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11 Sep 2000

Volume 77, Issue 11, pp. 1569-1731

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Temperature dependence of the thermo-optic coefficient of InP, GaAs, and SiC from room temperature to 600 K at the wavelength of 1.5 μm

Francesco G. Della Corte, Giuseppe Cocorullo, Mario Iodice, and Ivo Rendina

Appl. Phys. Lett. 77, 1614 (2000); http://dx.doi.org/10.1063/1.1308529 (3 pages) | Cited 31 times

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The thermo-optic coefficient ∂n/∂T has been measured from room temperature to 600 K at the wavelength of 1523 nm in three important semiconductors for fiber-optic device fabrication, namely, InP, GaAs, and 6H–SiC. The adopted technique is very simple and is based on the observation of the periodicity of the signal transmitted, at the desired wavelength, by an étalon made of the material under test, when it experiences a temperature variation. The values of ∂n/∂T measured in InP and GaAs at room temperature are in agreement with previously reported ones, but increase with temperature with a weak quadratic dependence. SiC conversely shows a lower thermo-optic coefficient (2.77×10−5 K−1) at 300 K, which, however, doubles for a 300 K temperature increase. © 2000 American Institute of Physics.
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78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
81.05.Ea III-V semiconductors

Effect of size and roughness on light transmission in a Si/SiO2 waveguide: Experiments and model

Kevin K. Lee, Desmond R. Lim, Hsin-Chiao Luan, Anuradha Agarwal, James Foresi, and Lionel C. Kimerling

Appl. Phys. Lett. 77, 1617 (2000); http://dx.doi.org/10.1063/1.1308532 (3 pages) | Cited 140 times

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In this letter, we experimentally evaluate the effect of miniaturization and surface roughness on transmission losses within a Si/SiO2 waveguide system, and explain the results using a theoretical model. Micrometer/nanometer-sized waveguides are imperative for its potential use in dense integrated optics and optical interconnection for silicon integrated circuits. A theoretical model was employed to predict the relationship between the transmission losses of the dielectric silicon waveguide and its width. This model accurately predicts that loss increases as waveguide width decreases. Furthermore, we show that a major source of loss comes from sidewall roughness. We have constructed a complete contour map showing the interdependence of sidewall roughness and transmission loss, to assist users in their design of an optimal waveguide fabrication process that minimizes loss. Additionally, users can find an effective path to reduce the scattering loss from sidewall roughness. Using this map, we confirm that nanometer-size silicon waveguides with 0.1 dB/cm transmission loss are possible with the currently available technology. © 2000 American Institute of Physics.
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42.82.Et Waveguides, couplers, and arrays
42.82.Bq Design and performance testing of integrated-optical systems
85.60.Bt Optoelectronic device characterization, design, and modeling
42.79.Gn Optical waveguides and couplers

Selective growth of nanocrystalline Si dots using an ultrathin-Si-oxide/oxynitride mask

Noriyuki Miyata, Heiji Watanabe, and Masakazu Ichikawa

Appl. Phys. Lett. 77, 1620 (2000); http://dx.doi.org/10.1063/1.1308523 (3 pages) | Cited 2 times

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We demonstrate the selective growth of nanocrystalline Si (nc–Si) dots by using ultrathin-Si-oxide/oxynitride mask and low-pressure chemical vapor deposition. The oxynitride layer is selectively grown on the Si(001)–2×1 open window formed in the ultrathin oxide layer by electron-beam-induced selective thermal decomposition. The 10-nm-scale hemispherical nc–Si dots grow selectively on the oxynitride-covered window within the incubation period in which Si growth does not occur on the oxide-covered surface. © 2000 American Institute of Physics.
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81.05.Cy Elemental semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.07.-b Nanoscale materials and structures: fabrication and characterization

Dome-to-pyramid shape transition in Ge/Si islands due to strain relaxation by interdiffusion

William L. Henstrom, Chuan-Pu Liu, J. Murray Gibson, T. I. Kamins, and R. Stanley Williams

Appl. Phys. Lett. 77, 1623 (2000); http://dx.doi.org/10.1063/1.1309027 (3 pages) | Cited 25 times

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Ge islands were grown on Si(001) and then annealed at 650 °C for 0, 20, 40, and 60 min in a chemical-vapor deposition reactor following Ge deposition. This letter confirms the previous observations directly. By combining the ability to quantify strain with the ability to measure island dimensions in a transmission electron microscope, we were able to plot strain versus aspect ratio for the various annealing times. The islands first relax strain because of Si intermixing with the Ge epilayer causes the lattice mismatch to be lowered. Once the mismatch is sufficiently reduced, and thus the strain energy sufficiently reduced, it becomes favorable for the islands to reverse their shape back from domes to pyramids, thus reducing surface energy. This confirms the reversibility of island shape and thus the thermodynamics of the transition. © 2000 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
68.35.Rh Phase transitions and critical phenomena
66.30.Ny Chemical interdiffusion; diffusion barriers
61.72.Cc Kinetics of defect formation and annealing
68.35.Md Surface thermodynamics, surface energies
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances

Layer-by-layer growth of GaN induced by silicon

A. Munkholm, Carol Thompson, M. V. Ramana Murty, J. A. Eastman, O. Auciello, G. B. Stephenson, P. Fini, S. P. DenBaars, and J. S. Speck

Appl. Phys. Lett. 77, 1626 (2000); http://dx.doi.org/10.1063/1.1309023 (3 pages) | Cited 19 times

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We present in situ x-ray scattering studies of surface morphology evolution during metal–organic chemical vapor deposition of GaN. Dosing the GaN(0001) surface with Si is shown to change the growth mode from step-flow to layer-by-layer over a wide temperature range. Annealing of highly doped layers causes Si to segregate to the surface, which also induces layer-by-layer growth. © 2000 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.70.Ck X-ray scattering
61.72.Cc Kinetics of defect formation and annealing
64.75.-g Phase equilibria

Microstructural evolution of laser-exposed silicon targets in SF6 atmospheres

J. D. Fowlkes, A. J. Pedraza, and D. H. Lowndes

Appl. Phys. Lett. 77, 1629 (2000); http://dx.doi.org/10.1063/1.1308538 (3 pages) | Cited 21 times

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The microstructures formed at the surface of silicon during pulsed-laser irradiation in SF6-rich atmospheres consist of an array of microholes surrounded by microcones. It is shown that there is a dynamic interplay between the formation of microholes and microcones. Fluorine produced by the laser-induced decomposition of SF6 is most likely responsible for the etching/ablation process. It is proposed that silicon-rich molecules and clusters that form in and are ejected from the continually deepening microholes sustain the axial and lateral growth of the microcones. The laser-melted layer at the tip and sides of the cones efficiently collects the silicon-rich products formed upon ablation. The total and partial pressures of SF6 in the chamber play a major role in cone development, a clear indication that it is the laser-generated plasma that controls the growth of these cones. © 2000 American Institute of Physics.
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81.65.-b Surface treatments
81.05.Cy Elemental semiconductors
79.20.Ds Laser-beam impact phenomena
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Fk Semiconductors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
68.35.B- Structure of clean surfaces (and surface reconstruction)

Radiative and nonradiative recombination processes in lattice-matched (Cd,Zn)O/(Mg,Zn)O multiquantum wells

T. Makino, C. H. Chia, Nguen T. Tuan, Y. Segawa, M. Kawasaki, A. Ohtomo, K. Tamura, and H. Koinuma

Appl. Phys. Lett. 77, 1632 (2000); http://dx.doi.org/10.1063/1.1308540 (3 pages) | Cited 55 times

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Time-resolved photoluminescence studies have been performed on (Cd,Zn)O/(Mg,Zn)O multiquantum wells, which are almost perfectly lattice matched (0.034%), grown by laser molecular-beam epitaxy on a ScAlMgO4 substrate. Radiative recombination of excitons in the wells exhibits a significant spectral distribution of times. This distribution was interpreted in terms of localization of excitons by potential fluctuations due to alloy disorder and to well width and depth variations. The temperature dependence of the radiative lifetime of excitons was deduced from the measurement of both the photoluminescence decay time and intensity. We found that the radiative lifetime increases linearly with temperature, showing a two-dimensional feature of excitons in the quantum wells. © 2000 American Institute of Physics.
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78.55.Et II-VI semiconductors
81.05.Dz II-VI semiconductors
78.47.-p Spectroscopy of solid state dynamics
78.66.Hf II-VI semiconductors
73.61.Ga II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.35.-y Excitons and related phenomena
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Size control of erbium-doped silicon nanocrystals

John St. John, Jeffery L. Coffer, Yandong Chen, and Russell F. Pinizzotto

Appl. Phys. Lett. 77, 1635 (2000); http://dx.doi.org/10.1063/1.1309022 (3 pages) | Cited 11 times

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This work describes the effects of pyrolysis oven length and erbium precursor on the preparation of discrete erbium-doped silicon nanoparticles. These doped nanoparticles were prepared by the co-pyrolysis of disilane and the volatile complex Er(tmhd)3 (tmhd=2,2,6,6-tetramethyl-3,5-heptanedionato). The particle sizes and size distributions were determined using high resolution and conventional transmission electron microscopy. Erbium-doped silicon nanoparticles exhibit a selected area electron diffraction pattern consistent with the diamond cubic phase and a distinctive dark contrast in the transmission electron microscope. The presence of erbium is confirmed by x-ray energy dispersive spectroscopy. In general, the mean diameter of the individual nanoparticles increases as the length of the pyrolysis oven used during their preparation is increased. © 2000 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
61.46.-w Structure of nanoscale materials
81.05.Cy Elemental semiconductors
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

InGaN/GaN multiple quantum wells grown by metalorganic vapor phase epitaxy with mass transport

G. Pozina, J. P. Bergman, B. Monemar, M. Iwaya, S. Nitta, H. Amano, and I. Akasaki

Appl. Phys. Lett. 77, 1638 (2000); http://dx.doi.org/10.1063/1.1310175 (3 pages) | Cited 10 times

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We report on studies of In0.12Ga0.88N/GaN heterostructures with three 35-Å-thick quantum wells (QWs) grown on sapphire substrates by metalorganic vapor phase epitaxy with employment of mass transport. The structure is demonstrated to show good structural and optical properties. The threading dislocation density is less than 107 cm−2 for the mass-transport regions. The photoluminescence (PL) spectrum is dominated by the rather narrow near-band gap emission at 2.97 eV with a linewidth of 40 meV. This emission has a typical PL decay time about 5 ns at 2 K within the PL contour. With increasing excitation intensity, an additional transition with longer decay time (about 200 ns) is enhanced at energy about 2.85 eV. The position of this line depends strongly on the excitation power. We explain the data in terms of a model, where the PL is a result of contribution from at least two nonequivalent QWs, which could be realized due to a potential gradient across the layers. © 2000 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.47.-p Spectroscopy of solid state dynamics

Controlled assembly of two-dimensional colloidal crystals

Q.-H. Wei, D. M. Cupid, and X. L. Wu

Appl. Phys. Lett. 77, 1641 (2000); http://dx.doi.org/10.1063/1.1310210 (3 pages) | Cited 7 times

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Under the influence of capillary forces, colloidal particles embedded in a soap film self-organize to form polycrystalline monolayers when the film is withdrawn from a concentrated suspension. Here, we show that mechanically generated capillary waves on the free surface of the bulk colloidal suspension can cause migration of grain boundaries, and under certain conditions, completely eliminate them. This dramatic effect, we call “mechanic annealing,” provides a robust means of growing two-dimensional single crystals with size that has never been achieved before. The method is expected to be applicable to a variety of self-assembling systems. © 2000 American Institute of Physics.
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82.70.Dd Colloids
68.18.-g Langmuir-Blodgett films on liquids

On the use of total reflection x-ray topography for the observation of misfit dislocation strain at the surface of a Si/Ge–Si heterostructure

Patrick J. McNally, G. Dilliway, J. M. Bonar, A. Willoughby, T. Tuomi, R. Rantamäki, A. N. Danilewsky, and D. Lowney

Appl. Phys. Lett. 77, 1644 (2000); http://dx.doi.org/10.1063/1.1308269 (3 pages) | Cited 5 times

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Synchrotron x-ray topography was used in total reflection topography (TRT) mode to observe strain-induced surface bumps due to the presence of underlying misfit dislocations in strained-layer SiGe on Si epitaxial heterostructures. In these experiments, the x rays approached the sample surfaces at grazing incident angles below the critical angles for total external reflection for a number of reflections, and hence, surface strain features nominally less than a few tens of angstrøms from the sample surface have been observed. These are similar to the surface bumpiness observed by atomic force microscopy, albeit on a much larger lateral length scale. The fact that TRT mode images were taken was confirmed by the observation of conventional backreflection topographic images of misfit dislocations in all samples when the grazing incidence angle became greater than the critical angle. © 2000 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
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