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9 Jul 2001

Volume 79, Issue 2, pp. 145-277

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Destructive interference of freely propagating terahertz pulses and its potential for high-resolution spectroscopy and optical computing

V. Grebenev, E. Knoesel, and L. Bartels

Appl. Phys. Lett. 79, 145 (2001); http://dx.doi.org/10.1063/1.1381419 (3 pages) | Cited 1 time

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Freely propagating terahertz pulses have been superimposed on a detection crystal leading to their mutual annihilation. An extinction ratio as good as 10:1 is found. The interference pattern represents the sum of the pulses, as measured individually, with high fidelity. Its application for high-resolution spectroscopy and optical computing are discussed. © 2001 American Institute of Physics.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
41.20.Jb Electromagnetic wave propagation; radiowave propagation
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks

Effect of saturable response to two-photon absorption on the readout signal level of three-dimensional bit optical data storage in a photochromic polymer

Min Gu, Jose Omar Amistoso, Akiko Toriumi, Masahiro Irie, and Satoshi Kawata

Appl. Phys. Lett. 79, 148 (2001); http://dx.doi.org/10.1063/1.1383999 (3 pages) | Cited 6 times

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We observe a saturable change in the refractive index induced by two-photon absorption in a photochromic polymer, while the erasable nature of the polymer is maintained. As a result, the support region of spatial frequencies of the recorded data bits caused by the refractive index change in the polymer is enlarged. This feature leads to the significant enhancement of the signal level in a reflection confocal microscope readout system for three-dimensional photochromic bit optical data storage. © 2001 American Institute of Physics.
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42.70.Ln Holographic recording materials; optical storage media
42.79.Vb Optical storage systems, optical disks
42.70.Jk Polymers and organics
78.66.Qn Polymers; organic compounds
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
07.60.Pb Conventional optical microscopes
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Near-transform-limited picosecond pulses from a gain-switched InGaAs diode laser with fiber Bragg gratings

D. J. L. Birkin, E. U. Rafailov, W. Sibbett, L. Zhang, Y. Liu, and I. Bennion

Appl. Phys. Lett. 79, 151 (2001); http://dx.doi.org/10.1063/1.1381412 (2 pages) | Cited 6 times

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We have generated near-transform-limited picosecond pulses (ΔτΔν ≈ 0.45) from a gain-switched diode laser using periodic and chirped fiber Bragg gratings. This configuration reduced the spectral bandwidth from 11 to 0.08 nm and the pulse duration was reduced, from 30 to <18 ps. Average and peak powers of 27 and 770 mW, respectively, were obtained. © 2001 American Institute of Physics.
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42.60.Fc Modulation, tuning, and mode locking
42.55.Px Semiconductor lasers; laser diodes
42.55.Rz Doped-insulator lasers and other solid state lasers
42.79.Dj Gratings
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.81.Wg Other fiber-optical devices

Quantum dots in glass spherical microcavity

Rui Jia, De-Sheng Jiang, Ping-Heng Tan, and Bao-Quan Sun

Appl. Phys. Lett. 79, 153 (2001); http://dx.doi.org/10.1063/1.1380732 (3 pages) | Cited 16 times

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Glass spherical microcavities containing CdSexS1−x semiconductor quantum dots (QDs) are fabricated. The coupling between the optical emission of embedded CdSexS1−x QDs and spherical cavity modes is realized. When the luminescence of QDs is excited by a laser beam, the strong whispering gallery mode resonance with high Q factors is achieved in the photoluminescence spectra. © 2001 American Institute of Physics.
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78.67.Hc Quantum dots
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
81.07.Ta Quantum dots

Highly efficient phosphorescence from organic light-emitting devices with an exciton-block layer

Masamichi Ikai, Shizuo Tokito, Youichi Sakamoto, Toshiyasu Suzuki, and Yasunori Taga

Appl. Phys. Lett. 79, 156 (2001); http://dx.doi.org/10.1063/1.1385182 (3 pages) | Cited 412 times

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One of the keys to highly efficient phosphorescent emission in organic light-emitting devices is to confine triplet excitons generated within the emitting layer. We employ “starburst” perfluorinated phenylenes (C60F42) as a both hole- and exciton-block layer, and a hole-transport material 4,4′,4″-tri(N-carbazolyl) triphenylamine as a host for the phosphorescent dopant dye in the emitting layer. A maximum external quantum efficiency reaches to 19.2%, and keeps over 15% even at high current densities of 10–20 mA/cm2, providing several times the brightness of fluorescent tubes for lighting. The onset voltage of the electroluminescence is as low as 2.4 V and the peak power efficiency is 70–72 lm/W, promising for low-power display devices. © 2001 American Institute of Physics.
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73.61.Ph Polymers; organic compounds
78.66.Qn Polymers; organic compounds
78.55.Kz Solid organic materials
71.35.Cc Intrinsic properties of excitons; optical absorption spectra

Etching of crystalline Si in Cl2 atmosphere by means of an optical fiber tip

G. Wysocki, S. T. Dai, T. Brandstetter, J. Heitz, and D. Bäuerle

Appl. Phys. Lett. 79, 159 (2001); http://dx.doi.org/10.1063/1.1369415 (3 pages) | Cited 7 times

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We report experiments on laser-induced chemical etching of silicon in chlorine atmosphere using a near-field optical configuration. Crystalline (100) Si surfaces were locally illuminated in 300 mbar Cl2 through a tapered fiber tip. In most of the experiments, we used UV argon ion laser lines around 350 nm for illumination. The etched samples were analyzed by means of atomic force microscopy. Patterns with a width of 140 nm at full width half maximum and a vertical etch rate of the order of 15 nm/s have been achieved. Comparison of etching with a visible wavelength at intensities that cannot cause surface melting shows that the etching is primarily a photophysical process. © 2001 American Institute of Physics.
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81.05.Cy Elemental semiconductors
81.65.Cf Surface cleaning, etching, patterning

Optical characterization of 4H-SiC by far ultraviolet spectroscopic ellipsometry

Seung-Gu Lim, Thomas N. Jackson, W. C. Mitchel, R. Bertke, and J. L. Freeouf

Appl. Phys. Lett. 79, 162 (2001); http://dx.doi.org/10.1063/1.1384895 (3 pages) | Cited 1 time

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We have developed a far UV spectroscopic ellipsometer system working up to 9 eV, and applied it to the characterization of three 4H-SiC samples with different surface conditions [i.e., as-received and chemical mechanical processing (CMP) processed 4H-SiC bulk substrates and a 4H-SiC epi sample]. Pseudodielectric functions ε1 and ε2 clearly demonstrate the excellent surface sensitivity of the far UV ellipsometry system as it distinguishes the improvements provided by CMP process. Simulation results of ellipsometer data indicate the existence of a damaged subsurface layer in the as-received 4H-SiC bulk substrate. The investigation of sample surfaces using atomic force microscopy confirms the results of ellipsometry measurements. © 2001 American Institute of Physics.
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78.40.Ha Other nonmetallic inorganics
07.60.Fs Polarimeters and ellipsometers
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.65.Ps Polishing, grinding, surface finishing
81.05.Hd Other semiconductors

Coherent nonlinear propagation of ultrafast electric field transients through intersubband resonances

F. Eickemeyer, M. Woerner, A. M. Weiner, T. Elsaesser, R. Hey, and K. H. Ploog

Appl. Phys. Lett. 79, 165 (2001); http://dx.doi.org/10.1063/1.1384898 (3 pages) | Cited 9 times

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Amplitude and phase-controlled midinfrared field transients at a wavelength of 12.5 μm induce resonant intersubband excitations in n-type modulation-doped GaAs/AlGaAs quantum wells. The transmitted electric field transients are directly measured by ultrafast electro-optic sampling. Coherent control of intersubband excitations is demonstrated by applying two phase-locked pulses with variable relative phase. A coherent nonlinear response corresponding to partial Rabi flops of up to 60° in the Bloch sphere is observed with excitation pulses of only 1 pJ energy. © 2001 American Institute of Physics.
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78.67.De Quantum wells
73.21.Fg Quantum wells
78.47.-p Spectroscopy of solid state dynamics
78.20.Jq Electro-optical effects
78.30.Fs III-V and II-VI semiconductors
42.65.-k Nonlinear optics

Study of the thermo-optic effect in hydrogenated amorphous silicon and hydrogenated amorphous silicon carbide between 300 and 500 K at 1.55 μm

Francesco G. Della Corte, Maurizio Esposito Montefusco, Luigi Moretti, Ivo Rendina, and Alfredo Rubino

Appl. Phys. Lett. 79, 168 (2001); http://dx.doi.org/10.1063/1.1383056 (3 pages) | Cited 13 times

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The thermo-optic coefficients of hydrogenated amorphous silicon (a-Si:H) and hydrogenated amorphous silicon carbide (a-SiC:H)two of the main amorphous semiconductors in optoelectronics—have been measured and critically analyzed in the practical device operation temperature range 300–500 K, at the communication wavelength of 1.55 μm. The experimental data have been fitted using a single-oscillator model that takes into account the shape of the ϵ2 spectrum of the amorphous materials. In particular, for a-Si:H, the extracted parameters significantly extend, and are consistent with, the few data reported in the literature; an interesting analogy with crystalline silicon is also found and discussed. Complete results for a-SiC:H are finally reported. © 2001 American Institute of Physics.
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78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
81.05.Gc Amorphous semiconductors
81.05.Cy Elemental semiconductors
85.60.-q Optoelectronic devices
78.66.Db Elemental semiconductors and insulators
78.66.Jg Amorphous semiconductors; glasses

Enhanced performance of pulse driven small area polyfluorene light emitting diodes

C. I. Wilkinson, D. G. Lidzey, L. C. Palilis, R. B. Fletcher, S. J. Martin, X. H. Wang, and D. D. C. Bradley

Appl. Phys. Lett. 79, 171 (2001); http://dx.doi.org/10.1063/1.1383799 (3 pages) | Cited 33 times

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We have investigated the performance of conjugated polymer light emitting diodes (LEDs) as their active areas are reduced to dimensions typical for pixellated displays. We find that by reducing the active diameter of the device from our standard size (1.5×3 mm) to 50 μm, the current density that can be sustained before LED failure increases by a factor of 9. This increase in current density is mirrored by similar increases in maximum LED brightness. We propose that such effects occur due to improved thermal management in small area devices. Using pulsed driving schemes, devices with a diameter of 50 μm sustained current densities of 5.1 MA m−2, and have emitted electroluminescence with a brightness of 6.5 Mcd m−2. © 2001 American Institute of Physics.
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85.60.Jb Light-emitting devices
42.70.Jk Polymers and organics
78.60.Fi Electroluminescence

Efficient electron injection in blue-emitting polymer light-emitting diodes with LiF/Ca/Al cathodes

T. M. Brown, R. H. Friend, I. S. Millard, D. J. Lacey, J. H. Burroughes, and F. Cacialli

Appl. Phys. Lett. 79, 174 (2001); http://dx.doi.org/10.1063/1.1383800 (3 pages) | Cited 85 times

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We report electroabsorption and electroluminescence investigations of polymer light-emitting diodes featuring a LiF/Ca/Al cathode, for efficient electron injection into the electroluminescent polymer layer. Our measurement of the built-in potential gives direct evidence of a sizeable reduction of the cathodic barrier height not only with respect to Ca, but also versus LiF/Al or CsF/Al bilayer cathodes, currently amongst the most efficient electron injectors for low electron affinity polymers. In blue-emitting (∼2.7 at peak) polyfluorene-based LEDs, with poly(ethylenedioxythiophene)/poly(styrene sulphonic acid) anodes and LiF/Ca/Al cathodes, we measure a built-in potential of 2.7 V, a luminance of ∼1600 cd/m2 (the highest among the devices studied here) at a driving voltage of 5 V, and efficiencies as high as ∼3 lm/W. We also find that the turn-on voltage essentially coincides with the built-in potential within the experimental error. © 2001 American Institute of Physics.
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78.66.Qn Polymers; organic compounds
73.61.Ph Polymers; organic compounds
85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
78.20.Jq Electro-optical effects
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Overcritical density plasma diagnosis inside laser-produced craters

O. Renner, E. Krouský, F. B. Rosmej, P. Sondhauss, I. Uschmann, E. Förster, M. P. Kalachnikov, and P. V. Nickles

Appl. Phys. Lett. 79, 177 (2001); http://dx.doi.org/10.1063/1.1381413 (3 pages) | Cited 4 times

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Spatially resolved x-ray spectra of the Al Lyman α group emitted from the surface of the laser- irradiated targets display plasma regions where the resonance line is suppressed and the dielectronic satellites dominate. Calculations based on multilevel collisional-radiative code and two-dimensional hydrodynamic simulations relate this spectral distribution to a presence of the cold overcritical density plasma inside the crater at the target surface. © 2001 American Institute of Physics.
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52.70.La X-ray and γ-ray measurements
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.65.-y Plasma simulation
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Modeling multilayer woven fabrics

J. A. Åström, J. P. Mäkinen, and J. Timonen

Appl. Phys. Lett. 79, 180 (2001); http://dx.doi.org/10.1063/1.1385350 (2 pages) | Cited 1 time

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A numerical algorithm for nonlinear elastic relaxation of a multilayer woven fabric is introduced and tested. The equilibrium solutions are compared with real samples. An excellent result is obtained in spite of two simplifications: Bending stiffness of the fibers and friction between the fibers are both neglected. The numerical simulation is very fast and cost efficient in the search for optimal fabrics. © 2001 American Institute of Physics.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.F- Deformation and plasticity

Degradation kinetics of thermal oxides

Fernanda Irrera

Appl. Phys. Lett. 79, 182 (2001); http://dx.doi.org/10.1063/1.1385193 (3 pages) | Cited 8 times

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In this letter I propose a kinetics model of trap creation in thermal oxides under electrical stress. The model is based on the idea that electrons drifted in the oxide conduction band by the stress field undergo scattering by existing defects. The process controls the creation of additional traps. The kinetics model predicts a square root dependence on the stress time. Model results are validated by experimental data of stress induced leakage current. Defect concentrations calculated with my kinetics model were used in a trap-assisted model and yielded excellent fits of the low-field conductivity © 2001 American Institute of Physics.
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73.61.Ng Insulators
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
71.55.Ht Other nonmetals
85.30.De Semiconductor-device characterization, design, and modeling

Effect of water absorption on the residual stress in fluorinated silicon-oxide thin films fabricated by electron-cyclotron-resonance plasma-enhanced chemical-vapor deposition

S. P. Kim, S. K. Choi, Youngsoo Park, and Ilsub Chung

Appl. Phys. Lett. 79, 185 (2001); http://dx.doi.org/10.1063/1.1383278 (3 pages) | Cited 10 times

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Fluorinated silicon-oxide (SiOF) films were produced by electron-cyclotron-resonance plasma-enhanced chemical-vapor deposition. The effect of water absorption on the film properties was studied by measuring the residual stress as a function of exposure time to room air. The residual stress shows an increase of the compressive component as the film absorbs water. However, the chemical bonding structure does not change after the water absorption. The residual stress returns to the initial value when the film is dried. It is suggested that the water absorption occurs entirely by physical adsorption of H2O molecules to Si–F bonds. © 2001 American Institute of Physics.
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73.61.Ng Insulators
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.60.Bs Mechanical and acoustical properties
52.77.Dq Plasma-based ion implantation and deposition

Nanoparticles and nanoballoons of amorphous boron coated with crystalline boron nitride

Shojiro Komatsu, Yoshiki Shimizu, Yusuke Moriyoshi, Katsuyuki Okada, and Mamoru Mitomo

Appl. Phys. Lett. 79, 188 (2001); http://dx.doi.org/10.1063/1.1383059 (3 pages) | Cited 8 times

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Solid- and hollow-cored nanoparticles of amorphous boron coated with crystalline boron nitride (BN) have been synthesized by pulsed-laser vaporization of BN, where the laser plume was controlled with a modulated plasma jet. The hollow particles (nanoballoons) were coated with BN both on the interior and exterior surfaces. The solid particles ranged from a few to 40 nm in their size. The typical diameter of the hollow particles and their wall thickness were about 200 and 30 nm, respectively. The nanoballoons were obtained only when the plasma modulation was synchronized with the ArF excimer-laser pulses. © 2001 American Institute of Physics.
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81.07.Bc Nanocrystalline materials
61.46.-w Structure of nanoscale materials
61.43.Er Other amorphous solids
52.77.Dq Plasma-based ion implantation and deposition
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Lateral heterogeneity in the surface composition after laser processing of Ti/Si interface contaminated with oxygen

R. Larciprete, A. Danailov, A. Barinov, L. Casalis, L. Gregoratti, and M. Kiskinova

Appl. Phys. Lett. 79, 191 (2001); http://dx.doi.org/10.1063/1.1384902 (3 pages) | Cited 3 times

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The lateral variations in the surface composition of an oxygen-contaminated Ti/Si(001) interface processed by pulsed laser annealing were investigated by synchrotron radiation x-ray photoemission spectromicroscopy. It has been found that SiO2, which segregates on top of the Ti silicide film, appears only in a circular edge region of the laser spots and is completely absent in the hotter internal area, where SiO evaporation has occurred. The results demonstrate that the temperature gradient within the laser-irradiated area can affect substantially the lateral homogeneity of the fabricated interfaces, an important issue for microdevice technology. © 2001 American Institute of Physics.
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68.35.Dv Composition, segregation; defects and impurities
61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Fk Semiconductors
79.60.Jv Interfaces; heterostructures; nanostructures
81.05.Cy Elemental semiconductors
68.35.Ct Interface structure and roughness

Defect characterization in ZnO layers grown by plasma-enhanced molecular-beam epitaxy on (0001) sapphire substrates

F. Vigué, P. Vennéguès, S. Vézian, M. Laügt, and J.-P. Faurie

Appl. Phys. Lett. 79, 194 (2001); http://dx.doi.org/10.1063/1.1384907 (3 pages) | Cited 48 times

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The structural properties of high-quality (0001)ZnO/Al2O3 films grown by plasma-enhanced molecular-beam epitaxy are investigated by x-ray diffraction and transmission electron microscopy. The only defects encountered are threading dislocations with a density of 1010–4×1010 cm−2. Most numerous dislocations are pure-edge dislocations (Burgers vector of 1/3〈11math0〉), which accommodate slight in-plane misorientations between subgrains. The oxygen polarity of these films is also established. © 2001 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.05.cp X-ray diffraction
68.37.Lp Transmission electron microscopy (TEM)

Bipolar phototransport in π-conjugated polymer /C60 composites

I. Balberg, R. Naidis, M.-K. Lee, J. Shinar, and L. F. Fonseca

Appl. Phys. Lett. 79, 197 (2001); http://dx.doi.org/10.1063/1.1383801 (3 pages) | Cited 10 times

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Conjugated polymer/fullerene composite films that exhibit steady-state phototransport properties of a unipolar or bipolar photoconductor, depending on the relative concentration of the components, are described. The observed behavior of the composites, in which each component has its own percolation path but its carrier content is not high enough to quench the carriers in the other component, is shown to be due to the coupling of the recombination processes in the two components. © 2001 American Institute of Physics.
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73.61.Ph Polymers; organic compounds
73.61.Wp Fullerenes and related materials
72.80.Tm Composite materials
72.40.+w Photoconduction and photovoltaic effects
71.20.Rv Polymers and organic compounds
72.15.Nj Collective modes (e.g., in one-dimensional conductors)
71.20.Tx Fullerenes and related materials; intercalation compounds
73.50.Pz Photoconduction and photovoltaic effects
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Nitrogen-related complexes in gallium arsenide

J. E. Lowther, S. K. Estreicher, and H. Temkin

Appl. Phys. Lett. 79, 200 (2001); http://dx.doi.org/10.1063/1.1383280 (3 pages) | Cited 9 times

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A first-principles pseudopotential method has been used to study some potentially important metastable defects in N-doped GaAs. Formation energies have been obtained and related to those of As and Ga vacancies in the intrinsic material. Of the structures considered, two are identified that crucially depend on overall material stoichiometry. These are N on a Ga site (NGa) or a NN dimer on an As site (NNAs). NGa has a partly shallow energy-level structure with a fully occupied level lying near the valence-band edge, whereas NNAs has localized character with a midgap deep level. Both defects may be responsible for the onset of a reduction in the apparent band gap that has been recently observed in heavily N-doped GaAs prior to alloying. © 2001 American Institute of Physics.
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71.55.Eq III-V semiconductors
61.72.J- Point defects and defect clusters
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)
61.66.Bi Elemental solids
61.66.Dk Alloys

Solving the structural model for the Si(001)–In(4×3) surface

T. M. Schmidt, J. L. P. Castineira, and R. H. Miwa

Appl. Phys. Lett. 79, 203 (2001); http://dx.doi.org/10.1063/1.1383275 (3 pages) | Cited 8 times

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The atomic geometry, energetic, and scanning tunneling microscopy (STM) simulations of the In-induced Si(001)-(4×3) surface have been investigated using first-principles total energy calculations. We have studied three distinct (4×3) structural models, which have been proposed based on STM and x-ray diffraction experiments. The energetic stability calculations indicate that the (4×3) model formed by In–Si–In mixed trimer is the most stable structure. In addition, we have simulated the STM images (for occupied states) of these three models. Our STM image for the In–Si–In mixed trimer structure presents a good agreement with the experimentally observed single central protrusion localized on the top-layer Si atom. Also, the calculated equilibrium atomic geometry of the In–Si–In mixed trimer model presents a good agreement with the experimentally obtained x-ray diffraction results. The other two proposed models are energetically less favorable by as much as 0.2 eV/(1×1) compared to the mixed trimer model. © 2001 American Institute of Physics.
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68.43.Fg Adsorbate structure (binding sites, geometry)
81.05.Cy Elemental semiconductors
71.15.Nc Total energy and cohesive energy calculations
68.35.Md Surface thermodynamics, surface energies
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.35.B- Structure of clean surfaces (and surface reconstruction)

High temperature semiconducting characteristics of magnesium-doped α-Al2O3 single crystals

M. Tardío, R. Ramírez, R. González, Y. Chen, and M. R. Kokta

Appl. Phys. Lett. 79, 206 (2001); http://dx.doi.org/10.1063/1.1384481 (3 pages) | Cited 5 times

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In the temperature interval 300–773 K, ac and dc electrical measurements show a phenomenally large enhancement of the electrical conductivity of otherwise excellent insulator Al2O3 crystals when doped with magnesium impurities. The conductivity increases linearly with the concentration of hole-trapped [Mg]0 centers and is four times higher in the direction parallel to the crystallographic c axis than in the perpendicular direction. The conductivity activation energy is 0.68 eV, independent of both [Mg]0 content and crystallographic orientation. Electroluminescence experiments indicate that holes are the majority carriers. These results favor the small-polaron-motion mechanism. © 2001 American Institute of Physics.
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72.80.Jc Other crystalline inorganic semiconductors
78.60.Fi Electroluminescence
72.20.Fr Low-field transport and mobility; piezoresistance
71.55.Ht Other nonmetals

Nonlinear current–voltage relations in polycrystalline perovskite manganites ceramics

John Philip and T. R. N. Kutty

Appl. Phys. Lett. 79, 209 (2001); http://dx.doi.org/10.1063/1.1384474 (3 pages) | Cited 11 times

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Highly nonlinear current–voltage (J∝Eα) relations with voltage-limiting characteristics are observed for Mg-doped lanthanum calcium manganite polycrystalline ceramics with nonlinearity coefficient, α = 2–9 at low-electric-field strengths of 2–5 V/mm, below magnetic transition temperatures. The current density increases with external magnetic field, so that magnetically tunable low-voltage varistors are realized. The α increases on annealing at 1375 K in atmospheres of lower pO2, and becomes more pronounced with decreasing grain size, indicating that nonlinear behavior is related to the outdiffusion of oxygen through the grain-boundary-layer regions. The increasing deficiency in Mn3+/Mn4+ pairs reduces the hole-hopping probability leading to insulating barriers in the grain-boundary-layer regions. The barrier height is lowered by the external electric field, facilitating the charge-carrier movement between the grains. Since the conduction is due to spin-polarized tunneling, the external magnetic field increases the current. © 2001 American Institute of Physics.
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75.47.Gk Colossal magnetoresistance
61.72.Cc Kinetics of defect formation and annealing
61.72.Mm Grain and twin boundaries

Role of holes in the isotope effect and mechanisms for the metal–oxide–semiconductor device degradation

Zhi Chen, Pradeep Garg, Vijay Singh, and Sundar Chetlur

Appl. Phys. Lett. 79, 212 (2001); http://dx.doi.org/10.1063/1.1384900 (3 pages) | Cited 2 times

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An experiment that incorporates the deuterium isotope effect into the “hole trapping and electron filling” scenario in silicon metal–oxide–semiconductor (MOS) devices is presented. It is suggested that Lai’s physical model is only partially true in order to explain all of the observed MOS device degradation phenomena. The isotope effect is exclusively due to hot electrons, not hot holes. Holes might break the Si–O bonds to generate interface traps at VG near VT. The dominant degradation mechanism is the electron-stimulated Si–H bond breaking, although electron trapping also plays a role in degradation. © 2001 American Institute of Physics.
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85.30.Tv Field effect devices
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Formation mechanism of V defects in the InGaN/GaN multiple quantum wells grown on GaN layers with low threading dislocation density

H. K. Cho, J. Y. Lee, G. M. Yang, and C. S. Kim

Appl. Phys. Lett. 79, 215 (2001); http://dx.doi.org/10.1063/1.1384906 (3 pages) | Cited 52 times

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V-defect formation of the InxGa1−xN/GaN multiple quantum wells (MQWs) grown on GaN layers with different threading dislocation (TD) densities was investigated. From cross-sectional transmission electron microscopy, we found that all V defects are not always connected with TDs at their bottom. By increasing the indium composition in the InxGa1−xN well layer or decreasing the TD density of the thick GaN layer, many V defects are generated from the stacking mismatch boundaries induced by stacking faults which are formed within the MQW due to the strain relaxation. Also, TD density in the thick GaN layer affects not only the origin of V-defect formation but also the critical indium composition of the InxGa1−xN well on the formation of V defects. © 2001 American Institute of Physics.
Show PACS
68.65.Fg Quantum wells
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.Nn Stacking faults and other planar or extended defects
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