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23 Nov 2009

Volume 95, Issue 21, Articles (21xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 95, 213501 (2009); http://dx.doi.org/10.1063/1.3265958 (3 pages)

S. Cibella, M. Ortolani, R. Leoni, G. Torrioli, L. Mahler, Ji-Hua Xu, A. Tredicucci, H. E. Beere, and D. A. Ritchie
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Difference between penetration and damping lengths in photonic crystal mirrors

C. Sauvan, J. P. Hugonin, and P. Lalanne

Appl. Phys. Lett. 95, 211101 (2009); http://dx.doi.org/10.1063/1.3266840 (3 pages) | Cited 3 times

Online Publication Date: 23 November 2009

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Different mirror geometries in two-dimensional photonic crystal slabs are studied with fully vectorial calculations. We compare their optical properties and, in particular, we show that, for heterostructure mirrors, the penetration length associated with the delay induced by distributed reflection is not correlated with the characteristic damping length of the electromagnetic energy distribution in the mirror. This unexpected result evidences that the usual trade-off between short damping lengths and large penetration lengths that is classically encountered in distributed Bragg reflectors can be overcome with carefully designed photonic crystal structures.
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42.79.Bh Lenses, prisms and mirrors
42.15.Eq Optical system design
42.70.Qs Photonic bandgap materials

Ultrafast carrier mobilities in high-resistivity iron-doped Ga0.69In0.31As photoconducting antennas

Suranjana Sengupta, Ingrid Wilke, and Partha. S. Dutta

Appl. Phys. Lett. 95, 211102 (2009); http://dx.doi.org/10.1063/1.3265734 (3 pages)

Online Publication Date: 23 November 2009

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We report measurements of terahertz (THz) frequency radiation pulses emitted by photoconducting (PC) antennas fabricated from high-resistivity Fe-doped Ga0.69In0.31As. The Ga0.69In0.31As:Fe was grown using a hybrid vertical Bridgman and gradient freezing directional solidification process. GaxIn1−xAs crystals were uniformly doped with Fe atoms to obtain high-resistivity ( ∼ 107 Ω cm). The ultrafast carrier mobility in this material is about three orders of magnitude higher than in GaxIn1−xAs thin films grown by molecular beam epitaxy. The bandgap of Ga0.69In0.31As:Fe is low enough ( ∼ 1 eV) to use compact Yb-based multiwatt lasers operating at 1.1 μm for photoexcitation of Ga0.69In0.31As based PC antennas for high power THz emission.
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73.61.Ey III-V semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
81.05.Ea III-V semiconductors
81.10.Fq Growth from melts; zone melting and refining
84.40.Ba Antennas: theory, components and accessories
61.72.U- Doping and impurity implantation
72.40.+w Photoconduction and photovoltaic effects

Defect selective passivation in GaN epitaxial growth and its application to light emitting diodes

M.-H. Lo, P.-M. Tu, C.-H. Wang, Y.-J. Cheng, C.-W. Hung, S.-C. Hsu, H.-C. Kuo, H.-W. Zan, S.-C. Wang, C.-Y. Chang, and C.-M. Liu

Appl. Phys. Lett. 95, 211103 (2009); http://dx.doi.org/10.1063/1.3266859 (3 pages) | Cited 4 times

Online Publication Date: 24 November 2009

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A defect selective passivation method to block the propagation of threading dislocations in GaN epitaxial growth is demonstrated. The defect selective passivation is done by using defect selective chemical etching to locate defect sites, followed by silicon oxide passivation of the etched pits, and epitaxial over growth. The threading dislocation density in the regrown epilayer is significantly improved from 1×109 to 4×107 cm−2. The defect passivated epiwafer is used to grow light emitting diode and the output power of the fabricated chip is enhanced by 45% at 20 mA compared to a reference one without using defect passivation.
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85.60.Jb Light-emitting devices
81.65.Rv Passivation

High spontaneous emission rate asymmetrically graded 480 nm InGaN/GaN quantum well light-emitting diodes

Lei Wang, Rui Li, Ziwen Yang, Ding Li, Tao Yu, Ningyang Liu, Lei Liu, Weihua Chen, and Xiaodong Hu

Appl. Phys. Lett. 95, 211104 (2009); http://dx.doi.org/10.1063/1.3266866 (3 pages) | Cited 8 times

Online Publication Date: 24 November 2009

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Spontaneous emission property of an asymmetrically graded 480 nm InGaN/GaN quantum well (QW) is investigated via k⋅p theory. Comparing to rectangular QW, band profiles of the graded QW change into parabolalike due to the variation of internal piezoelectric field along the growth direction, and the spontaneous emission rates of the graded QW are three times larger than rectangular case under various carrier densities. This can be attributed to the fact that the graded QW has much larger matrix element (Me)nmσ(kt) than rectangular QW considering that the wave function overlap of the graded QW is less affected by the quantum confined Stark effect.
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85.60.Jb Light-emitting devices
78.67.De Quantum wells
72.20.-i Conductivity phenomena in semiconductors and insulators

Tunable long-range surface plasmon polaritons taking advantage of nonlinear surface waves

Weiwei Shao, Lin Li, Weiwu Liu, Tianhao Zhang, Huihui Ma, Jingjun Xu, and Jianguo Tian

Appl. Phys. Lett. 95, 211105 (2009); http://dx.doi.org/10.1063/1.3267052 (3 pages) | Cited 2 times

Online Publication Date: 24 November 2009

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We present an improved Kretschmann configuration with nonlinear dielectric as substrate, in which long-range surface plasmon polaritons (SPPs) may appear, the modes and propagation lengths are tunable. We numerically simulated the solutions of SPP modes and their propagations. The results show that the SPP propagation length can range from tens of micrometers to tens of centimeters or even longer. The configuration proposed in this letter makes a breakthrough of the intrinsic restriction in conventional Kretschmann configuration and there exist the continuous steady SPP modes also in the range of k0ε31/2>β>k0ε11/2. It allows for optimization of SPP properties and makes SPP application more flexible in practices.
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71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

High-speed tuning of visible laser wavelength using a nanoimprinted grating optical tunable filter

Nien-Tsu Huang, Steven C. Truxal, Yi-Chung Tung, Amy Hsiao, Shuichi Takayama, and Katsuo Kurabayashi

Appl. Phys. Lett. 95, 211106 (2009); http://dx.doi.org/10.1063/1.3267083 (3 pages)

Online Publication Date: 24 November 2009

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We report on a microelectromechanical tunable optical filter incorporating strain-tunable nanoimprinted elastomeric grating with a pitch varied by 18%. This device enables tuning of optical fiber-guided laser wavelength between λ = 473 and 532 nm within 0.5 ms by mechanically modulating the pitch with a silicon microactuator. We also demonstrate the use of the device for obtaining two-color images of live/dead-stained cells with the color intensity ratio varied by the actuator voltage applied. The small structure of the device integrated on a silicon chip may be used in portable systems for optical switching and spectroscopy.
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42.55.Wd Fiber lasers
42.79.Ci Filters, zone plates, and polarizers
42.79.Dj Gratings
42.65.-k Nonlinear optics

Electrically driven ultraviolet lasing behavior from phosphorus-doped p-ZnO nanonail array/n-Si heterojunction

Jun-Yan Zhang, Qi-Feng Zhang, Tian-Song Deng, and Jin-Lei Wu

Appl. Phys. Lett. 95, 211107 (2009); http://dx.doi.org/10.1063/1.3268438 (3 pages) | Cited 19 times

Online Publication Date: 25 November 2009

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Electrically driven ultraviolet lasing behavior from p-ZnO:P nanonail array/n-Si heterojunction was demonstrated. Phosphorus-doped ZnO nanonail arrays were grown by chemical vapor deposition method. The constructed heterojunction with indium tin oxide films as the contacted electrodes demonstrated clear rectifying behavior, and the turn-on voltage was about 2.5 V. The p-n junction lowered the excitation threshold effectively and the electrically driven ultraviolet lasing behavior exhibited high monochromaticity: when the applied forward current reached 24 mA, distinct ultraviolet laser emission peaks were obtained at room temperature, and the full width at half maxims were 0.7, 0.9, and 0.5 nm, respectively. The three sharp peaks represented different lasing modes.
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42.55.Px Semiconductor lasers; laser diodes
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.16.-c Methods of micro- and nanofabrication and processing
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.40.Ei Rectification
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Atmospheric pressure argon plasma jet using a cylindrical piezoelectric transformer

Hyun Kim, Albrecht Brockhaus, and Jürgen Engemann

Appl. Phys. Lett. 95, 211501 (2009); http://dx.doi.org/10.1063/1.3267142 (3 pages) | Cited 11 times

Online Publication Date: 24 November 2009

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A low-voltage atmospheric pressure nonthermal argon plasma jet using a circular piezoelectric transducer is proposed. An Ar plasma flame is generated at an input voltage of 87 V. The consumed power is 2 W. The electrical and optical properties of the jet are analyzed. In particular, the transient Ar discharge ignition and evolution including the so-called plasma bullet phenomenon is examined temporally resolved with the aid of a fast camera. It is found that four discharge phases can be identified, designated as ignition, extension, self-propagation, and attenuation. The plasma bullet is launched while the electric field in the discharge space is decreasing. The average bullet velocity is 23 km/s.
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52.75.-d Plasma devices
52.80.-s Electric discharges
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Lattice softening for producing ultrahigh strength of iron base nanocrystalline alloy

S. Kuramoto, T. Furuta, N. Nagasako, and Z. Horita

Appl. Phys. Lett. 95, 211901 (2009); http://dx.doi.org/10.1063/1.3266832 (3 pages) | Cited 3 times

Online Publication Date: 24 November 2009

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One can increase the strength of metallic materials by pinning dislocations with nanoscale obstacles, as the dislocations facilitate plastic deformation. However, simultaneous achievement of the ultrahigh strength and the ductility is extremely difficult in conventional metallic materials. Here we show that the ultrahigh strength iron base alloy with enhanced ductility, whose strength is approaching ideal strength and being twice as much as the upper limit of conventional alloys, can be realized by introducing the paradox concept of lattice softening. Designing atomic arrangement with specific electronic structure creates the lattice softening, and a nanograined structure is then produced by subsequent processing with severe plastic deformation.
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81.40.Lm Deformation, plasticity, and creep
62.20.fk Ductility, malleability
73.22.-f Electronic structure of nanoscale materials and related systems
61.72.Lk Linear defects: dislocations, disclinations

Spatially resolved investigations of the emission around 3.31 eV (A-line) from ZnO nanocrystals

S. S. Kurbanov, G. N. Panin, and T. W. Kang

Appl. Phys. Lett. 95, 211902 (2009); http://dx.doi.org/10.1063/1.3264084 (3 pages) | Cited 3 times

Online Publication Date: 24 November 2009

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ZnO nanocrystals grown by chemical solution deposition were studied by means of photoluminescence and cathodoluminescence spectroscopy. A postgrown annealing treatment significantly improved the UV emission efficiency and resulted in the clear appearance of a low temperature emission band around 3.31 eV (so-called A-line). Spatially and wavelength resolved cathodoluminescence measurements revealed a spotlike distribution of the A-line emission on a nanocrystal surface. It is found that there is a strong correlation between the emission around 3.31 eV and the specklike defects on the nanocrystal surface that appeared after annealing. The origin of the A-line and the specklike defects are discussed.
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81.07.Bc Nanocrystalline materials
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
81.16.-c Methods of micro- and nanofabrication and processing
78.55.Et II-VI semiconductors
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
61.72.J- Point defects and defect clusters
81.40.Gh Other heat and thermomechanical treatments
78.60.Hk Cathodoluminescence, ionoluminescence

Damping of surface acoustic vibration induced by electrons trapped on SnO2 nanocrystal surface

F. Gao, T. H. Li, X. L. Wu, Y. C. Cheng, J. C. Shen, and Paul K. Chu

Appl. Phys. Lett. 95, 211903 (2009); http://dx.doi.org/10.1063/1.3266870 (3 pages) | Cited 5 times

Online Publication Date: 24 November 2009

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Broad full widths of half maxima (dampings) are observed from the low-frequency Raman spectra of hydrothermally prepared SnO2 nanocrystal congeries. No matrix exists between these nanocrystals and the complex-frequency model is thus unable to explain the damping in the low-frequency Raman peaks. An alternative model in which damping is induced by the interaction between confined surface acoustic vibrations and localized electrons near the nanocrystal surface is proposed to explain the phenomenon. This model which suggests that damping is proportional to d−3/2, where d is the average diameter of nanocrystals, is corroborated by our experimental results.
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68.35.Iv Acoustical properties
68.35.Ja Surface and interface dynamics and vibrations
81.07.Bc Nanocrystalline materials
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
63.22.Kn Clusters and nanocrystals
78.30.Hv Other nonmetallic inorganics

Near-field evidence of local polarized emission centers in InGaN/GaN materials

Ruggero Micheletto, Maria Allegrini, and Yoichi Kawakami

Appl. Phys. Lett. 95, 211904 (2009); http://dx.doi.org/10.1063/1.3265732 (3 pages) | Cited 1 time

Online Publication Date: 24 November 2009

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We study the optical polarization properties of confined structures in InGaN/GaN single quantum well devices. Using a near-field optical setup we investigated the photoluminescence maps with a polarization-modulation method. If the optical emissions have a preferred polarization orientation, our apparatus yields a signal that is proportional to the degree of polarization. We could demonstrate that within the quantum well there are localized submicrometer centers that emit strongly oriented light. This points toward the existence of quantum-dot like confined asymmetric domains hidden within the quantum well.
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85.30.-z Semiconductor devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Soft recovery technique to investigate dynamic fragmentation of laser shock-loaded metals

E. Lescoute, T. De Rességuier, J.-M. Chevalier, M. Boustie, J.-P. Cuq-Lelandais, and L. Berthe

Appl. Phys. Lett. 95, 211905 (2009); http://dx.doi.org/10.1063/1.3268437 (3 pages) | Cited 3 times

Online Publication Date: 25 November 2009

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With the development of high energy laser facilities dedicated to inertial confinement fusion, the question of debris ejection from metallic shells subjected to intense laser irradiation has become a key issue. We have used two diagnostics to investigate fragmentation processes. Recovery of ejected fragments has been performed in a highly transparent gel of density 0.9 g/cm3. Fragments sizes, shapes, and penetration depths, can be easily observed with a spatial resolution of micrometer-order. Complementary data are provided by transverse shadowgraphy which allows to obtain quasi-instantaneous, successive pictures of the debris clouds and mean ejection velocities.
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52.57.-z Laser inertial confinement
79.20.Ds Laser-beam impact phenomena
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
62.50.Ef Shock wave effects in solids and liquids
82.70.Gg Gels and sols

Nanocrystalline tungsten carbide: As incompressible as diamond

Zhijun Lin, Lin Wang, Jianzhong Zhang, Ho-kwang Mao, and Yusheng Zhao

Appl. Phys. Lett. 95, 211906 (2009); http://dx.doi.org/10.1063/1.3268457 (3 pages) | Cited 9 times

Online Publication Date: 25 November 2009

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We investigate the compressibility of nanocrystalline tungsten carbide (nano-WC) using synchrotron x-ray diffraction. Nano-WC displays a bulk modulus (452 GPa) comparable to that of diamond; it is 10%–15% larger than previously reported values for bulk WC. This finding is consistent with a generalized model of nanocrystal with a compressed surface layer. The linear bulk moduli of nano-WC along a- and c-axes were determined to be 407 and 546 GPa, respectively. First-principles density functional theory (DFT) calculations confirm the experimental observations of an anisotropic linear compressibility and a lower bulk modulus for microsized WC.
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81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.de Elastic moduli
62.23.-c Structural classes of nanoscale systems

Surface transformation and inversion domain boundaries in gallium nitride nanorods

Pan Xiao, Xu Wang, Jun Wang, Fujiu Ke, Min Zhou, and Yilong Bai

Appl. Phys. Lett. 95, 211907 (2009); http://dx.doi.org/10.1063/1.3268467 (3 pages) | Cited 6 times

Online Publication Date: 25 November 2009

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Phase transformation and subdomain structure in [0001]-oriented gallium nitride (GaN) nanorods of different sizes are studied using molecular dynamics simulations. The analysis concerns the structure of GaN nanorods at 300 K without external loading. Calculations show that a transformation from wurtzite to a tetragonal structure occurs along {01math0} lateral surfaces, leading to the formation of a six-sided columnar inversion domain boundary (IDB) in the [0001] direction of the nanorods. This structural configuration is similar to the IDB structure observed experimentally in GaN epitaxial layers. The transformation is significantly dependent on the size of the nanorods.
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61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
61.43.Bn Structural modeling: serial-addition models, computer simulation
68.35.Rh Phase transitions and critical phenomena
64.70.K- Solid-solid transitions

Excitonic characteristics in direct wide-band-gap CuScO2 epitaxial thin films

H. Hiraga, T. Makino, T. Fukumura, A. Ohtomo, and M. Kawasaki

Appl. Phys. Lett. 95, 211908 (2009); http://dx.doi.org/10.1063/1.3268476 (3 pages) | Cited 4 times

Online Publication Date: 25 November 2009

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Thin films of a delafossite compound CuScO2 were grown on spinel MgAl2O4 (111) substrates, yielding in highly crystalline and (0001)-oriented epitaxial structures. Absorption spectra at 20 K revealed a sharp exciton resonance at 3.97 eV, which persisted up to 300 K. Its direct transition band gap at 20 K and exciton binding energies were determined to be about 4.35 and 380 meV, both of which are considerably larger than those of ZnO. In view of its capability of naturally layered structure and p-type doping, this compound will be interesting for exciton physics as well as implementation of heterostructured devices.
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71.35.-y Excitons and related phenomena
71.20.Ps Other inorganic compounds
68.55.aj Insulators
81.15.Fg Pulsed laser ablation deposition
78.66.Nk Insulators
78.40.Ha Other nonmetallic inorganics
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High electron mobility and low sheet resistance in lattice-matched AlInN/AlN/GaN/AlN/GaN double-channel heterostructure

S. Zhang, M. C. Li, Z. H. Feng, B. Liu, J. Y. Yin, and L. C. Zhao

Appl. Phys. Lett. 95, 212101 (2009); http://dx.doi.org/10.1063/1.3264961 (3 pages) | Cited 6 times

Online Publication Date: 23 November 2009

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High electron mobility and low sheet resistance were achieved in lattice-matched AlInN/AlN/GaN/AlN/GaN double-channel (DC) heterostructure. Two-dimensional electron gas (2DEG) of the DC heterostructure was divided into the double channels and the room-temperature mobility was increased to 1430 cm2/V s by reducing the 2DEG density in each channel, compared with low electron mobility (1090 cm2/V s) for lattice-matched AlInN/AlN/GaN single-channel heterostructure. It was found that the 2DEG mobility was limited by thickness of the AlN interlayer between the double channels. After the structure optimization, the room temperature electron mobility of the DC heterostructure reached 1570 cm2/V s with sheet resistance of 222 Ω/◻.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.Fr Low-field transport and mobility; piezoresistance
73.63.Hs Quantum wells
73.21.Fg Quantum wells

Investigation on GaAs surface treated with dimethylaluminumhydride

Hong-Liang Lu, Xiao-Liang Wang, Masakazu Sugiyama, and Yukihiro Shimogaki

Appl. Phys. Lett. 95, 212102 (2009); http://dx.doi.org/10.1063/1.3268450 (3 pages) | Cited 3 times

Online Publication Date: 24 November 2009

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The reduction and removal of surface native oxides from as-degreased and HCl-treated GaAs substrates using dimethylaluminumhydride (DMAH) have been studied by x-ray photoelectron spectroscopy. It is revealed that higher oxide states are more easily removed from the GaAs surface after exposure to DMAH at 300 °C. Complete consumption of native oxides on HCl-treated GaAs surface has been realized with 10 s DMAH exposure. In addition, the metallization of the Al–O bonding with increase of DMAH exposure confirms the reduction of native oxides on GaAs.
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81.65.-b Surface treatments
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Type I/type II band alignment transition in strained PbSe/PbEuSeTe multiquantum wells

M. Simma, T. Fromherz, G. Bauer, and G. Springholz

Appl. Phys. Lett. 95, 212103 (2009); http://dx.doi.org/10.1063/1.3263722 (3 pages) | Cited 2 times

Online Publication Date: 24 November 2009

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Investigation of the optical transitions in tensily strained PbSe/PbEuSeTe multiquantum wells by differential transmission spectroscopy reveals a type I/type II band alignment transition due to strain-induced lowering of the band edge energies of the quantum wells. From the measured shifts of the optical transitions the optical deformation potentials of PbSe are obtained. This is crucial for realistic modeling of the electronic properties of strained PbSe heterostructures.
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73.21.Fg Quantum wells
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
71.20.Nr Semiconductor compounds

Carrier lifetime measurements in short-period InAs/GaSb strained-layer superlattice structures

Dmitry Donetsky, Stefan P. Svensson, Leonid E. Vorobjev, and Gregory Belenky

Appl. Phys. Lett. 95, 212104 (2009); http://dx.doi.org/10.1063/1.3267103 (3 pages) | Cited 25 times

Online Publication Date: 24 November 2009

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Minority carrier lifetime and interband absorption in midinfrared range of spectra were measured in InAs/GaSb strained-layer superlattices (SLSs) grown by molecular beam epitaxy on GaSb substrates. The carrier lifetime in 200-period undoped 7 ML InAs/8 ML GaSb SLS with AlSb carrier confinement layers was determined by time-resolved photoluminescence (PL) and from analysis of PL response to sinwave-modulated excitation. Study of PL kinetics in frequency domain allowed for direct lifetime measurements with the excess carrier concentration level of 3.5×1015 cm−3. The minority carrier lifetime of 80 ns at T = 77 K was obtained from dependence of the carrier lifetime on excitation power.
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73.63.-b Electronic transport in nanoscale materials and structures
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.55.Cr III-V semiconductors
73.21.Cd Superlattices

Interfacial layer dependence on device property of high-κ TiLaO Ge/Si N-type metal-oxide-semiconductor capacitors at small equivalent-oxide thickness

W. B. Chen and Albert Chin

Appl. Phys. Lett. 95, 212105 (2009); http://dx.doi.org/10.1063/1.3265947 (3 pages) | Cited 11 times

Online Publication Date: 24 November 2009

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We have investigated the device property dependence of high dielectric-constant (high-κ) TiLaO epitaxial-Ge/Si n-type metal-oxide-semiconductor (n-MOS) capacitors on different GeO2 and SiO2 interfacial layers. Large capacitance density of 3.3 μF/cm2, small equivalent-oxide thickness (EOT) of 0.81 nm and small C-V hysteresis of 19 mV are obtained simultaneously for MOS capacitor using ultrathin SiO2 interfacial layer, while the device with ultrathin interfacial GeO2 shows inferior performance of larger 1.1 nm EOT and poor C-V hysteresis of 93 mV. From cross-sectional transmission electron microscopy, secondary ion mass spectroscopy, and x-ray photoelectron spectroscopy analysis, the degraded device performance using GeO2 interfacial layer is due to the severe Ge outdiffusion, thinned interfacial GeO2 and thicker gate dielectric after 550 °C rapid-thermal anneal.
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84.32.Tt Capacitors
79.60.Jv Interfaces; heterostructures; nanostructures
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Thermoelectric properties and anisotropic electronic band structure on the In4Se3−x compounds

Jong-Soo Rhyee, Eunseog Cho, Kyu Hyoung Lee, Sang Mock Lee, Sang Il Kim, Hyun-Sik Kim, Yong Seung Kwon, and Sung Jin Kim

Appl. Phys. Lett. 95, 212106 (2009); http://dx.doi.org/10.1063/1.3266579 (3 pages) | Cited 20 times

Online Publication Date: 25 November 2009

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We report the high thermoelectric figure-of-merit (ZT) on the Se-deficient polycrystalline compounds of In4Se3−x (0.02 ≤ x ≤ 0.5) and the anisotropic electronic band structure. The Se-deficiency (x) has the effect of decreasing the semiconducting band gap and increasing the power factor. The band structure calculation for In4Se3−x (x = 0.25) exhibits localized hole bands at the Γ-point and Y-S symmetry line, whereas the significant electronic band dispersion is observed along the c-axis. Here, we propose that the high ZT values on those compounds are originated from the anisotropic electronic band structure as well as Peierls distortion.
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72.20.Pa Thermoelectric and thermomagnetic effects
71.20.Nr Semiconductor compounds
71.45.Lr Charge-density-wave systems
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Probing magnetic singularities during magnetization process in FePd films

Aurélien Masseboeuf, Thomas Jourdan, Frédéric Lançon, Pascale Bayle-Guillemaud, and Alain Marty

Appl. Phys. Lett. 95, 212501 (2009); http://dx.doi.org/10.1063/1.3266825 (3 pages)

Online Publication Date: 24 November 2009

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We report the use of Lorentz microscopy to observe the domain wall structure during the magnetization process in iron-palladium thin foils. We have focused on the magnetic structure of domain walls of bubble-shaped magnetic domains near saturation. Regions are found along the domain walls where the magnetization abruptly reverses. Multiresolution magnetic simulations showed that these regions are vertical Bloch lines (VBL) and that the different bubble shapes observed are related to the inner structure of the VBL. Combining these two complementary methods, we were thus able to probe the presence of magnetic singularities as small as Bloch points in the inner magnetization of the domain walls.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)

Effects of combined current injection and laser irradiation on Permalloy microwire switching

J. H. Franken, P. Möhrke, M. Kläui, J. Rhensius, L. J. Heyderman, J.-U. Thiele, H. J. M. Swagten, U. J. Gibson, and U. Rüdiger

Appl. Phys. Lett. 95, 212502 (2009); http://dx.doi.org/10.1063/1.3265944 (3 pages) | Cited 3 times

Online Publication Date: 24 November 2009

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Combined field- and current-induced domain wall (DW) motion in Permalloy microwires is studied using fast magneto-optical Kerr-microscopy. On increasing the current density, we find a decrease of Kerr signal contrast, corresponding to a reduction in the magnetization, which is attributed to Joule heating of the sample. Resistance measurements on samples with varying substrates confirm that the Curie temperature is reached when the magneto-optical contrast vanishes and reveal the importance of the heat flow into the substrate. By tuning the laser power, DWs can be pinned in the laser spot, which can thus act as a flexible pinning site for DW devices.
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
75.78.Fg Dynamics of domain structures
75.60.Ch Domain walls and domain structure
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
78.20.Ls Magneto-optical effects
72.80.Ga Transition-metal compounds

Electric field control of magnetoresistance in a lateral InAs quantum well spin valve

Hyun Kum, Debashish Basu, Pallab Bhattacharya, and Wei Guo

Appl. Phys. Lett. 95, 212503 (2009); http://dx.doi.org/10.1063/1.3268432 (3 pages) | Cited 4 times

Online Publication Date: 25 November 2009

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The control of magnetoresistance of a lateral spin valve with bias applied to a gate placed outside the channel region is demonstrated. The spin valve channel consists of an InAs/In0.53Ga0.47As/In0.52Al0.48As two-dimensional electron gas lattice matched to (001) InP. The polarizer and analyzer contacts are made with 35 nm type B MnAs/In0.52Al0.48As Schottky tunnel barriers. The magnetoresistance changes from 0.14% to 4% at 10 K in a device in which the spin transport is in the direction of magnetization of the polarizer and analyzer contacts. The effect is absent in a GaAs channel spin valve and other control devices indicating that the change in magnetoresistance is due to Rashba spin-orbit coupling.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Cc Other ferromagnetic metals and alloys
72.25.-b Spin polarized transport
72.20.My Galvanomagnetic and other magnetotransport effects
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