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10 Mar 2008

Volume 92, Issue 10, Articles (10xxxx)

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Appl. Phys. Lett. 92, 102101 (2008); http://dx.doi.org/10.1063/1.2890735 (3 pages)

Qing Wan, Jin Huang, Zhong Xie, Taihong Wang, Eric N. Dattoli, and Wei Lu
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Analysis of dispersive electroacoustic coupling configurations for application to gigahertz-band, temperature-compensated AlN-based acoustic devices

Cinzia Caliendo

Appl. Phys. Lett. 92, 103501 (2008); http://dx.doi.org/10.1063/1.2892044 (3 pages) | Cited 1 time

Online Publication Date: 10 March 2008

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AlN films, 1.4–6.2 μm thick, were sputtered on z-cut Al2O3 substrates and four electroacoustic coupling configurations were realized and characterized for x and y surface acoustic wave (SAW) propagation directions. The temperature-coefficient of delay dispersion curves of the four configurations was experimentally evaluated and eight temperature-compensated points were estimated. The velocity anisotropy of the multilayers was investigated for different AlN film thicknesses, electric excitation conditions, and temperature values. The design trade-offs required for temperature-compensated, 50 Ω matched, gigahertz-range, enhanced-coupling, low loss SAW devices are provided for the four dispersive coupling configurations.
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81.05.Ea III-V semiconductors
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
43.38.+n Transduction; acoustical devices for the generation and reproduction of sound

Solar-blind AlGaN-based p-i-n photodetectors with high breakdown voltage and detectivity

Turgut Tut, Tolga Yelboga, Erkin Ulker, and Ekmel Ozbay

Appl. Phys. Lett. 92, 103502 (2008); http://dx.doi.org/10.1063/1.2895643 (3 pages) | Cited 25 times

Online Publication Date: 10 March 2008

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We report on the high performance solar-blind AlGaN-based p-i-n photodetectors that are grown by metal-organic chemical vapor deposition on c-plane sapphire substrates. The dark current of the 200 μm diameter devices was measured to be on the order of 5 fA for bias voltages up to 10 V. The breakdown voltages were higher than 200 V. The responsivities of the photodetectors were 0.052 and 0.093 A/W at 280 nm under 0 and 40 V reverse biases, respectively. We achieved a detectivity of 7.5×1014 cm Hz1/2/W for 200 μm diameter AlGaN p-i-n detectors.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.Dw Photodiodes; phototransistors; photoresistors

GaInP/GaAs dual junction solar cells on Ge/Si epitaxial templates

Melissa J. Archer, Daniel C. Law, Shoghig Mesropian, Moran Haddad, Christopher M. Fetzer, Arthur C. Ackerman, Corinne Ladous, Richard R. King, and Harry A. Atwater

Appl. Phys. Lett. 92, 103503 (2008); http://dx.doi.org/10.1063/1.2887904 (3 pages) | Cited 11 times

Online Publication Date: 11 March 2008

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Large area, crack-free GaInP/GaAs double junction solar cells were grown by metal organic chemical vapor deposition on Ge/Si templates fabricated using wafer bonding and ion implantation induced layer transfer. Photovoltaic performance of these devices was comparable to those grown on bulk epi-ready Ge, demonstrating the feasibility of alternative substrates fabricated via wafer bonding and layer transfer for growth of active devices on lattice mismatched substrates.
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84.60.Jt Photoelectric conversion

Tunable transmission spectra of acoustic waves through double phononic crystal slabs

Fengming Liu, Feiyan Cai, Yiqun Ding, and Zhengyou Liu

Appl. Phys. Lett. 92, 103504 (2008); http://dx.doi.org/10.1063/1.2896146 (3 pages) | Cited 14 times

Online Publication Date: 11 March 2008

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Acoustic resonant modes in a slab with a periodic array of holes are analyzed by using three-dimensional finite-difference time-domain method. We show that there exist two different types of resonant modes in this slab: the coupled Stoneley wave resonant modes and the waveguide resonant modes. Both resonant modes can lead to complex resonant line shapes in the transmission spectrum. By using the distinct property of these resonant modes, a tunable phononic crystal structure consisting of coupled phononic crystal slabs is introduced for achieving acoustic filters and sensors.
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42.70.Qs Photonic bandgap materials
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects

Temperature dependence on current-voltage characteristics of Ni/Au–Al0.45Ga0.55N Schottky photodiode

C. J. Cheng, X. F. Zhang, Z. X. Lu, J. X. Ding, L. Zhang, L. Zhao, J. J. Si, W. G. Sun, L. W. Sang, Z. X. Qin, and G. Y. Zhang

Appl. Phys. Lett. 92, 103505 (2008); http://dx.doi.org/10.1063/1.2896298 (3 pages) | Cited 4 times

Online Publication Date: 11 March 2008

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Temperature dependence on electrical characteristics of a Ni/Au–Al0.45Ga0.55N Schottky photodiode is investigated in a temperature range of 198–323 K. The ideality factor decreases from 2.57 to 1.75, while the barrier height increases from 0.75 to 1.14 eV in this temperature range. The ln(I)-V curves at a small forward current are intersectant at 273, 298, and 323 K and are almost parallel at 198, 223, and 248 K. This crossing of the ln(I)-V curves is an inherent property of Schottky diodes, and the almost parallel curves can be well explained by thermionic field emission theory.
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85.60.Dw Photodiodes; phototransistors; photoresistors
85.30.Kk Junction diodes

Monolayer segregation of As atoms at the interface between gate oxide and Si substrate in a metal-oxide-semiconductor field effect transistor by three-dimensional atom-probe technique

Koji Inoue, Fumiko Yano, Akio Nishida, Takaaki Tsunomura, Takeshi Toyama, Yasuyoshi Nagai, and Masayuki Hasegawa

Appl. Phys. Lett. 92, 103506 (2008); http://dx.doi.org/10.1063/1.2891081 (3 pages) | Cited 12 times

Online Publication Date: 11 March 2008

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Atom-probe technique was applied to analyze three-dimensional dopant distribution in Si substrate of metal-oxide-semiconductor field effect transistor (MOSFET) structure. As a result, three-dimensional As atom distribution implanted in Si was obtained. The quantification of the As atom distribution in a depth direction was confirmed as compared with the one-dimensional distribution measured by secondary ion mass spectroscopy. Moreover, monolayer segregation of As atoms at the interface between gate oxide and Si substrate was clearly observed. This result shows the possibility to clarify discrete dopant distribution in Si substrate related to the characteristic variation of MOSFETs.
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85.30.Tv Field effect devices
85.40.Ry Impurity doping, diffusion and ion implantation technology

Influence of crystalline quality of low-temperature GaN cap layer on current collapse in AlGaN/GaN heterostructure field-effect transistors

E. Waki, T. Deguchi, A. Nakagawa, and T. Egawa

Appl. Phys. Lett. 92, 103507 (2008); http://dx.doi.org/10.1063/1.2896311 (3 pages) | Cited 1 time

Online Publication Date: 11 March 2008

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The correlation between the crystalline quality of low-temperature GaN (LT-GaN) films and current collapse in AlGaN/GaN heterostructure field-effect transistors with a LT-GaN cap layer was investigated. LT-GaN cap layers were grown at various temperatures ranging from 450 to 700 °C. No current collapse was observed for heterostructure field-effect transistors with LT-GaN cap layers grown at 500 and 550 °C. The crystalline quality of the 1-μm-thick LT-GaN films grown at 450–700 °C was then studied through x-ray diffraction and selected area electron diffraction measurements. The crystalline quality, considered by measuring the full width at half maximum through x-ray diffraction, deteriorated as the growth temperature decreased. The crystal structure of LT-GaN films grown at 500 and 550 °C was confirmed as polycrystalline. Thus, the results demonstrated that in AlGaN/GaN heterostructure field-effect transistors, a polycrystalline structure provides the most effective LT-GaN cap layer for suppressing current collapse.
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85.30.Tv Field effect devices

Light-induced programming of Si nanocrystal flash memories

J. S. de Sousa, G. A. Farias, and J.-P. Leburton

Appl. Phys. Lett. 92, 103508 (2008); http://dx.doi.org/10.1063/1.2839326 (3 pages) | Cited 5 times

Online Publication Date: 11 March 2008

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We show theoretically that it is possible to achieve much faster programming performances in nanocrystal flash memory devices by means of a light-induced mechanism that inverts the direction of charge transfer between nanocrystals and device substrate in comparison to conventional voltage-induced programming. Our method is based on the self-consistent solutions of Hartree and Poisson equation for both electrons and holes with open boundary conditions.
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71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
71.10.Li Excited states and pairing interactions in model systems
81.05.Cy Elemental semiconductors

State-independent optimal control of dissipative qubits

M. Wenin and W. Pötz

Appl. Phys. Lett. 92, 103509 (2008); http://dx.doi.org/10.1063/1.2894200 (3 pages) | Cited 2 times

Online Publication Date: 11 March 2008

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A general state-independent optimal control strategy for weakly dissipative quantum systems is presented. It allows the identification of Hamilton operators which approximately perform a preselected unitary operation and minimize the adverse effects from a dissipative environment. This direct method is demonstrated at the example of a single qubit, as realized, for example, by the spin of an excess electron in a quantum dot or a Josephson flux qubit, with Lindblad dissipator. We show that optimal solutions for arbitrary unitary single-qubit operations may be found both analytically and numerically.
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03.67.Lx Quantum computation architectures and implementations

Effect of hot-carrier-induced interface states distribution on linear drain current degradation in 0.35 μm n-type lateral diffused metal-oxide-semiconductor transistors

J. R. Lee, Jone F. Chen, Kuo-Ming Wu, C. M. Liu, and S. L. Hsu

Appl. Phys. Lett. 92, 103510 (2008); http://dx.doi.org/10.1063/1.2894517 (3 pages) | Cited 2 times

Online Publication Date: 11 March 2008

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The mechanisms of hot-carrier-induced linear drain current (Idlin) degradation in a 0.35 μm n-type lateral diffused metal-oxide-semiconductor transistor, operating at a nominal voltage of 12 V, is investigated. Results and analysis show that the location of hot-carrier-induced interface states varies with stress gate voltage. Stress-induced interface states located in accumulation region under polygate have little effect on Idlin degradation. As a result, interface states located in drain-side spacer region dominate Idlin degradation when interface states located in channel region are negligible.
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85.30.Tv Field effect devices

Effective-barrier-thickness fluctuation and critical-current spread of grain-boundary Josephson junctions

J. T. Jeng and C. H. Wu

Appl. Phys. Lett. 92, 103511 (2008); http://dx.doi.org/10.1063/1.2895811 (3 pages) | Cited 2 times

Online Publication Date: 12 March 2008

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The phenomenological formulas for the critical-current spread of the bicrystal grain-boundary Josephson junctions are proposed. By considering the intrinsically shunted-junction model and the gamma distribution, the fluctuation of effective-barrier thickness from 0.01 to 0.1 nm corresponds to the 1−σ critical-current spread from 14% to 106%. With a fixed scale parameter, the critical-current spread is inversely proportional to the square root of the bridge width. When the bridge width is fixed, the spread is inversely proportional to the square root of the mean critical-current density. These predictions are qualitatively in agreement with the experimental results reported to date.
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61.72.Mm Grain and twin boundaries
74.50.+r Tunneling phenomena; Josephson effects
74.25.Sv Critical currents
74.72.-h Cuprate superconductors

Observation of the high-Q modes inside the resonance zone of two-dimensional Bragg structures

N. S. Ginzburg, N. Yu. Peskov, A. S. Sergeev, G. G. Denisov, S. V. Kuzikov, V. Yu. Zaslavsky, A. V. Arzhannikov, P. V. Kalinin, S. L. Sinitsky, and M. Thumm

Appl. Phys. Lett. 92, 103512 (2008); http://dx.doi.org/10.1063/1.2891103 (3 pages) | Cited 5 times

Online Publication Date: 12 March 2008

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Electrodynamical properties of two-dimensional Bragg resonators of planar geometry are studied in the frame of the geometrical-optical approach and in three-dimensional simulations. Results of the theoretical analysis are corroborated by data obtained in “cold” microwave measurements. Formation of the high-Q eigenmodes in the vicinity of the Bragg resonance frequency has been demonstrated.
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42.79.-e Optical elements, devices, and systems

Visualization of heat flows in high-power diode lasers by lock-in thermography

Mathias Ziegler, Jens W. Tomm, Thomas Elsaesser, Götz Erbert, Frank Bugge, Włodzimierz Nakwaski, and Robert P. Sarzała

Appl. Phys. Lett. 92, 103513 (2008); http://dx.doi.org/10.1063/1.2898199 (3 pages) | Cited 2 times

Online Publication Date: 13 March 2008

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Lock-in thermography is applied to analyze thermal properties of high-power diode lasers. With a temporal resolution of about 100 μs for thermal imaging of the entire device, microscopic heat flows occurring on a millisecond time scale and propagating infrared light are distinguished. This allows for a measurement of heat transport in the device on a 100 μm length scale and an identification of “hot spots” at the device edges as scattered thermal radiation. Thermal transients are monitored and described quantitatively by finite element modeling. Thermographic images of the laser side identify the front facet as a major heat source.
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42.55.Px Semiconductor lasers; laser diodes
44.10.+i Heat conduction

Real-time thermal imaging of catastrophic optical damage in red-emitting high-power diode lasers

Mathias Ziegler, Jens W. Tomm, Thomas Elsaesser, Clemens Matthiesen, Marwan Bou Sanayeh, and Peter Brick

Appl. Phys. Lett. 92, 103514 (2008); http://dx.doi.org/10.1063/1.2898202 (3 pages) | Cited 13 times

Online Publication Date: 13 March 2008

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The dynamics of the catastrophic optical damage process under continuous wave operation is analyzed in red-emitting high-power diode lasers by means of combined thermal and optical near-field (NF) imaging with cameras. The catastrophic process is revealed as extremely fast (Δt ⩽ 2.3 ms) and spatially confined. It is connected with a pronounced impulsive temperature change. Its coincidence with the most intense NF filament is indicative of the critical nature of thermal runaway in the catastrophic process.
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42.55.Px Semiconductor lasers; laser diodes
42.65.Sf Dynamics of nonlinear optical systems; optical instabilities, optical chaos and complexity, and optical spatio-temporal dynamics

High-power single mode (>1 W) continuous wave operation of longitudinal photonic band crystal lasers with a narrow vertical beam divergence

I. I. Novikov, N. Yu. Gordeev, Yu. M. Shernyakov, Yu. Yu. Kiselev, M. V. Maximov, P. S. Kop’ev, A. Sharon, R. Duboc, D. B. Arbiv, U. Ben-Ami, V. A. Shchukin, and N. N. Ledentsov

Appl. Phys. Lett. 92, 103515 (2008); http://dx.doi.org/10.1063/1.2898517 (3 pages) | Cited 7 times

Online Publication Date: 14 March 2008

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We report on 980 nm InGaAs/AlGaAs lasers with a broad waveguide based on a longitudinal photonic band crystal concept. The beam divergence measured as full width at half maximum was as narrow as <5° (vertical). Broad area 100 μm multimode devices demonstrated >15 W pulsed operation as limited by the current source. Significantly increased modal spot size enabled stable single lateral mode operation in broad ridge 10 μm stripes. Maximum continuous wave power in single mode regime of 1.3 W for 10 μm wide stripe lasers was obtained, being limited by the catastrophic degradation of the unpassivated laser facets.
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42.55.Tv Photonic crystal lasers and coherent effects
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Optimal electrode shape and size of doubly rotated quartz plate thickness mode piezoelectric resonators

Zengtao Yang, Jiashi Yang, and Yuantai Hu

Appl. Phys. Lett. 92, 103516 (2008); http://dx.doi.org/10.1063/1.2896998 (2 pages) | Cited 3 times

Online Publication Date: 14 March 2008

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Using the Stevens–Tiersten equation for slowly varying thickness modes in doubly rotated quartz plate piezoelectric resonators, we determine optimal electrode shape and size for these resonators. The electrodes obtained are optimal in that they satisfy Bechmann’s number in every direction.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
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