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4 Nov 2002

Volume 81, Issue 19, pp. 3519-3685

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Strong exciton–photon coupling in a low-Q all-metal mirror microcavity

P. A. Hobson, W. L. Barnes, D. G. Lidzey, G. A. Gehring, D. M. Whittaker, M. S. Skolnick, and S. Walker

Appl. Phys. Lett. 81, 3519 (2002); http://dx.doi.org/10.1063/1.1517714 (3 pages) | Cited 56 times

Online Publication Date: 28 October 2002

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We report the experimental observation of strong exciton–photon coupling in a planar microcavity composed of an organic semiconductor positioned between two metallic (silver) mirrors. Via transmission and reflectivity measurements, we observe a very large, room temperature Rabi splitting in excess of 300 meV. We show that the Rabi-splitting is enhanced in all-metal microcavities by a factor of more than 2 compared to an organic film positioned between a silver mirror and a dielectric mirror. This enhancement results from the significantly larger optical fields that are confined within all-metal microcavities. © 2002 American Institute of Physics.
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63.20.kk Phonon interactions with other quasiparticles
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
42.82.Gw Other integrated-optical elements and systems

Direct-UV-written buried channel waveguide lasers in direct-bonded intersubstrate ion-exchanged neodymium-doped germano-borosilicate glass

Corin B. E. Gawith, Alexander Fu, Tajamal Bhutta, Ping Hua, David P. Shepherd, Elizabeth R. Taylor, Peter G. R. Smith, Daniel Milanese, and Monica Ferraris

Appl. Phys. Lett. 81, 3522 (2002); http://dx.doi.org/10.1063/1.1519103 (3 pages) | Cited 6 times

Online Publication Date: 28 October 2002

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We report a technique for producing single-mode buried channel waveguide lasers in neodymium-doped SiO2:GeO2:B2O3:Na2O (SGBN) glass. Direct bonding forms the basis of this process, providing a buried waveguide layer in the photosensitive SGBN material into which channel confinement can be directly written with a focused UV beam. Characterization of a 7.5-mm-long device was performed using a Ti:Sapphire laser operating at 808 nm and the resultant 1059 nm channel waveguide laser output exhibited single-mode operation, milliwatt-order lasing thresholds, and propagation losses of <0.3 dB cm−1. © 2002 American Institute of Physics.
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42.60.By Design of specific laser systems
42.55.Rz Doped-insulator lasers and other solid state lasers
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.79.Gn Optical waveguides and couplers
42.70.Hj Laser materials
81.05.Kf Glasses (including metallic glasses)
42.70.Ce Glasses, quartz

Coherent integration of 0.5 GHz spectral holograms at 1536 nm using dynamic biphase codes

Z. Cole, T. Böttger, R. Krishna Mohan, R. Reibel, W. R. Babbitt, R. L. Cone, and K. D. Merkel

Appl. Phys. Lett. 81, 3525 (2002); http://dx.doi.org/10.1063/1.1518152 (3 pages) | Cited 28 times

Online Publication Date: 28 October 2002

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Spectral hole-burning-based optical processing devices are proposed for coherent integration of multiple high-bandwidth interference patterns in a spectral hole-burning medium. In this implementation, 0.5 GHz spectral holographic gratings are dynamically accumulated in Er3+:Y2SiO5 at 4.2 K using a 1536 nm laser frequency stabilized to a spectral hole, along with commercial off-the-shelf components. The processed data, representing time delays over 0.5–2.0 μs, were optically read out using a frequency-swept probe; this approach makes possible the use of low-bandwidth, large-dynamic-range detectors and digitizers and enables competitive processing for applications such as radar, lidar, and radio astronomy. Coherent integration dynamics and material advances are reported. © 2002 American Institute of Physics.
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42.40.Eq Holographic optical elements; holographic gratings
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
42.50.Hz Strong-field excitation of optical transitions in quantum systems; multiphoton processes; dynamic Stark shift

Small molecule organic light-emitting diodes can exhibit high performance without conventional hole transport layers

Qinglan Huang, Ji Cui, He Yan, Jonathan G. C. Veinot, and Tobin J. Marks

Appl. Phys. Lett. 81, 3528 (2002); http://dx.doi.org/10.1063/1.1517397 (3 pages) | Cited 21 times

Online Publication Date: 28 October 2002

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It is generally accepted that hole transport layers (HTLs) with thicknesses on the order of tens of nm are indispensable to the function of small molecule organic light-emitting diodes (OLEDs) if high electroluminescence and quantum efficiencies are to be achieved. In the present letter, small molecule OLEDs with high luminance and external quantum efficiencies are fabricated in which the HTL is replaced solely by an ultrathin (1–2 nm) self–assembled, saturated hydrocarbon organosiloxane monolayer. These results require some reconsideration of conventional design criteria regarding the necessity of HTLs and argue that the role of the self-assembled monolayer here is to enhance hole injection and charge recombination efficiency, while blocking electron transport to the anode. These results therefore offer significantly simplified device fabrication. © 2002 American Institute of Physics.
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85.60.Jb Light-emitting devices
81.16.Dn Self-assembly

All-optical excitation and detection of microelectrical-mechanical systems

J. E. Graebner, S. Pau, and P. L. Gammel

Appl. Phys. Lett. 81, 3531 (2002); http://dx.doi.org/10.1063/1.1519351 (3 pages) | Cited 9 times

Online Publication Date: 28 October 2002

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The radiation pressure of a chopped, 3 mW optical beam is used to excite angular motion of a Microelectrical-mechanical-systems’ (MEMS) mirror at its resonant frequencies. The modes are identified with a scanning interferometer, providing an all-optical excitation/detection scheme. The resonant frequencies, mode distributions, spring constants, and coupling between adjacent MEMS devices can, therefore, be studied without the use of electrostatic or other types of actuation. Within the experimental error of ∼30%, the amplitude of angular oscillation is equal to the theoretical value expected for radiation pressure. © 2002 American Institute of Physics.
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37.10.Vz Mechanical effects of light on atoms, molecules, and ions
42.79.Bh Lenses, prisms and mirrors
42.65.Pc Optical bistability, multistability, and switching, including local field effects
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Amplified spontaneous emission and efficient tunable laser emission from a substituted thiophene-based oligomer

Dario Pisignano, Marco Anni, Giuseppe Gigli, Roberto Cingolani, Margherita Zavelani-Rossi, Guglielmo Lanzani, Giovanna Barbarella, and Laura Favaretto

Appl. Phys. Lett. 81, 3534 (2002); http://dx.doi.org/10.1063/1.1519735 (3 pages) | Cited 41 times

Online Publication Date: 28 October 2002

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We investigated gain and lasing in spin-coated films of a soluble substituted oligothiophene. With increasing excitation power, the photoluminescence spectra show a clear line narrowing due to amplified spontaneous emission. We measure a low threshold (20 μJ cm−2) for line narrowing and a large gain cross section (6×10−16 cm2), indicating that this molecule is a promising active material for organic solid-state lasers. As a demonstrator, we realize a transverse electromagnetic (TEM00) single-mode laser with tunable emission from the yellow to the red (a range of 37 nm), with a pump threshold as low as 18 μJ cm−2 and efficiency of 1.9%. These results are among the best so far reported for organic lasers. © 2002 American Institute of Physics.
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42.70.Hj Laser materials
42.55.Rz Doped-insulator lasers and other solid state lasers
78.45.+h Stimulated emission
42.70.Jk Polymers and organics
78.55.Kz Solid organic materials
42.60.Fc Modulation, tuning, and mode locking
78.66.Qn Polymers; organic compounds

Inhomogeneous nanoscale polymer-dispersed liquid crystals with gradient refractive index

Hongwen Ren and Shin-Tson Wu

Appl. Phys. Lett. 81, 3537 (2002); http://dx.doi.org/10.1063/1.1519102 (3 pages) | Cited 37 times

Online Publication Date: 28 October 2002

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Inhomogeneous polymer-dispersed liquid crystal devices having gradient droplet distribution were fabricated and their phase retardation characterized. The gradient refractive index profile can be used as switchable prism gratings, and positive and negative lenses with tunable focal lengths. Such a tunable electronic lens is a broadband device and can be used for unpolarized light. © 2002 American Institute of Physics.
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42.70.Df Liquid crystals
42.65.Pc Optical bistability, multistability, and switching, including local field effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.79.Bh Lenses, prisms and mirrors
42.82.Cr Fabrication techniques; lithography, pattern transfer

High-efficiency organic light-emitting diodes with tunable light emission by using aromatic diamine/5,6,11,12-tetraphenylnaphthacene multiple quantum wells

Yong Qiu, Yudi Gao, Liduo Wang, Peng Wei, Lian Duan, Deqiang Zhang, and Guifang Dong

Appl. Phys. Lett. 81, 3540 (2002); http://dx.doi.org/10.1063/1.1519348 (3 pages) | Cited 37 times

Online Publication Date: 28 October 2002

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Organic light-emitting diodes (OLEDs) with multiple-quantum-well (MQW) structures, which consist of N, N′-bis-(1-naphthyl)-N, N′-diphenyl-1, 1′ biphenyl 4, 4′-diamine and 5,6,11,12-tetraphenylnaphthacene (rubrene), and tris(8-hydroxyquinoline) aluminum (Alq3) as the electron transporting material, have been fabricated. The results demonstrate that the MQW structure can sharply increase the performance of OLEDs. The diode with a MQW number of 4 exhibits efficiency up to 8.1 cd/A, which is four times that of the conventional diodes without the MQW structure. It is also interesting to find that the light emission from Alq3 and rubrene can be obtained together and the electroluminescent spectrum, which is independent of the driving voltage, varies with the well number. For the device with a well number of 6, pure rubrene light emission is obtained. Our work demonstrates that the organic MQW structure not only can efficiently control the carrier transporting, thus conducive to achieve an electron–hole balance, but also help to adjust the emitting zone in the devices, then providing an option to obtain different emission colors. © 2002 American Institute of Physics.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
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How to affect stacking fault energy and structure by atom relaxation

J. Cai, C. Lu, P. H. Yap, and Y. Y. Wang

Appl. Phys. Lett. 81, 3543 (2002); http://dx.doi.org/10.1063/1.1519106 (3 pages) | Cited 7 times

Online Publication Date: 28 October 2002

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By a simulated annealing method with a parameterized tight-binding potential, the properties of structure and energy of a generalized stacking fault are investigated. It is shown that for metal Pd, the second-layer spacing from the stacking fault plane expands initially and then contracts with the variation of the stacking fault variable from 0 to 1. The effect of atom relaxation on stacking fault energy is shown to be small. For another metal Pt, the second-layer spacing contracts and the effect of atom relaxation on the stacking fault energy is found to be obvious. In addition, the calculated stacking fault energy is in agreement with experimental results for the two metals. © 2002 American Institute of Physics.
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61.72.Nn Stacking faults and other planar or extended defects

Effect of high-density plasma etching on the optical properties and surface stoichiometry of ZnO

K. Ip, K. H. Baik, M. E. Overberg, E. S. Lambers, Y. W. Heo, D. P. Norton, S. J. Pearton, F. Ren, and J. M. Zavada

Appl. Phys. Lett. 81, 3546 (2002); http://dx.doi.org/10.1063/1.1519095 (3 pages) | Cited 26 times

Online Publication Date: 28 October 2002

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Bulk, single-crystal ZnO was etched in Cl2/Ar and CH4/H2/Ar inductively coupled plasmas as a function of ion impact energy. For CH4/H2/Ar, the etch rate (R) increases with ion energy (E) as predicted from a model of ion enhanced sputtering by a collision–cascade process, R∝(E0.5−ETH0.5), where the threshold energy, ETH, is ∼ 96 eV. Band edge photoluminescence intensity decreases with incident ion energy in both chemistries, with a 70% decrease even for low energies ( ∼ 116 eV). Surface roughness is also a function of ion energy with a minimum at ∼ 250 eV, where Auger electron spectroscopy shows there is no measurable change in near-surface stoichiometry from that of unetched control samples. © 2002 American Institute of Physics.
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81.65.Cf Surface cleaning, etching, patterning
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
78.55.Cr III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

High epitaxial quality Y2O3 high-κ dielectric on vicinal Si(001) surfaces

G. Apostolopoulos, G. Vellianitis, A. Dimoulas, M. Alexe, R. Scholz, M. Fanciulli, D. T. Dekadjevi, and C. Wiemer

Appl. Phys. Lett. 81, 3549 (2002); http://dx.doi.org/10.1063/1.1519727 (3 pages) | Cited 18 times

Online Publication Date: 28 October 2002

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Thin films of Y2O3 were grown by molecular-beam epitaxy on silicon aiming at material with adequate crystal quality for use as high-κ gate replacements in future transistors. It was found that Y2O3 grows in single-crystalline form on 4° misoriented Si(001), due to an in-plane alignment of 〈110〉Y2O2 to the silicon dimer direction. The Y2O3 layers exhibit a low degree of mosaicity, a small proportion of twinning and sharp interfaces. This represents a significant improvement compared to material grown on exact silicon surfaces. © 2002 American Institute of Physics.
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68.55.-a Thin film structure and morphology
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Influence of the quantum-well shape on the light emission characteristics of InGaN/GaN quantum-well structures and light-emitting diodes

H. W. Shim, R. J. Choi, S. M. Jeong, Le Van Vinh, C.-H. Hong, E.-K. Suh, H. J. Lee, Y.-W. Kim, and Y. G. Hwang

Appl. Phys. Lett. 81, 3552 (2002); http://dx.doi.org/10.1063/1.1519725 (3 pages) | Cited 17 times

Online Publication Date: 28 October 2002

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Structural and optical properties of various shapes of quantum wells (QWs), including rectangular, triangular, trapezoidal, and polygonal ones are investigated. Photoluminescence (PL) measurements show that the highest light emission efficiency and the best reproducibility in the intensity and wavelength are obtained from trapezoidal QWs. The temperature dependence of PL spectra indicates the more localized nature of excitons in the trapezoidal QWs. A plan-view transmission electron microscopy shows that quantum dots (QDs) are formed inside the dislocation loop in trapezoidal QWs. The distribution of QDs in size and composition becomes more uniform with trapezoidal QWs than with rectangular QWs, leading to superior light-emission characteristics. It is suggested that QD engineering and dislocation control are possible, to some extent, by the modulation of the QW shape in InGaN/GaN-based light-emitting devices.© 2002 American Institute of Physics.
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78.67.De Quantum wells
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
85.60.Jb Light-emitting devices
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
78.60.Fi Electroluminescence

Surface dihydrides on Ge(100): A scanning tunneling microscopy study

Jae Yeol Maeng, Jun Young Lee, Young Eun Cho, Sehun Kim, and Sam K. Jo

Appl. Phys. Lett. 81, 3555 (2002); http://dx.doi.org/10.1063/1.1520329 (3 pages) | Cited 12 times

Online Publication Date: 28 October 2002

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We studied the atomic scale surface evolution of Ge(100) exposed at 300 K to gas-phase hydrogen atoms, H(g). Surface H(g) uptake created a 2×1:H phase, quickly reaching ∼1 monolayer H coverage. However, in contrast to the Si(100) surface, dangling bonds of the Ge(100) surface could never be completely removed by H(g) due to their regeneration by highly efficient surface H abstraction. This, together with the instability of surface dihydrides, GeH2(a), inhibited the large-scale formation of 3×1:H and 1×1:H phases. Short GeH2(a) rows, present in small metastable 3×1:H domains formed near defect sites, were etched selectively by H(g), producing line defects. © 2002 American Institute of Physics.
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68.43.Mn Adsorption kinetics
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)

Control of crystallographic tilt in GaN grown on Si (111) by cantilever epitaxy

T. M. Katona, J. S. Speck, and S. P. DenBaars

Appl. Phys. Lett. 81, 3558 (2002); http://dx.doi.org/10.1063/1.1519943 (3 pages) | Cited 12 times

Online Publication Date: 28 October 2002

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We have eliminated the crystallographic tilt associated with lateral growth during cantilever epitaxy by adjusting the lateral to vertical growth rate during the initial stages of growth. Cantilever epitaxy is a single growth run technique utilizing periodic, parallel mesas formed by etching the substrate. We have studied the relationship between the geometry of the “wing” region, the GaN spanning the etched trench, and the magnitude of crystallographic wing tilt. Cross-sectional scanning electron microscopy was used to characterize the geometry of the wing region, and x-ray diffraction was used to measure the magnitude of crystallographic tilt. It was found that by starting the GaN overgrowth with a slow lateral growth rate, compared to the vertical growth rate, a low tilt (⩽0.2°) was established and stabilized. The lateral growth rate can be increased during later stages of growth to assist in fast coalescence of neighboring stripes without significantly affecting the magnitude of crystallographic tilt. © 2002 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.05.Ea III-V semiconductors
61.72.Mm Grain and twin boundaries
81.65.Cf Surface cleaning, etching, patterning

Potential sputtering of proton from hydrogen-terminated Si(100) surfaces induced with slow highly charged ions

K. Kuroki, N. Okabayashi, H. Torii, K. Komaki, and Y. Yamazaki

Appl. Phys. Lett. 81, 3561 (2002); http://dx.doi.org/10.1063/1.1520335 (3 pages) | Cited 12 times

Online Publication Date: 28 October 2002

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A potential sputtering mechanism of hydrogen has been studied for impact of slow highly charged Xeq+ ions (<5 keV, q = 4–12) on well-defined H-terminated Si(100) surfaces. It was found that the sputtering yields of protons are proportional to qγ (γ ∼ 5), independent of the surface condition, that is, for both Si(100)2×1-H surface and Si(100)1×1-H surface. The yield for Si(100)1×1-H surface was ten times larger than that for Si(100)2×1-H surface, although the H coverage of the former is only twice the latter. Surface roughness is found to be the key parameter to vary the yield, and also to influence the energy distribution of sputtered protons. These findings are consistently explained with a pair-wise bond-breaking model induced by a double electron capture, where the classical over barrier process plays an essential role. © 2002 American Institute of Physics.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)

Atomic and electronic structures of doped grain boundaries in SrTiO3

Hyunju Chang, Youngmin Choi, Jae Do Lee, and Hongsuk Yi

Appl. Phys. Lett. 81, 3564 (2002); http://dx.doi.org/10.1063/1.1519960 (3 pages) | Cited 3 times

Online Publication Date: 28 October 2002

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The atomic and electronic structures of pristine, Mn- and Nb-doped grain boundaries in SrTiO3 are investigated by atomistic simulations and cluster calculations. The atomic structures of (310) symmetric tilt grain boundaries in SrTiO3 are determined by atomistic simulation using empirical potentials. The defect energies of Mn(Nb)-doped models are calculated and discussed in relation to the concentration profiles of Mn(Nb) in SrTiO3 grain boundaries. The local electronic structures near Mn(Nb)-doped grain boundaries in SrTiO3 are determined using embedded cluster calculations based on the density functional theory. The charge density of each system is calculated to elucidate the electronic structure of the grain boundary. The calculation results agree well with previous experimental observations of the atomic structures and grain boundary charges near the Mn(Nb)-doped grain boundary in SrTiO3. © 2002 American Institute of Physics.
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61.72.Mm Grain and twin boundaries
71.55.Ht Other nonmetals
61.72.Bb Theories and models of crystal defects
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Coiling-chirality changes in carbon microcoils obtained by catalyzed pyrolysis of acetylene and its mechanism

Shaoming Yang, Xiuqin Chen, and Seiji Motojima

Appl. Phys. Lett. 81, 3567 (2002); http://dx.doi.org/10.1063/1.1516612 (3 pages) | Cited 17 times

Online Publication Date: 28 October 2002

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As can be seen in the double helix of DNA, the single helix of proteins, etc., the three-dimensional (3D) helical/spiral structure is a fundamental structure of living things, and affords them critical functionalities. Helically coiled carbon fibers, which usually take the peculiar form of either a microcoil or a helix or twisted form, referred to as “carbon microcoils hereafter,” are of great interest due to their novel functionality and various potential applications. They can potentially be used in electromagnetic absorbers and/or filters, 3D composites, smart tunable electrical devices, microsensors, chiral catalysts, etc. © 2002 American Institute of Physics.
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81.05.U- Carbon/carbon-based materials
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Preferential carbon etching by hydrogen inside hexagonal voids of 6H-SiC(0001)

Dirk Sander, Wulf Wulfhekel, Margrit Hanbücken, Serge Nitsche, Jean Pierre Palmari, Frédéric Dulot, François Arnaud d’Avitaya, and André Leycuras

Appl. Phys. Lett. 81, 3570 (2002); http://dx.doi.org/10.1063/1.1519962 (3 pages) | Cited 7 times

Online Publication Date: 28 October 2002

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6H-SiC(0001) samples have been etched in a hot-wall chemical vapor deposition reactor at a hydrogen pressure of 13 mbar at 1800 °C. The surface morphology and elemental composition have been studied by scanning electron microscopy and micro-Auger analysis. Stoichiometric etching of SiC with equal atomic concentrations of Si and C is found on the flat sections of the surface, but in hexagonal voids of the SiC samples, a selective removal of C, leading to a pure Si surface at the bottom of the voids, is observed. Fast gas diffusion is the main transport mechanism for etching of the flat surface, while Knudsen diffusion becomes important inside the voids. It is proposed that the lower diffusion constant of reaction products containing Si compared to those containing C, leads to a preferential removal of C and a Si enrichment inside the voids. © 2002 American Institute of Physics.
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81.65.Cf Surface cleaning, etching, patterning
81.05.Hd Other semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.35.Dv Composition, segregation; defects and impurities
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.Qq Microscopic defects (voids, inclusions, etc.)
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
79.20.Fv Electron impact: Auger emission
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Atomic relocation processes in impurity-free disordered p-GaAs epilayers studied by deep level transient spectroscopy

P. N. K. Deenapanray, A. Martin, S. Doshi, H. H. Tan, and C. Jagadish

Appl. Phys. Lett. 81, 3573 (2002); http://dx.doi.org/10.1063/1.1519728 (3 pages) | Cited 3 times

Online Publication Date: 28 October 2002

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We have used capacitance–voltage and deep level transient spectroscopy techniques to study the relocation of impurities, such as Zn and Cu, in impurity-free disordered (IFD) p-type GaAs. A four-fold increase in the doping concentration is observed after annealing at 925 °C. Two electrically active defects HA (EV+0.39 eV) and HB2 (EV+0.54 eV), which we have attributed to Cu- and Asi/AsGa-related levels, respectively, are observed in the disordered p-GaAs layers. The injection of gallium vacancies causes segregation of Zn dopant atoms and Cu towards the surface of IFD samples. The atomic relocation process is critically assessed in terms of the application of IFD to the band gap engineering of doped GaAs-based heterostructures. © 2002 American Institute of Physics.
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71.55.Eq III-V semiconductors
73.61.Ey III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Cc Kinetics of defect formation and annealing
64.75.-g Phase equilibria
61.72.Yx Interaction between different crystal defects; gettering effect
61.72.S- Impurities in crystals
61.72.uj III-V and II-VI semiconductors

Electron transport through strongly coupled AlInP/GaInP superlattices

R. E. Martínez, I. Appelbaum, C. V. Reddy, R. Sheth, K. J. Russell, V. Narayanamurti, J.-H. Ryou, U. Chowdhury, and R. D. Dupuis

Appl. Phys. Lett. 81, 3576 (2002); http://dx.doi.org/10.1063/1.1519350 (3 pages)

Online Publication Date: 28 October 2002

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Using ballistic-electron-emission spectroscopy, electron transport through the principal (Γc,Lc) miniband of an (Al0.5In0.5P)11/(Ga0.5In0.5P)10 superlattice in the strong-coupling regime has been observed. Second derivative spectra of experimental data and Monte Carlo simulations were in agreement. © 2002 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.21.Cd Superlattices

Scanning Kelvin force microscopy imaging of surface potential variations near threading dislocations in GaN

J. W. P. Hsu, H. M. Ng, A. M. Sergent, and S. N. G. Chu

Appl. Phys. Lett. 81, 3579 (2002); http://dx.doi.org/10.1063/1.1519732 (3 pages) | Cited 22 times

Online Publication Date: 28 October 2002

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Scanning Kelvin force microscopy is applied to study the charge nature of threading dislocations on GaN surfaces. On the oxidized surface, the surface potential maps show little change near dislocations, indicating that if the dislocations are charged in the bulk, the charges are either screened or depleted due to band bending. After cleaning in hot H3PO4, the potential near dislocations located at domain boundaries and inside domains is found to be lower, consistent with excess local negative fixed charges. Curiously, no contrast was seen for the screw dislocations at the centers of growth spirals even after H3PO4 treatment. Thus, either these screw dislocations have no gap states, or if they do have gap states, the positions are higher in energy (closer to conduction band edge) than the gap states of other dislocations. © 2002 American Institute of Physics.
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68.35.Dv Composition, segregation; defects and impurities
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.37.Ps Atomic force microscopy (AFM)
73.25.+i Surface conductivity and carrier phenomena
71.55.Eq III-V semiconductors
81.65.Cf Surface cleaning, etching, patterning
81.05.Ea III-V semiconductors

Reduction of effective dielectric constant of gate insulator by low-resistivity electrodes

Kunio Saito, Yoshito Jin, and Masaru Shimada

Appl. Phys. Lett. 81, 3582 (2002); http://dx.doi.org/10.1063/1.1519736 (3 pages) | Cited 9 times

Online Publication Date: 28 October 2002

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On metal–oxide–semiconductor capacitors, the effective dielectric constant (keff) values extracted from high-frequency capacitance–voltage measurements were found to decrease when gate electrodes of very low resistivity were used. The equivalent-oxide thickness increase reaches about 1 nm with the low-resistivity electrodes. We examined gate insulators of SiO2, Al2O3, and HfO2 and gate electrodes of Al, TiN, Au, Cr, and TaN. The equivalent-oxide thickness increase can be prevented by inserting a high-resistivity metal film only 0.3 nm thick between the very low-resistivity metal and the insulator. The present results suggest that keff is reduced by the screening of ionic insulators with free electrons of the metal due to a quantum effect. © 2002 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.61.Ng Insulators
77.22.Ch Permittivity (dielectric function)
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
73.23.-b Electronic transport in mesoscopic systems

Contactless measurement of electrical conductivity of semiconductor wafers using the reflection of millimeter waves

Yang Ju, Kojiro Inoue, Masumi Saka, and Hiroyuki Abé

Appl. Phys. Lett. 81, 3585 (2002); http://dx.doi.org/10.1063/1.1520339 (3 pages) | Cited 11 times

Online Publication Date: 28 October 2002

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We present a method for quantitative measurement of electrical conductivity of semiconductor wafers in a contactless fashion by using millimeter waves. A focusing sensor was developed to focus a 110 GHz millimeter wave beam on the surface of a silicon wafer. The amplitude and the phase of the reflection coefficient of the millimeter wave signal were measured by which electrical conductivity of the wafer was determined quantitatively, independent of the permittivity and thickness of the wafers. The conductivity obtained by this method agrees well with that measured by the conventional four-point-probe method. © 2002 American Institute of Physics.
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84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
85.30.De Semiconductor-device characterization, design, and modeling
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
85.40.Qx Microcircuit quality, noise, performance, and failure analysis

Measurements of anisotropic thermoelectric properties in superlattices

B. Yang, W. L. Liu, J. L. Liu, K. L. Wang, and G. Chen

Appl. Phys. Lett. 81, 3588 (2002); http://dx.doi.org/10.1063/1.1515876 (3 pages) | Cited 43 times

Online Publication Date: 28 October 2002

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Thermoelectric properties, i.e., thermal conductivity, electrical conductivity, and the Seebeck coefficient, have been measured in the directions parallel (in-plane) and perpendicular to the interface of an n-type Si(80 Å)/Ge(20 Å) superlattice. A two-wire 3ω method is employed to measure the in-plane and cross-plane thermal conductivities. The cross-plane Seebeck coefficient is deduced by using a differential measurement between the superlattice and reference samples and the cross-plane electrical conductivity is determined through a modified transmission-line method. The in-plane thermal conductivity of the Si/Ge superlattice is 5–6 times higher than the cross-plane one, and the electrical conductivity shows a similar anisotropy. The anisotropy of the Seebeck coefficients is smaller in comparison to electrical and thermal conductivities in the temperature range from 150 to 300 K. However, the cross-plane Seebeck coefficient rises faster with increasing temperature than that of the in-plane direction. © 2002 American Institute of Physics.
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73.63.-b Electronic transport in nanoscale materials and structures
72.20.Pa Thermoelectric and thermomagnetic effects
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
73.50.Lw Thermoelectric effects

Location of holes in silicon-rich oxide as memory states

I. Crupi, S. Lombardo, E. Rimini, C. Gerardi, B. Fazio, and M. Melanotte

Appl. Phys. Lett. 81, 3591 (2002); http://dx.doi.org/10.1063/1.1520340 (3 pages) | Cited 2 times

Online Publication Date: 28 October 2002

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The induced changes of the flatband voltage by the location of holes in a silicon-rich oxide (SRO) film sandwiched between two thin SiO2 layers [used as gate dielectric in a metal–oxide–semiconductor (MOS) capacitor] can be used as the two states of a memory cell. The principle of operation is based on holes permanently trapped in the SRO layer and reversibly moved up and down, close to the metal and the semiconductor, in order to obtain the two logic states of the memory. The concept has been verified by suitable experiments on MOS structures. The device exhibits an excellent endurance behavior and, due to the low mobility of the holes at low field in the SRO layer, a much longer refresh time compared to conventional dynamic random access memory cells. © 2002 American Institute of Physics.
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84.30.Sk Pulse and digital circuits
84.32.Tt Capacitors
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
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