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10 Jul 2000

Volume 77, Issue 2, pp. 157-310

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Si1−xGex/Si resonant-cavity-enhanced photodetectors with a silicon-on-oxide reflector operating near 1.3 μm

Cheng Li, Qinqing Yang, Hongjie Wang, Jialian Zhu, Liping Luo, Jinzhong Yu, Qiming Wang, Yongkang Li, Junming Zhou, and Chenglu Lin

Appl. Phys. Lett. 77, 157 (2000); http://dx.doi.org/10.1063/1.126909 (3 pages) | Cited 8 times

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We report on a Si1−xGex/Si multiple quantum-well resonant-cavity-enhanced (RCE) photodetector with a silicon-on-oxide reflector as the bottom mirror operating near 1.3 μm. The breakdown voltage of the photodetector is above 18 V and the dark current density at 5 V reverse bias is 12 pA/μm2. The RCE photodetector shows enhanced responsivity with a clear peak at 1.285 μm and the peak responsivity is measured around 10.2 mA/W at a reverse bias of 5 V. The external quantum efficiency at 1.3 μm is measured to be 3.5% under reverse bias of 16 V, which is enhanced three- to fourfold compared with that of a conventional p-i-n photodetector with a Ge content of 0.5 reported in 1995 by Huang et al. [Appl. Phys. Lett. 67, 566 (1995)]. © 2000 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
42.79.Bh Lenses, prisms and mirrors

Highly efficient blue-green emission from organic light-emitting diodes using dibenzochrysene derivatives

Shizuo Tokito, Koji Noda, Hisayoshi Fujikawa, Yasunori Taga, Makoto Kimura, Kou Shimada, and Yasuhiko Sawaki

Appl. Phys. Lett. 77, 160 (2000); http://dx.doi.org/10.1063/1.126910 (3 pages) | Cited 14 times

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We have fabricated highly efficient organic light-emitting diodes (OLEDs) using new hole-transporting emissive materials based on dibenzochrysene. Hole drift mobilities of the dibenzochrysene derivatives were measured in the vacuum-deposited films and found to be 5×10−4–2×10−3 cm2/V s (at 5×105 V/cm). The OLEDs consist of an emitting layer of the dibenzochrysene derivative and an electron-transport layer of tris(8-quinolinolato) aluminum. Emission colors of the OLEDs were blue-green and their spectra were consistent with the photoluminescence spectra with a peak wavelength of 490 nm. High external quantum efficiency of 2% was obtained at a luminance of 300 cd/m2, and good durability in a continuous operation at room temperature and high temperatures was achieved. © 2000 American Institute of Physics.
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85.60.Jb Light-emitting devices
42.79.Wc Optical coatings
78.55.Kz Solid organic materials
78.66.Qn Polymers; organic compounds

Modal gain and internal optical mode loss of a quantum dot laser

E. Herrmann, P. M. Smowton, H. D. Summers, J. D. Thomson, and M. Hopkinson

Appl. Phys. Lett. 77, 163 (2000); http://dx.doi.org/10.1063/1.126911 (3 pages) | Cited 12 times

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The modal gain spectra and internal optical mode loss of a semiconductor laser structure containing a single layer of InGaAs quantum dots have been measured independently and directly as a function of current density. The quantum dot gain exhibits no obvious polarization dependence. The maximum modal gain of (11±4) cm−1 obtained from the ground state of a single layer of quantum dots is in this case insufficient for lasing operation since the internal optical mode loss measured on the same sample is (11±4) cm−1. As expected laser emission is not observed from the dot ground state, but from the excited dot state or from the wetting layer depending on device length. © 2000 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
42.60.By Design of specific laser systems

Molecular alignment in submicron patterned polymer matrix using nanoimprint lithography

Jian Wang, Xiaoyun Sun, Lei Chen, Lei Zhuang, and Stephen Y. Chou

Appl. Phys. Lett. 77, 166 (2000); http://dx.doi.org/10.1063/1.126912 (3 pages) | Cited 10 times

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We report a promising approach to align molecules in a polymer film patterned by nanoimprint lithography. We found that molecules and chromophores are spontaneously aligned in the plane of the film during the nanopatterning process. Since the polymer–chromophore (called guest–host) system plays an important role in the field of nonlinear optics and organic optoelectronics, in this letter we present a technique to combine the high-resolution patterning capability of nanoimprint lithography with the ability to control molecule and chromophore orientation. It opens up a way to realize new molecular electronic and optoelectronic devices. © 2000 American Institute of Physics.
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85.40.Hp Lithography, masks and pattern transfer
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

Monolithic active mode locking of quantum cascade lasers

Roberto Paiella, Federico Capasso, Claire Gmachl, Harold Y. Hwang, Deborah L. Sivco, Albert L. Hutchinson, Alfred Y. Cho, and H. C. Liu

Appl. Phys. Lett. 77, 169 (2000); http://dx.doi.org/10.1063/1.126913 (3 pages) | Cited 21 times

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We demonstrate active mode locking of a high-speed 8 μm quantum cascade laser in a monolithic configuration, at a repetition rate of 11.6 GHz. Evidence of mode locking is obtained from the measured optical spectra and corresponding interferograms, as well as from the power spectra of the photocurrent detected with a fast quantum-well infrared photodetector. An estimate for the pulse width of approximately 5 ps is inferred from the experimental results. Mode-locked operation is observed up to a maximum temperature of over 120 K. © 2000 American Institute of Physics.
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42.60.Fc Modulation, tuning, and mode locking
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Temperature characteristics of bipolar cascade lasers

S. G. Patterson, E. K. Lau, K. P. Pipe, and R. J. Ram

Appl. Phys. Lett. 77, 172 (2000); http://dx.doi.org/10.1063/1.126914 (3 pages) | Cited 3 times

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The temperature characteristics of bipolar cascade lasers operating up to 80 °C with room temperature, continuous-wave differential slope efficiencies of 93%, are reported. The continuous-wave characteristic lasing threshold temperature, T0, of the device is found to be 103 K for heatsink temperatures below 40 °C, dropping to 56 K for heatsink temperatures in the range 50–80 °C. Two separate regions are found to exist for the characteristic temperature of the differential slope efficiency, T1. The temperature of the topside metal contact versus bias was measured directly using a microthermocouple probe. Finite element modeling showed good agreement with measured surface temperatures. The simulations indicate that, prior to the onset of lasing in the bottom active region, nonradiative recombination heating in the bottom active region significantly heats the (lasing) top active region, leading to a reduction in the differential slope efficiency of the bipolar cascade laser. © 2000 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.)
02.70.Dh Finite-element and Galerkin methods
42.55.Ah General laser theory
85.30.De Semiconductor-device characterization, design, and modeling

Room-temperature operation at 333 nm of Al0.03Ga0.97N/Al0.25Ga0.75N quantum-well light-emitting diodes with Mg-doped superlattice layers

A. Kinoshita, H. Hirayama, M. Ainoya, Y. Aoyagi, and A. Hirata

Appl. Phys. Lett. 77, 175 (2000); http://dx.doi.org/10.1063/1.126915 (3 pages) | Cited 71 times

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We demonstrate room-temperature deep ultraviolet (UV) current injection emission from Al0.03Ga0.97N/Al0.25Ga0.75N multiquantum-well (MQW) light-emitting diodes (LEDs) fabricated by metalorganic vapor phase epitaxy. The electroluminescence (EL) peaked at 333.0 nm under pulsed current injection. To our knowledge, this is the shortest wavelength ever reported for nitride QW LEDs. A Mg-doped GaN/AlGaN superlattice (SL) hole conductive layer was used as a p-type layer in order to enable current injection into such deep-level AlGaN QWs. We observed single-peak near band-edge emission from the QWs. The output intensity did not saturate up to current densities of 0.33 kA/cm2. We obtained a reasonable well width dependence on the EL peak wavelength of Al0.01Ga0.99N MQW LEDs, which confirms that the main emission peak originates from the QW regions. These results revealed that the Mg-doped SL hole conductive layers are highly suitable for application to GaN-based UV light-emitting devices. © 2000 American Institute of Physics.
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85.60.Jb Light-emitting devices

Heavy photon dispersions in photonic crystal waveguides

V. N. Astratov, R. M. Stevenson, I. S. Culshaw, D. M. Whittaker, M. S. Skolnick, T. F. Krauss, and R. M. De La Rue

Appl. Phys. Lett. 77, 178 (2000); http://dx.doi.org/10.1063/1.126916 (3 pages) | Cited 39 times

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Heavy photon dispersion curves exhibiting group velocities suppressed by two orders of magnitude are measured directly for deeply etched AlGaAs waveguide structures by means of surface coupling techniques. It is shown that due to the wave vector-selective nature of surface coupling, such techniques permit the excitation of modes of specific, known dispersion in photonic crystal waveguides. Coupling to regions of very strong anomalous dispersion is demonstrated, with potential to be developed into a method for excitation of gap solitons. © 2000 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.79.Gn Optical waveguides and couplers
42.65.Tg Optical solitons; nonlinear guided waves
78.66.Fd III-V semiconductors

Second-harmonic spectroscopy of bulk boron-doped Si(001)

D. Lim, M. C. Downer, and J. G. Ekerdt

Appl. Phys. Lett. 77, 181 (2000); http://dx.doi.org/10.1063/1.126917 (3 pages) | Cited 9 times

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The effect of bulk boron incorporation on the second-harmonic generation (SHG) spectrum of Si(001) films grown epitaxially by chemical vapor deposition is studied as a function of doping level and temperature. At room temperature, boron doping (NA ∼ 1018 cm−3) strongly enhances and blueshifts the E1 resonance of the second-harmonic generation spectra to 3.4 eV. Surface hydrogen termination reverses this effect. The observed doping and temperature dependence are modeled as electric-field-induced SHG in the bulk depletion region. The results suggest applications of SHG as an in situ, noninvasive probe of electrically active dopants. © 2000 American Institute of Physics.
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78.66.Db Elemental semiconductors and insulators
71.55.Cn Elemental semiconductors
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.uf Ge and Si

Laser emission from quantum dots in microdisk structures

P. Michler, A. Kiraz, Lidong Zhang, C. Becher, E. Hu, and A. Imamoglu

Appl. Phys. Lett. 77, 184 (2000); http://dx.doi.org/10.1063/1.126918 (3 pages) | Cited 72 times

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We report optically pumped continuous-wave lasing from self-assembled InAs and InGaAs quantum dots (QDs) embedded in high-quality-factor microdisk laser structures. The microdisk emission spectra show lasing on 1–5 well separated modes in the wavelength range between 900 and 990 nm. The estimated threshold pump densities are between 20 and 200 W/cm2. The lasing characteristics are discussed in terms of both inhomogeneously and homogeneously broadened QD transitions. © 2000 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.55.Sa Microcavity and microdisk lasers
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.60.By Design of specific laser systems
42.60.Pk Continuous operation
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Green II–VI light emitting diodes with long lifetime on InP substrate

W. Faschinger and J. Nürnberger

Appl. Phys. Lett. 77, 187 (2000); http://dx.doi.org/10.1063/1.126919 (3 pages) | Cited 25 times

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We demonstrate that the quaternary compound ZnMgSeTe can be grown by molecular beam epitaxy in reasonable quality. For layers with energy gaps as high as 3.1 eV, nitrogen doping leads to free hole concentrations around 1018 cm−3. In combination with n-ZnMgCdSe, this material allows the fabrication of II–VI diodes lattice matched to InP substrate. Light emitting diodes containing a tensile strained ZnCdSe quantum well in ZnMgCdSe emit green light when operated in forward direction. In contrast to diodes with a comparable density of extended defects grown on GaAs substrate, these diodes show no formation of dark line defects and a lifetime which is about three orders of magnitude longer. © 2000 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.66.Hf II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.60.Fi Electroluminescence
81.05.Dz II-VI semiconductors

Strong enhancement of second-order response coefficients in tellurium containing Ag–III–VI2 compounds

Sergey N. Rashkeev and Walter R. L. Lambrecht

Appl. Phys. Lett. 77, 190 (2000); http://dx.doi.org/10.1063/1.126920 (3 pages) | Cited 10 times

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First-principles calculations of the second-order optical response coefficients are reported for Ag–III–VI2 compounds with III=Ga, In and VI=S, Se, Te. While both the substitutions of In for Ga and Te for Se or S lower the band gap by similar amounts, the substitution of Se by Te is significantly more favorable for increasing χ(2). The enhancement of χ(2) by a factor 2 from AgGaSe2 to AgGaTe2 is surprising compared to the only modest enhancement obtained in II–VI compounds. The origin of these enhancements is analyzed in terms of the frequency-dependent response functions and the band structures. © 2000 American Institute of Physics.
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42.65.An Optical susceptibility, hyperpolarizability
71.20.Nr Semiconductor compounds

Photonic band gaps and flat band edges in periodically textured metallic microcavities

M. G. Salt, W. C. Tan, and W. L. Barnes

Appl. Phys. Lett. 77, 193 (2000); http://dx.doi.org/10.1063/1.126921 (3 pages) | Cited 4 times

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The dispersion of optical modes in metallic microcavities is shown to be dramatically altered when wavelength-scale periodic texture is added to one of the cavity mirrors. We demonstrate that Bragg scattering of the cavity modes by such microstructure produces near-flat bands that remain significantly flat well away from the first Brillouin zone boundary. The electric fields associated with these modes are studied and are found to have field maxima that are enhanced over those pertaining to planar microcavities. The impact of this band structure upon emissive devices, especially in terms of the clear insensitivity to viewing angle, is discussed. © 2000 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.79.Bh Lenses, prisms and mirrors
78.66.Bz Metals and metallic alloys
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In situ observation of nucleation and subsequent growth of clusters in silane radio frequency discharges

Kazunori Koga, Yasuhiro Matsuoka, Kenichi Tanaka, Masaharu Shiratani, and Yukio Watanabe

Appl. Phys. Lett. 77, 196 (2000); http://dx.doi.org/10.1063/1.126922 (3 pages) | Cited 24 times

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Growth processes of clusters in low-pressure and low-power silane radio frequency discharges are studied by using the newly developed double-pulse-discharge method which realizes in situ measurement of their size and density in a size range of 0.5–4 nm. The clusters begin to be composed of two size groups at about 10 ms after the discharge initiation: clusters in the small size group have an almost constant average size of about 0.5 nm through the discharge period, while those in the large one grow at about 4 nm/s in a monodisperse way. Time evolution of the measured average sizes and densities in the groups is transformed into that of size distributions assuming that the density of SinHx clusters for the small group decreases exponentially with the increase in the number of Si atoms, n, of them, and the size distribution for the large group is the lognormal one. The results show that a critical cluster size for nucleation is SinHx (n ∼ 4). © 2000 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
81.10.Aj Theory and models of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation
81.07.-b Nanoscale materials and structures: fabrication and characterization
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Flexible microdischarge arrays: Metal/polymer devices

S.-J. Park, C. J. Wagner, C. M. Herring, and J. G. Eden

Appl. Phys. Lett. 77, 199 (2000); http://dx.doi.org/10.1063/1.126923 (3 pages) | Cited 36 times

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Flexible microdischarge arrays have been fabricated in metal–polymer–metal structures having a total thickness of ∼30 μm (∼1.2 mils). Composed of individual cylindrical devices having a diameter of 150 μm, positive differential resistance (30–120 kΩ), and operating voltages as low as 114 V for a 5 μm thick dielectric layer, the arrays operate at pressures beyond 700 Torr of Ne and in 1 atm of air. For Ne pressures ⩽ 200 Torr, emission is produced from Ne ion excited states lying more than 55 eV above the neutral ground state (2p6). The structures reported here are inexpensive to fabricate and have lifetimes beyond 50 h. Arrays that have been sealed by conventional lamination have also been operated successfully. © 2000 American Institute of Physics.
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85.45.Bz Vacuum microelectronic device characterization, design, and modeling
85.45.Db Field emitters and arrays, cold electron emitters
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Quantitative evaluation of growth-induced residual stress in InP epitaxial micromechanical structures

N. Chitica, M. Strassner, and J. Daleiden

Appl. Phys. Lett. 77, 202 (2000); http://dx.doi.org/10.1063/1.126924 (3 pages) | Cited 14 times

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We have investigated the residual stress distribution and its relation to the presence of impurity atoms in InP layers grown by metalorganic vapor phase epitaxy (MOVPE) on top of lattice-matched GaInAs layers. The homogeneous and gradient components of the stress have been directly measured using highly sensitive micromechanical test structures. Secondary ion mass spectrometry depth profiling of the composition evidenced that residual As and Ga atoms are present throughout the relatively thick (>0.5 μm) InP layers. Our investigations show that the distribution of these impurities accounts for the measured residual stress in the layers and, at the same time, it is specific to the MOVPE growth technique. © 2000 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
81.05.Ea III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
61.72.S- Impurities in crystals
07.10.Cm Micromechanical devices and systems
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Improvement of the interface quality during thermal oxidation of Al0.98Ga0.02As layers due to the presence of low-temperature-grown GaAs

J. C. Ferrer, Z. Liliental-Weber, H. Reese, Y. J. Chiu, and E. Hu

Appl. Phys. Lett. 77, 205 (2000); http://dx.doi.org/10.1063/1.126925 (3 pages) | Cited 9 times

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The role of a low-temperature-grown GaAs (LT GaAs) layer on the lateral oxidation of an Al0.98Ga0.02As/GaAs layer structure has been studied by transmission electron microscopy. Results show that structures incorporating LT GaAs develop better quality oxide/GaAs interfaces compared to reference samples without LT GaAs. While the latter have As accumulation in the vicinity of these interfaces, the structures with LT layers display sharper oxide–GaAs interfaces with a reduced concentration of As. These results are explained in terms of the high Ga vacancy concentration in the LT GaAs and the possible influence of those vacancies in enhancing As diffusion away from the oxide–semiconductor interface. © 2000 American Institute of Physics.
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81.65.Mq Oxidation
81.05.Ea III-V semiconductors
68.35.Ct Interface structure and roughness
61.72.J- Point defects and defect clusters

A technique to form a porous silicon layer with no backside contact by alternating current electrochemical process

A. El-Bahar and Y. Nemirovsky

Appl. Phys. Lett. 77, 208 (2000); http://dx.doi.org/10.1063/1.126926 (3 pages) | Cited 2 times

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We report here the formation of porous silicon under alternating current conditions. Instead of applying the usual direct current electrochemical process, an alternating current was applied with a given frequency and peak voltage. The porous silicon layer properties are equivalent to the properties that would be achieved by the standard direct current formation technique (i.e., same porosity level). The main advantages of this process are: (a) The alternating current formed porous silicon exhibits higher mechanical stability during the drying step than layers formed using the standard direct current technique. (b) The alternating current process can be performed without a deposited backside contact. These simplify the process and permit its integration with high temperature processing steps and clean furnaces of a modern very large sale-integrated technology. © 2000 American Institute of Physics.
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81.05.Cy Elemental semiconductors
81.15.Pq Electrodeposition, electroplating
81.05.Rm Porous materials; granular materials
68.55.-a Thin film structure and morphology
82.45.-h Electrochemistry and electrophoresis
68.60.Bs Mechanical and acoustical properties

Decay dynamics of visible luminescence in amorphous silicon nanoparticles

Yoshihiko Kanemitsu, Yunosuke Fukunishi, and Takashi Kushida

Appl. Phys. Lett. 77, 211 (2000); http://dx.doi.org/10.1063/1.126927 (3 pages) | Cited 13 times

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We have studied the recombination dynamics of carriers in amorphous silicon (a-Si) nanoparticles prepared by electrochemical anodization of hydrogenated a-Si films. The photoluminescence (PL) lifetime of the fast-decay component in a-Si nanoparticles is shorter than that in crystalline silicon (c-Si) nanoparticles. The energy dependence of the PL lifetime in a-Si nanoparticles is different from that in c-Si nanoparticles. The PL decay dynamics of a-Si nanoparticles is determined by recombination processes of carriers localized in the band-tail state. The origin of the blueshift of the PL spectrum in a-Si nanoparticles will be discussed. © 2000 American Institute of Physics.
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78.66.Jg Amorphous semiconductors; glasses
78.55.Ap Elemental semiconductors
78.66.Db Elemental semiconductors and insulators

Kinetic modeling of N incorporation in GaInNAs growth by plasma-assisted molecular-beam epitaxy

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

Appl. Phys. Lett. 77, 214 (2000); http://dx.doi.org/10.1063/1.126928 (3 pages) | Cited 41 times

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We have studied the growth of GaInNAs by a plasma-assisted molecular-beam epitaxy (MBE). It was found that the N-radicals were incorporated into the epitaxial layer like dopant atoms. In the range of 400–500 °C, the growth temperature (Tg) mainly affected the crystal quality of GaInNAs rather than the N concentration. The N concentration dropped rapidly when Tg exceeded 500 °C. Considering N desorption alone is insufficient to account for the strong falloff of the N concentration with Tg over 500 °C, the effect of thermally-activated N surface segregation must be taken into account. The N concentration was independent of the arsenic pressure and the In concentration in GaInNAs layers, but inversely proportional to the growth rate. Based on the experimental results, a kinetic model including N desorption and surface segregation was developed to analyze quantitatively the N incorporation in MBE growth. © 2000 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
64.75.-g Phase equilibria
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
82.20.Wt Computational modeling; simulation
61.66.Bi Elemental solids
61.66.Dk Alloys
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)

Drastic increase of the density of Ge islands by capping with a thin Si layer

N. Usami, M. Miura, Y. Ito, Y. Araki, and Y. Shiraki

Appl. Phys. Lett. 77, 217 (2000); http://dx.doi.org/10.1063/1.126929 (3 pages) | Cited 4 times

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Capping Ge islands with a thin Si layer was found to be very effective in increasing the density of islands. An increase of the density by a factor of 3 was observed in 4.5 monolayers (MLs) of Ge islands by capping with a 6 Å Si layer. In addition, the formation of islands was confirmed even for 2.7 ML Ge and a thin Si cap layer although the amount of Ge is smaller than the critical coverage of the island formation. Possible explanations for these phenomena are discussed based on coarsening of the islands and the intermixing effect. © 2000 American Institute of Physics.
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81.05.Cy Elemental semiconductors
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)

Reoxidation effects on the chemical bonding states of nitrogen accumulated at the oxynitride/silicon interface

Yoshinao Miura, Haruhiko Ono, and Koichi Ando

Appl. Phys. Lett. 77, 220 (2000); http://dx.doi.org/10.1063/1.126930 (3 pages) | Cited 13 times

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Nitrogen bonding states near oxynitride/Si interfaces in NO-nitrided oxide films were investigated by x-ray photoelectron spectroscopy (XPS). A reoxidation process was used to change the nitrogen location in the depth profile. Charge-up effects on the XPS spectra were removed by considering a highly nonuniform nitrogen distribution. We found that the N 1s core-level shifts to a higher energy by 0.4 eV as the interfacial nitrogen is incorporated into the oxide during the reoxidation. It was also shown that the chemical environment of the interfacial nitrogen differs from that in Si3N4. We attribute this gradual chemical shift to the difference in the second nearest neighbor atoms surrounding the nitrogen. © 2000 American Institute of Physics.
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68.35.Ct Interface structure and roughness
81.05.Cy Elemental semiconductors
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.65.Mq Oxidation
61.50.Lt Crystal binding; cohesive energy
79.60.Jv Interfaces; heterostructures; nanostructures
73.20.At Surface states, band structure, electron density of states

Configurations of misfit dislocations at interfaces of lattice-matched Ga0.5In0.5P/GaAs heterostructures

Y. Q. Wang, Z. L. Wang, T. Brown, A. Brown, and G. May

Appl. Phys. Lett. 77, 223 (2000); http://dx.doi.org/10.1063/1.126931 (3 pages) | Cited 8 times

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A configuration of misfit dislocation dipoles is observed in a Ga0.5In0.5P heterostructure grown by solid-source molecular-beam epitaxy on GaAs. The dipole dislocations are mostly of 60° type, separated by ∼3.5 nm. The dislocations are not produced by conventional lattice mismatch, rather, they could be the result of lateral compositional modulation in the Ga0.5In0.5P epilayer. © 2000 American Institute of Physics.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.05.Ea III-V semiconductors
68.35.Ct Interface structure and roughness

Ion-beam synthesis of epitaxial silicon carbide in nitrogen-implanted diamond

V. Heera, F. Fontaine, W. Skorupa, B. Pécz, and Á. Barna

Appl. Phys. Lett. 77, 226 (2000); http://dx.doi.org/10.1063/1.126932 (3 pages) | Cited 8 times

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Natural IIa diamond was implanted at 90 keV to 1×1015 N+/cm2 and subsequently at 150 keV to 3×1017 Si+/cm2 at a temperature of 900 °C. The structure of the implanted diamond region was investigated by high-resolution cross-sectional transmission electron microscopy, Raman, and infrared absorption spectrometry. A buried layer with crystalline 3C–SiC domains in perfect epitaxial relation to the diamond substrate was detected. Amorphization and graphitization were completely prevented by the elevated temperature during the implantation. Resistance measurements demonstrated low electrical resistivity in the implanted regions. © 2000 American Institute of Physics.
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81.05.Hd Other semiconductors
61.72.up Other materials
81.15.Np Solid phase epitaxy; growth from solid phases
78.30.Hv Other nonmetallic inorganics

Confinement of phonons in InGaAs/InP superlattices

H. K. Shin, D. J. Lockwood, and P. J. Poole

Appl. Phys. Lett. 77, 229 (2000); http://dx.doi.org/10.1063/1.126933 (3 pages) | Cited 5 times

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A comparison is presented of optical mode Raman spectra of an In0.48Ga0.52As/InP superlattice, an In0.48Ga0.52As strained epilayer on InP, and bulk InP. The sharpness of the interfaces between the alloy and InP layers in the superlattice sample is confirmed through the observation of folded acoustic modes up to folding index m = 6. Mixed interface modes were correspondingly not observed in the superlattice optic mode Raman spectra. The GaAs-like longitudinal optic (LO) and transverse optic and InP LO modes in the superlattice are found to decrease in frequency with respect to the corresponding strained-epilayer and bulk-InP modes. These frequency shifts arise from phonon confinement effects in the superlattice. © 2000 American Institute of Physics.
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68.35.Ja Surface and interface dynamics and vibrations
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
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