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5 Sep 2011

Volume 99, Issue 10, Articles (10xxxx)

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Appl. Phys. Lett. 99, 103701 (2011); http://dx.doi.org/10.1063/1.3633066 (3 pages)

Yinan Zhang, David J. S. Birch, and Yu Chen
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Multi-scale surface texture to improve blue response of nanoporous black silicon solar cells

Fatima Toor, Howard M. Branz, Matthew R. Page, Kim M. Jones, and Hao-Chih Yuan

Appl. Phys. Lett. 99, 103501 (2011); http://dx.doi.org/10.1063/1.3636105 (3 pages) | Cited 16 times

Online Publication Date: 6 September 2011

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We characterize the optical and carrier-collection physics of multi-scale textured p-type black Si solar cells with conversion efficiency of 17.1%. The multi-scale texture is achieved by combining density-graded nanoporous layer made by metal-assisted etching with micron-scale pyramid texture. We found that (1) reducing the thickness of nanostructured Si layer improves the short-wavelength spectral response and (2) multi-scale texture permits thinning of the nanostructured layer while maintaining low surface reflection. We have reduced the nanostructured layer thickness by 60% while retaining a solar-spectrum-averaged black Si reflectance of less than 2%. Spectral response at 450 nm has improved from 57% to 71%.
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88.40.jj Silicon solar cells

Doping-dependent device functionality of InP/InAlGaAs long-wavelength light-emitting transistors

Y. Huang, J.-H. Ryou, R. D. Dupuis, F. Dixon, M. Feng, N. Holonyak, Jr., and D. Kuciauskas

Appl. Phys. Lett. 99, 103502 (2011); http://dx.doi.org/10.1063/1.3633345 (3 pages)

Online Publication Date: 7 September 2011

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We report on the control of functionality in long-wavelength light-emitting transistors (LETs) with an InGaAs single quantum-well embedded in N-InP/p-InAlGaAs/N-InAlAs structures by means of the choice of the doping level and dopant in the p-type base layer. As a dual-functional device, the LET works as a heterojunction bipolar transistor (HBT) with a current gain of ∼45 when the base doping level is ∼2 × 1018 cm−3 using zinc (Zn) as the dopant, and it functions like an efficient light-emitting diode (LED) with a carrier capture efficiency of ∼82% when the base doping is ∼8 × 1018 cm−3 using carbon (C) as the dopant. The distinctive device performance and functionality of Zn- and C-doped LETs are attributed to the different quantum capture efficiency and carrier lifetime in the quantum well originating from different base doping schemes.
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85.60.Jb Light-emitting devices
85.30.Pq Bipolar transistors
85.40.Ry Impurity doping, diffusion and ion implantation technology

Determination of long time discharge current in microelectromechanical system capacitive switches

M. Koutsoureli and G. Papaioannou

Appl. Phys. Lett. 99, 103503 (2011); http://dx.doi.org/10.1063/1.3636405 (3 pages) | Cited 3 times

Online Publication Date: 7 September 2011

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An improved method to study the long term discharge current through the dielectric film in microelectromechanical system capacitive switches is presented. The method allows the detection of currents in the sub-fempto-Ampere range by monitoring the decay of the bias for minimum capacitance in the pull-up state. The method has been applied for time interval in excess of 10 000 s. Finally, it is shown that in carefully designed devices the method allows the calculation of the current that arises from the charge fluctuation decay.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)

Five picocoulomb electron bunch generation by ultrafast laser-induced field emission from metallic nano-tip arrays

Anna Mustonen, Paul Beaud, Eugenie Kirk, Thomas Feurer, and Soichiro Tsujino

Appl. Phys. Lett. 99, 103504 (2011); http://dx.doi.org/10.1063/1.3631634 (3 pages) | Cited 10 times

Online Publication Date: 7 September 2011

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Laser-induced field emission from metallic field emitter array cathodes excited by femtosecond near infrared laser pulses is explored. When 50 fs laser pulses irradiated a 1.2 × 105-tip emitter array under a DC field emission bias, electron bunches with bunch charge up to 5.2 pC were observed. The variation of the bunch charge at different laser intensities and polarizations indicated that electrons were produced from the field emitters by a photofield emission process. The result demonstrates the feasibility of metallic field emitter array cathodes for high-charge short-pulse electron source applications.
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78.47.J- Ultrafast spectroscopy (<1 psec)
79.20.Ds Laser-beam impact phenomena
79.70.+q Field emission, ionization, evaporation, and desorption

Enhancement of channel conductivity in AlGaN/GaN heterostructure field effect transistors by AlGaN:Si back barrier

E. Cho, F. Brunner, R. Zhytnytska, P. Kotara, J. Würfl, and M. Weyers

Appl. Phys. Lett. 99, 103505 (2011); http://dx.doi.org/10.1063/1.3634032 (3 pages) | Cited 1 time

Online Publication Date: 7 September 2011

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Heterostructure field effect transistors with three AlGaN/GaN interfaces were designed and investigated. A Si-doped AlGaN back barrier was used to compensate for the reduction of channel conductivity due to a carbon doped semi-insulating GaN buffer layer. Simulation using a one dimensional Poisson-Schrödinger solver showed an enhancement of the charge carrier density which was then confirmed experimentally. Hall and magnetic field dependent mobility measurements proved the Si-doped AlGaN back barrier layer causes neither degradation of electron mobility nor a parasitic conduction channel. Id,max of the transistors was enhanced by a factor of 1.5–2 without decreasing the off-state breakdown voltage.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling

Spatial hole burning degradation of AlGaAs/GaAs laser diodes

Y. B. Qiao, S. W. Feng, C. Xiong, X. W. Wang, X. Y. Ma, H. Zhu, and G. H. Wei

Appl. Phys. Lett. 99, 103506 (2011); http://dx.doi.org/10.1063/1.3634051 (3 pages) | Cited 2 times

Online Publication Date: 7 September 2011

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The degradation of AlGaAs/GaAs laser diodes is studied in detail using laser scanning confocal microscopy, cathodoluminescence images, and x-ray diffraction (XRD) techniques. Our analysis has identified a degradation mechanism that results from the periodic distribution of the carrier density and the near-field intensity originating from periodic spatial hole burning. Based on the XRD measurements, we find that the epitaxial layer enters a polycrystalline phase during degradation due to the dark line defects, and the out-of-plane strain and in-plane compressive stress are induced by degradation.
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42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
07.60.Pb Conventional optical microscopes
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Benchmarking the performance of ultrathin body InAs-on-insulator transistors as a function of body thickness

Kuniharu Takei, Steven Chuang, Hui Fang, Rehan Kapadia, Chin-Hung Liu, Junghyo Nah, Ha Sul Kim, E. Plis, Sanjay Krishna, Yu-Lun Chueh, and Ali Javey

Appl. Phys. Lett. 99, 103507 (2011); http://dx.doi.org/10.1063/1.3636110 (3 pages) | Cited 5 times

Online Publication Date: 8 September 2011

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The effect of body thickness (5-13 nm) on the leakage currents of top-gated, InAs-on-insulator field-effect-transistors with a channel length of ∼200 nm is explored. From a combination of experiments and simulation, it is found that the OFF-state currents are primarily dominated by Shockley Read Hall recombination/generation and trap-assisted tunneling. The OFF currents are shown to decrease with thickness reduction, highlighting the importance of the ultrathin body device configuration. The devices exhibit promising performances, with a peak extrinsic and intrinsic transconductances of ∼1.7 and 2.3 mS/μm, respectively, at a low source/drain voltage of 0.5 V and a body thickness of ∼13 nm.
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85.30.Tv Field effect devices

Prospect of charge enhancement by increasing top oxide thickness of silicon-on-insulator fin field effect transistors

Md. Zunaid Baten, Raisul Islam, Emran Md. Amin, and Quazi D. M. Khosru

Appl. Phys. Lett. 99, 103508 (2011); http://dx.doi.org/10.1063/1.3634045 (3 pages)

Online Publication Date: 8 September 2011

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The variation of electrostatic and transport characteristics of silicon-on-insulator fin field effect transistors (FinFETs) having sub-10 nm fin dimensions is investigated with the variation of top oxide thickness. Capacitance voltage and ballistic transport characteristics of double gate (DG) and triple gate (TG) FinFETs are obtained by self-consistently solving the coupled Schrödinger’s and Poisson’s equations. Performance enhancement can be obtained in terms of both on-state current and inversion capacitance by increasing the top oxide thickness of highly scaled FinFETs. The work suggests limiting values of the device parameter to differentiate the DG and TG variants of FinFET.
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85.30.Tv Field effect devices

High rejection, tunable parallel resonance in micromachined lead zirconate titanate on silicon resonators

Sarah S. Bedair, Daniel Judy, Jeffrey Pulskamp, Ronald G. Polcawich, Adam Gillon, Eugene Hwang, and Sunil Bhave

Appl. Phys. Lett. 99, 103509 (2011); http://dx.doi.org/10.1063/1.3636432 (3 pages) | Cited 2 times

Online Publication Date: 9 September 2011

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This paper presents a micromachined lead zirconate titanate-on-silicon electromechanical resonator, tunable from series to parallel resonance, for either bandstop or bandpass filter applications. Scattering parameter measurements (9.2 V direct current (DC) bias) reveal bandstop rejection levels > 109 dB at 59.74 MHz and passband loss of 40 dB with a −20-dB bandwidth of 25 kHz (0.042%). These compare within 5-dB of the models. Parallel resonance is also observed for an alternate mechanical mode at 182.8 MHz with a 1.5 V DC bias with a rejection of 54.7 dB, a −20 dB bandwidth of 41 kHz (0.022%). This mode is tunable with the electric field to show series resonance.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
84.30.Vn Filters
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Degradation of polycrystalline HfO2-based gate dielectrics under nanoscale electrical stress

V. Iglesias, M. Lanza, K. Zhang, A. Bayerl, M. Porti, M. Nafría, X. Aymerich, G. Benstetter, Z. Y. Shen, and G. Bersuker

Appl. Phys. Lett. 99, 103510 (2011); http://dx.doi.org/10.1063/1.3637633 (3 pages) | Cited 4 times

Online Publication Date: 9 September 2011

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The evolution of the electrical properties of HfO2/SiO2/Si dielectric stacks under electrical stress has been investigated using atomic force microscope-based techniques. The current through the grain boundaries (GBs), which is found to be higher than thorough the grains, is correlated to a higher density of positively charged defects at the GBs. Electrical stress produces different degradation kinetics in the grains and GBs, with a much shorter time to breakdown in the latter, indicating that GBs facilitate dielectric breakdown in high-k gate stacks.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.22.Jp Dielectric breakdown and space-charge effects
61.72.Mm Grain and twin boundaries
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