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29 Apr 2002

Volume 80, Issue 17, pp. 3033-3231

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Visualization of low-frequency liquid surface acoustic waves by means of optical diffraction

Runcai Miao, Zongli Yang, Jingtao Zhu, and Changyu Shen

Appl. Phys. Lett. 80, 3033 (2002); http://dx.doi.org/10.1063/1.1475769 (3 pages) | Cited 12 times

Online Publication Date: 22 April 2002

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A technique for low-frequency liquid surface acoustic wave (LFLSAW) visualization is developed based on the light diffraction. The technique is capable of real-time characterization of wave amplitude, and it produces highly visible stationary diffraction pattern for a low-frequency wave (a few hundreds Hz). The disappearance of the zero-order diffraction fringe, which corresponding to the 100% diffraction efficiency, was experimentally observed for using this technique. The correlation of the diffraction pattern to the LFLSAW amplitude is also experimentally established. © 2002 American Institute of Physics.
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43.35.Pt Surface waves in solids and liquids

Broadband optical amplifier based on a conjugated polymer

J. R. Lawrence, G. A. Turnbull, and I. D. W. Samuel

Appl. Phys. Lett. 80, 3036 (2002); http://dx.doi.org/10.1063/1.1472479 (3 pages) | Cited 26 times

Online Publication Date: 22 April 2002

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We demonstrate a compact, broadband optical amplifier using the conjugated polymer poly[2-methoxy-5-(2′,6′-dimethyloctyloxy)-paraphenylenevinylene] (OC1C10–PPV) in dilute solution. Gains of 30–40 dB in a wavelength range of 575–640 nm, corresponding to a 50 THz bandwidth, are observed due to the broad luminescence spectrum and large cross section for stimulated emission of the polymer. The variation in gain as a function of solution concentration and probe intensity is examined. For a 1 cm path length we observe a small signal gain of 44±1 dB, and deduce a stimulated emission cross-section for OC1C10–PPV of (5.3±0.6)×10−17 cm2. © 2002 American Institute of Physics.
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42.70.Hj Laser materials
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.70.Jk Polymers and organics
78.45.+h Stimulated emission
78.55.Bq Liquids

Wavelength stabilization of semiconductor lasers with a tunable photodetector

Lorenzo Colace, Gianlorenzo Masini, and Gaetano Assanto

Appl. Phys. Lett. 80, 3039 (2002); http://dx.doi.org/10.1063/1.1473877 (3 pages) | Cited 1 time

Online Publication Date: 22 April 2002

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We introduce an approach to stabilizing the wavelength of a semiconductor laser employing a voltage-tunable photodetector. The latter provides a bipolar error signal driving a feedback loop for the laser retuning. We demonstrate wavelength stabilization within ±25 pm in the 1.55 μm window. Performances, system compactness, and integrability make the approach quite appealing for use in dense wavelength division multiplexing networks. © 2002 American Institute of Physics.
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42.60.Fc Modulation, tuning, and mode locking
42.55.Px Semiconductor lasers; laser diodes
85.60.Gz Photodetectors (including infrared and CCD detectors)

Polarization effects of a europium complex in stretched polyethylene

V. I. Srdanov, M. R. Robinson, M. H. Bartl, X. Bu, and G. C. Bazan

Appl. Phys. Lett. 80, 3042 (2002); http://dx.doi.org/10.1063/1.1470700 (3 pages) | Cited 8 times

Online Publication Date: 22 April 2002

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Polarization effects in photoluminescence spectra of Eu3+ ions in tris(dinaphthoylmethane) (monophenanthroline)europium(III) complex [abbreviated hereafter as Eu(dnm)3phen] dispersed in stretched polyethylene (PE) reveal quasi-uniaxial alignment of the molecular complex, not present in the unstretched PE. The ligand field structure of Eu3+ 5D0–7F2 transition in the Eu(dnm)3phen single crystal differs from that of a single molecule in stretched PE, indicating rearrangement of the organic ligands upon stretching. © 2002 American Institute of Physics.
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78.55.Kz Solid organic materials
71.70.Ch Crystal and ligand fields

Coupled-stripe quantum-well-assisted AlGaAs–GaAs–InGaAs–InAs quantum-dot laser

G. Walter, T. Chung, and N. Holonyak

Appl. Phys. Lett. 80, 3045 (2002); http://dx.doi.org/10.1063/1.1473686 (3 pages) | Cited 8 times

Online Publication Date: 22 April 2002

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Data are presented on the coupled-stripe laser operation (continuous wave, 300 K) of a single InAs quantum-dot (QD) layer coupled via a thin (5 Å) GaAs barrier to an auxiliary strained InGaAs quantum well (QW) grown (confined) in an AlGaAs–GaAs heterostructure. Because of strain-induced (QW strain) improvement of the QD growth and QD alignment along diagonal (reflecting) ridges, the InGaAs-QW+InAs-QD crystals exhibit high gain along and across laser stripes, which is advantageous for coupled-stripe laser operation. A twin-stripe single-QD-layer QW+QD laser (4 μm stripes on 6 μm centers) of usual cleaved length, < 500 μm, is capable of continuous 300 K operation, with only probe heat-sink clamping and testing, at >50 mW. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.07.Ta Quantum dots
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Intrinsic reduction of the depolarization loss in solid-state lasers by use of a (110)-cut Y3Al5O12 crystal

Ichiro Shoji and Takunori Taira

Appl. Phys. Lett. 80, 3048 (2002); http://dx.doi.org/10.1063/1.1475365 (3 pages) | Cited 16 times

Online Publication Date: 22 April 2002

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The depolarization caused by thermally induced birefringence in Y3Al5O12 lasers is intrinsically reduced without any compensation by use of rods cut in other directions than (111). Using a (110)-cut crystal, one can expect the depolarization to become less than 1/10 of that caused in a conventional (111)-cut crystal. © 2002 American Institute of Physics.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.70.Hj Laser materials
78.20.Fm Birefringence
42.25.Lc Birefringence

Unidirectional bistability in semiconductor waveguide ring lasers

M. Sorel, P. J. R. Laybourn, G. Giuliani, and S. Donati

Appl. Phys. Lett. 80, 3051 (2002); http://dx.doi.org/10.1063/1.1474619 (3 pages) | Cited 54 times

Online Publication Date: 22 April 2002

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Large-diameter ridge-guided semiconductor lasers weakly coupled to a straight output waveguide show unidirectional operation and directional bistability at currents up to about twice the threshold. The direction of lasing in the ring may be controlled by biasing contacts at either end of the coupled guide. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.55.Wd Fiber lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.65.Pc Optical bistability, multistability, and switching, including local field effects

Effects of insertion of strain-mediating layers on luminescence properties of 1.3-μm GaInNAs/GaNAs/GaAs quantum-well structures

E.-M. Pavelescu, C. S. Peng, T. Jouhti, J. Konttinen, W. Li, M. Pessa, M. Dumitrescu, and S. Spânulescu

Appl. Phys. Lett. 80, 3054 (2002); http://dx.doi.org/10.1063/1.1470223 (3 pages) | Cited 42 times

Online Publication Date: 22 April 2002

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We present a 1.3-μm GaInNAs/GaAs quantum-well heterostructure, which consists of a strain-mediating GaInNAs layer grown between a compressive-strained quantum well and a tensile-strained GaNAs layer. Compared to a similar sample with no strain-mediating layer, this heterostructure exhibits improved material properties and remarkable redshift of emission with enhanced light intensity. The observations are based on photoluminescence spectra and x-ray diffraction data measured for the active region of the samples. © 2002 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.67.De Quantum wells

Rate equations of vertical-cavity semiconductor optical amplifiers

P. Royo, R. Koda, and L. A. Coldren

Appl. Phys. Lett. 80, 3057 (2002); http://dx.doi.org/10.1063/1.1476056 (3 pages) | Cited 1 time

Online Publication Date: 22 April 2002

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We rigorously establish the rate equations for vertical-cavity semiconductor optical amplifiers, starting from a general energy rate equation. Our results show that the conventional rate equation used so far in the literature is incorrect because of an inappropriate calculation of the mirror losses. Our calculations include the effect of amplified spontaneous emission and can be used to describe the properties of resonant-cavity-enhanced photodetectors. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
85.30.De Semiconductor-device characterization, design, and modeling
42.79.Bh Lenses, prisms and mirrors
42.50.Nn Quantum optical phenomena in absorbing, amplifying, dispersive and conducting media; cooperative phenomena in quantum optical systems
85.60.Gz Photodetectors (including infrared and CCD detectors)

Quantum cascade lasers with double metal-semiconductor waveguide resonators

Karl Unterrainer, Raffaele Colombelli, Claire Gmachl, Federico Capasso, Harold Y. Hwang, A. Michael Sergent, Deborah L. Sivco, and Alfred Y. Cho

Appl. Phys. Lett. 80, 3060 (2002); http://dx.doi.org/10.1063/1.1469657 (3 pages) | Cited 38 times

Online Publication Date: 22 April 2002

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Quantum cascade (QC) lasers with double metal-semiconductor waveguide resonators are reported for operating wavelengths of 19, 21, and 24 μm. The waveguides are based on surface-plasmon modes confined at the metal–semiconductor interfaces on both sides of the active region/injector stack and are not restricted by a cutoff wavelength for the TM polarized intersubband radiation. The double metal-semiconductor resonator devices are fabricated using an epilayer transfer process. Optical confinement factors close to 1 are obtained, with low waveguide losses. The performance of the devices is compared with that of QC lasers based on single-sided surface-plasmon waveguides. The concept of QC laser with double metal-semiconductor waveguide is applicable to a much wider wavelength range. © 2002 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.)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.40.Ns Metal-nonmetal contacts
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.79.Gn Optical waveguides and couplers

Symmetry-induced perfect transmission of light waves in quasiperiodic dielectric multilayers

R. W. Peng, X. Q. Huang, F. Qiu, Mu Wang, A. Hu, S. S. Jiang, and M. Mazzer

Appl. Phys. Lett. 80, 3063 (2002); http://dx.doi.org/10.1063/1.1468895 (3 pages) | Cited 49 times

Online Publication Date: 22 April 2002

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Resonant transmission of light has been observed in symmetric Fibonacci TiO2/SiO2 multilayers, which is characterized by many perfect transmission peaks. The perfect transmission dramatically decreases when the mirror symmetry in the multilayer structure is deliberately disrupted. Actually, the feature of perfect transmission peaks can be considered as general evidence for dielectric multilayers with symmetric internal structure. It opens a unique way to control light propagation. © 2002 American Institute of Physics.
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78.66.Nk Insulators
42.79.Wc Optical coatings
68.65.Ac Multilayers
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
42.70.Qs Photonic bandgap materials
42.50.-p Quantum optics
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Principle and application of a thermal probe to reactive plasmas

E. Stamate, H. Sugai, and K. Ohe

Appl. Phys. Lett. 80, 3066 (2002); http://dx.doi.org/10.1063/1.1473688 (3 pages) | Cited 13 times

Online Publication Date: 22 April 2002

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A thermal probe for plasma diagnostics is introduced. The method is based upon measuring the equilibrium temperature of a conducting sphere as a function of its applied bias. The resulting temperature–voltage characteristic is processed using a theoretical model that accounts for charge and thermodynamic balance. The thermal probe is capable of detecting negative ions and shows sensitivity to certain chemical reactions. Measurements performed in Ar, Ar/SF6, and O2 show good agreement among the plasma parameters using thermal and Langmuir probes. © 2002 American Institute of Physics.
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52.70.-m Plasma diagnostic techniques and instrumentation
52.70.Ds Electric and magnetic measurements
52.25.-b Plasma properties
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Dislocation jumping over the sound barrier in tungsten

Qikai Li and San-Qiang Shi

Appl. Phys. Lett. 80, 3069 (2002); http://dx.doi.org/10.1063/1.1473865 (3 pages) | Cited 11 times

Online Publication Date: 22 April 2002

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It is commonly believed that dislocations cannot surmount the sound barrier at the shear wave velocity. This letter presents results of molecular dynamics simulation showing the contrary, namely that a stationary dislocation can be accelerated above the sound barrier provided that the theoretical shear strength is reached at the dislocation core and the total energy of a subsonic perfect dislocation is sufficiently high to cause its dissociation into transonic partial dislocations. © 2002 American Institute of Physics.
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61.72.Lk Linear defects: dislocations, disclinations
61.72.Bb Theories and models of crystal defects
02.70.Ns Molecular dynamics and particle methods

Delayed phase explosion during high-power nanosecond laser ablation of silicon

Quanming Lu, Samuel S. Mao, Xianglei Mao, and Richard E. Russo

Appl. Phys. Lett. 80, 3072 (2002); http://dx.doi.org/10.1063/1.1473862 (3 pages) | Cited 53 times

Online Publication Date: 22 April 2002

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An important parameter for high-irradiance laser ablation is the ablation crater depth, resulting from the interaction of individual laser pulses on a targeted surface. The crater depth for laser ablation of single-crystal silicon shows a dramatic increase at a laser intensity threshold of approximately 2×1010 W/cm2, above which, large (micron-sized) particulates were observed to eject from the target. We present an analysis of this threshold phenomenon and demonstrate that thermal diffusion and subsequent explosive boiling after the completion of the laser pulse is a possible mechanism for the observed dramatic increase of the ablation depth. Calculations based on this delayed phase explosion model provide a satisfactory estimate of the measurements. In addition, we find that the shielding of an expanding mass plasma during laser irradiation has a profound effect on this threshold phenomenon. © 2002 American Institute of Physics.
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79.20.Ds Laser-beam impact phenomena
68.35.Rh Phase transitions and critical phenomena
52.38.Mf Laser ablation
68.35.Fx Diffusion; interface formation

Evidence of swelling of SiO2 upon thermal annealing

S. Banerjee, S. Chakraborty, and P. T. Lai

Appl. Phys. Lett. 80, 3075 (2002); http://dx.doi.org/10.1063/1.1473863 (3 pages) | Cited 5 times

Online Publication Date: 22 April 2002

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Ultrathin SiO2 film was thermally grown on Si(001) substrate by dry oxidation and wet oxidation processes. The films were then subjected to thermal annealing (TA) at 1000 °C for 30 min. The structural characterization of the as-grown and the TA samples was carried out using the grazing incidence x-ray reflectivity technique. The analysis of the x-ray reflectivity data was carried out by using a model independent formalism based on the distorted wave Born approximation for obtaining the electron density profile (EDP) of the film as a function of depth. The EDP of both films show a decrease in the electron density as well as an increase in their thickness when the films are subjected to TA. It has also been observed that the total number of electrons is conserved in the oxide film after TA. Our analysis of the x-ray reflectivity data indicates that the SiO2 film swells and its interface with the substrate modifies upon TA. © 2002 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
68.55.-a Thin film structure and morphology
81.40.Gh Other heat and thermomechanical treatments
61.72.Cc Kinetics of defect formation and annealing
81.65.Mq Oxidation

Ordering of Ge quantum dots with buried Si dislocation networks

F. Leroy, J. Eymery, P. Gentile, and F. Fournel

Appl. Phys. Lett. 80, 3078 (2002); http://dx.doi.org/10.1063/1.1474601 (3 pages) | Cited 39 times

Online Publication Date: 22 April 2002

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Buried dislocation networks obtained by Si(001) wafer bonding pattern the free surface of the sample, giving rise to long-range undulations and short-range embossing, respectively, for flexion and rotation misalignement. Comparison with continuum-elasticity calculations reveals that this patterning is enhanced by strain-driven overetching. These surfaces are a template for growth, and we show that Ge quantum dots can be ordered with a fourfold symmetry by proceeding a postgrowth annealing. © 2002 American Institute of Physics.
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68.65.Hb Quantum dots (patterned in quantum wells)
81.05.Cy Elemental semiconductors
81.07.Ta Quantum dots
61.72.Lk Linear defects: dislocations, disclinations
81.40.Gh Other heat and thermomechanical treatments

Percolation behavior in the Raman spectra of ZnBeTe alloy

O. Pagès, T. Tite, D. Bormann, O. Maksimov, and M. C. Tamargo

Appl. Phys. Lett. 80, 3081 (2002); http://dx.doi.org/10.1063/1.1467711 (3 pages) | Cited 16 times

Online Publication Date: 22 April 2002

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Zone-center longitudinal (LO) and transverse (TO) optical phonons of Zn1−xBexTe epilayers are identified by Raman spectroscopy. On top of the expected BeTe- and ZnTe-like modes, which obey the modified-random-element-isodisplacement model, we observe an extra BeTe-like (TO, LO) doublet at intermediate x values. It has the same atypical characteristics as its BeSe-like counterpart in ZnBeSe alloy. Its activation validates our percolative picture for multimode description in Be–chalcogenide alloys that open the attractive class of mixed crystals with a sharp contrast in the bond stiffness. Also, the local modes of Be in ZnTe and of Zn in BeTe are identified at 411 cm−1 and 195 cm−1, respectively. © 2002 American Institute of Physics.
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78.30.Fs III-V and II-VI semiconductors
78.66.Hf II-VI semiconductors
63.20.Pw Localized modes
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

Selective study of polymer/dielectric interfaces with vibrationally resonant sum frequency generation via thin-film interference

Philip T. Wilson, Kimberly A. Briggman, William E. Wallace, John C. Stephenson, and Lee J. Richter

Appl. Phys. Lett. 80, 3084 (2002); http://dx.doi.org/10.1063/1.1475358 (3 pages) | Cited 14 times

Online Publication Date: 22 April 2002

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A technique for selective characterization of the structure of free and buried thin-film interfaces by vibrationally resonant sum frequency generation spectroscopy is described. Manipulation of Fresnel coefficients by choice of film thickness on a reflecting substrate allows simultaneous optimization of the signal from the desired interface and minimization of the signal from other interfacial sources. This technique is demonstrated for the free polystyrene (PS)/air and the buried PS/spin-on glass interfaces. Our spectra show that the pendant phenyl group orientation is similar at the buried and free interfaces, with the phenyls pointing away from the bulk PS at each interface.
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68.35.Ct Interface structure and roughness
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.66.Qn Polymers; organic compounds
77.55.-g Dielectric thin films
77.84.Jd Polymers; organic compounds

Unusual transition phenomenon in Zr-based bulk metallic glass upon heating at high pressure

Liling Sun, Takumi Kikegawa, Qi Wu, Zhanji Zhai, and Wenkui Wang

Appl. Phys. Lett. 80, 3087 (2002); http://dx.doi.org/10.1063/1.1473869 (3 pages) | Cited 5 times

Online Publication Date: 22 April 2002

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Structural changes of the bulk metallic glass (BMG) Zr41.2Ti13.8Cu12.5Ni10Be22.5 were investigated at high pressure and high temperature with synchrotron radiation x-ray diffraction (SR-XRD). In situ SR-XRD measurements confirm that heating the BMG at a pressure of 10 GPa leads to an unusual sequence of transitions. The initial amorphous solid transforms into a crystalline phase at 582 K, and then the crystalline phase transforms back to an amorphous phase at 698 K. This crystalline-to-amorphous phase transition in a BMG is driven by increasing temperature at higher density produced by high pressure. © 2002 American Institute of Physics.
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64.70.K- Solid-solid transitions
61.43.Fs Glasses
62.50.-p High-pressure effects in solids and liquids

Manufacture of specific structure of aluminum-doped zinc oxide films by patterning the substrate surface

X. Jiang, C. L. Jia, and B. Szyszka

Appl. Phys. Lett. 80, 3090 (2002); http://dx.doi.org/10.1063/1.1473683 (3 pages) | Cited 31 times

Online Publication Date: 22 April 2002

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(0001)-oriented aluminum-doped zinc oxide films were prepared using a magnetron sputtering technique. High-resolution transmission-electron-microscopic images show that the oriented grains nucleate directly on the substrate surface and grow with equal lateral dimensions through the film thickness. A surface-energy-driven self-texture mechanism was proposed on the basis of process modes. A method for manufacturing specific film structure by patterning the substrate surface is tested and discussed. © 2002 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.05.Dz II-VI semiconductors
81.15.Cd Deposition by sputtering
85.40.Ry Impurity doping, diffusion and ion implantation technology
61.72.up Other materials
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.35.Md Surface thermodynamics, surface energies
68.35.Ct Interface structure and roughness

Direct observation of Ga-rich microdomains in crack-free AlGaN grown on patterned GaN/sapphire substrates

T. Riemann, J. Christen, A. Kaschner, A. Laades, A. Hoffmann, C. Thomsen, M. Iwaya, S. Kamiyama, H. Amano, and I. Akasaki

Appl. Phys. Lett. 80, 3093 (2002); http://dx.doi.org/10.1063/1.1473703 (3 pages) | Cited 10 times

Online Publication Date: 22 April 2002

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The strong three-dimensional modulation of the optical and structural properties due to the self-organized formation of Ga-rich AlGaN microdomains is directly imaged by spectrally and spatially resolved cathodoluminescence microscopy. The 5-μm-thick, crack-free AlGaN was grown on patterned GaN/sapphire templates periodically structured into trenches and terraces. During initial AlGaN overgrowth, the modulation of the local AlGaN stochiometry results in marble-like striations of Ga accumulation clearly reflecting the pattern periodicity. In contrast, after subsequent overgrowth, a homogeneous emission wavelength, i.e., a homogeneous aluminum content, is found near the sample surface. However, the strong rise of quantum efficiency directly above the trenches indicates a drastic improvement of material quality. © 2002 American Institute of Physics.
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68.55.-a Thin film structure and morphology
78.66.Fd III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
61.66.Bi Elemental solids
61.66.Dk Alloys

Thermophysical properties and glass forming ability in the alloy series (Ti100−xZrx)45(Ni14.5Cu85.5)55

C. C. Hays and S. C. Glade

Appl. Phys. Lett. 80, 3096 (2002); http://dx.doi.org/10.1063/1.1475368 (3 pages) | Cited 3 times

Online Publication Date: 22 April 2002

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Measurements of the structural and thermophysical properties of bulk metallic glass forming alloys in the series (Ti100−xZrx)45(Ni14.5Cu85.5)55 (at. %) are presented for 25 ⩽ x ⩽ 75. The bulk glass forming ability was found to terminate abruptly for x>50 due to the nucleation of NiTiZr and Zr2Cu symmetry phases with increasing x. Calorimetric measurements reveal that crystallization is facilitated by a decomposition process in the under-cooled liquid. © 2002 American Institute of Physics.
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64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
61.43.Fs Glasses

Effects of tensile, compressive, and zero strain on localized states in AlInGaN/InGaN quantum-well structures

M. E. Aumer, S. F. LeBoeuf, B. F. Moody, S. M. Bedair, K. Nam, J. Y. Lin, and H. X. Jiang

Appl. Phys. Lett. 80, 3099 (2002); http://dx.doi.org/10.1063/1.1469219 (3 pages) | Cited 8 times

Online Publication Date: 22 April 2002

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The recombination dynamics of optical transitions as well as strain effects in AlInGaN/In0.08Ga0.92N quantum wells (QWs) were studied. QW emission energy, photoluminescence decay behavior, photoluminescence emission line shape, and nonradiative recombination behavior were found to be strong functions of strain as well as localization. The degree of carrier localization was inferred by modeling several aspects of optical behavior obtained from variable temperature time-resolved photoluminescence experiments. According to the modeling results, the degree of localization was found to be a minimum for unstrained QWs and increased as either tensile or compressive strain increased, indicating that InGaN QW microstructure is a function of the lattice-mismatch-induced strain experienced during deposition. © 2002 American Institute of Physics.
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78.67.De Quantum wells
73.21.Fg Quantum wells
68.65.Fg Quantum wells
78.55.Cr III-V semiconductors
73.20.Fz Weak or Anderson localization
78.47.-p Spectroscopy of solid state dynamics

Large changes in refractive index by synchrotron-radiation-driven compaction of hydrogenated silicon nitride films

Housei Akazawa

Appl. Phys. Lett. 80, 3102 (2002); http://dx.doi.org/10.1063/1.1475768 (3 pages) | Cited 5 times

Online Publication Date: 22 April 2002

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When high-energy photons (hν>100 eV) irradiate films of hydrogenated silicon nitride (a-SiNx:H) that have been deposited by plasma-enhanced chemical-vapor deposition, the network of atoms in the material is photolytically rearranged. This reaction proceeds rapidly from the instance the radiation is applied and is almost completed within 200 s. This is in striking contrast with the continuing effect of such radiation on SiO2 (defect formation and decomposition). The result was a change (Δn) in the refractive index at 633 nm of as much as 0.04, and this effect was independent of the temperature of irradiation. By using an effective medium mixture of Si3N4, crystalline Si, and voids to model the dielectric function of a-SiNx:H films, the volumes of the voids and of crystalline Si components were found to be reduced by 44% and 49%, respectively, from their initial values. The resulting 9.8% reduction in the thickness (compaction) is the origin of the large Δn. © 2002 American Institute of Physics.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Nk Insulators
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Ms Insulators
61.72.Qq Microscopic defects (voids, inclusions, etc.)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.50.Hp Processes caused by visible and UV light
68.55.-a Thin film structure and morphology

Negative band gap bowing in epitaxial InAs/GaAs alloys and predicted band offsets of the strained binaries and alloys on various substrates

Kwiseon Kim, Gus L. W. Hart, and Alex Zunger

Appl. Phys. Lett. 80, 3105 (2002); http://dx.doi.org/10.1063/1.1470693 (3 pages) | Cited 6 times

Online Publication Date: 22 April 2002

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We use pseudopotential theory to provide (1) the band offsets of strained GaAs and InAs on various substrates and (2) the energies Ev(x) and Ec(x) of the valence and conduction bands of InxGa1−xAs alloy, as a function of composition. Results are presented for both the bulk alloy and for the alloy strained on InP or GaAs. We predict that while Ec(x) bows downward for relaxed bulk alloys, it bows upward for strained epitaxial alloys. The calculated alloy offsets are used to discuss electron and hole localization in this system. © 2002 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)
71.20.Nr Semiconductor compounds
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