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13 Mar 2000

Volume 76, Issue 11, pp. 1353-1479

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Comparison of spontaneous and piezoelectric polarization in GaN/Al0.65Ga0.35N multi-quantum-well structures

R. A. Hogg, C. E. Norman, A. J. Shields, M. Pepper, and N. Iizuka

Appl. Phys. Lett. 76, 1428 (2000); http://dx.doi.org/10.1063/1.126053 (3 pages) | Cited 14 times

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We report a luminescence study of GaN/Al0.65Ga0.35N multi-quantum-well structures. The surface of the samples exhibits microcracking allowing the same quantum well to be measured under two different strain conditions. We can accurately describe the emission energies in the two strain conditions by considering piezoelectric polarization alone in contrast to the theoretical prediction that spontaneous polarization effects should dominate. © 2000 American Institute of Physics.
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78.60.Hk Cathodoluminescence, ionoluminescence
77.65.Ly Strain-induced piezoelectric fields
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
78.66.Fd III-V semiconductors
73.61.Ey III-V semiconductors

Thermally activated electrical conductivity in thin GaN epitaxial films

J. Salzman, C. Uzan-Saguy, R. Kalish, V. Richter, and B. Meyler

Appl. Phys. Lett. 76, 1431 (2000); http://dx.doi.org/10.1063/1.126054 (3 pages) | Cited 14 times

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Temperature-dependent Hall measurements of thin GaN films subjected to He ion irradiation at ever increasing doses are used to study the electron transport in GaN. It is shown that electron transport is a thermally activated process with activation energies gradually increasing with reciprocal net carrier concentration, until a saturated value of the activation energy is reached. These experiments provide a direct verification that conductivity in thin GaN layers is controlled by potential barriers caused by depletion of carriers at grain boundaries in the material. Values of average grain size, density of surface states at the grain boundaries, and their energetics are extracted from the experiment. © 2000 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.20.At Surface states, band structure, electron density of states
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
61.72.Mm Grain and twin boundaries

Transient enhanced diffusion of implanted boron in 4H-silicon carbide

M. S. Janson, M. K. Linnarsson, A. Hallén, B. G. Svensson, N. Nordell, and H. Bleichner

Appl. Phys. Lett. 76, 1434 (2000); http://dx.doi.org/10.1063/1.126055 (3 pages) | Cited 23 times

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Experimental evidence is given for transient enhanced diffusion of boron (B) in ion-implanted silicon carbide (SiC). The implanted B is diffusing several μm into the samples when annealed at 1600 and 1700 °C for 10 min, but the in-diffused tails remain unaffected when the annealing times are increased to 30 min at the same temperatures. A lower limit of the effective B diffusivity at 1600 °C is determined to 7×10−12 cm2/s, which is 160 times larger than the equilibrium B diffusivity given in the literature. © 2000 American Institute of Physics.
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61.72.up Other materials
66.30.J- Diffusion of impurities
61.82.Fk Semiconductors

Imaging and local current transport measurements of AlInP quantum dots grown on GaP

C. V. Reddy, V. Narayanamurti, J. H. Ryou, U. Chowdhury, and R. D. Dupuis

Appl. Phys. Lett. 76, 1437 (2000); http://dx.doi.org/10.1063/1.126056 (3 pages) | Cited 6 times

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Individual AlInP self-assembled quantum dots grown on a (100) GaP substrate are imaged and probed using ballistic electron emission microscopy (BEEM). The excellent nanometer scale lateral resolution of BEEM is utilized to inject carriers directly into a single quantum dot, and thus, current transport through the dot investigated without any direct electrical contact. The BEEM spectra taken on and off the dot revealed a local conduction-band offset between GaP and AlInP with a barrier height of ΔEc ∼ 0.13±0.01 eV. © 2000 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

The use of a surfactant (Sb) to induce triple period ordering in GaInP

C. M. Fetzer, R. T. Lee, J. K. Shurtleff, G. B. Stringfellow, S. M. Lee, and T. Y. Seong

Appl. Phys. Lett. 76, 1440 (2000); http://dx.doi.org/10.1063/1.126057 (3 pages) | Cited 17 times

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A surfactant is used to induce an ordered structure in an epitaxial layer. The addition of small amounts of triethylantimony during the organometallic vapor phase epitaxy growth of GaInP on (001) GaAs substrates is shown to remove CuPt ordering with a resultant increase in band gap energy. Increasing the concentration of Sb in the vapor beyond a critical Sb to P ratio [Sb/P(v)] of 4×10−4 gives a reversal of this behavior. The band gap energy is observed to decrease by 50 meV at a concentration of Sb/P(v) = 1.6×10−3, coincident with the formation of an ordered phase with a period triple the normal lattice spacing along the [111] and [mathmath1] directions. The formation of this new ordered structure is believed to be related to high concentrations of Sb on the surface, which leads to a change in the surface reconstruction from (2×4)-like to (2×3)-like, as indicated by surface photoabsorption performed in situ. © 2000 American Institute of Physics.
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68.35.Rh Phase transitions and critical phenomena
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
71.20.Ps Other inorganic compounds

BGaInAs alloys lattice matched to GaAs

J. F. Geisz, D. J. Friedman, J. M. Olson, Sarah R. Kurtz, R. C. Reedy, A. B. Swartzlander, B. M. Keyes, and A. G. Norman

Appl. Phys. Lett. 76, 1443 (2000); http://dx.doi.org/10.1063/1.126058 (3 pages) | Cited 28 times

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We report the epitaxial growth of zinc-blende BxGa1−x−yInyAs and BxGa1−xAs on GaAs substrates with boron concentrations (x) up to 2%–4% by atmospheric-pressure metalorganic chemical vapor deposition. The band gap of BxGa1−xAs increases by only 4–8 meV/%B with increasing boron concentration in this concentration range. We demonstrate an epitaxial BxGa1−x−yInyAs layer deposited on GaAs with a band gap of 1.34 eV that is significantly less strained than a corresponding Ga1−yInyAs layer with the same band gap. © 2000 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.20.At Surface states, band structure, electron density of states
68.55.-a Thin film structure and morphology
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Two-stage superconducting-quantum-interference-device amplifier in a high-Q gravitational wave transducer

Gregory M. Harry, Insik Jin, Ho Jung Paik, Thomas R. Stevenson, and Frederick C. Wellstood

Appl. Phys. Lett. 76, 1446 (2000); http://dx.doi.org/10.1063/1.126059 (3 pages) | Cited 15 times

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We report on the total noise from an inductive motion transducer for a gravitational-wave antenna. The transducer uses a two-stage superconducting quantum interference device (SQUID) amplifier and has a noise temperature of 1.1 mK, of which 0.70 mK is due to back action noise from the SQUID chip. The total noise includes thermal noise from the transducer mass, which has a measured Q of 2.60×106. The noise temperature exceeds the expected value of 3.5 μK by a factor of 200, primarily due to voltage noise at the input of the SQUID. Noise from flux trapped on the chip is found to be the most likely cause. © 2000 American Institute of Physics.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
04.80.Nn Gravitational wave detectors and experiments
95.55.Ym Gravitational radiation detectors; mass spectrometers; and other instrumentation and techniques
84.30.Le Amplifiers
84.40.Ba Antennas: theory, components and accessories

DyFe2(110) nanostructures: Morphology and magnetic anisotropy

A. Mougin, C. Dufour, K. Dumesnil, N. Maloufi, and Ph. Mangin

Appl. Phys. Lett. 76, 1449 (2000); http://dx.doi.org/10.1063/1.126060 (3 pages) | Cited 1 time

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Single-crystalline DyFe2(110) nanosystems have been obtained by molecular-beam epitaxy. From reflection high-energy electron diffraction observations, the systems have been shown to grow in a Stranski–Krastanov mode. Depending on elaboration conditions (substrate temperature and nominal thickness), dots with anisotropic shape or continuous films with low surface roughness are obtained. Compared to the bulk compounds, the epitaxial systems are strained because of thermal differential contraction and exhibit modifications of easy-magnetization direction compared to bulk. The magnetization reversal process is correlated to the morphology of the layers. © 2000 American Institute of Physics.
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68.55.-a Thin film structure and morphology
75.70.Ak Magnetic properties of monolayers and thin films
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)
75.50.Kj Amorphous and quasicrystalline magnetic materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy

Anisotropic magnetic susceptibility of multiwalled carbon nanotubes

F. Tsui, L. Jin, and O. Zhou

Appl. Phys. Lett. 76, 1452 (2000); http://dx.doi.org/10.1063/1.126061 (3 pages) | Cited 19 times

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Magnetic susceptibility of partially aligned multiwalled carbon nanotubes has been studied using superconducting quantum interference device magnetometry. Partial alignment of multiwalled nanotubes was produced by uniaxially straining composites of carbon nanotubes embedded in polymer matrices. The degree of alignment was determined by x-ray diffraction. The observed magnetic response is diamagnetic and anisotropic with the component along the nanotubes less diamagnetic than that of the perpendicular. The observed anisotropy is consistent with theoretical predictions, but it contradicts earlier experimental findings. © 2000 American Institute of Physics.
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75.20.Ck Nonmetals
61.48.-c Structure of fullerenes and related hollow and planar molecular structures

Chemical ordering of epitaxial FePd deposited on ZnSe and the surfactant effect of segregated Se

C. Bourgognon, S. Tatarenko, J. Cibert, L. Carbonell, V. H. Etgens, M. Eddrief, B. Gilles, A. Marty, and Y. Samson

Appl. Phys. Lett. 76, 1455 (2000); http://dx.doi.org/10.1063/1.126062 (3 pages) | Cited 7 times

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We describe the experimental conditions under which a thin film (500 Å thick) of the ferromagnetic alloy FePd can be grown epitaxially onto a thin (100 nm thick) ZnSe(001) layer on a GaAs(001) substrate. A two-dimensional growth could be achieved by using a Pt seeding layer inserted between FePd and ZnSe. During the growth of the metallic layers, the segregation of Se atoms at the surface involves a dramatic effect on the formation of the uniaxial L10 FePd ordered phase. As a result, no perpendicular magnetic anisotropy was observed. The removal of the Se atoms from the Pt surface by a gentle ion bombardment, enables the growth of a FePd layer exhibiting a large anisotropy constant of about 1.2×107 erg/cm3 along the growth direction with a marked perpendicular magnetic domain configuration. © 2000 American Institute of Physics.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.50.Bb Fe and its alloys
68.55.-a Thin film structure and morphology
68.35.Fx Diffusion; interface formation
75.30.Gw Magnetic anisotropy
75.60.Ch Domain walls and domain structure
61.82.Bg Metals and alloys
61.80.Jh Ion radiation effects
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Integration of Pb(Zr0.52Ti0.48)O3 epilayers with Si by domain epitaxy

A. K. Sharma, J. Narayan, C. Jin, A. Kvit, S. Chattopadhyay, and C. Lee

Appl. Phys. Lett. 76, 1458 (2000); http://dx.doi.org/10.1063/1.126063 (3 pages) | Cited 17 times

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High-quality lead zirconate titanate films (PZT) have been grown on yttrium barium copper oxide (YBCO) bottom electrode by domain epitaxy where integral multiples of lattice constants match across the interface. The YBCO films were epitaxially fabricated on Si (100) by introducing epilayer geometry of strontium titanate/magnesium oxide/titanium nitride. Pulsed-laser ablation was used to evaporate these five stoichiometric targets in a high vacuum chamber. X-ray diffraction and high-resolution transmission electron microscopy techniques were employed to gain understanding of the structure, crystallinity, and interfaces in these epilayers. The electrical characterization of the PZT films with evaporated silver contacts resulted in superior values of spontaneous polarization, remnant polarization, and coercive fields. This heterostructure opens a way for integration of epitaxial single-crystal PZT-based capacitors with silicon-based devices. © 2000 American Institute of Physics.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
84.32.Tt Capacitors
77.80.-e Ferroelectricity and antiferroelectricity
68.55.-a Thin film structure and morphology
77.22.Ej Polarization and depolarization
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Strain-induced second-harmonic generation in pseudocubic Ba0.48Sr0.52TiO3 thin films

U. C. Oh, Jing Ma, G. K. L. Wong, J. B. Ketterson, and Jung Ho Je

Appl. Phys. Lett. 76, 1461 (2000); http://dx.doi.org/10.1063/1.126064 (3 pages) | Cited 4 times

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We report the observation of a strong second-order nonlinear optical response from epitaxial Ba0.48Sr0.52TiO3 thin films grown on MgO(001) by magnetron sputtering. The result is unexpected since the crystal structure of Ba0.48Sr0.52TiO3 is centrosymmetric under ambient conditions. A second-order nonlinear susceptibility d33 as large as 11 pm/V at a fundamental wavelength of 1.064 μm is observed in a 300 Å thick film. By studying a series of films with different strains, induced by a film–substrate lattice mismatch, we conclude that the resulting tetragonal distortion, presumably accompanied by a loss of inversion symmetry, is responsible for the second-harmonic generation. © 2000 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.66.Nk Insulators
77.80.-e Ferroelectricity and antiferroelectricity
81.15.Cd Deposition by sputtering
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
42.65.An Optical susceptibility, hyperpolarizability
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Room-temperature operation of a memory-effect AlGaAs/GaAs heterojunction field-effect transistor with self-assembled InAs nanodots

K. Koike, K. Saitoh, S. Li, S. Sasa, M. Inoue, and M. Yano

Appl. Phys. Lett. 76, 1464 (2000); http://dx.doi.org/10.1063/1.126065 (3 pages) | Cited 24 times

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This letter describes the memory effect of an AlGaAs/GaAs heterojunction field-effect transistor that contains InAs nanodots in the barrier layer. The device experiences a shift of threshold gate voltage, as a function of the amount of the electrons trapped in the nanodots. These trapped electrons can be injected by applying a positive gate voltage and be erased by a visible light illumination at negative gate bias. Although the shift of the threshold gate voltage volatilizes with the time after the memory programing operation, a considerable part of the shift is retained even after 100 h at room temperature. © 2000 American Institute of Physics.
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85.30.Tv Field effect devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.61.Ey III-V semiconductors

Spin-dependent capacitance of silicon field-effect transistors

M. S. Brandt, R. T. Neuberger, and M. Stutzmann

Appl. Phys. Lett. 76, 1467 (2000); http://dx.doi.org/10.1063/1.126066 (3 pages) | Cited 3 times

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Under electron spin resonance conditions, changes of the capacitance of vertical field-effect transistors are observed, due to spin-dependent trapping of charge carriers by defects at the interface between the substrate and the channel region. The spectra obtained by capacitively detected magnetic resonance show the presence of two different defects, tentatively assigned to defects introduced by processing and complexes involving transition-metal impurities. Using a quantitative model, the number of defects resonantly charged by this trapping is estimated. It is shown that the possible cross talk of spin-dependent changes of the conductivity in the substrate is, in fact, suppressed by the large impedance of the space-charge layer. © 2000 American Institute of Physics.
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73.61.Cw Elemental semiconductors
85.30.Tv Field effect devices
76.30.Mi Color centers and other defects

Atomic resolution on Si(111)-(7×7) by noncontact atomic force microscopy with a force sensor based on a quartz tuning fork

Franz J. Giessibl

Appl. Phys. Lett. 76, 1470 (2000); http://dx.doi.org/10.1063/1.126067 (3 pages) | Cited 142 times

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Atomic resolution by noncontact atomic force microscopy with a self-sensing piezoelectric force sensor is presented. The sensor has a stiffness of 1800 N/m and is operated with sub-nanometer amplitudes, allowing atomic resolution with relatively bluntly etched tungsten tips. Sensitivity and noise are discussed. © 2000 American Institute of Physics.
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07.79.Lh Atomic force microscopes
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
68.35.B- Structure of clean surfaces (and surface reconstruction)
07.10.Pz Instruments for strain, force, and torque
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
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High-speed tapping mode imaging with active Q control for atomic force microscopy

T. Sulchek, R. Hsieh, J. D. Adams, G. G. Yaralioglu, S. C. Minne, C. F. Quate, J. P. Cleveland, A. Atalar, and D. M. Adderton

Appl. Phys. Lett. 76, 1473 (2000); http://dx.doi.org/10.1063/1.126071 (3 pages) | Cited 74 times

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The speed of tapping mode imaging with the atomic force microscope (AFM) has been increased by over an order of magnitude. The enhanced operation is achieved by (1) increasing the instrument’s mechanical bandwidth and (2) actively controlling the cantilever’s dynamics. The instrument’s mechanical bandwidth is increased by an order of magnitude by replacing the piezotube z-axis actuator with an integrated zinc oxide (ZnO) piezoelectric cantilever. The cantilever’s dynamics are optimized for high-speed operation by actively damping the quality factor (Q) of the cantilever. Active damping allows the amplitude of the oscillating cantilever to respond to topography changes more quickly. With these two advancements, 80μm×80 μm high-speed tapping mode images have been obtained with a scan frequency of 15 Hz. This corresponds to a tip velocity of 2.4 mm/s. © 2000 American Institute of Physics.
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07.79.Lh Atomic force microscopes
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Copper thin films used as transmission remoderators for slow positron beams

R. S. Brusa, W. Deng, R. Checchetto, G. P. Karwasz, and A. Zecca

Appl. Phys. Lett. 76, 1476 (2000); http://dx.doi.org/10.1063/1.126068 (3 pages) | Cited 3 times

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The positron remoderation efficiency of self-supported copper films 1000–5000 Å thick was measured by a slow positron beam at impinging positron energies between 1 and 20 keV. A maximum efficiency of 11.5 (−1+3)% was found. It has been shown that copper films are easily produced. A relatively low temperature annealing (≃450 °C) is needed to remoderate positrons. These properties make them good candidate for positron beams with brightness enhancement stage in transmission geometry. © 2000 American Institute of Physics.
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07.77.Ka Charged-particle beam sources and detectors
29.25.Bx Electron sources
41.75.Fr Electron and positron beams
29.27.Eg Beam handling; beam transport
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FREE

Erratum: “Nonlinear optical response of GaN layers on sapphire: The impact of fundamental beam interference” [Appl. Phys. Lett. 76, 810 (2000)]

I. V. Kravetsky, I. M. Tiginyanu, Ralf Hildebrandt, Gerd Marowsky, D. Pavlidis, A. Eisenbach, and H. L. Hartnagel

Appl. Phys. Lett. 76, 1479 (2000); http://dx.doi.org/10.1063/1.126069 (1 page)

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Abstract Unavailable
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
99.10.Cd Errata
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