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15 Jun 1998

Volume 72, Issue 24, pp. 3097-3228

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Patterning the second-order optical nonlinearity of asymmetric quantum wells by ion implantation enhanced intermixing

S. Janz, M. Buchanan, P. van der Meer, Z. R. Wasilewski, D.-X. Xu, P. Piva, I. V. Mitchell, U. G. Akano, and A. Fiore

Appl. Phys. Lett. 72, 3097 (1998); http://dx.doi.org/10.1063/1.121558 (3 pages) | Cited 4 times

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The change in the second-order nonlinear susceptibility of an asymmetric quantum well (AQW) superlattice induced by ion beam-enhanced intermixing has been measured. The surface-emitted second-harmonic intensities radiated from implanted and masked areas of an AQW waveguide were measured and compared for incident wavelengths between λ = 1480 and 1600 nm. Intermixing resulted in a 60 meV blueshift of the AQW band edge and a uniform suppression of the AQW second-order susceptibility, while the masked AQWs were unchanged. © 1998 American Institute of Physics.
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42.65.An Optical susceptibility, hyperpolarizability
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.66.-w Optical properties of specific thin films
61.72.up Other materials
61.80.Jh Ion radiation effects
64.75.-g Phase equilibria
68.35.Fx Diffusion; interface formation
42.65.Wi Nonlinear waveguides
42.79.Gn Optical waveguides and couplers

A photoconductive, miniature terahertz source

Richard K. Lai, Jiunn-Ren Hwang, Theodore B. Norris, and John F. Whitaker

Appl. Phys. Lett. 72, 3100 (1998); http://dx.doi.org/10.1063/1.121559 (3 pages) | Cited 5 times

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We discuss the performance of a micromachined, photoconductive terahertz emitter that is fabricated on low-temperature-grown GaAs. The device is mounted on a pair of single-mode optical fibers that allows the source to be freely positionable. A strong radiation burst is emitted due to the large magnetic moment created by the electrode. The emitter’s small feature size of 300 μm by 300 μm with a photoconductive switch area of 30 μm by 30 μm suggests its application for terahertz, time-domain, near-field spectroscopy and imaging. © 1998 American Institute of Physics.
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42.72.Ai Infrared sources
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
42.79.Pw Imaging detectors and sensors

Piezoelectric effects on electrical and optical properties of wurtzite GaN/AlGaN quantum well lasers

Seoung-Hwan Park and Shun-Lien Chuang

Appl. Phys. Lett. 72, 3103 (1998); http://dx.doi.org/10.1063/1.121560 (3 pages) | Cited 78 times

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The piezoelectric effects on the optical gain of wurtzite GaN/AlGaN QW lasers taking into account the many-body effects are presented. The self-consistent model with piezoelectric field effect shows that band structures and optical gain are significantly affected by the piezoelectric field at relatively low carrier densities. The peak gain is redshifted and smaller when compared to the flat-band model without piezoelectric field effect. Only gain peaks corresponding to C1-HH1 and C1-LH1 transitions are observed in the investigated range and transitions for C1-HH2 and C1-LH2 are negligible due to the large subband energy spacing at low carrier densities and small matrix elements at high carrier densities. At high carrier densities, the self-consistent model shows band structures and optical properties similar to the flat-band model due to the screening effects. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
78.66.Fd III-V semiconductors
73.61.Ey III-V semiconductors
71.20.Nr Semiconductor compounds
42.60.By Design of specific laser systems
77.65.-j Piezoelectricity and electromechanical effects
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
73.20.At Surface states, band structure, electron density of states
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Metalorganic molecular-beam-epitaxy-grown In0.77Ga0.23As/InGaAs multiple quantum well lasers emitting at 2.07 μm wavelength

Manabu Mitsuhara, Matsuyuki Ogasawara, Mamoru Oishi, and Hideo Sugiura

Appl. Phys. Lett. 72, 3106 (1998); http://dx.doi.org/10.1063/1.121561 (3 pages) | Cited 10 times

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We report the growth of a four-period multiple quantum well (MQW) structure with 115-Å-thick, +1.65% strained wells by metalorganic molecular beam epitaxy and its application to 2 μm wavelength lasers. Transmission electron microscopy and photoluminescence measurements reveal that the structural and optical properties of MQW are sensitive to the barrier strain: the values of barrier strain required for MQW with both flat barrier-well interfaces and strong photoluminescence fall within a small range from −0.17% to +0.14%. The double-crystal x-ray diffraction pattern of the MQW remains unchanged before and after annealing at 620 °C for 2.5 h. Buried heterostructure lasers fabricated using metalorganic vapor phase epitaxy regrowth have an emission wavelength of 2.07 μm under a continuous operation current of 120 mA at 55 °C. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
68.35.Ct Interface structure and roughness
81.05.Ea III-V semiconductors

Dynamics of infrared absorption caused by hydroxyl groups and its effect on refractive index evolution in ultraviolet exposed hydrogen loaded GeO2-doped fibers

F. M. Araújo, E. Joanni, M. B. Marques, and O. G. Okhotnikov

Appl. Phys. Lett. 72, 3109 (1998); http://dx.doi.org/10.1063/1.121562 (3 pages) | Cited 6 times

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The growth dynamics of UV induced IR absorption and related refractive index change in hydrogen loaded GeO2-doped fibers have been studied. We report a higher initial rate and strong saturation for Ge–OH generation compared with Si–OH formation under UV exposure. A close correlation was found between the Ge/Si–OH groups concentration and the induced index change as a function of the UV exposure time. © 1998 American Institute of Physics.
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42.81.Cn Fiber testing and measurement of fiber parameters
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.35.+c Brillouin and Rayleigh scattering; other light scattering
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Spectrally-resolved near-field investigation of proton implanted vertical cavity surface emitting lasers

Jeongyong Kim, David E. Pride, Joseph T. Boyd, and Howard E. Jackson

Appl. Phys. Lett. 72, 3112 (1998); http://dx.doi.org/10.1063/1.121563 (3 pages) | Cited 9 times

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Emission characteristics of proton implanted vertical cavity surface emitting lasers have been studied by spectrally-resolved near-field scanning optical microscopy (NSOM). Measured spatial intensity distributions of individual transverse modes show a fundamental mode at threshold, and two double-lobed first-order modes excited around aperture edge above 1.3× threshold injection current. The use of high spectral and spatial resolution NSOM enabled the detection of a local resonance wavelength dependence on position across the laser aperture; from these data, a lateral refractive index variation is calculated. As the injection current is increased, these index distributions are found to be consistent with the observed reduction of the spatial width of the intensity distribution and the increase in the spectral mode spacing. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
07.79.Fc Near-field scanning optical microscopes
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.72.uj III-V and II-VI semiconductors

High definition aperture probes for near-field optical microscopy fabricated by focused ion beam milling

J. A. Veerman, A. M. Otter, L. Kuipers, and N. F. van Hulst

Appl. Phys. Lett. 72, 3115 (1998); http://dx.doi.org/10.1063/1.121564 (3 pages) | Cited 86 times

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We have improved the optical characteristics of aluminum-coated fiber probes used in near-field scanning optical microscopy by milling with a focused ion beam. This treatment produces a flat-end face free of aluminum grains, containing a well-defined circularly-symmetric aperture with controllable diameter down to 20 nm. The polarization behavior of the tips is circularly symmetric with a polarization ratio exceeding 1:100. The improved imaging characteristics are demonstrated by measuring single molecule fluorescence. Count rates increase more than one order of magnitude over unmodified probes, and the molecule images map a spatial electric field distribution of the aperture in agreement with calculations. © 1998 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
81.65.Cf Surface cleaning, etching, patterning
78.55.-m Photoluminescence, properties and materials

Reduction of effects of Fabry–Perot fringing in wavelength modulation experiments

A. N. Dharamsi, P. C. Shea, and A. M. Bullock

Appl. Phys. Lett. 72, 3118 (1998); http://dx.doi.org/10.1063/1.121565 (3 pages) | Cited 1 time

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One of the factors limiting the sensitivity of wavelength modulation experiments is the fringing that is created by inadvertent multiple reflections between parallel optical surfaces in the apparatus. It is shown that the effects of this “étaloning” can be countered by using detection harmonic orders greater than the second. A theoretical basis for the effect is presented and compared with experimental results obtained. © 1998 American Institute of Physics.
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42.79.Hp Optical processors, correlators, and modulators
07.60.Ly Interferometers
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Optically induced domain waveguides in SrxBa1−xNb2O6 crystals

Alexander Bekker, Aviad Peda’el, Naum K. Berger, Moshe Horowitz, and Baruch Fischer

Appl. Phys. Lett. 72, 3121 (1998); http://dx.doi.org/10.1063/1.121566 (3 pages) | Cited 9 times

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Optically induced refractive index patterns, which can be used for waveguides, were formed in SrxBa1−xNb2O6 crystals using an erasable fixing mechanism, based on domains formation by the screening effect. The sign and strength of the refractive index change of the fixed waveguides was controllable by an applied electric field. Fixed patterns are shown to allow the storage of many spatially multiplexed holograms. © 1998 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
42.70.Gi Light-sensitive materials
42.70.Ln Holographic recording materials; optical storage media
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
77.80.Dj Domain structure; hysteresis
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Polarization switching in a tensile-strained InGaAs/InGaAsP multiple quantum well distributed feedback laser diode

Natsuhiko Mizutani, Sei-ichi Miyazawa, Masahiro Nakanishi, Masao Majima, Jun Nitta, Yoshinobu Sekiguchi, Hidetoshi Nojiri, and Yuichi Handa

Appl. Phys. Lett. 72, 3124 (1998); http://dx.doi.org/10.1063/1.121567 (3 pages) | Cited 1 time

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An inhomogeneously biased distributed feedback (DFB) laser diode (LD) with two electrodes switched its polarization mode by 3 mA change of the bias current, maintaining single longitudinal mode oscillation. In the active layer of the LD, 13 nm thick and 0.6% tensile-strained InGaAs multiple quantum well (MQW) equalized the transverse electric and the transverse magnetic modal optical gain at 1.55 μm. With various grating pitches on the same MQW active layer, polarization switching DFB LDs were realized in the wavelength range as wide as 18 nm. The linewidth characteristics during the polarization switching were confirmed to be narrow due to the small switching current. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.65.Pc Optical bistability, multistability, and switching, including local field effects

Green photoluminescence from Er-containing amorphous SiN thin films

A. R. Zanatta and L. A. O. Nunes

Appl. Phys. Lett. 72, 3127 (1998); http://dx.doi.org/10.1063/1.121568 (3 pages) | Cited 30 times

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Green light emission at room temperature was achieved from nonhydrogenated amorphous silicon–nitrogen (a-SiN) thin films. The films were deposited by cosputtering a silicon target covered with metallic erbium platelets in an Ar+N2 atmosphere. According to the deposition conditions, the nitrogen concentration [N] reached ∼ 40 at. % rendering an optical gap of approximately 3.5 eV while the Er concentration [Er] was estimated to be ∼ 10 at. % in the present films. The high [Er] associated to the optical band gap allows the direct excitation of Er3+ ions. This optical excitation is more efficient at low temperatures as a consequence of the reduction in nonradiative processes, and when exciting the samples with the 488.0 nm line of an Ar+ laser which is in resonance with the 4F7/2Er3+ energy level. In addition to light emission at ∼ 520 and ∼ 545 nm, transitions in the infrared energy region could be easily verified in as-deposited samples. © 1998 American Institute of Physics.
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78.66.Nk Insulators
78.55.Hx Other solid inorganic materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.43.Er Other amorphous solids
81.15.Cd Deposition by sputtering

High-power λ ≈ 8 μm quantum cascade lasers with near optimum performance

Claire Gmachl, Alessandro Tredicucci, Federico Capasso, Albert L. Hutchinson, Deborah L. Sivco, James N. Baillargeon, and Alfred Y. Cho

Appl. Phys. Lett. 72, 3130 (1998); http://dx.doi.org/10.1063/1.121569 (3 pages) | Cited 59 times

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Quantum cascade (QC) lasers emitting at λ ≈ 8 μm with a power performance equal to short-wavelength (λ ≈ 5 μm) QC lasers are reported. The device improvement is mainly achieved by a design of the injector/relaxation region, which at laser threshold allows resonant carrier injection between the ground state of the preceding and the upper laser level of the subsequent active region. In pulsed operation a peak output power of 1.3 W per facet has been measured at 100 K. At room temperature a record peak power of 325 mW and a record slope efficiency of 180 mW/A have been measured. In continuous-wave operation the maximum power at 30 K was 510 mW per facet and still 200 mW per facet at 80 K. The high values of the output power and slope efficiency demonstrate the validity of the cascading scheme, in which electrons above threshold generate one photon per each active region they successively traverse. © 1998 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.)

Focused ion-beam fabrication of fiber probes with well-defined apertures for use in near-field scanning optical microscopy

Saeed Pilevar, Klaus Edinger, Walid Atia, Igor Smolyaninov, and Christopher Davis

Appl. Phys. Lett. 72, 3133 (1998); http://dx.doi.org/10.1063/1.121570 (3 pages) | Cited 23 times

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We present a focused ion-beam (FIB) fabrication method for very clean and well-defined subwavelength fiber probes with metallic apertures of a desired diameter for use in near-field scanning optical microscopy. Such probes exhibit improved features compared to probes coated with metal by the conventional angled evaporation technique. Examples of FIB fabricated fiber probes are shown and images of a test sample are presented using one of the probes in a near-field microscope. © 1998 American Institute of Physics.
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42.81.Bm Fabrication, cladding, and splicing
07.79.Fc Near-field scanning optical microscopes
07.60.Vg Fiber-optic instruments

Red–green–blue photopumped lasing from ZnCdMgSe/ZnCdSe quantum well laser structures grown on InP

L. Zeng, B. X. Yang, A. Cavus, W. Lin, Y. Y. Luo, M. C. Tamargo, Y. Guo, and Y. C. Chen

Appl. Phys. Lett. 72, 3136 (1998); http://dx.doi.org/10.1063/1.121571 (3 pages) | Cited 20 times

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Room-temperature optical pumped lasing emission in the red, green, and blue has been obtained from ZnCdMgSe/ZnCdSe quantum well (QW) laser structures grown on InP substrates. The structures are nearly identical, except for variations in the thickness and/or composition of the QW layer. No other single set of semiconductor materials has been demonstrated whose structures are pseudomorphic on one single substrate, and produces light emitters throughout the entire visible range. Our results demonstrate the potential for these materials as integrated full color display devices. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
68.35.Ct Interface structure and roughness

Polymer-based highly multimode electro-optic waveguide modulator

De-Gui Sun and Ray T. Chen

Appl. Phys. Lett. 72, 3139 (1998); http://dx.doi.org/10.1063/1.121572 (3 pages) | Cited 4 times

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A unidirectional electro-optic modulator based on an asymmetrical highly multimode waveguide coupler is proposed. To achieve high switching performance in a guided-wave coupler, a grating-based dumping wall is placed on the larger waveguide. This dumping effect makes the asymmetric highly multimode waveguide coupler possess a highly efficient unidirectional coupling process. A high modulation depth of 99% is experimentally achieved at 633 nm wavelength with an index modulation of 3.0×10−4. This device can be used for multimode optical interconnection systems such as data communications and fiber sensor networks. © 1998 American Institute of Physics.
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42.79.Hp Optical processors, correlators, and modulators
42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays
42.82.Ds Interconnects, including holographic interconnects
42.70.Jk Polymers and organics
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Elastic and plastic deformation of diamondlike carbons

A. M. Stoneham, P. D. Godwin, A. P. Sutton, and S. J. Bull

Appl. Phys. Lett. 72, 3142 (1998); http://dx.doi.org/10.1063/1.121573 (3 pages) | Cited 6 times

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In exploiting tribological applications of diamondlike carbons (DLC, a-C:H), both elastic and plastic properties must be optimized. We use tight-binding molecular dynamics to generate realization of DLC, from which can be obtained properties and their dependence on the precursors used, and on the H/C ratio. Here we analyze the elastic properties and especially the rebonding events which occur under strain. Rebonding occurs only at rather large strains; in some cases, it is reversible. Hydrogen has a key role in determining the number of carbons with less than four carbon neighbors, since it is mainly these carbons which participate in the major plastic (rebonding) events. © 1998 American Institute of Physics.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
62.20.D- Elasticity

Determination of the ordered structures of Pb(Mg1/3Nb2/3)O3 and Ba(Mg1/3Nb2/3)O3 by atomic-resolution Z-contrast imaging

Y. Yan, S. J. Pennycook, Z. Xu, and D. Viehland

Appl. Phys. Lett. 72, 3145 (1998); http://dx.doi.org/10.1063/1.121574 (3 pages) | Cited 61 times

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The atomic structure of ordered domains in Ba(Mg1/3Nb2/3)O3 and La-doped and undoped Pb(Mg1/3Nb2/3)O3 is studied by high-resolution Z-contrast imaging. The ordered domain structure in both doped and undoped Pb(Mg1/3Nb2/3)O3 is determined to be in agreement with the charge balanced random-layer model and inconsistent with the space-charge model. It is shown that La doping in Pb(Mg1/3Nb2/3)O3 enhances not only the domain size but also the degree of ordering. © 1998 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis

Topography measurements of the critical thickness of ZnSe grown on GaAs

G. Horsburgh, K. A. Prior, W. Meredith, I. Galbraith, B. C. Cavenett, C. R. Whitehouse, G. Lacey, A. G. Cullis, P. J. Parbrook, P. Möck, and K. Mizuno

Appl. Phys. Lett. 72, 3148 (1998); http://dx.doi.org/10.1063/1.121575 (3 pages) | Cited 6 times

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Synchrotron-based x-ray topography (XRT) measurements have been used to study the initial stages of relaxation in ZnSe layers grown by molecular beam epitaxy on vertical gradient freeze Bridgman GaAs substrates. The formation of the very first strain-relieving misfit dislocations in the grown ZnSe layers has been detected in a layer of thickness 100 nm. No such dislocations have been observed in a corresponding layer of 95 nm thickness. The critical thickness for this material system is therefore estimated to be 97.5±2.5 nm, which is markedly lower than the widely accepted value of 150 nm. In contrast to the InGaAs/GaAs system, combined XRT and transmission electron microscopy studies indicate that the initial misfit dislocations observed for ZnSe/GaAs are not, in general, formed by the bending over of pre-existing threading dislocations into the interface, but by other mechanisms such as stacking fault decomposition. The critical thickness data obtained have been used to infer the maximum critical thickness of CdZnSe quantum wells possible in II–VI laser diodes. © 1998 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.Lk Linear defects: dislocations, disclinations
61.72.Nn Stacking faults and other planar or extended defects
68.35.Ct Interface structure and roughness
68.60.Bs Mechanical and acoustical properties

Self-regulated growth of tilted superlattices by atomic layer epitaxy

J. M. Hartmann, M. Charleux, J. Cibert, and H. Mariette

Appl. Phys. Lett. 72, 3151 (1998); http://dx.doi.org/10.1063/1.121576 (3 pages) | Cited 8 times

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We report on a self-regulated method for the growth of tilted superlattices. It relies on the reconstructed surfaces alternatively stabilized during the atomic layer epitaxy (ALE) of compound semiconductors. The c(2×2)+(2×1) Cd-stabilized and the (2×1) Te-stabilized surfaces alternatively formed during the ALE of CdTe and CdMn(Mg)Te ensure a self-regulation of the growth at 0.5 monolayer deposited per ALE cycle for both CdTe and CdMn(Mg)Te. We are thus able to overcome the problem of precise flux control inherent to tilted superlattices. © 1998 American Institute of Physics.
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81.05.Dz II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.35.B- Structure of clean surfaces (and surface reconstruction)

High-resolution imaging of contact potential difference with ultrahigh vacuum noncontact atomic force microscope

Shin’ichi Kitamura and Masashi Iwatsuki

Appl. Phys. Lett. 72, 3154 (1998); http://dx.doi.org/10.1063/1.121577 (3 pages) | Cited 115 times

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An ultrahigh vacuum scanning Kelvin probe force microscope (UHV SKPM) utilizing the gradient of electrostatic force, was developed based on an ultrahigh vacuum noncontact atomic force microscope (NC-AFM) capable of atomic level imaging, and used for simultaneous observation of contact potential difference (CPD) and NC-AFM images. CPD images of a Si(111) surface with Au deposited, clearly showed the potential difference in phases between 7×7 and 5×2 structures. When Ag was deposited as a submonolayer on the Si(111) 7×7 reconstructed surface, the atomic level lateral resolution was observed in CPD images as well as in NC-AFM topographic images. © 1998 American Institute of Physics.
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73.40.Cg Contact resistance, contact potential
73.30.+y Surface double layers, Schottky barriers, and work functions
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
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.40.Ns Metal-nonmetal contacts
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Intense visible photoluminescence in amorphous SiOx and SiOx:H films prepared by evaporation

H. Rinnert, M. Vergnat, G. Marchal, and A. Burneau

Appl. Phys. Lett. 72, 3157 (1998); http://dx.doi.org/10.1063/1.121578 (3 pages) | Cited 53 times

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Visible photoluminescence (PL) can be observed in a-SiOx and a-SiOx:H alloys prepared by evaporation of SiO in ultrahigh vacuum and under a flow of hydrogen ions, respectively. The hydrogen and oxygen bonding is studied by infrared spectrometry. The hydrogen stability is followed by thermal desorption spectrometry experiments. The evolution of the PL with annealing treatments shows that the PL can be attributed to a quantum confinement effect in a-Si clusters embedded in the matrix of a-SiOx. Hydrogen does not greatly contribute to the PL efficiency and to the thermal evolution of the a-Si clusters. © 1998 American Institute of Physics.
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78.66.Nk Insulators
78.55.Hx Other solid inorganic materials
68.55.-a Thin film structure and morphology
78.35.+c Brillouin and Rayleigh scattering; other light scattering
81.40.Gh Other heat and thermomechanical treatments
81.40.Tv Optical and dielectric properties related to treatment conditions
42.79.Wc Optical coatings

Relaxed Ge0.9Si0.1 alloy layers with low threading dislocation densities grown on low-temperature Si buffers

C. S. Peng, Z. Y. Zhao, H. Chen, J. H. Li, Y. K. Li, L. W. Guo, D. Y. Dai, Q. Huang, J. M. Zhou, Y. H. Zhang, T. T. Sheng, and C. H. Tung

Appl. Phys. Lett. 72, 3160 (1998); http://dx.doi.org/10.1063/1.121579 (3 pages) | Cited 31 times

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Relaxed GexSi1−x epilayers with high Ge fractions but low threading dislocation densities have been successfully grown on Si (001) substrate by employing a stepped-up strategy and a set of low-temperature GeySi1−y buffers. We show that even if the Ge fraction rises up to 90%, the threading dislocation density can be kept lower than 5×106 cm−2 in the top layers, while the total thickness of the structure is no more than 1.7 μm. © 1998 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Hd Other semiconductors

Nonradiative recombination at GaAs homointerfaces fabricated using an As cap deposition/removal process

M. Passlack, R. Droopad, Z. Yu, C. Overgaard, B. Bowers, and J. Abrokwah

Appl. Phys. Lett. 72, 3163 (1998); http://dx.doi.org/10.1063/1.121580 (3 pages) | Cited 2 times

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GaAs homointerfaces have been grown by molecular beam epitaxy using the steps of GaAs growth, As cap deposition, wafer storage, thermal desorption of the As cap, and GaAs overgrowth. As cap layers with a thickness of up to 7.8 μm were deposited and the wafers were stored for 3–7 days in ultrahigh vacuum (UHV) or under atmospheric conditions. Nonradiative recombination originating from the GaAs homointerface of wafers stored in UHV could not be detected (interface recombination velocity S≪1000 cm/s), however, significant nonradiative recombination (S = 104–105 cm/s) was found for all GaAs homointerfaces where wafer storage occurred under atmospheric conditions. This result demonstrates that the As cap deposition/removal process is inadequate for GaAs surface protection in a fabrication facility. © 1998 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.05.Ea III-V semiconductors
81.65.-b Surface treatments
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors

Minority carrier diffusion length and lifetime in GaN

Z. Z. Bandić, P. M. Bridger, E. C. Piquette, and T. C. McGill

Appl. Phys. Lett. 72, 3166 (1998); http://dx.doi.org/10.1063/1.121581 (3 pages) | Cited 45 times

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Electron beam induced current measurements on planar Schottky diodes on undoped GaN grown by metalorganic chemical vapor deposition are reported. The minority carrier diffusion length of 0.28 μm has been measured, indicating minority carrier lifetime of 6.5 ns. The tapping mode atomic force microscopy imaging of the surfaces and scanning electron microscopy of the cross sections have been used to characterize the linear dislocations and columnar structure of the GaN. The possible influence of recombination on the extended defects in GaN on the minority carrier diffusion length and lifetime is discussed, and contrasted to other recombination mechanisms. © 1998 American Institute of Physics.
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73.61.Ey III-V semiconductors
85.30.Kk Junction diodes
85.30.Hi Surface barrier, boundary, and point contact devices
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
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
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Fabrication of multiperiod Si/SiO2/Ge layered structure through chemical bond manipulation

K. Prabhakaran, T. Matsumoto, T. Ogino, and Y. Masumoto

Appl. Phys. Lett. 72, 3169 (1998); http://dx.doi.org/10.1063/1.121582 (3 pages) | Cited 2 times

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In this letter, we report a method called chemical bond manipulation for fabrication of multiperiod nanometer sized Si/SiO2/Ge layered structure. Chemical bond manipulation is a self-organization process which involves selective breaking and making of surface chemical bonds and thereby enable formation of the desired species on a full wafer scale. We show that oxygen of germanium oxide layer formed on Si(111) are picked up by the Si atoms arriving at the surface during subsequent growth. This phenomenon involves breaking of Ge–O bonds and making of Si–O bonds and leads to the formation of ultrathin Si and Ge layers sandwiched between ultrathin silicon oxide layers, preserving the original wafer morphology. This material exhibits blue-green light emission at room temperature when excited by ultraviolet laser. © 1998 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.40.Ty Semiconductor-insulator-semiconductor structures
78.66.Db Elemental semiconductors and insulators
78.55.-m Photoluminescence, properties and materials
81.05.Cy Elemental semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
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