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1 Nov 1998

Volume 84, Issue 9, pp. 4649-5372

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Some effects of conduction band nonparabolicity on electron reflection spectrum of multiquantum barriers

Michinori Irikawa, Takuya Ishikawa, Yoshitaka Sasaki, Katsumi Iwasawa, Ikuo Suemune, and Kenichi Iga

J. Appl. Phys. 84, 4667 (1998); http://dx.doi.org/10.1063/1.368708 (6 pages) | Cited 3 times

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The effect of nonparabolicity of conduction band on the electron reflection spectrum of multiquantum barriers (MQB) has been examined. Drastic reduction in the effective barrier height is expected by adopting the nonparabolic model on the MQB which had been designed using the parabolic model for 1.5 μm semiconductor lasers (LDs). The predicted enhancement in barrier height by the MQB is over 600 meV under parabolic model. However, it decreases to 40 meV under nonparabolic model with the same structure. On the other hand, the experimental enhancement in barrier height by the MQB is estimated to be around 30 meV on 1.5 μm LDs, close to the value calculated by nonparabolic model. Those results suggest that a much higher effective barrier height can be realized by optimizing the MQB design taking the nonparabolicity into account. The conduction band nonparabolicity was incorporated by the k⋅p perturbation method. © 1998 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.23.-b Electronic transport in mesoscopic systems
42.55.Px Semiconductor lasers; laser diodes

Comparison between the Monte Carlo method and the drift-diffusion approximation in quantum-well laser simulation

A. D. Güçlü, R. Maciejko, A. Champagne, M. Abou-Khalil, and T. Makino

J. Appl. Phys. 84, 4673 (1998); http://dx.doi.org/10.1063/1.368709 (4 pages) | Cited 1 time

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The most widespread approaches to semiconductor device simulation are the drift-diffusion equations, momentum/energy balance equations, and the Monte Carlo method. In this article, the first comparison between results of a Monte Carlo simulation of a multiple-quantum-well structure and those obtained using a classical drift-diffusion simulator is presented. The outcome of the two methods is found to be similar. Still, the Monte Carlo approach offers much more insight into several issues such as the effects of the light holes and the carrier–carrier interactions. The limits and advantages of both methods are discussed. © 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.)
85.30.De Semiconductor-device characterization, design, and modeling
02.70.Rr General statistical methods
42.25.Fx Diffraction and scattering
05.60.-k Transport processes

Giant sonic stop bands in two-dimensional periodic system of fluids

M. S. Kushwaha and B. Djafari-Rouhani

J. Appl. Phys. 84, 4677 (1998); http://dx.doi.org/10.1063/1.368710 (7 pages) | Cited 37 times

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Periodic binary systems can give rise to genuine acoustic stop bands within which sound and vibrations remain forbidden. We compute extensive band structures for two-dimensional (2D) periodic arrays of air cylinders in water. Complete, multiple, huge stop bands are found for both square and hexagonal lattices. The lowest stop bands are largest for a range of filling fraction 10% ⩽ f ⩽ 55%, with a gap/midgap ratio of 1.8. The most interesting finding of the present investigation is that the low-frequency, flat passbands for a perfectly periodic system correspond to the discrete modes of a single airy cylinder. This is attributed to the low filling fraction and huge density contrast in air and water. We stress that such a simple inhomogeneous system as made up of air and water exhibits the largest stop bands ever reported for 2D or 3D elastic as well as dielectric composites. © 1998 American Institute of Physics.
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62.60.+v Acoustical properties of liquids

Laser-induced evolution of hypocycloidal formation of vortex filaments from nonlinear Rayleigh–Taylor instability in a thin layer of molten metal

S. Lugomer and A. Maksimović

J. Appl. Phys. 84, 4684 (1998); http://dx.doi.org/10.1063/1.368711 (9 pages) | Cited 1 time

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A tiny vortex filament, the self-organization of which follows the contour of the nonlinear Rayleigh–Taylor (RT) instability was generated by the Gaussian laser pulse on a ns time scale. Vortex filament self-organization on the nonplanar target surface follows the asymmetric RT evolution consisting of the compressed half of the hypocycloide whose cusps have evolved into spikes, and of the other half whose cusps have evolved into loops. Since the loops cannot be formed, the filaments break into short sets of parallel rolls, oriented in radial direction. The asymmetric contour of the filament self-organization was reproduced by the two-dimensional multimode model that gives the analytical solution, based on the model of Ott. The asymmetry in the vortex filament self-organization is generated by the random wave number mode values, and by the specific phase relations between the modes. © 1998 American Institute of Physics.
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47.20.Ky Nonlinearity, bifurcation, and symmetry breaking
68.15.+e Liquid thin films
47.32.C- Vortex dynamics
79.20.Ds Laser-beam impact phenomena

Statistical–mechanical calculations of thermal properties of diatomic gases

Francisco J. Gordillo-Vázquez and Joseph A. Kunc

J. Appl. Phys. 84, 4693 (1998); http://dx.doi.org/10.1063/1.368712 (11 pages) | Cited 1 time

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The impact of rotational–vibrational dynamics of molecules on the molecular partition functions, law of mass action and thermodynamic functions of partially dissociated diatomic gases is discussed. A group of 11 gases, expected to have their partition functions the most sensitive to the molecular rotational–vibrational properties, is selected for rigorous and detailed studies, and the partition functions, dissociation degrees and free energies of the gases are calculated (using various models of molecular rotational–vibrational dynamics) and compared in a broad range of temperature and particle density. © 1998 American Institute of Physics.
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51.30.+i Thermodynamic properties, equations of state
05.20.-y Classical statistical mechanics
34.50.Ez Rotational and vibrational energy transfer
05.70.Ce Thermodynamic functions and equations of state

Modeling and three-dimensional simulation of the neutral dynamics in an air discharge confined in a microcavity. I. Formation and free expansion of the pressure waves

O. Eichwald, M. Yousfi, P. Bayle, and M. Jugroot

J. Appl. Phys. 84, 4704 (1998); http://dx.doi.org/10.1063/1.368713 (12 pages) | Cited 9 times

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A three-dimensional numerical analysis of the neutral dynamics is performed in the case of a short-gap (0.5 mm) spark discharge in air confined in microcavities at atmospheric pressure (760 Torr) and ambient temperature (293 K). This work is undertaken in the framework of silicon microsystems bearing a micropump actuated by pressure waves which result from a discharge. The short-gap discharge characteristics are taken from experimental results namely 470 ns for the duration and 13.5 W for the maximum injected power. The neutral gas evolution is described by the classical transport equations and solved by a powerful numerical monotonic upstream-centered scheme for conversion laws. The gas–solid interaction occurring in thermal and hydrodynamic boundary layers is taken into account assuming that the microcavity temperature remains invariant (293 K). This article (part I) is devoted to the first evolution phase of the neutral dynamics whose the duration corresponds to the discharge time. Our results clearly show that the first phase can again be split into a neutral inertia phase (during which the thermal energy transferred is stored in the ionized channel) followed by a free expansion one where this thermal energy is dissipated in the microcavity volume. The latter phase is analyzed before the neutral heterogeneities reach the microcavity’s walls. We also discuss the specific gas behaviors of the gas nearby the electrode surfaces, following heat exchanges and viscous stress. © 1998 American Institute of Physics.
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity
47.45.-n Rarefied gas dynamics
47.11.-j Computational methods in fluid dynamics
47.27.T- Turbulent transport processes

Modeling and three dimensional simulation of the neutral dynamics in an air discharge confined in a microcavity. II. Analysis of the wall and geometry effects

O. Eichwald, P. Bayle, Y. Yousfi, and M. Jugroot

J. Appl. Phys. 84, 4716 (1998); http://dx.doi.org/10.1063/1.368714 (11 pages) | Cited 5 times

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This article is devoted to the analysis of the confinement effects of the neutral dynamics generated by a short-gap (0.5 mm) discharge inside three different microcavity geometries (cylinder, cube, and bricklike) filled with air at atmospheric pressure (760 Torr) and ambient temperature (293 K). The discharge is modelled by two mathematical functions representing the Joule heating and the momentum transfer between charged and neutral particles. Their spatio-temporal evolution are taken from experimental results with 470 ns for the duration and 13.5 W for the maximum injected power. The neutral gas evolution is described by the classical transport equations and solved by a powerful numerical monotonic upstream-centered scheme for conversion laws. Because of the microcavity dimensions considered, particular care has been used in the analysis of the thermal and hydrodynamics boundary layers which condition the gas–solid interaction in terms of viscous slip effects and thermal exchanges. The results presented show the microcavity geometry effects on the distribution of the initial cylindrical pressure wave as soon as it reaches the lateral walls. They show the specificity of the cube and bricklike microcavities due to the delayed reflections on the corners leading to a more heterogeneous gas behavior than in the case of the cylindrical microcavity. We also discuss the specific gas behaviors near the wall resulting from heat exchange and viscous stress. © 1998 American Institute of Physics.
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity
47.11.-j Computational methods in fluid dynamics
47.45.-n Rarefied gas dynamics
47.27.T- Turbulent transport processes
47.40.-x Compressible flows; shock waves

Reactions in the afterglow of time modulated inductive discharges of Xe and I2 mixtures

Paul N. Barnes and Mark J. Kushner

J. Appl. Phys. 84, 4727 (1998); http://dx.doi.org/10.1063/1.368799 (4 pages) | Cited 1 time

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An investigation was conducted using absorption and emission spectroscopy of the afterglow from rf inductive discharges in Xe/I2 mixtures. RF power at 11.5 MHz was supplied to coils surrounding a cylindrical discharge cell. Total pressures were between 0.8 and 5.3 Torr. Measurements were made as a function of radius and time following the termination of the discharge. Results presented here indicate that in the afterglow the XeI∗ excimer is formed by highly excited I2 and ground state Xe. Evidence is also presented that ion–ion neutralization is a major precursor reaction for the formation of other excited species in the afterglow. © 1998 American Institute of Physics.
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52.80.Pi High-frequency and RF discharges
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
52.80.Hc Glow; corona
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Information from probe characteristics in negative ion containing plasma

M. Vucelić and S. Mijović

J. Appl. Phys. 84, 4731 (1998); http://dx.doi.org/10.1063/1.368715 (5 pages) | Cited 8 times

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The effect of negative ions on the probe characteristic is studied theoretically. The reliability of results obtained from probe characteristics is analyzed. The methods of determining the energy distribution functions of charged particles is analyzed as an inverse ill-posed problem. A Tikhonov’s regularization procedure for detection of negative ions from a probe characteristic is described. This method parallels the Dryvestein method with the key difference stemming from the fact that experimental determination of the second derivative of the probe characteristic is avoided. For a small ratio of negative ion to electron densities and quite plasma, the energy distribution, temperature and density for the electrons and negative ions can be estimated only from the probe characteristic and the errors in the experimental data. The model functions, simulating experimental energy distribution for the electrons and negative ions, are introduced to test applicability limitations of the method. In addition, the comparative advantages of the method are presented as well. © 1998 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
52.25.-b Plasma properties
52.27.Jt Nonneutral plasmas

Surface interactions of CF2 radicals during deposition of amorphous fluorocarbon films from CHF3 plasmas

Nathan E. Capps, Neil M. Mackie, and Ellen R. Fisher

J. Appl. Phys. 84, 4736 (1998); http://dx.doi.org/10.1063/1.368716 (8 pages) | Cited 42 times

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Surface reactivities for CF2 radicals formed in a CHF3 plasma molecular beam are measured during film deposition on a variety of substrates. The imaging of radicals interacting with surfaces (IRIS) technique was used to collect spatially resolved laser-induced fluorescence (LIF) images of CF2 radicals interacting with SiO2, Si3N4, Si, 304 stainless steel, and system 8 photoresist substrates. Films deposited during IRIS experiments were characterized using x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy and were found to be nearly identical in composition on all substrates. Simulation of LIF cross-sectional data shows high scattering coefficients for CF2 radicals on all substrates. These extremely large scattering coefficients (>1.0) indicate that CF2 molecules are generated through plasma interactions with the substrate. Possible CF2 surface generation mechanisms are discussed, with consideration of CF and ion bombardment contributions to the generation of CF2. © 1998 American Institute of Physics.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
33.50.Dq Fluorescence and phosphorescence spectra
33.60.+q Photoelectron spectra
79.60.Fr Polymers; organic compounds
68.55.-a Thin film structure and morphology

Electromagnetic surface wave modes in nonrelativistic electron–positron plasmas

Sang-Hoon Cho and Hee J. Lee

J. Appl. Phys. 84, 4744 (1998); http://dx.doi.org/10.1063/1.368717 (5 pages) | Cited 9 times

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Electromagnetic surface waves propagating on the plane interface (x = 0) between the electron–positron plasma and vacuum are investigated by the specular reflection procedure. The transverse electromagnetic modes are studied in terms of dispersion relation both in the presence and absence of an applied magnetic field. The analytic modes for some limiting cases are derived and discussed with the aid of some numerical analysis. In the presence of an applied magnetic field (B0 = B0ŷ) directed perpendicular both to the interface normal and the wave vector, the cold electromagnetic surface wave dispersion relation shows that possible modes appear only when the frequency (ω) and the wave vector (k) satisfy the condition Ω2<ω2<Ω2+ωp2 and c2k2>Ω2 (Ω is cyclotron frequency). © 1998 American Institute of Physics.
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52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
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