By Topic

Applied Physics Letters

Issue 20 • Date May 2001

Filter Results

Displaying Results 1 - 25 of 53
  • Issue Cover

    Page(s): c1
    Save to Project icon | PDF file iconPDF (23 KB)  
    Freely Available from IEEE
  • Issue Table of Contents

    Page(s): toc1
    Save to Project icon | PDF file iconPDF (27 KB)  
    Freely Available from IEEE
  • High-quality porous-silicon buried waveguides

    Page(s): 3003 - 3005
    Save to Project icon | PDF file iconPDF (322 KB)  

    This letter reports a method to produce porous-silicon waveguides by means of a laser local oxidation process. The estimated losses of the waveguides are below 1 dB/cm. This demonstrates the applicability of this material in integrated optics and telecommunications. Moreover, our results disclose the opportunity to integrate optoelectronic devices onto Si substrates. The laser writing method is achievable at low laser power, thus it is highly efficient and achievable with the standard equipment present in most laboratories. Another advantage is that oxidation is achieved without heating the complete chip, thus simplifying the integration process, i.e., the oxidation is inherently local through the direct-write process. This method opens the opportunity to build microstructures, like channel and membrane filters, in a flexible manner by R&D laboratories. © 2001 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Simultaneously efficient blue and red light generations in a periodically poled LiTaO3

    Page(s): 3006 - 3008
    Save to Project icon | PDF file iconPDF (41 KB)  

    Generations of efficient blue light at 447 nm and red light at 671 nm were achieved by frequency doubling and tripling of a diode-pumped, Q-switched 1342 nm Nd:YVO4 laser with a periodically poled LiTaO3 (PPLT). The blue light at 447 nm was generated by sum-frequency mixing of the fundamental at 1342 nm with the generated second harmonic at 671 nm. The first-order and third-order reciprocals of the PPLT compensated the phase mismatches of second-harmonic and sum-frequency processes, respectively, making them quasiphase matched. The resulting averaged blue light power of 51 mW and red light power of 207 mW under the averaged fundamental power of 500 mW indicate that the PPLT may be used to construct an all-solid-state blue and red dual wavelength laser. © 2001 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 spectra of (GaIn)(NAs) laser diodes for the 1.3-μm-wavelength regime

    Page(s): 3009 - 3011
    Save to Project icon | PDF file iconPDF (56 KB)  

    Optical gain spectra of (GaIn)(NAs)/GaAs quantum-well lasers operating in the 1.3-μm-emission-wavelength regime are measured and compared to those of a commercial (GaIn)(AsP)/InP structure. Good agreement of the experimental results with computed spectra of a microscopic many-body theory is obtained. Due to the contributions of a second confined subband, a spectrally broad gain region is expected for (GaIn)(NAs)/GaAs at elevated carrier densities. © 2001 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Angle-dependent photocurrent spectroscopy of oxide-apertured vertical-cavity surface-emitting lasers during aging

    Page(s): 3012 - 3014
    Save to Project icon | PDF file iconPDF (45 KB)  

    Aging properties of oxide-apertured vertical-cavity surface-emitting lasers have been analyzed by photocurrent (PC) measurements at room temperature. We demonstrate that this method allows an analysis of the aging process and provides insight into degradation mechanisms occurring during operation of these devices. By changing the angle of incidence in the PC experiment the energy positions of the top mirror features shift to higher energy while the excitonic transitions do not change. Thus, angle dependent PC spectra reveal both the appearance of defect bands located in the intrinsic region of the device as well as modifications of the top mirror transmission upon aging. © 2001 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Strain-tunable photonic band gap crystals

    Page(s): 3015 - 3017
    Save to Project icon | PDF file iconPDF (89 KB)  

    We have designed a two-dimensional strain-tunable photonic band gap crystal by distorting the symmetry of the crystal from a regular hexagonal to a quasihexagonal lattice by means of field driven strain using a piezoelectric material. Calculations predict that the original high symmetry energy bands split up into several strained energy bands depending on the magnitude and direction of the strain. In the proposed structures, we show that 2% (3%) shear strain can be used to tune ∼52% (73%) of the original undistorted absolute band gap of a two-dimensional photonic band gap crystal. These device structures can be used for optical switching and modulation. © 2001 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Spatial control of second-order optical susceptibility induced in thermally poled glasses

    Page(s): 3018 - 3020
    Save to Project icon | PDF file iconPDF (108 KB)  

    Second-order susceptibility thermally induced in poled glass samples was erased in doped borophosphate, lead silica, and fused silica glasses using an optical method. A simple law describes the temporal evolution and the spatial profile of the erased nonlinear region versus the intensity and profile of the erasure laser beam. A comparison is made between one and two photon absorption induced spatial profiles. © 2001 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Enhancement of second-harmonic generation in a one-dimensional semiconductor photonic band gap

    Page(s): 3021 - 3023
    Save to Project icon | PDF file iconPDF (262 KB)  

    We demonstrate significant enhancement of second-order nonlinear interactions in a one-dimensional semiconductor Bragg mirror operating as a photonic band gap structure. The enhancement comes from a simultaneous availability of a high density of states, thanks to high field localization, and the improvement of effective coherent length near the photonic band edge. © 2001 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Submicron three-dimensional infrared GaAs/AlxOy-based photonic crystal using single-step epitaxial growth

    Page(s): 3024 - 3026
    Save to Project icon | PDF file iconPDF (331 KB)  

    A relatively simple technique is demonstrated to fabricate three-dimensional face-centered-cubic infrared photonic crystals with submicron feature sizes using GaAs-based technology, single-step epitaxial growth, and lateral wet oxidation. The photonic crystals were fabricated with feature sizes (a) of 1.5 and 0.5 μm. Transmission measurements reveal a stopband centered at 1.0 μm with a maximum attenuation of 10 dB for the submicron (a=0.5 μm) photonic crystal. This technique is scalable to small photonic crystal periodicity and hence to shorter wavelengths. © 2001 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electrode sheath voltage in pulsed high-pressure mercury arcs

    Page(s): 3027 - 3028
    Save to Project icon | PDF file iconPDF (43 KB)  

    The electric field strength and the electrode sheath voltage in high-pressure mercury arcs were experimentally determined for operation in a current-pulse mode. The current was sinusoidally alternating with a basic frequency of 50 Hz. Each fifth half cycle was pulsed with different ratios of the maximum current in the pulse to those in the other four half cycles. The experimental results quite well agree with model calculations considering radiation transport. The most impressive feature of the electrode sheath voltage is a very pronounced minimum immediately after the reignition peak which can reach high negative values. © 2001 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electric field modulation spectroscopy by scanning tunneling microscopy with a nanometer-scale resolution

    Page(s): 3029 - 3031
    Save to Project icon | PDF file iconPDF (262 KB)  

    Instrumentation has been devised by coupling electric field modulation spectroscopy (EFMS) with scanning tunneling microscopy (STM) that enables the investigation of electronic band structures in semiconductors with a nanometer-scale spatial resolution. Model experiments using low-temperature-grown GaAs (LT–GaAs) epifilms show that a difference as small as 0.01 eV in electronic energy gaps between the GaAs substrate and the LT–GaAs epilayers can be distinguished in the EFMS spectra, demonstrating the high energy, as well as spatial, resolution of the STM–EFMS. © 2001 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electronic properties of α-Sn(100)2×1: Evidence for asymmetric dimer reconstruction

    Page(s): 3032 - 3034
    Save to Project icon | PDF file iconPDF (58 KB)  

    A well-ordered thick layer of α-Sn(100) has been grown on InSb(100). The low energy electron diffraction pattern showed a sharp 2×1 double domain reconstruction with very low background at room temperature. The electronic properties have been studied by core-level- and angle-resolved photoemission spectroscopy (ARPES). ARPES spectra showed the presence of a surface state at normal emission, 1.15 eV below the Fermi level. This state disperses downward 1.3 eV along the [010] direction. Core-level spectra are well fitted with three surface-shifted components at binding energies +0.22, -0.23, and -0.49 eV with respect to the bulk component. Such results are in agreement with theoretical calculations based on asymmetric dimers by [Z.-Y. Lu, G. Chiarotti, S. Scandolo, and E. Tosatti, Phys. Rev. B 58, 13698 (1998)], taking into account final state effects, and exclude the existence of symmetric dimers. © 2001 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Zone-folding effect on optical phonon in GaN/Al0.2Ga0.8N superlattices

    Page(s): 3035 - 3037
    Save to Project icon | PDF file iconPDF (51 KB)  

    Optical properties of GaN/Al0.2Ga0.8N superlattices have been investigated by Raman scattering and photoluminescence measurements. It is found that the A1(LO) phonon decreases in frequency with decreasing quantum-well width. The frequency shift is attributed to the effect of phonon zone folding. Through the study of photoluminescence, we show that our observation of the zone-folding effect on optical phonon in GaN/Al0.2Ga0.8N superlattices is due to the sharpness of the interfaces between barrier and well layers. The sharp interfaces prevent the appearance of mixed interface modes which mask the phonon effect of zone folding in previous reports. © 2001 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Surfactant effects on doping of GaAs grown by organometallic vapor phase epitaxy

    Page(s): 3038 - 3040
    Save to Project icon | PDF file iconPDF (45 KB)  

    Recently, the addition of the isoelectronic surfactant Sb during organometallic vapor phase epitaxy (OMVPE) of GaInP was shown to eliminate ordering, resulting in a significant change in the band gap energy. These results suggest that surfactants added during growth could have profound affects on other important properties of semiconductors, such as doping. This letter presents the results of a recent study on the effects of the isoelectronic surfactant Sb on doping in GaAs. The addition of a small amount of triethylantimony during OMVPE of GaAs is found, using secondary ion mass spectroscopy analysis, to increase the Zn doping concentration from ≪6×1018 atoms/cm3 to 9×1018 atoms/cm3, a factor of 1.6. The amount of antimony introduced into the solid is only 2–3×1017 atoms/cm3. The addition of Sb also increases the impurity concentration of In in GaAs, but does not affect the concentration of Te or P. © 2001 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Yellow and green luminescence in a freestanding GaN template

    Page(s): 3041 - 3043
    Save to Project icon | PDF file iconPDF (53 KB)  

    We have studied a broad photoluminescence band in high-mobility freestanding 200-μm-thick GaN template prepared by hydride vapor-phase epitaxy. Variable-excitation intensity and energy experiments showed two defect-related bands: a yellow luminescence (YL) band at about 2.15 eV and a green luminescence (GL) band at about 2.43 eV. In contrast to epitaxial GaN samples prepared by both vapor-phase and molecular-beam epitaxy, the YL in the sample studied is weak and can be easily saturated. However, the GL is dominant. We attribute the GL to isolated defects involving gallium vacancies and the YL to the same defect, but bound to dislocations, or possibly to structural surface defects. © 2001 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Linear growth of thin films under the influence of stress

    Page(s): 3044 - 3046
    Save to Project icon | PDF file iconPDF (65 KB)  

    We have studied the growth of thin films in the presence of stress instability that enhances the roughness and roughening induced by conservative as well as nonconservative noise. It is clearly illustrated that nonconservative noise effects may enhance stress induced roughness. Nevertheless, the incorporation of conservative noise appears to also be substantial in growth processes driven by diffusion. For growth on a rough substrate the dependence of the amplitude of the surface roughness on the film thickness differs from that of a film growing on a flat substrate. The amplitude shows a minimum at a particular substrate thickness, which indicates that the growth up to this thickness is enforced by undulations of the substrate. © 2001 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Switchable mirrors based on nickel–magnesium films

    Page(s): 3047 - 3049
    Save to Project icon | PDF file iconPDF (135 KB)  

    An electrochromic mirror electrode based on reversible uptake of hydrogen in nickel magnesium alloy films is reported. Thin, magnesium-rich Ni–Mg films prepared on glass substrates by co-sputtering from Ni and Mg targets are mirror-like in appearance and have low visible transmittance. Upon exposure to hydrogen gas or on cathodic polarization in alkaline electrolyte, the films take up hydrogen and become transparent. When hydrogen is removed, the mirror properties are recovered. The transition is believed to result from reversible formation of Mg2NiH4 and MgH2. A thin overlayer of palladium was found to enhance the kinetics of hydrogen insertion and extraction, and to protect the metal surface against oxidation. © 2001 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 29Si magic-angle-spinning nuclear-magnetic-resonance study of spinel-type Si3N4

    Page(s): 3050 - 3051
    Save to Project icon | PDF file iconPDF (35 KB)  

    29Si magic-angle-spinning nuclear-magnetic resonance has been measured on spinel-type cubic silicon nitride (c-Si3N4). c-Si3N4 shows two 29Si resonances at -50.0±0.2 and -225.0±0.2 ppm, corresponding to the tetrahedron SN4 and the octahedron SiN6, respectively. Integration of the spectrum gives SN4/SiN6 about one half that of the spinel structure. Ab initio self-consistent field Hartree–Fock molecular orbital calculations also indicate that the chemical shift for octahedral Si is more negative in nitride than in oxides. © 2001 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Wetting layer carrier dynamics in InAs/InP quantum dots

    Page(s): 3052 - 3054
    Save to Project icon | PDF file iconPDF (136 KB)  

    The electronic coupling between InAs/InP quantum dot (QD) array and its wetting layer (WL) is studied by continuous wave and time resolved photoluminescence. The carrier dynamics is explained by the existence of two regimes in the WL: at low QD density the carrier dynamics is dominated by the diffusion and at high density when the distance between QDs is comparable to the carrier mean free path in the WL the quantum capture into QDs dominates. From the identification of these two regimes the carrier mean free path in the WL is estimated to about 30 nm. © 2001 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Surface alignment bistability of nematic liquid crystals by orientationally frustrated surface patterns

    Page(s): 3055 - 3057
    Save to Project icon | PDF file iconPDF (159 KB)  

    We demonstrate a robust in-plane bistability of liquid-crystal surface alignment based on tailored submicrometer-sized surface domains imposing a frustrated alignment. By a nanorubbing technique utilizing the atomic force microscope, we prepared an orientational checkerboard pattern on polyimide layer, consisting of square unit domains on which the alignment is locally constrained to be planar yet orthogonal between the neighboring domains. Due to the four-fold rotational symmetry of the pattern, the two diagonal axes of the square domain become equally stable directions for the macroscopic liquid crystal alignment. The alignment could be switched between these two states by an in-plane electric field above a certain threshold, determined by the local azimuthal anchoring. © 2001 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Si-rich/SiO2 nanostructured multilayers by reactive magnetron sputtering

    Page(s): 3058 - 3060
    Save to Project icon | PDF file iconPDF (367 KB)  

    Silicon-rich (SR)/SiO2 multilayered systems were produced by reactive magnetron sputtering, through an approach based on the ability of hydrogen, when alternatively mixed to the argon of the plasma, to reduce the oxygen originated from the SiO2 target. Optimum values of both hydrogen partial pressure (45 mTorr) and deposition temperature (500 °C) have led to the highest incorporation of Si in the SR layer which crystallizes after annealing. The SR/SiO2 superlattices grown with such conditions showed that the size of the Si nanocrystals is limited by the thickness of the SR layer. Considering the difference observed between the photoluminescence peak position and the predicted band gap for Si nanocrystals, the results suggest that we deal with a quantum-size confinement assisted by a Si–O vibration located at the interface. © 2001 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Strong influence of supercooled liquid on crystallization of the Al85Ni5Y4Nd4Co2 metallic glass

    Page(s): 3061 - 3063
    Save to Project icon | PDF file iconPDF (48 KB)  

    The present letter aims to report the effect of supercooled liquid region on crystallization behavior of an Al85Ni5Y4Nd4Co2 metallic glass produced by rapid solidification of the melt. It is found that crystallization behaviors of this alloy above and below the glass-transition temperature are completely different. Formation of the primary nanoscale α-Al particles observed during continuous heating or after annealing above glass-transition temperature does not occur during isothermal annealing below glass-transition temperature when an unidentified intermetallic compound, and α-Al phases are formed simultaneously. © 2001 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Dielectric exchange-force effect on the rupture force of adsorbed bilayers of self-assembled surfactant films

    Page(s): 3064 - 3066
    Save to Project icon | PDF file iconPDF (144 KB)  

    We measured and formulated dielectric exchange forces between adsorbed layers of self-assembled surfactant films and atomic-force microscope tips in water. The dielectric exchange-force model is in agreement with the observation that the surfactant-layer rupture forces (tip-applied force necessary to obtain tip/substrate contact) are smaller in the thickest layers, where the compactness of the adsorbed film results in the smallest values of the dielectric permittivity. Within experimental accuracy, a dielectric permittivity value of ∼4 for bilayers and of ∼36 for monolayers is found. © 2001 American Institute of Physics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Apertured quantum dot microcavity light emitting diodes

    Page(s): 3067 - 3069
    Save to Project icon | PDF file iconPDF (44 KB)  

    Experimental data are presented showing efficiency enhancements due to size reductions of apertured quantum dot microcavity light emitting diodes. The aperture sizes are photolithographically controlled to generate four different aperture sizes that are nominally 4, 3, 2, and 1 μm diameters. Even at room temperature the efficiencies increase with decrease in aperture size. © 2001 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