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24 May 1999

Volume 74, Issue 21, pp. 3081-3230

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Collisional broadening and shift of spectral lines in quantum dot lasers

A. V. Uskov, K. Nishi, and R. Lang

Appl. Phys. Lett. 74, 3081 (1999); http://dx.doi.org/10.1063/1.124068 (3 pages) | Cited 30 times

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We estimate homogeneous broadening and shift of optical transition lines in self-assembled quantum dots (SAQD) caused by elastic Coulomb collisions of carriers in wetting layer with carriers in the SAQD. In particular, we demonstrate that the dephasing time for lasing transitions can be ∼0.1–1 ps at carrier densities in wetting layer ∼ 1015 m−2. © 1999 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.66.-w Optical properties of specific thin films
73.61.-r Electrical properties of specific thin films

Improved operational stability of polyfluorene-based organic light-emitting diodes with plasma-treated indium–tin–oxide anodes

J. S. Kim, R. H. Friend, and F. Cacialli

Appl. Phys. Lett. 74, 3084 (1999); http://dx.doi.org/10.1063/1.124069 (3 pages) | Cited 95 times

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We report the influence of various surface treatments of indium–tin–oxide (ITO) anodes on the operational stability of high-efficiency (up to 8.2 lm/W) green-emitting polymer light-emitting diodes (PLEDs), employing a doped poly(3,4-ethylene dioxythiophene), hole transport layer, a polyfluorene based emissive layer, and Ca–Al cathodes. The anodes were modified by physical (oxygen-plasma), chemical (aquaregia), and combined treatments. Oxygen plasma improves the stability under constant current with respect to all other anodes, with half-brightness (100 cd/m2) lifetimes two to five times longer than for untreated samples, and 1000 times longer than for aquaregia samples. We derive two major indications for optimization of PLEDs. First, thermal management of the diode is of the uppermost importance and there is significant scope for improvement. Second, the ITO anode and in general the electrical properties of the hole-injecting contact are crucial to device operation, even in the presence of a hole transport layer. © 1999 American Institute of Physics.
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85.60.Jb Light-emitting devices
42.70.Jk Polymers and organics
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Polarization independent phase demodulation using photorefractive two-wave mixing

Philippe Delaye, Alain Blouin, Denis Drolet, Jean-Pierre Monchalin, Louis-Anne de Montmorillon, and Gérald Roosen

Appl. Phys. Lett. 74, 3087 (1999); http://dx.doi.org/10.1063/1.124070 (3 pages) | Cited 6 times

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We describe both theoretically and experimentally a polarization independent interferometric adaptive photodetector based on photorefractive two-wave mixing. The configuration is based on the simultaneous recording of two independent gratings in a single photorefractive crystal. Applied to the detection of ultrasonic signals, this interferometric photodetector operates with depolarized beams issued from multimode fibers and gives a detection limit close to the ultimate. © 1999 American Institute of Physics.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.40.Kw Holographic interferometry; other holographic techniques
43.35.Yb Ultrasonic instrumentation and measurement techniques
42.81.Gs Birefringence, polarization
85.60.Gz Photodetectors (including infrared and CCD detectors)
43.60.Qv Signal processing instrumentation, integrated systems, smart transducers, devices and architectures, displays and interfaces for acoustic systems

Temperature-insensitive operation of real index guided 1.06 μm InGaAs/GaAsP strain-compensated single-quantum-well laser diodes

Hideki Asano, Mitsugu Wada, Toshiaki Fukunaga, and Toshiro Hayakawa

Appl. Phys. Lett. 74, 3090 (1999); http://dx.doi.org/10.1063/1.124071 (3 pages) | Cited 10 times

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Temperature-insensitive characteristics have been demonstrated in single mode 1.06 μm InGaAs single-quantum-well laser diodes grown by metalorganic vapor phase epitaxy. The large band-gap AlGaInP current blocking layer is employed in the buried-ridge laser structure. Tensile-strained GaAsP barrier layers were used for strain compensation and electron barriers for reducing electron overflow from a quantum well. As a result, almost totally temperature-insensitive light output-current characteristics have been realized. The uncoated device shows the highest record characteristics temperature of 437 K for the threshold current in the range of 20–50 °C. In addition, the slope efficiency does not change over 20–80 °C. © 1999 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Small-signal gain and iodine dissociation in a supersonic chemical oxygen–iodine laser with transonic injection of iodine

D. Furman, E. Bruins, B. D. Barmashenko, and S. Rosenwaks

Appl. Phys. Lett. 74, 3093 (1999); http://dx.doi.org/10.1063/1.124072 (3 pages) | Cited 3 times

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Measurements of the gain and temperature in the resonator of a supersonic chemical oxygen–iodine laser (COIL) with transonic injection of I2, using diode laser-based diagnostics, are reported. For conditions corresponding to the maximum chemical efficiency of this type of COIL (11.7 mmole/s of chlorine, no primary buffer gas, and 1.36 mmole/s of the secondary N2), the gain is a nonmonotonous function of the iodine flow rate. Maximum gain of 0.34%/cm is achieved for an iodine flow rate of 0.27 mmole/s. An analytical method is developed which enables the use of these dependencies for calculation of the iodine dissociation fraction F and the number N of O2(1Δ) molecules lost in the region of iodine dissociation per I2 molecule. It is found that F is a nonmonotonous function of the iodine flow rate, its maximum value being small (0.55). © 1999 American Institute of Physics.
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42.55.Ks Chemical lasers
78.60.Ps Chemiluminescence
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

Reflection from dual-domains in a holographically-formed polymer-dispersed liquid crystal material

Chris C. Bowley, Gregory P. Crawford, and Haiji Yuan

Appl. Phys. Lett. 74, 3096 (1999); http://dx.doi.org/10.1063/1.124073 (3 pages) | Cited 8 times

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A holographically-formed polymer-dispersed liquid crystal is reported with two distinctive reflective states brought about by a single laser exposure of a liquid crystal-rich emulsion. The two reflective states are the result of two structurally different domains that are formed during the holographic cure. A simple phenomenological model is presented that describes the dual-domain effect. © 1999 American Institute of Physics.
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81.05.Qk Reinforced polymers and polymer-based composites
61.30.-v Liquid crystals
81.40.Tv Optical and dielectric properties related to treatment conditions
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.70.Df Liquid crystals
42.40.My Applications
82.70.Kj Emulsions and suspensions

A simple method for optically enhancing the small electro-optical effects of fast switching electroclinic liquid crystals

H. Xu, A. B. Davey, T. D. Wilkinson, and W. A. Crossland

Appl. Phys. Lett. 74, 3099 (1999); http://dx.doi.org/10.1063/1.124074 (3 pages) | Cited 4 times

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We report a method for optically enhancing the small electro-optic effect of fast switching liquid crystals in order to allow the liquid-crystal electro-optical devices to operate at very high speed. In comparison with the method using grating-excited guided modes, this method makes device fabrication and operation much easier as the cell structure is similar to a conventional cell but with a metallic mirror coated on the bottom glass substrate. Using this method, a contrast ratio of >5 has been obtained for optical switches with an electro-optical response time of 700 ns and a field of 12 V/μm. © 1999 American Institute of Physics.
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42.79.Kr Display devices, liquid-crystal devices
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
78.20.Jq Electro-optical effects
42.82.Ds Interconnects, including holographic interconnects
85.60.-q Optoelectronic devices
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order

Design considerations and analytical approximations for high continuous-wave power, broad-waveguide diode lasers

D. Botez

Appl. Phys. Lett. 74, 3102 (1999); http://dx.doi.org/10.1063/1.124075 (3 pages) | Cited 39 times

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Accurate analytical approximations are derived for the equivalent transverse spot size, d/Γ (<5% error), and the transverse beamwidth θ1/2 (<2% error), of broad-waveguide-type diode lasers, over a wide range in waveguide width: from the first-order-mode cutoff to the third-order-mode cutoff. The analytical formulas are found to be in good agreement with experimental values. For low-series-resistance and thermal-resistance devices, it is found that the junction-temperature rise ΔTj in continuous wave (CW) operation is a strong function of both the characteristic temperature T1 for the external differential quantum efficiency ηD as well as of the heatsink thermal resistance. If the device has relatively temperature-insensitive ηD (i.e., T1≳1000 K) the maximum CW power as well as the power density at catastrophic optical mirror damage, mathCOMD, are limited, for a given active-region material, only by the heatsink heat-removal ability. For large d/Γ, 0.97 μm emitting, 100 μm stripe InGaAs/InGaAs(P)/GaAs devices with T1 = 1800 K, record-high CW and quasi-CW (100 μs wide pulses) output powers are obtained. The ratio of quasi-CW to CW mathCOMD values is only 1.3, in contrast to devices of poor carrier confinement and subsequent low-T1 values (∼140 K), for which the ratio is 1.9, and whose maximum CW powers are ∼40% less than those obtainable from high-T1 devices. © 1999 American Institute of Physics.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
42.60.Pk Continuous operation
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Piezoelectric and electro-optic coefficients of the molecular nonlinear optical crystal 2-furyl methacrylic anhydride

P. Kerkoc, S. Maruo, S. Horinouchi, and K. Sasaki

Appl. Phys. Lett. 74, 3105 (1999); http://dx.doi.org/10.1063/1.124076 (2 pages) | Cited 3 times

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Large crystals of 2-furyl methacrylic anhydride were successfully grown, making it possible to measure accurately their piezoelectric and electro-optic coefficients. Low modulation frequency electro-optic coefficients at a wavelength of 632.8 nm are: r33 = 7.1±0.4 pm/V and r13 = 4.5±0.2 pm/V, whereas the inverse piezoelectric coefficients are: d33 = 8.2±0.4 pm/V and d13 = 2.2±0.1 pm/V. © 1999 American Institute of Physics.
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42.70.Jk Polymers and organics
77.65.Bn Piezoelectric and electrostrictive constants
77.84.Jd Polymers; organic compounds
78.20.Jq Electro-optical effects
42.70.Mp Nonlinear optical crystals

Depth-resolved imaging of nematic liquid crystals by third-harmonic microscopy

D. Yelin, Y. Silberberg, Y. Barad, and J. S. Patel

Appl. Phys. Lett. 74, 3107 (1999); http://dx.doi.org/10.1063/1.124077 (3 pages) | Cited 10 times

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Third-harmonic microscopy is shown to be a powerful tool for the study of liquid crystal structures. The third-harmonic probe enables the investigation of molecular order well inside a liquid crystal cell. The observation of phase transition in various nematic liquid crystal samples is presented as a demonstration for the power of this technique. For example, nematic and isotropic regions are shown to coexist across the depth of the cell. Thermal fluctuations are observed in the nematic regions close to the isotropic–nematic transition temperature. © 1999 American Institute of Physics.
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42.70.Df Liquid crystals
61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures
64.70.M- Transitions in liquid crystals
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
07.60.Pb Conventional optical microscopes

In-plane alignment of noncentrosymmetric molecules by oblique-incidence molecular beam deposition

Bert Müller, Chengzhi Cai, Armin Kündig, Ye Tao, Martin Bösch, Matthias Jäger, Christian Bosshard, and Peter Günter

Appl. Phys. Lett. 74, 3110 (1999); http://dx.doi.org/10.1063/1.124078 (3 pages) | Cited 1 time

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The preferential orientation of noncentrosymmetric, organic molecules with intermolecular bonding is realized by means of oblique-incidence molecular beam deposition. The in-plane anisotropy in the optical properties of the thin films is shown by transmission spectra of ultraviolet light. Second-harmonic generation measurements demonstrate the preferential orientation of the molecules aligned in-plane. In addition, the dependence of the second-harmonic light intensity on the film thickness reveals the dominance of bulk effects with respect to surface contributions. Therefore, this molecular alignment technique is a promising method to produce stable thin films for applications in linear and nonlinear optics. © 1999 American Institute of Physics.
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42.70.Jk Polymers and organics
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.66.Qn Polymers; organic compounds
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
68.55.-a Thin film structure and morphology
78.20.Ek Optical activity
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.40.Me Organic compounds and polymers

Infrared and self-frequency doubled laser action in Yb3+-doped LiNbO3:MgO

E. Montoya, J. Capmany, L. E. Bausá, T. Kellner, A. Diening, and G. Huber

Appl. Phys. Lett. 74, 3113 (1999); http://dx.doi.org/10.1063/1.124079 (3 pages) | Cited 43 times

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Stable continuous-wave laser action in the near-infrared and in the green spectral region has been obtained in a self-frequency doubling solid-state laser, the Yb3+:MgO:LiNbO3 nonlinear crystal. By pumping with a Ti:sapphire laser and using a nearly concentric cavity, laser action at 1.06 μm was achieved with an absorbed power threshold of 101 mW and efficiency around 47%. As much as 60 mW of self-frequency-doubled radiation at 530 nm was also obtained with absorbed pump powers of 800 mW in critical cavity alignment. Efficient laser action was also obtained in the near-infrared region under pumping with diode laser. © 1999 American Institute of Physics.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.70.Hj Laser materials
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.By Design of specific laser systems
42.70.Mp Nonlinear optical crystals

Degenerate four-wave mixing in (Pb, La) (Zr, Ti)O3 polycrystalline film fabricated by metalorganic chemical-liquid deposition

G. H. Jin, B. Nemet, Y. L. Lu, C. Hsu, M. Cronin-Golomb, F. L. Wang, H. Jiang, and J. Zhao

Appl. Phys. Lett. 74, 3116 (1999); http://dx.doi.org/10.1063/1.124080 (3 pages) | Cited 12 times

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We have demonstrated a large photorefractive effect in thin-film polycrystalline (Pb, La) (Zr, Ti)O3 (8.5/65/35) fabricated by metalorganic chemical-liquid deposition. With an applied external electric field, this film exhibited a high photorefractive diffraction efficiency measured by degenerate four-wave mixing. Poling phenomena and depolarization processes in the film were also investigated. © 1999 American Institute of Physics.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
78.66.Nk Insulators
42.70.Gi Light-sensitive materials
78.20.Jq Electro-optical effects
77.22.Ej Polarization and depolarization
42.40.Eq Holographic optical elements; holographic gratings
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Characteristics of a barrier discharge in monatomic and molecular gases

R. Sankaranarayanan, B. Pashaie, and S. K. Dhali

Appl. Phys. Lett. 74, 3119 (1999); http://dx.doi.org/10.1063/1.124081 (3 pages) | Cited 8 times

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We show that, in a parallel-plate dielectric-barrier discharge, monatomic gases behave very differently from molecular gases. Time-resolved images show diffused discharge for monatomic gases and filamentary discharge for molecular gases. In addition, current waveforms also show a marked difference. An empirical relationship for power and voltage is derived which shows good agreement with experimental results for both monatomic and molecular gases. © 1999 American Institute of Physics.
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52.80.Tn Other gas discharges
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Stress analysis of selective epitaxial growth of GaN

Q. K. K. Liu, A. Hoffmann, H. Siegle, A. Kaschner, C. Thomsen, J. Christen, and F. Bertram

Appl. Phys. Lett. 74, 3122 (1999); http://dx.doi.org/10.1063/1.124082 (3 pages) | Cited 15 times

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Stress distributions in selectively overgrown self-organized GaN hexagonal pyramids have been analyzed by continuum elasticity theory. This has been carried out using the values for the moduli of elasticity found in the literature and an effective lattice mismatch between the GaN and the substrate that was determined from the Raman shift of the GaN buffer layer. The results of compressive stress in the buffer layer, tensile stress on the lower half of the pyramids’ facet surface, and full relaxation for approximately the upper 2/3 of the pyramids are in satisfactory agreement with the experimental observations that were deduced from cathodoluminescence microscopy and micro-Raman spectroscopy. © 1999 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
62.20.D- Elasticity
81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence

Temperature dependence of Raman scattering in single crystal GaN films

Ming S. Liu, Les A. Bursill, S. Prawer, K. W. Nugent, Y. Z. Tong, and G. Y. Zhang

Appl. Phys. Lett. 74, 3125 (1999); http://dx.doi.org/10.1063/1.124083 (3 pages) | Cited 47 times

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Micro-Raman scattering from single crystal GaN films, both free-standing and attached to Al2O3 substrates, was performed over the temperature range from 78 to 800 K. These measurements reveal that the Raman phonon frequency decreases and the linewidth broadens with increasing temperature. This temperature dependence is well described by an empirical relationship which has proved to be effective for other semiconductors. The experiments also demonstrate that the strain from Al2O3 substrates compresses the epitaxial GaN in the c-axis direction. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
68.55.-a Thin film structure and morphology
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

Optical investigation of InGaN/GaN multiple quantum wells

T. Wang, D. Nakagawa, M. Lachab, T. Sugahara, and S. Sakai

Appl. Phys. Lett. 74, 3128 (1999); http://dx.doi.org/10.1063/1.124084 (3 pages) | Cited 31 times

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Optical investigation was performed on InGaN/GaN multiple quantum well (MQW) structures with different well thicknesses. At low temperature, the excitation power dependence of the photoluminescence (PL) emission energy of a MQW with 5 nm well thickness was found to be different from that of a MQW with 2.5 nm well thickness. Their temperature dependence of the optical behaviors including the PL line shapes and the internal quantum efficiencies also showed distinct features. The optical behaviors of the quantum well with a thickness above 2.5 nm can be explained by a model based on the formation of self-organized small In-rich regions, rather than by the piezoelectric field-induced quantum-confined Stark effect. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
64.75.-g Phase equilibria
78.20.Jq Electro-optical effects

Distributed on-fiber thin film heaters for Bragg gratings with adjustable chirp

John A. Rogers, Benjamin J. Eggleton, Janet R. Pedrazzani, and Thomas A. Strasser

Appl. Phys. Lett. 74, 3131 (1999); http://dx.doi.org/10.1063/1.124085 (3 pages) | Cited 26 times

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This letter describes a fiber Bragg grating device that has tunable chirp. It relies on a distributed on-fiber resistive heater that consists of a thin metal film deposited onto the outer surface of a bare fiber; the thickness of this film varies continuously with position along the fiber. The physics of heat flow and diffusion in these structures leads to temperature gradients that follow, to a remarkably good approximation, the local resistance of the tapered metal film. This temperature distribution produces a chirp with a geometry that is defined by the thickness profile of the film and at a rate that can be adjusted by changing the current. Finite element modeling illuminates aspects of the flow of heat in these structures, and optical measurements demonstrate important characteristics of the devices. © 1999 American Institute of Physics.
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42.81.Wg Other fiber-optical devices
42.79.Dj Gratings
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
07.20.Hy Furnaces; heaters

Optical nonlinearity in low-temperature-grown GaAs: Microscopic limitations and optimization strategies

M. Haiml, U. Siegner, F. Morier-Genoud, U. Keller, M. Luysberg, R. C. Lutz, P. Specht, and E. R. Weber

Appl. Phys. Lett. 74, 3134 (1999); http://dx.doi.org/10.1063/1.124086 (3 pages) | Cited 27 times

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We have quantitatively measured the linear and the nonsaturable absorption as well as the absorption modulation and its recovery time in as-grown and annealed low-temperature (LT) GaAs. Correlation of the optical data with As antisite (AsGa) defect densities yields the absorption cross section and the saturation parameter of the dominant AsGa to the conduction-band defect transition. We show that this defect transition is mainly responsible for the large nonsaturable absorption in as-grown LT GaAs with fast recovery times. Reducing the AsGa density by annealing yields an optimized material with small nonsaturable absorption, high absorption modulation, and fast recovery times. © 1999 American Institute of Physics.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.72.J- Point defects and defect clusters
61.72.Cc Kinetics of defect formation and annealing
71.55.Eq III-V semiconductors
71.20.Nr Semiconductor compounds
78.47.-p Spectroscopy of solid state dynamics

Concentration-controlled phase selection of silicide formation during reactive deposition

A. Vantomme, S. Degroote, J. Dekoster, G. Langouche, and R. Pretorius

Appl. Phys. Lett. 74, 3137 (1999); http://dx.doi.org/10.1063/1.124090 (3 pages) | Cited 35 times

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Slow (low-rate) reactive deposition of a metal onto a Si substrate can result in direct formation of a metal disilicide, thereby skipping the metal-rich phases in the formation sequence. These observations have been explained thermodynamically by using the effective heat of formation model. As a result of this concentration-controlled phase selection, it is possible to form disilicides, such as CoSi2, NiSi2, or β-FeSi2 at much lower growth temperatures than possible in conventional solid-phase reaction of a metal layer deposited onto Si at room temperature (i.e., lower than the nucleation temperature). Moreover, epitaxial growth of CoSi2/Si(100), which is not possible by solid-phase reaction, becomes achievable when depositing Co atoms sufficiently slowly onto a heated Si substrate. © 1999 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.40.Sz Deposition technology
81.15.Kk Vapor phase epitaxy; growth from vapor phase
85.40.Ls Metallization, contacts, interconnects; device isolation
82.60.Cx Enthalpies of combustion, reaction, and formation
81.15.Aa Theory and models of film growth

GHz bandwidth GaAs light-emitting diodes

C. H. Chen, M. Hargis, J. M. Woodall, M. R. Melloch, J. S. Reynolds, E. Yablonovitch, and W. Wang

Appl. Phys. Lett. 74, 3140 (1999); http://dx.doi.org/10.1063/1.124092 (3 pages) | Cited 13 times

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Double-heterostructure GaAs/GaAlAs light-emitting diodes (LEDs) have been fabricated with the emitter regions beryllium doped to 2×1019 and 7×1019 cm−3. The 7×1019 cm−3 doped emitters have an internal quantum efficiency of 10% and an optical modulation bandwidth of 1.7 GHz. The steady-state optical output power versus the input current shows an external efficiency of 2.5 μW/mA. The 2×1019 cm−3 emitters have internal quantum efficiencies as high as 80%, but a reduced cutoff frequency. The external quantum efficiency reaches 10 μW/mA. These high-speed LEDs are produced by reducing the radiative lifetime to 100–250 ps without significantly degrading internal quantum efficiency. The current results on heavily beryllium-doped LEDs exhibit, to the best of our knowledge, the highest external efficiencies to date for such high doping and efficiencies close to that observed for lower-doped LEDs. © 1999 American Institute of Physics.
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85.60.Jb Light-emitting devices
61.72.uj III-V and II-VI semiconductors
78.60.Fi Electroluminescence
78.66.Fd III-V semiconductors
42.79.Sz Optical communication systems, multiplexers, and demultiplexers

Effects of interfacial layer growth on the electrical characteristics of thin titanium oxide films on silicon

Byoung Hun Lee, Yongjoo Jeon, Keith Zawadzki, Wen-Jie Qi, and Jack Lee

Appl. Phys. Lett. 74, 3143 (1999); http://dx.doi.org/10.1063/1.124089 (3 pages) | Cited 50 times

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Effects of interfacial layer growth on reactively sputter-deposited TiO2 films were studied. Leakage current was reduced to 10−8 A/cm2 at +1 V after annealing in oxygen ambient and showed tunneling-like temperature dependence. As the interfacial layer grew, interface states and hysteresis were improved significantly. However, the reliability was degraded as the annealing temperature increased. © 1999 American Institute of Physics.
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73.61.Ng Insulators
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.55.-g Dielectric thin films
61.72.Cc Kinetics of defect formation and annealing
77.22.Jp Dielectric breakdown and space-charge effects
73.20.-r Electron states at surfaces and interfaces
84.32.Tt Capacitors

Photoluminescence from silicon nanoparticles in a diamond matrix

M. L. Terranova, S. Piccirillo, V. Sessa, S. Botti, and M. Rossi

Appl. Phys. Lett. 74, 3146 (1999); http://dx.doi.org/10.1063/1.124088 (3 pages) | Cited 5 times

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Composite polycrystalline diamond layers containing light-emitting Si nanoparticles (mean diameter: 3.6 and 6.2 nm) have been prepared by using a chemical-vapor deposition technique coupled with a powder-flowing apparatus. The room-temperature photoluminescence behavior of such material in the 1.6–2.5 eV energy range is found characterized by a strong increase of the emission efficiency from the Si nanostructures embedded in the diamond matrix. Moreover, the studies reveal that it is possible to tune the luminescence frequency in the yellow-green spectral region by selecting the size of the inserted Si grains. © 1999 American Institute of Physics.
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78.66.Vs Fine-particle systems
78.55.Ap Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.05.Cy Elemental semiconductors

Electrical transport in pure and boron-doped carbon nanotubes

Bingqing Wei, Ralph Spolenak, Philipp Kohler-Redlich, Manfred Rühle, and Eduard Arzt

Appl. Phys. Lett. 74, 3149 (1999); http://dx.doi.org/10.1063/1.124093 (3 pages) | Cited 77 times

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The resistivities of individual multiwalled pure and boron-doped carbon nanotubes have been measured in the temperature range from 25 to 300 °C. The connection patterns were formed by depositing two-terminal tungsten wires on a nanotube using focused-ion-beam lithography. A decrease of the resistivity with increasing temperature, i.e., a semiconductor-like behavior, was found for both B-doped and pure carbon nanotubes. B-doped nanotubes have a reduced room-temperature resistivity (7.4×10−7–7.7×10−6 Ωm) as compared to pure nanotubes (5.3×10−6–1.9×10−5 Ωm), making the resistivity of the doped tubes comparable to those along the basal plane of graphite. The activation energy derived from the resistivity versus temperature Arrhenius plots was found to be smaller for the B-doped (55–70 meV) than for the pure multiwalled nanotubes (190–290 meV). © 1999 American Institute of Physics.
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72.20.Fr Low-field transport and mobility; piezoresistance
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
72.80.Rj Fullerenes and related materials

Tensile tests of ropes of very long aligned multiwall carbon nanotubes

Z. W. Pan, S. S. Xie, L. Lu, B. H. Chang, L. F. Sun, W. Y. Zhou, G. Wang, and D. L. Zhang

Appl. Phys. Lett. 74, 3152 (1999); http://dx.doi.org/10.1063/1.124094 (3 pages) | Cited 81 times

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We have directly measured the Young’s modulus and tensile strength of multiwall carbon nanotubes by pulling very long (∼2 mm) aligned nanotube ropes with a specially designed stress-strain puller. This puller can apply an axial force to the rope and simultaneously measure the corresponding rope elongation and the change in rope resistance. The average Young’s modulus and tensile strength obtained were 0.45±0.23 TPa and 1.72±0.64 GPa, respectively, which are lower than those calculated and measured previously. The factors that affect the mechanical strengths of nanotubes are discussed. © 1999 American Institute of Physics.
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62.20.D- Elasticity
62.20.F- Deformation and plasticity
81.05.ub Fullerenes and related materials
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