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8 Dec 2008

Volume 93, Issue 23, Articles (23xxxx)

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Appl. Phys. Lett. 93, 231101 (2008); http://dx.doi.org/10.1063/1.3040686 (3 pages)

Mads Brøkner Christiansen, Anders Kristensen, Sanshui Xiao, and Niels Asger Mortensen
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Effects of artificially structured micrometer holes on the transport behavior of Al-doped ZnO layers

M. T. Elm, T. Henning, P. J. Klar, and B. Szyszka

Appl. Phys. Lett. 93, 232101 (2008); http://dx.doi.org/10.1063/1.3040312 (3 pages) | Cited 2 times

Online Publication Date: 9 December 2008

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We study the transport properties of artificially structured n-type ZnO:Al thin films prepared by rf magnetron sputtering on glass substrates. The samples were patterned with an array of 4×4 and 8×8 μm2 holes. With decreasing hole size, the resistance of the samples increases. Filling the holes with Au or Al increases and decreases the resistance, respectively. All samples show a negative magnetoresistance, which becomes more pronounced with decreasing hole diameter. The filling of the holes with Au or Al reduces the effects of the artificial structuring on the magnetoresistance.
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72.20.-i Conductivity phenomena in semiconductors and insulators
73.61.Ga II-VI semiconductors
85.40.Hp Lithography, masks and pattern transfer
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Power dissipation spectra and terahertz intervalley transfer gain in bulk GaAs under high electric fields

Y. M. Zhu, T. Unuma, K. Shibata, K. Hirakawa, Y. Ino, and M. Kuwata-Gonokami

Appl. Phys. Lett. 93, 232102 (2008); http://dx.doi.org/10.1063/1.3039069 (3 pages) | Cited 6 times

Online Publication Date: 9 December 2008

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We have investigated terahertz radiation emitted from electrons photoexcited by femtosecond laser pulses in bulk GaAs under strong bias electric fields. Power dissipation spectra of electrons for step-function-like input electric fields have been obtained by calculating Fourier spectra of the measured terahertz traces. The cutoff frequency νc for negative power dissipation (i.e., gain) due to intervalley transfer is found to gradually increase with increasing electric fields below 50 kV/cm and saturate at ∼ 1 THz above 50 kV/cm at 300 K. From the temperature dependence of νc, it is found that νc is governed by the emission of optical phonons.
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78.70.Gq Microwave and radio-frequency interactions
78.47.-p Spectroscopy of solid state dynamics
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
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Low temperature diffusion length of excitons in gallium nitride measured by cathodoluminescence technique

Naoyuki Ino and Naoki Yamamoto

Appl. Phys. Lett. 93, 232103 (2008); http://dx.doi.org/10.1063/1.3040310 (3 pages) | Cited 7 times

Online Publication Date: 10 December 2008

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Monochromatic cathodoluminescence (CL) images of threading dislocations in GaN epitaxial layers were observed using a transmission electron microscopy combined with CL system. The carrier diffusion lengths were derived from the free exciton emission intensity profile of the dislocation contrast in the CL images. The carrier diffusion lengths in Si-doped and Mg-doped GaN were nearly the same and shorter than that in undoped GaN in the temperature range from 20 to 140 K, respectively. Moreover, the temperature dependence of the diffusion length shows that the acoustic phonon scattering mainly affects the exciton diffusion process at low temperatures from 40 to 120 K.
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73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
71.35.-y Excitons and related phenomena
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The chemical and electronic surface and interface structure of CuGaSe2 thin-film solar cell absorbers

M. Bär, M. Rusu, S. Lehmann, Th. Schedel-Niedrig, I. Lauermann, and M. C. Lux-Steiner

Appl. Phys. Lett. 93, 232104 (2008); http://dx.doi.org/10.1063/1.2998391 (3 pages) | Cited 4 times

Online Publication Date: 11 December 2008

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The chemical and electronic surface and interface structure of CuGaSe2 thin films was investigated by photoelectron spectroscopy. With bulk [Ga]/[Cu] ratios increasing from 0.94 to 1.39 a transition of the Cu:Ga:Se surface composition from 1:1:2 to 1:3:5 and a downward shift of the valence band maximum with respect to the Fermi energy were observed. The comparison with the conduction band minimum (CBM) of CdS reveals that at the CdS/CuGaSe2 interface the recombination barrier height simultaneously increases and a “clifflike” offset is formed to the CBM of CuGaSe2.
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73.20.At Surface states, band structure, electron density of states
68.47.Fg Semiconductor surfaces
84.60.Jt Photoelectric conversion
79.60.Bm Clean metal, semiconductor, and insulator surfaces
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
68.35.Dv Composition, segregation; defects and impurities
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Charge loss behavior of a metal-alumina-nitride-oxide-silicon-type flash memory cell with different levels of charge injection

Man Chang, Minseok Jo, Seonghyun Kim, Yongkyu Ju, Seungjae Jung, Joonmyoung Lee, Jaesik Yoon, Hyunsang Hwang, and Choongman Lee

Appl. Phys. Lett. 93, 232105 (2008); http://dx.doi.org/10.1063/1.3041642 (3 pages) | Cited 6 times

Online Publication Date: 11 December 2008

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We found that the charge loss behavior of metal-alumina-nitride-oxide-silicon-type flash memory was highly dependent on the amount of injected charge (Qinj). Beyond the critical level of Qinj, the direction of the dominant charge loss changed from pointing toward SiO2 to pointing toward Al2O3. The highly injected charges could cause the band bending of Al2O3, which reduced the tunneling distance across Al2O3 with the low conduction band offset. These results were verified by experimental results and theoretical device modeling through a comparison of the charge loss rate and the tunneling rate between a SiO2/Si3N4/SiO2 stack and a SiO2/Si3N4/Al2O3 stack.
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84.30.Sk Pulse and digital circuits
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