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9 May 2005

Volume 86, Issue 19, Articles (19xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 86, 191102 (2005); http://dx.doi.org/10.1063/1.1922084 (3 pages)

Nir Dahan, Avi Niv, Gabriel Biener, Vladimir Kleiner, and Erez Hasman
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Broadband InGaAs tapered diode laser sources for optical coherence radar and coherence tomography

Oliver Casel, Harry Fuchs, Marc A. Tremont, Dirk Woll, and Richard Wallenstein

Appl. Phys. Lett. 86, 191101 (2005); http://dx.doi.org/10.1063/1.1925313 (3 pages) | Cited 1 time

Online Publication Date: 2 May 2005

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This letter reports on broadband laser sources based on InGaAs tapered diode laser amplifiers with external optical feedback. The generated 920 nm radiation with a bandwidth of up to 20 nm and a power of a few hundred milliwatts is emitted in an almost diffraction limited beam. Spectral filtering and subsequent amplification in a second tapered amplifier provides radiation with spectral widths in the range of 20 to 40 nm and optical output powers of up to 2.5 W.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
42.79.Qx Range finders, remote sensing devices; laser Doppler velocimeters, SAR, and LIDAR
87.63.L- Visual imaging
81.70.Fy Nondestructive testing: optical methods

Space-variant polarization manipulation of a thermal emission by a SiO2 subwavelength grating supporting surface phonon-polaritons

Nir Dahan, Avi Niv, Gabriel Biener, Vladimir Kleiner, and Erez Hasman

Appl. Phys. Lett. 86, 191102 (2005); http://dx.doi.org/10.1063/1.1922084 (3 pages) | Cited 16 times

Online Publication Date: 2 May 2005

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Space-variant polarization manipulation of enhanced nondirectional thermal emission in a narrow spectral peak is presented. The emission is attributed to surface phonon-polariton excitation from space-variant subwavelength SiO2 gratings. Polarization manipulation was obtained by discretely controlling the local orientation of the grating. We experimentally demonstrated thermal emission in an axially symmetric polarization distribution. Theoretical calculations based on rigorous coupled-wave analysis are presented along with experimental results.
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42.79.Dj Gratings
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
68.35.Ja Surface and interface dynamics and vibrations

High-detectivity InAs quantum-dot infrared photodetectors grown on InP by metal–organic chemical–vapor deposition

W. Zhang, H. Lim, M. Taguchi, S. Tsao, B. Movaghar, and M. Razeghi

Appl. Phys. Lett. 86, 191103 (2005); http://dx.doi.org/10.1063/1.1923176 (3 pages) | Cited 11 times

Online Publication Date: 2 May 2005

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We report a high-detectivity InAs quantum-dot infrared photodetector. The InAs quantum dots were grown by self-assembly on InP substrates via low-pressure metal–organic chemical–vapor deposition. Highly uniform quantum dots with a density of 4×1010 cm2 were grown on a GaAs/InP matrix. Photoresponse was observed at temperatures up to 160 K with a peak of 6.4 μm and cutoff of 6.6 μm. Very low dark currents and noise currents were obtained by inserting Al0.48In0.52As current blocking layers. The background-limited performance temperature was 100 K. A detectivity of 1.0×1010 cm Hz1/2/W was obtained at 77 K with a bias of −1.1 V.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
81.07.Ta Quantum dots
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Experimental characterization of the reflectance of 60° waveguide bends in photonic crystal waveguides

M. H. Shih, Woo Jun Kim, Wan Kuang, J. R. Cao, Sang-Jun Choi, John D. O’Brien, and P. Daniel Dapkus

Appl. Phys. Lett. 86, 191104 (2005); http://dx.doi.org/10.1063/1.1923169 (3 pages) | Cited 3 times

Online Publication Date: 3 May 2005

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Photonic crystal waveguides with two 60° bends were fabricated in an InGaAsP/InP suspended membrane geometry. The transmission spectrum was measured and the reflectance of the 60° bend was evaluated from Fabry–Perot oscillations using Fourier analysis. It is shown that the reflectance agrees well with the results of a finite element method simulation.
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42.70.Qs Photonic bandgap materials
42.55.Tv Photonic crystal lasers and coherent effects
81.16.Mk Laser-assisted deposition

Three-dimensional optical memory using photoluminescence change in Sm-doped sodium borate glass

Jinhyong Lim, Myeongkyu Lee, and Eunkyoung Kim

Appl. Phys. Lett. 86, 191105 (2005); http://dx.doi.org/10.1063/1.1926402 (3 pages) | Cited 14 times

Online Publication Date: 3 May 2005

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The feasibility of three-dimensional (3D) optical memory has been demonstrated by utilizing the photoluminescence (PL) spectrum change in a Sm-doped fluoride glass [ K. Miura, J. Qiu, S. Fujiwara, S. Sakasuchi, and K. Hirao, Appl. Phys. Lett. 80 2263 (2002) ]. We here report on a femtosecond laser-induced PL change in a Sm-doped sodium borate glass that is easier to synthesize and its potential application to 3D memory. Irradiation with a femtosecond pulsed laser (800 nm, 1 kHz, 100 fs) induced a PL peak near 682 nm, resulting from the photoreduction of the Sm ions. A multilayer pattern (bit size = 1 μm,layer separation = 8 μm) formed by femtosecond laser irradiation was read out by a reflection-type fluorescent confocal microscope, which detected the emission at 682 nm as a signal. High-contrast pattern images were obtained without crosstalk.
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42.79.Vb Optical storage systems, optical disks
42.70.Ce Glasses, quartz
78.55.Hx Other solid inorganic materials
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Characteristics of a tunneling quantum-dot infrared photodetector operating at room temperature

P. Bhattacharya, X. H. Su, S. Chakrabarti, G. Ariyawansa, and A. G. U. Perera

Appl. Phys. Lett. 86, 191106 (2005); http://dx.doi.org/10.1063/1.1923766 (3 pages) | Cited 77 times

Online Publication Date: 3 May 2005

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We report high-temperature (240–300 K) operation of a tunneling quantum-dot infrared photodetector. The device displays two-color characteristics with photoresponse peaks at ∼ 6 μm and 17 μm. The extremely low dark current density of 1.55 A/cm2 at 300 K for 1 V bias is made possible by the tunnel filter. For the 17 μm absorption, the measured peak responsivity is 0.16 A/W (300 K) for a bias of 2 V and the specific detectivity D* is 1.5×107 cm Hz1/2/W (280 K) for a bias of 1 V. Excellent performance characteristics are also measured for the 6 μm photoresponse.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)
85.30.-z Semiconductor devices

Optical add-drop multiplexers based on Si-wire waveguides

Hirohito Yamada, Tao Chu, Satomi Ishida, and Yasuhiko Arakawa

Appl. Phys. Lett. 86, 191107 (2005); http://dx.doi.org/10.1063/1.1924884 (3 pages) | Cited 9 times

Online Publication Date: 3 May 2005

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Ultrasmall optical add-drop multiplexers (OADMs) with Si-wire waveguides were demonstrated. Bragg grating reflectors based on Si-wire waveguides were developed and used as the wavelength-selective mechanism in the OADMs. The dropping wavelength bandwidth of the OADMs was less than 0.7 nm, and the dropping wavelengths could be controlled precisely by adjusting the grating period.
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42.79.Sz Optical communication systems, multiplexers, and demultiplexers
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.79.Gn Optical waveguides and couplers
42.79.Dj Gratings
42.79.Bh Lenses, prisms and mirrors

Calculation of the linewidth broadening in vertical-cavity surface-emitting lasers due to temperature fluctuations

Christian Lauer and Markus-Christian Amann

Appl. Phys. Lett. 86, 191108 (2005); http://dx.doi.org/10.1063/1.1924868 (3 pages) | Cited 3 times

Online Publication Date: 3 May 2005

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We investigate the broadening of the spectral linewidth of vertical-cavity surface-emitting lasers due to the temperature fluctuations occuring in the small resonator volume of these lasers. The present analysis is restricted to the direct impact of temperature changes on the emission wavelength via the temperature dependent refractive index of the semiconductor materials (thermorefractive effect). Our results indicate a significant contribution to the laser linewidth of up to ≈ 10 MHz for small devices. This broadening adds to the Schawlow–Townes–Henry linewidth and thus defines a minimal achievable spectral linewidth.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects

Observation of ultrahigh quality factor in a semiconductor microcavity

D. Sanvitto, A. Daraei, A. Tahraoui, M. Hopkinson, P. W. Fry, D. M. Whittaker, and M. S. Skolnick

Appl. Phys. Lett. 86, 191109 (2005); http://dx.doi.org/10.1063/1.1925774 (3 pages) | Cited 21 times

Online Publication Date: 4 May 2005

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Observation of a very high-quality factor (Q) of ∼ 30,000 is reported for a planar semiconductor microcavity grown by molecular-beam epitaxy using in situ optical monitoring. The very high Qs are measured in pillars of 5–10 μm diameter, and are approximately a factor of 3 higher than measured in planar structures before etching. The higher values in the pillars are ascribed to the elimination of the effects of in-plane dispersion, diffraction, and lateral inhomogeneities, thus allowing the intrinsic Q of the planar structure to be observed. Spectrally resolved mode mapping is reported, accounting qualitatively for the decrease of Q with increasing mode number in the pillars.
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85.30.De Semiconductor-device characterization, design, and modeling
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.65.Cf Surface cleaning, etching, patterning

Observation of soliton ridge states for the self-imprinting of fiber-slab couplers

Eugenio DelRe, Angelo D’Ercole, Elia Palange, and Aharon J. Agranat

Appl. Phys. Lett. 86, 191110 (2005); http://dx.doi.org/10.1063/1.1926401 (3 pages) | Cited 4 times

Online Publication Date: 4 May 2005

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We investigate experimentally the energy exchange patterns and consequent propagation dynamics of an extended hybrid-dimensional interaction between a one-dimensional and a two-dimensional spatial soliton in a biased photorefractive crystal. Results show that conditions can be found in which the coupling manifests propagation invariant features. The mechanism hinges on mutual distortion through spatially nonlocal components of response, as opposed to standard wave overlap, which would lead to a diffusion of the needle into the slab mode. These nonlocal-nonlinearity-driven ridge modes represent the instrument for writing fiber-slab couplers, the key to attaining soliton-based wavelength selectivity with electroactivated features.
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42.65.Tg Optical solitons; nonlinear guided waves
42.81.Qb Fiber waveguides, couplers, and arrays
42.70.Gi Light-sensitive materials
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials

Potential white-light long-lasting phosphor: Dy3+-doped aluminate

Bo Liu, Chaoshu Shi, and Zeming Qi

Appl. Phys. Lett. 86, 191111 (2005); http://dx.doi.org/10.1063/1.1925778 (3 pages) | Cited 34 times

Online Publication Date: 5 May 2005

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The white-light long-lasting phosphor CaAl2O4:Dy3+ was prepared and investigated. The white-light afterglow spectra under the irradiation of 254 or 365 nm are comprised of the blue light emission and the yellow light emission, originating from the transitions of math→math, math→math in the 4f9 configuration of Dy3+. The afterglow can last 32 min for the best sample with Dy-doped concentration of 2 at. %. The decay curve and the thermoluminescence curve show to be a second-order process. Thermoluminescence curves exhibit a complicated structure in the range of 230–450 K with the peaks at 244, 280, 310, and 346 K. The two thermoluminescence bands peaking above room temperature have corresponding traps with the depths of 0.54 and 0.61 eV, which are responsible for the afterglow emission at room temperature. This work provides a promising approach for the development of white-light long-lasting phosphor.
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78.60.Kn Thermoluminescence
78.40.Ha Other nonmetallic inorganics
61.72.S- Impurities in crystals
71.55.Ht Other nonmetals
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Ti Kα radiography of Cu-doped plastic microshell implosions via spherically bent crystal imaging

J. A. King, K. Akli, B. Zhang, R. R. Freeman, M. H. Key, C. D. Chen, S. P. Hatchett, J. A. Koch, A. J. MacKinnon, P. K. Patel, R. Snavely, R. P. J. Town, M. Borghesi, L. Romagnani, M. Zepf, et al.

Appl. Phys. Lett. 86, 191501 (2005); http://dx.doi.org/10.1063/1.1923178 (3 pages) | Cited 9 times

Online Publication Date: 3 May 2005

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We show that short pulse laser generated Ti Kα radiation can be used effectively as a backlighter for radiographic imaging. This method of x-ray radiography features high temporal and spatial resolution, high signal to noise ratio, and monochromatic imaging. We present here the Ti Kα backlit images of six-beam driven spherical implosions of thin-walled 500-μm Cu-doped deuterated plastic (CD) shells and of similar implosions with an included hollow gold cone. These radiographic results were used to define conditions for the diagnosis of fast ignition relevant electron transport within imploded Cu-doped coned CD shells.
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81.70.Ex Nondestructive testing: electromagnetic testing, eddy-current testing
78.47.-p Spectroscopy of solid state dynamics
07.85.-m X- and γ-ray instruments

Suppression of ionization instability in a magnetohydrodynamic plasma by coupling with a radio-frequency electromagnetic field

Tomoyuki Murakami, Yoshihiro Okuno, and Hiroyuki Yamasaki

Appl. Phys. Lett. 86, 191502 (2005); http://dx.doi.org/10.1063/1.1926410 (3 pages) | Cited 8 times

Online Publication Date: 4 May 2005

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We describe the suppression of ionization instability and the control of a magnetohydrodynamic electrical power-generating plasma by coupling with a radio-frequency (rf) electromagnetic field. The rf heating stabilizes the unstable plasma behavior and homogenizes the nonuniform plasma structure, whereby the power-generating performance is significantly improved.
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52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.75.Fk Magnetohydrodynamic generators and thermionic convertors; plasma diodes
52.50.Qt Plasma heating by radio-frequency fields; ICR, ICP, helicons
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.80.-s Electric discharges

Possible method for diagnosing waves in dusty plasmas with magnetized charged dust particulates

M. Rosenberg and P. K. Shukla

Appl. Phys. Lett. 86, 191503 (2005); http://dx.doi.org/10.1063/1.1923749 (3 pages) | Cited 3 times

Online Publication Date: 4 May 2005

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We discuss theoretically a possible method for diagnosing some features of dust wave behavior in a magnetized plasma containing small (tens of nm) charged dust grains whose motion is magnetized. It is easier to magnetize a small dust particle because its charge-to-mass ratio increases as its size decreases. However, it is more difficult to use the backscattering of light from the dust as a diagnostic as the dust size decreases below the diffraction limit. The idea proposed here is to measure the reduction in transmitted UV or optical light intensity due to enhanced extinction by small metal dust particles that have surface plasmon resonances at those wavelengths. Such measurements could indicate the spatial location of the dust density compressions or rarefactions, which may yield information on the dust wave behavior, or perhaps even charged dust transport. Parameters that may be relevant to possible laboratory dusty plasma experiments are discussed.
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52.27.Lw Dusty or complex plasmas; plasma crystals
52.25.Xz Magnetized plasmas
52.25.Fi Transport properties
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.35.-g Waves, oscillations, and instabilities in plasmas and intense beams

2.45 GHz microwave-excited atmospheric pressure air microplasmas based on microstrip technology

Jaeho Kim and Kazuo Terashima

Appl. Phys. Lett. 86, 191504 (2005); http://dx.doi.org/10.1063/1.1926411 (3 pages) | Cited 24 times

Online Publication Date: 5 May 2005

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A plasma system based on microstrip technology was developed for the generation of atmospheric pressure microplasmas. A discharge gap was placed between the striplines and the ground plane on the transverse cross section in the direction of microwave propagation. This microstrip structure permits the concentration of electric fields at the discharge gap, which is confirmed by a computer simulation using the three-dimensional simulation code based on the finite-difference time-domain method, and can produce atmospheric pressure plasmas even in air. The microplasmas were sustained in the discharge gap (width: 0.2 mm, length: 6 mm) at a microwave power of 1 W. The experimentally measured rotational temperature of nitrogen molecules was 800 K, indicating these plasmas to be nonthermal plasmas. This plasma system will provide a portable microplasma system utilizing a small semiconductor microwave source and a large-scale atmospheric pressure nonthermal plasma using the array configuration.
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52.50.Dg Plasma sources
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
52.40.Fd Plasma interactions with antennas; plasma-filled waveguides
52.80.-s Electric discharges
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.65.-y Plasma simulation
02.70.Bf Finite-difference methods

Rapid heating of solid density material by a petawatt laser

R. G. Evans, E. L. Clark, R. T. Eagleton, A. M. Dunne, R. D. Edwards, W. J. Garbett, T. J. Goldsack, S. James, C. C. Smith, B. R. Thomas, R. Clarke, D. J. Neely, and S. J. Rose

Appl. Phys. Lett. 86, 191505 (2005); http://dx.doi.org/10.1063/1.1920422 (3 pages) | Cited 27 times

Online Publication Date: 5 May 2005

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Time-resolved x-ray spectra from solid targets irradiated by the VULCAN Petawatt laser focused to 1020 W cm−2 show that material at solid density is heated to temperatures above 500 eV to a depth of about 15 μm and for a duration of more than 30 ps. Modeling with the implicit hybrid plasma code LSP shows that the heating is sensitive to the laser prepulse through resistive inhibition of the laser accelerated electrons in the blow off layer.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.70.La X-ray and γ-ray measurements
52.65.Ww Hybrid methods
52.38.Kd Laser-plasma acceleration of electrons and ions
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Geometrical criteria required for the determination of the epitaxial stress from the transmission electron microscopy curvature method

M. Cabié, A. Ponchet, A. Rocher, L. Durand, and A. Altibelli

Appl. Phys. Lett. 86, 191901 (2005); http://dx.doi.org/10.1063/1.1900306 (3 pages)

Online Publication Date: 2 May 2005

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The epitaxial stress of a Ga0.8In0.2As thin layer deposited on a GaAs substrate has been measured by the curvature method adapted to transmission electron microscopy. It is shown that even if the geometrical characteristics of the specimens thinned to be observed by transmission electron microscopy are very different from the ones of a thick sample, the conditions of validity of the model can still be verified. Finite element calculations have been performed to determine the geometry of the specimen answering to these conditions. Once these conditions are satisfied, the stress measured on a Ga0.8In0.2As layer is −1.30±0.13 GPa.
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81.05.Ea III-V semiconductors
68.60.Bs Mechanical and acoustical properties
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
68.55.-a Thin film structure and morphology
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
68.37.Lp Transmission electron microscopy (TEM)

Blue-purplish InGaN quantum wells with shallow depth of exciton localization

Tetsuya Akasaka, Hideki Gotoh, Hedetoshi Nakano, and Toshiki Makimoto

Appl. Phys. Lett. 86, 191902 (2005); http://dx.doi.org/10.1063/1.1925314 (3 pages) | Cited 9 times

Online Publication Date: 2 May 2005

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Temperature-dependent time-resolved PL measurements were performed for blue-purplish InGaN multiple quantum wells grown on various kinds of underlying layers (ULs). By using an InGaN UL, excitons recombined radiatively at low temperatures, being confined in the shallow potential minima (7.1 meV), while they radiatively recombined two-dimensionally with high luminescent efficiency at around room temperature, being delocalized thermally from the potential minima. Therefore, the exciton localization is not necessary in order to obtain high luminescent efficiency, but it is important to annihilate the nonradiative recombination centers by incorporation of indium atoms into ULs.
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73.21.Fg Quantum wells
78.55.Cr III-V semiconductors
71.35.-y Excitons and related phenomena
78.67.De Quantum wells

Accurate determination of atomic structure of multiwalled carbon nanotubes by nondestructive nanobeam electron diffraction

Zejian Liu, Qi Zhang, and Lu-Chang Qin

Appl. Phys. Lett. 86, 191903 (2005); http://dx.doi.org/10.1063/1.1923170 (3 pages) | Cited 17 times

Online Publication Date: 2 May 2005

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We report a method that allows direct, systematic, and accurate determination of the atomic structure of multiwalled carbon nanotubes by analyzing the scattering intensities on the nonequatorial layer lines in the electron diffraction pattern. Complete structure determination of a quadruple-walled carbon nanotube is described as an example, and it was found that the intertubular distance varied from 0.36 nm to 0.5 nm with a mean value of 0.42 nm.
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73.22.Dj Single particle states
61.05.jm Convergent-beam electron diffraction, selected-area electron diffraction, nanodiffraction

In situ investigation of growth and thermal stability of ultrathin Si layers on the HfO2/Si (100) high-κ dielectric system

Yu. Yu. Lebedinskii, A. Zenkevich, E. P. Gusev, and M. Gribelyuk

Appl. Phys. Lett. 86, 191904 (2005); http://dx.doi.org/10.1063/1.1923158 (3 pages) | Cited 10 times

Online Publication Date: 2 May 2005

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We report on growth behavior and thermal stability of ultrathin (0.5–12 nm) Si layers grown on HfO2 (3 nm)/Si (100) by pulsed laser deposition (PLD) as investigated by in situ x-ray photoelectron spectroscopy and low-energy ion scattering spectroscopy. Layer-by-layer growth of ultrathin Si overlayer was observed during room-temperature deposition, while an island-like growth behavior dominated at T ≥ 900 K. Vacuum annealing of the Si(3.5 nm)/HfO2 (3 nm)/Si (100) structure resulted in Si crystallization and coarsening. The process was accompanied by hafnium oxide reduction at the surface causing HfO2 layer decomposition and hafnium silicide formation. These interface reactions depended on the thickness of the Si cap layer—the thicker (12 nm) Si layer on HfO2 (40 nm)/Si (100) appeared to be stable at least up to T = 1200 K. An ultrathin (0.3 nm) Al2O3 layer PLD deposited between HfO2 and the Si overlayer also effectively inhibited the reactions up to T = 1200 K.
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81.05.Cy Elemental semiconductors
68.55.A- Nucleation and growth
68.60.Dv Thermal stability; thermal effects
68.35.Ct Interface structure and roughness
77.22.Ch Permittivity (dielectric function)
81.15.Fg Pulsed laser ablation deposition
61.72.Cc Kinetics of defect formation and annealing
79.60.Bm Clean metal, semiconductor, and insulator surfaces
64.70.K- Solid-solid transitions
64.75.-g Phase equilibria
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Thermodynamic stability of Ga2O3(Gd2O3)/GaAs interface

Y. L. Huang, P. Chang, Z. K. Yang, Y. J. Lee, H. Y. Lee, H. J. Liu, J. Kwo, J. P. Mannaerts, and M. Hong

Appl. Phys. Lett. 86, 191905 (2005); http://dx.doi.org/10.1063/1.1923172 (3 pages) | Cited 27 times

Online Publication Date: 2 May 2005

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Ga2O3(Gd2O3)/GaAs heterostructures have been annealed up to ∼ 780 °C. Studies using x-ray reflectivity and high-resolution transmission electron microscopy have shown that the samples annealed under ultrahigh vacuum have maintained smooth and abrupt interfaces with the interfacial roughness being less than 0.2 nm. The oxide remains amorphous, an important parameter for device consideration. Current–voltage and capacitance–voltage measurements have shown low leakage currents (10−8–10−9 A/cm2), a high dielectric constant of 15, and a low interfacial density of states (Dit) between gate dielectrics and GaAs. The attainment of a smooth interface between the gate dielectric and GaAs, even after high temperature annealing for activating implanted dopant, is a must to ensure the low (Dit) and to maintain a high carrier mobility in the channel of the metal–oxide–semiconductor field-effect transistor.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
72.20.Fr Low-field transport and mobility; piezoresistance
77.55.-g Dielectric thin films
73.20.At Surface states, band structure, electron density of states
68.35.Ct Interface structure and roughness
68.37.Lp Transmission electron microscopy (TEM)
77.22.Ch Permittivity (dielectric function)
65.40.G- Other thermodynamical quantities
61.72.Cc Kinetics of defect formation and annealing
61.43.Er Other amorphous solids

Strategy for pinpointing the best glass-forming alloys

D. Ma, H. Tan, D. Wang, Y. Li, and E. Ma

Appl. Phys. Lett. 86, 191906 (2005); http://dx.doi.org/10.1063/1.1922570 (3 pages) | Cited 35 times

Online Publication Date: 3 May 2005

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We present a model for the glass forming ability (GFA), based on phase selection of the glass over all the competing crystalline phases. Our analysis indicates that the best glass-forming zone can be either symmetric, or asymmetric, about the eutectic composition. Based on the model predictions we outline a microstructure-based strategy to pinpoint the off-eutectic composition with the optimum GFA. The practical implementation and significance of the strategy is demonstrated by discovering bulk metallic glasses in Zr–Cu and Zr–Cu–Al systems.
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81.30.Bx Phase diagrams of metals, alloys, and oxides
61.43.Fs Glasses
61.43.Dq Amorphous semiconductors, metals, and alloys

Optical properties of poly(di-n-hexylsilane)–zirconia hybrid thin films: suppression of thermochromism and large thermo-optic coefficients

Masahiro Marusaki, Hiroyoshi Naito, Yukihito Matsuura, and Kimihiro Matsukawa

Appl. Phys. Lett. 86, 191907 (2005); http://dx.doi.org/10.1063/1.1923196 (3 pages) | Cited 5 times

Online Publication Date: 3 May 2005

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Optical properties of hybrid thin films, poly(di-n-hexylsilane) (PDHS) dispersed in a zirconia matrix prepared by a sol–gel method, have been studied by means of optical absorption, photoluminescence and ellipsometry measurements. It is found that thermochromism of PDHS is suppressed in the PDHS–zirconia hybrid thin films, and that the refractive index of the hybrid, n, is continuously decreased with increasing temperature, T. The thermo-optic (TO) coefficient of the hybrids, dn/dT, is found to be −4×10−4 °C−1 and thus such a high value of dn/dT enables us to apply the hybrids to optical devices such as TO switches and optical deflectors.
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42.70.-a Optical materials
78.55.-m Photoluminescence, properties and materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects

Reduction of dislocations in GaN epilayers using templated three-dimensional coherent nanoislands

K. Jeganathan, M. Shimizu, and H. Okumura

Appl. Phys. Lett. 86, 191908 (2005); http://dx.doi.org/10.1063/1.1926419 (3 pages) | Cited 4 times

Online Publication Date: 3 May 2005

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Low-dislocation-density GaN layers have been grown on 6H–SiC(0001) substrates by molecular-beam epitaxy using high-density ( ∼ 4×1011 cm−2) self-assembled Stranski–Krastanov GaN nanoislands buffer. The density of dislocations determined from hot-wet chemical etching and atomic force microscopy show that the insertion of coherent nanoislands as a buffer reduces the defect migration from the interface to the GaN epitaxial layers. The dislocation density is dramatically dropped to ∼ 107 cm−2 in GaN layers grown on coherent nanoislands as compared to ∼ 109 cm−2 in the typical GaN layers grown on the AIN buffer.
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81.05.Ea III-V semiconductors
61.72.Lk Linear defects: dislocations, disclinations
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.65.Cf Surface cleaning, etching, patterning
68.55.A- Nucleation and growth
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.37.Ps Atomic force microscopy (AFM)
68.35.B- Structure of clean surfaces (and surface reconstruction)
66.30.Lw Diffusion of other defects

Dynamic polarization filtering in anisotropically strained M-plane GaN films

K. Omae, T. Flissikowski, P. Misra, O. Brandt, H. T. Grahn, K. Kojima, and Y. Kawakami

Appl. Phys. Lett. 86, 191909 (2005); http://dx.doi.org/10.1063/1.1927271 (3 pages) | Cited 9 times

Online Publication Date: 3 May 2005

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The dynamic optical polarization filtering for anisotropically strained M-plane GaN films on LiAlO2 is investigated by pump and probe spectroscopy. Due to a very large polarization anisotropy in the absorption coefficient, these films exhibit an intrinsic polarization filtering, which appears as a rotation of the polarization vector after transmission of linearly polarized light through the film. For dynamic filtering, the polarization rotation is controlled by the pump, since the photoexcited carriers remove the intrinsic linear dichroism by selective bleaching of the anisotropic absorption. The dynamic behavior of the polarization rotation is mainly determined by the redistribution of holes between the two uppermost valence bands and by the recombination time. The latter is comparable to the measured decay time of the dynamic rotation of about 15 ps. For M-plane GaN films, the maximum dynamic rotation reaches 35°, while the maximum static polarization rotation is about 40°.
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78.66.Fd III-V semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.20.Fm Birefringence
78.47.-p Spectroscopy of solid state dynamics
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
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