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5 Mar 2007

Volume 90, Issue 10, Articles (10xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 90, 101901 (2007); http://dx.doi.org/10.1063/1.2712772 (3 pages)

S. N. Yi, Jong H. Na, Kwan H. Lee, Anas F. Jarjour, Robert A. Taylor, Y. S. Park, T. W. Kang, S. Kim, D. H. Ha, G. Andrew, and D. Briggs
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Integrated liquid core waveguides for nonlinear optics

Patrick Dumais, Claire L. Callender, Julian P. Noad, and Christopher J. Ledderhof

Appl. Phys. Lett. 90, 101101 (2007); http://dx.doi.org/10.1063/1.2711287 (3 pages) | Cited 2 times

Online Publication Date: 5 March 2007

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A liquid core waveguide monolithically integrated with silica waveguides is demonstrated as a nonlinear optical device. Continuum generation is achieved using toluene as a core medium, with picosecond pulses at 1550 nm wavelength. A 500 nm wide spectrum is generated for an estimated peak input power of 60 kW over a propagation length of 16 mm.
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42.79.Gn Optical waveguides and couplers
42.65.Wi Nonlinear waveguides
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.82.Et Waveguides, couplers, and arrays

Temperature dependence of pulse duration in a mode-locked quantum-dot laser

M. A. Cataluna, E. A. Viktorov, Paul Mandel, W. Sibbett, D. A. Livshits, J. Weimert, A. R. Kovsh, and E. U. Rafailov

Appl. Phys. Lett. 90, 101102 (2007); http://dx.doi.org/10.1063/1.2711291 (3 pages) | Cited 10 times

Online Publication Date: 5 March 2007

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The authors demonstrate, experimentally and theoretically, that in a mode-locked two-section quantum-dot laser, the pulse duration decreases with temperature. The primary cause is the increase of carrier capture/escape rates with temperature that leads to faster absorption recovery.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Fc Modulation, tuning, and mode locking

Fiber-microsphere laser with a submicrometer sol-gel silica glass layer codoped with erbium, aluminum, and phosphorus

Hideaki Takashima, Hideki Fujiwara, Shigeki Takeuchi, Keiji Sasaki, and Masahide Takahashi

Appl. Phys. Lett. 90, 101103 (2007); http://dx.doi.org/10.1063/1.2711384 (3 pages) | Cited 8 times

Online Publication Date: 5 March 2007

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Lasing of a taper-microsphere system with a gain layer of submicrometer thickness is demonstrated. For the gain layer, an Er3+-doped P2O5–Al2O3–SiO2 thin film with a thickness of 200 nm was fabricated using the sol-gel method on a silica microsphere. The demonstration of single-mode lasing with the thin gain layer suggests the improved dispersion of Er ions in the P codoped gain layer.
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42.55.Wd Fiber lasers
42.60.By Design of specific laser systems
42.70.Ce Glasses, quartz

Dual-mode switching of a liquid crystal panel for viewing angle control

Jong-In Baek, Yong-Hoan Kwon, Jae Chang Kim, and Tae-Hoon Yoon

Appl. Phys. Lett. 90, 101104 (2007); http://dx.doi.org/10.1063/1.2711386 (3 pages) | Cited 17 times

Online Publication Date: 5 March 2007

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The authors propose a method to control the viewing angle of a liquid crystal (LC) panel using dual-mode switching. To realize both wide viewing angle (WVA) characteristics and narrow viewing angle (NVA) characteristics with a single LC panel, the authors use two different dark states. The LC layer can be aligned homogeneously parallel to the transmission axis of the bottom polarizer for WVA dark state operation, while it can be aligned vertically for NVA dark state operation. The authors demonstrated that viewing angle control can be achieved with a single panel without any loss of contrast at the front.
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42.79.Kr Display devices, liquid-crystal devices
85.60.Pg Display systems

Integrated thin film photodetectors with vertically coupled microring resonators for chip scale spectral analysis

Sang-Yeon Cho and Nan Marie Jokerst

Appl. Phys. Lett. 90, 101105 (2007); http://dx.doi.org/10.1063/1.2711524 (3 pages) | Cited 7 times

Online Publication Date: 5 March 2007

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An integrated spectral analysis system using a thin film InGaAs metal-semiconductor-metal photodetector integrated with a vertically coupled polymer microring resonator was demonstrated for chip scale implementation. The integrated spectral analysis system has an excellent selectivity in measured spectral response as well as low dark current (3.2 nA). The measured full width half maximum of the spectral photoresponse at 5 V was 0.5 nm.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
42.82.Gw Other integrated-optical elements and systems

Simultaneous detection and identification of multigas pollutants using filament-induced nonlinear spectroscopy

H. L. Xu, Y. Kamali, C. Marceau, P. T. Simard, W. Liu, J. Bernhardt, G. Méjean, P. Mathieu, G. Roy, J.-R. Simard, and S. L. Chin

Appl. Phys. Lett. 90, 101106 (2007); http://dx.doi.org/10.1063/1.2711537 (3 pages) | Cited 10 times

Online Publication Date: 5 March 2007

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The authors report on an approach for simultaneous monitoring of multigas pollutants based on fluorescence emission of trace gases, induced by the filamentation of intense femtosecond laser pulses in air. The high intensity inside a filament can dissociate the gas molecules into small fragments which emit characteristic fluorescence. This method is illustrated for simultaneously sensing atmospheric trace gases, methane and acetylene. The spectra of an “unknown” mixture were analyzed by using a genetic algorithm, showing good concentration agreement with the experimental results within an error of 25%.
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82.33.Tb Atmospheric chemistry
92.60.Sz Air quality and air pollution

Influence of doping on the performance of terahertz quantum-cascade lasers

A. Benz, G. Fasching, A. M. Andrews, M. Martl, K. Unterrainer, T. Roch, W. Schrenk, S. Golka, and G. Strasser

Appl. Phys. Lett. 90, 101107 (2007); http://dx.doi.org/10.1063/1.2711710 (3 pages) | Cited 27 times

Online Publication Date: 5 March 2007

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The authors present the effects of the doping concentration on the performance of a set of terahertz quantum-cascade lasers emitting around 2.75 THz. The chosen design is based on the longitudinal-optical-phonon depopulation of the lower laser state. An identical structure is regrown varying the sheet density from 5.4×109 to 1.9×1010 cm−2. A linear dependency of the threshold current density on the doping is observed. The applied field where lasing takes place is independent of the doping. The field is responsible for the alignment of the cascades and therefore the transport of the electrons through the structure.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Strongly reduced exciton transfer between parallel quantum wires

K. F. Karlsson, H. Weman, K. Leifer, A. Rudra, E. Kapon, and S. K. Lyo

Appl. Phys. Lett. 90, 101108 (2007); http://dx.doi.org/10.1063/1.2711757 (3 pages) | Cited 3 times

Online Publication Date: 5 March 2007

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Exciton transfer between two parallel GaAs V-groove quantum wires or two planar quantum wells separated by AlGaAs barriers ranging from 5.5 nm to 20 nm thickness is studied by photoluminescence and photoluminescence excitation spectroscopy. It is found that the transfer is strongly reduced between the widely spaced quantum wires as compared with quantum wells. This observation is supported by model calculations, which yield strong dimensionality dependence of the photon-exchange transfer.
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73.21.Hb Quantum wires
73.21.Fg Quantum wells
71.35.-y Excitons and related phenomena
78.67.Lt Quantum wires
78.67.De Quantum wells
78.55.Cr III-V semiconductors

Hemispherical semi-insulating GaAs double-frequency absorption photodetector operating at 1.3 μm wavelength

Xiuhuan Liu, Bao Shi, Gang Jia, Zhanguo Chen, Ce Ren, Yuhong Zhang, Kun Cao, and Jianxun Zhao

Appl. Phys. Lett. 90, 101109 (2007); http://dx.doi.org/10.1063/1.2711760 (3 pages) | Cited 5 times

Online Publication Date: 5 March 2007

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The hemispherical semi-insulating GaAs photodetector operating at 1.3 μm is presented. The GaAs hemisphere was used both as a detector and a solid immersion lens to improve the responsivity. The physical mechanism of the detector is attributed to double-frequency absorption (DFA) confirmed by the measured photocurrent quadratically dependent on the incident optical power and nonlinearly dependent on the bias and by the relationship between the photocurrent and the azimuth in agreement with the anisotropy of DFA in GaAs single crystal.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
42.79.Bh Lenses, prisms and mirrors

Constriction-limited detection efficiency of superconducting nanowire single-photon detectors

Andrew J. Kerman, Eric A. Dauler, Joel K. W. Yang, Kristine M. Rosfjord, Vikas Anant, Karl K. Berggren, Gregory N. Gol’tsman, and Boris M. Voronov

Appl. Phys. Lett. 90, 101110 (2007); http://dx.doi.org/10.1063/1.2696926 (3 pages) | Cited 61 times

Online Publication Date: 5 March 2007

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We investigate the source of the large variations in the observed detection efficiencies of superconducting nanowire single-photon detectors between many nominally identical devices. Through both electrical and optical measurements, we infer that these variations arise from “constrictions:” highly localized regions of the nanowires where the effective cross-sectional area for superconducting current is reduced. These constrictions limit the bias-current density to well below its critical value over the remainder of the wire, and thus prevent the detection efficiency from reaching the high values that occur in these devices when they are biased near the critical current density.
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85.25.Pb Superconducting infrared, submillimeter and millimeter wave detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)

Analysis of spatial coherence of organic light-emitting devices through investigation of interference effects observed in top-emitting devices

Duncan Hill, Karl Leo, Gufeng He, and Qiang Huang

Appl. Phys. Lett. 90, 101111 (2007); http://dx.doi.org/10.1063/1.2709520 (3 pages) | Cited 3 times

Online Publication Date: 6 March 2007

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Interference effects in top-emitting organic light-emitting diodes (OLEDs) containing an air gap of 15 μm are studied over a range of angles in order to obtain information about the spatial coherence properties. The devices display effects similar to a Fabry-Pérot Étalon illuminated by a source with a broad spectral range, but the interference effects diminish rapidly with angle, which is inexplicable with simple thin film optics. The results suggest that this effect is due to the spatial coherence of the OLED. From an analysis of the interference pattern a number of device parameters can also be determined.
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85.60.Jb Light-emitting devices

Switchable AlxGa1−xAs all-optical delay line at 1.55 μm

A. D. Bristow, R. Iyer, J. S. Aitchison, H. M. van Driel, and Arthur L. Smirl

Appl. Phys. Lett. 90, 101112 (2007); http://dx.doi.org/10.1063/1.2679838 (3 pages) | Cited 4 times

Online Publication Date: 7 March 2007

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The authors demonstrate an on-chip optical delay in AlxGa1−xAs that operates at room temperature and 1.55 μm. A nonlinear directional coupler for optical switching and a 188 ps long racetrack structure provide bit delays of >100 for picosecond pulses. In the linear regime the transmission ratio of the slow channel is 74%, which reduces to 40% with increasing peak intensity. (Meanwhile, the fast channel output increases from 26% to 60%.) Switching occurs due to a nonlinear detuning of the directional coupler, limited by three-photon absorption and time-averaging effects. This proof-of-principle device can operate at up to 5 GHz and is promising for optical buffering applications.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.82.Et Waveguides, couplers, and arrays

Phase delay and group velocity determination at a planar defect state in three dimensional photonic crystals

J. F. Galisteo-López, M. Galli, L. C. Andreani, A. Mihi, R. Pozas, M. Ocaña, and H. Míguez

Appl. Phys. Lett. 90, 101113 (2007); http://dx.doi.org/10.1063/1.2710772 (3 pages) | Cited 9 times

Online Publication Date: 8 March 2007

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Phase sensitive optical transmission measurements have been performed on three dimensional opal-based photonic crystals containing a planar defect. From numerical derivation of the measured phase, the group velocity has been retrieved. Strong modulations in the group velocity are seen to correlate with a recovery in the transmission inside the forbidden spectral interval, demonstrating the presence of a localized defect state. Accordingly, the phase change measured across the forbidden interval doubles in the lattice containing a planar defect with respect to the defect-free crystal, as expected when introducing a localized state inside the pseudogap. All results have been modeled with a scalar wave approximation in a two band model including extinction.
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42.70.Qs Photonic bandgap materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.55.-i Impurity and defect levels

Room temperature emission from CdSe/ZnSSe/MgS single quantum dots

R. Arians, T. Kümmell, G. Bacher, A. Gust, C. Kruse, and D. Hommel

Appl. Phys. Lett. 90, 101114 (2007); http://dx.doi.org/10.1063/1.2710787 (3 pages) | Cited 22 times

Online Publication Date: 8 March 2007

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The authors report on room temperature photoluminescence from single CdSe quantum dots. The quantum dots, realized by self-organized epitaxial growth, are embedded in ZnSSe/MgS barriers. The integrated intensity of the emission drops by less than a factor of 3 between 4 K and room temperature. Microphotoluminescence with a spatial resolution of 200 nm exhibits single dot emission that remains visible up to 300 K. The linewidth of the single dot emission increases thereby from 340 μeV to 25 meV at room temperature, which the authors attribute to the interaction of excitons with optical phonons.
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78.67.Hc Quantum dots
78.55.Et II-VI semiconductors
71.35.-y Excitons and related phenomena
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

Fabrication and characterization of microcavity lasers in rhodamine B doped SU8 using high energy proton beam

S. Venugopal Rao, A. A. Bettiol, K. C. Vishnubhatla, S. N. B. Bhaktha, D. Narayana Rao, and F. Watt

Appl. Phys. Lett. 90, 101115 (2007); http://dx.doi.org/10.1063/1.2711777 (3 pages) | Cited 4 times

Online Publication Date: 8 March 2007

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The authors present their results on the characterization of individual dye-doped microcavity polymer lasers fabricated using a high energy proton beam. The lasers were fabricated in rhodamine B doped SU8 resist with a single exposure step followed by chemical processing. The resulting trapezoidal shaped cavities had dimensions of ∼ 250×250 μm2. Physical characterization of these structures was performed using a scanning electron microscope while the optical characterization was carried out by recording the emission subsequent to pumping the lasers with 532 nm, 6 nanosecond pulses. The authors observed intense, narrow emission near 624 nm with the best emission linewidth full width at half maximum of ∼ 9 nm and a threshold ∼ 150 μJ/mm2.
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42.55.Sa Microcavity and microdisk lasers
42.55.Mv Dye lasers
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.82.Cr Fabrication techniques; lithography, pattern transfer
85.60.Bt Optoelectronic device characterization, design, and modeling

Influence of quantum-well-barrier composition on gain and threshold current in AlGaN lasers

W. W. Chow, M. Kneissl, J. E. Northrup, and N. M. Johnson

Appl. Phys. Lett. 90, 101116 (2007); http://dx.doi.org/10.1063/1.2679969 (3 pages) | Cited 15 times

Online Publication Date: 9 March 2007

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In an AlGaN quantum-well laser, the presence of Al affects the optical properties of the gain-generating active region partly because of the distinct difference in the band structure between AlN and GaN or InN. The intricate connection between band structure and internal-electric-field effects leads to a noticeably stronger influence of barrier composition on optical gain, lasing polarization, and threshold current than in conventional near-infrared III-V lasers.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Nanostructured vanadium dioxide thin films with low phase transition temperature

Sihai Chen, Hong Ma, Jun Dai, and Xinjian Yi

Appl. Phys. Lett. 90, 101117 (2007); http://dx.doi.org/10.1063/1.2712427 (3 pages) | Cited 14 times

Online Publication Date: 9 March 2007

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A low phase turning temperature of 35 °C has been observed in the semiconductor-to-metal transition of nanoscale vanadium dioxide (VO2) thin films. The thin films are prepared by reactive ion beam sputtering deposition and subsequent thermal annealing. Both scanning electron microscopy and transmission electron microscopy measurements show that the grain size of the fabricated VO2 thin films are several tens of nanometers. The average height of the crystallite is 20 nm and the grain diameter is between 20 and 100 nm. The low-temperature phase transition is accompanied by a significant change in the thin film’s infrared transmission property.
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71.30.+h Metal-insulator transitions and other electronic transitions
68.55.-a Thin film structure and morphology
61.46.Hk Nanocrystals
73.61.-r Electrical properties of specific thin films
81.40.Gh Other heat and thermomechanical treatments
78.66.-w Optical properties of specific thin films

Nonlinear and bistable behavior of an ultrahigh-Q GaAs photonic crystal nanocavity

Evelin Weidner, Sylvain Combrié, Alfredo de Rossi, Nguyen-Vi-Quynh Tran, and Simone Cassette

Appl. Phys. Lett. 90, 101118 (2007); http://dx.doi.org/10.1063/1.2712502 (3 pages) | Cited 24 times

Online Publication Date: 9 March 2007

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The authors investigate the nonlinear and bistable behavior of a high-Q GaAs photonic crystal heterostructure nanocavity, side coupled to a line-defect slab waveguide. The observations agree well with a model incorporating the relevant nonlinearities. The power threshold for bistable behavior is at least one order of magnitude lower than what is reported so far.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers

Detection of terahertz waves using low-temperature-grown InGaAs with 1.56 μm pulse excitation

A. Takazato, M. Kamakura, T. Matsui, J. Kitagawa, and Y. Kadoya

Appl. Phys. Lett. 90, 101119 (2007); http://dx.doi.org/10.1063/1.2712503 (3 pages) | Cited 15 times

Online Publication Date: 9 March 2007

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The authors have investigated the dc and terahertz-detection characteristics of the photoconductive antennas made on low-temperature-grown (LTG) InxGa1−xAs (0.4<x<0.53). It was found that the resistivity of the LTG In0.4Ga0.6As can be as high as 700 Ω cm, with which the resistance of the antenna becomes higher than 3 MΩ. Terahertz waves were detected by the antennas with the pulse excitation at 1.56 μm, with a spectral range exceeding 3 THz, and a dynamic range of about 55 dB. The results also indicate that the photocarrier dynamics depend on the In content.
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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
72.40.+w Photoconduction and photovoltaic effects
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Influence of wall-charge accumulation on the gas dielectric barrier discharge in alternating current plasma display panel

Bingang Guo, Wei Wei, Tsutae Shinoda, and Chunliang Liu

Appl. Phys. Lett. 90, 101501 (2007); http://dx.doi.org/10.1063/1.2710781 (3 pages) | Cited 7 times

Online Publication Date: 5 March 2007

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Influences of wall-charge accumulation on gas dielectric barrier discharge (DBD) breakdown threshold and sustaining voltage margin of alternating current plasma display panel (AC-PDP) were investigated. It is observed that wall-charge accumulation results in a remarkable increase of gas DBD breakdown threshold during sustaining discharge period. Sustaining voltage margin is reduced by the threshold increase. A larger margin can be obtained when the threshold is decreased by removing unfavorable influence of wall-charge accumulation. Compared with normal margin, improved margin has a larger value and a faster linear increase with increasing wall-charge voltage. That indicates a way to improve AC-PDP performances remarkably.
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52.75.-d Plasma devices
52.80.-s Electric discharges
52.40.Hf Plasma-material interactions; boundary layer effects

Mode transition in radio-frequency atmospheric argon discharges with and without dielectric barriers

J. J. Shi and M. G. Kong

Appl. Phys. Lett. 90, 101502 (2007); http://dx.doi.org/10.1063/1.2711413 (3 pages) | Cited 11 times

Online Publication Date: 5 March 2007

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In this letter, basic characteristics of glow modes and their mode transition are studied for radio-frequency (rf) atmospheric argon discharges with bare and dielectrically insulated electrodes. Through input power control, large-volume rf atmospheric argon discharges with bare electrodes are achieved in the α mode via an abrupt transition from a constricted γ mode, whereas dielectrically insulated electrodes result in large argon discharges in both the α and γ modes with gradual mode transition. Current dependence of the 750 nm line intensity and of the gas temperature are shown to capture clearly the signature of mode transition.
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52.80.Pi High-frequency and RF discharges
52.80.Hc Glow; corona
52.40.Hf Plasma-material interactions; boundary layer effects
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

On the production of energetic neutrals in the cathode sheath of direct-current discharges

Tsuyohito Ito and Mark A. Cappelli

Appl. Phys. Lett. 90, 101503 (2007); http://dx.doi.org/10.1063/1.2711416 (3 pages) | Cited 3 times

Online Publication Date: 5 March 2007

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Direct measurements of the energy distribution of energetic neutrals incident onto the cathode of a dc glow discharge are presented. The measurements are performed by time-of-flight analysis of neutrals escaping through a cathode orifice. The experimental results are found to be in excellent agreement with Monte Carlo simulations, although the forward angle of the neutrals considered is limited in the present experimental configuration. It is found that the commonly used theories for the production of energetic neutrals through charge exchange in the cathode sheath do not capture the neutral energy distribution over the range of discharge voltage studied.
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52.80.Hc Glow; corona
52.50.Dg Plasma sources
52.40.Kh Plasma sheaths
52.70.Nc Particle measurements
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
52.25.Ya Neutrals in plasmas

Suspended nanowire web

Volker Cimalla, Mike Stubenrauch, Frank Weise, Michael Fischer, Katja Tonisch, Martin Hoffmann, and Oliver Ambacher

Appl. Phys. Lett. 90, 101504 (2007); http://dx.doi.org/10.1063/1.2711753 (3 pages) | Cited 6 times

Online Publication Date: 5 March 2007

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A complex three-dimensional, nanowire based nanoarchitecture is presented, which can be processed by high-throughput bottom-up procedures without any high-resolution lithography. It combines the benefits of three self-organization mechanisms to produce nanostructures, i.e., the formation of nanoneedles, the droplet formation out of a thin metal film, and the vapor-liquid-solid growth of nanowires. The principle is demonstrated for a silicon based suspended nanowire web. Cell adherence on this assembly was found to be superior to other nanostructures. The possibility of fluid transport beneath the nanowire web enables improved microcatalyst principles and the realization of novel interfaces for biosensing or bioelectronics.
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68.65.La Quantum wires (patterned in quantum wells)
81.10.Bk Growth from vapor
81.16.Hc Catalytic methods
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
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Photoluminescence properties of a single GaN nanorod with GaN/AlGaN multilayer quantum disks

S. N. Yi, Jong H. Na, Kwan H. Lee, Anas F. Jarjour, Robert A. Taylor, Y. S. Park, T. W. Kang, S. Kim, D. H. Ha, G. Andrew, and D. Briggs

Appl. Phys. Lett. 90, 101901 (2007); http://dx.doi.org/10.1063/1.2712772 (3 pages) | Cited 14 times

Online Publication Date: 5 March 2007

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Photoluminescence (PL) properties of a single nanorod containing multiple GaN quantum disks separated by AlGaN potential barriers are investigated using micro-PL spectroscopy. Previous studies reported ensemble spectra from many nanorods. The PL spectra show different features depending on the region of the nanorod excited by the laser, including a sharp feature originating from the quantum disk region. The distinct differences between the PL from the different regions are discussed. The results imply that excitons are strongly confined in the quantum disks, and the authors suggest that small quantum disks can be regarded as quantum dots having a discrete density of states.
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78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
78.55.Cr III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.35.-y Excitons and related phenomena

Study of the defect elimination mechanisms in aspect ratio trapping Ge growth

J. Bai, J.-S. Park, Z. Cheng, M. Curtin, B. Adekore, M. Carroll, A. Lochtefeld, and M. Dudley

Appl. Phys. Lett. 90, 101902 (2007); http://dx.doi.org/10.1063/1.2711276 (3 pages) | Cited 21 times

Online Publication Date: 5 March 2007

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Recent research has demonstrated the effectiveness of the “aspect ratio trapping” technique for eliminating threading dislocations in Ge grown selectively in submicron trenches on Si substrates. In this letter, analysis of the mechanisms by which dislocation elimination is achieved has been carried out. Detailed transmission electron microscopy studies reveal that facets, when formed early in the growth process, play a dominant role in determining the configurations of threading dislocations in the films. These dislocations are shown to behave as “growth dislocations,” which are replicated during growth approximately along the facet normal and so are deflected out from the center of the selective epitaxial regions.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.A- Nucleation and growth
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.37.Lp Transmission electron microscopy (TEM)
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