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29 May 1989

Volume 54, Issue 22, pp. 2171-2277

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Strain variations in heteroepitaxial InP‐on‐Si grown by low‐pressure metalorganic chemical vapor deposition

D. S. Wuu, R. H. Horng, and M. K. Lee

Appl. Phys. Lett. 54, 2244 (1989); http://dx.doi.org/10.1063/1.101137 (3 pages) | Cited 8 times

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Variations in the magnitude and sign of the strain in epitaxial InP directly on (001) Si are studied as a function of layer thickness using photoluminescence and x‐ray diffraction techniques. The heteroepilayers were grown by low‐pressure metalorganic chemical vapor deposition and showed good quality. We find that biaxial compressive strains are still present in InP layers with thickness up to 0.8 μm. The magnitudes of compressive strains are much larger than those expected from the equilibrium theory. With increasing thickness above 1 μm, the InP/Si layers suffer biaxial tensile strains as a result of differential thermal contraction during the cooling process after growth.
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68.60.Bs Mechanical and acoustical properties
78.55.Cr III-V semiconductors
68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Novel photovoltaic δ‐doped GaAs superlattice structure

A. M. Glass, E. F. Schubert, B. A. Wilson, C. E. Bonner, J. E. Cunningham, D. H. Olson, and W. Jan

Appl. Phys. Lett. 54, 2247 (1989); http://dx.doi.org/10.1063/1.101138 (3 pages) | Cited 9 times

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An asymmetric δ‐doped GaAs structure is described which exhibits novel photovoltaic effects and low‐intensity nonlinear optics. Of particular interest in this kind of structure is the ability to design the electro‐optical and nonlinear optical properties and the material response time over a wide range by appropriate design of the doping profile.
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73.50.Pz Photoconduction and photovoltaic effects
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
85.60.-q Optoelectronic devices
73.61.Ey III-V semiconductors

AlAs/GaAs tunnel emitter bipolar transistor

A. F. J. Levi, R. N. Nottenburg, Y. K. Chen, and J. E. Cunningham

Appl. Phys. Lett. 54, 2250 (1989); http://dx.doi.org/10.1063/1.101139 (3 pages) | Cited 7 times

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We report the first microwave AlAs/GaAs tunnel emitter bipolar transistor utilizing nonequilibrium electron transport in the base. At an emitter current density of 1×105 A cm−2, current gain of greater than unity is measured up to a frequency of 40 GHz. dc current gains of 82 and 53 are measured for devices with emitter stripe widths of 9 and 1.5 μm, respectively. Enhanced device scaling is made possible with the extremely high velocity in the thin base region.
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85.30.Pq Bipolar transistors
73.40.Gk Tunneling
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Preparation and magnetic properties of Bi‐Pb‐Sr‐Ca‐Cu‐O superconducting ceramics

Takuya Uzumaki, Kazunori Yamanaka, Nobuo Kamehara, and Koichi Niwa

Appl. Phys. Lett. 54, 2253 (1989); http://dx.doi.org/10.1063/1.101140 (3 pages) | Cited 11 times

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A high Tc phase (Tc ≂110 K) in Bi‐Pb‐Sr‐Ca‐Cu‐O systems was synthesized by adding Ca2PbOx to the mixture of a low Tc phase (Tc ≂80 K) and a Bi‐Sr‐Cu‐O (Tc ≂10 K). X‐ray powder diffraction measurement suggests that the sintered bulk mainly consists of the high Tc phase. The volume fraction of the high Tc phase was 74% from the measurement of magnetization. The lower critical field Hc1 was 10 Oe at 77.3 K. The critical current density Jc of 3.0×102 A/cm2 was obtained for a repressed sample with a highly oriented microstructure.
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74.70.-b Superconducting materials other than cuprates
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
74.25.Sv Critical currents

Improvement of YBa2Cu3O7−x thick films by doping with silver

J. H. Miller, S. L. Holder, J. D. Hunn, and G. N. Holder

Appl. Phys. Lett. 54, 2256 (1989); http://dx.doi.org/10.1063/1.101518 (3 pages) | Cited 23 times

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Composite thick films of YBa2Cu3O7−x and silver have been prepared on alumina substrates using a paint‐on method. It is found that thick films containing greater than about 10% silver by weight have greatly reduced normal resistivities for T>Tc (onset) and significantly enhanced Tc (R=0) as compared with undoped films processed under identical conditions. These results are interpreted in terms of enhanced grain growth and an improved coupling between grain boundaries because of proximity‐induced electron pairing in the silver regions.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
61.72.up Other materials

Noise and hysteresis in flux‐locked TlBaCaCuO SQUIDs

V. Foglietti, R. H. Koch, W. J. Gallagher, B. Oh, B. Bumble, and W. Y. Lee

Appl. Phys. Lett. 54, 2259 (1989); http://dx.doi.org/10.1063/1.101141 (3 pages) | Cited 24 times

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Measurements of TlBaCaCuO‐based dc superconducting quantum interference devices (SQUIDs) performed using a practical feedback circuit gave a flat frequency response and an energy sensitivity of 6×10−30 J/Hz at 5 kHz and 77 K with an 80 pH SQUID. Flux‐locked loop operation was demonstrated to be strongly effective in eliminating the magnetic field hysteresis of the SQUID. The SQUIDs were operated in the flux‐locked loop at temperatures over 90 K and the 1/f noise was found to decrease with increasing temperature near 77 K.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.70.-b Superconducting materials other than cuprates
74.40.-n Fluctuation phenomena

Reactivity of Bi‐Sr‐Ca‐Cu‐O superconductor surface with indium studied by photoelectron spectroscopy

Pramada Kulkarni, Shailaja Mahamuni, Madhavi Chandrachood, I. S. Mulla, Arun S. Nigavekar, A. P. B. Sinha, and S. K. Kulkarni

Appl. Phys. Lett. 54, 2262 (1989); http://dx.doi.org/10.1063/1.101564 (3 pages) | Cited 4 times

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Interfacial interaction between Bi2Sr2CaCu2O8+δ high Tc superconductor and indium metal has been investigated using photoemission measurements. The results indicate that a sharp interface is possible and the interfacial interaction is restricted to a region of ∼5 Å thickness. In this region, there is a substantial CuO and SrO bond breaking.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
74.70.-b Superconducting materials other than cuprates
79.60.-i Photoemission and photoelectron spectra
68.35.B- Structure of clean surfaces (and surface reconstruction)

Propagation of terahertz bandwidth electrical pulses on YBa2Cu3O7−δ transmission lines on lanthanum aluminate

Martin C. Nuss, P. M. Mankiewich, R. E. Howard, B. L. Straughn, T. E. Harvey, C. D. Brandle, G. W. Berkstresser, K. W. Goossen, and P. R. Smith

Appl. Phys. Lett. 54, 2265 (1989); http://dx.doi.org/10.1063/1.101519 (3 pages) | Cited 24 times

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We study the propagation of terahertz bandwidth electrical pulses on high critical current density c‐axis oriented YBa2Cu3O7−δ (YBCO) coplanar transmission lines deposited epitaxially on the low dielectric loss substrate lanthanum aluminate (LaAlO3). The losses on the YBCO transmission line are lower than on an equivalent gold line on the same substrate at temperatures below 50 K. At higher temperatures, absorption and dispersion of the ultrashort electrical pulses are observed in reasonable agreement with Mattis–Bardeen theory.
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85.25.Qc Superconducting surface acoustic wave devices and other superconducting devices
84.40.Az Waveguides, transmission lines, striplines
74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates

Transition range viscosity of rapidly quenched Bi‐Ca‐Sr‐Cu‐O glasses

M. Tatsumisago, C. A. Angell, S. Tsuboi, Y. Akamatsu, N. Tohge, and T. Minami

Appl. Phys. Lett. 54, 2268 (1989); http://dx.doi.org/10.1063/1.101565 (3 pages) | Cited 11 times

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As a precursor of high Tc superconductors, glasses in the system BixCaSrCu2Ow (x=1.5,2.7) have been prepared using twin‐roller and metal‐plate quenching procedures. Transition range viscosities have been measured on samples as thin as 0.02 mm using the beam‐bending method with a technical modification. From the viscosity data, the system Bi‐Ca‐Sr‐Cu‐O can be characterized as a ‘‘fragile’’ liquid like the ZrF4‐based fluorides. The possibility of drawing fibers of high Tc superconductor precursors is discussed on the basis of the temperature dependence of viscosity.
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74.81.Bd Granular, melt-textured, amorphous, and composite superconductors
74.70.-b Superconducting materials other than cuprates
61.43.Fs Glasses
61.43.-j Disordered solids
81.20.-n Methods of materials synthesis and materials processing

In situ processing of epitaxial Y‐Ba‐Cu‐O high Tc superconducting films on (100) SrTiO3 and (100) YS‐ZrO2 substrates at 500–650 °C

R. K. Singh, J. Narayan, A. K. Singh, and J. Krishnaswamy

Appl. Phys. Lett. 54, 2271 (1989); http://dx.doi.org/10.1063/1.101520 (3 pages) | Cited 105 times

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We report the formation of excellent quality epitaxial YBa2Cu3O7 films on (100) SrTiO3 and (100) ZrO2 (yttria stabilized) substrates in the temperature range of 500–650 °C by XECl excimer laser ablation in a 0.2 Torr oxygen ambient. By applying a dc bias voltage of +300 V to an interposing ring, we were able to reduce the substrate temperatures from 650 to 500 °C for obtaining epitaxial films. The quality of the epitaxial films was found to decrease with temperature, particularly below 550 °C. The thickness of the superconducting films was varied from 500 to 5000 Å with superconducting transition temperatures Tc (zero resistance) varying from 87 to 90 K for 650 °C deposits. The critical current density Jc of films was found to vary linearly with temperature with values of (zero magnetic field at 77 K) 5.0×106 and 1.0×106 for films deposited at 650 °C on (100) SrTiO3 and (100) yttria‐stabilized zirconia substrates, respectively. X‐ray diffraction, transmission electron microscopy, electron channeling patterns, and Rutherford backscattering (RBS)/channeling showed excellent epitaxial quality of films on both substrates with best values of minimum ion channeling yield of 3.5% on (100) SrTiO3 substrates.
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74.78.-w Superconducting films and low-dimensional structures
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.-a Thin film structure and morphology
74.70.-b Superconducting materials other than cuprates

Time‐dependent self‐focusing and a 20 ps delay in laser ablation of polymers

Hackjin Kim, Jay C. Postlewaite, Taehyoung Zyung, and Dana D. Dlott

Appl. Phys. Lett. 54, 2274 (1989); http://dx.doi.org/10.1063/1.101521 (3 pages) | Cited 15 times

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Laser surface ablation of polymethylmethacrylate by ultrafast 0.532 μm pulses is studied using an imaging apparatus with 2 ps resolution. Coherent two‐photon absorption rapidly heats the sample, inducing explosive thermal decomposition. Electron microscopy is used to characterize the damaged surface. Ultrafast imaging shows that surface damage is accompanied by the production of a transient optical filament. The intensity dependence shows that self‐focusing results from an accumulative, rather than instantaneous, relaxation of the transient refractive index. At all intensities, there is a 20 ps delay before ablation commences.
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79.20.Ds Laser-beam impact phenomena
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.30.Va Image forming and processing
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Addendum: Band offsets for pseudomorphic InP/GaAs [Appl. Phys. Lett. 54, 259 (1989)]

David Nolte

Appl. Phys. Lett. 54, 2277 (1989); http://dx.doi.org/10.1063/1.101102 (1 page)

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Abstract Unavailable
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73.20.At Surface states, band structure, electron density of states
71.20.Nr Semiconductor compounds
71.20.Ps Other inorganic compounds
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
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Addendum: Direct test of a model of efficient second‐harmonic generation in glass optical fibers [Appl. Phys. Lett. 53, 557 (1988)]

Victor Mizrahi, U. Österberg, C. Krautschik, G. I. Stegeman, J. E. Sipe, and T. F. Morse

Appl. Phys. Lett. 54, 2277 (1989); http://dx.doi.org/10.1063/1.101103 (1 page)

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Abstract Unavailable
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.81.Gs Birefringence, polarization
42.70.Ce Glasses, quartz
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