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16 Oct 2000

Volume 77, Issue 16, pp. 2437-2616

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Structural analysis of InxGa1−xN single quantum wells by coaxial-impact collision ion scattering spectroscopy

M. Sumiya, S. Nakamura, S. F. Chichibu, K. Mizuno, M. Furusawa, and M. Yoshimoto

Appl. Phys. Lett. 77, 2512 (2000); http://dx.doi.org/10.1063/1.1318933 (3 pages) | Cited 2 times

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The structures of InxGa1−xN single quantum wells (SQWs) on 3-μm-thick GaN layer for the ultraviolet, blue, and green light-emitting devices were investigated by coaxial-impact collision ion scattering spectroscopy (CAICISS). The possibility that CAICISS could analyze structural fluctuation of the ternary system like InxGa1−xN was demonstrated. It was found that In incorporated into InGaN SQWs occupied the substitutional site of Ga atom having Ga-face (+c) polarity. © 2000 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
78.66.Fd III-V semiconductors

Refractive index dispersion functions of solid-phase polymers by multicolor optical diffraction

J. V. Ford, B. G. Sumpter, D. W. Noid, M. D. Barnes, and J. U. Otaigbe

Appl. Phys. Lett. 77, 2515 (2000); http://dx.doi.org/10.1063/1.1318940 (3 pages) | Cited 4 times

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We show that fourth-order dispersion functions of solid-phase polymers can be determined by multicolor optical diffraction. Electrodynamically trapped microparticles of polyethylene glycol with different molecular weights were probed by two-dimensional optical diffraction with four different laser wavelengths (632.8, 514.5, 488.0, and 457.9 nm); subsequent Mie analysis of one-dimensional scattering patterns yielded size and refractive index (both real and imaginary parts). Using a single wavelength as a size reference, the nonlinear dependence of the refractive index of solid (nonevaporating) polymer microparticles was determined by finding the refractive index for a given wavelength that best matched a Mie calculation subject to the reference size constraint. The experimentally determined refractive index values were fit to a standard fourth-order Cauchy function to obtain values for n0, n1, and n2. © 2000 American Institute of Physics.
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42.70.Jk Polymers and organics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.25.Fx Diffraction and scattering
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Enhancement of cathodoluminescent and photoluminescent properties of Eu:Y2O3 luminescent films by vacuum cooling

D. Kumar, J. Sankar, K. G. Cho, V. Craciun, and R. K. Singh

Appl. Phys. Lett. 77, 2518 (2000); http://dx.doi.org/10.1063/1.1318938 (3 pages) | Cited 23 times

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This letter investigates the role of postdeposition oxygen treatments upon their luminescent properties by synthesizing Eu:Y2O3 films by pulsed laser deposition under different conditions and subjecting them to various postdeposition oxygen treatments. Our results have shown that Eu:Y2O3 films grown in 300 mTorr oxygen ambient and cooled in vacuum (10−6 Torr) after the termination of growth exhibit better photoluminescent and cathodoluminescent brightness than those grown in (i) vacuum and cooled in vacuum and (ii) 300 mTorr oxygen and cooled in 2 Torr oxygen. Two possible mechanisms have been proposed to explain these results. © 2000 American Institute of Physics.
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78.66.Nk Insulators
78.55.Hx Other solid inorganic materials
78.60.Hk Cathodoluminescence, ionoluminescence
81.40.Tv Optical and dielectric properties related to treatment conditions
81.15.Fg Pulsed laser ablation deposition
85.45.Fd Field emission displays (FEDs)

Characterization of excimer-laser-annealed polycrystalline silicon films grown by ultrahigh-vacuum chemical vapor deposition

Ying-Chia Chen, YewChung Sermon Wu, I-Chung Tung, Chi-Wei Chao, Ming-Shiann Feng, and Huang-Chung Chen

Appl. Phys. Lett. 77, 2521 (2000); http://dx.doi.org/10.1063/1.1318937 (3 pages) | Cited 5 times

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Polycrystalline silicon (poly-Si) films grown by ultrahigh-vacuum chemical vapor deposition (UHVCVD) system and then annealed by excimer laser at room temperature have been investigated for the applications in polycrystalline silicon thin-film transistors (poly-Si TFTs). The results showed that the grain size of the laser-annealed poly-Si film decreased with laser energy density when a lower laser energy density below 157.7 mJ/cm2 was used. At about the threshold laser energy density ( ∼ 134.5 mJ/cm2), the finest grain structure could be obtained due to the partial melting in the top layer of the film. When the energy density of the excimer laser was larger than the threshold energy density, the large grain growth was initiated. The largest grain structure could be obtained at ∼ 184 mJ/cm2, while its surface roughness was better than that of the nonannealed UHVCVD poly-Si films. The surface roughening was suggested to arise from the specific melt-regrowth process but not the rapid release of hydrogen or capillary wave mechanism derived from laser-annealed amorphous silicon. By use of the laser-annealed UHVCVD poly-Si films as the active layer, the fabricated poly-Si TFT exhibited a field-effect mobility of 138 cm2/V s, a subthreshold swing of 0.8 V/dec, a threshold voltage of 3.5 V, and an on/off current ratio of ∼ 106. © 2000 American Institute of Physics.
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68.60.Dv Thermal stability; thermal effects
68.55.-a Thin film structure and morphology
61.72.Cc Kinetics of defect formation and annealing
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.82.Fk Semiconductors
78.66.Db Elemental semiconductors and insulators
78.40.Fy Semiconductors
85.30.Tv Field effect devices

Complete removal of threading dislocations from mismatched layers by patterned heteroepitaxial processing

X. G. Zhang, A. Rodriguez, X. Wang, P. Li, F. C. Jain, and J. E. Ayers

Appl. Phys. Lett. 77, 2524 (2000); http://dx.doi.org/10.1063/1.1319178 (3 pages) | Cited 9 times

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We report the effectiveness of patterned heteroepitaxial processing (PHP) in removing threading dislocations (TDs) from ZnSe epitaxial layers grown on GaAs substrates by metalorganic vapor phase epitaxy. The PHP approach used here involves postgrowth patterning of continuous epitaxial layers followed by annealing. In this study, each as-grown ZnSe/GaAs sample was first cut into pieces forming four types of samples, namely: (1) as grown, (2) postgrowth annealed, (3) postgrowth patterned, and (4) PHP prepared (patterned and annealed). The epitaxial layers with thicknesses of 2000–6000 Å were patterned to create 500–6000-Å-high and 3–70-μm-wide square mesas that were separated by 20 μm trenches. TD densities were determined by the etch pit density (EPD) technique and comparisons were made between the four types of samples. The first three types of samples exhibited EPDs of approximately 107 cm−2, which indicate that neither patterning alone nor annealing alone was effective at reducing TDs. In contrast, PHP resulted in a complete removal of TDs from 70 μm×70 μm square layers with thicknesses of >3000 Å. This corresponds to an EPD less than 2.0×104 cm−2, and at least a 500-fold reduction compared to as-grown layers; in fact, this value is even lower than that of the GaAs substrate (EPD=105 cm−2). Thus TDs can be removed in PHP by glide to the sidewalls, as promoted by the presence of image forces. © 2000 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.05.Dz II-VI semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
61.72.Cc Kinetics of defect formation and annealing
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.Lk Linear defects: dislocations, disclinations

Phase diagram of epitaxial ferromagnets: Erbium (0001) on sapphire (11math0)

C. S. Durfee and C. P. Flynn

Appl. Phys. Lett. 77, 2527 (2000); http://dx.doi.org/10.1063/1.1319182 (3 pages)

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We have accurately determined the elastic state and the magnetic phase diagram of epitaxially clamped Er on Al2O3 through the range of strong bulk magnetostriction. The elastic free energy is too small to explain the observed change of the Curie point. The additional required energy of ∼5% of the self-energy for full perpendicular magnetization must arise from differences of domain configuration between the magnetized bulk and the film. © 2000 American Institute of Physics.
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75.50.Cc Other ferromagnetic metals and alloys
75.70.Ak Magnetic properties of monolayers and thin films
75.80.+q Magnetomechanical effects, magnetostriction
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.60.Ch Domain walls and domain structure
75.70.Kw Domain structure (including magnetic bubbles and vortices)
68.55.-a Thin film structure and morphology

Y-junction carbon nanotubes

B. C. Satishkumar, P. John Thomas, A. Govindaraj, and C. N. R. Rao

Appl. Phys. Lett. 77, 2530 (2000); http://dx.doi.org/10.1063/1.1319185 (3 pages) | Cited 155 times

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Carbon nanotubes with junctions are considered to be of potential value in nanoelectronics. A simple pyrolysis procedure for producing Y-junction carbon nanotubes is described. The method involves the pyrolysis of the organometallic precursor, nickelocene, along with thiophene at 1273 K. Tunneling conductance measurements showed that at the Y junction, the I-V characteristics are asymmetric with respect to zero bias as in a junction diode. © 2000 American Institute of Physics.
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81.05.ub Fullerenes and related materials
85.65.+h Molecular electronic devices
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
73.61.Wp Fullerenes and related materials
73.40.Gk Tunneling

Dislocation energetics in epitaxial strained islands

B. J. Spencer and J. Tersoff

Appl. Phys. Lett. 77, 2533 (2000); http://dx.doi.org/10.1063/1.1319186 (3 pages) | Cited 20 times

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We calculate (to first order in the Burgers vector) the energy of introducing dislocations into Stranski-Krastanow islands having equilibrium shape. These results suggest that misfit dislocations of different Burgers vector tend to segregate spatially within the islands, which may be a source of mosaic structure in films formed by island coalescence. © 2000 American Institute of Physics.
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61.72.Lk Linear defects: dislocations, disclinations
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
64.75.-g Phase equilibria
61.72.Bb Theories and models of crystal defects
66.30.Lw Diffusion of other defects

Pressure dependence of the blue luminescence in Mg-doped GaN

S. Ves, U. D. Venkateswaran, I. Loa, K. Syassen, F. Shahedipour, and B. W. Wessels

Appl. Phys. Lett. 77, 2536 (2000); http://dx.doi.org/10.1063/1.1319180 (3 pages) | Cited 1 time

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We report the hydrostatic pressure dependence of the blue luminescence band observed at ∼2.8 eV in heavily magnesium-doped GaN (GaN:Mg) epilayers grown on sapphire by metalorganic chemical vapor deposition. Photoluminescence (PL) studies carried out up to 6 and 8 GPa, respectively, at room and low (10 K) temperature show that the pressure-induced energy shift of this PL band is ∼26 meV/GPa. This blueshift is about 40% less than the shift observed for the band edge in GaN. A substantially smaller pressure coefficient suggests that the 2.8 eV PL transition is associated with the recombination via deep centers. © 2000 American Institute of Physics.
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78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
62.50.-p High-pressure effects in solids and liquids
71.55.Gs II-VI semiconductors

Photoirradiation effect on polymer light-emitting device: Separation between recombination zone and photo-oxidized defects

Kazuya Tada and Mitsuyoshi Onoda

Appl. Phys. Lett. 77, 2539 (2000); http://dx.doi.org/10.1063/1.1314888 (3 pages) | Cited 6 times

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The photoirradiation effect on the characteristics of a polymer light-emitting diode with a semitransparent metal cathode is studied. The electroluminescence intensity as well as the photoluminescence quantum efficiency decreases due to photoirradiation in air, while the external quantum efficiency of electroluminescence does not change. This suggests that not the formation of quenching defects but the degraded carrier transport/injection nature of the polymer mainly affects the emission property of the device and that the recombination zone is separated from the photo-oxidized defects. Two models of the separation, the layer model and the scattering model, are proposed. The validity of the two models depends on the penetration depth of oxygen in the polymer. © 2000 American Institute of Physics.
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85.60.Jb Light-emitting devices
42.70.Jk Polymers and organics
78.66.Qn Polymers; organic compounds
61.82.Pv Polymers, organic compounds
61.41.+e Polymers, elastomers, and plastics
78.60.Fi Electroluminescence
78.55.Kz Solid organic materials
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Optical properties of high-quality CuInSe2 single crystals

A. V. Mudriy, I. V. Bodnar, I. A. Viktorov, V. F. Gremenok, M. V. Yakushev, R. D. Tomlinson, A. E. Hill, and R. D. Pilkington

Appl. Phys. Lett. 77, 2542 (2000); http://dx.doi.org/10.1063/1.1308525 (3 pages) | Cited 12 times

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CuInSe2 single crystals have been studied employing photoluminescence (PL), optical reflection (OR), optical absorption (OA) and wavelength derivative reflection (WDR) techniques at temperatures from 4.2 to 300 K. Exciton-related peaks were observed in the near-band-edge region of the PL spectra: several narrow lines, with full width at half maximum (FWHM) of about 0.3 meV, and two wider peaks (FWHM about 0.7 meV) at 1.0414 (A) and 1.0449 eV (B). The A and B peaks were also observed in the OR and OA spectra and identified as A and B free excitonic states. The narrow lines were attributed to bound exciton recombination on intrinsic defects. A third exciton resonance (C) was observed in the WDR spectra at 1.2779 eV. The crystal-field and spin-orbit splittings were derived to be 5.3 and 234.7 meV, respectively. © 2000 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
78.40.Fy Semiconductors
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
71.70.Ch Crystal and ligand fields

Optical properties of multiple layers of self-organized InAs quantum dots emitting at 1.3 μm

J. Bloch, J. Shah, L. N. Pfeiffer, K. W. West, and S. N. G. Chu

Appl. Phys. Lett. 77, 2545 (2000); http://dx.doi.org/10.1063/1.1289493 (3 pages) | Cited 26 times

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We report the growth and characterization of multiple layers of self-organized InAs quantum dots emitting near 1.3 μm. We analyze their optical properties as a function of the number of dot layers and investigate how the vertical stack modifies the dot size distribution. © 2000 American Institute of Physics.
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78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
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Improvement on epitaxial grown of InN by migration enhanced epitaxy

Hai Lu, William J. Schaff, Jeonghyun Hwang, Hong Wu, Wesley Yeo, Amit Pharkya, and Lester F. Eastman

Appl. Phys. Lett. 77, 2548 (2000); http://dx.doi.org/10.1063/1.1318235 (3 pages) | Cited 106 times

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Epitaxial growth of InN on (0001) sapphire with an AlN buffer layer was studied by migration-enhanced epitaxy, which is composed of an alternative supply of pure In atoms and N2 plasma. A series of samples were prepared with different substrate temperatures ranging from 360 to 590 °C. As-grown films were characterized by x-ray diffraction (XRD), reflective high-energy electron diffraction, atomic-force microscopy (AFM), and Hall measurements. Both XRD θ–2θ and ω scans show that the full width at half maximum of the (0002) peak nearly continuously decrease with increasing growth temperature, while InN grown at 590 °C shows the poorest surface morphology from AFM. It is suggested that three-dimensional characterization is necessary for an accurate evaluation of the quality of the InN epilayer. Hall mobility as high as 542 cm2/V s was achieved on film grown at ∼ 500 °C with an electron concentration of 3×1018 cm−3 at room temperature. These results argue against the common view that nitrogen vacancies are responsible for the high background n-type conductivity of InN. To illuminate the relationship between Hall mobility and carrier concentration, the electrical properties of all InN films grown recently were summarized. © 2000 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
73.61.Ey III-V semiconductors
68.55.-a Thin film structure and morphology
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

High electron mobility in AlGaN/GaN heterostructures grown on bulk GaN substrates

E. Frayssinet, W. Knap, P. Lorenzini, N. Grandjean, J. Massies, C. Skierbiszewski, T. Suski, I. Grzegory, S. Porowski, G. Simin, X. Hu, M. Asif Khan, M. S. Shur, R. Gaska, and D. Maude

Appl. Phys. Lett. 77, 2551 (2000); http://dx.doi.org/10.1063/1.1318236 (3 pages) | Cited 47 times

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Dislocation-free high-quality AlGaN/GaN heterostructures have been grown by molecular-beam epitaxy on semi-insulating bulk GaN substrates. Hall measurements performed in the 300 K–50 mK range show a low-temperature electron mobility exceeding 60 000 cm2/V s for an electron sheet density of 2.4×1012 cm−2. Magnetotransport experiments performed up to 15 T exhibit well-defined quantum Hall-effect features. The structures corresponding to the cyclotron and spin splitting were clearly resolved. From an analysis of the Shubnikov de Hass oscillations and the low-temperature mobility we found the quantum and transport scattering times to be 0.4 and 8.2 ps, respectively. The high ratio of the scattering to quantum relaxation time indicates that the main scattering mechanisms, at low temperatures, are due to long-range potentials, such as Coulomb potentials of ionized impurities. © 2000 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.05.Ea III-V semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
72.20.Fr Low-field transport and mobility; piezoresistance
73.61.Ey III-V semiconductors
72.20.My Galvanomagnetic and other magnetotransport effects
73.43.-f Quantum Hall effects

Finite size effects in carbon nanotubes

Jian Wu, Wenhui Duan, Bing-Lin Gu, Jing-Zhi Yu, and Yoshiyuki Kawazoe

Appl. Phys. Lett. 77, 2554 (2000); http://dx.doi.org/10.1063/1.1318241 (3 pages) | Cited 17 times

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The low-energy theory for finite long carbon nanotube is derived and numerically examined. It shows that the electronic structure is dominated by the quantum confining, which determines the profile of wave functions as well as the eigen energies; while the details of the wave functions are resolved by the structure of the nanotubes. This behavior is attributed to the peculiar electronic structure of the nanotubes. Because of the slow variation of the profile of electron wave functions, the measured conductance is NOT independent of the position to measure it, which is evident in the multiprobe experiment. © 2000 American Institute of Physics.
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71.20.Tx Fullerenes and related materials; intercalation compounds
72.80.Rj Fullerenes and related materials

Conductive layer near the GaN/sapphire interface and its effect on electron transport in unintentionally doped n-type GaN epilayers

M. G. Cheong, K. S. Kim, C. S. Oh, N. W. Namgung, G. M. Yang, C.-H. Hong, K. Y. Lim, E.-K. Suh, K. S. Nahm, H. J. Lee, D. H. Lim, and A. Yoshikawa

Appl. Phys. Lett. 77, 2557 (2000); http://dx.doi.org/10.1063/1.1318728 (3 pages) | Cited 18 times

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Temperature-dependent Hall effect measurements on unintentionally doped n-type GaN epilayers show that, above room temperature, the Hall-mobility values of different samples vary parallel with each other with temperature. We demonstrate that this anomaly is mainly due to a conductive layer near the GaN/sapphire interface for thin samples with low carrier density. Through trapping electrons, threading edge dislocations (TEDs) debilitate the epilayer contribution in a two-layer mixed conduction model involving the epilayer and the near-interface layer. The trapping may, in part, explain low mobility and anomalous transport in pure GaN layers. Scattering by TEDs is important only at low temperatures. © 2000 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.50.Bk General theory, scattering mechanisms

Fowler–Nordheim hole tunneling in p-SiC/SiO2 structures

R. K. Chanana, K. McDonald, M. Di Ventra, S. T. Pantelides, L. C. Feldman, G. Y. Chung, C. C. Tin, J. R. Williams, and R. A. Weller

Appl. Phys. Lett. 77, 2560 (2000); http://dx.doi.org/10.1063/1.1318229 (3 pages) | Cited 22 times

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We report the confirmed occurrence of Fowler–Nordheim hole tunneling in p-4H–SiC metal-oxide-semiconductor capacitor structures. The effective mass for holes in the oxide is found to be in the range of 0.35m–0.52m, where m is the free electron mass. © 2000 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.40.Gk Tunneling
73.20.-r Electron states at surfaces and interfaces
85.30.Tv Field effect devices
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Variable frequency photoconductive grating method

J. P. Nicholson

Appl. Phys. Lett. 77, 2563 (2000); http://dx.doi.org/10.1063/1.1318936 (3 pages) | Cited 1 time

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The theoretical treatment of the steady-state photocarrier grating method is extended to include the frequency dependence of the chopping frequency, ω. It is shown that measurements of the characteristic parameter, β, as a function of ω yield both the ambipolar diffusion length, L, as well as the carrier lifetime, τ, for a fixed angular setting. An alternative experimental setup using a Pockel cell and polarizing cube as beam splitter is suggested to facilitate measurements at higher frequencies. © 2000 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.)
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.40.+w Photoconduction and photovoltaic effects
42.79.Dj Gratings
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
85.60.Bt Optoelectronic device characterization, design, and modeling

Role of inversion layer formation in producing low effective surface recombination velocities at Si/liquid contacts

William J. Royea, David J. Michalak, and Nathan S. Lewis

Appl. Phys. Lett. 77, 2566 (2000); http://dx.doi.org/10.1063/1.1318935 (3 pages) | Cited 3 times

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Photoconductivity decay lifetimes have been obtained for NH4F(aq)-etched Si(111) and for air-oxidized Si(111) surfaces in contact with solutions of CH3OH or tetrahydrofuran (THF) containing either ferrocene+/0 (Fc+/0), bis(pentamethylcyclopentadienyl) Fe+/0, or I2. Si surfaces in contact with electrolytes having Nernstian redox potentials >0 V versus the standard calomel electrode exhibited low effective surface recombination velocities regardless of the different surface chemistries, whereas those exposed only to N2(g) ambients or to electrolytes containing mild oxidants showed differing rf photoconductivity decay behavior depending on their different surface chemistry. The data reveal that formation of an inversion layer, and not a reduced density of electrical trap sites on the surface, is primarily responsible for the long charge-carrier lifetimes observed for Si surfaces in contact with CH3OH or THF electrolytes containing I2 or Fc+/0. © 2000 American Institute of Physics.
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73.40.Mr Semiconductor-electrolyte contacts
73.25.+i Surface conductivity and carrier phenomena
72.40.+w Photoconduction and photovoltaic effects
82.45.-h Electrochemistry and electrophoresis
73.20.-r Electron states at surfaces and interfaces
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
81.65.Cf Surface cleaning, etching, patterning
81.65.Rv Passivation

Ultrashallow junctions in silicon formed by molecular-beam epitaxy using boron delta doping

Phillip E. Thompson and Joe Bennett

Appl. Phys. Lett. 77, 2569 (2000); http://dx.doi.org/10.1063/1.1319189 (3 pages) | Cited 12 times

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Low-temperature molecular-beam epitaxy was used to form highly conductive, ultrashallow layers in silicon using boron delta doping. Junction depths, determined with secondary ion mass spectrometry, ranged from 7 to 18 nm. A minimum resistivity of 3×10−4 Ω cm was obtained when the delta-doped layers were spaced 2.5 nm apart. The sheet resistances of the epitaxial layers, plotted as a function of junction depth, followed the theoretical curve for a box-doped layer having a boron doping concentration equal to the solid solubility limit, 6×1020/cm3. At a specific thickness, the minimum sheet resistance obtained by B delta doping was more than a factor of 5 less than that achieved by ion implantation. © 2000 American Institute of Physics.
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61.72.uf Ge and Si
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.05.Cy Elemental semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
73.61.Cw Elemental semiconductors

Metal-assisted chemical etching in HF/H2O2 produces porous silicon

X. Li and P. W. Bohn

Appl. Phys. Lett. 77, 2572 (2000); http://dx.doi.org/10.1063/1.1319191 (3 pages) | Cited 176 times

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A simple and effective method is presented for producing light-emitting porous silicon (PSi). A thin (d<10 nm) layer of Au, Pt, or Au/Pd is deposited on the (100) Si surface prior to immersion in a solution of HF and H2O2. Depending on the type of metal deposited and Si doping type and doping level, PSi with different morphologies and light-emitting properties is produced. PSi production occurs on the time scale of seconds, without electrical current, in the dark, on both p- and n-type Si. Thin metal coatings facilitate the etching in HF and H2O2, and of the metals investigated, Pt yields the fastest etch rates and produces PSi with the most intense luminescence. A reaction scheme involving local coupling of redox reactions with the metal is proposed to explain the metal-assisted etching process. The observation that some metal remains on the PSi surface after etching raises the possibility of fabricating in situ PSi contacts. © 2000 American Institute of Physics.
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81.05.Rm Porous materials; granular materials
78.55.Mb Porous materials
81.65.Cf Surface cleaning, etching, patterning
81.05.Cy Elemental semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.55.Ap Elemental semiconductors

Thin film semiconductor deposition on free-standing ZnO columns

R. Könenkamp, K. Boedecker, M. C. Lux-Steiner, M. Poschenrieder, F. Zenia, C. Levy-Clement, and S. Wagner

Appl. Phys. Lett. 77, 2575 (2000); http://dx.doi.org/10.1063/1.1319187 (3 pages) | Cited 66 times

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We report the deposition of a-Si:H on thin films of free-standing single crystalline ZnO columns. The ZnO columns have a height of several μm and a diameter between 100 and 200 nm. The ZnO films are prepared in electrodeposition and have considerable potential for use in photoelectric thin film devices. Morphology, electronic parameters, and basic optical behavior, such as reflectance and light trapping efficiency, are reported. Amorphous silicon is deposited on the columns as a continuous smooth film with conformal coverage. Some possibilities of using these films in devices are discussed. © 2000 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.61.Ga II-VI semiconductors
73.61.Jc Amorphous semiconductors; glasses
78.30.Fs III-V and II-VI semiconductors
78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.66.Hf II-VI semiconductors
68.55.-a Thin film structure and morphology
81.15.Pq Electrodeposition, electroplating
78.66.Jg Amorphous semiconductors; glasses
84.60.Jt Photoelectric conversion

Aharonov–Bohm phase effects and inelastic scattering in transport through a parallel tunnel-coupled symmetric double-dot device

Anatoly Yu. Smirnov, Norman J. M. Horing, and Lev G. Mourokh

Appl. Phys. Lett. 77, 2578 (2000); http://dx.doi.org/10.1063/1.1317542 (3 pages) | Cited 8 times

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We have examined the effects of inelastic phonon scattering on the lead-to-lead current through a parallel-quantum-double-dot device to determine the persistence of coherence within the device. The tunnel-coupled double-dot system is taken to be symmetric and is threaded by Aharonov–Bohm magnetic flux. We show that at resonant values of the magnetic flux, when only the bonding or antibonding state is involved in transport through the double dot, the current–voltage characteristic changes drastically and the electron–phonon interaction has a pronounced effect on the level populations. However, it does not destroy coherence during the tunneling process through the system. © 2000 American Institute of Physics.
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85.35.Ds Quantum interference devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
63.20.K- Phonon interactions
71.38.-k Polarons and electron-phonon interactions
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Longitudinal magnetic recording media with thermal stabilization layers

E. N. Abarra, A. Inomata, H. Sato, I. Okamoto, and Y. Mizoshita

Appl. Phys. Lett. 77, 2581 (2000); http://dx.doi.org/10.1063/1.1319183 (3 pages) | Cited 110 times

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We introduce promising longitudinal recording media with enhanced thermal stability compared to conventional media. The media consist of one or more magnetic layers disposed between the recording layer and the underlayer with the magnetization direction of the layers being antiparallel to the adjacent layer or layers. Antiferromagnetic coupling is induced through a thin Ru layer between the Co-based magnetic layers. Comparison with conventional media with the same remanence magnetization and thickness product reveals improved thermal stability and read-write properties for the proposed media. © 2000 American Institute of Physics.
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75.50.Ss Magnetic recording materials
68.60.Dv Thermal stability; thermal effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.15.Cd Deposition by sputtering
75.30.Et Exchange and superexchange interactions

Preparation of crack-free antiferroelectric PbZrO3 thin films by a two-step annealing process

L. B. Kong and J. Ma

Appl. Phys. Lett. 77, 2584 (2000); http://dx.doi.org/10.1063/1.1319184 (3 pages) | Cited 7 times

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Crack-free antiferroelectric PbZrO3(PZ) thin films were prepared by a two-step annealing technique via a modified sol-gel process. Although x-ray diffraction results showed that single phase of perovskite PbZrO3 was obtained in the thin films annealed at 550, 700, and 550 °C/700 °C, double P-E hysteresis loop indicating phase transformation from antiferroelectric to ferroelectric phase was only observed for the two-step annealed PZ thin film at room temperature, with a forward switching field (EAFE-FE) of 151 kV/cm, a backward switching field (EFE-AFE) of about 77 kV/cm, and saturated polarization of 54 μC/cm2. The dielectric constant and dielectric loss of the PZ film annealed at 700 °C are 260 and 0.04 at 1 kHz, respectively. The prevention of the PZ film from being cracking by the two-step annealing procedure is believed to be a result of the more stable property of the film caused by the 550 °C pre-annealing. © 2000 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.80.Dj Domain structure; hysteresis
68.60.Dv Thermal stability; thermal effects
77.80.Fm Switching phenomena
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
77.80.B- Phase transitions and Curie point
68.55.-a Thin film structure and morphology
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
77.22.Ej Polarization and depolarization
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