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14 Dec 1998

Volume 73, Issue 24, pp. 3483-3612

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Wavelength tuning of 1/2-rational harmonically mode-locked pulses in a cavity-dispersive fiber laser

Y. Zhao, C. Shu, J. H. Chen, and F. S. Choa

Appl. Phys. Lett. 73, 3483 (1998); http://dx.doi.org/10.1063/1.122811 (3 pages) | Cited 7 times

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We investigate electrical wavelength tuning of a cavity length dispersive fiber ring laser operated in the 1/2-rational harmonic mode-locking condition. By changing the modulator frequency around the optimum mode-locking frequency, a tuning range of 10.45 nm with a tuning rate of 0.067 nm/kHz is achieved. The repetition rate of the mode-locked pulses is twice the modulation frequency (∼1 GHz) and the extinction ratio of the laser spectrum during the full tuning range is above 30 dB. Compared with the conventionally harmonic mode locking, the tuning range is about half reduced but the tuning rate has a same value. The variation of the modulation frequency and the length of the dispersion compensation fiber has a same effect on the wavelength tuning as in the case of conventionally harmonic mode-locking. © 1998 American Institute of Physics.
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42.55.Wd Fiber lasers
42.60.By Design of specific laser systems
42.60.Fc Modulation, tuning, and mode locking
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

GaAs/AlxGa1−xAs quantum cascade lasers

Carlo Sirtori, Peter Kruck, Stefano Barbieri, Philippe Collot, Julien Nagle, Mattias Beck, Jérôme Faist, and Ursula Oesterle

Appl. Phys. Lett. 73, 3486 (1998); http://dx.doi.org/10.1063/1.122812 (3 pages) | Cited 182 times

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A unipolar injection quantum cascade (QC) laser grown in an AlGaAs/GaAs material system by molecular beam epitaxy, is reported. The active material is a 30 period sequence of injectors/active regions made from Al0.33Ga0.67As/GaAs-coupled quantum wells. For this device a special waveguide design, which complies with a GaAs heavily doped substrate and very short Al0.90Ga0.10As cladding layers, has been optimized. At a heat-sink temperature of 77 K, the laser emission wavelength is 9.4 μm with peak optical power exceeding 70 mW and the threshold current density is 7.3 kA/cm2. The maximum operating temperature is 140 K. This work experimentally demonstrates the general validity of QC laser principles by showing laser action in a heterostructure material different from the one used until now. © 1998 American Institute of Physics.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
42.82.Et Waveguides, couplers, and arrays

Deformation of ferroelectric short-pitch helical liquid crystal by transverse electric field: Application for diffraction-based light modulator

A. Parfenov

Appl. Phys. Lett. 73, 3489 (1998); http://dx.doi.org/10.1063/1.122813 (3 pages) | Cited 2 times

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The electro-optic effect in helical ferroelectric liquid crystal deformed by transverse electric field is exploited to realize a diffraction-based light modulator. Experiments show that a contrast ratio better than 100:1 is easily achievable for the short-pitch liquid crystal aligned homeotropically with oblique readout breaking the initial symmetrical geometry. The modulation obtains low polarization sensitivity for selected directions of the readout. © 1998 American Institute of Physics.
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77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
78.20.Jq Electro-optical effects
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
77.65.-j Piezoelectricity and electromechanical effects
42.79.Hp Optical processors, correlators, and modulators
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Low-threshold amplified spontaneous emission in blends of conjugated polymers

R. Gupta, M. Stevenson, A. Dogariu, M. D. McGehee, J. Y. Park, V. Srdanov, A. J. Heeger, and H. Wang

Appl. Phys. Lett. 73, 3492 (1998); http://dx.doi.org/10.1063/1.122814 (3 pages) | Cited 48 times

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Low thresholds (∼500 W/cm2) for amplified spontaneous emission (ASE) are reported in films of soluble poly(paraphenylene vinylene)-based conjugated polymer blends. Efficient Förster energy transfer from the absorbing host polymer to the emitting guest polymer is observed. Emission in the blends originates predominantly from the guest polymer. The large spectral shift between the absorption and emission wavelengths lowers the self-absorption losses and results in low ASE thresholds. Initial results show an enhancement in photoluminescence quantum efficiency of the blends. © 1998 American Institute of Physics.
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78.45.+h Stimulated emission
78.66.Qn Polymers; organic compounds
61.41.+e Polymers, elastomers, and plastics

Two-dimensional rough surface couplers for broadband quantum-well infrared photodetectors

Vikram Jandhyala, Deepak Sengupta, Eric Michielssen, Balasubramaniam Shanker, and Greg Stillman

Appl. Phys. Lett. 73, 3495 (1998); http://dx.doi.org/10.1063/1.122815 (3 pages) | Cited 2 times

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Rough surfaces are proposed as a class of couplers for achieving high absorption in broadband quantum-well infrared photodetectors (QWIPs). The performance of these structures is predicted numerically using the steepest-descent fast-multipole method, a recently developed fast electromagnetic analysis technique. This method permits the efficient and accurate solution of the electric-field integral equation governing scattering from a quasiplanar structure. The scattered optical electric-field component along the growth direction at the device layer can be used to predict the QWIP absorption. It is demonstrated that rough-surface couplers exhibit very high absorption sustained over large spectral ranges, in contrast to quasirandom or periodic gratings that are characterized by tradeoffs between peak absorption and spectral range. It is expected that the excellent spectral absorption characteristics of rough-surface couplers will make them particularly suitable for broadband QWIP applications. © 1998 American Institute of Physics.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)
68.35.Ct Interface structure and roughness
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Time-resolved surface scattering imaging of organic liquids under femtosecond KrF laser pulse excitation

Koji Hatanaka, Tamitake Itoh, Tsuyoshi Asahi, Nobuyuki Ichinose, Shunichi Kawanishi, Tsuneo Sasuga, Hiroshi Fukumura, and Hiroshi Masuhara

Appl. Phys. Lett. 73, 3498 (1998); http://dx.doi.org/10.1063/1.122816 (3 pages) | Cited 9 times

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Time-resolved surface scattering imaging was performed for liquid benzyl chloride and liquid toluene under femtosecond KrF laser ablation conditions. No scattering image was obtained until 1 ns, while scattering started from 2 ns when the laser fluence exceeded 25 mJ/cm2, and its intensity increased with the passage of time. The higher the laser fluence was, the steeper the increasing slope was. The scattering is due to surface roughness, which is the initial stage of macroscopic morphological changes. Root-mean-square surface roughness was estimated from the scattering intensity by using frosted fused-silica plates as reference samples. The induced surface roughness increases to a few hundred nm in 10 ns. © 1998 American Institute of Physics.
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78.47.-p Spectroscopy of solid state dynamics
78.35.+c Brillouin and Rayleigh scattering; other light scattering
61.25.Em Molecular liquids
68.03.Fg Evaporation and condensation of liquids

Spectral identification of transverse lasing modes of multimode index-guided vertical-cavity surface-emitting lasers

D. Burak, S. A. Kemme, R. K. Kostuk, and R. Binder

Appl. Phys. Lett. 73, 3501 (1998); http://dx.doi.org/10.1063/1.122817 (3 pages) | Cited 4 times

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The identification of lasing modes in vertical-cavity surface-emitting lasers (VCSELs) is usually based on the polarization-resolved near-field pattern identification, a method difficult to apply in the presence of multiple transverse modes. We study lasing modes of a multitransverse mode index-guided VCSEL under dc pumping conditions by considering in detail the modes’ spectral positions. The experimentally observed spectra are compared with theoretical calculations, based on a recently developed method for vectorial VCSEL eigenmodes [D. Burak and R. Binder, Appl. Phys. Lett. 72, 891 (1998)]. This allows for the identification of transverse lasing modes as a function of the pumping current. Two main effects that influence the spectral characteristics of the VCSEL are considered in our approach: temperature-induced linear shift of lasing wavelengths with increasing pumping current and switching of the lasing mode between different eigenmodes of the VCSEL cavity. The obtained temperature-dependent shift of the lasing frequencies agrees reasonably well with the value known from previous experimental estimations. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking

Monolithic integration of a SiGe/Si modulator and multiple quantum well photodetector for 1.55 μm operation

Baojun Li, Guozheng Li, Enke Liu, Zuimin Jiang, Jie Qin, and Xun Wang

Appl. Phys. Lett. 73, 3504 (1998); http://dx.doi.org/10.1063/1.122818 (2 pages) | Cited 9 times

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The monolithic integration of a SiGe/Si rib waveguide modulator and multiple quantum well photodetector prepared by molecular beam epitaxy is achieved. The low dark current of 49.8 nA at −5 V reverse bias is measured and a modulation depth of 90% at 2.8 V modulation bias is obtained. The external quantum efficiency at λ = 1.55 μm is estimated to be 18.2%. © 1998 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.79.Hp Optical processors, correlators, and modulators
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
42.82.Fv Hybrid systems

Observation of inhibited spontaneous emission and stimulated emission of rhodamine 6G in polymer replica of synthetic opal

K. Yoshino, S. B. Lee, S. Tatsuhara, Y. Kawagishi, M. Ozaki, and A. A. Zakhidov

Appl. Phys. Lett. 73, 3506 (1998); http://dx.doi.org/10.1063/1.122819 (3 pages) | Cited 65 times

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We report the observation of inhibited spontaneous emission of organic dye rhodamine 6G infiltrated in a polymer replica of synthetic opal as a photonic crystal. The morphology-dependent resonances, superimposed on the broadband emission of rhodamine 6G due to spherical wavelength-sized microcavity enhancement of dye emission, have also been observed. © 1998 American Institute of Physics.
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78.45.+h Stimulated emission
42.70.Jk Polymers and organics
42.50.-p Quantum optics
42.70.Qs Photonic bandgap materials
78.55.Kz Solid organic materials

Surface defect scattering of surface plasmon polaritons: Mirrors and light emitters

J. A. Sánchez-Gil

Appl. Phys. Lett. 73, 3509 (1998); http://dx.doi.org/10.1063/1.122820 (3 pages) | Cited 44 times

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We study the near-field and the angular distribution of radiation resulting from the scattering of surface plasmon polaritons from a surface defect by means of numerical calculations based on the use of the impedance boundary condition. Maximum reflection (plasmon mirrors) is found for half widths on the order of the inverse of the surface plasmon wavevector, either protuberances or indentations, as predicted by a perturbation-theoretic argument. Maximum radiation (light emitters) occurs for wider protuberances, with coupling efficiencies beyond 80%. © 1998 American Institute of Physics.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.66.Bz Metals and metallic alloys
07.79.Fc Near-field scanning optical microscopes

Optical constants of (Al0.98Ga0.02)xOy native oxides

K. J. Knopp, R. P. Mirin, D. H. Christensen, K. A. Bertness, A. Roshko, and R. A. Synowicki

Appl. Phys. Lett. 73, 3512 (1998); http://dx.doi.org/10.1063/1.122821 (3 pages) | Cited 9 times

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We report the optical constants of oxidized crystalline and low-temperature-grown (LTG) Al0.98Ga0.02As films, as determined by variable angle spectroscopic ellipsometry. Data were acquired at three angles of incidence over 240–1700 nm and fitted to a Cauchy dispersion function. For oxidized crystalline material, we observe a variation in the real index of ±0.5% for layer thickness variations of ±6%. We show that upon oxidation, LTG material can expand by >25% while crystalline material contracts by <2%. Atomic force microscopy analysis indicates thickness-dependent variations in the oxide microstructure. Additionally, an optical scattering loss of 2.1×10−4%/pass is calculated based on surface roughness measurements for a thin layer of oxidized crystalline material. © 1998 American Institute of Physics.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
81.65.Mq Oxidation
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Local dynamics in polymer-dispersed liquid crystals studied by near-field scanning optical microscopy

Erwen Mei and Daniel A. Higgins

Appl. Phys. Lett. 73, 3515 (1998); http://dx.doi.org/10.1063/1.122822 (3 pages) | Cited 7 times

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Electric-field-induced molecular reorientation dynamics are studied in localized regions within polymer-dispersed liquid-crystal (PDLC) films, using time-resolved near-field scanning optical microscopy (NSOM) methods. A concentrated electric field is applied across the PDLC film, between the metallized NSOM probe and the conductive, transparent substrate supporting the sample. The electric field is modulated as a square wave form at (sub)-kilohertz frequencies. Subsequent liquid-crystal (LC) reorientation is observed by crossed-polarized, transmitted-light NSOM methods. The results show dramatic spatial variations in the time scale over which the molecules reorient. The variations are interpreted based on proximity of the region probed to the polymer–LC interface. © 1998 American Institute of Physics.
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61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures
07.79.Fc Near-field scanning optical microscopes

Effects of annealing on self-organized InAs quantum islands on GaAs(100)

Q. W. Mo, T. W. Fan, Q. Gong, J. Wu, Z. G. Wang, and Y. Q. Bai

Appl. Phys. Lett. 73, 3518 (1998); http://dx.doi.org/10.1063/1.122842 (3 pages) | Cited 17 times

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Self-organized InAs islands on (001) GaAs grown by molecular beam epitaxy were annealed and characterized with photoluminescence (PL) and transmission electron microscopy (TEM). The PL spectra from the InAs islands demonstrated that annealing resulted in a blueshift in peak energy, a reduction in intensity, and a narrower linewidth in the PL peak. In addition, the TEM analysis revealed the relaxation of strain in some InAs islands with the introduction of the network of 90° dislocations. The correlation between the changes in the PL spectra and the relaxation of strain in InAs islands was discussed. © 1998 American Institute of Physics.
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68.55.-a Thin film structure and morphology
61.72.Cc Kinetics of defect formation and annealing
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.07.-b Nanoscale materials and structures: fabrication and characterization
78.66.Fd III-V semiconductors

Identification of structural changes in carbon–nitrogen alloys by studying the dependence of the plasmon energy on nitrogen concentration

F. Alvarez, M. C. dos Santos, and P. Hammer

Appl. Phys. Lett. 73, 3521 (1998); http://dx.doi.org/10.1063/1.122823 (3 pages) | Cited 16 times

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The effect of nitrogen on the valence-electron plasmon energy in amorphous carbon–nitrogen alloys (a-C1−xNx) is used to identify structural changes in the material. The samples were prepared by dual-ion-beam-assisted deposition and studied in situ by x-ray photoemission spectroscopy. The plasmon energy of the alloy goes through a maximum above 15–20 at.% nitrogen concentration. This behavior is correlated with structural changes obtained in a semiempirical quantum chemical calculation on graphite-like carbon clusters, randomly substituted by nitrogen. At that concentration, the geometry optimization shows that the graphite-like conformation is unstable against the buckling of the structure. © 1998 American Institute of Physics.
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61.43.Er Other amorphous solids
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
71.23.Cq Amorphous semiconductors, metallic glasses, glasses
79.60.Ht Disordered structures

Growth and characterization of 10-nm-thick c-axis oriented epitaxial PbZr0.25Ti0.75O3 thin films on (100)Si substrate

T. Maruyama, M. Saitoh, I. Sakai, T. Hidaka, Y. Yano, and T. Noguchi

Appl. Phys. Lett. 73, 3524 (1998); http://dx.doi.org/10.1063/1.122824 (3 pages) | Cited 35 times

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A 10-nm-thick PbZr0.25Ti0.75O3 thin film is epitaxially grown on a SrRuO3/BaTiO3/ZrO2/Si heterostructure substrate by reactive evaporation. Structural and electrical properties of the film are investigated. It is concluded that the film is ferroelectric and retains a native uniform upward polarization. Artificial downward polarization domains, whose average diameter is 24 nm, can be formed in the film. © 1998 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.-a Thin film structure and morphology
77.55.-g Dielectric thin films
77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization

Transmission electron microscopy observations of fracture of single-wall carbon nanotubes under axial tension

O. Lourie and H. D. Wagner

Appl. Phys. Lett. 73, 3527 (1998); http://dx.doi.org/10.1063/1.122825 (3 pages) | Cited 78 times

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Well-aligned bundles of single-wall carbon nanotubes under tensile stresses were observed to fracture in real-time by transmission electron microscopy. The expansion of elliptical holes in the polymer matrix results in a tensile force in bridging nanotubes. The polymer matrix at both ends of the bundles deforms extensively under the tension force, and fracture of the nanotubes occurs in tension within the polymer hole region rather than in shear within the gripping polymer region at the ends of the bundles. This provides evidence of significant polymer-nanotube wetting and interfacial adhesion. © 1998 American Institute of Physics.
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81.05.ub Fullerenes and related materials
62.20.M- Structural failure of materials
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
61.41.+e Polymers, elastomers, and plastics
68.35.Gy Mechanical properties; surface strains
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Effect of oxygen on the growth of (10math0) GaN surfaces: The formation of nanopipes

J. Elsner, R. Jones, M. Haugk, R. Gutierrez, Th. Frauenheim, M. I. Heggie, S. Öberg, and P. R. Briddon

Appl. Phys. Lett. 73, 3530 (1998); http://dx.doi.org/10.1063/1.122826 (3 pages) | Cited 25 times

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Local density–functional methods are used to examine the behavior of O and O-related defect complexes on the walls of nanopipes in GaN. We find that O has a tendency to segregate to the (10math0) surface and identify the gallium vacancy surrounded by three oxygen impurities [VGa–(ON)3] to be a particularly stable and electrically inert complex. We suggest that during Stranski–Krastanow growth, when interisland spaces shrink, these defects reach a critical concentration beyond which further growth is prevented and nanopipes are formed. © 1998 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Fx Diffusion; interface formation
81.05.Ea III-V semiconductors
61.46.-w Structure of nanoscale materials

The electronic conduction mechanism in barium strontium titanate thin films

Sufi Zafar, Robert E. Jones, Bo Jiang, Bruce White, V. Kaushik, and S. Gillespie

Appl. Phys. Lett. 73, 3533 (1998); http://dx.doi.org/10.1063/1.122827 (3 pages) | Cited 85 times

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In the literature, the Schottky emission equation is widely used to describe the conduction mechanism in perovskite-type titanate thin films. Though the equation provides a good fit to the leakage current data, the extracted values of the Richardson and dielectric constants are inconsistent with their experimental values. In this work, a modified Schottky equation is applied. This equation resolves the difficulties associated with the standard Schottky equation. Also, the electronic mobility in thin films of barium strontium titanate is reported. © 1998 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
77.22.Ch Permittivity (dielectric function)
77.80.-e Ferroelectricity and antiferroelectricity

Tunneling transport and diffusion in weakly coupled quantum dot ensembles

D. G. Deppe and Q. Deng

Appl. Phys. Lett. 73, 3536 (1998); http://dx.doi.org/10.1063/1.122799 (3 pages) | Cited 8 times

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The lateral tunneling rate and carrier diffusion in weakly coupled quantum dots are analyzed. In the weak coupling limit, localization of charge within a single dot is obtained through superposition of the lowest-energy eigenstates of coupled dots. The free evolution of the wave function leads to tunneling, but with a time dependence that includes dephasing. Idealized quantum dot boundary conditions are used to estimate tunneling times, and these are compared with recent experiments. © 1998 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.20.Fz Weak or Anderson localization
73.40.Gk Tunneling
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Quantum Monte Carlo simulation of resonant tunneling diodes based on the Wigner distribution function formalism

J. García-García, F. Martín, X. Oriols, and J. Suñé

Appl. Phys. Lett. 73, 3539 (1998); http://dx.doi.org/10.1063/1.122800 (3 pages) | Cited 3 times

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A tool for the simulation of resonant tunneling diodes (RTDs) has been developed. This is based on the solution of the quantum Liouville equation in the active region of the device and the Boltzman transport equation in the regions adjacent to the contacts by means of a Monte Carlo algorithm. By accurately coupling both approaches to current transport, we have developed a quantum simulation tool that allows the use of simulation domains much larger and realistic than those previously considered, without a significant increase in computational burden. The main characteristics expected for the considered devices are clearly obtained, thus supporting the validity of our tool for the simulation of RTDs. © 1998 American Institute of Physics.
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85.30.Kk Junction diodes
85.30.De Semiconductor-device characterization, design, and modeling

Initial stages in the carbonization of (111)Si by solid-source molecular beam epitaxy

V. Cimalla, Th. Stauden, G. Ecke, F. Scharmann, G. Eichhorn, J. Pezoldt, S. Sloboshanin, and J. A. Schaefer

Appl. Phys. Lett. 73, 3542 (1998); http://dx.doi.org/10.1063/1.122801 (3 pages) | Cited 16 times

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Silicon carbide can be reproducibly grown on (111)Si below 600 °C by carbonization using an elemental solid carbon source in molecular beam epitaxy. The initial stages were observed by in situ reflection high-energy electron diffraction. Prior to silicon carbide growth, the continuous carbon flux lead to a transition from the (7×7) reconstruction of clean (111)Si to a carbon-induced (√×√)R30° structure. Above 660 °C, the silicon carbide growth starts directly on the silicon surface via three-dimensional nucleation. Below 660 °C, first a thin silicon–carbon alloy was formed by diffusion of carbon into the surface near the region with a concentration exceeding the bulk solubility in silicon. © 1998 American Institute of Physics.
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81.05.Hd Other semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology

Ohmic contacts to p-6H–SiC using focused ion-beam surface-modification and pulsed laser epitaxial TiN deposition

A. A. Iliadis, S. N. Andronescu, K. Edinger, J. H. Orloff, R. D. Vispute, V. Talyansky, R. P. Sharma, T. Venkatesan, M. C. Wood, and K. A. Jones

Appl. Phys. Lett. 73, 3545 (1998); http://dx.doi.org/10.1063/1.122802 (3 pages) | Cited 4 times

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The development of low-resistance Ohmic metallizations to p-type 6H–SiC, using a focused ion-beam (FIB)-Ga surface-modification and ex situ pulsed laser (PLD) epitaxial TiN deposition without further annealing, is reported. The FIB-Ga surface-modification and PLD epitaxial TiN metallizations showed a minimum value of contact resistance of 4.4×10−5 Ω cm2 at an ion dose and energy of 5.0×1016 ions/cm2 and 20 keV, respectively. Auger analysis data indicated well-defined interfaces between the metal and the semiconductor, and a significant subsurface Ga concentration. © 1998 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
73.40.Cg Contact resistance, contact potential
85.40.Sz Deposition technology
73.40.Ns Metal-nonmetal contacts
81.15.Fg Pulsed laser ablation deposition

Evaluation of electrical stress effects on SiO2–Si structures using scanning electron microscope cathodoluminescence

X. Liu, D. S. H. Chan, W. K. Chim, and J. C. H. Phang

Appl. Phys. Lett. 73, 3548 (1998); http://dx.doi.org/10.1063/1.122803 (2 pages)

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In this letter, we describe the hot-electron-injection-induced 2.7 eV luminescence centers and the interfacial stress dependence of the 2.7 eV cathodoluminescence peak buildup in SiO2–Si structures. The results suggest that electrical stress may relax the interface strain and modulate the radiation sensitivity. This phenomenon may be extended to provide a nonelectrical and physical evaluation of the electrical stress degradation of SiO2–Si structures. Possible mechanisms are proposed to explain the observations. © 1998 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
78.60.Hk Cathodoluminescence, ionoluminescence
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)

Time-resolved photoluminescence measurements of InGaN light-emitting diodes

M. Pophristic, F. H. Long, C. Tran, I. T. Ferguson, and R. F. Karlicek

Appl. Phys. Lett. 73, 3550 (1998); http://dx.doi.org/10.1063/1.122843 (3 pages) | Cited 37 times

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We have used time-resolved photoluminescence (PL) to examine light-emitting diodes made of InGaN/GaN multiple quantum wells (MQWs) before the final stages of processing. The time-resolved photoluminescence from a dim MQW was quenched by nonradiative recombination centers. The PL kinetics from a bright MQW were not single exponential but stretched exponential, with the stretch parameter β = 0.59±0.05. The emission lifetime varied with energy, within error β was independent of the emission energy. the stretched exponential kinetics are consistent with significant disorder in the material. We attribute the disorder to spatial fluctuations of the local indium concentration. © 1998 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.55.Cr III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics
78.66.Fd III-V semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Hole-assisted Zener magnetotunneling in heterostructures

Riccardo A. G. Cinelli, Vincenzo Piazza, Silvano De Franceschi, Marco Lazzarino, Fabio Beltram, Deborah L. Sivco, and Alfred Y. Cho

Appl. Phys. Lett. 73, 3553 (1998); http://dx.doi.org/10.1063/1.122804 (3 pages) | Cited 2 times

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Electron transport at high electric fields is investigated in a periodic semiconductor heterostructure. We present the analysis of the magnetic-field dependence of resonant Zener tunneling from a valence-band subband to a conduction-band subband in a multiple-quantum-well heterostructure. It is shown that Zener tunneling can have a different physical origin in such structures with respect to bulk systems. The dominant role of holes trapped in the valence-band quantum wells in driving this process is demonstrated. © 1998 American Institute of Physics.
Show PACS
73.61.Ey III-V semiconductors
73.40.Gk Tunneling
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.50.Fq High-field and nonlinear effects
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
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