bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of oxygen-implant isolation on the recombination leakage current of n-p+ AlGaAs graded heterojunction diodes
Authors: Watanabe Kazuo , Nagata Koichi , Yamazaki Hajime , Ishida Satoru , Ichijo Takehisa
Published: July 2002

The recombination leakage current induced by planar isolation of n-p+AlGaAs graded heterojunction area with oxygen ion implantation followed by annealing at 500–650 °C has been investigated. The recombination leakage current is smaller than that induced by conventional isolation with hydrogen ion implantation; specifically, it is about one order of magnitude smaller after the higher temperature (600–650 °C) annealing. The main origin of the remaining recombination leakage current is probably not oxygen deep levels but rather recombination centers related to the ion implantation damage that remains after annealing. A point-defect complex level, which may be related to the recombination center, is detected at an activation energy of around 0.8 eV by deep level transient spectroscopy.
Charge-state-dependent iron precipitation in silicon
Authors: Mesli A. , Heiser T. , Amroun N. , Siffert P.
Published: July 2002

The kinetics of interstitial iron precipitation in p-type silicon are investigated. During annealing, the iron charge state is controlled by the applied reverse voltage and its effect on the precipitation is studied. We observe that iron in the neutral charge state (Fe0i) precipitates preferentially in three-dimensional nucleation centers while Fe+ivanishes in the dislocation lines (rod-like nucleation centers). These centers are created during the fast cooling procedure necessary to dissolve iron in the silicon matrix.
Possible dislocation multiplication source in (001) semiconductor epitaxy
Authors: Washburn J. , Kvam E. P.
Published: July 2002

A cross-slip mechanism, based on a commonly observed dislocation configuration and which can produce multiple misfit dislocations in the direction orthogonal to the initial slip direction, is put forth. The mechanism has eight crystallographic variants in (001) epitaxy, and is itself repeatable. The essence of the model is the configuration of the threading dislocation in the epilayer, which bends, avoiding an acute angle between the near-surface screw segment and interfacial segment, resulting in a pinning point in the cross-slip plane which is removed by some distance from the heterointerface.
Metalorganic chemical vapor deposition of Tl2Ba2CaCu2Ox superconducting thin films using fluorinated β-diketonate source reagents
Authors: Hamaguchi N. , Gardiner R. , Kirlin P. S. , Dye R. , Hubbard K. M. , Muenchausen R. E.
Published: July 2002

Superconducting Tl2Ba2CaCu2Ox films were fabricated using a three-step process. Amorphous BaCaCuOF films were deposited on MgO(100) single-crystal substrates by metalorganic chemical vapor deposition at 500 °C using fluorinated β-diketonate complexes of Ba, Ca, and Cu. The fluorine was stripped in wet oxygen at 785 °C and c-axis oriented Tl2Ba2CaCu2Ox films were then formed by annealing in dry at 870 °C in the presence of Tl2O3/Ba2Ca2CuN3Ox pellets. The best films showed onsets of superconductivity at 125 K and zero resistivity was achieved by 108 K. Critical current densities as high as 104 A/cm2 were obtained at 90 K.
Reaction patterning of YBa2Cu3O7−δ thin films on Si
Authors: Fork D. K. , Barrera A. , Geballe T. H. , Viano A. M. , Fenner D. B.
Published: July 2002

A novel technique exploiting the severe chemical reaction between Si and YBa2Cu3O7−δ (YBCO) has been developed for patterning epitaxial YBCO films in situ. Patterning is achieved by etching features in epitaxial YSZ on Si(100), and then depositing a final layer of YBCO; the material which grows on the exposed Si is insulating. Linewidths down to 3 μm have been demonstrated with a zero resistance critical temperature (Tc) of 86 K and a transport critical current density of 1.6×106 A/cm2 at 77 K. 45° and low-angle twist grain boundaries occur under some circumstances but can be eliminated by regrowing 20 Å of homoepitaxial YSZ on the surface prior to YBCO growth. Si diffusion in insulating portions has been characterized by x-ray photoemission spectroscopy, indicating vertical diffusion through the film.
Aligned and twinned orientations in epitaxial CoSi2 layers
Authors: Vanderstraeten H. , Bruynseraede Y. , Wu M. F. , Vantomme A. , Langouche G. , Phillips J. M.
Published: July 2002

Heteroepitaxial CoSi2 layers have been made by ion beam synthesis and solid phase epitaxy in Si〈111〉 substrates. Using the x-ray rocking curves of the asymmetric (331) reflections we are able to determine very accurately the relative amount of aligned (type A) and twinned (type B) CoSi2 in samples with different thicknesses. It is shown that for epilayers thinner than 360 Å, the relative amount of type A CoSi2 decreases from 100% to 30%.
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u growth of superconducting YBa2Cu3O7−δ thin films on Si with conducting indium-tin-oxide buffer layers
Authors: Kellett B. J. , James J. H. , Gauzzi A. , Dwir B. , Pavuna D. , Reinhart F. K.
Published: July 2002

Superconducting YBa2Cu3O7−δ (YBCO) thin films have been grown in situ on Si with conducting indium-tin-oxide (ITO) buffer layers. ITO allows YBCO to be electrically connected to the underlying Si substrate. Both the YBCO film and ITO buffer layer, grown by ion beam sputtering, are textured and polycrystalline with a combined room- temperature resistivity of about 2 mΩ cm. Superconducting onsets are 92 K with zero resistance at 68 K.
Microstructure of Cu- and Y-rich YBa2Cu3O7−x thin films: Identification of the CuYO2 phase
Authors: Marshall A. F. , Matijasevic V. , Rosenthal P. , Shinohara K. , Hammond R. H. , Beasley M. R.
Published: July 2002

The CuYO2 delafossite-type structure has been identified as a second phase in thin films of Cu- and Y-rich YBa2Cu3O7−x (123) made by electron beam co-evaporation at conditions of low oxygen pressure; this phase occurs as extremely small, densely distributed, highly oriented precipitates within the 123 matrix. The smallest (sub-100 Å) [00.1] oriented precipitates of this hexagonal phase are strained to give a better lattice match to the surrounding 123 structure. The results suggest that, for thin film deposition conditions of sufficiently low temperature and pressure, there may be a tie line between YBa2Cu3O7−x and CuYO2 in the equilibrium phase diagram. The size and distribution of the precipitates is such as would be expected to influence structurally sensitive superconducting transport properties.
Epitaxial growth of Bi-Sr-Ca-Cu-O superconducting thin films by metalorganic chemical vapor deposition
Authors: Sugimoto T. , Yoshida M. , Yamaguchi K. , Sugawara K. , Shiohara Y. , Tanaka S.
Published: July 2002

The epitaxial growth of Bi-Sr-Ca-Cu-O thin films was achieved by metalorganic chemical vapor deposition. The film-MgO substrate interface has been examined and discussed using the cross-sectional transmission electron microscopy. On the smooth surface of the MgO substrate, the lattice of the film was ordered from the first atomic layer on the surface of the substrate, and the misfit dislocations caused by the large lattice mismatch between the film and the MgO substrate appeared every four or five lattices. The first Bi2O2 layer on the substrate surface was found to be regularly arranged regardless of the roughness of the substrate surface. The x-ray diffraction patterns of the films as a function of the growth time showed that the high Tc phase (Bi2Sr2Ca2Cu3Ox) was not formed in the early stage of the growth while its amount increased as the growth was prolonged. These results suggest that the high Tc phase is not directly grown but formed via the low Tc phase (Bi2Sr2CaCu2Ox) or semiconducting phase (Bi2Sr2CuOx) with the thermal diffusion limited growth of Cu-O and Ca layers. Even an 8-nm-thick film was found to be free of the compressive stress forming misfit dislocations observed in the transmission electron microscope photograph of the thicker film, since the length of the c axis in the 8-nm-thick film is not enlarged from the result of the x-ray diffraction pattern.
Dislocation velocity in indium phosphide
Authors: Yonenaga Ichiro , Sumino Koji
Published: July 2002

Velocities of α, β, and screw dislocations in InP crystals generated from surface scratches were measured as a function of stress and temperature by means of the etch pit technique. Effects of Zn and S impurities, acting as acceptor and donor, respectively, on the dislocation velocity were also investigated. lt was found that Zn impurity strongly retards the motion of all types of dislocations. On the other hand, S impurity is found to reduce the mobilities of β and screw dislocations while it enhances the mobility of α dislocations.
Electroluminescence and photoluminescence from Si1−xGex alloys
Authors: Rowell N. L. , Noël J.-P. , Houghton D. C. , Buchanan M.
Published: July 2002

Electroluminescence has been observed from Si1−xGex/Si p-n heterostructures grown by molecular beam epitaxy and fabricated into mesa diodes. The luminescence from each sample was observed at temperatures up to 80 K with diodes forward biased at current densities up to 50 A/cm2. For x=0.18 and x=0.25, broad (∼80 meV) electroluminescence peaks were observed at 890 and 860 meV, respectively. These energies as well as the peak shapes and quantum efficiencies (∼1%) were the same as those from corresponding photoluminescence spectra.
Native-oxide-defined coupled-stripe AlxGa1−xAs-GaAs quantum well heterostructure lasers
Authors: Dallesasse J. M. , Holonyak N. , Hall D. C. , El-Zein N. , Sugg A. R. , Smith S. C. , Burnham R. D.
Published: July 2002

Data are presented on the continuous-wave (cw) room-temperature (300 K) operation of multiple stripe AlxGa1−xAs-GaAs quantum well heterostructure (QWH) laser arrays defined with native oxide contact masking. Use of the native AlxGa1−xAs(x≳0.7) oxide allows the fabrication of high-performance devices without depositing foreign oxide or dielectric layers (SiO2 or Si3N4). Arrays of ten 5-μm-wide emitters on 7 μm centers are coupled and operate at powers as high as 300 mW per facet, or at wider stripe spacing (5 μm emitters on 10 μm centers) as high as 400 mW per facet. These data indicate that current blocking layers of native oxide, formed from AlxGa1−xAs with H2O vapor in N2 carrier gas (400 °C, 3 h), can be used in the construction of high-power multiple stripe QWH arrays with excellent performance characteristics.
Low-temperature metalorganic chemical vapor deposition of InP on Si(001)
Authors: Grundmann M. , Krost A. , Bimberg D.
Published: July 2002

We report successful growth of antiphase domain-free InP on Si(001) without any preannealing of the Si substrate using low-pressure metalorganic chemical vapor deposition in contrast to present belief that high-temperature substrate annealing prior to growth is imperative to achieve this goal. Optimized crystallographic and optical properties are obtained for an offcut along [11̄0] of 4°±0.4°, an InP buffer layer temperature of 400 °C±10 °C, a layer deposition temperature of 640 °C, and low growth rates r≤2.7 μm/h.
Reflection high-energy electron diffraction observation of GaAs surface-prepared ultrasonic running de-ionized water treatment
Authors: Hirota Y. , Homma Y. , Sugii K.
Published: July 2002

GaAs (001) surface ultrasonically cleaned under running de-ionized water (U-RDIW) is investigated by reflection high-energy electron diffraction (RHEED). The RHEED observations of U-RDIW-treated surfaces show a spotty (1×1) pattern at room temperature and a (2×1) streaky surface reconstruction pattern at 360 °C. The experimental results indicate that chemically clean and damage-free GaAs surfaces can be produced by U-RDIW treatment. We discuss surface structures before/after heating using a hydrogen- terminated model.
Formation of CuInSe2 thin films by rapid thermal recrystallization
Authors: Mooney G. D. , Hermann A. M. , Tuttle J. R. , Albin D. S. , Noufi R.
Published: July 2002

Polycrystalline thin-film CuInSe2 has been formed by rapid thermal processing of vacuum codeposited Cu, In, and Se. Films were fabricated and characterized in three composition regions: Cu-poor (∼20 at. % Cu), stoichiometric (25 at. %), and Cu-rich (∼28 at. %). Characterization results are presented including x-ray diffraction analysis, electron probe for microanalysis, scanning electron microscopy, and optical reflection and transmission measurements. Results show that nearly single-phase material has been formed from codeposited precursors with a post-deposition annealing time of less than 2 min. The films have optical absorption coefficients in the high 104 cm−1 range with minimum subgap absorption, and an optical band gap of 1.0 eV with smooth morphologies amenable to photovoltaic device fabrication.
Reduced dislocation density in Ge/Si epilayers
Authors: Kvam E. P. , Namavar F.
Published: July 2002

Mismatched epilayers, for which the coherency strain has been relieved by misfit dislocation introduction, typically exhibit high epithreading dislocation densities. When the misfit is substantial, as for Ge or GaAs grown by molecular beam epitaxy onto (001) Si substrates, the density is regularly over 109 cm−2. We have grown Ge on Si (111) and (001) with epithreading dislocation densities in the 106 cm−2 range by use of chemical vapor deposition. This is because longer, and thus fewer, misfit dislocations appear for strain relief. Potential explanations for this are postulated. The most likely reason is that thermally activated dislocation glide is much faster at chemical vapor deposition growth temperatures.
Low-threshold disorder-defined native-oxide delineated buried-heterostructure AlxGa1−xAs-GaAs quantum well lasers
Authors: Kish F. A. , Caracci S. J. , Holonyak N. , Dallesasse J. M. , Höfler G. E. , Burnham R. D. , Smith S. C.
Published: July 2002

Impurity-induced layer disordering (IILD) along with oxidation (native oxide) of high-gap AlxGa1−xAs confining layers is employed to fabricate low-threshold stripe-geometry buried-heterostructure AlxGa1−xAs-GaAs quantum well heterostructure (QWH) lasers. Silicon IILD is used to intermix the quantum well and waveguide regions with the surrounding confining layers (beyond the laser stripe) to provide optical and current confinement in the QW region of the stripe. The high-gap AlxGa1−xAs upper confining layer is oxidized in a self-aligned configuration defined by the contact stripe and reduces IILD leakage currents at the crystal surface and diffused shunt junctions. AlxGa1−xAs-GaAs QWH lasers fabricated by this method have continuous 300 K threshold currents as low as 5 mA and powers ≳ 3l mW/facet for ∼ 3-μm-wide active regions.
Experimental observation of large room-temperature current gains in a Stark effect transistor
Authors: Collins D. A. , Chow D. H. , McGill T. C.
Published: July 2002

We report experimental observation of room-temperature current gains as large as 50 in a novel transistor grown in the InAs/GaSb/AlSb material system. Due to the unique degree of flexibility this material system offers in choosing band alignments, the base and collector terminals are separated by a quantum barrier while electrons traveling between the emitter and collector terminals do not tunnel across any classically forbidden regions, even though a quasi-bound state exists in the quantum well collector. This asymmetry in current conduction between the terminals of the device leads to transistor action: applying a bias to the base terminal electrostatically modulates the emitter-collector current through Stark shifts of the energy levels in the quantum well collector, while the quantum barrier between the base and collector terminals suppresses the base current. Because transport through the structure is dependent on resonant transmission, this novel transistor holds promise for the fabrication of high-speed circuits.
Resonant tunneling of two-dimensional electrons into one-dimensional subbands of a quantum wire
Authors: Zaslavsky A. , Tsui D. C. , Santos M. , Shayegan M.
Published: July 2002

Liquid phase epitaxy regrowth on the edge of in situ cleaved substrates is employed to create a vertical two-dimensional electron gas in a double-barrier tunneling potential. Resonant tunneling of two-dimensional electrons through one-dimensional quantum wire subbands is unambiguously identified by negative differential resistance features in the transport characteristics. The bias positions of these features agree with simple tunneling theory estimates based on conservation laws and the calculated band alignment in the structure under bias.
Visible optical parametric oscillation in LiB3O5
Authors: Wang Yunping , Xu Zuyan , Deng Daoqun , Zheng Wanhua , Wu Baichang , Chen Chuangtian
Published: July 2002

The successful operation of a visible optical parametric oscillator (OPO) using a LiB3O5 crystal as the nonlinear element is reported. An energy conversion efficiency as high as 22% for a signal wave has been obtained in a 15.9-mm-long crystal. This OPO can generate visible output energy of 2.7 mJ and be continuously tuned from 435 to 1922 nm.
5 GHz modulation of a mushroom mesa surface emitting laser
Authors: Dziura T. G. , Yang Y. J. , Fernandez R. , Wang S. C.
Published: July 2002

A modulation bandwidth approaching 5 GHz in a GaAs quantum well vertical cavity surface emitting laser with a mushroom mesa structure is reported. The modulation speed and the maximum power of 1.5 mW were limited by device heating. The second harmonic distortion as a function of frequency was measured at an injection current twice threshold and an optical modulation index of 10%, and a peak distortion of about −25 dBc was obtained.
Quantum well width and In composition effects on the operating characteristics of InGaAs/GaAs strained single quantum well diode lasers
Authors: Ben-Michael R. , Fekete D. , Sarfaty R.
Published: July 2002

In this work we study the effect of strain on the performance of highly strained InxGa1−xAs/GaAs/GaAlAs quantum well lasers (SQWL). We changed the indium concentration and the QW width and found that the threshold current density, Jth, is minimal with x∼0.4 when the width of the QW is 20 Å. For x=0.3 the minimal Jth was obtained with a 90 Å active layer. The best performing laser reported in this work has Jth=68 A/cm2 emitting at 1.063 μm with cavity length of 2022 μm. Comparison with GaAs/GaAlAs lasers is possible because both structures have the same optical mode confinement, and the comparison shows that SQWLs have indeed lower Jth, but the improvement in Jth with the strain is not as dramatic as predicted theoretically.
Native-oxide coupled-cavity AlxGa1−xAs-GaAs quantum well heterostructure laser diodes
Authors: El-Zein N. , Kish F. A. , Holonyak N. , Sugg A. R. , Ries M. J. , Smith S. C. , Dallesasse J. M. , Burnham R. D.
Published: July 2002

Data are presented demonstrating AlxGa1−xAs-GaAs quantum well heterostructure laser diodes consisting of an array of coupled cavities (19 μm long on 22 μm centers, ∼250 μm total length) arranged lengthwise in single 10-μm-wide laser stripes. The cavities are defined by a native oxide formed from a significant portion of the high-gap AlxGa1−xAs upper confining layer. The native oxide (grown at 425 °C in H2O vapor+N2 carrier gas) confines the injected carriers and optical field within the cavities, resulting in reflection and optical feedback distributed periodically along the laser stripe. These diodes exhibit single-longitudinal-mode operation over an extended range (relative to similar diodes fabricated without multiple cavities). At high current injection levels, longitudinal-mode spectra demonstrate unambiguously oscillation from the internal coupled cavities.
First direct observation of voids in bulk, undoped, semi-insulating GaAs
Authors: Williams G. M. , Cullis A. G. , Stirland D. J.
Published: July 2002

Defect selective A/B chemical etching, low-temperature scanning cathodoluminescence, and transmission electron microscopy have been used to study the microstructure of undoped, semi-insulating liquid-encapsulated Czochralski GaAs wafers. It is shown for the first time that a distribution of microvoids is present in the bulk material at a number density of at least 1010 cm−3. These microvoids, which are present in the centers of the dislocation cell structures observed in the GaAs, may result from the post-growth heat treatment of ingots which is used to improve the material homogeneity. A possible explanation for the formation of these microvoids is given.
Femtosecond response of electro-optic poled polymers
Authors: Ferm Paul M. , Knapp Charles W. , Wu Chengjiu , Yardley James T. , Hu Bin-Bin , Zhang Xi-Cheng , Auston David H.
Published: July 2002

We investigate the ultrafast electro-optic response and sensitivity of a poled side chain polymer film via the electro-optic sampling technique. A 760 fs rise-time electrical transient is observed corresponding to a bandwidth of 460 GHz. We believe this to be device limited and not due to limitations in the speed of response of the polymer.
Chemical imidization for enhanced thermal stability of poled electro-optic response in polyimide guest-host systems
Authors: Wu J. W. , Valley J. F. , Ermer S. , Binkley E. S. , Kenney J. T. , Lytel R.
Published: July 2002

Chemical imidization at room temperature is employed as a novel curing process for dc electric field poled electro-optic (EO) polyimide guest-host systems. Dehydration occurring through imidization of the polyamic acid is completed chemically after poling rather than thermally during poling. After thermal aging at 155 °C (above the poling temperature) chemically imidized samples retain over 30% of their original poling induced EO signal while similarly poled samples, which have not been chemically imidized, produce a null EO response.
Radical-assisted organometallic vapor-phase epitaxial growth of GaAs
Authors: Li S. H. , Chen C. H. , Jaw D. H. , Stringfellow G. B.
Published: July 2002

For the first time, radicals have been added to assist organometallic vapor-phase epitaxial (OMVPE) growth of GaAs at low temperatures. Supplemental t-C4H9 radicals from the pyrolysis of azo-t-butane [(t-C4H9)2N2] were used to increase the growth rate of GaAs from trimethylgallium [TMGa, (CH3)3Ga] and arsine (AsH3) at temperatures as low as 390 °C. Mass spectroscopy studies show that the added radicals enhance the decomposition rates of both TMGa and AsH3. The GaAs growth rate was increased by a factor of 6 at 450 °C. The radical-assisted OMVPE grown samples are, indeed, GaAs based on microprobe analysis. Spectra from Raman scattering experiments further confirm that the GaAs is single crystalline.
Subnanosecond burning of persistent spectral holes by donor-acceptor electron transfer in tetraphenylporphine/p-benzoquinone systems
Authors: Suzuki Hiroyuki , Shimada Toshiyuki
Published: July 2002

The first observation of subnanosecond spectral hole burning is reported in tetraphenylporphine/p-benzoquinone embedded in poly(methylmethacrylate) at liquid-helium temperature. The hole formation mechanism is photoinduced one-photon donor-acceptor electron transfer, and is consistent with the mechanism predicted by the reaction exothermicity accompanying the reaction. Spectral holes burnt in the present system disappeared almost completely when the temperature was increased to 20 K.
Improvement of the optical and photoelectric properties of hydrogenated amorphous silicon-carbon alloys by using trisilylmethane as a feedstock
Authors: Li Y.-M. , Fieselmann B. F.
Published: July 2002

Hydrogenated amorphous silicon-carbon alloys (a-SiC:H) with band gaps around 1.9 eV have been prepared using trisilylmethane (TSM) as the carbon source by plasma-enhanced chemical vapor deposition. Compared to a-SiC:H alloys prepared from the conventional CH4/SiH4 mixture, the TSM-based films show sharper optical-absorption edge, weaker defect-related optical absorption, lower methyl group concentration, longer ambipolar diffusion length, and higher photoconductivity.
Ion-beam synthesis of a Si/β-FeSi2/Si heterostructure
Authors: Oostra D. J. , Vandenhoudt D. E. W. , Bulle-Lieuwma C. W. T. , Naburgh E. P.
Published: July 2002

Ion-beam synthesis of a buried β-FeSi2 layer in Si is demonstrated. In the experiments Si(111) substrates have been implanted with 450-keV Fe+ ions. Samples have been analyzed by Rutherford backscattering spectrometry, x-ray diffraction, and transmission electron microscopy. Annealing at 900 °C of samples implanted with 6×1017 Fe+/cm2 causes formation of a buried layer consisting of grains with lateral dimensions of approximately 5 μm. The epitaxy of β-FeSi2 (110) and/or (101) planes parallel to the Si(111) substrate plane is observed.
Microcrystalline diamond deposition using a combustion flame of acetylene and oxygen with a magnetic field
Authors: Abe Toshimi , Suemitsu Maki , Miyamoto Nobuo , Sato Noriyoshi
Published: July 2002

Microcrystalline diamonds were successfully deposited on an abraded molybdenum surface under a magnetic field using a combustion flame of acetylene (C2H2) and oxygen (O2) gases. The deposition rate was about 1 μm/min, which is an order larger than that obtained by conventional chemical-vapor-deposition methods. The magnetic field led to an increase of the deposited area and of the microcrystal diameter. The microcrystals show good crystallinity as observed from scanning electron microscopy, reflective electron diffraction, and x-ray diffraction measurements.
Effect of helium dilution during plasma-enhanced deposition on electron trapping in silicon dioxide thin films
Authors: Park Y. C. , Johnson N. M. , Jackson W. B. , Stevens K. S. , Smith D. L. , Hagstrom S. B.
Published: July 2002

The effect of helium dilution during plasma-enhanced chemical vapor deposition (PECVD) of silicon dioxide thin films was studied with avalanche injection and charge trapping techniques. It is shown that, while oxides deposited with He dilution can have low bulk trap densities, they are not lower than films deposited without He dilution. We thus present a more complete specification than previously available of the range of gas-phase deposition conditions that produce device-grade silicon dioxide.
Effects of hydrogen and deposition pressure on Si1−xGex growth rate
Authors: Jang Syun-Ming , Reif Rafael
Published: July 2002

Si1−xGex films were deposited at 620 °C by very low pressure chemical vapor deposition. The effects of H2 dilution and deposition pressure on Si1−xGex growth rate were examined. Under the conditions employed here, both H2 dilution and deposition pressure were found to affect the growth rate and its peak as a function of Ge incorporation in the film. The suppression of Si1−xGex growth rate from H2 at low Ge contents was observed. The growth rate enhancement by increasing deposition pressure is dependent on Ge content and becomes more significant as Ge increases. The implications of these observations for Si1−xGex growth rate are discussed.
Superior microwave properties by post-annealing YBa2Cu3O7 thin films at low oxygen partial pressure
Authors: Mogro-Campero A. , Turner L. G. , Kadin A. M. , Mallory D. S.
Published: July 2002

YBa2Cu3O7 (YBCO) thin films with improved properties have been recently reported by post-annealing in a low partial pressure of oxygen, similar to that used by in situ methods, compared to the usual post-annealing in 1 atm of oxygen. Here it is shown that the improvements extend to the microwave surface resistance. The surface resistance was measured at close to 10 GHz; the scaled value at 10 GHz and at 77 K is 240 μΩ. This value is as low as has been reported for YBCO thin films measured around 10 GHz made by any method, and is two orders of magnitude lower than the surface resistance of copper at the same temperature and frequency.
Simultaneous blue and green second harmonic generation in quasiphase matched LiNbO3 waveguide
Authors: Cao Xiaofan , Srivastava Ramakant , Ramaswamy Ramu V.
Published: July 2002

We report the first simultaneous quasiphase matched second harmonic generation (SHG) of blue (433 nm) and green (532 nm) light in LiNbO3 channel waveguides. Up to 0.45 mW (0.25 mW) of blue (green) light was obtained stimultaneously with an efficiency of 22%/W (28%/W). This result is made possible by using a 6.8 μm period domain inversion grating which serves as a first-order (second-order) grating for green (blue) generation simultaneously. We also show that further enhancement in the SHG performance can be obtained by choosing the appropriate grating depth.
Selective low pressure chemical vapor deposition of copper: Effect of added water vapor in hydrogen or helium carrier gas
Authors: Lecohier B. , Calpini B. , Philippoz J.-M. , Stumm T. , van den Bergh H.
Published: July 2002

The low pressure chemical vapor deposition (LPCVD) of copper from its bis-hexafluoroacetylacetonate is studied on oxidized silicon substrates partially covered with a platinum seeding layer. With a known concentration of water vapor in the gas mixture, almost equal copper film growth rates are obtained when using either hydrogen or helium as carrier gas. For both carrier gases, an increase of the copper growth rate is observed with an increasing amount of water vapor added to the gas mixture, and deposition rates above 500 Å/min are obtained. The chemical purity and electrical conductivity of the copper deposit are as high in the case of a helium carrier gas as in the case of a hydrogen carrier gas. Implications for the mechanism of copper LPCVD are discussed.
Structure of S-passivated InP(100)-(1×1) surface
Authors: Lu Z. H. , Graham M. J. , Feng X. H. , Yang B. X.
Published: July 2002

X-ray absorption near-edge structure (XANES) is used to determine the structure of the S-passivated InP(100)-(1×1) surface. From photon electric polarization-dependent XANES studies, we found that S forms a bridge bond with two In atoms along the [011] direction, with an In-S-In bond angle of 100°. The atomic position of S is found to be close to the tetrahedral site of a phosphorous vacancy.
Light emitting charge injection transistor with p-type collector
Authors: Mastrapasqua Marco , Capasso Federico , Luryi Serge , Hutchinson Albert L. , Sivco Deborah L. , Cho Alfred Y.
Published: July 2002

We report the first realization of a charge injection transistor with a complementary collector. The device is implemented using InGaAs/InAlAs/InGaAs heterostructure material grown by molecular beam epitaxy. Real space transfer of hot electrons into the p-type collector leads to a luminescence signal arising from the recombination of the injected electrons with holes in the collector active region. The observed on/off ratio in the emitted light power is more than 104 and obeys an exclusive OR function of input voltages. The estimated internal quantum efficiency is as high as 90%.
Giant magnetoresistance dependence on Ar acceleration voltage in Co9Fe/Cu and Co3Fe/Cu multilayers
Authors: Saito Y. , Hashimoto S. , Inomata K.
Published: July 2002

In relation to theoretical predictions on the importance of randomness at the interface to determine the cause for giant magnetoresistance, argon acceleration voltage (VB) in ion beam sputtering was changed for preparing a set of CoxFe1−x/Cu multilayers. We found that the magnetoresistance as quite sensitive to the argon acceleration voltage and had a maximum around VB=600 V. Perfect antiferromagnetic coupling of the CoxFe1−x layers via thin Cu layers and the oscillation behavior of this indirect exchange coupling with a 12 Å period were observed for VB=600 V. These results suggest the importance of the interface state for giant magnetoresistance in multilayers. We also found that a small saturation field can be induced, which can be explained by the metamagnetic transition associating the relation of Ku≳J/tCoFe.
Enhancement of photoluminescence intensity in InGaAs/AlxGa1−xAs quantum wells by hydrogenation
Authors: Lord S. M. , Roos G. , Pezeshki B. , Harris J. S. , Johnson N. M.
Published: July 2002

The effect of diffusion of monatomic hydrogen on photoluminescence (PL) in the InGaAs/AlGaAs system has been studied. A significant increase in 77 K PL integrated intensity for In0.2Ga0.8As/AlxGa1−xAs quantum wells grown by molecular beam epitaxy is observed after hydrogenation. A 50% increase is observed for InGaAs/GaAs and the effect increases as the Al concentration increases from 0% to 33%. For 33%, the increase is approximately a factor of 9. This enhancement of the PL may be ascribed to hydrogen passivation of defects at the heterointerface or within the layers.
Low-defect colorless Bi12SiO20 grown by hydrothermal techniques
Authors: Harris Meckie T. , Larkin John J. , Martin J. J.
Published: July 2002

Colorless single crystals of bismuth silicon oxide (BSO) have been grown using a pressure-balanced hydrothermal technique. The absorption shoulder which causes the yellow coloration observed in conventional BSO was completely missing in the hydrothermal material. The 10 K absorption edge was found to be 3.45 eV for the hydrothermal samples. Because of the absence of a low-temperature photochromic response and the observation of only very weak TSC peaks, it appears that the hydrothermal crystals represent near-intrinsic BSO. When a crystal was pulled from a melt of hydrothermal material, the yellow coloration returned.
Tl2Ba2CaCu2O8 films with very low microwave surface resistance up to 95 K
Authors: Holstein W. L. , Parisi L. A. , Wilker C. , Flippen R. B.
Published: July 2002

Very low surface resistance Tl2Ba2CaCu2O8 films of thickness 1.0 μm on (100) LaAlO3 were fabricated and characterized. The films are highly c-axis oriented (x-ray diffraction rocking curve full width half maximum of 0.68°) with good in-plane epitaxy with respect to the substrate. The Tc of the films was 107.6±0.5 K as measured by ac magnetic susceptibility. The surface resistance at 10 GHz was measured with the parallel plate resonator technique and found to be 23±5 μΩ at 4.2 K, 130±20 μΩ at 77 K, and 300±60 μΩ at 95 K. Using a 20 GHz TE011 end-wall replacement copper cavity, the surface resistance was found to be comparable to that of copper, about 18 mΩ, at 104±1 K. The surface resistance of the films is significantly lower than that of all films reported to date at temperatures above 70 K and only slightly higher than the best high-temperature superconductor films reported to date at 4.2 K.
Thermal effects on (100) CdZnTe substrates as studied by x-ray photoelectron spectroscopy and reflection high energy electron diffraction
Authors: Wu Y. S. , Becker C. R. , Waag A. , Bicknell-Tassius R. N. , Landwehr G.
Published: July 2002

The influence of different CdZnTe substrate treatments prior to II-VI molecular beam epitaxial growth on surface stoichiometry, oxygen, and carbon contamination has been studied using x-ray photoelectron spectroscopy and reflection high energy electron diffraction. Heating the substrate at 300 °C can eliminate oxygen contamination, but cannot completely remove carbon from the surface. Heating at higher temperatures decreases the carbon contamination only slightly, while increasing the Zn–Cd ratio on the surface considerably. The magnitude of the latter effect is surprising and is crucial when one is using lattice matched CdZnTe (Zn 4%) substrates.
Electromigraton activation energy dependence on AlCu interconnect linewidth and microstructure
Authors: Dreyer M. L. , Varker C. J.
Published: July 2002

Al 1.5% Cu interconnects with linewidths from 0.8 to 10 μm and median grain size of 3.0 μm were stressed at current densities from 2–3×106 A cm−2 and at film temperatures between 140 and 300 °C. The activation energy dependence of the linewidth and grain size distribution, along with evidence for electromigration damage at specific sites within the film grain structure provides support for a line segment model in which the mass transport mechanism is dependent on the microstructure of the film. The results suggest that the contribution of nongrain boundary diffusion mechanisms to mass transport is more significant than previously believed for lines having comparable grain size and linewidth dimensions. In the context of interconnect reliability in integrated circuits, the data indicates that interconnect design rules which are driven by reliability constraints must include the microstructural properties of the film for accurate assessment.
Epitaxial MgO buffer layers for YBa2Cu3O7−x thin film on GaAs
Authors: Chang L. D. , Tseng M. Z. , Hu E. L. , Fork D. K.
Published: July 2002

Epitaxial MgO thin films have been grown on GaAs using electron beam (e-beam) evaporation. X-ray diffraction indicates that the epitaxial relations are MgO[001]//GaAs[001] and MgO[110]//GaAs[110]. The rocking curve widths are less than 1.5°. The refractive index is 1.73 and the dielectric strength is in excess of 4×106 V/cm. The MgO epitaxial films were used as a buffer layer for the growth of in situ YBa2Cu3O7−x on GaAs. The room-temperature resistivity of this film is 450–530 μΩ cm and Tc (R=0) is 85–87 K. The critical current density at 77 K is 4–6.7×104 and 1–3.8×106 A/cm2 at 4.2 K, in zero applied field.
Epitaxial YBa2Cu3O7−δ on GaAs(001) using buffer layers
Authors: Fork D. K. , Nashimoto K. , Geballe T. H.
Published: July 2002

Epitaxy of YBa2Cu3O7−δ (YBCO) on GaAs substrates has been demonstrated using epitaxial buffer layers. Recently developed methods for growing epitaxial YBCO thin films on Si have been adapted to achieve similar results on GaAs. MgO thin films were grown epitaxially on GaAs at below 400 °C. This layer provides a suitable template for the growth of YBCO or YBCO on BaTiO3. All materials are deposited in situ by pulsed laser deposition in a single growth process. The in-plane crystallography of MgO on GaAs is [100] parallel to [100], accommodating a lattice mismatch of −25.5%. Zero resistance at temperatures as high as 87 K and transition widths as narrow as 1.5 K are reported. Critical current densities as high as 9×106 A/cm2 at 4.2 K and 1.5×105 A/cm2 at 77 K have been measured.
Influence of process parameters on the time-dependent dielectric breakdown of rapid thermally nitrided and reoxidized nitrided thin SiO2
Authors: Joshi A. B. , Kwong D. L. , Lee S.
Published: July 2002

We report the impact of rapid thermal nitridation (RTN) and subsequent reoxidation (RTO) on the time-dependent dielectric breakdown of thin-gate oxides. The effect of RTN and RTO conditions on intrinsic and defect-related dielectric breakdown is investigated. These breakdown characteristics are correlated with compositional changes in the oxide during RTN and RTO. An optimal RTN/RTO gate oxide with higher charge-to-breakdown and lower defect density than pure SiO2 is reported.
Observations of new misfit dislocation configurations and slip systems at ultrahigh stresses in the (Al)GaAs/InxGa1−xAs/GaAs(100) system
Authors: Bonar J. M. , Hull R. , Walker J. F. , Malik R.
Published: July 2002

We have observed new misfit dislocation configurations and slip systems in (Al)GaAs/InxGa1−xAs/GaAs(100) heterostructures for x≥0.4. Dislocations are observed running along 〈001〉 directions in the interface, which are inconsistent with conventional glide of misfit dislocations on {111} planes in the zincblende lattice. Diffraction contrast analysis in a transmission electron microscope (TEM) shows that these dislocations are of the edge type with b=a/2〈011〉, inclined at 45° to the interface. In situ TEM heating experiments reveal dislocation propagation velocities ∼tens of μm s−1 at 600 °C, suggesting that they are moving by glide, rather than climb. The only slip planes consistent with these observations are {101} planes inclined to the interface. This represents a new relaxation mechanism in highly strained semiconductor heterostructures.
Relative fluorine concentrations in radio frequency/electron cyclotron resonance hybrid glow discharges
Authors: Passow M. L. , Pender J. T. P. , Brake M. L. , Sung K. T. , Liu Y. , Pang S. W. , Elta M. E.
Published: July 2002

The relative concentration of atomic fluorine was measured in a radio frequency (rf) glow discharge and a modified electron cyclotron resonance microwave/rf hybrid discharge in CF4 using an actinometric technique. The dependence of fluorine concentration on rf and microwave power, pressure, flow, and excitation source are presented. Anomalous behavior with rf power at constant microwave power was observed when using the Ar 750-nm line as the actinometric species.
Growth studies on Si0.8Ge0.2 channel two-dimensional hole gases
Authors: Smith D. W. , Emeleus C. J. , Kubiak R. A. , Parker E. H. C. , Whall T. E.
Published: July 2002

We report a study of the influences of MBE conditions on the low-temperature mobilities of Si/Si0.8Ge0.2 2DHG structures. A significant dependence of 2DHG mobility on growth temperature is observed with the maximum mobility of 3640 cm2 V−1 s−1 at 5.4 K being achieved at the relatively high-growth temperature of 640 °C. This dependence is associated with a reduction in interface charge density. Studies on lower mobility samples show that Cu contamination can be reduced both by growth interruptions and by modifications to the Ge source; this reduction produces improvements in the low-temperature mobilities. We suggest that interface charge deriving from residual metal contamination is currently limiting the 4-K mobility.
Tri-isopropyl gallium: A very promising precursor for chemical beam epitaxy
Authors: Lane P. A. , Martin T. , Freer R. W. , Calcott P. D. J. , Whitehouse C. R. , Jones A. C. , Rushworth S.
Published: July 2002

The first reported use of tri-isopropyl gallium (TiPGa) in chemical beam epitaxy (CBE) is described. Hall measurements performed on the resulting undoped GaAs epitaxial layers indicate an order of magnitude reduction in unintentional carbon impurity levels compared to structures grown under comparable conditions using the standard CBE precursor, triethyl gallium. 2 K photoluminescence spectra match those recorded elsewhere from state-of-the-art high purity GaAs material grown by molecular beam epitaxy, and 77 K Hall measurements on intentionally n-type doped GaAs layers confirm residual acceptor levels in the low 1014 cm−3 range. The early data obtained already provide a clear indication of the important potential of TiPGa as an improved precursor for the CBE growth of Ga-containing III–V materials.
Dopant-induced disordering of annealed AlGaAs heterostructures
Authors: Reynolds C. L. , Geva M.
Published: July 2002

Impurity-induced layer disordering, i.e., outdiffusion of dopant and matrix elements, has been observed in superlattices and quantum wells. In this letter, we report on disordering in AlGaAs heterostructures in which only the central region of 650-Å-thick AlGaAs layers is Si doped. Disordering is clearly shown to be dependent on Si concentration and outdiffusion.
Reflection high-energy electron diffraction study of the GaAs:Si:GaAs system
Authors: Fahy M. R. , Ashwin M. J. , Harris J. J. , Newman R. C. , Joyce B. A.
Published: July 2002

Surface structures occurring as a function of coverage during the deposition of Si on GaAs (001) and the further changes brought about by subsequent GaAs overgrowth using molecular beam epitaxy (MBE) have been studied with reflection high-energy electron diffraction (RHEED). Deposition of Si in the presence of an As4 flux causes the surface reconstruction to change systematically from 2×4 to symmetric 3×1 via an asymmetric 3×1 stage. The process is reversed during the overgrowth of GaAs. The change in surface periodicity in the [110] direction from two-fold to three-fold is explained by a superpositioning model. The implications of this for the growth and incorporation mechanisms of Si on GaAs are discussed.
Electron optical properties of nanometer field emission electron sources
Authors: Qian W. , Scheinfein M. R. , Spence J. C. H.
Published: July 2002

Electron optical properties of nanometer diameter field emission electron sources have been calculated using ray tracing methods. The spherical and chromatic aberration coefficients referred to the object plane were found to be on the order of angstroms. The effective source size was estimated to be much smaller than that in a conventional field emission source. The ultimate resolution of a lensless point projection electron microscope, which depends on both the source aberrations and the effective source size, were also in the order of angstroms. The beam angular half-width on the anode was 7.4° relative to the virtual image position on the optic axis, and the corresponding coherence width was 9.6°, suggesting that the source is totally coherent.
Epitaxial growth of single-crystal Ca1−xSrxCuO2 thin films by pulsed-laser deposition
Authors: Norton D. P. , Chakoumakos B. C. , Budai J. D. , Lowndes D. H.
Published: July 2002

Single-crystal thin films of Ca1−xSrxCuO2, the ‘‘infinite layer’’ parent compound for the high temperature superconductors, have been grown by pulsed-laser deposition over the composition range 0.15≤x≤1.0 utilizing a single-target codeposition growth scheme. Four-circle x-ray diffractometry reveals that these Ca1−xSrxCuO2 thin films are very high-quality single crystals of the tetragonal, infinite layer phase with extremely narrow diffraction peaks, complete in-plane crystalline alignment with the (100) SrTiO3 substrate, and virtually no impurity phases present. A systematic expansion of the c-axis lattice constant is observed as the Sr content is increased. Four-point transport measurements show that these single-crystal Ca1−xSrxCuO2 films are semiconducting, with room temperature resistivities on the order of an ohm-cm. These results demonstrate that this metastable compound can be epitaxially stabilized over a wide range of composition.
Ruderman–Kittel–Kasuya–Yosida interaction between zero-dimensional and one-dimensional ferromagnetic inclusions in a matrix of nonmagnetic metal
Authors: Genkin G. M. , Sapozhnikov M. V.
Published: July 2002

Work is devoted to the calculation of Ruderman–Kittel–Kasuya–Yosida interaction between inclusions of spherical shape (zero-dimensional) and whiskerical shape (one-dimensional). The conservation of oscillating character of the interaction independently of ferromagnetic particle sizes is shown.
Application of superlattices to the investigation of resonant defect in GaAs layers
Authors: Feng S. L. , Zhou J. , Lu L. W.
Published: July 2002

A resonant electron irradiation-induced deep level SE0 in GaAs layers has been investigated by using 50–50 Å uniformly Si-doped GaAs-Ga0.7Al0.3As superlattices and characterized by deep level transient spectroscopy. The formation of a miniband in superlattices changes the forbidden band gap and allows some resonant defects in bulk materials such as SE0 in GaAs to be detected. In these superlattices, three electron irradiation induced deep levels SE0, SE1, and SE2 located in GaAs layers have been observed. In bulk GaAs only two levels, E1 and E2, corresponding to SE1 and SE2 can be detected, since SE0 is a resonant level in bulk GaAs, situated 60 meV above the GaAs conduction band edge.
On the above supply voltage hot carrier distribution in semiconductor devices
Authors: Leung C. C. C. , Childs P. A.
Published: July 2002

In this letter we show that contrary to recent suggestions the hot carrier distribution at energies greater than the maximum available from the electric fields within a device does not take the form exp(−ε/kTL), where TL is the lattice temperature. The effective temperature is shown to be typically 1.35TL close to the supply energy, only approaching TL at energies well above that available from the electric field. Our results are obtained by solving the one-dimensional Boltzmann transport equation using a novel hybrid Monte Carlo/iterative technique.