By Topic

Applied Physics Letters

Issue 3 • Date Jan 2000

Filter Results

Displaying Results 1 - 25 of 50
  • Issue Cover

    Page(s): c1
    Save to Project icon | PDF file iconPDF (24 KB)  
    Freely Available from IEEE
  • Issue Table of Contents

    Page(s): toc1
    Save to Project icon | PDF file iconPDF (23 KB)  
    Freely Available from IEEE
  • GaAs/AlGaAs distributed feedback quantum cascade lasers

    Page(s): 253 - 255
    Save to Project icon | PDF file iconPDF (199 KB)  

    We report on the realization of distributed feedback quantum cascade lasers in the GaAs/AlGaAs material system. A metallized surface relief grating is used for feedback. Both single mode and double mode emission is observed at λ≈10 μm. The coupling coefficient is measured from the mode spacing for double mode emission to be 24 cm-1. The emission wave number can be tuned with the temperature at a rate of dν/dT≈0.048 cm-1/K. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Continuous-wave operation of λ=3.25 μm broadened-waveguide W quantum-well diode lasers up to T=195 K

    Page(s): 256 - 258
    Save to Project icon | PDF file iconPDF (50 KB)  

    Mid-infrared (λ=3.25 μm) broadened-waveguide diode lasers with active regions consisting of 5 type-II “W” quantum wells operated in continuous-wave (cw) mode up to 195 K. At 78 K, the threshold current density was 63 A/cm2, and up to 140 mW of cw output power was generated. A second structure with ten quantum wells operated up to 310 K in pulsed mode. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Transparent conducting aluminum-doped zinc oxide thin films for organic light-emitting devices

    Page(s): 259 - 261
    Save to Project icon | PDF file iconPDF (60 KB)  

    Aluminum-doped zinc oxide (AZO) thin films (∼3000 Å) with low electrical resistivity and high optical transparency have been grown by pulsed-laser deposition on glass substrates without a postdeposition anneal. Films were deposited at substrate temperatures ranging from room temperature to 400 °C in O2 partial pressures ranging from 0.1 to 50 mTorr. For 3000-Å-thick AZO films grown at room temperature in an oxygen pressure of 5 mTorr, the electrical resistivity was 8.7×10-4 Ω cm and the average optical transmittance was 86% in the visible range (400–700 nm). For 3000-Å-thick AZO films deposited at 200 °C in 5 mTorr of oxygen, the resistivity was 3.8×10-4 Ω cm and the average optical transmittance in the visible range was 91%. AZO films grown at 200 °C were used as an anode contact for organic light-emitting diodes. The external quantum efficiency measured from these devices was about 0.3% at a current density of 100 A/m2. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Time-resolved photoresponse of a gallium-doped germanium photoconductor using a variable pulse-width terahertz source

    Page(s): 262 - 264
    Save to Project icon | PDF file iconPDF (56 KB)  

    Picosecond to nanosecond-wide terahertz pulses are used to study the fast photoresponse of a gallium-doped germanium (Ge:Ga) photoconductor operating at 4.2 K. A recombination time of about 2 ns is observed in the time-resolved photoresponse. Laser-activated semiconductor reflection switches are used to “slice” the variable-width terahertz pulses from the quasicontinuous-wave output of a free-electron laser. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Relative electrical resistivities and poling of nonlinear optical polymeric waveguides

    Page(s): 265 - 267
    Save to Project icon | PDF file iconPDF (50 KB)  

    A method based on Maker fringe measurements of nonlinear optical coefficients has been used to determine the relative dc electrical resistivities of a series of linear and nonlinear optical polymers. The method can be used to identify low resistivity linear cladding materials for optimized electric field poling of nonlinear optical polymeric waveguides. As an example of the application of the technique we have studied the resistivity of poly(methyl methacrylate)-polystyrene (PMMA-PS) copolymers with varying content of the two components. The resistivity of PMMA was found to be one order of magnitude lower than that of PS. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Photonic-crystal spot-size converter

    Page(s): 268 - 270
    Save to Project icon | PDF file iconPDF (202 KB)  

    We have demonstrated a spot-size converter (SSC) that is made of photonic crystals (PCs) and has a conversion ratio of 10:1 for a 1-μm-wavelength light beam. Its real-spatial distribution was narrowed by intentionally broadening its wave vector distribution and increasing effective refractive index. The advantage of this PC-based SSC over conventional bulk-based SSC are compactness (monolithic integration), positional independence, and extremely deep depth of focus. This PC-SSC is a candidate for an interface between photonic-crystal waveguides and conventional optical waveguides. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • (GaIn)(NAs)/GaAs vertical-cavity surface-emitting laser with ultrabroad temperature operation range

    Page(s): 271 - 272
    Save to Project icon | PDF file iconPDF (30 KB)  

    The temperature dependence of the emission of a (GaIn)(NAs)/GaAs vertical-cavity surface-emitting laser is investigated. We find laser emission over an extremely broad temperature range from 30 K up to 388 K. The laser threshold varies from 5 kW/cm2 at 373 K down to a minimum of 1 kW/cm2 at 180 K and increases again to 4 kW/cm2 at 30 K. Picosecond emission dynamics after femtosecond optical excitation is obtained with peak delays below 33 ps and pulse widths below 20 ps over the entire operation range. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Selective area deposited blue GaN–InGaN multiple-quantum well light emitting diodes over silicon substrates

    Page(s): 273 - 275
    Save to Project icon | PDF file iconPDF (81 KB)  

    We report on fabrication and characterization of blue GaN–InGaN multi-quantum well (MQW) light-emitting diodes (LEDs) over (111) silicon substrates. Device epilayers were fabricated using unique combination of molecular beam epitaxy and low-pressure metalorganic chemical vapor deposition growth procedure in selective areas defined by openings in a SiO2 mask over the substrates. This selective area deposition procedure in principle can produce multicolor devices using a very simple fabrication procedure. The LEDs had a peak emission wavelength of 465 nm with a full width at half maximum of 40 nm. We also present the spectral emission data with the diodes operating up to 250 °C. The peak emission wavelengths are measured as a function of both dc and pulse bias current and plate temperature to estimate the thermal impedance. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Switching dynamics between single-mode and dual-mode pulse emissions from a self-seeded laser diode

    Page(s): 276 - 278
    Save to Project icon | PDF file iconPDF (65 KB)  

    Spectrally selected, self-seeded pulses are generated from a Fabry–Perot laser diode in an external cavity containing a two-chromatic fiber grating. Electrical switching between single-mode and dual-mode operations is demonstrated by controlling the amplitude of the ac signal applied to the laser diode. The principle is based on carrier induced frequency chirp that determines the spectral overlap of the Fabry–Perot modes with the grating reflection band during the pulse buildup time. We also investigate the switching dynamics and show that the steady states can be reached after about five to six round-trip cycles. The buildup of single-mode emissions is slightly faster than that of the dual mode. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Intracavity lens for low-divergence high-power laser diode operation

    Page(s): 279 - 281
    Save to Project icon | PDF file iconPDF (100 KB)  

    An intracavity lens has been integrated into a high-power tapered ridge-waveguide semiconductor laser diode. The lens is designed to compensate for the phase curvature of the incident mode on the output facet. This has led to improved linearity in the light–current characteristics of the device, showing an increase of up to 47% in power slope efficiency and a reduction of up to 17% in the full width at e-2 intensity of the far field pattern. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A wavelength multiplexer using cascaded three-dimensional vertical couplers

    Page(s): 282 - 284
    Save to Project icon | PDF file iconPDF (106 KB)  

    A four-channel wavelength multiplexer/demultiplexer for sparse wavelength division multiplexing was demonstrated using cascaded three-dimensional (3D) vertical couplers. 17 nm channel spacing with crosstalk less than 15 dB was achieved. Strong coupled vertical couplers were fabricated using wafer bonding to invert a conventionally processed epitaxial layer and bond to a new host substrate. This technology makes the fabrication of 3D photonic integrated circuits and the realization of multilevel optical interconnects possible. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fused hollow cathode cold atmospheric plasma

    Page(s): 285 - 287
    Save to Project icon | PDF file iconPDF (189 KB)  

    A fused hollow cathode (FHC) plasma source is introduced. The system of radio-frequency (rf) generated hollow cathodes with flowing gas forms an integrated electrode source which operates in the pressure range from 1 Torr to atmospheric pressure. The diameter of the source is 3.5 cm. However, the construction perfectly enables further scaling up. The forward rf power to sustain the discharge at atmospheric pressure can be as low as 2 W. The discharge is stable, volume filling, silent, with no streamers. The FHC atmospheric plasma source is very promising for surface processing, specially on temperature sensitive substrates, and may substantially save costs by avoiding investments into the vacuum equipment. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An atmospheric pressure plasma source

    Page(s): 288 - 290
    Save to Project icon | PDF file iconPDF (83 KB)  

    An atmospheric pressure plasma source operated by radio frequency power has been developed. This source produces a unique discharge that is volumetric and homogeneous at atmospheric pressure with a gas temperature below 300 °C. It also produces a large quantity of oxygen atoms, ∼5×1015cm-3, which has important value for materials applications. A theoretical model shows electron densities of 0.2–2×1011cm-3 and characteristic electron energies of 2–4 eV for helium discharges at a power level of 3–30 W cm-3. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Refractive index and gap energy of cubic InxGa1-xN

    Page(s): 291 - 293
    Save to Project icon | PDF file iconPDF (55 KB)  

    Spectroscopic ellipsometry studies have been carried out in the energy range from 1.5 to 4.0 eV in order to determine the complex refractive indices for cubic InGaN layers with various In contents. The films were grown by molecular-beam epitaxy on GaAs(001) substrates. By studying GaN films, we prove that for the analysis of optical data, a parametric dielectric function model can be used. Its application to the InGaN layers yields, in addition, the composition dependence of the average fundamental absorption edge at room temperature. From the latter, a bowing parameter of 1.4 eV is deduced. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Straight β-SiC nanorods synthesized by using C–Si–SiO2

    Page(s): 294 - 296
    Save to Project icon | PDF file iconPDF (569 KB)  

    Straight beta-silicon carbide nanorods have been grown on silicon wafers using hot filament chemical vapor deposition with iron particles as catalyst. A plate made of a C–Si–SiO2 powder mixture was used as carbon and silicon sources. Hydrogen, which was the only gas fed into the deposition system, acts both as a reactant and as a mass transporting medium. The diameter of the β-SiC nanorod ranged from 20 to 70 nm, while its length was approximately 1 μm. A growth mechanism of beta-silicon carbide nanorods was proposed. The field emission properties of the beta-silicon carbide nanorods grown on the silicon substrate are also reported. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Tl incorporation in InSb and lattice contraction of In1-xTlxSb

    Page(s): 297 - 299
    Save to Project icon | PDF file iconPDF (54 KB)  

    Ternary In1-xTlxSb thin films are grown by low pressure metalorganic chemical vapor deposition in the high In composition region. Infrared photoresponse spectra of the In1-xTlxSb epilayers show a clear shift toward a longer wavelength compared to that of InSb. Tl incorporation is confirmed by Auger electron spectroscopy. In contrast to the theoretical expectation, high resolution x-ray diffraction study reveals that the lattice of the In1-xTlxSb epilayers is contracted by the incorporation of Tl. As more Tl is incorporated, the lattice contraction is observed to increase gradually in the experimental range. A possible origin of this phenomenon is discussed. Our experimental results suggest that the Tl incorporation behavior in In1-xTlxSb differs from that of other group III impurities in III antimonides. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effect of dopant atoms on the roughness of III–V semiconductor cleavage surfaces

    Page(s): 300 - 302
    Save to Project icon | PDF file iconPDF (341 KB)  

    We demonstrate that the presence of dopant atoms influences the roughness, morphology, and optical mirror properties of III–V semiconductor (110) cleavage surfaces. High concentrations of Te dopant atoms in GaAs lead to macroscopically curvatured (110) cleavage surfaces with high step concentrations. This “glass-like” fracture behavior is explained by the “lattice superdilation phenomenon” induced by high concentrations of Te dopant atoms in GaAs. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Formation of crystalline Ba-ferrite phase from α-Fe2O3 phase in amorphous precursor

    Page(s): 303 - 305
    Save to Project icon | PDF file iconPDF (204 KB)  

    The formation of crystalline Ba-ferrite/sapphire(001) films in an amorphous precursor during annealing was studied in a real-time synchrotron x-ray scattering experiment. From the x-ray integrated intensity and the surface morphology, we found that the crystalline Ba-ferrite phase was formed by solid phase transformation of the intermediate crystalline α-Fe2O3 phase, not by direct crystallization of the amorphous precursor. The solid phase transformation occurred at temperature above 500 °C. The high crystallization temperature of the Ba-ferrite phase was attributed to the activation barrier for the diffusion of Ba ions into the α-Fe2O3 phase. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Step-bunching instability in strained-layer superlattices grown on vicinal substrates

    Page(s): 306 - 308
    Save to Project icon | PDF file iconPDF (115 KB)  

    Epitaxial structures containing either compressive or tensile InGaAsP layers separated by InP layers were grown on variously misoriented vicinal (001) InP substrates and studied by transmission electron microscopy. Except for zero misorientation, the compressive layers develop long-wavelength asymmetrical lateral thickness modulations. We demonstrate that the associated surface undulation consists of periodic bunches involving only the initial substrate steps. With increasing misorientation, the wavelength of the modulation and its phase shift between successive layers decrease, whereas its amplitude increases. On the other hand, all tensile layers develop short-wavelength localized symmetrical thickness variations often involving facets. For intermediate misorientations, they also display undulations similar to those observed in compressive layers. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • In situ transmission electron microscope studies of the kinetics of abnormal grain growth in electroplated copper films

    Page(s): 309 - 311
    Save to Project icon | PDF file iconPDF (273 KB)  

    We have performed in situ transmission electron microscopy studies of abnormal grain growth in electroplated copper films at room temperature and 55 °C, starting minutes after the plating process by electroplating directly onto electron-transparent membranes. A kinetic analysis indicates that the grains that grow abnormally, reject impurities as they grow, so that the impurities accumulate in (and must diffuse through) the untransformed matrix. This suggests that while impurities impair normal grain growth, impurity rejection contributes to the energetics that drive abnormal grain growth. This result also indicates that removal of impurities from the film can control the kinetics of the transformation to large-grained structures. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Initial growth of Ga2O3(Gd2O3) on GaAs: Key to the attainment of a low interfacial density of states

    Page(s): 312 - 314
    Save to Project icon | PDF file iconPDF (118 KB)  

    Growth of the first few layers of an oxide mixture Ga2O3(Gd2O3) on GaAs (100) substrate, electron-beam evaporated from a Ga5Go3O12 source, was found to be a single crystal. Reflection high-energy electron diffraction and x-ray diffraction studies show that the thin oxide film is epitaxially grown on GaAs with the surface normal (110) and in-plane axis [001] parallel to (100) and [011] of GaAs, respectively, and has a structure isomorphic to Mn2O3. Studies using high-resolution transmission electron microscopy on the oxide–GaAs interface indicate some atomic registry between the oxide and GaAs during the initial growth. The chemical composition of the oxide film was determined by x-ray photoelectron spectroscopy to be unequivocally pure Gd2O3. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • X-ray microdiffraction study of Cu interconnects

    Page(s): 315 - 317
    Save to Project icon | PDF file iconPDF (223 KB)  

    We have used x-ray microdiffraction to study the local structure and strain variation of copper interconnects. Different types of local microstructures have been found in different samples. Our data show that the Ti adhesion layer has a very dramatic effect on Cu microstructure. Strain measurement was conducted before and after electromigration test, Cu fluorescence was used to find the mass variations around voids and hillocks, and x-ray microdiffraction was used to measure the strain change around that interested region. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Stimulated emission study of InGaN/GaN multiple quantum well structures

    Page(s): 318 - 320
    Save to Project icon | PDF file iconPDF (119 KB)  

    We report the study results of an InGaN/GaN multiple quantum well structure with a nominal indium content of 25%. The high-resolution transmission electron microscopy and x-ray diffraction show clear indium aggregation and phase separation. Stimulated emission data always show two major peaks in spectrum. The long- (short-) wavelength peak is assigned to the recombination of localized state carriers (free carriers). At low temperatures or optical pump levels, the localized-state recombination dominates the stimulated emission; however, at high temperatures or pump levels, the free-carrier recombination becomes dominant. The peak position corresponding to localized states changes little in spectrum as temperature or pump level varies. This result is attributed to carrier overflow, strain relaxation, and carrier shielding in increasing temperature or carrier supply. © 2000 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

Applied Physics Letters, published by the American Institute of Physics, features concise, up-to-date reports on significant new findings in applied physics.

Full Aims & Scope

Meet Our Editors

Editor
Nghi Q. Lam
Argonne National Laboratory