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3 Nov 2003

Volume 83, Issue 18, pp. 3647-3835

Issue Cover Spotlight Figure

Appl. Phys. Lett. 83, 3737 (2003); http://dx.doi.org/10.1063/1.1623315 (3 pages)

Ian Appelbaum, D. J. Monsma, K. J. Russell, V. Narayanamurti, and C. M. Marcus
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Optical actuation of micromirrors fabricated by the micro-origami technique

José M. Zanardi Ocampo, Pablo O. Vaccaro, Thomas Fleischmann, Te-Sheng Wang, Kazuyoshi Kubota, Tahito Aida, Toshiaki Ohnishi, Akira Sugimura, Ryo Izumoto, Makoto Hosoda, and Shigeki Nashima

Appl. Phys. Lett. 83, 3647 (2003); http://dx.doi.org/10.1063/1.1622800 (3 pages) | Cited 23 times

Online Publication Date: 28 October 2003

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Micromirrors were fabricated by the micro-origami technique. This technique allows the fabrication of simple and robust hinges for movable parts, and it can be applied to any pair of lattice mismatched epitaxial layers, in semiconductors or metals. A multilayer structure, including AlGaAs/GaAs component layers and an InGaAs strained layer, was grown by molecular beam epitaxy on a GaAs substrate. After definition of the hinge and mirror’s shape by photolithography, the micromirrors were released from the substrate by selective etching. They moved to their final position powered by the strain release in the InGaAs layer. Optical actuation was achieved by irradiation with the 488 nm line of an argon laser, and the mirror’s position was measured by sensing the reflection of a He–Ne laser. Continuous wave irradiation with a power density of 450 mW/mm2 produced an angular deflection of the mirror of around 0.5°. The frequency response of the mirrors shows a resonance at 25 kHz. © 2003 American Institute of Physics.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
42.82.Bq Design and performance testing of integrated-optical systems
42.79.Bh Lenses, prisms and mirrors
81.65.Cf Surface cleaning, etching, patterning
81.16.Nd Micro- and nanolithography

Square-lattice photonic crystal microcavities for coupling to single InAs quantum dots

K. Hennessy, C. Reese, A. Badolato, C. F. Wang, A. Imamoglu, P. M. Petroff, E. Hu, G. Jin, S. Shi, and D. W. Prather

Appl. Phys. Lett. 83, 3650 (2003); http://dx.doi.org/10.1063/1.1623319 (3 pages) | Cited 21 times

Online Publication Date: 28 October 2003

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We have observed optical emission from self-assembled InAs/GaAs quantum dots (QDs) embedded within the single-hole-defect, square-lattice (S1) photonic crystal microcavity. Cavities were measured to have quality factors as high as 4000. Finite-difference time-domain (FDTD) calculations were used to determine the specific S1 geometry that is resonant at the center of our ensemble QD spectrum. Extensive, systematic measurements fully confirmed the FDTD simulations and mapped resonant wavelengths as a function of varying lattice constant and hole radius of the photonic crystal structures. © 2003 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
78.67.Hc Quantum dots
78.40.Fy Semiconductors
78.66.Fd III-V semiconductors

Basic enhancement of the overall optical efficiency of intracavity frequency-doubling devices for the 1 μm continuous-wave Nd:Y3Al5O12 laser emission

V. Lupei, N. Pavel, and T. Taira

Appl. Phys. Lett. 83, 3653 (2003); http://dx.doi.org/10.1063/1.1616667 (3 pages) | Cited 12 times

Online Publication Date: 28 October 2003

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The possibility of basic enhancement of the overall optical-to-optical efficiency of intracavity frequency-doubling devices for the 1 μm continuous-wave (cw) Nd lasers by direct pumping into the emitting level and by using concentrated laser materials is discussed. This possibility is demonstrated for 1.0 and 2.4 at. % Nd:Y3Al5O12 (Nd:YAG) crystals pumped by a Ti:sapphire laser at 885 nm. A slope efficiency of 0.79 in absorbed pump power was obtained for the 1064 nm emission of a 1.0 at. % Nd:YAG crystal. The effect of enhancement of intracavity emission on the second-harmonic emission is manifested in a drastic reduction of emission threshold and in an increased dependence on the absorbed power. The use of concentrated Nd:YAG crystal enables a better use of the pump power and improves the overall optical efficiency of the intracavity frequency-doubling devices. © 2003 American Institute of Physics.
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42.70.Hj Laser materials
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

A THz transverse electromagnetic mode two-dimensional interconnect layer incorporating quasi-optics

S. Coleman and D. Grischkowsky

Appl. Phys. Lett. 83, 3656 (2003); http://dx.doi.org/10.1063/1.1624474 (3 pages) | Cited 27 times

Online Publication Date: 28 October 2003

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We report the demonstration of a planar THz interconnect layer capable of transmitting subpicosecond pulses in the transverse electromagnetic (TEM) mode over arbitrarily long paths with low absorption and no observable group velocity dispersion. Quasioptical elements are incorporated within the interconnect layer forming a configurable THz bandwidth TEM-mode planar interconnect with negligible group velocity dispersion and low loss. For a 146 mm guided path length, including four reflections, the pulses are broadened by the frequency dependent absorption of the interconnect layer from 0.28 to 0.32 ps, and attenuated by the factor 0.2. © 2003 American Institute of Physics.
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84.40.Az Waveguides, transmission lines, striplines
85.40.Ls Metallization, contacts, interconnects; device isolation
85.60.Bt Optoelectronic device characterization, design, and modeling
42.79.Bh Lenses, prisms and mirrors
07.57.Hm Infrared, submillimeter wave, microwave, and radiowave sources

High-power blue generation from a periodically poled MgO:LiNbO3 ridge-type waveguide by frequency doubling of a diode end-pumped Nd:Y3Al5O12 laser

M. Iwai, T. Yoshino, S. Yamaguchi, M. Imaeda, N. Pavel, I. Shoji, and T. Taira

Appl. Phys. Lett. 83, 3659 (2003); http://dx.doi.org/10.1063/1.1623938 (3 pages) | Cited 33 times

Online Publication Date: 28 October 2003

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Continuous-wave power of 189 mW at 473 nm with 49% conversion efficiency is generated from a 8.5 mm long uncoated periodically polled MgO:LiNbO3 ridge-type waveguide by frequency doubling of a diode end-pumped Nd:Y3Al5O12 laser at room temperature; the corresponding internal blue power and conversion efficiency were 222 mW and 58%, respectively. The highest conversion efficiency of 63% (74% with respect to the blue internal power) was obtained from a 12 mm long waveguide with 99 mW blue output power. Saturation of output blue power was observed for coupled fundamental power into the waveguides in excess of 200 mW. © 2003 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Nv Optical frequency converters
42.79.Gn Optical waveguides and couplers
42.65.Wi Nonlinear waveguides

Enhanced light diffraction from a double-layer microsphere lattice

Hideki T. Miyazaki, Hiroshi Miyazaki, Norio Shinya, and Kenjiro Miyano

Appl. Phys. Lett. 83, 3662 (2003); http://dx.doi.org/10.1063/1.1623932 (3 pages) | Cited 6 times

Online Publication Date: 28 October 2003

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Anomalously strong diffraction, whose efficiency is as high as 55%, has been observed from a double-layer microsphere lattice. The enhancement is due to the specular resonance scattering from two spheres in contact, each belonging to the top and bottom layers of the double-layer, respectively. The system thus works as a single layer two-dimensional (2D) lattice of bispheres. No enhancement is observed from a single-layer lattice nor from triple-layer lattice. It functions as a “blazed” transmission grating with 2D spectral dispersion compared with the one-dimensional dispersion in ordinary linear gratings. © 2003 American Institute of Physics.
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42.25.Fx Diffraction and scattering
42.79.Dj Gratings

Efficiency of local light-plasmon coupling

H. Ditlbacher, J. R. Krenn, A. Hohenau, A. Leitner, and F. R. Aussenegg

Appl. Phys. Lett. 83, 3665 (2003); http://dx.doi.org/10.1063/1.1625107 (3 pages) | Cited 31 times

Online Publication Date: 28 October 2003

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We investigate quantitatively the local coupling efficiency of a strongly focused laser beam to surface plasmon polaritons on a gold thin film. The coupling is mediated by gold ridges with nanoscale cross section. The coupling efficiency is determined by measuring the leakage radiation emitted by the surface plasmon polaritons into the glass substrate supporting the thin film. © 2003 American Institute of Physics.
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78.68.+m Optical properties of surfaces
78.66.Bz Metals and metallic alloys
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
73.22.Lp Collective excitations
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.55.Hx Other solid inorganic materials

Self-induced transparency in InGaAs quantum-dot waveguides

S. Schneider, P. Borri, W. Langbein, U. Woggon, J. Förstner, A. Knorr, R. L. Sellin, D. Ouyang, and D. Bimberg

Appl. Phys. Lett. 83, 3668 (2003); http://dx.doi.org/10.1063/1.1624492 (3 pages) | Cited 15 times

Online Publication Date: 28 October 2003

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We report the experimental observation and the theoretical modeling of self-induced-transparency signatures such as nonlinear transmission, pulse retardation and reshaping, for subpicosecond pulse propagation in a 2-mm-long InGaAs quantum-dot ridge waveguide in resonance with the excitonic ground-state transition at 10 K. The measurements were obtained by using a cross-correlation frequency-resolved optical gating technique which allows us to retrieve the field amplitude of the propagating pulses. © 2003 American Institute of Physics.
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42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
42.79.Gn Optical waveguides and couplers
42.65.Wi Nonlinear waveguides
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Influence of dimensionality on the emission spectra of nanostructures

V. M. Apalkov and Tapash Chakraborty

Appl. Phys. Lett. 83, 3671 (2003); http://dx.doi.org/10.1063/1.1625785 (3 pages)

Online Publication Date: 28 October 2003

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We report on our results of the numerical simulations of a quantum dot (quantum wire)-quantum well cascade structure. Experimental work on the quantum dot structure was recently reported in the literature. For parameters of such a structure, the calculated emission spectra has a single peak for up to four electrons in the dot. The width of the emission line is found to be due to long-range in-plane disorder, resulting mainly due to fluctuations of the height of the dots. © 2003 American Institute of Physics.
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78.67.De Quantum wells
78.67.Hc Quantum dots
78.67.Lt Quantum wires
78.60.Fi Electroluminescence
42.55.Px Semiconductor lasers; laser diodes
68.65.Fg Quantum wells
68.65.Hb Quantum dots (patterned in quantum wells)
68.65.La Quantum wires (patterned in quantum wells)
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Continuum radiation from electron-dust-chain collisions in dusty plasmas

Young-Dae Jung

Appl. Phys. Lett. 83, 3674 (2003); http://dx.doi.org/10.1063/1.1623946 (3 pages) | Cited 2 times

Online Publication Date: 28 October 2003

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The bremsstrahlung emission due to collisions of nonrelativistic electrons with chains of strongly coupled dust grains in a plasma is investigated in dusty plasmas. The dust chain is considered as the one-dimensional model for strongly coupled dusty plasmas. The Born approximation is assumed for the initial and final states of the projectile electron and coherent effects are considered. The result shows that the radiation cross section is greater for smaller dust spacing for soft photon regions. This work shows a possibility of the low energy continuum radiation due to the electron-dust-chain collisions in dusty plasmas. © 2003 American Institute of Physics.
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52.27.Lw Dusty or complex plasmas; plasma crystals
52.20.Fs Electron collisions
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.65.-y Plasma simulation
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Mechanism for the increased light transmission through Ni/Au/ZnO contacts on p-GaN for high power optoelectronic devices

C. L. Tseng, M. J. Youh, G. P. Moore, M. A. Hopkins, R. Stevens, and W. N. Wang

Appl. Phys. Lett. 83, 3677 (2003); http://dx.doi.org/10.1063/1.1619558 (3 pages) | Cited 6 times

Online Publication Date: 28 October 2003

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The mechanisms responsible for the transparency of Ni/Au and Ni/Au/ZnO on p-GaN has been investigated. It was found that the optical transmission of Ni/Au contacts is dominated by the film thickness and morphology. A change in film thickness, induced by thermal annealing, results in a more transparent contact material. In addition a ZnO film was used as an antireflection layer on top of a Ni/Au contact. The Ni/Au/ZnO film was found to have an increased light transmission of 15% compared with an annealed Ni/Au contact. The maximum optical transmission measured through the Ni/Au/ZnO contact was 90%. © 2003 American Institute of Physics.
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78.66.Fd III-V semiconductors
61.72.Cc Kinetics of defect formation and annealing

InAs quantum dots on the GaAs(math math math)B surface

Y. Temko, T. Suzuki, M. C. Xu, and K. Jacobi

Appl. Phys. Lett. 83, 3680 (2003); http://dx.doi.org/10.1063/1.1624472 (3 pages) | Cited 9 times

Online Publication Date: 28 October 2003

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We report on InAs quantum dots grown by molecular-beam epitaxy on the stable GaAs(math math math)B surface discovered recently. Atomically resolved scanning tunneling microscopy images acquired in situ reveal compact quantum dots terminated by (math0math), (0mathmath), and (mathmathmath)B facets and an unresolved vicinal (00math) region. A flat base of (mathmathmath)B orientation extends in front of the (math0math) and (mathmathmath)B facets. The quantum dots exhibit a very narrow size distribution attributed to the well ordered substrate and to high nucleation efficiency. © 2003 American Institute of Physics.
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81.07.Ta Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Infrared reflectivity of (GaAs)m/(AlAs)n superlattices

G. Yu, N. L. Rowell, D. J. Lockwood, and Z. R. Wasilewski

Appl. Phys. Lett. 83, 3683 (2003); http://dx.doi.org/10.1063/1.1622782 (3 pages) | Cited 9 times

Online Publication Date: 28 October 2003

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We report an original analysis method to model the p-polarized infrared reflectivity (IR) spectra of (GaAs)m/(AlAs)n superlattices (m = 36, 4<n<7) grown on semi-insulating GaAs (100). In our fitting procedure, the first derivative of the IR spectrum was calculated numerically and the respective dielectric functions of the AlAs barriers and GaAs quantum wells were described by two independent factorized models, with the thickness of the AlAs layers treated as a free parameter. The longitudinal and transverse optical phonon frequencies of the GaAs layers were found to be independent of the AlAs layer thickness, while those of the AlAs layer decreased in accordance with theory and their linewidths increased with increasing confinement. © 2003 American Institute of Physics.
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78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.30.Fs III-V and II-VI semiconductors
81.05.Ea III-V semiconductors
73.21.Cd Superlattices
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
68.65.Cd Superlattices

Dielectric functions of ferroelectric Bi3.25La0.75Ti3O12 thin films on Si(100) substrates

Z. G. Hu, J. H. Ma, Z. M. Huang, Y. N. Wu, G. S. Wang, and J. H. Chu

Appl. Phys. Lett. 83, 3686 (2003); http://dx.doi.org/10.1063/1.1619208 (3 pages) | Cited 16 times

Online Publication Date: 28 October 2003

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Ferroelectric Bi3.25La0.75Ti3O12 (BLT) thin films were deposited directly on Si(100) substrates under annealing temperatures of 590 and 700 °C. The optical properties of the BLT films have been investigated using spectroscopic ellipsometry at room temperature in the 0.73–6 eV energy range. To model the dielectric functions of the BLT films, the double Tauc–Lorentz dispersion relation was successfully adopted. A four-layer model was used to fit the measured pseudodielectric function in order to deduce the complex dielectric functions. The results show that the annealing temperature mainly affects the dielectric functions of the BLT films beyond the fundamental band gap energy. The volume fraction of air present in the surface rough layer increases with increasing annealing temperature. The fundamental band gap was observed to shift slightly to a higher energy at a high annealing temperature. The difference of the optical properties due to the structure changes testifies the x-ray diffraction spectral results. © 2003 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)
61.72.Cc Kinetics of defect formation and annealing
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.40.Gh Other heat and thermomechanical treatments
68.55.-a Thin film structure and morphology

Line spectra from doped nano-oxide: A design for nanooptics

Igor S. Altman, Peter V. Pikhitsa, Mansoo Choi, Jae In Jeong, Ho-Jun Song, Igor E. Agranovski, and Thor E. Bostrom

Appl. Phys. Lett. 83, 3689 (2003); http://dx.doi.org/10.1063/1.1624638 (3 pages) | Cited 8 times

Online Publication Date: 28 October 2003

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We report the photoluminescence (PL) observation of extremely sharp zero-phonon lines originating from transitions of Mn2+ and Cr3+ ions embedded into MgO matrix of nanoscale (nanocrystals and films). The excellent performance of PL compared to that from quantum dots makes our finding attractive for applications. © 2003 American Institute of Physics.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.55.Hx Other solid inorganic materials

F spots and domain patterns in rhombohedral PbZr0.90Ti0.10O3

Haitao Huang, Li Min Zhou, Jun Guo, Huey Hoon Hng, Joo Tien Oh, and Peter Hing

Appl. Phys. Lett. 83, 3692 (2003); http://dx.doi.org/10.1063/1.1624632 (3 pages) | Cited 8 times

Online Publication Date: 28 October 2003

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The microstructure of PbZr0.9Ti0.1O3 ceramics is studied by transmission electron microscopy. Two types of domain patterns are found, namely, the 109° domain with the F spots (½{hkl} superlattice reflections) observed in neighboring domains and the 71° domain with the F spots observed in one domain and having disappeared in the neighboring one. The computer simulation indicates that the F spots are forbidden at h = k positions so that they do not appear in the electron diffraction pattern if viewed along the [math10] direction. Based on this result, the observed two types of domain patterns and their corresponding diffraction patterns can be explained. © 2003 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.)

Evolution of shape, height, and in-plane lattice constant of Ge-rich islands during capping with Si

Zhenyang Zhong, J. Stangl, F. Schäffler, and G. Bauer

Appl. Phys. Lett. 83, 3695 (2003); http://dx.doi.org/10.1063/1.1622785 (3 pages) | Cited 12 times

Online Publication Date: 28 October 2003

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The surface morphology of Ge-rich islands on Si (001) substrates capped with 0 to 10 monolayers (MLs) of Si at 550 °C was investigated by atomic force microscopy. An evolution of the island shape from domes to pyramids was observed, which coincides with a dramatic decrease of the island height during overgrowth. The average lateral lattice constant 〈a∥〉 of the Ge-rich islands for a series of samples was obtained from grazing incidence x-ray diffraction. 〈a∥〉 decreases appreciably with deposition of the Si cap layer, even for a cap thickness as low as 1.3 MLs. At the beginning of overgrowth, Si incorporation promotes the shape evolution and the size variation of the islands. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.05.Hd Other semiconductors
68.37.Ps Atomic force microscopy (AFM)
68.49.Uv X-ray standing waves

Formation and localization of internal polymer columnar structures in liquid crystal cells

Qingbing Wang, L.-C. Chien, and Satyendra Kumar

Appl. Phys. Lett. 83, 3698 (2003); http://dx.doi.org/10.1063/1.1623325 (3 pages) | Cited 3 times

Online Publication Date: 28 October 2003

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Internal polymer columnar structures in liquid crystal (LC) cells have been produced using the method of thermally-induced phase separation of LC/prepolymer solution and solidified by photopolymerization. These polymer columns adhere to both substrates and enhance control of the LC cell spacing and mechanical stability. The existence and profile of the polymer columns were investigated by optical and scanning electron microscopy techniques. Supertwisted nematic LC cells with polymer columnar structures have been constructed using this method and their electro-optical characteristics measured. © 2003 American Institute of Physics.
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61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures
42.79.Kr Display devices, liquid-crystal devices
78.20.Jq Electro-optical effects
61.25.H- Macromolecular and polymers solutions; polymer melts
42.70.Df Liquid crystals
64.75.-g Phase equilibria
61.41.+e Polymers, elastomers, and plastics
82.50.-m Photochemistry
64.70.D- Solid-liquid transitions
81.30.Fb Solidification
42.70.Jk Polymers and organics

Uniformity of optical absorption in HgCdTe epilayer measured by infrared spectromicroscopy

J. D. Phillips, K. Moazzami, J. Kim, D. D. Edwall, D. L. Lee, and J. M. Arias

Appl. Phys. Lett. 83, 3701 (2003); http://dx.doi.org/10.1063/1.1625776 (3 pages) | Cited 6 times

Online Publication Date: 28 October 2003

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Infrared absorption in HgCdTe epitaxial material has been investigated using infrared spectromicroscopy to study the uniformity at dimensions representative of typical infrared detectors. Infrared transmission measurements were performed on HgCdTe material using an infrared beam diameter of 9 μm. Line scans and area maps of transmission spectra were obtained to investigate statistical variations in infrared absorption. The HgCdTe material demonstrates a high degree of uniformity, with a standard deviation in absorption coefficient near the sensitive turn-on region of less than 3% and standard deviation in extracted Hg1-xCdxTe compositon of 3×10−4. © 2003 American Institute of Physics.
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78.66.Hf II-VI semiconductors
78.30.Fs III-V and II-VI semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
85.60.Gz Photodetectors (including infrared and CCD detectors)

Solid-liquid phase transitions in CdTe crystals under pulsed laser irradiation

V. A. Gnatyuk, T. Aoki, O. S. Gorodnychenko, and Y. Hatanaka

Appl. Phys. Lett. 83, 3704 (2003); http://dx.doi.org/10.1063/1.1625777 (3 pages) | Cited 7 times

Online Publication Date: 28 October 2003

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Phase transitions in CdTe crystals irradiated with nanosecond KrF (248 nm) excimer laser pulses were investigated by a numerical simulation and time-resolved reflectivity method. By solving the time-dependent heat flow equation and taking into account the temperature dependences of semiconductor parameters, the time dependence of the surface temperature in a CdTe crystal was calculated as a function of laser pulse intensity. The dynamics of laser-induced melting was directly monitored by measurements of the reflection coefficient of a probe laser beam (532 nm). The melting and ablation thresholds have been determined as 2.5 and 7.3 MW/cm2, respectively. © 2003 American Institute of Physics.
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Fk Semiconductors
68.35.Rh Phase transitions and critical phenomena
64.70.D- Solid-liquid transitions
79.20.Ds Laser-beam impact phenomena
78.47.-p Spectroscopy of solid state dynamics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.68.+m Optical properties of surfaces
68.35.Md Surface thermodynamics, surface energies
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Thermal detrapping analysis of pumping-related defects in diamond

Marco Marinelli, E. Milani, M. E. Morgada, G. Pucella, G. Rodriguez, A. Tucciarone, G. Verona-Rinati, M. Angelone, and M. Pillon

Appl. Phys. Lett. 83, 3707 (2003); http://dx.doi.org/10.1063/1.1623318 (3 pages) | Cited 3 times

Online Publication Date: 28 October 2003

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A method is presented to selectively characterize the traps involved in the pumping procedure of diamond films. The pumping process strongly reduces the concentration of active carrier trapping centers, leading to an enhancement of electronic properties of such material, and is obtained by irradiating the diamond films with ionizing radiation. Since the improved transport properties lead to an increased efficiency when diamond films are used as radiation detectors, valuable information on this process can be obtained by analyzing the response of diamond based particle detectors. For this purpose a high-quality diamond film was grown by microwave chemical vapor deposition and a particle detector was realized. Its response to a 5.5-MeV 241Am α-particles was measured after successive annealing steps performed at different temperatures in the 180–228 °C range. Before each annealing curve at a given temperature, the detector was driven to the pumped state through β-particle irradiation. The efficiency versus annealing time curves evidence a thermally induced detrapping, confirming the pumping mechanism as a filling and consequent passivation of defects. The analysis of the decay time of the detector efficiency as a function of temperature allows the determination of the activation energy of these defects, which is Ea = 1.62±0.15 eV. © 2003 American Institute of Physics.
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29.40.Wk Solid-state detectors
81.05.U- Carbon/carbon-based materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
71.55.Cn Elemental semiconductors

Metastability of two-hydrogen complexes in silicon

D. J. Chadi

Appl. Phys. Lett. 83, 3710 (2003); http://dx.doi.org/10.1063/1.1624476 (3 pages) | Cited 7 times

Online Publication Date: 28 October 2003

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A two-hydrogen interstitial complex (H2∗∗) in crystalline Si that exhibits metastability is proposed via first-principles total energy calculations. In its most stable state, H2∗∗ is 0.28 eV/H higher in energy than H2∗ and is electron-spin-resonance inactive. The complex has a metastable spin active state arising from a Si dangling-bond in which the H–H separation is 2.39 Å. The properties of H2∗∗ make it a promising candidate for the defect responsible for the Staebler–Wronski effect in amorphous Si. © 2003 American Institute of Physics.
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71.55.Cn Elemental semiconductors
61.72.J- Point defects and defect clusters
76.30.Mi Color centers and other defects

Oxidation rate enhancement of SiGe epitaxial films oxidized in dry ambient

M. Spadafora, G. Privitera, A. Terrasi, S. Scalese, C. Bongiorno, A. Carnera, M. Di Marino, and E. Napolitani

Appl. Phys. Lett. 83, 3713 (2003); http://dx.doi.org/10.1063/1.1622439 (3 pages) | Cited 17 times

Online Publication Date: 28 October 2003

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We present a study on thin oxides obtained by rapid thermal oxidation of Si1−xGex epitaxial layers. The oxidation processes were performed in dry O2 at 1000 °C for times up to 600 s. Our data show an oxide growth rate enhancement with respect to pure Si. Except for a very small amount of GeO2 that is found at the surface, all the Ge is rejected towards the SiO2/SiGe interface, forming a Ge-enriched layer free of extended defects. The comparison of our results for dry processes with those reported in the literature for wet ambient supports the idea that the kinetics of SiGe oxidation is controlled by similar mechanisms in both cases, in contrast with models and interpretations so far proposed. © 2003 American Institute of Physics.
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81.65.Mq Oxidation
81.05.Hd Other semiconductors

Engineering carrier confinement potentials in 1.3-μm InAs/GaAs quantum dots with InAlAs layers: Enhancement of the high-temperature photoluminescence intensity

H. Y. Liu, I. R. Sellers, M. Hopkinson, C. N. Harrison, D. J. Mowbray, and M. S. Skolnick

Appl. Phys. Lett. 83, 3716 (2003); http://dx.doi.org/10.1063/1.1622443 (3 pages) | Cited 18 times

Online Publication Date: 28 October 2003

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We describe an optical study of structures consisting of an InAlAs-GaAs strained buffer layer and an InAlAs-InGaAs composite strain-reducing layer designed to modify the confining potential of 1.3-μm InAs/GaAs quantum dots (QDs). With increasing (decreasing) InAlAs (InGaAs) thickness in the strain-reducing layer grown above the QDs, the integrated photoluminescence (PL) intensity of the QD ground-state transition increases dramatically and the emission wavelength decreases slightly from 1.36 to 1.31 μm. The enhancement of PL efficiency is temperature dependent, being much greater above 200 K. A maximum enhancement of 450 is achieved at room temperature. This improvement of the high-temperature PL efficiency should lead to a significant improvement in the characteristics of 1.3-μm InAs/GaAs QD lasers. © 2003 American Institute of Physics.
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73.21.La Quantum dots
78.67.Hc Quantum dots
81.07.Ta Quantum dots
42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.05.Ea III-V semiconductors
78.55.Cr III-V semiconductors

Effect of quantum-well confinement on acceptor state lifetime in δ -doped GaAs/AlAs multiple quantum wells

W. M. Zheng, M. P. Halsall, P. Harrison, J.-P. R. Wells, I. V. Bradley, and M. J. Steer

Appl. Phys. Lett. 83, 3719 (2003); http://dx.doi.org/10.1063/1.1623950 (3 pages) | Cited 6 times

Online Publication Date: 28 October 2003

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Using far-infrared time-resolved spectroscopy, we have investigated the effect of quantum-well confinement on the lifetime of shallow acceptor states in GaAs/AlAs multiple quantum wells with Be δ-doping at the well center. Low-temperature far-infrared absorption measurements clearly show three principal absorption lines due to transitions of Be acceptor states from the ground state to the first three odd-parity excited states, respectively. It is found that the lifetime of excited states monotonically reduces with decreasing quantum-well width, from 350 ps in bulk to 55 ps in a 100 Å well. We suggest that the effect of quantum-well confinement on zone-fold acoustic-phonon modes increases the intra-acceptor scattering rate of acoustic-phonon-assisted relaxation. © 2003 American Institute of Physics.
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73.21.Fg Quantum wells
78.67.De Quantum wells
71.55.Eq III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
78.47.-p Spectroscopy of solid state dynamics
63.20.K- Phonon interactions
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
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