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Neutron and x-ray scattering studies of (FeF{sub 2}){sub m}(CoF{sub 2}){sub n} multilayers

Description: We have performed elastic neutron scattering measurements of the staggered magnetization in (FeF{sub 2}){sub m}(CoF{sub 2}){sub n} superlattices. Thermal expansion measurements, which are proportional to the magnetic contribution to the specific heat, wwre also carried out using high resolution x-ray diffraction. One of the two measured samples has thickness of m = n = 4.5 and the other m = 26 and n = 28 monolayers, as determined from high angle x-ray {theta} - 2{theta} scans. In the m = n = 4.5 sample, only one transition is observed T{sub N} = 62.9K. Analysis of the neutron data, including the rounding effects, indicates an effective {beta} {approx} 0.42. This does not compare well with the 3D Ising exponent {beta} = 0.325. The X-ray data also shows the existence of only one specific heat anomaly at T = 62.8 K. For the m = 26, n = 28 sample, dips in the staggered magnetization, and peaks in the thermal expansion were observed at T {approx} 40 K and 74 K. The higher temperature anomaly, associated primarily with the FeF{sub 2} layers, is sharper than the lower one, which is presumably rounded by the staggered ordering field improsed by the long range order in the FeF{sub 2} regions on the CoF{sub 2} regions.
Date: June 1, 1993
Creator: Lederman, D.; Belanger, D. P.; Wang, J.; Han, S. J.; Paduani, C. P.; Ramos, C. A. et al.
Partner: UNT Libraries Government Documents Department

Polarized photomodulated reflectivity and photoluminescence studies of ordered InGaP{sub 2} under pressure

Description: Spontaneous ordering of ternary alloys grown on misoriented substrates has been of recent interest. Ordering induced band gap reduction, and valence band splittings exhibiting novel polarization properties have been investigated by theory and experiment. This paper discusses polarized photomodulated reflectivity (PR) and photoluminescence (PL) studies of MOCVD grown InGaP{sub 2} epilayers lattice-matched to a GaAs substrate. These structures were grown on a (001) face with a niisorientation of two degrees along <110>. The high degree of ordering has enabled us to accurately measure the crystal field splitting and additional structure not reported in the PR spectra. For the electric field E parallel to [110] two features in the PR spectra are seen; for E {parallel}[110], however, additional features are observed. Comparison with spectra of disordered samples of the same alloy composition has enabled a determination of the band gap reduction due to ordering. Linewidths of the PR peaks are approximately 5--10 meV which has enabled us to study them in detail as a function of hydrostatic pressure at cryogenic temperatures. The pressure dependence is slightly sublinear with the first order term of 8--9 meV/kbar for pressures well below the l-X crossover. Also observed is the indirect level crossing which occurs under pressure at about 40-kbar. A comparison of PR lineshapes at 1-bar is also presented at several commonly used experimental temperatures. Data indicate a substantial change in PR lineshapes, showing that interpretation of reflectivity data for these samples must be handled carefully.
Date: August 1, 1994
Creator: Thomas, R. J.; Chandrasekhar, H. R.; Chandrasekhar, M.; Jones, E. D. & Schneider, R. P. Jr.
Partner: UNT Libraries Government Documents Department

Interfacial structure of lattice mismatched bcc(110)/bcc(110) transition metal superlattices

Description: We present structural characterizations of a series of sputtered Fe/Nb and V/Nb superlattices by high-angle x-ray diffraction. Diffraction scans were performed with the scattering vector at various angles ({Chi}) with respect to the layers. {Chi}=0{degrees} diffraction spectra (normal to the layers) were fitted to a general structural model to determine the (110) lattice strains, interfacial disorder and interdiffusion. {Chi}>0{degrees} spectra probe the lattice strain of the individual layers and the in-plane interfacial coherence. Both systems form incoherent interfaces above a critical modulation wavelength ({Lambda}{sub C}). At {Lambda}{sub C}, the Fe/Nb system undergoes a crystalline-to-amorphous transition while the V/Nb forms in-plane coherent interfaces.
Date: March 1, 1993
Creator: Fullerton, E. E.; Sowers, C. H.; Bader, S. D.; Mini, S.; Bommannavar, A. S. & Ehrlich, S. N.
Partner: UNT Libraries Government Documents Department

Surfaces and interfaces of ceramics and metals. [Final] report, July 1988--November 1992

Description: Structures of surfaces of several ceramic oxides were studied by use of reflection electron microscopy (REM) and associated techniques. High-temperature annealing in air or oxygen gives smooth, flat crystal faces in most cases, including the (111) MgO surface, previously thought to be facetted. Stability of the (111) MgO surface is shown to be due to a surface superlattice reconstruction. Surface superlattices, stable in air, have also been shown to exist on sapphire and rutile crystal faces. The segregation of Ca to the surface of MgO has been studied using reflection electron energy loss techniques. Initial studies of Cu-Au alloy crystal surfaces, necessarily carried out in ultra-high vacuum, have been made using RHEED and Auger electron spectroscopy. Clean alloy surfaces show surface reconstructions associated with the segregation of Au atoms at the surface. High-temperature annealing results in the segregation of sulfur to the surface and the formation of a variety of surface superlattice structures. Structures of solid-solid interfaces have been studied using a wide variety of electron-optical techniques including nanodiffraction and electron holography. In particular the interfaces in semiconductor multiple quantum well structures and also multilayer structures of Si and Co have been studied.
Date: December 31, 1992
Partner: UNT Libraries Government Documents Department

Phase separation and ordering process in Al-Li alloys studied by small-angle neutron scattering and neutron diffraction

Description: To study phase separation kinetics of Al-9.5at.%Li polycrystalline alloys in which precipitates have ordered Al{sub 3}Li ({delta}{prime}) structure, profile analysis of small-angle neutron scattering and superlattice reflections (100) and (110) were done. A small-angle scattering instrument and a triple-axis spectrometer in elastic mode were used in the measurements. Strong texture was observed in the reflections. Therefore, measurements were done using the crystal orientation where the intensity of the reflection was at the maximum. Profiles of small-angle scattering and superlattice reflections were almost identical at higher momentum transfer side. At lower momentum transfer side, small-angle scattering showed interference effects, but superlattice reflection did not show any sign of interference. Integrated intensities of superlattice reflections were obtained and compared with small-angle scattering intensity. The order parameter was not saturated in the {delta}{prime} precipitates at the early stage of the phase separation process.
Date: July 1, 1993
Creator: Furusaka, M.; Fujikawa, S. I. & Tranquada, J. M.
Partner: UNT Libraries Government Documents Department

Energy gap structure of layered superconductors

Description: We report the energy gap structure and density-of-states (DOS) of a model layered superconductor with one superconducting layer and one normal layer in a unit cell along the c-axis. In the physically interesting parameter range where the interlayer hopping strengths of the quasiparticles are comparable to the critical temperature, the peaks in the DOS curve do not correspond to the order parameter (OP) of the superconducting layer, but depend on the OP and the band dispersion in the c-direction in a complex manner. In contrast to a BCS superconductor, the DOS of layered systems have logarithmic singularities. Our simulated tunneling characteristics bear close resemblance to experimental results.
Date: December 1, 1993
Creator: Liu, S. H. & Klemm, R. A.
Partner: UNT Libraries Government Documents Department

Neutron-induced collision cascade mixing in Nb/V superlattices

Description: High-angle X-ray diffraction was used to determine cascade mixing efficiencies, Dt/dpa, in Nb/V superlattices irradiated to small doses ({le}0.26 dpa). Samples were neutron irradiated in the core of the High Flux Beam Reactor at Brookhaven National Laboratory and ion irradiated with 1.5 MeV Ne. No significant differences were observed in cascade mixing efficiencies between the two types of irradiation. Values of Dt/dpa were observed to vary with the modulation wavelength of the superlattice, with thicker wavelength samples yielding values approaching that determined from ion mixing thick Nb/V bilayers (Dt/dpa{approx}110 {Angstrom}{sup 2}/dpa). The decrease in mixing efficiency observed at lower wavelengths may be related to an observed structural transition in which the interfaces of the superlattice become coherent.
Date: July 1, 1993
Creator: Alexander, D. E.; Fullerton, E. E.; Baldo, P. M.; Sowers, C. H. & Rehn, L. E.
Partner: UNT Libraries Government Documents Department

Phenomenological explanation of elastic anomalies in superlattices

Description: The experimental fact that measured elastic and structural properties of superlattices are strongly correlated can be understood on the basis of a simple model based on the packing of hard spheres. The model is consistent with features of many models that have been proposed to explain the supermodulus effect; but contrary to previous explanations, it allows predictions for a given pair of constitutents to be made. For an arbitrary pair of elements, it predicts the existence or non-existence of an elastic anomaly, and a rough estimate of its magnitude.
Date: June 1, 1993
Creator: Grimsditch, M.; Fullerton, E. E. & Schuller, I. K.
Partner: UNT Libraries Government Documents Department

Superhardness Effect in Au/Ni multilayers

Description: The presence of an enhanced hardness, that is a `Superhardness Effect, is found as a behavior parallel to the Supermodulus Effect in Au/Ni multilayer structures. The submicron thick Au/Ni coatings are prepared by magnetron sputter deposition. A microindenter is used to measure load as a function of indentation depth. An increase in hardness is measured as the Au/Ni layer pair spacing decreases. A local maximum in hardness occurs for samples with layer pairs consisting of 4-6 atomic planes of each metal component.
Date: March 1, 1993
Creator: Jankowski, A. F.
Partner: UNT Libraries Government Documents Department

Microstructures of InAs{sub 1{minus}x}Sb{sub x} (x = 0.07--0.14) alloys and strained-layer superlattices

Description: Growth of InAs{sub l{minus}x},Sb{sub x} alloys by MOCVD at 475C results in CuPt ordering even at Sb concentrations as low as x = 0.07--0.14. The two {l_brace}111{r_brace}{sub B} variants are present, but each exists separately in 1--2 {mu}m regions. However, the ordering is incomplete: it occurs in platelet domains lying on {l_brace}111{r_brace} habit planes within a disordered matrix, and is not continuous at the atomic scale within the domains. This ordering apparently explains the reduction in infrared emission energies relative to the bandgaps of bulk alloys. Similar ordering is found in an InAs{sub 0.91}Sb{sub 0.09}/In{sub 0.87}Ga{sub 0.13}AS strained-layer superlattice with lower-than, expected emission energy. High-resolution images indicate that the SLS has planar, sharply defined interfaces. Infrared LEDs have been made from such superlattices.
Date: August 1, 1994
Creator: Follstaedt, D. M.; Biefeld, R. M. & Kurtz, S. R., Baucom, K. C.
Partner: UNT Libraries Government Documents Department

Photoluminescence determination of valence-band symmetry and Auger-1 threshold energy in biaxially compressed InAsSb layers

Description: InAsSb/InGaAs strained-layer superlattices (SLSs) and InAsSb quantum wells, both with biaxially compressed InAsSb layers, were characterized using magneto-photoluminescence and compared with unstained InAsSb and InAs alloys. In heterostructures with biaxially compressed InAsSb, the holes exhibited a decrease in effective mass, approaching that of the electrons. Correcting the data for the magneto-exciton binding energy, we obtain electron-hole reduced mass values in the range, {mu}=0.010--0.015, for the InAsSb heterostructures, whereas {mu}=0.026 and {mu}-0.023 for unstrained InAsSb and InAs alloys respectively. In the 2-dimensional limit, a large increase in the Auger-1 threshold energy accompanies this strain-induced change in valence-band symmetry. Correspondingly, the activation energy for nonradiative recombination in the SLSs displayed a marked increase compared with that of the unstrained alloys.
Date: August 1, 1994
Creator: Kurtz, S. R.; Biefeld, R. M. & Dawson, L. R.
Partner: UNT Libraries Government Documents Department

Optimization of InAsSb/InGaAs strained-layer superlattice growth by metal-organic chemical vapor deposition for use in infrared emitters

Description: We have prepared InAsSb/InGaAs strained-layer superlattices (SLSs) by metal-organic chemical vapor deposition using a variety of growth conditions. Presence of an InGaAsSb interface layer was indicated by x-ray diffraction. This interface effect was minimized by optimizing the purge times, reactant flows, and growth conditions. The optimized growth conditions involved the use of low pressure, short purge times between the growth of the layers, and no reactant flow during the purges. Electron diffraction indicates that CuPt-type compositional ordering occurs in InAs{sub 1{minus}x}Sb{sub x} alloys and SLSs which explains an observed bandgap reduction from previously accepted alloy values.
Date: August 1, 1994
Creator: Biefeld, R. M.; Baucom, K. C.; Follstaedt, D. M. & Kurtz, S. R.
Partner: UNT Libraries Government Documents Department

The growth of InAs{sub 1-x}Sb{sub x}/InAs strained-layer superlattices by metal-organic chemical vapor deposition

Description: InAs{sub 1-x}Sb{sub x}/InAs strained-layer superlattice (SLS) semiconductors and thick epitaxial layers of InAs{sub 1-x}Sb{sub x} were grown under a variety of conditions by metal-organic chemical vapor deposition on InAs substrates. The III/V ratio was varied from 0.026 to 1.0 over a temperature range of 475--525C, at pressures of 200 to 660 torr and growth rates of 0.75 to 3.0 {mu}m/hour. The composition of the ternary can be predicted from the input gas molar flow rates using a thermodynamic model. At lower temperatures, the thermodynamic model must be modified to take account of the incomplete decomposition of arsine and trimethylantimony. These layers were characterized by optical microscopy, SIMS, and x-ray diffraction. The optical properties of these SLS`s were determined by infrared photoluminescence and absorption measurements. The PL peak energies of the alloys` and the SLS`s are consistently lower than the previously reported values for the bandgap of InAs{sub 1-x}Sb{sub x} alloys.
Date: June 1, 1993
Creator: Biefeld, R. M.; Baucom, K. C. & Kurtz, S. R.
Partner: UNT Libraries Government Documents Department

Growth of epitaxial semiconductor alloys and superlattices with continuously variable composition by pulsed-laser ablation

Description: We describe a new method to grow epitaxial semiconductor alloys with continuously variable composition, while using a single pulsed laser ablation target of fixed composition. Epitaxial ZnSe{sub 1{minus}x}S{sub x} films with continuously variable sulfur content ``x`` were grown by ablating a ZnSe target through low-pressure ambient H{sub 2}S gas. The sulfur content was easily controlled by varying the H{sub 2}S partial pressure. The composition of ZnSe{sub 1{minus}x}S{sub x} films differs by as much as x = 0.52 from the pure ZnSe target. We have used this method to grow heteroepitaxial structures with either continuously graded or periodically repeating, abrupt compositional changes (compositional superlattices). Structures that simultaneously incorporate both types of compositional modulation also have been grown. This development removes the principal barrier to convenient pulsed-laser ablation (PLA) growth of compositionally graded semiconductor thin-film materials, namely that the film and target normally have the same composition. The method appears to have broad application for PLA growth of other compound semiconductor films and heterostructures, as well as for doping individual layers.
Date: August 1, 1993
Creator: McCamy, J. W. & Lowndes, D. H.
Partner: UNT Libraries Government Documents Department

Experimental investigations of superconductivity in quasi-two-dimensional epitaxial copper oxide superlattices and trilayers

Description: Epitaxial trilayer and superlattice structures grown by pulsed laser ablation have been used to study the superconducting-to-normal transition of ultrathin (one and two c-axis unit cells) YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} layers. The normalized flux-flow resistances for several epitaxial structures containing two-cell-thick YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} films collapse onto the ``universal`` curve of the Ginzburg-Landau Coulomb Gas (GLCG) model. Analysis of normalized resistance data for a series of superlattices containing one-cell-thick YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} layers also is consistent with the behavior expected for quasi-two-dimensional layers in a highly anisotropic, layered three-dimensional superconductor. Current-voltage measurements for one of the trilayer structures also are consistent with the normalized resistance data, and with the GLCG model. Scanning tunneling microscopy, transmission electron microscopy, and electrical transport studies show that growth-related steps in ultrathin YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} layers affect electrical continuity over macroscopic distances, acting as weak links. However , the perturbation of the superconducting order parameter can be minimized by utilizing hole-doped buffer and cap layers, on both sides of the YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} layer, in trilayers and superlattices. These results demonstrate the usefulness of epitaxial trilayer and superlattice structures as tools for systematic, fundamental studies of high-temperature superconductivity.
Date: June 1, 1993
Creator: Lowndes, D. H. & Norton, D. P.
Partner: UNT Libraries Government Documents Department

Superlattice crystal accelerator: Acceleration beyond GeV/m

Description: Here, an idea of using a visible light wave to accelerate relativistic particles via the inverse FEL mechanism is explored. A strain modulated crystal structure -- the superlattice, plays the role of a microscopic undulator providing very strong ponderomotive coupling between the beam and the light wave. Purely classical treatment of relativistic protons channeling through a superlattice is performed in a self consistent fashion involving the Maxwell wave equation for the accelerating electromagnetic field and the relativistic Boltzmann equation for the protons. It yields the accelerating efficiency in terms of the negative gain coefficient for the amplitude of the electromagnetic wave -- the rate the energy is extracted from the light by the beam. Presented analytic formalism allows one to find the acceleration rate in a simple closed form, which is further evaluated for a model beam -- optical cavity system to verify feasibility of this scheme.
Date: May 1, 1993
Creator: Bogacz, S. A.
Partner: UNT Libraries Government Documents Department

Deposition and properties of novel nitride superlattice coatings. Progress report, September 28, 1990--April 1993

Description: We have carried out detailed studies of the processing, structure, and properties of certain polycrystalline superlattice coatings, including TiN/NbN, TiN/VN, TiN/Ni, and TiN/NiCr, which were produced using an opposed, dual-cathode, high-rate, reactive, unbalanced-magnetron sputtering system. The coatings exhibited hardness values as high as 5200 kgf/mm{sup 2} for TiN/NbN, 5100 for TiN/VN, 3500 for TiN/Ni, and 3200 for TiN/NiCr. These hardness values are all twice higher than their corresponding rule-of-mixture hardness values. The structure and properties of the coatings are a strong function of superlattice period, partial pressure of N{sub 2}, and energy and flux of ion bombardment during deposition. Possible mechanisms for hardness enhancement in the polycrystalline superlattice appear to be a result of dislocation blocking due to coherency strains, difference in dislocation line energies between layers, and small grain sizes. In response to high interest shown by industry, BIRL formed a 2-year Industrial Group Program, currently with 12 members, to transfer the superlattice coating technology.
Date: April 1, 1993
Creator: Barnett, S. A.; Sproul, W. D. & Wong, M. S.
Partner: UNT Libraries Government Documents Department

New concepts for high efficiency energy conversion: The avalanche heterostructure and superlattice solar cells. Subcontract report, 1 June 1987--31 January 1990

Description: This report describes investigation into the theory and technology of a novel heterojunction or superlattice, single-junction solar cell, which injects electrons across the heterointerface to produce highly efficient impact ionization of carriers in the lowband-gap side of the junction, thereby conserving their total energy. Also, the superlattice structure has the advantage of relaxing the need for perfect lattice matching at the p-n interface and will inhibit the cross diffusion of dopant atoms that typically occurs in heavy doping. This structure avoids the use of tunnel junctions that make it very difficult to achieve the predicted efficiencies in cascade cells, thus making it possible to obtain energy efficiencies that are competitive with those predicted for cascade solar cells with reduced complexity and cost. This cell structure could also be incorporated into other solar cell structures designed for wider spectral coverage.
Date: January 1, 1993
Creator: Summers, C. J.; Rohatgi, A.; Torabi, A. & Harris, H. M.
Partner: UNT Libraries Government Documents Department

Electronic states in systems of reduced dimensionality. Progress report, September 15, 1991--September 14, 1992

Description: This report briefly discusses the following research: magnetically modulated systems, inelastic magnetotunneling, ballistic transport review, screening in reduced dimensions, raman and electron energy loss spectroscopy; and ballistic quantum interference effects. (LSP).
Date: April 15, 1992
Creator: Ulloa, S. E.
Partner: UNT Libraries Government Documents Department

Magnetic excitations in antiferromagnetically coupled superlattices: Fe/Mo and Fe/Cr

Description: Here we report the results of a Brillouin light scattering (BLS) study of magnetic excitations in antiferromagnetically (AF) coupled Fe/Mo and Fe/Cr superlattices. This technique, already been applied to AF coupled tri-layer films shows that these systems reflect coupling (ferromagnetic and antiferromagnetic) between ferromagnetic layers. However since in ordinary magnetic superlattices, new collective modes exist resulting from dipolar coupling of the ferromagnetic layers, it could be expected that these new antiferromagnetic systems will also show novel behaviour. In this manuscript, only the magnetization and BLS results are presented and discussed.
Date: January 1, 1993
Creator: Grimsdtich, M.; Kumar, S. & Fullerton, E. E.
Partner: UNT Libraries Government Documents Department

Magneto-optical multilayers

Description: Magneto-optical multilayers are of interest to the optical data storage community as a possible second-generation medium of the future. The important Co/Pt-superlattice system is introduced in this respect, and an extensive reference listing is provided to previous research. Magneto-optical modeling studies of Co/Pt are presented, and it is concluded that the interfacial Pt is magnetized and is magneto-optically active at the short wavelengths of interest ({approximately}4 eV) for applications. Magneto-optics in the ultrathin limit are discussed, and an additivity law is presented and verified experimentally utilizing data for epitaxial Fe/Ag(111) superlattices. Finally, the surface magnetic anisotropy that provides the vertical easy axes of magnetization in candidate superlattice systems is discussed and illustrated experimentally using ultrathin epitaxial films of Fe grown on a variety of substrates. It is concluded that magneto-optic multilayers will provide many stimulating basic and applied challenges in the years ahead.
Date: February 1, 1992
Creator: Bader, S. D.
Partner: UNT Libraries Government Documents Department

X-ray diffraction study of GaSb/AlSb strained-layer-superlattices grown on miscut (100) substrates

Description: A series of superlattices were grown by molecular beam epitaxy on (100) GaSb substrates which had been miscut by 2, 3, and 4 degrees toward the <011> direction. These superlattices were then studied by scanning all possible [444] or [511] (asymmetric) reflections with high resolution multiple-crystal x-ray diffractometry. In addition, the (400) (quasi-symmetric) reflection was scanned. From peak splittings we extracted mismatch and tilt parameters for the epitaxial unit cell. We compared our results for the non-tetragonal component of the distortion ot calculations based on the coherent strain model of Hornstra and Bartels (J. Cryst. Growth 44,513 (1978)). We find that this model which was developed for epitaxial growth on a general (hkl) plane also describes our results for growth on vicinal (100) planes. The resolution of our data is sufficient to establish that the distortion was not purely tetragonal. A monoclinic unit cell symmetry adequately describes our results.
Date: July 1, 1991
Creator: Macrander, A. T.; Schwartz, G. P.; Guiltieri, G. J. & Gilmer, G.
Partner: UNT Libraries Government Documents Department

Magnetic metallic multilayers

Description: Utilizing self-consistent Hartree-Fock calculations, several aspects of multilayers and interfaces are explored: enhancement and reduction of the local magnetic moments, magnetic coupling at the interfaces, magnetic arrangements within each film and among non-neighboring films, global symmetry of the systems, frustration, orientation of the various moments with respect to an outside applied field, and magnetic-field induced transitions. Magnetoresistance of ferromagnetic-normal-metal multilayers is found by solving the Boltzmann equation. Results explain the giant negative magnetoresistance encountered in these systems when an initial antiparallel arrangement is changed into a parallel configuration by an external magnetic field. The calculation depends on (1) geometric parameters (thicknesses of layers), (2) intrinsic metal parameters (number of conduction electrons, magnetization, and effective masses in layers), (3) bulk sample properties (conductivity relaxation times), (4) interface scattering properties (diffuse scattering versus potential scattering at the interfaces, and (5) outer surface scattering properties (specular versus diffuse surface scattering). It is found that a large negative magnetoresistance requires considerable asymmetry in interface scattering for the two spin orientations. Features of the interfaces that may produce an asymmetrical spin-dependent scattering are studied: varying interfacial geometric random roughness with no lateral coherence, correlated (quasi-periodic) roughness, and varying chemical composition of the interfaces. The interplay between these aspects of the interfaces may enhance or suppress the magnetoresistance, depending on whether it increases or decreases the asymmetry in the spin-dependent scattering of the conduction electrons.
Date: April 1, 1994
Creator: Hood, R. Q.
Partner: UNT Libraries Government Documents Department

The optimization of interfaces in InAsSb/InGaAs strained-layer superlattices grown by metal-organic chemical vapor deposition

Description: We have prepared InAsSb/InGaAs strained-layer superlattice (SLS) semiconductors by metal-organic chemical vapor deposition (MOCVD) under a variety of conditions. Presence of an InGaAsSb interface layer is indicated by x-ray diffraction patterns. Optimized growth conditions involved the use of low pressure, short purge times, and no reactant flow during the purges. MOCVD was used to prepare an optically pumped, single heterostructure InAsSb/InGaAs SLS/InPSb laser which emitted at 3.9 {mu}m with a maximum operating temperature of approximately 100 K.
Date: December 31, 1993
Creator: Biefeld, R. M.; Baucom, K. C. & Kurtz, S. R.
Partner: UNT Libraries Government Documents Department