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27 Apr 2009

Volume 94, Issue 17, Articles (17xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 94, 172503 (2009); http://dx.doi.org/10.1063/1.3123290 (3 pages)

Kai He, David J. Smith, and Martha R. McCartney
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Scaling of light emitting transistor for multigigahertz optical bandwidth

C. H. Wu, G. Walter, H. W. Then, M. Feng, and N. Holonyak, Jr.

Appl. Phys. Lett. 94, 171101 (2009); http://dx.doi.org/10.1063/1.3126642 (3 pages) | Cited 8 times

Online Publication Date: 27 April 2009

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We report for an n-InGaP/p-AlGaAs/i-InGaAs-QW/n-GaAs heterojunction bipolar light emitting transistor (HBLET) the record spontaneous optical-signal bandwidth, at −3 dB, of 1.8–4.3 GHz (corresponding to an effective carrier recombination lifetime of 37 ps). Besides the improved circuit matching of three-terminal device operation, the extension in performance is achieved by the lateral reduction in the emitter aperture size DA from 13 to 5 μm to provide higher injection current densities and better confinement of the radiative recombination in the base region. By reducing the carrier loss to lateral extrinsic recombination, we obtain with HBLETs higher current gains β( = ΔIC/ΔIB>30) and simultaneously >4 GHz optical bandwidths.
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85.60.Dw Photodiodes; phototransistors; photoresistors
85.30.Pq Bipolar transistors

Multicolor photodetector based on GaAs quantum rings grown by droplet epitaxy

Jiang Wu, Zhenhua Li, Dali Shao, M. O. Manasreh, Vasyl P. Kunets, Zhiming M. Wang, Gregory J. Salamo, and B. D. Weaver

Appl. Phys. Lett. 94, 171102 (2009); http://dx.doi.org/10.1063/1.3126644 (3 pages) | Cited 16 times

Online Publication Date: 27 April 2009

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Photoresponse from multicolor photodetector was measured in the spectral range of 0.4–6.0 μm as a function of temperature and bias voltage. Devices were fabricated from wafers with an active region of five periods of GaAs quantum rings grown by droplet epitaxy technique on lattice matched Al0.3Ga0.7As barriers. The photoresponse spectra exhibit two broad bands in the visible-near-infrared and midinfrared spectral regions. The visible-near-infrared band, which is due to interband transitions, was observed at temperatures as high as room temperature. On the other hand, the midinfrared band, which is due to intersubband transitions, was observed at temperature lower than 80 K.
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85.60.Gz Photodetectors (including infrared and CCD detectors)

Spectral response design of hydrogenated amorphous silicon p-i-n diodes for ambient light sensing

S. S. Tan, C. Y. Liu, Yeu-Long Jiang, Der-Yu Lin, and Klaus Y. J. Hsu

Appl. Phys. Lett. 94, 171103 (2009); http://dx.doi.org/10.1063/1.3125250 (3 pages)

Online Publication Date: 28 April 2009

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For the applications involving ambient light sensing, the spectral response of photodetectors is required to mimic that of human eyes and the cost must be low. This paper discusses the layer structure design of human-eye-like hydrogenated amorphous silicon (a-Si:H) p-i-n photodiodes. The resultant sample devices are insensitive to infrared light and have a normal spectral response in the light band ranging between 400 nm wavelength and 740 nm wavelength. The spectrum peak locates around 560 nm wavelength, similar to the case of human eyes. The devices are suitable for low-cost ambient light sensing applications.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.30.Kk Junction diodes

Waveguide mode imaging and dispersion analysis with terahertz near-field microscopy

Oleg Mitrofanov, Thomas Tan, Paul R. Mark, Bradley Bowden, and James A. Harrington

Appl. Phys. Lett. 94, 171104 (2009); http://dx.doi.org/10.1063/1.3126053 (3 pages) | Cited 11 times

Online Publication Date: 28 April 2009

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Propagation of terahertz waves in hollow metallic waveguides depends on the waveguide mode. Near-field scanning probe terahertz microscopy is applied to identify the mode structure and composition in dielectric-lined hollow metallic waveguides. Spatial profiles, relative amplitudes, and group velocities of three main waveguide modes are experimentally measured and matched to the HE11, HE12, and TE11 modes. The combination of near-field microscopy with terahertz time-resolved spectroscopy opens the possibility of waveguide mode characterization in the terahertz band.
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84.40.Az Waveguides, transmission lines, striplines
41.20.Jb Electromagnetic wave propagation; radiowave propagation

Enhanced terahertz emission from coherent longitudinal optical phonons in a quantum well structure under applied bias

Kohji Mizoguchi, Yusuke Kanzawa, Shingo Saito, Kiyomi Sakai, and Masaaki Nakayama

Appl. Phys. Lett. 94, 171105 (2009); http://dx.doi.org/10.1063/1.3126446 (3 pages) | Cited 2 times

Online Publication Date: 28 April 2009

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We report on the characteristics of terahertz waves emitted from coherent longitudinal optical (LO) phonons in a GaAs/AlAs multiple quantum well structure under an applied electric field. It is found that the intensity of the terahertz wave from the coherent LO phonon is resonantly enhanced in comparison with the intensity in a low electric-field region, under the condition that an intersubband energy is tuned to the LO-phonon energy of GaAs. The pump-energy dependence of the terahertz-wave intensity indicates that the enhancement originates from the double resonances in the Raman scattering process.
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78.70.Gq Microwave and radio-frequency interactions
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
81.07.St Quantum wells
68.65.Fg Quantum wells
78.66.Fd III-V semiconductors
78.67.De Quantum wells

Surface-plasmon resonance of a planar lollipop near-field transducer

Chubing Peng

Appl. Phys. Lett. 94, 171106 (2009); http://dx.doi.org/10.1063/1.3126483 (3 pages) | Cited 2 times

Online Publication Date: 28 April 2009

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Surface-plasmon resonance of a lollipop near-field transducer integrated in a planar solid immersion mirror for heat-assisted magnetic recording has been studied by pump-probe photothermal measurement and recording on a phase-change medium. Lollipops of 190 nm in disk diameter and 20-nm-thick were found to exhibit two resonant modes in 710–950 nm. Recording on a phase-change medium showed that the wavelength at the short resonant mode is not sensitive to the presence of a medium, while the resonance at the long wavelength exhibits significant redshift. On resonance, the plasmon efficiency enables the pronounced near-field optical recording.
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42.79.Vb Optical storage systems, optical disks
85.70.Sq Magnetooptical devices
07.07.Mp Transducers
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Surface plasmon resonances of optical antenna atomic force microscope tips

Yanshu Zou, Paul Steinvurzel, Tian Yang, and Kenneth B. Crozier

Appl. Phys. Lett. 94, 171107 (2009); http://dx.doi.org/10.1063/1.3116145 (3 pages) | Cited 13 times

Online Publication Date: 29 April 2009

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A method for fabricating optical antennas on atomic force microscope probes using focused ion beam modification is described. We numerically demonstrate that these optical antenna probes provide a large near field intensity enhancement when illuminated at their resonant wavelengths. We experimentally measure the plasmon resonant wavelengths of probes with various lengths. Both simulation and experiment indicate that the resonant wavelength redshifts with increasing antenna length. We anticipate that the optical antenna tips could be used for mapping the field distributions of nanophotonic devices or for high spatial resolution spectroscopy.
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07.79.Lh Atomic force microscopes
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Experimental observation of mode-selective anticrossing in surface-plasmon-coupled metal nanoparticle arrays

Amitabh Ghoshal, Ivan Divliansky, and Pieter G. Kik

Appl. Phys. Lett. 94, 171108 (2009); http://dx.doi.org/10.1063/1.3122922 (3 pages) | Cited 10 times

Online Publication Date: 29 April 2009

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Surface plasmon excitation using resonant metal nanoparticles is studied experimentally. Geometry dependent reflection measurements reveal the existence of several optical resonances. Strong coupling of the in-plane nanoparticle plasmon resonance and propagating plasmons is evident from clear anticrossing behavior. Reflection measurements at high numerical aperture demonstrate the excitation of surface plasmons via out-of-plane particle polarization. The thus excited plasmons do not exhibit anticrossing in the considered frequency range. The results are explained in terms of the known surface plasmon dispersion relation and the anisotropic frequency dependent nanoparticle polarizability. These findings are important for applications utilizing surface-coupled nanoparticle plasmon resonances.
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73.22.Lp Collective excitations
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

The perfect absorber

E. F. C. Driessen and M. J. A. de Dood

Appl. Phys. Lett. 94, 171109 (2009); http://dx.doi.org/10.1063/1.3126062 (3 pages) | Cited 6 times

Online Publication Date: 29 April 2009

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We demonstrate that films of very lossy metal or dielectric, with a thickness of only a few nanometers, can absorb almost all incident radiation when illuminated from the substrate side at the critical angle for total internal reflection. The absorption for s-polarized light approaches 100%, while the absorption for p-polarized light vanishes. We demonstrate this effect by measuring the absorption as a function of the angle of incidence at a wavelength of 775 nm in a 4.5 nm thick NbN film with a dielectric constant ϵNbN = −8.2+31.4i. The measured absorption in this film reaches a maximum of 94%. We discuss the design of a near-unity efficiency single-photon detector for s-polarized light that has a broadband absorption coefficient of >90% for wavelengths from 700 to 1600 nm.
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77.55.-g Dielectric thin films
61.46.-w Structure of nanoscale materials
85.60.Gz Photodetectors (including infrared and CCD detectors)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
77.22.Ch Permittivity (dielectric function)

Parametric amplification in GaAs/AlOx waveguide

E. Guillotel, M. Ravaro, F. Ghiglieno, C. Langlois, C. Ricolleau, S. Ducci, I Favero, and G. Leo

Appl. Phys. Lett. 94, 171110 (2009); http://dx.doi.org/10.1063/1.3126482 (3 pages) | Cited 11 times

Online Publication Date: 29 April 2009

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We report the direct proof of parametric amplification in a semiconductor waveguide. Thanks to low propagation losses and high nonlinear efficiency, we amplified an input signal at 2 μm in a selectively oxidized GaAs/AlAs multilayer waveguide through the down conversion of a pump at 1 μm. The 4.5% single-pass gain measured for a 30 mW cw pump is compatible with parametric oscillation, provided that distributed and concentrated waveguide losses are further reduced.
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42.65.Lm Parametric down conversion and production of entangled photons
42.65.-k Nonlinear optics
42.65.Wi Nonlinear waveguides

Phase-matched emission of few high-harmonic orders from a helium gas cell

Sven Teichmann, Peter Hannaford, and Lap Van Dao

Appl. Phys. Lett. 94, 171111 (2009); http://dx.doi.org/10.1063/1.3127521 (3 pages) | Cited 4 times

Online Publication Date: 29 April 2009

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We report on femtosecond-laser-based generation of a few phase-matched high-order harmonics in a helium semi-infinite gas cell. The harmonic beam consists of effectively four to six intense orders with wavelengths around 9.5 nm. By varying the effective interaction length, we observe the effects of coherence length related to plasma formation and the Gouy phase shift on the output. The atomic scattering factors for photoabsorption, the effective propagation lengths (leff,He ≈ 1 mm, leff,Ar ≈ 7.2 mm), and the energy conversion efficiencies (εHe ≈ 10−7, εAr ≈ 5×10−7) are deduced for harmonic generation in helium (77th to 95th orders) and also argon (21st to 27th orders) for comparison.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
32.80.-t Photoionization and excitation
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Stimulated terahertz emission due to electronic Raman scattering in silicon

S. G. Pavlov, U. Böttger, J. N. Hovenier, N. V. Abrosimov, H. Riemann, R. Kh. Zhukavin, V. N. Shastin, B. Redlich, A. F. G. van der Meer, and H.-W. Hübers

Appl. Phys. Lett. 94, 171112 (2009); http://dx.doi.org/10.1063/1.3119662 (3 pages) | Cited 4 times

Online Publication Date: 30 April 2009

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Stimulated Raman emission in the terahertz frequency range (4.8–5.1 THz and 5.9–6.5 THz) has been realized by optical excitation of arsenic donor centers in silicon at low temperatures. The Stokes shift of the observed laser emission is 5.42 THz which is equal to the Raman-active donor electronic transition between the ground 1s(A1) and the excited 1s(E) arsenic states. Optical thresholds of the Raman laser are similar to those observed for other silicon donor lasers. In addition, intracenter donor lasing has been observed when pumping on the dipole-forbidden 1s(A1)→2s transition.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.55.Ye Raman lasers
71.55.Cn Elemental semiconductors

A simple cross-correlation technique between infrared and hard x-ray pulses

Bertold Krässig, R. W. Dunford, E. P. Kanter, E. C. Landahl, S. H. Southworth, and L. Young

Appl. Phys. Lett. 94, 171113 (2009); http://dx.doi.org/10.1063/1.3125256 (3 pages) | Cited 4 times

Online Publication Date: 30 April 2009

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We report a gas phase technique to establish the temporal overlap of ultrafast infrared laser and hard x-ray pulses. We use tunnel ionization of a closed shell atom in the strong field at the focus of an infrared laser beam to open a distinct x-ray absorption resonance channel with a clear fluorescence signature. The technique has an intrinsic response of a few femtoseconds and is nondestructive to the two beams. It provides a step-functionlike cross-correlation result. The details of the transient provide a diagnostic of the temporal overlap of the two pulses.
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32.80.-t Photoionization and excitation
07.85.-m X- and γ-ray instruments
32.30.Rj X-ray spectra
32.50.+d Fluorescence, phosphorescence (including quenching)
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Nanopatterning by solid-state dewetting on reconstructed ceramic surfaces

Joysurya Basu, C. Barry Carter, R. Divakar, B. Mukherjee, and N. Ravishankar

Appl. Phys. Lett. 94, 171114 (2009); http://dx.doi.org/10.1063/1.3127442 (3 pages) | Cited 10 times

Online Publication Date: 30 April 2009

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We demonstrate ordered array formation of Au nanoparticles by controlled solid-state dewetting of a metal film on stepped alumina substrates. In situ transmission electron microscopy studies reveal that the dewetting process starts with nucleation of ordered dry regions on the substrate. The chemical potential difference between concave and convex surface regions induces anisotropic metal diffusion leading to the formation of nanowires in the valleys. The nanowires fragment due to Rayleigh instability forming arrays of metal nanoparticles on the substrate. The length scale of reconstruction relative to the starting film thickness is an important parameter in controlling the spatial order of the nanoparticles.
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81.16.Rf Micro- and nanoscale pattern formation
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
66.30.Fq Self-diffusion in metals, semimetals, and alloys

Demonstration of high-Q (>8600) three-dimensional photonic crystal nanocavity embedding quantum dots

A. Tandaechanurat, S. Ishida, K. Aoki, D. Guimard, M. Nomura, S. Iwamoto, and Y. Arakawa

Appl. Phys. Lett. 94, 171115 (2009); http://dx.doi.org/10.1063/1.3127523 (3 pages) | Cited 11 times

Online Publication Date: 1 May 2009

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The authors report on an experimental demonstration of coupling of quantum dots with a point-defect nanocavity in woodpile three-dimensional (3D) photonic crystal (PhC) with the highest quality (Q) factor among those for 3D PhC cavities. The Q factor of more than 8600 was achieved by stacking 25 layers using a micromanipulation technique. The size of the square-shaped defect cavity was optimized to tune the cavity mode to the midgap frequency of the complete photonic bandgap to achieve high Q.
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42.86.+b Optical workshop techniques
81.07.Bc Nanocrystalline materials
81.07.Ta Quantum dots
42.70.Qs Photonic bandgap materials
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.67.Hc Quantum dots

Optical isolation based on nonreciprocal phase shift induced by interband photonic transitions

Zongfu Yu and Shanhui Fan

Appl. Phys. Lett. 94, 171116 (2009); http://dx.doi.org/10.1063/1.3127531 (3 pages) | Cited 10 times

Online Publication Date: 1 May 2009

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Photonic transitions in waveguides can create nonreciprocal phase response for counterpropagating modes. Such effect can be used in Mach–Zehnder interferometers to form optical isolators and circulators. Performance of such device is analyzed using coupled mode theory given the experimentally available modulation in silicon. The proposed scheme can provide a broadband (>0.8 THz), high contrast ratio (>20 dB) optical isolation at telecommunication wavelength.
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42.79.Gn Optical waveguides and couplers
07.60.Ly Interferometers

Growth of AlGaN/GaN/AlGaN double heterojunction field-effect transistors and the observation of a compositional pulling effect

Z. Chen, Y. Pei, S. Newman, D. Brown, R. Chung, S. Keller, S. P. DenBaars, S. Nakamura, and U. K. Mishra

Appl. Phys. Lett. 94, 171117 (2009); http://dx.doi.org/10.1063/1.3129865 (3 pages) | Cited 6 times

Online Publication Date: 1 May 2009

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Field-effect transistors (FETs) were grown on both GaN and AlGaN buffers. X-ray reciprocal space mapping and ω-2θ scans showed that the AlGaN barriers grown on these two buffers had different Al compositions and growth rates, which was attributed to the compositional pulling effect. AlGaN/GaN/AlGaN double heterojunction FETs exhibited lower output conductance and better pinch-off due to the improved electron confinement resulting from the increase in the effective back-side barrier height. Thus, this device is promising for highly scaled transistors. This device also demonstrated a state-of-the-art power added efficiency of 53.5% and an associated power gain of 9.1 dB at a drain bias of 20 V at 30 GHz.
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85.30.Tv Field effect devices
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Absolute vacuum ultraviolet flux in inductively coupled plasmas and chemical modifications of 193 nm photoresist

M. J. Titus, D. Nest, and D. B. Graves

Appl. Phys. Lett. 94, 171501 (2009); http://dx.doi.org/10.1063/1.3125260 (3 pages) | Cited 12 times

Online Publication Date: 27 April 2009

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Vacuum ultraviolet (VUV) photons in plasma processing systems are known to alter surface chemistry and may damage gate dielectrics and photoresist. We characterize absolute VUV fluxes to surfaces exposed in an inductively coupled argon plasma, 1–50 mTorr, 25–400 W, using a calibrated VUV spectrometer. We also demonstrate an alternative method to estimate VUV fluence in an inductively coupled plasma (ICP) reactor using a chemical dosimeter-type monitor. We illustrate the technique with argon ICP and xenon lamp exposure experiments, comparing direct VUV measurements with measured chemical changes in 193 nm photoresist-covered Si wafers following VUV exposure.
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85.40.Hp Lithography, masks and pattern transfer
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
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Electric discharge caused by expanding armatures in flux compression generators

Sergey I. Shkuratov, Jason Baird, Evgueni F. Talantsev, and Larry L. Altgilbers

Appl. Phys. Lett. 94, 171502 (2009); http://dx.doi.org/10.1063/1.3127525 (3 pages) | Cited 3 times

Online Publication Date: 30 April 2009

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In this letter, we experimentally demonstrate that explosively driven expansion of metallic armature of the magnetic flux compression generator (FCG) plays a dominant role in the formation of plasma and electric discharge initiation inside the FCG.
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89.20.Kk Engineering
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables
52.80.-s Electric discharges
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Corner liquid imbibition during capillary penetration in lithographically made microchannels

S. Girardo, R. Cingolani, S. Chibbaro, F. Diotallevi, S. Succi, and D. Pisignano

Appl. Phys. Lett. 94, 171901 (2009); http://dx.doi.org/10.1063/1.3123804 (3 pages) | Cited 3 times

Online Publication Date: 27 April 2009

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The authors investigate the formation of liquid layers at corners of lithographically made microchannels during capillary filling. The microflow and shape of the liquid-air interface is studied through an optically transparent microfluidic device. The experimental findings at early stages of layer formation are supported by three-dimensional lattice Boltzmann simulations, allowing to predict the shape and dynamics of the corner films and highlighting their dependence on the fluid contact angle.
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47.61.-k Micro- and nano- scale flow phenomena
68.15.+e Liquid thin films
68.03.Cd Surface tension and related phenomena
47.11.Qr Lattice gas
47.85.Np Fluidics
47.60.Dx Flows in ducts and channels

Atomic displacement parameters and structural disorder of oxygen ions in the CexZr1−xO2 solid solutions (0.12 ≤ x ≤ 1.0): Possible factors of high catalytic activity of ceria-zirconia catalysts

Masatomo Yashima and Takahiro Wakita

Appl. Phys. Lett. 94, 171902 (2009); http://dx.doi.org/10.1063/1.3124244 (3 pages) | Cited 5 times

Online Publication Date: 27 April 2009

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Crystal structures and electron-density distributions of ceria-zirconia CexZr1−xO2 compounds have been studied by the maximum-entropy method (MEM) and MEM-based pattern fitting combined with the Rietveld method using high-angular-resolution synchrotron x-ray powder diffraction data. The isotropic atomic displacement parameter of the oxygen atoms U(O) in Ce0.5Zr0.5O2 has a maximum value in CexZr1−xO2 (0.12 ≤ x ≤ 1.0). Electron-density distribution of Ce0.5Zr0.5O2 shows a large spatial distribution of the oxygen ions. The greater U(O) and large spatial distribution of oxygen ions in Ce0.5Zr0.5O2 are possible factors of its higher catalytic activity.
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61.66.Fn Inorganic compounds
65.40.gd Entropy
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
71.20.Ps Other inorganic compounds

Study of a nitrogen-doped ZnO film with synchrotron radiation

C. W. Zou, X. D. Yan, J. Han, R. Q. Chen, W. Gao, and J. Metson

Appl. Phys. Lett. 94, 171903 (2009); http://dx.doi.org/10.1063/1.3125255 (3 pages) | Cited 6 times

Online Publication Date: 27 April 2009

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X-ray absorption near-edge spectroscopy (XANES) and photoelectron spectroscopy (PES) with synchrotron radiation have been applied to investigate the structure and chemical states of nitrogen atoms in ZnO:N films with different annealing temperatures. The high-resolution XANES and PES spectra of N 1s reveal the chemical states of N dopants and give a direct observation of nitrogen location in the ZnO films. The results indicate that only the nitrogen atoms incorporated substitutionally at O sites act as acceptors, and contribute to the p-type characteristic of the ZnO:N film.
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68.55.-a Thin film structure and morphology
78.70.Dm X-ray absorption spectra
79.60.Dp Adsorbed layers and thin films
61.72.Cc Kinetics of defect formation and annealing
61.72.uj III-V and II-VI semiconductors

Nanocrystallization mechanism of amorphous Fe78B13Si9

K. Sato, H. Murakami, W. Sprengel, H.-E. Schaefer, and Y. Kobayashi

Appl. Phys. Lett. 94, 171904 (2009); http://dx.doi.org/10.1063/1.3126041 (3 pages) | Cited 4 times

Online Publication Date: 27 April 2009

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The nanocrystallization mechanism of an amorphous alloy is discussed based on the kinetics of open nanospaces in Fe78B13Si9. There already exists a high concentration of Fe-enriched fluctuated sites with open nanospaces in the amorphous matrix. The structural and compositional fluctuation helps transient short-range Fe diffusion in the metastable amorphous matrix with an increase of temperature, triggering highly concentrated α-Fe nucleation. Along with the growth of α-Fe nucleus, Fe atoms are transferred from the intergranular amorphous phase to Fe-based nanocrystallites. The nanocrystallization of α-Fe is achieved through nucleation by short-range Fe diffusion and its growth by nanovoid-mediated long-range Fe diffusion.
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64.70.kd Metals and alloys
66.30.Pa Diffusion in nanoscale solids
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
66.30.Fq Self-diffusion in metals, semimetals, and alloys
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
75.50.Kj Amorphous and quasicrystalline magnetic materials
61.43.Fs Glasses

Geometric effects on dislocation nucleation in strained electronics

T. L. Li, J. H. Lee, Y. F. Gao, G. M. Pharr, M. Huang, and T. Y. Tsui

Appl. Phys. Lett. 94, 171905 (2009); http://dx.doi.org/10.1063/1.3126520 (3 pages) | Cited 3 times

Online Publication Date: 27 April 2009

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Dislocation loops may be nucleated from sharp geometric features in strained micro- and nano-electronic devices. This process is investigated by a dissipative cohesive interface model which treats the dislocation core as a continuous, inhomogeneous lattice slip field. As a representative example, we calculate the critical external stress for dislocation nucleation from the edges/corners of a rectangular stress-free Si3N4 pad on a Si substrate as a function of geometric parameters such as the length-to-height ratio and the three-dimensional shape of the pad. The shapes of the dislocations are also simulated.
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61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
85.35.-p Nanoelectronic devices

Room temperature free carrier tunneling in dilute nitride based quantum well - quantum dot tunnel injection system for 1.3 μm

W. Rudno-Rudziński, G. Sęk, K. Ryczko, M. Syperek, J. Misiewicz, E. S. Semenova, A. Lemaitre, and A. Ramdane

Appl. Phys. Lett. 94, 171906 (2009); http://dx.doi.org/10.1063/1.3122935 (3 pages) | Cited 7 times

Online Publication Date: 28 April 2009

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We present optical studies of quantum dot tunnel injection structures for 1.3 μm emission with an InGaAsN quantum well injector. Photoreflectance spectroscopy supported by effective mass calculations within the band anticrossing model has been used to identify the optical transitions. Based on that, an evidence of the tunneling from the injector well to the dots could be detected by photoluminescence excitation up to the free carrier regime at room temperature. The latter finds confirmation in shortened photoluminescence rise times, when compared to the injector-free quantum dot reference structure.
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73.40.Gk Tunneling
81.07.St Quantum wells
81.07.Ta Quantum dots
81.05.Ea III-V semiconductors
78.55.Cr III-V semiconductors
78.67.De Quantum wells
78.67.Hc Quantum dots
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