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12 Jul 1999

Volume 75, Issue 2, pp. 151-304

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Transmitted signal detection of optical disks with a superresolution near-field structure

Takashi Nakano, Akira Sato, Hiroshi Fuji, Junji Tominaga, and Nobufumi Atoda

Appl. Phys. Lett. 75, 151 (1999); http://dx.doi.org/10.1063/1.124302 (3 pages) | Cited 30 times

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We observed transmitted signals of phase change marks recorded in super-resolution near-field structure (super-RENS) disks under high speed disk rotation. The observed minimum mark size was 81 nm and the carrier to noise ratio was about 6 dB at a constant linear velocity of 4.8 m/s. The mark size was far beyond the diffraction limit of an optical pickup with a wavelength of 635 nm and a numerical aperture of 0.6. It was clear that near-field scattering actually occurred in super-RENS disks. © 1999 American Institute of Physics.
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42.79.Vb Optical storage systems, optical disks

AlGaInP/AuBe/glass light-emitting diodes fabricated by wafer bonding technology

R. H. Horng, D. S. Wuu, S. C. Wei, M. F. Huang, K. H. Chang, P. H. Liu, and K. C. Lin

Appl. Phys. Lett. 75, 154 (1999); http://dx.doi.org/10.1063/1.124303 (3 pages) | Cited 7 times

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An AlGaInP/AuBe/glass light-emitting diode (LED) was fabricated by a wafer bonding technique. The AlGaInP LED was grown on a temporary GaAs substrate by metalorganic vapor phase epitaxy. By bonding the AuBe/glass substrate on top of epitaxial layers, the temporary GaAs substrate was removed. The luminance of this wafer-bonded device is about 3050 cd/m2 (600 nm wavelength) at an operating current of 20 mA. It is about three times brighter than a conventional device with an absorbing GaAs substrate. This could be due to the fact that the AuBe/glass substrate serves as a reflective mirror, improving the light extraction efficiency. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
85.60.Jb Light-emitting devices
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
73.61.Ey III-V semiconductors
81.05.Ea III-V semiconductors

Optical poling of azo-dye-doped thin films using an ultrashort pulse laser

Kenji Kitaoka, Jinhai Si, Tsuneo Mitsuyu, and Kazuyuki Hirao

Appl. Phys. Lett. 75, 157 (1999); http://dx.doi.org/10.1063/1.124304 (3 pages) | Cited 12 times

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DR1(4-[N-ethyl-N-(2-hydroxyethyl)]amino-4′-nitro-azobenzene)-doped poly(methyl methacrylate) and DR1-doped silica gel thin films were optically polarized by the coherent superposition of the 1500 nm fundamental and the 750 nm second-harmonic light of a 130 fs pulse laser. These films were successfully polarized and saturated in 2 min, despite the transparent seed beams’ wavelength for the dye. The mechanism of the optical poling likely occurred in such a way that a multiphoton absorption and a photoisomerization of DR1 induced a polarized structure in the films. © 1999 American Institute of Physics.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.70.Jk Polymers and organics
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.66.Qn Polymers; organic compounds
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
42.50.Hz Strong-field excitation of optical transitions in quantum systems; multiphoton processes; dynamic Stark shift

High-quality near-field optical probes by tube etching

Raoul Stöckle, Christian Fokas, Volker Deckert, Renato Zenobi, Beate Sick, Bert Hecht, and Urs P. Wild

Appl. Phys. Lett. 75, 160 (1999); http://dx.doi.org/10.1063/1.124305 (3 pages) | Cited 116 times

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A method called tube etching for the fabrication of near-field optical probes is presented. Tip formation occurs inside a cylindrical cavity formed by the polymer coating of an optical fiber which is not stripped away prior to etching in hydrofluoric acid. The influence of temperature, etchant concentration, and fiber type on the tip quality is studied. A tip formation mechanism for the given geometry is proposed. The procedure overcomes drawbacks of the conventional etching techniques while still producing large cone angles: (i) tips with reproducible shapes are formed in a high yield, (ii) the surface roughness on the taper is drastically reduced, and (iii) the tip quality is insensitive to vibrations and temperature fluctuations during the etching process. After aluminum coating, optical probes with well-defined apertures are obtained. Due to the smooth glass surface the aluminum coating is virtually free of pinholes. © 1999 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.65.Cf Surface cleaning, etching, patterning

Thermo-optically tuned cascaded polymer waveguide taps

John M. Taboada, Jeffery J. Maki, Suning Tang, Lin Sun, Dechang An, Xuejun Lu, and Ray T. Chen

Appl. Phys. Lett. 75, 163 (1999); http://dx.doi.org/10.1063/1.124306 (3 pages) | Cited 1 time

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Polymer thermo-optic-waveguide taps have a potential application as light routers for guided-wave optical interconnects involving cascaded fanouts. The taps can guide light from an optical bus bar and direct it into other devices in a switching/modulation network. Thermo-optic waveguide taps are designed and fabricated on silicon wafers using standard very large-scale integrated fabrication techniques. Coupling of light into an adjacent waveguide tap is observed to increase by 12.3% from 38.7% to 51.0% with the application of 34 mW of power. © 1999 American Institute of Physics.
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42.82.Ds Interconnects, including holographic interconnects
42.70.Jk Polymers and organics
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays

Stimulated emission and lasing in whispering-gallery modes of GaN microdisk cavities

Seongsik Chang, Nathan B. Rex, Richard K. Chang, Gabel Chong, and Louis J. Guido

Appl. Phys. Lett. 75, 166 (1999); http://dx.doi.org/10.1063/1.124307 (3 pages) | Cited 41 times

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We report optically pumped, pulsed lasing action in whispering-gallery modes of GaN microdisk cavities at room temperature. The microdisk structure was fabricated by reactive-ion etching a 2-μm-thick GaN epitaxial layer grown via metalorganic chemical vapor deposition. Below the lasing threshold, stimulated emission with superlinear pump-intensity dependence is observed. Spontaneous-to-stimulated emission transition occurs at a pump intensity that is 10× lower than that for a GaN sample without a cavity structure. Above the lasing threshold, the pump-intensity dependence is almost linear and gain pinning is observed. In addition, whispering-gallery modes are observed with the linewidth of individual peaks being as narrow as 0.1 nm. © 1999 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.55.Sa Microcavity and microdisk lasers
78.45.+h Stimulated emission

Demonstration of high-brightness-mode propagation in a compound waveguide structure

J. A. Patchell, F. P. Logue, J. O’Gorman, J. Hegarty, B. A. Usievich, and V. A. Sychugov

Appl. Phys. Lett. 75, 169 (1999); http://dx.doi.org/10.1063/1.124308 (3 pages)

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We demonstrate the existence of an unusual and useful high-brightness guided mode of a multimode AlGaAs/GaAs heterostructure compound slab waveguide. This mode has a narrow near-field single lobe confined to the low-index regions of the waveguide. This mode was selectively probed by optically exciting quantum wells optimally placed in the waveguide. By pumping in a stripe geometry, lasing is observed above a threshold of 80 kW/cm2 indicating efficient lasing in the highest-order waveguide mode. The near-field emission pattern of the waveguide was imaged to provide a direct measurement of the intensity profile of the higher-order mode. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
42.55.Px Semiconductor lasers; laser diodes
42.79.Gn Optical waveguides and couplers

Organic light-emitting diodes with a bipolar transport layer

Vi-En Choong, Song Shi, Jay Curless, Chan-Long Shieh, H.-C. Lee, Franky So, Jun Shen, and Jie Yang

Appl. Phys. Lett. 75, 172 (1999); http://dx.doi.org/10.1063/1.124309 (3 pages) | Cited 83 times

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A structure based on a bipolar transport/emitting layer is proposed and implemented for making organic light-emitting diodes. Compared to the conventional heterojunction organic light-emitting diodes, more than a factor of six improvement in device reliability (a projected operating lifetime of 70 000 h) is achieved in the structure. The significant improvement in device lifetime is attributed to the elimination of the heterointerface present in the conventional devices which greatly affects the device reliability. © 1999 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
78.66.Qn Polymers; organic compounds

Effect of depolarization of scattered evanescent waves on particle-trapped near-field scanning optical microscopy

Min Gu and Pu Chun Ke

Appl. Phys. Lett. 75, 175 (1999); http://dx.doi.org/10.1063/1.124310 (3 pages) | Cited 11 times

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The degree of polarization of the scattered evanescent wave is measured with a laser-trapped particle for different incident angles. It is found that depolarization under s polarized beam illumination is stronger than that under p polarized beam illumination. As a result, the contrast of the evanescent wave interference pattern imaged in a particle-trapped near-field scanning optical microscope is improved approximately by a factor of 3 with a parallel analyzer under s polarized beam illumination. The phase shift of scattered evanescent waves under s and p polarized beam illumination is determined from the measured evanescent wave interference pattern. © 1999 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes

Molecular beam epitaxial growth of InGaAsN:Sb/GaAs quantum wells for long-wavelength semiconductor lasers

X. Yang, M. J. Jurkovic, J. B. Heroux, and W. I. Wang

Appl. Phys. Lett. 75, 178 (1999); http://dx.doi.org/10.1063/1.124311 (3 pages) | Cited 91 times

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InGaAsN:Sb/GaAs quantum wells (QWs) were grown by solid-source molecular beam epitaxy using a N2 radio-frequency plasma source. Photoluminescence reveals an enhancement in the optical properties of InGaAsN/GaAs QWs by the introduction of Sb flux during growth. X-ray diffraction and reflection high-energy electron diffraction analyses indicate that Sb acts as a surfactant. This technique was used to improve the performance of long-wavelength InGaAsN laser diodes. A low-threshold current density of 520 A/cm2 was achieved for an InGaAsN:Sb/GaAs single quantum well 1.2 μm laser diode at room temperature under pulsed operation. © 1999 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
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Boride-enhanced diffusion in silicon: Bulk and surface layers

N. E. B. Cowern, M. J. J. Theunissen, F. Roozeboom, and J. G. M. van Berkum

Appl. Phys. Lett. 75, 181 (1999); http://dx.doi.org/10.1063/1.124312 (3 pages) | Cited 20 times

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Epitaxial silicon boride layers, located at the surface or within the bulk of single-crystal silicon, give rise to enhanced diffusion of B during annealing. A submonolayer buried boride layer releases ≈0.4 interstitials per B atom in the layer, generating a transient diffusion enhancement in the range of 10–100 for several minutes at 900 °C. The resulting profile broadening is comparable to that caused by ion implantation damage. At the same temperature, surface boride layers generate a diffusion enhancement of ∼6, part of which arises from the B diffusion flux and part from the chemical influence of the boride layer. © 1999 American Institute of Physics.
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66.30.J- Diffusion of impurities
81.05.Cy Elemental semiconductors
68.35.Fx Diffusion; interface formation
66.30.Ny Chemical interdiffusion; diffusion barriers
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.J- Point defects and defect clusters
61.72.Cc Kinetics of defect formation and annealing
61.72.S- Impurities in crystals

Photoluminescence from Si nanocrystals dispersed in phosphosilicate glass thin films: Improvement of photoluminescence efficiency

Minoru Fujii, Atsushi Mimura, Shinji Hayashi, and Keiichi Yamamoto

Appl. Phys. Lett. 75, 184 (1999); http://dx.doi.org/10.1063/1.124313 (3 pages) | Cited 49 times

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Photoluminescence (PL) from Si nanocrystals (nc-Si) dispersed in phosphosilicate glass thin films was studied. It was found that, at room temperature, the 1.4 eV PL due to the recombination of electron-hole pairs in nc-Si becomes intense as the P concentration increases. At low temperatures, an additional peak related to defects at interfaces between nc-Si and the matrix was observed at about 0.9 eV. In contrast to the 1.4 eV peak, the 0.9 eV peak became weaker with increasing P concentration and almost disappeared at a P concentration of 1.5 mol %. These results suggest that the number of interface defects decreases with increasing P concentration and that this decrease leads to an improvement of the band-edge PL of nc-Si. © 1999 American Institute of Physics.  
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78.55.Ap Elemental semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.25.+i Surface conductivity and carrier phenomena
72.80.Cw Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Self-waveguided blue light emission in p-sexiphenyl crystals epitaxially grown by mask-shadowing vapor deposition

Hisao Yanagi and Takayuki Morikawa

Appl. Phys. Lett. 75, 187 (1999); http://dx.doi.org/10.1063/1.124314 (3 pages) | Cited 82 times

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Highly polarized and self-waveguided blue light emission was observed in oriented organic crystals of p-sexiphenyl (6P). The 6P molecules were epitaxially grown in needlelike crystals with a submillimeter length by mask-shadowing vapor deposition on the KCl (001) surface. In the crystals, the molecular axes are oriented parallel to the [110] direction of the KCl substrate and perpendicular to the needle axis of the crystal. Under ultraviolet excitation, the blue light emission was confined within the crystal and self-waveguided along the needle axis with the transverse-electric mode, then radiated from the tips of the needles. This self-waveguided emission in the crystal was based on the uniaxially oriented transition dipoles which lay on the KCl surface and were aligned perpendicular to the needle axis in the crystal. © 1999 American Institute of Physics.
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78.55.Kz Solid organic materials
78.66.Qn Polymers; organic compounds
68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)
42.79.Gn Optical waveguides and couplers
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Observation of magneto-optical second-harmonic generation with surface plasmon excitation in ultrathin Au/Co/Au films

V. V. Pavlov, G. Tessier, C. Malouin, P. Georges, A. Brun, D. Renard, P. Meyer, J. Ferré, and P. Beauvillain

Appl. Phys. Lett. 75, 190 (1999); http://dx.doi.org/10.1063/1.124315 (3 pages) | Cited 13 times

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Magnetization-induced second-harmonic generation with surface plasmon excitation in an ultrathin Au/Co/Au multilayer structure has been investigated. The resonant coupling of surface plasmons with the fundamental light results in drastic changes of the second-harmonic intensity and a sign reversal of nonlinear magneto-optical effects. Model analysis of the observed phenomena is given on the basis of the multiple interference of interface nonlinear contributions calculated using the Green’s functions formalism. © 1999 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.66.Bz Metals and metallic alloys
78.20.Ls Magneto-optical effects
75.70.Ak Magnetic properties of monolayers and thin films

Patterning of highly oriented pyrolytic graphite by oxygen plasma etching

Xuekun Lu, Hui Huang, Nikolay Nemchuk, and Rodney S. Ruoff

Appl. Phys. Lett. 75, 193 (1999); http://dx.doi.org/10.1063/1.124316 (3 pages) | Cited 46 times

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Patterning of highly oriented pyrolytic graphite (HOPG) was demonstrated by oxygen plasma etching of lithographically patterned substrates. Periodic arrays of islands, or holes of several microns on an edge, were obtained on freshly cleaved HOPG surfaces which had been prepared with SiO2 mask stops and then oxygen plasma etched. The etching process is described, including a study of etch rate as a function of rf power, and morphology was characterized with scanning electron microscopy. © 1999 American Institute of Physics.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning

Pendeoepitaxy of gallium nitride thin films

Kevin Linthicum, Thomas Gehrke, Darren Thomson, Eric Carlson, Pradeep Rajagopal, Tim Smith, Dale Batchelor, and Robert Davis

Appl. Phys. Lett. 75, 196 (1999); http://dx.doi.org/10.1063/1.124317 (3 pages) | Cited 83 times

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Pendeoepitaxy, a form of selective lateral growth of GaN thin films has been developed using GaN/AlN/6H–SiC(0001) substrates and produced by organometallic vapor phase epitaxy. Selective lateral growth is forced to initiate from the (11math0) GaN sidewalls of etched GaN seed forms by incorporating a silicon nitride seed mask and employing the SiC substrate as a pseudomask. Coalescence over and between the seed forms was achieved. Transmission electron microscopy revealed that all vertically threading defects stemming from the GaN/AlN and AlN/SiC interfaces are contained within the seed forms and a substantial reduction in the dislocation density of the laterally grown GaN. Atomic force microscopy analysis of the (11math0) face of discrete pendeoepitaxial structures revealed a root mean square roughness of 0.98 Å. The pendeoepitaxial layer photoluminescence band edge emission peak was observed to be 3.454 eV and is blueshifted by 12 meV as compared to the GaN seed layer. © 1999 American Institute of Physics.
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81.05.Ea III-V semiconductors
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors

Voltage modulation scanned probe oxidation

Francesc Pérez-Murano, Karen Birkelund, Kiyoshi Morimoto, and John A. Dagata

Appl. Phys. Lett. 75, 199 (1999); http://dx.doi.org/10.1063/1.124318 (3 pages) | Cited 44 times

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Scanned probe microscope (SPM) oxidation with voltage modulation leads to a significant enhancement of the oxide growth rate, improvement of the aspect ratio of oxide features, and control of the structural and electrical properties of the SPM oxide. Variation of the voltage-pulse parameters confirms that the oxide dimensions can be controlled sensitively over a wide range of pulse parameters and that voltage modulation overcomes the self-limiting character of SPM oxidation by reducing the buildup of space charge within the oxide during growth. The enhancement can be used to increase the writing speed or lower the voltage, both beneficial for practical nanoelectronics fabrication. © 1999 American Institute of Physics.
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81.65.Mq Oxidation
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
81.05.Cy Elemental semiconductors

Determination of nematic polar anchoring from retardation versus voltage measurements

Yu. A. Nastishin, R. D. Polak, S. V. Shiyanovskii, and O. D. Lavrentovich

Appl. Phys. Lett. 75, 202 (1999); http://dx.doi.org/10.1063/1.124319 (3 pages) | Cited 28 times

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The popular “high-electric-field” technique to determine the polar anchoring coefficient W of a nematic–substrate interface requires the simultaneous measurement of the capacitance and optical phase retardation of a liquid crystal cell as a function of applied voltage. We develop a generalized model that makes it possible to eliminate the capacitance measurement. The new technique, called the RV (retardation versus voltage) technique, requires only the measurement of retardation as a function of applied voltage, and allows for the determination of W by a linear fit over a prescribed voltage window. The technique is not sensitive to uniformity of the cell thickness, does not require patterned electrodes, and allows for the local probe of the surface. The value of W obtained by the RV technique is the same as W obtained by the traditional technique. © 1999 American Institute of Physics.
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61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order

Formation of epitaxially strained islands by controlled annealing

Y. W. Zhang

Appl. Phys. Lett. 75, 205 (1999); http://dx.doi.org/10.1063/1.124320 (3 pages) | Cited 5 times

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A three-dimensional continuum method is developed to simulate the formation of epitaxially strained islands during controlled annealing. In the formulation, the strain energy density, surface energy and surface energy anisotropy are taken into account. Our simulations show that no surface energy anisotropy leads to spherical caps while high anisotropy leads to elongated islands. Under the present framework, a relatively uniform and regular island array can be obtained at a certain annealing time from a random surface. An almost perfectly uniform and regular island array can be obtained at a certain annealing time from a random surface with one dominant wavelength, which is in a specific range; for long-time annealing, these island arrays are undergoing ripening. © 1999 American Institute of Physics.
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81.15.Aa Theory and models of film growth
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.72.Cc Kinetics of defect formation and annealing
68.35.Md Surface thermodynamics, surface energies

Ultrafast carrier dynamics in germanium nanoparticles

P. Tognini, A. Stella, S. De Silvestri, M. Nisoli, S. Stagira, P. Cheyssac, and R. Kofman

Appl. Phys. Lett. 75, 208 (1999); http://dx.doi.org/10.1063/1.124321 (3 pages) | Cited 11 times

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It is shown that the ultrafast carrier dynamics in Ge nanoparticles involving the electronic density of states well above the gap can be separated in two regimes: a faster one (∼1 ps) characterized by bleaching of the absorption around 490 nm and a slower one (up to a few hundred picoseconds) governed by band gap renormalization. There is also a clear correspondence between the spectral response in both regimes and a bulk-like band structure for sizes below the exciton Bohr radius. Quantum confinement is manifested through the measurable blueshift of E1+Δ1 spectral structure in the ultrafast optical response. © 1999 American Institute of Physics.
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73.22.-f Electronic structure of nanoscale materials and related systems
78.66.Vs Fine-particle systems
78.66.Db Elemental semiconductors and insulators
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency

Contribution of atomic and molecular ions to dry-etch damage

L. G. Deng, M. Rahman, J. A. van den Berg, and C. D. W. Wilkinson

Appl. Phys. Lett. 75, 211 (1999); http://dx.doi.org/10.1063/1.124322 (3 pages) | Cited 3 times

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Using ions of low energy is accepted as an essential requirement in achieving low damage when dry-etching III–V semiconductors. SiCl4 is widely used to make GaAs electron devices. We have studied the effect of a SiCl4 reactive ion etching environment as well as the effect of the bombardment by the separate constituent ions from a SiCl4 discharge in a low-energy implanter. Photoluminescence intensity measurements from GaAs/AlGaAs quantum well probe structures have been used to study the damage inflicted. We find that molecular ions contribute less to deep damage than do atomic ions. Thus, low damage may be promoted by selecting reactive etch chemistries with low ion energies and small atomic to molecular ion fractions. © 1999 American Institute of Physics.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
78.55.Cr III-V semiconductors
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Temperature-dependent micro-photoluminescence of individual CdSe self-assembled quantum dots

J. C. Kim, H. Rho, L. M. Smith, Howard E. Jackson, S. Lee, M. Dobrowolska, and J. K. Furdyna

Appl. Phys. Lett. 75, 214 (1999); http://dx.doi.org/10.1063/1.124323 (3 pages) | Cited 38 times

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We use micro- and nano-photoluminescence to study the temperature-dependent excitonic emission from CdSe quantum dots embedded in a ZnSe matrix. By varying the spatial resolution from 200 nm to 1.7 μm, we are able to study the temperature dependence of the ultranarrow (∼200 μeV) emission from excitons confined to single quantum dots, as well as statistical ensembles of up to 200 dots. By measuring the quenching of the photoluminescence (PL) with temperature, we find compelling evidence that the PL emission from these samples results from two different kinds of states. Similar to previous work, we find that a broad PL line persists to 300 K with an activation energy of ∼40 meV. However, we find that the ultranarrow lines are quenched at about 60 K, indicating an effective activation energy of only 4.0 meV. © 1999 American Institute of Physics.
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78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.35.-y Excitons and related phenomena
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Comparison of mobility and hole current activation energy in the space charge trap-limited regime in a starburst amine

J. Staudigel, M. Stössel, F. Steuber, and J. Simmerer

Appl. Phys. Lett. 75, 217 (1999); http://dx.doi.org/10.1063/1.124327 (3 pages) | Cited 12 times

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Using two complementary methods, we have investigated the individual contribution of the space charge-limited hole transport in vapor-deposited films of 4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (m-MTDATA) to the temperature behavior of organic light-emitting diodes. In single-layer indium tin oxide/m-MTDATA/Ag structures, we have measured the activation energies of the current density and of the hole mobility as a function of the applied electric field. Both activation energies obtained under steady-state and pulsed conditions are comparable, which confirms that the temperature behavior of the current density is predominantly governed by the hole mobility. © 1999 American Institute of Physics.
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73.50.Fq High-field and nonlinear effects
72.80.Le Polymers; organic compounds (including organic semiconductors)
72.20.Ht High-field and nonlinear effects
85.60.Jb Light-emitting devices
73.61.Ph Polymers; organic compounds

High-quality highly strained InGaAs quantum wells grown on InP using (InAs)n(GaAs)0.25 fractional monolayer superlattices

S. Jourba, M. Gendry, O. Marty, M. Pitaval, and G. Hollinger

Appl. Phys. Lett. 75, 220 (1999); http://dx.doi.org/10.1063/1.124328 (3 pages) | Cited 4 times

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(InAs)n/(GaAs)m (n = 1.5–2, m = 0.25 monolayer) fractional monolayer superlattices (FMS) have been used to grow highly strained InGaAs quantum wells (QWs) on InP by molecular beam epitaxy. We show that FMS quantum wells have better structural and optoelectronic properties compared to equivalent QWs grown using standard procedures. In addition, the onsets of the three-dimensional growth mode and plastic relaxation are delayed, which allows the highest emission wavelength in the InxGa1−xAs/InGaAlAs/InP system to be extended up to 2.35 μm at high growth temperatures (500 °C). © 1999 American Institute of Physics.
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81.05.Ea III-V semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.Ct Interface structure and roughness
68.35.Gy Mechanical properties; surface strains

Investigation of periodicity fluctuations in strained (GaNAs)1(GaAs)m superlattices by the kinematical simulation of x-ray diffraction

Z. Pan, Y. T. Wang, Y. Zhuang, Y. W. Lin, Z. Q. Zhou, L. H. Li, R. H. Wu, and Q. M. Wang

Appl. Phys. Lett. 75, 223 (1999); http://dx.doi.org/10.1063/1.124329 (3 pages) | Cited 9 times

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Periodicity fluctuations of layer thickness and composition in a superlattice not only decrease the intensity, they also broaden the width of the satellite peaks in the x-ray diffraction pattern. In this letter, we develop a method that is dependent on the width of satellite peaks to assess periodicity fluctuations of a superlattice quickly. A linear relation of the magnitude of fluctuations, peak width and peak order has been derived from x-ray diffraction kinematical theory. By means of this method, periodicity fluctuations in strained (GaNAs)1(GaAs)m superlattices grown on GaAs substrates by molecular beam epitaxy have been studied. Distinct satellite peaks indicate that the superlattices are of high quality. The N composition of 0.25 and its fluctuation of 20% in a strained GaNxAs1−x monolayer are obtained from simulations of the measured diffraction pattern. The x-ray simulations and in situ observation results of reflection high-energy electron diffraction are in good agreement. © 1999 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.05.Ea III-V semiconductors
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