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28 Aug 2000

Volume 77, Issue 9, pp. 1241-1405

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Quantum cascade lasers with monolithic air–semiconductor Bragg reflectors

L. Hvozdara, A. Lugstein, N. Finger, S. Gianordoli, W. Schrenk, K. Unterrainer, E. Bertagnolli, G. Strasser, and E. Gornik

Appl. Phys. Lett. 77, 1241 (2000); http://dx.doi.org/10.1063/1.1289910 (3 pages) | Cited 14 times

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Electrically pumped GaAs/AlGaAs quantum cascade lasers with monolithic one-dimensional photonic-band gap mirrors are presented. The mirrors consist of two, precisely defined grooves trenched across the laser ridge using a focused ion beam. A substantial improvement of the laser performance is achieved due to the increased reflectivity of these mirrors. A decrease of the threshold current by 40% at 150 K is observed. The maximum operation temperature increases from 155 K for an unmodified laser to 170 K for the laser with the modified mirrors, and an increase of the T0 parameter from 99 to 114 K is found. © 2000 American Institute of Physics.
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42.60.By Design of specific laser systems
42.79.Bh Lenses, prisms and mirrors
42.70.Qs Photonic bandgap materials
42.55.Px Semiconductor lasers; laser diodes
42.82.-m Integrated optics

Temperature dependence of narrow-band terahertz generation from periodically poled lithium niobate

Y.-S. Lee, T. Meade, M. DeCamp, T. B. Norris, and A. Galvanauskas

Appl. Phys. Lett. 77, 1244 (2000); http://dx.doi.org/10.1063/1.1290046 (3 pages) | Cited 41 times

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Femtosecond optical pulses are used to generate narrow-band terahertz wave forms via optical rectification in a periodically poled lithium niobate crystal. By cooling the crystal to reduce losses due to phonon absorption, we are able to obtain bandwidths as narrow as 18 GHz at a carrier frequency of 1.8 THz. Temperature-dependent measurements show insignificant bandwidth broadening between 10 and 120 K, although the terahertz power substantially decreases as the temperature increases. Absolute power measurements indicate a conversion efficiency of at least 10−5. © 2000 American Institute of Physics.
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07.57.Hm Infrared, submillimeter wave, microwave, and radiowave sources
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
84.40.-x Radiowave and microwave (including millimeter wave) technology

Composition, temperature, and crystal orientation dependence of the linear electro-optic properties of Pb(Zn1/3Nb2/3)O3–PbTiO3 single crystals

Y. Barad, Yu Lu, Z.-Y. Cheng, S.-E. Park, and Q. M. Zhang

Appl. Phys. Lett. 77, 1247 (2000); http://dx.doi.org/10.1063/1.1290156 (3 pages) | Cited 28 times

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The linear electro-optic (EO) coefficients of Pb(Zn1/3Nb2/3)O3–PbTiO3 single crystals over a broad composition range were investigated at temperatures from −20 to 80 °C. The orientation effect on the EO coefficients was also examined. For crystals poled in the 〈001〉 direction, a large r33 was observed near the morphotropic phase boundary (MPB). More importantly, r33 was found to be independent of temperature for the crystals on the tetragonal side of the MPB. In contrast, r13 was nearly zero for all compositions examined at all the temperatures. The large r33 near the MPB and the observed crystal orientation effect of the EO coefficients were also analyzed. © 2000 American Institute of Physics.
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78.20.Jq Electro-optical effects
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ej Polarization and depolarization
77.80.B- Phase transitions and Curie point

Relative intensity noise characteristics of injection-locked semiconductor lasers

X. Jin and S. L. Chuang

Appl. Phys. Lett. 77, 1250 (2000); http://dx.doi.org/10.1063/1.1290140 (3 pages) | Cited 11 times

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An experimental and theoretical study of relative intensity noise (RIN) spectra of side-mode injection-locked Fabry–Pérot semiconductor lasers is reported. It is shown that the injection-locking technique effectively increases the relaxation oscillation frequency from 4.5 GHz (free-running mode) to 12 GHz (injection-locked mode) and enhances relaxation peaks of the slave laser RIN spectra. Results from our theoretical model, which include the key parameters for semiconductor quantum-well lasers, such as the linewidth enhancement factor, the nonlinear gain saturation coefficients, and optical confinement factor, show good agreement with our experimental results. © 2000 American Institute of Physics.
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42.60.Fc Modulation, tuning, and mode locking
42.60.Mi Dynamical laser instabilities; noisy laser behavior
42.55.Px Semiconductor lasers; laser diodes
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency

Demonstration of optical gain at 1.06 μm in a neodymium-doped polyimide waveguide

Gauri Karve, Bipin Bihari, and Ray T. Chen

Appl. Phys. Lett. 77, 1253 (2000); http://dx.doi.org/10.1063/1.1290157 (3 pages) | Cited 37 times

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Neodymium-doped polyimide waveguides were studied for optical amplifier applications. Photoluminescence at 890 nm, 1.06 μm, and 1.33 μm from neodymium ions in the polymer matrix was observed. Optical gain of about 8 dB was measured at 1.06 μm in a 5-cm-long multimode channel waveguide. Phase separation was observed in the doped polyimide. Large scattering losses in the waveguides due to the phase separation were reduced by planarizing the layer of doped polyimide with another layer of undoped polyimide. Such a waveguide amplifier has potential applications in lossless splitters, lossless fiber, and waveguide systems with large fanout. © 2000 American Institute of Physics.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.70.Hj Laser materials
42.79.Gn Optical waveguides and couplers
78.55.-m Photoluminescence, properties and materials
78.45.+h Stimulated emission
42.70.Jk Polymers and organics
64.75.-g Phase equilibria
42.60.By Design of specific laser systems

Structural and optical properties of high-quality ZnTe homoepitaxial layers

J. H. Chang, M. W. Cho, H. M. Wang, H. Wenisch, T. Hanada, T. Yao, K. Sato, and O. Oda

Appl. Phys. Lett. 77, 1256 (2000); http://dx.doi.org/10.1063/1.1290155 (3 pages) | Cited 18 times

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The structural and optical properties of high-quality homoepitaxial ZnTe films are investigated. A substrate surface treatment using diluted HF solution plays a key role in growing device-quality ZnTe layers. X-ray diffraction analysis of ZnTe epilayers based on the crystal-truncation-rod method suggests that a homoepitaxial ZnTe film grown on a HF-treated substrate can be regarded as an ideal truncated crystal without an interfacial layer, while a ZnTe layer grown on a substrate without HF treatment suggests the presence of an interfacial layer which may lead to degraded crystallinity of ZnTe overlayers. The crystal quality of the homoepitaxial ZnTe layers with HF treatments are characterized by an extremely narrow x-ray diffraction linewidth of 15.6 arcsec and dominant very sharp excitonic emission lines with dramatically reduced deep-level emission intensity in the photoluminescence (PL) spectrum. Three bound excitonic emission lines at neutral acceptors are observed in the PL from the high-quality ZnTe homoepitaxial layers in addition to the free-exciton emission line, suggesting the presence of three different kinds of residual acceptor impurities. © 2000 American Institute of Physics.
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68.55.-a Thin film structure and morphology
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
81.05.Dz II-VI semiconductors
81.65.-b Surface treatments
71.35.-y Excitons and related phenomena
71.55.Gs II-VI semiconductors

Frequency doubling and tripling of terahertz radiation in a GaAs/AlAs superlattice due to frequency modulation of Bloch oscillations

S. Winnerl, E. Schomburg, S. Brandl, O. Kus, K. F. Renk, M. C. Wanke, S. J. Allen, A. A. Ignatov, V. Ustinov, A. Zhukov, and P. S. Kop’ev

Appl. Phys. Lett. 77, 1259 (2000); http://dx.doi.org/10.1063/1.1290141 (3 pages) | Cited 19 times

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We report on frequency doubling and tripling of THz radiation in a voltage-biased GaAs/AlAs superlattice. By use of a corner cube antenna system, radiation from the Santa Barbara free-electron laser (frequency 0.7 THz) was guided into a superlattice mesa element and the second and third harmonic were coupled out of the mesa. Without bias only radiation of the third harmonic was generated, while the biased superlattice emitted radiation of both the second and third harmonic. We attribute the harmonic generation to frequency modulation of damped Bloch oscillations of the miniband electrons in the superlattice. © 2000 American Institute of Physics.
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73.50.Mx High-frequency effects; plasma effects
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.61.Ey III-V semiconductors
78.70.Gq Microwave and radio-frequency interactions
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
84.40.-x Radiowave and microwave (including millimeter wave) technology

Spectral properties of resonant-cavity, polyfluorene light-emitting diodes

R. B. Fletcher, D. G. Lidzey, D. D. C. Bradley, M. Bernius, and S. Walker

Appl. Phys. Lett. 77, 1262 (2000); http://dx.doi.org/10.1063/1.1287402 (3 pages) | Cited 33 times

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We report on the fabrication and device properties of light-emitting resonant cavity conjugated-polymer diodes. The microcavity structures were constructed using a dielectric mirror, an indium–tin–oxide anode, a green light-emitting polyfluorene blend, and a metal (cathode) mirror. The best performance was obtained for a composite calcium–aluminum cathode, that combines high reflectivity with a low workfunction. This structure emitted electroluminescence with a linewidth of 12 nm and a maximum brightness of 300 cd m−2 at a bias of 35 V with an efficiency of 0.95 cd A−1. © 2000 American Institute of Physics.
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85.60.Jb Light-emitting devices
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Experimental observation of a “convective cell” in electron phase space in an inductively coupled radio-frequency plasma

U. Kortshagen and B. Heil

Appl. Phys. Lett. 77, 1265 (2000); http://dx.doi.org/10.1063/1.1289905 (3 pages) | Cited 2 times

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Spatially resolved two-dimensional Langmuir-probe measurements of energy-resolved electron fluxes have been performed in an inductively coupled radio-frequency plasma. A flux pattern reminiscent of a “convection cell” in energy-configuration space has been observed. The measurements are interpreted in terms of a total-energy picture of the plasma electrons. © 2000 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
52.25.Fi Transport properties
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InGaN/GaN quantum wells grown by molecular-beam epitaxy emitting from blue to red at 300 K

B. Damilano, N. Grandjean, J. Massies, L. Siozade, and J. Leymarie

Appl. Phys. Lett. 77, 1268 (2000); http://dx.doi.org/10.1063/1.1289915 (3 pages) | Cited 40 times

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InGaN/GaN quantum wells (QWs) were grown by molecular-beam epitaxy on c-plane sapphire substrates. The growth of InGaN is carried out at 550 °C with a large V/III ratio to counteract the low efficiency of NH3 at that temperature and to promote the two-dimensional mode of growth. An In composition of 16%±2% was determined by high-resolution x-ray diffraction experiments. Room-temperature photoluminescence of InGaN/GaN single QWs can be obtained over the whole visible spectrum (from 0.4 to 0.66 μm) by varying the well thickness from 1 to 5 nm. These heterostructures exhibit very large Stokes shifts between the emission and the absorption edge energies. © 2000 American Institute of Physics.
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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
81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Microheterogeneity and relaxation in 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 relaxor single crystals

F. M. Jiang and S. Kojima

Appl. Phys. Lett. 77, 1271 (2000); http://dx.doi.org/10.1063/1.1289909 (3 pages) | Cited 32 times

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Micro-Brillouin scattering has been applied to the observation of the microheterogeneity and the fast relaxation of 0.65 Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 single crystals in various microareas with the size of 1–2 μm. Cubic–tetragonal at TC–T and tetragonal–rhombohedral around TT–R transitions show different types of acoustic anomalies. It was found that local symmetry varies from one microarea to others below TC–T. Intense quasielastic scattering was observed below 250 °C; it is correlated with thermally activated fast relaxations of polar microregions. The results show that microheterogeneity and related dynamics of polar microregions are origins of relaxor phase transitions and are responsible for macroscopic properties like hypersonic damping. © 2000 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.B- Phase transitions and Curie point
77.22.Gm Dielectric loss and relaxation
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Chemical mapping and formation of V-defects in InGaN multiple quantum wells

Nikhil Sharma, Paul Thomas, David Tricker, and Colin Humphreys

Appl. Phys. Lett. 77, 1274 (2000); http://dx.doi.org/10.1063/1.1289904 (3 pages) | Cited 49 times

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InGaN multiple-quantum-well structures grown by metal–organic chemical-vapor deposition on GaN and capped by p-type GaN are found to contain inverted pyramids of indium-free GaN. High-resolution structural and chemical analyses of these “V-defects” by a number of complementary transmission electron microscopy techniques show that the InGaN quantum wells end abruptly at the V-defect interfaces, which lie on {10–11} planes. Each V-defect has at its center a threading edge dislocation, indicating that the defects are initiated at edge dislocation cores in the presence of indium. The lower temperatures of InGaN/GaN quantum-well growth (790 °C/950 °C) assist the formation of V-pits, which are subsequently filled in during the growth at higher temperature (1045 °C) of the p-type capping layer. © 2000 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
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Comparison of the effect of boron and nitrogen incorporation on the nucleation behavior and electron-field-emission properties of chemical-vapor-deposited diamond films

I-Nan Lin, Kuoguang Perng, Lien-Hsin Lee, Chuan-Feng Shih, Kuo-Shung Liu, Gariant A. Evans, and John W. Steeds

Appl. Phys. Lett. 77, 1277 (2000); http://dx.doi.org/10.1063/1.1289903 (3 pages) | Cited 7 times

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Effect of boron (or nitrogen) doping on the nucleation behavior of chemical-vapor-deposited diamond films was investigated. It is observed that inclusion of B(OCH3)3 species in gases markedly enhances, whereas addition of (NH3)2CO species pronouncedly retards the nucleation of diamonds. Raman spectroscopic analyses reveal that the probable mechanism is the formation of boron–carbon clusters due to boron incorporation. While the boron (or nitrogen) species incorporated insignificantly modify the microstructure, these dopants markedly alter the electron-field-emission behavior of the diamond films. The field-emission properties are optimized for films grown with B(OCH3)3=2 sccm [or (NH3)2CO = 6 sccm]. The nitrogen-doped films exhibit significantly superior electron-field-emission capacity to the boron-doped films, even though the latter possess much lower electrical resistivity [viz. (Je)n = 1020 μA/cm2, (ρ)n = 76 mΩ cm and (Je)b = 360 μA/cm2, (ρ)b = 2.1 mΩ cm]. © 2000 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
68.55.-a Thin film structure and morphology
73.61.Cw Elemental semiconductors
81.05.Cy Elemental semiconductors
61.72.up Other materials
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.ub Fullerenes and related materials
78.30.Am Elemental semiconductors and insulators
78.66.Db Elemental semiconductors and insulators

Effect of rapid thermal annealing on GaInNAs/GaAs quantum wells grown by plasma-assisted molecular-beam epitaxy

Z. Pan, L. H. Li, W. Zhang, Y. W. Lin, R. H. Wu, and W. Ge

Appl. Phys. Lett. 77, 1280 (2000); http://dx.doi.org/10.1063/1.1289916 (3 pages) | Cited 78 times

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We have studied the effect of rapid thermal annealing (RTA) on GaInNAs/GaAs quantum wells (QWs) grown by molecular-beam epitaxy using a dc plasma as the N source. It was found that RTA at low temperature (LT, 650 °C) and high temperature (HT, 900 °C) could both improve the QW quality significantly. To clarify the mechanism of quality improvement by RTA, a magnetic field perpendicular to the path of the N plasma flux was applied during the growth of the GaInNAs layers for the sake of comparison. It was found that LT-RTA mainly removed dislocations at interfaces related to the ion bombardment, whereas, HT-RTA further removed dislocations originating from the growth. LT-RTA caused only a slight blueshift of photoluminescence peak wavelength, probably due to defect-assisted interdiffusion of In–Ga at the QW interfaces. The blueshift caused by HT-RTA, on the other hand, was much larger. It is suggested that this is due to the fast defect-assisted diffusion of N–As at the QW interfaces. As defects are removed by annealing, the diffusion of In–Ga at interfaces would be predominant. © 2000 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.72.Cc Kinetics of defect formation and annealing
68.35.Fx Diffusion; interface formation
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
42.55.Px Semiconductor lasers; laser diodes
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Optical gate action of a molecular thin film probed with femtosecond near-field optical microscopy

H. Kawashima, M. Furuki, S. Tatsuura, M. Tian, Y. Sato, L. S. Pu, and T. Tani

Appl. Phys. Lett. 77, 1283 (2000); http://dx.doi.org/10.1063/1.1289902 (3 pages) | Cited 9 times

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We have combined a near-field scanning optical microscope with a two-color time-resolved pump–probe measurement system. The sample was a molecular thin film that revealed an excitonic resonance and also had a characteristic domain structure. The measurement system has a noise-equivalent transmittance change as small as 5.0×10−5 for a probe pulse with an intensity of 30 nW, which allows us to detect an optical gate action of a single domain. The results suggest that the film composition is uniform over a distance of several microns while it may vary on a greater scale. © 2000 American Institute of Physics.
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78.47.-p Spectroscopy of solid state dynamics
78.66.Qn Polymers; organic compounds
42.65.Pc Optical bistability, multistability, and switching, including local field effects
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
07.79.Fc Near-field scanning optical microscopes
07.60.Dq Photometers, radiometers, and colorimeters
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

High-resolution microbeam x-ray diffractometry applied to InGaAsP/InP layers grown by narrow-stripe selective metal-organic vapor phase epitaxy

Shigeru Kimura, Hidekazu Kimura, Kenji Kobayashi, Tomoaki Oohira, Koich Izumi, Yasutaka Sakata, Yoshiyuki Tsusaka, Kazushi Yokoyama, Shingo Takeda, Masafumi Urakawa, Yasushi Kagoshima, and Junji Matsui

Appl. Phys. Lett. 77, 1286 (2000); http://dx.doi.org/10.1063/1.1290048 (3 pages) | Cited 10 times

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We measure the diffraction peaks of InGaAsP selective metal-organic vapor-phase epitaxial layers on 1.7-μm-wide InP stripe regions between a pair of SiO2 mask stripes. This is achieved by using an x-ray microbeam with low angular divergence and a narrow energy bandwidth that was produced through two-dimensional condensation of undulator radiation x rays from a synchrotron light source using successive asymmetric diffraction. The lattice strain is investigated by changing the SiO2 mask width from 4 to 40 μm. The rocking curves reveal clear peak shifts in the InGaAsP layers from the higher angle side to the lower angle side of the InP substrate peaks as the mask width increases. © 2000 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.05.Ea III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Epitaxial growth of laminar crystalline silicon on CaF2

B. R. Schroeder, Shuang Meng, A. Bostwick, Marjorie A. Olmstead, and Eli Rotenberg

Appl. Phys. Lett. 77, 1289 (2000); http://dx.doi.org/10.1063/1.1290158 (3 pages) | Cited 9 times

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Si heteroepitaxy on CaF2 was studied with x-ray photoelectron spectroscopy and diffraction and low-energy electron diffraction to determine the interface bonding and silicon overlayer growth mode. The CaF2 surface was prepared by irradiation with low-energy electrons and exposure to arsenic, which replaced surface fluorine atoms with arsenic. Thin Si films (1.3 nm) were subsequently deposited at 550 °C. The Si films completely cover the CaF2 substrate and have a type-B orientation. The resultant interface has Si–Ca bonds, with the As surfactant layer terminating the Si surface in a 1×1 structure. © 2000 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.05.Cy Elemental semiconductors
79.60.Jv Interfaces; heterostructures; nanostructures
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.35.Ct Interface structure and roughness
61.80.Fe Electron and positron radiation effects
68.35.B- Structure of clean surfaces (and surface reconstruction)

Blue-emitting β-SiC fabricated by annealing C60 coupled on porous silicon

X. L. Wu, G. G. Siu, M. J. Stokes, D. L. Fan, Y. Gu, and X. M. Bao

Appl. Phys. Lett. 77, 1292 (2000); http://dx.doi.org/10.1063/1.1290153 (3 pages) | Cited 29 times

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C60 molecules were chemically coupled in the pores of porous Si through a coupling agent and then coated with a layer of Si, and followed by N2 annealing. X-ray diffraction results indicate that the fabricated samples contain β-SiC particles which may exist in the pores, in addition to Si, SiO2, and graphite. The photoluminescence (PL) spectra show an asymmetrical broadband, which can be Gaussian divided into two bands at 380 (3.26 eV) and 454 (2.73 eV) nm. Spectral analyses and the experimental results from infrared spectroscopy and PL excitation measurements suggest that the 380 nm PL band is related to oxygen-vacancy defects in the SiO2 matrix, whereas the blue PL band is closely connected with the β-SiC particles. Our experiments provide a way for fabricating stable blue-emitting β-SiC materials. © 2000 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
78.30.Hv Other nonmetallic inorganics
71.55.Ht Other nonmetals
81.05.Rm Porous materials; granular materials
61.72.Cc Kinetics of defect formation and annealing
61.72.J- Point defects and defect clusters

Strain status of self-assembled InAs quantum dots

K. Zhang, Ch. Heyn, W. Hansen, Th. Schmidt, and J. Falta

Appl. Phys. Lett. 77, 1295 (2000); http://dx.doi.org/10.1063/1.1290152 (3 pages) | Cited 12 times

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Grazing incidence x-ray diffraction experiments employing the asymmetric (202) Bragg diffraction have been performed to characterize self-assembled InAs quantum dots grown by molecular-beam epitaxy. We find that the strain is elastically relaxed with different components. The volume distribution of partially strained InAs inside islands is peaked at intermediate strain values. The fraction of both almost fully strained and totally relaxed InAs is found to be small. In addition, a small volume fraction of relaxed InxGa1−xAs is found. © 2000 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation

A Brillouin study of the angular dispersion of generalized surface and pseudosurface acoustic waves on the (001) surface of InSb

M. H. Kuok, S. C. Ng, and V. L. Zhang

Appl. Phys. Lett. 77, 1298 (2000); http://dx.doi.org/10.1063/1.1290270 (3 pages) | Cited 6 times

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The velocity angular dispersion of the generalized surface (GSW) and pseudosurface (PSW) acoustic waves on the (001) plane of InSb has been measured by Brillouin scattering. The complete range of angular dispersion of these waves on the (001) plane of an anisotropic cubic crystal has been experimentally determined. The p–p and p–s polarization results accord well with theory. In particular, the measured angular dispersion of these surface modes traces out two separate and distinct branches, in contrast to one single curve arising from the branching from GSW to PSW, normally observed for anisotropic cubic crystals. © 2000 American Institute of Physics.
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68.35.Gy Mechanical properties; surface strains
43.35.Pt Surface waves in solids and liquids
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Structural and luminescence properties of nanostructured ZnS:Mn

Daisuke Adachi, Shigeki Hasui, Toshihiko Toyama, and Hiroaki Okamoto

Appl. Phys. Lett. 77, 1301 (2000); http://dx.doi.org/10.1063/1.1290274 (3 pages) | Cited 25 times

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We have studied structural and luminescence properties of nanostructured (NS-) ZnS:Mn which has potential applications in thin-film electroluminescence (TFEL) devices. As a NS-ZnS:Mn system, a ZnS:Mn/Si3N4 multilayer having thicknesses of 2.5 nm for ZnS and 0.6 nm for Si3N4 was prepared by a conventional rf-magnetron sputtering method. Grazing incidence x-ray reflectometry and x-ray diffractometry show that ZnS:Mn nanocrystals were formed between the amorphous Si3N4 layers. Photoluminescence intensity associated with the Mn2+ transitions per total thickness of the ZnS:Mn layers is increased in NS-ZnS:Mn in comparison with that of the ZnS:Mn thin film, indicating the effects due to quantum confinement. The TFEL device with NS-ZnS:Mn as an emission layer exhibits a reddish-orange broad band emission with the maximum luminance of 2.8 cd/m2 under the 1-kHz sinusoidal wave operation at a voltage of 20.5 V0−p. © 2000 American Institute of Physics.
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78.60.Fi Electroluminescence
68.55.-a Thin film structure and morphology
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
81.07.-b Nanoscale materials and structures: fabrication and characterization

Composition and its impact on shape evolution in dislocated Ge(Si)/Si islands

X. Z. Liao, J. Zou, D. J. H. Cockayne, Z. M. Jiang, X. Wang, and R. Leon

Appl. Phys. Lett. 77, 1304 (2000); http://dx.doi.org/10.1063/1.1290384 (3 pages) | Cited 43 times

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The composition distribution of Ge(Si)/Si (001) islands grown at 700 °C by molecular beam epitaxy is investigated using high-spatial resolution x-ray energy dispersive spectrometry in a scanning transmission electron microscope. Island shapes are investigated using cross-section transmission electron microscopy. Results show nonuniformity of the composition distribution in the islands, which affects the evolution of the aspect ratios of height-to-base diameter of dislocated islands. © 2000 American Institute of Physics.
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68.55.Nq Composition and phase identification
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
68.35.Ct Interface structure and roughness
81.05.Hd Other semiconductors

Carrier transfer and photoluminescence quenching in InAs/GaAs multilayer quantum dots

S. Sanguinetti, M. Padovani, M. Gurioli, E. Grilli, M. Guzzi, A. Vinattieri, M. Colocci, P. Frigeri, and S. Franchi

Appl. Phys. Lett. 77, 1307 (2000); http://dx.doi.org/10.1063/1.1290385 (3 pages) | Cited 13 times

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A detailed study of the carrier transfer and photoluminescence (PL) quenching in stacked InAs/GaAs quantum dots (QDs) is presented. Vertically aligned QD structures, grown by atomic layer molecular beam epitaxy, with different numbers N of dot planes and different spacer thicknesses (d) were prepared and studied. The dependencies of carrier transfer from the GaAs barriers to the InAs QDs and of the PL quenching channels on the design parameters N and d have been identified by performing continuous wave and time-resolved PL measurements. We have found that both the radiative recombination and capture efficiency into the QDs are reduced by increasing N and by decreasing d, as a consequence of the deterioration of the interdot GaAs spacers induced by stacking. © 2000 American Institute of Physics.
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73.61.Ey III-V semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.50.Dn Low-field transport and mobility; piezoresistance

Substitutional C fraction and the influence of C on Si dimer diffusion in Si1−yCy alloys grown on (001) and (118) Si

E. T. Croke, F. Grosse, J. J. Vajo, M. F. Gyure, M. Floyd, and David J. Smith

Appl. Phys. Lett. 77, 1310 (2000); http://dx.doi.org/10.1063/1.1287728 (3 pages) | Cited 4 times

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The dependence of substitutional C fraction on growth temperature and substrate orientation is measured for Si1−yCy alloy films grown on (001) and (118) Si by molecular-beam epitaxy. Secondary ion mass spectrometry and high-resolution x-ray diffraction were used to measure the total C and the substitutional C concentrations, respectively, in several samples prepared at temperatures between 450 and 650 °C. The substitutional C fraction decreased rapidly with increasing temperature in this range, regardless of orientation, and was slightly lower for growth on (118) Si. Cross-sectional transmission electron microscopy on (118)-oriented samples revealed a tendency for C to concentrate periodically on (001) facets which formed immediately after initiation of Si1−yCy growth. A kinetic Monte Carlo simulation based upon enhanced diffusion of Si dimers in the presence of subsurface C predicted a step instability leading to step bunching and the formation of periodic surface features, as well as the accumulation of high C concentrations on nearly (001) planes. © 2000 American Institute of Physics.
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68.55.Nq Composition and phase identification
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
66.30.H- Self-diffusion and ionic conduction in nonmetals
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.05.Hd Other semiconductors

Molecular wires, solenoids, and capacitors by sidewall functionalization of carbon nanotubes

Gotthard Seifert, Thomas Köhler, and Thomas Frauenheim

Appl. Phys. Lett. 77, 1313 (2000); http://dx.doi.org/10.1063/1.1289263 (3 pages) | Cited 26 times

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Theoretical investigations (density-functional tight binding) about the changes of the properties of single-wall carbon nanotubes (SWNTs) by fluorination are reported. It is shown that a sidewall functionalization of SWNTs may lead to tubes with a wide variety of electronic properties, ranging from insulating over semiconducting to a metallic-like behavior. Therefore, a chemical derivatization of SWNTs may open possibilities for tailoring the electronic properties of nanotubes, providing nanoscale wires, capacitors, and solenoids. © 2000 American Institute of Physics.
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61.48.-c Structure of fullerenes and related hollow and planar molecular structures
71.20.Tx Fullerenes and related materials; intercalation compounds
73.61.Wp Fullerenes and related materials
85.65.+h Molecular electronic devices
81.05.ub Fullerenes and related materials
84.32.Tt Capacitors
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