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4 Feb 2002

Volume 80, Issue 5, pp. 707-899

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Influence of the recharging process on the dark current noise in quantum-well infrared photodetectors

Robert Rehm, Harald Schneider, Martin Walther, and Peter Koidl

Appl. Phys. Lett. 80, 862 (2002); http://dx.doi.org/10.1063/1.1435071 (3 pages) | Cited 8 times

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We show that the dark curent noise spectrum of an In0.30Ga0.70As/GaAs quantum-well infrared photodetector (QWIP) is characterized by two plateau-like frequency regions. At high frequencies, the observed noise current is due to the generation–recombination noise of carriers, which have been emitted thermionically from the quantum wells into the continuum. In the low-frequency regime, an additional contribution to the noise current is caused by the redistribution of space charges, that occurs on a time scale similar to the dielectric relaxation time. © 2002 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
73.63.Hs Quantum wells
72.70.+m Noise processes and phenomena

Simple fabrication scheme for sub-10 nm electrode gaps using electron-beam lithography

K. Liu, Ph. Avouris, J. Bucchignano, R. Martel, S. Sun, and J. Michl

Appl. Phys. Lett. 80, 865 (2002); http://dx.doi.org/10.1063/1.1436275 (3 pages) | Cited 70 times

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An innovative and simple method, based on electron-beam (e-beam) overlapping and overexposure techniques, is developed to fabricate sub-10 nm electrode gaps with very good electrical properties. Gaps with 4 to 10 nm spacing can be fabricated using a proper e-beam dose and pattern-developing time. The fabrication yield is nearly 100% for 8–9 nm gaps, but significantly smaller for 3–4 nm gaps. The gap leakage resistance is around 1012–1013 Ω, implying very good isolation. As an example, we present a transport study on a single 8 nm Co particle junction using a 10 nm gap. © 2002 American Institute of Physics.
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81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
85.35.-p Nanoelectronic devices
81.07.Lk Nanocontacts
75.50.Cc Other ferromagnetic metals and alloys
75.50.Tt Fine-particle systems; nanocrystalline materials
81.07.Nb Molecular nanostructures

Light coupling mechanism of quantum grid infrared photodetectors

J. Mao, Amlan Majumdar, K. K. Choi, D. C. Tsui, K. M. Leung, C. H. Lin, T. Tamir, and G. A. Vawter

Appl. Phys. Lett. 80, 868 (2002); http://dx.doi.org/10.1063/1.1445484 (3 pages) | Cited 6 times

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Rigorous electromagnetic modeling based on a modal solution of the pertinent boundary-value problem was performed to study the light coupling mechanism in quantum grid infrared photodetectors with lamellar patterns. Our theory shows that vertical field component and absorption quantum efficiency η can be strongly enhanced by judiciously adjusting the width w of individual grid lines. This enhancement is further increased if the top of the grid lines is covered by metal, which behave as a collection of dipole scatterers. We have experimentally verified the dipole scattering characteristics with different w, and found that the variation of η agrees very well with the theory. We also found that, as expected, the conductivity of the metal strips affects η significantly due to internal dissipation. © 2002 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
02.60.Lj Ordinary and partial differential equations; boundary value problems

Femtosecond data storage, processing, and search using collective excitations of a macroscopic quantum state

D. Mihailovic, D. Dvorsek, V. V. Kabanov, J. Demsar, L. Forró, and H. Berger

Appl. Phys. Lett. 80, 871 (2002); http://dx.doi.org/10.1063/1.1447594 (3 pages) | Cited 15 times

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An ultrafast parallel data processor is described in which amplitude mode excitations of a charge density wave are used to encode data on the surface of a 1 T-TaS2 crystal. The data are written, manipulated, and read using parallel femtosecond laser pulse beams, and the operation of a database search algorithm is demonstrated on a two-element array. © 2002 American Institute of Physics.
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42.79.Vb Optical storage systems, optical disks
42.70.Ln Holographic recording materials; optical storage media
71.45.Lr Charge-density-wave systems
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Current-induced fluorescence quenching in organic light-emitting diodes

Ralph H. Young, Ching W. Tang, and Alfred P. Marchetti

Appl. Phys. Lett. 80, 874 (2002); http://dx.doi.org/10.1063/1.1445271 (3 pages) | Cited 75 times

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The electroluminescence quantum efficiency of organic light-emitting diodes with a doped Alq [tris(8-quinolinolato)aluminum] emitting layer is found to decrease markedly with increasing current density. This phenomenon was investigated using multilayer device structures permitting bipolar or unipolar carrier transport, and luminescence measurements with simultaneous optical and electrical excitation. The loss of electroluminescence quantum efficiency is attributed to the quenching of the singlet-excited state of the dopant by a cationic species. © 2002 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.55.Kz Solid organic materials

Field-emission properties of multihead silicon cone arrays coated with cesium

W. K. Wong, F. Y. Meng, Q. Li, F. C. K. Au, I. Bello, and S. T. Lee

Appl. Phys. Lett. 80, 877 (2002); http://dx.doi.org/10.1063/1.1446990 (3 pages) | Cited 18 times

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Field emission from multihead silicon (Si) cones was substantially improved by cesium (Cs) coating. Increasing the Cs coating lowered the emission turn-on field (for 10 μA/cm2) from 25 V/μm to a saturated value of 13 V/μm, while the threshold field (for 10 mA/cm2) decreased by 30%, dropping from 27 V/μm for Si cones coated with 1.8 monolayers (ML) of Cs to a saturated value of 19 V/μm with 4.1 ML of Cs. The Cs-treated Si cones could give an emission current density that was three to ten times that delivered by bare Si cones. The work function reduced by a factor of 1.43 for Si cones coated with 4.9 ML of Cs with reference to the untreated Si cones. From the slope of Fowler–Nordheim plot, the field enhancement factor β was found to increase by a factor of 2.02 for Si cones coated with 2.5 ML of Cs and then reduce to 1.57 after the 4.9 ML of Cs deposition. Reduction of the factor β might occur because of a thick Cs layer, which could flatten the sharp cone features. Stability test showed that no current decay was observed at a current density of 0.8 mA/cm2 under a constant applied field of 16 V/μm during the 10 h investigation. © 2002 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
73.30.+y Surface double layers, Schottky barriers, and work functions

Dose-energy match for the formation of high-integrity buried oxide layers in low-dose separation-by-implantation-of-oxygen materials

Meng Chen, Xiang Wang, Jing Chen, Xianghua Liu, Yeming Dong, Yuehui Yu, and Xi Wang

Appl. Phys. Lett. 80, 880 (2002); http://dx.doi.org/10.1063/1.1447005 (3 pages) | Cited 23 times

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High-quality low-dose separation-by-implantation-of-oxygen (SIMOX) silicon-on-insulator (SOI) wafers have been fabricated from a series of good matches of dose-energy combinations. The results reveal that a wafer fabricated at an optimum dose-energy match has a superior SOI layer with a low threading dislocation density, a high-integrity buried oxide (BOX) layer with a minimal detectable silicon island density and a low pinhole density. This work introduces an approach to flexibly control the thickness of both SOI and BOX layers, allowing the fabrication of ultrathin SIMOX wafers with ultrathin SOI and BOX layers, and improving the throughput capacity by selecting good dose-energy matches. A possible mechanism is discussed.© 2002 American Institute of Physics.
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85.40.Ry Impurity doping, diffusion and ion implantation technology
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