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6 May 2002

Volume 80, Issue 18, pp. 3247-3450

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G-quartet biomolecular nanowires

A. Calzolari, R. Di Felice, E. Molinari, and A. Garbesi

Appl. Phys. Lett. 80, 3331 (2002); http://dx.doi.org/10.1063/1.1476700 (3 pages) | Cited 31 times

Online Publication Date: 29 April 2002

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We present a first-principle investigation of quadruple helix nanowires, consisting of stacked planar hydrogen-bonded guanine tetramers. Our results show that long wires form and are stable in potassium-rich conditions. We present their electronic band structure and discuss the interpretation in terms of effective wide-band-gap semiconductors. The microscopic structural and electronic properties of the guanine quadruple helices make them suitable candidates for molecular nanoelectronics. © 2002 American Institute of Physics.
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85.65.+h Molecular electronic devices

Si–SiO2 barrier height and its temperature dependence in metal-oxide-semiconductor structures with ultrathin gate oxide

A. Hadjadj, O. Simonetti, T. Maurel, G. Salace, and C. Petit

Appl. Phys. Lett. 80, 3334 (2002); http://dx.doi.org/10.1063/1.1476709 (3 pages) | Cited 4 times

Online Publication Date: 29 April 2002

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The potential distribution across n+ polycristalline silicon (poly-Si)/SiO2/Si(p) structures, with an oxide layer thinner than 4 nm, was determined using a full quantum self-consistent model. When applied to capacitance–voltage measurements, it allows an accurate determination of the oxide thickness tox to be made. When applied to current–voltage measurements, in the Fowler–Nordheim regime, it leads to an accurate determination of the barrier height Φ at the interface between the emitting poly-Si gate electrode and the oxide, over a temperature range 20–250 °C. The results show a constant Φ(0 K) for 3 nm<tox ⩽ 9 nm. However, the temperature sensitivity ∣dΦ/dT∣ increases from 0.35 to 0.7 meV/K with tox reduction. © 2002 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.40.Gk Tunneling
73.50.Fq High-field and nonlinear effects
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Estimation of the impact of electrostatic discharge on density of states in hydrogenated amorphous silicon thin-film transistors

Natasa Tosic Golo, Siebrigje van der Wal, Fred G. Kuper, and Ton Mouthaan

Appl. Phys. Lett. 80, 3337 (2002); http://dx.doi.org/10.1063/1.1476394 (3 pages) | Cited 2 times

Online Publication Date: 29 April 2002

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The objective of this letter is to give an estimation of the impact of an electrostatic discharge (ESD) stress on the density of states (DOS) within the energy gap of hydrogenated amorphous silicon (a-Si:H) thin-film transistors. ESD stresses were applied by means of a transmission line model tester. The DOS in the a-Si:H was determined by Suzuki’s algorithm using field-effect conductance measurements. A comparison of stressed and unstressed devices shows that there is a threshold ESD stress voltage, below which there is no damage. Above the threshold stress level, first an increase of the deep gap states is found and when stress is increased further, also in the tail states. © 2002 American Institute of Physics.
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85.30.Tv Field effect devices
71.23.Cq Amorphous semiconductors, metallic glasses, glasses
41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
85.30.De Semiconductor-device characterization, design, and modeling
71.55.Jv Disordered structures; amorphous and glassy solids

Combining a scanning near-field optical microscope with a picosecond streak camera: Statistical analysis of exciton kinetics in GaAs single-quantum wells

U. Neuberth, L. Walter, G. von Freymann, B. Dal Don, H. Kalt, M. Wegener, G. Khitrova, and H. M. Gibbs

Appl. Phys. Lett. 80, 3340 (2002); http://dx.doi.org/10.1063/1.1477274 (3 pages) | Cited 10 times

Online Publication Date: 29 April 2002

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Combining a low-temperature scanning near-field optical microscope with a picosecond streak camera allows us to measure the complete wavelength-time behavior at one spot on the sample within about 13 min at excitation powers of 100 nW. We use this instrument to measure the variation of relaxation times in disordered single-GaAs quantum wells with sample position. © 2002 American Institute of Physics.
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73.21.Fg Quantum wells
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.35.Lk Collective effects (Bose effects, phase space filling, and excitonic phase transitions)
68.37.Uv Near-field scanning microscopy and spectroscopy
78.47.-p Spectroscopy of solid state dynamics
07.68.+m Photography, photographic instruments; xerography

Interaction between low-energy electrons and defects created by hot holes in ultrathin silicon dioxide

Eric M. Vogel, Dawei Heh, and Joseph B. Bernstein

Appl. Phys. Lett. 80, 3343 (2002); http://dx.doi.org/10.1063/1.1471376 (3 pages) | Cited 4 times

Online Publication Date: 29 April 2002

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The interaction of injected electrons with defects created by hot holes in 2.0-nm-thick silicon dioxide is studied using substrate hot hole injection and concomitant electron tunneling. The ratio of injected hot holes to electrons is varied from approximately 10−3 to 100 by changing the forward biased substrate hot hole injector voltage. Increased bulk and interfacial degradation caused by the interaction of concomitantly injected electrons with defects created by hole injection is not observed for the experimental conditions studied. The ability of defects to produce catastrophic breakdown is also not affected. The results suggest that the interaction of tunneling electrons with defects created by hot holes is not a viable mechanism for explaining the catastrophic breakdown of the oxide layer in field-effect transistors. © 2002 American Institute of Physics.
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73.61.Ng Insulators
73.50.Fq High-field and nonlinear effects
71.55.Ht Other nonmetals
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.40.Gk Tunneling
77.22.Jp Dielectric breakdown and space-charge effects
85.30.Tv Field effect devices

Size and grain-boundary effects of a gold nanowire measured by conducting atomic force microscopy

Alexander Bietsch and Bruno Michel

Appl. Phys. Lett. 80, 3346 (2002); http://dx.doi.org/10.1063/1.1473868 (3 pages) | Cited 27 times

Online Publication Date: 29 April 2002

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The resistivities of thin metal films and wires are highly sensitive to their polycrystalline structure and surface morphology because grain boundaries and surfaces provide additional scattering sites compared to bulk materials. Here, we investigated polycrystalline gold wires of nanometer-scale diameter that were—at some locations—connected through single grain boundaries. A detailed topography of the wires was recorded by atomic force microscopy. A Pt-coated tip in a conducting atomic force microscopy setup served as a mobile electrode to probe the resistance of a wire. Analyzing the topographical cross section and the resistance data allowed us to evaluate the effective specific resistivity of the wire as well as reflection coefficients of single grain boundaries. © 2002 American Institute of Physics.
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73.63.Bd Nanocrystalline materials
61.46.-w Structure of nanoscale materials
61.72.Mm Grain and twin boundaries
68.37.Ps Atomic force microscopy (AFM)
85.40.Ls Metallization, contacts, interconnects; device isolation
68.35.B- Structure of clean surfaces (and surface reconstruction)
72.20.Fr Low-field transport and mobility; piezoresistance

Photoluminescence and photoluminescence excitation studies of as-grown and P-implanted GaN: On the nature of yellow luminescence

H. Y. Huang, C. H. Chuang, C. K. Shu, Y. C. Pan, W. H. Lee, W. K. Chen, W. H. Chen, and M. C. Lee

Appl. Phys. Lett. 80, 3349 (2002); http://dx.doi.org/10.1063/1.1476400 (3 pages) | Cited 8 times

Online Publication Date: 29 April 2002

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We have studied optical and electronic properties of isoelectronic P-implanted GaN films grown by metalorganic chemical vapor phase epitaxy. After rapid thermal annealing, a strong emission band around 430 nm was observed, which is attributed to the recombination of exciton bound to isoelectronic P-hole traps. From the Arrhenius plot, the hole binding energy of ∼ 180 meV and the exciton localization energy of 28 meV were obtained. According to first-principle total-energy calculations, the implantation process likely introduced NI and P-related defects. By using photoluminescence excitation technique, we found that the P-implantation-induced localized states not only increase the yellow luminescence but also suppress the transitions from the free carriers to deep levels. © 2002 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
71.55.Eq III-V semiconductors
81.05.Ea III-V semiconductors
61.72.uj III-V and II-VI semiconductors
61.80.Jh Ion radiation effects
61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
71.35.-y Excitons and related phenomena
71.15.Nc Total energy and cohesive energy calculations

Band line-up and mechanisms of current flow in n-GaN/p-SiC and n-AlGaN/p-SiC heterojunctions

A. Y. Polyakov, N. B. Smirnov, A. V. Govorkov, E. A. Kozhukhova, B. Luo, J. Kim, R. Mehandru, F. Ren, K. P. Lee, S. J. Pearton, A. V. Osinsky, and P. E. Norris

Appl. Phys. Lett. 80, 3352 (2002); http://dx.doi.org/10.1063/1.1477273 (3 pages) | Cited 6 times

Online Publication Date: 29 April 2002

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The properties of n-GaN/p-SiC and n-AlGaN/p-SiC heterojunctions (HJ) prepared by hydride vapor phase epitaxy (HVPE) on 4H SiC substrates are reported. It is shown that the GaN/p-SiC HJ is staggered type II with the conduction bandoffset and the valence bandoffset values, respectively, ΔEc = −0.49 eV and ΔEv = 0.65 eV. When changing GaN for AlGaN with Al mole fraction of x = 0.25–0.3 the band alignment becomes normal type I with ΔEc = 0.2 eV and ΔEv = 0.6 eV. Current–voltage characteristics of both heterojunctions bear evidence of strong tunneling via defect states. The tunneling was found to be more pronounced in the AlGaN/SiC HJs even though these showed no evidence of formation of dark line defects at the interface, in contrast to GaN/SiC. © 2002 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Gk Tunneling
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Anisotropy in breakdown field of 4H–SiC

Shun-ichi Nakamura, Hironori Kumagai, Tsunenobu Kimoto, and Hiroyuki Matsunami

Appl. Phys. Lett. 80, 3355 (2002); http://dx.doi.org/10.1063/1.1477271 (3 pages) | Cited 9 times

Online Publication Date: 29 April 2002

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The breakdown fields along the 〈11math0〉 and 〈03math8〉 directions in 4H–SiC have been measured. For the measurements, epitaxial p+n diodes with mesa structures were fabricated on the (11math0) and (03math8) faces, and they showed good rectification properties and avalanche breakdown. The breakdown fields along these directions calculated from the breakdown voltage were found to be about three quarters of that along the 〈0001〉 direction in 4H–SiC. The cause of the anisotropy in breakdown field is discussed. © 2002 American Institute of Physics.
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85.30.Kk Junction diodes
73.50.Fq High-field and nonlinear effects
73.40.Ei Rectification
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
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