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Selected Topics in Quantum Electronics, IEEE Journal of

Issue 4 • Date July-Aug. 2011

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Displaying Results 1 - 25 of 46
  • Table of contents

    Page(s): C1
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  • IEEE Journal of Selected Topics in Quantum Electronics publication information

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  • Table of contents

    Page(s): 761 - 762
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  • Introduction to the Issue on Nanowires

    Page(s): 763 - 765
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    The invited and contributed papers in this issue on nanowires cover the following topics: growth, synthesis, and fabrication; electrical and optical properties; theory, modeling, and simulations; light-emitting diodes and lasers; photodetectors and solar cells; and other photonic devices including sensors. View full abstract»

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  • Tailoring GaAs, InAs, and InGaAs Nanowires for Optoelectronic Device Applications

    Page(s): 766 - 778
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    GaAs, InAs, and InGaAs nanowires each exhibit significant potential to drive new applications in electronic and optoelectronic devices. Nevertheless, the development of these devices depends on our ability to fabricate these nanowires with tight control over critical properties, such as nanowire morphology, orientation, crystal structure, and chemical composition. Although GaAs and InAs are related material systems, GaAs and InAs nanowires exhibit very different growth behaviors. An understanding of these growth behaviors is imperative if high-quality ternary InGaAs nanowires are to be realized. This report examines GaAs, InAs, and InGaAs nanowires, and how their growth may be tailored to achieve desirable material properties. GaAs and InAs nanowire growth are compared, with a view toward the growth of high-quality InGaAs nanowires with device-accessible properties. View full abstract»

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  • Growth and Characterization of ZnSe/CdSe Multiquantum Disks

    Page(s): 779 - 784
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    The authors report the growth of high-density ZnSe/CdSe multiquantum disks on oxidized Si substrate. It was found the as-grown nanotips were tapered with the mixture of cubic zinc blende and hexagonal wurtzite structures. Also, photoluminescence intensities observed from these ZnSe/CdSe multiquantum disks were much larger than that observed from the homogeneous ZnSe. Activation energies for the ZnSe/CdSe multiquantum disks with well widths Lw of 8, 12, and 16 nm were 22, 62, and 56 meV, respectively. View full abstract»

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  • {\bf SiO}_{bm x} Nanowires Grown via the Active Oxidation of Silicon

    Page(s): 785 - 793
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    Amorphous, substoichiometric silica nanowires (NWs) can be grown on gold-coated silicon wafers by high-temperature annealing in an inert ambient with a low residual O2 partial pressure, consistent with conditions required for the active oxidation of the underlying Si substrate. The vapor precursor required for NW growth is volatile SiO obtained directly from the reaction between the substrate and the residual O2. This review summarizes the important elements of SiOx NW growth under active oxidation conditions and includes some examples of more-complex multistructured SiOx NW morphologies that utilize the active oxidation process. View full abstract»

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  • InGaAs/GaAs Core–Shell Nanowires Grown by Molecular Beam Epitaxy

    Page(s): 794 - 800
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    Au-catalyzed InxGa1-xAs nanowires (NWs) and InxGa1-xAs/GaAs core-shell NWs were grown by molecular beam epitaxy on (1 1 1)B GaAs. The effects of In content, growth temperature, and V/III elemental flux ratios on NW morphology have been investigated. The structure of the NWs has been characterized by SEM and transmission electron microscopy and their optical properties by low-temperature photoluminescence. View full abstract»

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  • Low-Temperature Facile Synthesis of ZnO Rod Arrays and Their Device Applications

    Page(s): 801 - 807
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (885 KB) |  | HTML iconHTML  

    Different morphologies of ZnO rod arrays with tunable photoluminescence (PL) were synthesized by vapor-phase transport deposition. The morphology and luminescence properties of ZnO rod arrays were found to be dependent on the deposition temperature and can be further tuned by postgrowth annealing treatment. Crystalline ZnO rods with intense UV emission at room temperature (RT) can be synthesized under a relatively lower temperature of 500 °C in a conventional tube furnace. ZnO rods grown at higher or lower temperature regions, however, showed additional defect-related emissions. Besides the commonly observed green emission from vapor-deposited ZnO rods, our samples also showed broad orange-red emission centered at ca. 620 nm. The origin of the different emission bands from the ZnO rod arrays was analyzed based on the annealing treatment in conjunction with the PL characterizations. Furthermore, two prototypes of optoelectronic devices (i.e., LEDs and FETs) were fabricated based on the as-grown ZnO rods. UV electroluminescence was achieved from ZnO rod arrays/p+-Si heterojunctions at RT, and FET based a single ZnO rod showed comparable transistor properties with previous reports on the ZnO nanorods grown at higher temperatures. View full abstract»

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  • Semiconductor Alloy Nanowires and Nanobelts With Tunable Optical Properties

    Page(s): 808 - 818
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    Recent advancements in the study of alloy semiconductor nanowires (NWs) and nanobelts are reviewed with a special perspective on their applications in optoelectronics with widely tunable bandgaps. Special emphasis is on the composition-graded alloy NWs. An extremely wide range of alloy compositions (thus bandgaps) can be achieved on a single substrate in a single growth run, creating an unprecedented materials capability that is not possible with planar epitaxial growth. Applications of such unique materials in widely tunable lasers and full-spectrum solar cells are discussed. View full abstract»

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  • Gold-Free GaAs Nanowire Synthesis and Optical Properties

    Page(s): 819 - 828
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    To date, the use of gold for the synthesis of nanowires has proven to be nearly impossible to circumvent, regardless of the potential negative effects on the nanowires physical properties. In this paper, the synthesis of gallium arsenide nanowires without the use of gold as a catalyst is reviewed. The review focuses on gallium-assisted growth and selective area epitaxy, revealing the common and different growth mechanisms and resulting properties. In particular, we show how the excellent material quality results also in excellent optical properties of gold-free GaAs nanowires and related heterostructures. Finally, the perspectives for future applications are discussed. View full abstract»

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  • Crystal Phases in III--V Nanowires: From Random Toward Engineered Polytypism

    Page(s): 829 - 846
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    III-V nanowires (NWs) are promising for a wide range of applications, ranging from optics to electronics, energy, and biological sensing. The structural quality of NWs is of paramount importance for the performance of such future NW-based devices. Random structural defects and polytypism occur naturally in semiconductor NWs, but progress both on the theoretical understanding and experimental control have been achieved recently. Here, we review progress towards the realization of perfect wurtzite and zinc-blende phases in III-V NWs, eventually leading to true phase engineering in single NWs. View full abstract»

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  • GaN Nanowires Grown by Molecular Beam Epitaxy

    Page(s): 847 - 858
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    The unique properties of GaN nanowires grown by molecular beam epitaxy are reviewed. These properties include the absence of residual strain, exclusion of most extended defects, long photoluminescence lifetime, low surface recombination velocity, and high mechanical quality factor. The high purity of the nanowires grown by this method allows for controllable n-type doping. P-type doping presents more challenges but has been demonstrated in active light-emitting diode devices. The present understanding of nucleation and growth of these materials is also reviewed. View full abstract»

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  • Doping of III-Nitride Nanowires Grown by Molecular Beam Epitaxy

    Page(s): 859 - 868
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    III-nitride nanowires (NWs) were grown on Si(111) without catalyst by plasma-assisted molecular-beam epitaxy under N-rich conditions. The influence of doping on the morphology and electrical properties was investigated. The morphology as well as the density of GaN NWs changes with Si amount. For high Si fluxes, the wire density is reduced, in addition, the NWs broaden from bottom to top. By doping with Mg, the NW shape does not significantly change although the wires tend to coalesce. The photoelectric transport in GaN NWs is extremely sensitive to the NW diameter. This effect is used to determine the doping level. The free carrier concentration and mobility were also estimated using Raman measurements. For Si-doped InN NWs, a reduced NW density is observed, in comparison to the undoped counterpart. At high Si doping, the InN NW morphology is improved leading to more uniform diameter NWs. InN NWs have metallic conductance because of a high background bulk concentration and the surface electron accumulation layer. The broadening of the photoluminescence (PL) spectra as a function of Fermi level was used to determine the electron concentration in different InN NW samples. A comparison of Raman scattering and electrical measurements is also presented. View full abstract»

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  • Fabrication of Highly Ordered Silicon Nanowire Arrays With Controllable Sidewall Profiles for Achieving Low-Surface Reflection

    Page(s): 869 - 877
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    A novel and simple approach is demonstrated for fabricating silicon nanowire arrays (SNWAs) with controllable sidewall profiles. A single-step deep-reactive-ion etching (SDRIE) is used to transfer the holography patterned photoresist template to silicon or silicon-on-insulator substrates. With the SDRIE etching process, scalloping of the sidewalls can be avoided while reserving the high-mask selectivity over resist and high-etching rate. The sidewall angle of resultant patterns can be adjusted by tuning the composition of the gas mixture of the process. A modified-SDRIE process with a linearly changed gas flow is further developed to extend its capability. A post-high-energy argon plasma treatment is used to create sharp tips on the top of SNWAs and to increase the filling factor. Broadband antireflective (AR) window with a low reflectivity can be realized from tall SNWAs with high-filling factor. Depositing silicon dioxide over SNWAs can further enhance the AR performance. The position and bandwidth of the AR window can be controlled by tuning the SNWA parameters. View full abstract»

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  • Properties of GaN Nanowires Grown by Molecular Beam Epitaxy

    Page(s): 878 - 888
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    On Si(1 1 1) and Si(0 0 1), GaN nanowires (NWs) form in a self-induced way without the need for any external material. On sapphire, NW growth is induced by Ni collectors. Both types of NWs exhibit the wurtzite crystal structure and grow in the Ga-polar C-direction perpendicular to the substrate. The NW sidewalls are M-plane facets, although on the Ni-induced NWs also A-plane segments form, if the growth temperature is low. Both self-induced and collector-induced NWs are free of strain and epitaxially aligned to the substrate, but in particular the former show a significant spread in tilt and twist caused by a mostly amorphous interfacial layer of Si-N. The self-induced NWs are virtually free of extended defects, but the collector-induced NWs contain many stacking faults. The photoluminescence of the former is significantly brighter and sharper. The spectra of single, dispersed, self-induced NWs contain extremely sharp excitonic lines. Significant emission is caused by excitons bound to donors close to the surface whose binding energy is reduced compared to the bulk value. In comparison, both the microstructure and optical properties of the self-induced NWs are superior. The limited material quality of the collector-induced NWs can be explained by detrimental effects of the collector. View full abstract»

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  • Probing Ultrafast Carrier Dynamics in Silicon Nanowires

    Page(s): 889 - 895
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    We present the first ultrafast optical pump-probe spectroscopic measurements, to the best of our knowledge, on silicon nanowires (SiNWs). In this study, we performed femtosecond pump-probe measurements on vapor-liquid-solid-grown SiNWs to investigate the influence of the NW diameter, pump and probe polarizations, and pump fluence on the observed dynamics while tuning the probe wavelength below and above the indirect bandgap in Si. For smaller NW diameters, carriers were found to relax more rapidly into both extended and localized states, indicating that a surface-mediated mechanism governs the observed dynamics. The magnitude of the photoinduced transmission change exhibited strong polarization dependence, showing that optical transitions in these quasi-1D systems are highly polarized along the NW axis. Finally, density-dependent experiments revealed that the relaxation time decreases with increasing photoexcited carrier density for an above bandgap probe; however, no significant density-dependent changes in the relaxation dynamics were observed when probed below the bandgap. In short, our experiments reveal the influence of diameter, polarization, and carrier density on carrier dynamics in SiNWs, shedding light on the phenomena that govern carrier relaxation in these important nanosystems and giving insight on their future use in nanophotonic applications. View full abstract»

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  • Optical Applications of ZnO Nanowires

    Page(s): 896 - 906
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    This paper discusses different aspects of optical applications of ZnO nanowires NWs. After a description of the relevant synthesis and fabrication techniques, light-emitting diodes based on ZnO NW and NW arrays are introduced and different experimental realizations from the literature are discussed. The working principle of ZnO UV photodetectors is presented, and improvements and limitations of ZnO- NW-based dye-sensitized solar cells are discussed. Different aspects of ZnO-NW waveguides and their potential application for biological sensing are described. Finally, the current status of ZnO-NW-based UV lasers is presented. View full abstract»

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  • InSb Nanowire Field-Effect Transistors and Quantum-Dot Devices

    Page(s): 907 - 914
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    The authors present fabrication and electrical measurements of InSb nanowire field-effect transistors (FETs) and quantum dots. The devices are made on a SiO2-capped Si substrate from InSb segments of InAs/InSb heterostructured nanowires, which are grown by metalorganic vapor phase epitaxy. For the FETs, both single- and dual-gate devices are fabricated. The Si substrate is employed as the back gate in both the single- and dual-gate devices, while a top metal gate is employed as a second gate in the dual-gate devices. This top gate is made either as a global gate or as a local finger gate by using a thin HfO2 layer grown by atomic layer deposition as a gate dielectric. The measurements reveal that the fabricated devices show the desired transistor characteristics. The measurements also demonstrate the possibility of realizing ambipolar transistors using InSb nanowires. For InSb nanowire quantum dots, both contact-induced Schottky-barrier-defined devices and top-finger-gate-defined devices are fabricated, and the Si substrate is used as a gate to tune the electron number in the quantum dots. The electrical measurements of these fabricated quantum-dot devices show the Coulomb-blockade effect at 4.2 K. A Fabry-Perot-like interference effect is also observed in a Schottky-barrier-defined quantum device. The authors also discuss in a comparative way, the results of measurements for the InSb nanowire devices made by different fabrication technologies employed in this study. View full abstract»

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  • Nonlinear Optical Properties of Semiconductor Nanowires

    Page(s): 915 - 921
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    The orientation dependency of nonlinear optical effects, including the second-harmonic generation (SHG) and third-harmonic generation (THG), as well as two-photon luminescence, in semiconductor nanowires (NW) are described. The mismatch of dielectric constants between nanostructures and their environment governs the rise of optical nonlinearities causing SHG even in materials with a high symmetry crystal lattice that would not generate second harmonic in the bulk state. Due to the depolarization effects, the intensity of the optical electric field inside illuminated NWs depends dramatically on their orientation related to the exciting light polarization. As a result, rotation of the light polarization causes giant angular dependency of all the mentioned optical phenomena, with the maximum relative amplitude at the electric-field polarization oriented along the NWs. Simultaneous measurements of two-photon-induced luminescence, SHG and THG in ZnSe NWs are presented. In accordance with the theory, the angular dependencies of nonlinear phenomena were observed and influence of the environmental dielectric constant on the magnitude of the nonlinear signals was demonstrated. The relative amplitudes of the angular dependencies were also significantly influenced by NW bending and nonuniformity. View full abstract»

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  • GaAs and InAs Nanowires for Ballistic Transport

    Page(s): 922 - 934
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    Tailoring of GaAs and InAs nanowires (NWs) to be suited for measurements of ballistic transport is discussed in this paper. Methods used to avoid imperfections most harmful for the transport properties are described. We consider the imperfections, which frequently occur in III-V NWs: occasional stacking faults, unintentional impurities (like gold atoms originating from the catalyst in the vapor-liquid-solid growth method) and imperfections associated with the NW side facets. Foremost important is obtaining GaAs and InAs NWs, in which either a pure wurtzite or pure zinc-blende structure is enforced, i.e., overcoming the inherent tendency of the two structures to intermix in III-V NWs. Next follows elimination, or at least minimization of the number of incorporated impurities. In InAs NWs, this has been achieved by using low-growth temperature combined with a low-growth rate. Finally, embedding the NWs in an in situ grown shell has provided a robust way for passivation of the surface states and keeping the electrons away from any impurities adhered to the surface. View full abstract»

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  • Theoretical Analysis of a Surface Plasmonic Waveguide With a Double-Petal-Shaped Air Core

    Page(s): 935 - 941
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    A kind of surface plasmonic waveguide (SPW) with a double-petal-shaped air core is designed. The propagation properties of the fundamental mode supported by this waveguide on geometrical parameters and working wavelengths are analyzed by using the finite-difference frequency-domain method. Results show that the longitudinal energy flux density is mainly distributed in the two wedged corners formed by the air core. The propagation length, effective index and mode area of the fundamental mode can be adjusted by the shape of petal-type air cores. With certain geometric parameters, relative to the case of 632.8 nm, the propagation length becomes large under the condition of larger working wavelength. A comparison of SPW proposed here and SPW with double elliptical air cores has been carried out, and results show that the SPW with a double-petal-shaped air core not only has no sharp tips, but also has better propagation properties than that of double-elliptical air cores under certain conditions. When the core is filled with gain medium, it is found that the propagation length can be extended obviously with the help of the gain dielectric medium. This kind of SPW can be applied to the field of nanoscale circuits and sensors. View full abstract»

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  • Comprehensive Numeric Study of Gallium Nitride Light-Emitting Diodes Adopting Surface-Plasmon-Mediated Light Emission Technique

    Page(s): 942 - 951
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    The coupling of quantum well (QW) spontaneous emissions to surface plasmons (SPs) has been a promising technique to increase emission rate of LEDs. We carried out numeric investigations to explore the electromagnetic nature of these SP modes. It has been shown that the SP resonance frequency on a flat silver/GaN interface, and hence the corresponding emission enhancement factor can be easily tuned by altering the thickness of silver film and the separation between QW and metal. By using coupled SPPs, partial energy transfer across silver film can be achieved, where strong directional light emission can be re-emitted. We also utilized semiconductor simulation technique to investigate the internal operations of our proposed LED. We found that the internal inefficiency of the device might be attributed to the current crowding effect, poor carrier injection, as well as bad overlap of electron and hole wave functions inside the well. The combination of electromagnetic and semiconductor simulation techniques has been presented as a powerful tool in theoretical analysis of SP-mediated emission LED. View full abstract»

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  • Rigorous Full-Vectorial Solutions of Photonics Nanowires

    Page(s): 952 - 959
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    The full-vectorial H and E-fields and Poynting vector profiles are calculated by using a rigorous full-vectorial formulation for silicon and gold nanowires. This paper reveals that the mode profiles of both circular silicon and gold nanowires are not circular, due to strong index contrast at the core-cladding interfaces. The modes are highly hybrid with all the six components of the electric, and magnetic fields being present along with a strong axial field component. From the analyses, the characteristics of single-mode operation and the vector field profiles of both circular and planar silicon nanowires are presented. The modal properties of zinc-oxide-coated gold nanowires are also presented in this paper. View full abstract»

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  • Growth Simulations of Self-Assembled Nanowires on Stepped Substrates

    Page(s): 960 - 965
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    The growth of self-assembled nanowires on stepped substrates is modeled by means of kinetic Monte Carlo simulations. It is found that the energy barrier at the step edges has a great effect on the formation of nanoislands on stepped substrates. As the barrier is smaller than 0.1 eV, nanowires with high aspect ratios can be obtained. The width, aspect ratio, and separation of the nanowires can be controlled flexibly by the width of the steps or terraces of the substrates. The effects of growth temperature and postgrowth annealing time on the morphology of the nanowires are studied. The nanowires are found to be more robust than the self-assembled nanoislands formed on plane substrates. Strain is shown to increase the width and decrease the aspect ratio of the nanowires. The scaled nanowire length distribution is also studied. As the coverage is larger than 0.2 ML, the distribution is apparently different from that at lower coverage, which reflects the different growth mechanisms of the nanowires at different layer thickness. View full abstract»

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Aims & Scope

Papers published in the IEEE Journal of Selected Topics in Quantum Electronics fall within the broad field of science and technology of quantum electronics of a device, subsystem, or system-oriented nature.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
John Cartledge
Queen's University