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6 Aug 2001

Volume 79, Issue 6, pp. 705-888

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Modification of the optical and photorefractive properties of Ce-doped strontium–barium niobate by co-doping with a nonphotorefractive La impurity

T. Volk, L. Ivleva, P. Lykov, D. Isakov, V. Osiko, and M. Wöhlecke

Appl. Phys. Lett. 79, 854 (2001); http://dx.doi.org/10.1063/1.1389320 (3 pages) | Cited 7 times

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We demonstrate a possibility to modify photorefractive properties of a ferroelectric crystal by means of controlling the ferroelectric phase transition. This is shown by an example of co-doping a photorefractive SBN-0.61:Ce crystal with a nonphotorefractive La impurity, which strongly lowers the ferroelectric phase transition and in turn drastically enhances the linear electrooptic coefficients. The observed low coercive fields enable us to build in SBN:(Ce+La) a reproducible fast switching of the energy transfer direction. This is done by an electric field switching which changes the sign of the two-beam coupling gain factor Γ. © 2001 American Institute of Physics.
Show PACS
42.70.Gi Light-sensitive materials
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
77.80.B- Phase transitions and Curie point
78.20.Jq Electro-optical effects
77.80.Fm Switching phenomena
78.20.-e Optical properties of bulk materials and thin films

Effects of singlet and triplet energy transfer to molecular dopants in polymer light-emitting diodes and their usefulness in chromaticity tuning

R. W. T. Higgins, A. P. Monkman, H.-G. Nothofer, and U. Scherf

Appl. Phys. Lett. 79, 857 (2001); http://dx.doi.org/10.1063/1.1389070 (3 pages) | Cited 32 times

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Efficient, white emission with Commission Internationale de L’Eclairage coordinates of 0.33, 0.42 is demonstrated from polymer light-emitting diodes operating at high brightness. An amino endcapped polyfluorene derivative doped with rubrene was used as the active layer, in combination with a poly(3,4-ethylenedioxythiophene) hole transport layer. Luminescence reaches 14950 Cd/m2 at a current density of 150 mA/cm2, and the maximum external quantum efficiency measured 1.05% for a bias voltage of 9.0 V. We observe a fall in external quantum efficiency relative to the undoped device, which we ascribe to an increased singlet–triplet annihilation rate at the dopant sites. © 2001 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
78.66.Qn Polymers; organic compounds
71.20.Rv Polymers and organic compounds

Schottky barrier rectifier with high current density using vanadium as barrier metal

J. S. Kim, H. H. Choi, S. H. Son, and S. Y. Choi

Appl. Phys. Lett. 79, 860 (2001); http://dx.doi.org/10.1063/1.1391402 (3 pages) | Cited 4 times

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This letter reports on an improved forward voltage drop (VF) and reverse leakage current (IR) in Schottky barrier rectifier using vanadium (V–SBR) as the barrier metal with a low barrier height (ϕB) and argon implantation. The VF for a V–SBR was as low as 0.25 V compared to 0.39 V for a molybdenum (Mo)–SBR at the same forward current density (JF) of 60 A/cm2. This study was able to achieve a good result for JF in SBR. Presently, the conventional Schottky rectifier with a low ϕB metal is used to achieve low VF, but at the expense of a high IR. To reduce this effect, crystalline Si was altered into amorphous Si using argon implantation on the n-epitaxial layer. Finally, a SBR with a high JF and low IR could be fabricated. © 2001 American Institute of Physics.
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85.30.Kk Junction diodes
73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
73.40.Ei Rectification

On the mechanism of interface trap generation under nonuniform channel-hot-electron stress and uniform carrier-injection stress in metal–oxide–semiconductor field-effect transistors

Kangguo Cheng, Jean-Pierre Leburton, Karl Hess, and Joseph W. Lyding

Appl. Phys. Lett. 79, 863 (2001); http://dx.doi.org/10.1063/1.1389318 (3 pages)

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The interpretation of the small hydrogen/deuterium isotope effect widely observed under uniform stress has been based on an implicit assumption that interface traps in the entire channel are passivated by deuterium after the deuterium annealing process. Through a stress/anneal process, we show that this assumption is incorrect. Instead, our results clearly suggest that interface trap generation under both nonuniform channel hot-carrier stress and uniform stress, such as Fowler–Nordheim tunneling and substrate electron injection, essentially follows the same mechanism, which is the breaking of Si–H(D) bonds and the release of hydrogen/deuterium at the oxide/silicon interface. © 2001 American Institute of Physics.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling
61.72.Cc Kinetics of defect formation and annealing
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Low-frequency noise in Al0.4Ga0.6N-based Schottky barrier photodetectors

S. L. Rumyantsev, N. Pala, M. S. Shur, R. Gaska, M. E. Levinshtein, V. Adivarahan, J. Yang, G. Simin, and M. Asif Khan

Appl. Phys. Lett. 79, 866 (2001); http://dx.doi.org/10.1063/1.1385191 (3 pages) | Cited 26 times

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The low-frequency generation recombination and the 1/f noise in AlGaN Schottky barrier photodetectors with high (40%) Al fraction has been investigated under forward and reverse bias conditions. The activation energy of local level contributing to noise was found to be Ea ≈ 1 eV. Depending on the forward current level, the noise from Schottky barrier or from the series resistance (contacts and/or base) predominates. The upper bound of the Hooge parameter in Al0.4Ga0.6N was estimated as α⩽10. © 2001 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
73.50.Td Noise processes and phenomena
73.30.+y Surface double layers, Schottky barriers, and work functions
85.60.Bt Optoelectronic device characterization, design, and modeling
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