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19 Apr 2010

Volume 96, Issue 16, Articles (16xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 96, 163101 (2010); http://dx.doi.org/10.1063/1.3327831 (3 pages)

Ramesh Nath, Seungbum Hong, Jeffrey A. Klug, Alexandra Imre, Michael J. Bedzyk, Ram S. Katiyar, and Orlando Auciello
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“Rainbow” trapped in a self-similar coaxial optical waveguide

Qing Hu, Jin-Zhu Zhao, Ru-Wen Peng, Feng Gao, Rui-Li Zhang, and Mu Wang

Appl. Phys. Lett. 96, 161101 (2010); http://dx.doi.org/10.1063/1.3399778 (3 pages) | Cited 5 times

Online Publication Date: 19 April 2010

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We report in this paper that the light waves with different frequencies can be selectively guided and spatially separated in a self-similar dielectric waveguide, where a hollow core is surrounded by a coaxial Thue–Morse multilayer. Due to the self-similar furcation feature in the photonic band structure, the transmission multibands are achieved. More interestingly, this dielectric waveguide supports “cladding modes,” which are spatially separated and confined along the waveguide. Consequently, a “rainbow” can be trapped (spatial confined but not stopped) in the Thue–Morse waveguide. The finding can be applied to designing miniaturized compact photonic devices, such as spectroscopy on a chip.
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42.79.Gn Optical waveguides and couplers
42.70.Qs Photonic bandgap materials

Continuous operation of high bit rate quantum key distribution

A. R. Dixon, Z. L. Yuan, J. F. Dynes, A. W. Sharpe, and A. J. Shields

Appl. Phys. Lett. 96, 161102 (2010); http://dx.doi.org/10.1063/1.3385293 (3 pages) | Cited 20 times

Online Publication Date: 19 April 2010

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We demonstrate a quantum key distribution with a secure bit rate exceeding 1 Mbit/s over 50 km fiber averaged over a continuous 36 h period. Continuous operation of high bit rates is achieved using feedback systems to control path length difference and polarization in the interferometer and the timing of the detection windows. High bit rates and continuous operation allows finite key size effects to be strongly reduced, achieving a key extraction efficiency of 96% compared to keys of infinite lengths.
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03.67.Dd Quantum cryptography and communication security
07.60.Ly Interferometers
42.81.Gs Birefringence, polarization
42.50.-p Quantum optics
42.79.Sz Optical communication systems, multiplexers, and demultiplexers

High-speed all-optical terahertz polarization switching by a transient plasma phase modulator

Haidan Wen, Dan Daranciang, and Aaron M. Lindenberg

Appl. Phys. Lett. 96, 161103 (2010); http://dx.doi.org/10.1063/1.3407514 (3 pages) | Cited 5 times

Online Publication Date: 20 April 2010

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We demonstrate high-speed all-optical polarization switching of broadband terahertz frequency electromagnetic fields with subpicosecond switch-on time. This is achieved through the use of a two-plasma configuration in an orthogonal geometry in which one plasma modulates the relative phase of a two-color optical pump field, enabling rapid terahertz polarization modulation at rates limited by the repetition-rate of the control pulse.
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52.38.Dx Laser light absorption in plasmas (collisional, parametric, etc.)
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.79.Hp Optical processors, correlators, and modulators
42.60.Fc Modulation, tuning, and mode locking

Circuit model for a periodic array of slits sandwiched between two dielectric slabs

Raúl Rodríguez-Berral, Francisco Mesa, and Francisco Medina

Appl. Phys. Lett. 96, 161104 (2010); http://dx.doi.org/10.1063/1.3405721 (3 pages) | Cited 3 times

Online Publication Date: 20 April 2010

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This paper proposes an equivalent circuit model that uses lumped elements and transmission lines to explain the transmission of electromagnetic waves through a conducting screen periodically perforated with slits and sandwiched between two different dielectric slabs. The present model relies on the impedance-matching point of view, previously introduced by some of the authors, rather than on the surface plasmon polariton concept. Thus, the model constitutes a simple and insightful framework that easily leads to accurate qualitative and quantitative predictions about the nature of the transmission spectrum of such structures.
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84.30.-r Electronic circuits
41.20.Jb Electromagnetic wave propagation; radiowave propagation

Room-temperature continuous-wave metal grating distributed feedback quantum cascade lasers

M. Carras, G. Maisons, B. Simozrag, M. Garcia, O. Parillaud, J. Massies, and X. Marcadet

Appl. Phys. Lett. 96, 161105 (2010); http://dx.doi.org/10.1063/1.3399779 (3 pages) | Cited 4 times

Online Publication Date: 21 April 2010

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We report on the design and elaboration of continuous wave (cw) distributed feedback quantum cascade lasers (QCLs) using a simple metal grating approach without epitaxial regrowth, neither for the grating nor for the thermal extraction. Room temperature cw single monomode QCLs with 30 dB side mode suppression ratio are demonstrated down to 4.5 μm with 20 mW output power and threshold of 1.5 kA cm−2. The beam quality factor (M2) does not exceed 1.22 for both axes. These results are discussed and the key issue of thermal management of the device is emphasized.
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42.55.Px Semiconductor lasers; laser diodes
42.79.Dj Gratings

Optical properties of II-VI colloidal quantum dot doped porous silicon microcavities

Hong Qiao, Bin Guan, Till Böcking, Michael Gal, J. Justin Gooding, and Peter J. Reece

Appl. Phys. Lett. 96, 161106 (2010); http://dx.doi.org/10.1063/1.3404183 (3 pages) | Cited 3 times

Online Publication Date: 21 April 2010

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In this paper we report on the light emitting properties of mesoporous silicon vertical-cavity optical resonators with II-VI colloidal quantum dots selectively deposited in the cavity layer. Optical resonator structures exhibit reflectivity stop bands of several hundred nanometres and resonant modes with line-widths less than 3.5 nm. The observed modification of spectral and spatial emission properties of the quantum dots and tenfold enhancement at the resonance wavelength is consistent with cavity enhanced spontaneous emission. Using this hybrid fabrication approach we show that narrow band light emitting structures may be fabricated over a broad spectral region in the visible and near-infrared.
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42.79.Gn Optical waveguides and couplers
82.70.Dd Colloids
85.60.Jb Light-emitting devices

Plasmonic enhanced quantum well infrared photodetector with high detectivity

Wei Wu, Alireza Bonakdar, and Hooman Mohseni

Appl. Phys. Lett. 96, 161107 (2010); http://dx.doi.org/10.1063/1.3419885 (3 pages) | Cited 14 times

Online Publication Date: 22 April 2010

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We report a normal-incident quantum well infrared photodetector (QWIP) strongly coupled with surface plasmon modes. A periodic hole array perforated in gold film was integrated with In0.53Ga0.47As/InP QWIP to convert normal-incident electromagnetic waves into surface plasmon waves, and to excite the intersubband transition of carriers in the quantum wells. The peak responsivity of the photodetector at ∼ 8 μm was ∼ 7 A/W at the bias of 0.7 V at 78 K with the peak detectivity as high as ∼ 7.4×1010 cm Hz1/2/W. The full width at half maximum of the response spectrum was only ∼ 0.84 μm due to a narrow plasmonic resonance.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.82.Gw Other integrated-optical elements and systems
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

Spectroscopy of 1.55μm PbS quantum dots on Si photonic crystal cavities with a fiber taper waveguide

M. T. Rakher, R. Bose, C. W. Wong, and K. Srinivasan

Appl. Phys. Lett. 96, 161108 (2010); http://dx.doi.org/10.1063/1.3396988 (3 pages) | Cited 2 times

Online Publication Date: 23 April 2010

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We use an optical fiber taper waveguide to probe PbS quantum dots (QDs) dried on Si photonic crystal cavities near 1.55μm. We demonstrate that a low density (≲100 μm−2) of QDs does not significantly degrade cavity quality factors as high as ≈ 3×104. We also show that the tapered fiber can be used to excite the QDs and collect the subsequent cavity-filtered photoluminescence, and present measurements of reversible photodarkening and QD saturation. This method represents an important step toward spectroscopy of single colloidal QDs in the telecommunications band.
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78.67.Hc Quantum dots
42.70.Qs Photonic bandgap materials
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.55.-m Photoluminescence, properties and materials
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Theoretical investigation of a high efficiency and broadband subterahertz gyrotron

Nai-Ching Chen, Tsun-Hsu Chang, Ching-Pin Yuan, Toshitaka Idehara, and Isamu Ogawa

Appl. Phys. Lett. 96, 161501 (2010); http://dx.doi.org/10.1063/1.3400216 (3 pages) | Cited 7 times

Online Publication Date: 19 April 2010

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This study investigates the electron dynamics of gyrotron interaction in a tapered waveguide and proposes an interaction structure for a 0.2 THz TE02 reflective gyrotron backward-wave oscillator (gyro-BWO). The design shows the advantages of high power, continuous, and broadband frequency tuning, mode converter free, and inherently possesses mode-selective ability to suppress the potentially competing TE22 mode. Calculated results indicate that the reflective TE02 gyro-BWO is capable of generating a peak power of 3.3 kW corresponding to 26.3% interacting efficiency with a broad 3dB tuning bandwidth of 6.9 GHz at beam current Ib = 0.5 A and beam voltage Vb = 25 kV.
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84.40.Ik Masers; gyrotrons (cyclotron-resonance masers)
84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)
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Role of c-screw dislocations on indium segregation in InGaN and InAlN alloys

Huaping Lei, Jun Chen, and Pierre Ruterana

Appl. Phys. Lett. 96, 161901 (2010); http://dx.doi.org/10.1063/1.3394007 (3 pages) | Cited 4 times

Online Publication Date: 19 April 2010

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Indium segregation induced by c-screw dislocations in wurtzite InGaN and InAlN alloys is investigated with molecular dynamics based on Stillinger–Weber potentials [ Stillinger and Weber, Phys. Rev. B 31, 5262 (1985)] . Beginning with the analysis of atomic structures and energetic stability of c-screw dislocations in AlN, GaN, and InN compounds, their interaction with In atoms in GaN and AlN is explored. The results show that In atoms reduce the core energy of c-screw dislocation when they are located at the center of the core region. The distance dependence of the interaction energy indicates that In atoms will tend to gather around the dislocation line and form an In-rich region. These results agree with experimental observations in InGaN and should predict a similar behavior in InAlN.
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61.72.Lk Linear defects: dislocations, disclinations
61.72.Yx Interaction between different crystal defects; gettering effect
64.75.Qr Phase separation and segregation in semiconductors
02.70.Ns Molecular dynamics and particle methods

Experimental verification of a tunable left-handed material by bias magnetic fields

Yin Poo, Rui-xin Wu, Guang-hua He, Ping Chen, Jie Xu, and Ri-feng Chen

Appl. Phys. Lett. 96, 161902 (2010); http://dx.doi.org/10.1063/1.3409120 (3 pages) | Cited 2 times

Online Publication Date: 22 April 2010

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We designed a two-dimensional periodic composite made of ferrite rods and metallic wires, and theoretically proved the composite in magnetized state had a tunable left-handed material (LHM) regime by its transmission properties and the retrieved effective permittivity and permeability. Further, we fabricated a sample as designed, and experimentally demonstrated the LHM regime by the sample’s abnormal transmission in bias magnetic fields. The abnormal transmission changes with the intensity of the bias magnetic field showing the frequency tunable character of the LHM regime.
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42.70.-a Optical materials
77.22.Ch Permittivity (dielectric function)
42.25.Bs Wave propagation, transmission and absorption

Effect of thermal annealing on properties of InSbN grown by molecular beam epitaxy

K. P. Lim, H. T. Pham, S. F. Yoon, C. Y. Ngo, and S. Tripathy

Appl. Phys. Lett. 96, 161903 (2010); http://dx.doi.org/10.1063/1.3399775 (3 pages) | Cited 5 times

Online Publication Date: 22 April 2010

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We study the annealing effects on the properties of as-grown InSbN films. The annihilation of donor defects in the form of N-N interstitials is suggested by the shifting of N induced tensile strain and a decrease in free electron concentration from ∼ 1×1018 to device level of ∼ 2×1016 cm−3. These findings support the argument that N interstitials thermally dissociate into single N. Corresponding signatures for the reduced Sb antisites and N-N interstitial defects are apparent in Raman spectra. This work will benefit those working on long wavelength infrared photodetectors.
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61.72.Cc Kinetics of defect formation and annealing
61.72.jj Interstitials
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.ag Semiconductors
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors

The configurational entropy of mixing of interstitials solid solutions

Jorge Garcés

Appl. Phys. Lett. 96, 161904 (2010); http://dx.doi.org/10.1063/1.3400221 (3 pages) | Cited 2 times

Online Publication Date: 22 April 2010

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A simple and general expression for the configurational entropy of mixing of multicomponent interstitials solid solutions is deduced based on a probabilistic approach to compute the configurational entropy. The good agreement obtained with previous experimental and theoretical works based on Monte Carlo and partial configurational entropy calculations in binary systems show that the expression is suitable to be used as a reference state to compute the excess thermodynamic functions in multicomponent interstitials solid solutions. The results show that the configurational entropy can be computed to a high degree of accuracy in some systems without the use of a computer.
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65.40.gd Entropy
64.75.Ef Mixing
61.72.jj Interstitials
64.60.De Statistical mechanics of model systems (Ising model, Potts model, field-theory models, Monte Carlo techniques, etc.)

Characterization of polycrystals with elongated duplex microstructure by inversion of ultrasonic backscattering data

O. I. Lobkis and S. I. Rokhlin

Appl. Phys. Lett. 96, 161905 (2010); http://dx.doi.org/10.1063/1.3416910 (3 pages) | Cited 2 times

Online Publication Date: 23 April 2010

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In this letter a simple analytical ultrasonic backscattering model is proposed for determination of characteristic microstructural scales in polycrystalline materials with elongated grains. The inversion methodology for microstructural parameters is based on backscattering coefficient ratios measured in different propagation directions. The ultrasonic backscattering measurements were performed on a Ti alloy sample with a duplex microstructure and the model was applied to experimental data inversion to size the material microtexture.
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43.35.Yb Ultrasonic instrumentation and measurement techniques
81.40.-z Treatment of materials and its effects on microstructure, nanostructure, and properties
81.05.Bx Metals, semimetals, and alloys
62.65.+k Acoustical properties of solids
43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants

Ultrafast manipulation of hard x-rays by efficient Bragg switches

M. Herzog, W. Leitenberger, R. Shayduk, R. M. van der Veen, C. J. Milne, S. L. Johnson, I. Vrejoiu, M. Alexe, D. Hesse, and M. Bargheer

Appl. Phys. Lett. 96, 161906 (2010); http://dx.doi.org/10.1063/1.3402773 (3 pages) | Cited 7 times

Online Publication Date: 23 April 2010

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We experimentally demonstrate efficient switching of the hard x-ray Bragg reflectivity of a SrRuO3/SrTiO3 superlattice by optical excitation of large-amplitude coherent acoustic superlattice phonons. The rocking curve changes drastically on a 1 ps timescale. The (0 0 116) reflection is almost extinguished (ΔR/R0 = −0.91), while the (0 0 118) reflection increases by more than an order of magnitude (ΔR/R0 = 24.1). The change of the x-ray structure factor depends nonlinearly on the phonon amplitude, allowing manipulation of the x-ray response on a timescale considerably shorter than the phonon period. Numerical simulations for a superlattice with slightly changed geometry and realistic parameters predict a switching-contrast ratio ΔR/R0 of 700 with high reflectivity.
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78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
68.65.Cd Superlattices
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
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The transport and quantum capacitance properties of epitaxial graphene

J. L. Xia, Fang Chen, J. L. Tedesco, D. K. Gaskill, R. L. Myers-Ward, C. R. Eddy, D. K. Ferry, and N. J. Tao

Appl. Phys. Lett. 96, 162101 (2010); http://dx.doi.org/10.1063/1.3396982 (3 pages) | Cited 7 times

Online Publication Date: 19 April 2010

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Epitaxial graphene field effect transistors were fabricated, characterized, and studied. Both the capacitance and transport measurements were performed on the same devices using an electrochemical gate. The quantum capacitance of the epitaxial graphene was extracted, which was similar to that of exfoliated graphene near the Dirac point, but it exhibits a large sublinear behavior at high carrier densities. The recently developed self-consistent theory for charged impurities in graphene is found to provide a reasonable description of the transport data, but a more complete theory is needed to explain both the transport and quantum capacitance data for the epitaxial graphene devices.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling

Geminate electron-hole recombination in organic solids in the presence of a donor-acceptor heterojunction

Mariusz Wojcik, Przemyslaw Michalak, and M. Tachiya

Appl. Phys. Lett. 96, 162102 (2010); http://dx.doi.org/10.1063/1.3397992 (3 pages) | Cited 6 times

Online Publication Date: 19 April 2010

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Geminate electron-hole recombination is one of the main factors limiting the efficiency of organic solar cells. We present a systematic study of this process based on both analytical and simulation models. We determine how the charge-pair separation probability is affected by the hopping length of charge carriers, the presence of a donor-acceptor heterojunction, electron and hole mobilities, and other factors. We show that the charge-pair separation probability of an electron and a hole which are initially at the contact distance is maximized when the electron and hole mobilities are equal to each other.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.20.Ee Mobility edges; hopping transport
72.20.Fr Low-field transport and mobility; piezoresistance

Long range resonant tunneling in quantum cascade structures

A. Buffaz, M. Carras, L. Doyennette, V. Trinité, X. Marcadet, and V. Berger

Appl. Phys. Lett. 96, 162103 (2010); http://dx.doi.org/10.1063/1.3399768 (3 pages) | Cited 5 times

Online Publication Date: 19 April 2010

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Tunneling transport in a quantum cascade detector is investigated. With regard to coherent transport in quantum cascade lasers, a Kazarinov–Suris approach R. F. Kazarinov and R. A. Suris, [Sov. Phys. Semicond. 6, 120 (1972)] needs to be modified through the introduction of an additional Fermi–Dirac factor in order to properly model the experimental data at low temperature. Electronic current is completely dominated by tunneling transport; the model here presented should help to suppress it in the future design of efficient quantum cascade detectors.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)

Effect of atomically controlled interfaces on Fermi-level pinning at metal/Ge interfaces

K. Yamane, K. Hamaya, Y. Ando, Y. Enomoto, K. Yamamoto, T. Sadoh, and M. Miyao

Appl. Phys. Lett. 96, 162104 (2010); http://dx.doi.org/10.1063/1.3368701 (3 pages) | Cited 14 times

Online Publication Date: 19 April 2010

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We study electrical properties of metal/Ge contacts with an atomically controlled interface, and compare them with those with a disordered one, where atomically controlled interfaces can be demonstrated by using Fe3Si/Ge(111) contacts. We find that the Schottky barrier height of Fe3Si/n-Ge(111) contacts is unexpectedly lower than those induced by the strong Fermi-level pinning at other metal/n-Ge contacts. For Fe3Si/p-Ge(111) contacts, we identify clear rectifying behavior in I-V characteristics at low temperatures, which is also different from I-V features due to the strong Fermi-level pinning at other metal/p-Ge contacts. These results indicate that there is an extrinsic contribution such as dangling bonds to the Fermi-level pinning effect at the directly connected metal/Ge contacts.
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73.40.Ns Metal-nonmetal contacts
73.20.At Surface states, band structure, electron density of states
71.55.-i Impurity and defect levels
73.30.+y Surface double layers, Schottky barriers, and work functions

Modeling of porous silicon junction field effect transistor gas sensors: Insight into NO2 interaction

G. Barillaro, G. M. Lazzerini, and L. M. Strambini

Appl. Phys. Lett. 96, 162105 (2010); http://dx.doi.org/10.1063/1.3391620 (3 pages) | Cited 2 times

Online Publication Date: 20 April 2010

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In this paper a lumped parameter electrical model for porous silicon junction field effect transistor (PSJFET) gas sensors is presented and experimentally validated. The PSJFET is an integrated p-channel JFET device modified with a porous silicon layer, the latter acting as sensing element. The model is described by using an analytical closed-form expression, which quantitatively links the sensor current to the analyte concentration in the environment, and validated by using experimental data of PSJFETs exposed to both synthetic air and NO2 with concentration of 300 ppb. Best fitting of experimental data with the proposed model allows one to get quantitative information on the effect of NO2 adsorption/desorption at the PS surface on electrical PS parameters, such as its conductance and surface charge density.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling

Electronic channels for acoustic transport in semiconductor heterostructures

K. Biermann, O. D. D. Couto, W. Seidel, R. Hey, and P. V. Santos

Appl. Phys. Lett. 96, 162106 (2010); http://dx.doi.org/10.1063/1.3407672 (3 pages) | Cited 3 times

Online Publication Date: 21 April 2010

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We demonstrate electronic waveguides for the ambipolar transport of electrons and holes by surface acoustic waves (SAWs) in buried (Al,Ga)As quantum well (QW) structures, which do not require deep-etching for their fabrication. They are defined by tailoring the SAW-induced piezoelectric potential in the QW plane using thin metal stripes deposited onto the piezoelectric cap layer of the QW sample. Acoustic transport experiments show the enhanced capture and acoustic transport of photoexcited carriers underneath the metallic surface stripes.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials
43.20.Mv Waveguides, wave propagation in tubes and ducts
85.35.Ds Quantum interference devices
73.23.-b Electronic transport in mesoscopic systems
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Gate-defined double quantum dot with integrated charge sensors realized in InGaAs/InP by incorporating a high-κ dielectric

Jie Sun, Marcus Larsson, Ivan Maximov, and H. Q. Xu

Appl. Phys. Lett. 96, 162107 (2010); http://dx.doi.org/10.1063/1.3409223 (3 pages) | Cited 3 times

Online Publication Date: 21 April 2010

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A gate-defined double quantum dot with two integrated quantum point contact charge sensors is realized in an InGaAs/InP heterostructure by employing a high-κ HfO2 thin film as gate dielectric and a polymer bridge technique. Clear honeycomb patterns are observed in the measured charge stability diagram of the double quantum dot and charge sensing signals of the quantum point contacts. It is also found that the quantum point contact charge sensors can detect the charge states in the double quantum dot even in the condition that the direct transport signal is not visible.
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Thermoelectric properties of polycrystalline In4Se3 and In4Te3

Xun Shi, Jung Y. Cho, James R. Salvador, Jihui Yang, and Hsin Wang

Appl. Phys. Lett. 96, 162108 (2010); http://dx.doi.org/10.1063/1.3389494 (3 pages) | Cited 16 times

Online Publication Date: 21 April 2010

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High thermoelectric performance of a single crystal layered compound In4Se3 was reported recently. We present here an electrical and thermal transport property study over a wide temperature range for polycrystalline samples of In4Se3 and In4Te3. Our data demonstrate that these materials are lightly doped semiconductors, leading to large thermopower and resistivity. Very low thermal conductivity, below 1 W/m K, is observed. The power factors for In4Se3 and In4Te3 are much smaller when compared with state-of-the-art thermoelectric materials. This combined with the very low thermal conductivity results in the maximum ZT value of less than 0.6 at 700 K for In4Se3.
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72.20.Pa Thermoelectric and thermomagnetic effects
72.80.Jc Other crystalline inorganic semiconductors
66.70.Df Metals, alloys, and semiconductors

Effect of surface passivation on generation and recombination lifetimes in silicon wafer studied by impedance spectroscopy

Sanjai Kumar, P. K. Singh, and S. R. Dhariwal

Appl. Phys. Lett. 96, 162109 (2010); http://dx.doi.org/10.1063/1.3385779 (3 pages) | Cited 2 times

Online Publication Date: 22 April 2010

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Impedance spectroscopy is used to study the effect of surface passivation on minority carrier lifetimes. The technique allows measurement of generation and recombination lifetimes separately. Induced p+-p-n structures are prepared by depositing semitransparent layers of high and low work function metals (Pd and Al, respectively) on the two sides of silicon wafers. Hydrogen adsorption property of Pd surface has been utilized for passivation. The generation lifetimes remain almost unaffected but recombination lifetimes enhance many folds after passivations which are in agreement with values obtained by microwave photoconductive decay technique after chemical passivation. Variations are analyzed for estimation of bulk recombination lifetime.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Cg Contact resistance, contact potential
68.43.Mn Adsorption kinetics

Band alignment at the BaCuSeF/ZnTe interface

Andriy Zakutayev, Janet Tate, Heather A. S. Platt, Douglas A. Keszler, Alireza Barati, Andreas Klein, and Wolfram Jaegermann

Appl. Phys. Lett. 96, 162110 (2010); http://dx.doi.org/10.1063/1.3405757 (3 pages) | Cited 2 times

Online Publication Date: 22 April 2010

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In situ photoemission spectroscopy experiments are used to characterize the interface between ZnTe and the wide band gap p-type semiconductor BaCuSeF. The contact is characterized by a null valence-band offset, a large conduction-band offset, and a chemically graded interface. By applying the transitivity rule for band offset and on the basis of similarities in chemical composition, BaCuSeF contact to chalcogenide photovoltaic absorber materials would be expected to have similar properties. By extension, BaCuChF (Ch = S,Se,Te) materials are suitable as p-layers in p-i-n double-heterojunction solar cells fabricated with CdTe, Cu(InGa)Se2, and Cu2ZnSnS4 absorbers.
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73.20.At Surface states, band structure, electron density of states
71.20.Nr Semiconductor compounds
79.60.Jv Interfaces; heterostructures; nanostructures
88.40.J- Types of solar cells
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