emissions, and effluent amounts, and (3) facility size, for ion exchange (IX) separation of plutonium and gallium. This analysis is based upon processing 3.5 MT-Pu/yr. The technical basis for this summary is detailed in a separate document, {open_quotes}Preconceptual Design for Separation of Plutonium and Gallium by Ion Exchange{close_quotes}. The m… more
Date: September 30, 1997
Creator: DeMuth, S.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Detection of lateral composition modulation by magnetoexciton spectroscopy

Description: An experimental signature for detecting spontaneous lateral composition modulation in a (InAs){sub n}/(GaAs){sub m} short period superlattice on an InP substrate based on magnetoexciton spectroscopy described. The authors find by aligning the magnetic field in three crystallographic directions, one parallel to and the other two perpendicular to the composition modulation direction, that the magnetoexciton shifts are anisotropic and are a good indicator for the presence of composition modulation. more
Date: July 10, 1997
Creator: Jones, E. D.; Millunchick, J. M.; Follstaedt, D.; Lee, S.; Reno, J.; Twesten, R. D. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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ICP dry etching of III-V nitrides

Description: Inductively coupled plasma etching of GaN, AlN, InN, InGaN and InAlN was investigated in CH{sub 4}/H{sub 2}/Ar plasmas as a function of dc bias, and ICP power. The etch rates were generally quite low, as is common for III-nitrides in CH{sub 4} based chemistries. The etch rates increased with increasing dc bias. At low rf power (150 W), the etch rates increased with increasing ICP power, while at 350 W rf power, a peak was found between 500 and 750 W ICP power. The etched surfaces were found to … more
Date: October 1, 1997
Creator: Vartuli, C. B.; Lee, J. W. & MacKenzie, J. D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Lattice-engineered MBE growth of high-indium mole fraction InGaAs for low cost MMICs and (1.3--1.55 {micro}m) OEICs

Description: Using molecular beam epitaxy (MBE) and lattice engineering techniques, the feasibility of combining photonic devices applicable to the 1.3 to 1.55 {micro}m wavelength range and monolithic microwave (or mm-wave) integrated circuits (MMICs) on GaAs is demonstrated. A key factor in the MBE growth is incorporation of an InGaAs active layer having an indium arsenide mole fraction of 0.35 or greater and its lattice compatibility with the underlying semi-insulating GaAs substrate. The InGaAs layer use… more
Date: November 1, 1997
Creator: Childs, T. T.; Sokolov, V. & Sullivan, C. T.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Atomic hydrogen cleaning of semiconductor photocathodes

Description: Negative Electron Affinity (NEA) semiconductor photocathodes are widely used for the production of polarized electron beams, and are also useful for the production of high brightness electron beams which can be modulated at very high frequencies. Preparation of an atomically clean semiconductor surface is an essential step in the fabrication of a NEA photocathode. This cleaning step is difficult for certain semiconductors, such as the very thin materials which produce the highest beam polarizat… more
Date: June 1, 1997
Creator: Sinclair, C. K.; Poelker, B. M. & Price, J. S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Modeling of InGaSb thermophotovoltaic cells and materials

Description: A closed form computer program has been developed for the simulation and optimization of In{sub x}Ga{sub 1{minus}x}Sb thermophotovoltaic cells operating at room temperature. The program includes material parameter models of the energy bandgap, optical absorption constant, electron and hole mobility, intrinsic carrier concentration and index of refraction for any composition of GaInSb alloys.
Date: May 1, 1997
Creator: Zierak, M.; Borrego, J. M.; Bhat, I.; Gutmann, R. J. & Charache, G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Detection of lateral composition modulation in a (InAs){sub n}/(GaAs){sub n} short period superlattice on InP by magnetoexciton spectroscopy

Description: An experimental signature for detecting spontaneous lateral composition modulation in a (InAs){sub n}/(GaAs){sub n} short period superlattice on a InP substrate based on magnetoexciton spectroscopy is presented. The authors find by aligning the magnetic field in three crystallographic directions, one parallel to and the other two perpendicular to the composition modulation direction, that the magnetoexciton shifts are anisotropic and are a good indicator for the presence of composition modulati… more
Date: March 1, 1997
Creator: Jones, E. D.; Mirecki-Millunchick, J.; Follstaedt, D.; Hafich, M.; Lee, S.; Reno, J. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Electrical and optical properties of degenerately doped N-type In{sub x}Ga{sub 1{minus}x}As

Description: Degenerately-doped (> 10{sup 19} cm{sup {minus}3}) n-type In{sub x}Ga{sub 1{minus}x}As (x > 0.53) possesses a number of intriguing electrical and optical properties relevant to electro-optic devices and thermophotovoltaic devices in particular. Due to the low electron effective mass of this material and the demonstrated ability to incorporate n-type dopants into the mid-10{sup 19} cm{sup {minus}3} range, both the Moss-Burnstein bandgap shift and plasma reflection characteristics are particularl… more
Date: May 1, 1997
Creator: Charache, G. W.; DePoy, D. M. & Egley, J. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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A high-DC-voltage GaAs photoemission gun: Transverse emittance and momentum spread measurements

Description: We have built a high-DC-voltage photoemission gun and a diagnostic beamline permitting us to measure rms transverse emittance ({epsilon}{sub x}) and rms momentum spread ({delta}) of short-duration electron pulses produced by illuminating the cathode with light from a mode-locked, frequency-doubled Nd:YLF laser. The electron gun is a GaAs photocathode source designed to operate at 500kV. We have measured {epsilon}{sub x} and {delta} for conditions ranging from emittance-dominated to space-charge… more
Date: June 1, 1997
Creator: Engwall, D.; Bohn, C. & Cardman, L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Chlorine-based plasma etching of GaN

Description: The wide band gap group-III nitride materials continue to generate interest in the semiconductor community with the fabrication of green, blue, and ultraviolet light emitting diodes (LEDs), blue lasers, and high temperature transistors. Realization of more advanced devices requires pattern transfer processes which are well controlled, smooth, highly anisotropic and have etch rates exceeding 0.5 {micro}m/min. The utilization of high-density chlorine-based plasmas including electron cyclotron res… more
Date: February 1, 1997
Creator: Shul, R. J.; Briggs, R. D.; Pearton, S. J.; Vartuli, C. B.; Abernathy, C. R.; Lee, J. W. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Compact environmental spectroscopy using advanced semiconductor light-emitting diodes and lasers

Description: This report summarizes research completed under a Laboratory Directed Research and Development program funded for part of FY94, FY95 and FY96. The main goals were (1) to develop novel, compound-semiconductor based optical sources to enable field-based detection of environmentally important chemical species using miniaturized, low-power, rugged, moderate cost spectroscopic equipment, and (2) to demonstrate the utility of near-infrared spectroscopy to quantitatively measure contaminants. Potentia… more
Date: April 1, 1997
Creator: Fritz, I.J.; Klem, J.F. & Hafich, M.J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

TPV efficiency measurements and predictions for a closed cavity geometry

Description: A thermophotovoltaic (TPV) efficiency measurement, within a closed cavity, is an integrated test which incorporates four fundamental parameters of TPV direct energy conversion. These are: (1) the TPV devices, (2) spectral control, (3) a radiation/photon source, and (4) closed cavity geometry effects. The overall efficiency of the TPV device is controlled by the TP cell performance, the spectral control characteristics, the radiator temperature and the geometric arrangement. Controlled efficienc… more
Date: May 1, 1997
Creator: Gethers, C. K.; Ballinger, C. T.; Postlethwait, M. A.; DePoy, D. M. & Baldasaro, P. F.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

MOX capsule post-irradiation examination. Volume 2: Test plan for 30-GWd/MT burnup fuel

Description: This test plan is a Level-2 document as defined in the Fissile Materials Disposition Program Light-Water Reactor Mixed-Oxide Fuel Irradiation Test Project Plan. The planned post-irradiation examination (PIE) work to be performed on the mixed uranium and plutonium oxide fuel capsules that have received burnups of approximately 30 GWd/MT is described. The major emphasis of this PIE task will be material interactions, particularly indications of gallium transport and interactions. This PIE will in… more
Date: December 1, 1997
Creator: Morris, R.N.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Theoretical investigation of extended defects in group-III nitrides

Description: The authors have investigated two types of extended defects commonly found in AlN, GaN and InN films using density-functional techniques. First, basal-plane stacking faults have been studied for all three compounds. Stacking-fault energies were found to be largest in AlN and smallest in GaN consistent with density-functional results for their wurtzite/zinc-blende energy differences. In addition, the 4H and 6H structures were found to have lower energies than zinc blende for all three compounds.… more
Date: December 1, 1997
Creator: Wright, A. F.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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X-ray standing wave investigations of Group III and V metal adsorption on Si(001)

Description: Investigations of atomic bonding, surface reconstruction, surface dynamics, and growth kinetics of group III and V metals on Si(001) are important for understanding the initial growth stage of III-V semiconductors on Si(001). Such studies can also provide valuable information for other important issues such as surfactant-mediated epitaxy, surface passivation and delta-doping layers. X-ray standing waves generated by dynamical Bragg diffraction were used as an element-specific structural probe f… more
Date: May 1, 1997
Creator: Qian, Y.; Bedzyk, M. J. & Lyman, P. F.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Nonlinear optical properties of atomic vapor and semiconductors

Description: This thesis contains the study of highly forbidden resonant second harmonic generation (SHG) in atomic potassium vapor using tunable picosecond pulses. Various output characteristics of vapor SHG have been investigated including the input intensity dependence, potassium vapor density dependence, buffer gas pressure dependence, and spatial profile. Recently, the discovery of new nonlinear optical crystals such as barium borate ({beta}-BaB{sub 2}O{sub 4}, BBO) and lithium borate (LiB{sub 3}O{sub … more
Date: June 1, 1997
Creator: Kim, D.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries Government Documents Department
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