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22 Nov 1999

Volume 75, Issue 21, pp. 3243-3419

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1540 nm light emission from Er-doped amorphous GaAsN films

A. R. Zanatta

Appl. Phys. Lett. 75, 3279 (1999); http://dx.doi.org/10.1063/1.125324 (3 pages) | Cited 6 times

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Erbium-doped amorphous gallium–arsenic–nitrogen (a-GaAsN) films have been prepared by cosputtering from a crystalline GaAs wafer partially covered with metallic Er pieces. The films were deposited at room temperature under different partial pressures of Ar and N2. After deposition, the films were characterized by optical transmission in the visible-ultraviolet energy range, photoluminescence (PL) in the infrared region, and Raman scattering spectroscopy. Compositional measurements were also performed indicating an Er content of ∼0.5 at. % and a N concentration that scales with the N2 partial pressure during deposition. According to the experimental results, to higher N contents correspond larger optical band gaps and more intense Er3+-related PL signals. This dependence is analyzed in terms of the compositional, electronic, and structural characteristics of each film. © 1999 American Institute of Physics.
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78.66.Jg Amorphous semiconductors; glasses
78.55.Cr III-V semiconductors
68.55.Nq Composition and phase identification
71.23.Cq Amorphous semiconductors, metallic glasses, glasses
61.43.Dq Amorphous semiconductors, metals, and alloys
78.40.Fy Semiconductors
78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.66.Fd III-V semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.15.Cd Deposition by sputtering

Local structures of Ga atoms in amorphous silicon and hydrogenated amorphous silicon before and after synchrotron x-ray irradiation

Kin Man Yu, W. Walukiewicz, S. Muto, H.-C. Jin, J. R. Abelson, C. Clerc, C. J. Glover, and M. C. Ridgway

Appl. Phys. Lett. 75, 3282 (1999); http://dx.doi.org/10.1063/1.125325 (3 pages) | Cited 2 times

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The influence of intense x-ray irradiation on the local bonding structure of Ga dopants in both hydrogen-free (a-Si) and hydrogenated (a-Si:H) amorphous Si thin films has been studied. Prior to x-ray exposure, extended x-ray absorption fine structure measurements revealed that H reduced the static disorder around the Ga atoms in amorphous Si. Thereafter, x-ray irradiation modified the local structure in the a-Si and a-Si:H samples. The Ga coordination number increased from <3.5 to ∼3.80 atoms for both types of amorphous material as consistent with a greater fraction of electrically active, tetrahedrally coordinated dopant atoms. Also, greater structural disorder was observed around Ga atoms after x-ray irradiation suggesting that tetrahedrally coordinated Ga atoms were less well ordered than in threefold-coordinated sites. © 1999 American Institute of Physics.
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61.43.Dq Amorphous semiconductors, metals, and alloys
61.80.Cb X-ray effects
61.82.Fk Semiconductors
78.70.Dm X-ray absorption spectra
68.55.-a Thin film structure and morphology

Reactive-ion-etched gallium nitride: Metastable defects and yellow luminescence

S. A. Brown, R. J. Reeves, C. S. Haase, R. Cheung, C. Kirchner, and M. Kamp

Appl. Phys. Lett. 75, 3285 (1999); http://dx.doi.org/10.1063/1.125326 (3 pages) | Cited 18 times

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Gallium nitride has been reactive-ion etched with SF6 and argon plasmas. The Ar-etched samples show a striking transition from a dominant blue luminescence band to a dominant yellow luminescence band after less than 5 min of low power illumination. The observation of metastable defects which are associated with both the yellow and blue bands has important consequences for our understanding of defect-related luminescence in gallium nitride. © 1999 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
71.55.Eq III-V semiconductors
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.05.Ea III-V semiconductors

Nucleation of single-crystal CoSi2 with oxide-mediated epitaxy

M. W. Kleinschmit, M. Yeadon, and J. M. Gibson

Appl. Phys. Lett. 75, 3288 (1999); http://dx.doi.org/10.1063/1.125327 (3 pages) | Cited 11 times

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Oxide-mediated epitaxy (OME) has shown promise as a technique for the formation of epitaxial CoSi2 on a variety of Si surfaces. With our in situ ultra-high-vacuum transmission electron microscope we have studied the phase formation sequence of the deposited Co during an anneal on both clean and oxide (OME) -covered Si (001) samples. The striking difference in OME is the absence of polycrystalline CoSi2 nucleation. We discuss the origin and consequences of this observation, and report other details of the phase evolution sequence. © 1999 American Institute of Physics.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.Nq Composition and phase identification
61.72.Cc Kinetics of defect formation and annealing

Polarized optical absorption and photoluminescence measurements in single-crystal thin films of 4′-dimethylamino-N-methyl-4-stilbazolium tosylate

Achintya K. Bhowmik, Jianjun Xu, and Mrinal Thakur

Appl. Phys. Lett. 75, 3291 (1999); http://dx.doi.org/10.1063/1.125328 (3 pages) | Cited 8 times

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Single-crystal thin films of the anhydrous (red) and the hydrated (orange) phases of the organic salt 4′-dimethylamino-N-methyl-4-stilbazolium tosylate were grown by a modification of the shear method. The optical absorption coefficients of the films were measured with light polarized along and normal to the dipole/molecular axis at both resonant and off-resonant wavelengths, and a strong dichroism was observed at the resonant wavelengths. The absorption measurements are important considering potential applications of these films (red phase) in high-speed single-pass thin-film electro-optic modulators [M. Thakur, J. Xu, A. Bhowmik, and L. Zhou, Appl. Phys. Lett. 74, 635 (1999)] and other photonic devices. Highly polarized photoluminescence (PL) has been observed in these films. The PL efficiencies of the red- and orange-phase single-crystal films were measured to be about 12% and 14%, respectively, which are significantly higher than the maximum PL efficiency measured in solution (3%). © 1999 American Institute of Physics.
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78.66.Qn Polymers; organic compounds
78.55.Kz Solid organic materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.20.Fm Birefringence

Influence of residual stress on thermal expansion behavior

X.-L. Wang, C. M. Hoffmann, C. H. Hsueh, G. Sarma, C. R. Hubbard, and J. R. Keiser

Appl. Phys. Lett. 75, 3294 (1999); http://dx.doi.org/10.1063/1.125329 (3 pages) | Cited 6 times

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We demonstrate that the thermal expansion behavior of a material can be substantially modified by the presence of residual stresses. In the case of a composite tube made of two layers of dissimilar steels, in situ neutron diffraction measurements revealed a significant difference in the coefficients of thermal expansion along the radial and tangential directions. It is shown that the observed difference in thermal expansion is due to the change of residual stresses with temperature. © 1999 American Institute of Physics.
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65.40.De Thermal expansion; thermomechanical effects

Experimental and theoretical studies of phonons in hexagonal InN

V. Yu. Davydov, V. V. Emtsev, I. N. Goncharuk, A. N. Smirnov, V. D. Petrikov, V. V. Mamutin, V. A. Vekshin, S. V. Ivanov, M. B. Smirnov, and T. Inushima

Appl. Phys. Lett. 75, 3297 (1999); http://dx.doi.org/10.1063/1.125330 (3 pages) | Cited 120 times

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The first- and second-order Raman scattering and IR reflection have been studied for hexagonal InN layers grown on (0001) and (1math02) sapphire substrates. All six Raman-active optical phonons were observed and assigned: E2(low) at 87 cm−1, E2(high) at 488 cm−1, A1(TO) at 447 cm−1, E1(TO) at 476 cm−1, A1(LO) at 586 cm−1, and E1(LO) at 593 cm−1. The ratio between the InN static dielectric constants for the ordinary and extraordinary directions was found to be ε⊥0/ε∥0 = 0.91. The phonon dispersion curves, phonon density-of-state function, and lattice specific heat were calculated. The Debye temperature at 0 K for hexagonal InN was estimated to be 370 K. © 1999 American Institute of Physics.
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63.20.D- Phonon states and bands, normal modes, and phonon dispersion
78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
65.40.-b Thermal properties of crystalline solids
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems
63.70.+h Statistical mechanics of lattice vibrations and displacive phase transitions

Effect of indium segregation on optical properties of V-groove InGaAs/GaAs strained quantum wires

F. Lelarge, C. Constantin, K. Leifer, A. Condo, V. Iakovlev, E. Martinet, A. Rudra, and E. Kapon

Appl. Phys. Lett. 75, 3300 (1999); http://dx.doi.org/10.1063/1.125331 (3 pages) | Cited 5 times

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Self-ordered, strained InGaAs/GaAs quantum structures are grown on V-grooved GaAs substrates. The lateral patterning of these nonplanar heterostructures allows the growth of defect-free strained structures with thickness exceeding that achieved with planar epitaxy. Indium segregation at the bottom of the groove results in the formation of a vertical InGaAs quantum-well structure with In-enriched composition. We studied in detail the influence of nominal thickness and In content on the photoluminescence peak energy of these quantum wires. Room-temperature emission at 1.16 μm with a relatively narrow linewidth (30–35 meV) is achieved as a demonstration of the potential of this approach for fabricating long-wavelength semiconductor light sources on GaAs substrates. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
64.75.-g Phase equilibria

Characterization of the progressive growth of columns by excimer laser irradiation of silicon

F. Sánchez, J. L. Morenza, and V. Trtik

Appl. Phys. Lett. 75, 3303 (1999); http://dx.doi.org/10.1063/1.125332 (3 pages) | Cited 15 times

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The growth mechanism of columns produced by excimer laser irradiation of a silicon target is investigated. The micrometric columns are formed by a cumulative process with well-defined steps. The first steps lead to silicon hillocks, which evolve to columns through a little-understood mechanism. To investigate it, we irradiated a Si(100) single crystal in air with the necessary pulses of an excimer laser beam to obtain two samples, one with a partially and one with a fully developed column structure. Then we alternated scanning electron microscopy observations with irradiation pulses on the same target area. The progressive evolution of the laser-generated structures is presented. Columns grow at notably high rates, from around 0.5 μm/pulse during the early stages to 0.2 μm/pulse on average for 10–20 μm tall columns. The experimental results lead us to suggest a hydrodynamic growth mechanism. © 1999 American Institute of Physics.
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81.05.Cy Elemental semiconductors
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
81.65.Cf Surface cleaning, etching, patterning

Local and external factors affecting the photodegradation of 4N,N′-dimethylamino-4′nitrostilbene polymer films

Adriana Galvan-Gonzalez, Michael Canva, and George I. Stegeman

Appl. Phys. Lett. 75, 3306 (1999); http://dx.doi.org/10.1063/1.125333 (3 pages) | Cited 8 times

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The photodegradation of the electro-optic chromophore 4N,N′-dimethylamino-4′nitrostilbene was investigated as a function of wavelength, temperature, local atmosphere, and local molecular environment, i.e., attached as a side chain to a polymer or dissolved as a guest in a host polymer. © 1999 American Institute of Physics.
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42.70.Jk Polymers and organics
78.66.Qn Polymers; organic compounds
78.20.Jq Electro-optical effects
82.50.-m Photochemistry
82.30.Qt Isomerization and rearrangement
61.41.+e Polymers, elastomers, and plastics

Beaded carbon tubes

Jyh-Ming Ting and Jones B. C. Lan

Appl. Phys. Lett. 75, 3309 (1999); http://dx.doi.org/10.1063/1.125334 (3 pages) | Cited 6 times

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Unusual tubular carbon structures were observed when preparing carbon tubes using a vapor phase process. Regular, single-diametered carbon tubes were obtained at temperatures below 1300 °C. However, at temperatures greater than 1300 °C, in addition to regular carbon tubes, beaded carbon tubes appeared. The occurrence and appearance of such unusual beaded structure is thought to be related to the growth temperature, and is explained in terms of a three-dimensional nucleation model. © 1999 American Institute of Physics.
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61.48.-c Structure of fullerenes and related hollow and planar molecular structures
81.05.ub Fullerenes and related materials
81.20.-n Methods of materials synthesis and materials processing

Wavelength dependence of the third-order nonlinear optical properties of a polythiophene/selenophene derivative film

Edward Van Keuren, Takanori Wakebe, Reinhard Andreaus, Helmut Möhwald, Wolfgang Schrof, Vladimir Belov, Hiro Matsuda, and Raul Rangel-Rojo

Appl. Phys. Lett. 75, 3312 (1999); http://dx.doi.org/10.1063/1.125335 (3 pages) | Cited 14 times

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The third-order nonlinear optical properties of a hybrid polymer film containing substituted thiophene rings copolymerized with unsubstituted selenophene were measured using the Z-scan technique. Large, resonantly enhanced third-order nonlinearities were found at wavelengths on the low-energy side of the absorption band. In contrast to the results on a similar copolymer film incorporating only thiophene, a strong two-photon absorption appeared in the near infrared. The imaginary part of the third-order susceptibility can be adequately explained as saturation of an exciton band, while the origin of the large negative real part is unknown. © 1999 American Institute of Physics.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.70.Jk Polymers and organics
42.65.An Optical susceptibility, hyperpolarizability
78.66.Qn Polymers; organic compounds
78.30.Jw Organic compounds, polymers

High optical quality AlInGaN by metalorganic chemical vapor deposition

M. E. Aumer, S. F. LeBoeuf, F. G. McIntosh, and S. M. Bedair

Appl. Phys. Lett. 75, 3315 (1999); http://dx.doi.org/10.1063/1.125336 (3 pages) | Cited 36 times

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We report on the metalorganic chemical vapor deposition of the quaternary alloy AlInGaN. We found it desirable to grow quaternary films at temperatures greater than 855 °C in order to suppress deep level emissions in the room-temperature photoluminescence. Details of the conditions necessary to grow In0.1Ga0.9N at 875 °C are presented. Strained and relaxed AlInGaN films were grown with good optical and structural properties for AlN compositions up to 26% and InN content up to 11%. The effects of strain were observed by a difference in the band gap between thin and thick films with the same compositions. The potential impact of the use of quaternary films is discussed regarding strain engineering for the improvement of present device designs. © 1999 American Institute of Physics.  
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Ea III-V semiconductors
68.55.-a Thin film structure and morphology
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
71.20.Nr Semiconductor compounds
68.60.Bs Mechanical and acoustical properties

Patterning a surface on the nanometric scale by ion sputtering

S. Rusponi, G. Costantini, F. Buatier de Mongeot, C. Boragno, and U. Valbusa

Appl. Phys. Lett. 75, 3318 (1999); http://dx.doi.org/10.1063/1.125337 (3 pages) | Cited 54 times

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Surface etching by ion sputtering, besides producing equilibrium-oriented patterns similar to those obtained by molecular beam epitaxy (MBE), can also be used to pattern the surface along nonequilibrium orientations, thus extending the possibilities of MBE. By tuning the competition between ion erosion at grazing angles and diffusion-induced surface reorganization, it is, for example, possible to pattern a substrate characterized by a square symmetry with a well-ordered ripple structure running along any desired direction. © 1999 American Institute of Physics.
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81.65.Cf Surface cleaning, etching, patterning
68.35.B- Structure of clean surfaces (and surface reconstruction)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Bx Metals, semimetals, and alloys

Third-order optical nonlinearity in ZnO microcrystallite thin films

Weili Zhang, H. Wang, K. S. Wong, Z. K. Tang, G. K. L. Wong, and Ravinder Jain

Appl. Phys. Lett. 75, 3321 (1999); http://dx.doi.org/10.1063/1.125338 (3 pages) | Cited 25 times

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We report the measurement of third-order optical nonlinearity (χ(3)) of ZnO microcrystallite thin films near the excitonic resonance at various temperatures using the femtosecond degenerate four-wave-mixing technique. The measured χ(3) response times are 270, 240, and 160 fs at 4.2 K, 77 K, and room temperature, respectively. The values of χ(3) range from 10−7 to 10−4 esu. The maximum values of χ(3) always correspond to the absorption peaks at different temperatures. Room-temperature excitonic enhancement of χ(3) is also observed. © 1999 American Institute of Physics.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.66.Hf II-VI semiconductors
42.65.An Optical susceptibility, hyperpolarizability
78.47.-p Spectroscopy of solid state dynamics
78.40.Fy Semiconductors
71.35.Gg Exciton-mediated interactions
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Interface properties of AlxGa1−xN/AlN heterostructures from optical waveguiding information

E. Dogheche, B. Belgacem, D. Remiens, P. Ruterana, and F. Omnes

Appl. Phys. Lett. 75, 3324 (1999); http://dx.doi.org/10.1063/1.125339 (3 pages) | Cited 14 times

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A complete optical characterization using the prism coupling technique is proposed for AlGaN/AlN heterostructures grown on sapphire substrates by metalorganic vapor-phase epitaxy. In this study, we have qualified the film behavior and the substrate-to-layer interface directly from the measured optical data. The experimental and theoretical approach used for this purpose is described in detail. The results have clearly shown essential changes in the refractive index profile at the interface, which may be related to structural defects, and indicate a good agreement with the trends observed by transmission electron microscopy analysis. © 1999 American Institute of Physics.
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68.35.Ct Interface structure and roughness
78.66.Fd III-V semiconductors
42.79.Gn Optical waveguides and couplers
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Optical and structural properties of epitaxial MgxZn1−xO alloys

A. K. Sharma, J. Narayan, J. F. Muth, C. W. Teng, C. Jin, A. Kvit, R. M. Kolbas, and O. W. Holland

Appl. Phys. Lett. 75, 3327 (1999); http://dx.doi.org/10.1063/1.125340 (3 pages) | Cited 161 times

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The optical and structural properties of high-quality single-crystal epitaxial MgZnO films deposited by pulsed-laser deposition were studied. In films with up to ∼36 at. % Mg incorporation, we have observed intense ultraviolet band edge photoluminescence at room temperature and 77 K. The highly efficient photoluminescence is indicative of the excitonic nature of the material. Transmission spectroscopy was used to show that the excitonic structure of the alloys was clearly visible at room temperature. High-resolution transmission electron microscopy, x-ray diffraction, and Rutherford backscattering spectroscopy/ion channeling were used to verify the epitaxial single-crystal quality of the films and characterize the defect content. Post-deposition annealing in oxygen was found to reduce the number of defects and to improve the optical properties of the films. These results indicate that MgZnO alloys have potential applications in a variety of optoelectronic devices. © 1999 American Institute of Physics.
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78.66.Hf II-VI semiconductors
68.55.-a Thin film structure and morphology
78.55.Et II-VI semiconductors
78.40.Fy Semiconductors
71.55.Gs II-VI semiconductors
81.15.Fg Pulsed laser ablation deposition
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
61.72.Cc Kinetics of defect formation and annealing
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