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10 Oct 2005

Volume 87, Issue 15, Articles (15xxxx)

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Appl. Phys. Lett. 87, 151103 (2005); http://dx.doi.org/10.1063/1.2089157 (3 pages)

Andrew B. Greytak, Carl J. Barrelet, Yat Li, and Charles M. Lieber
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High-mobility Sb-doped p-type ZnO by molecular-beam epitaxy

F. X. Xiu, Z. Yang, L. J. Mandalapu, D. T. Zhao, J. L. Liu, and W. P. Beyermann

Appl. Phys. Lett. 87, 152101 (2005); http://dx.doi.org/10.1063/1.2089183 (3 pages) | Cited 119 times

Online Publication Date: 4 October 2005

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Reproducible Sb-doped p-type ZnO films were grown on n-Si (100) by electron-cyclotron-resonance-assisted molecular-beam epitaxy. The existence of Sb in ZnO:Sb films was confirmed by low-temperature photoluminescence measurements. An acceptor-bound exciton (A°X) emission was observed at 3.358 eV at 8 K. The acceptor energy level of the Sb dopant is estimated to be 0.2 eV above the valence band. Temperature-dependent Hall measurements were performed on Sb-doped ZnO films. At room temperature, one Sb-doped ZnO sample exhibited a low resistivity of 0.2 Ω cm, high hole concentration of 1.7×1018 cm−3 and high mobility of 20.0 cm2/V s. This study suggests that Sb is an excellent dopant for reliable and reproducible p-type ZnO fabrication.
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73.61.Ga II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Et II-VI semiconductors
71.35.-y Excitons and related phenomena
71.20.Nr Semiconductor compounds
72.20.My Galvanomagnetic and other magnetotransport effects
61.72.uj III-V and II-VI semiconductors

Carbon nanotube gated lateral resonant tunneling field-effect transistors

D. P. Wang, B. R. Perkins, A. J. Yin, A. Zaslavsky, J. M. Xu, R. Beresford, and G. L. Snider

Appl. Phys. Lett. 87, 152102 (2005); http://dx.doi.org/10.1063/1.2089177 (3 pages) | Cited 6 times

Online Publication Date: 4 October 2005

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We have produced a lateral resonant tunneling field-effect transistor using a Y-junction multiwalled carbon nanotube as the dual gate on a narrow channel etched from a modulation-doped GaAs/AlGaAs heterostructure. When the Y-junction nanotube is negatively biased, electrons traveling from source to drain along the channel face a voltage-tunable electrostatic double-barrier potential. We measured the three-terminal IDS(VDS,VGS) characteristics of the device at 4.2 K and observed gate-induced structure in the transconductance and negative differential resistance in the drain current. We interpret the data in terms of resonant tunneling through one-dimensional subbands confined by a self-consistently calculated electrostatic potential.
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85.30.Tv Field effect devices
85.35.Kt Nanotube devices

Radiation-induced trapping and charge transport in a smectic liquid crystal

Katherine Hudson, Brett Ellman, Volker Gettwert, Yulia Getmanenko, and Robert J. Twieg

Appl. Phys. Lett. 87, 152103 (2005); http://dx.doi.org/10.1063/1.2099543 (3 pages) | Cited 6 times

Online Publication Date: 4 October 2005

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We have studied changes in the hole transport properties of a smectic liquid crystalline semiconductor resulting from high-energy electron irradiation. The “radiation doping” results in sharply increased shallow trap densities and the onset of nearly trap-limited hopping conduction. A simple semiquantitative model provides estimates of the trap lifetime and the irradiation energy required to create a single trap. Experimental techniques to overcome parasitic effects due to increased molecular ion densities in irradiated samples are also discussed.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.20.Ee Mobility edges; hopping transport
72.80.Le Polymers; organic compounds (including organic semiconductors)
72.80.Ph Liquid semiconductors
61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures
61.82.Fk Semiconductors
61.82.Pv Polymers, organic compounds
61.80.Fe Electron and positron radiation effects

Dependence of carrier mobility on grain mosaic spread in ⟨001⟩-oriented Si films grown on polycrystalline substrates

Woong Choi, Vladimir Matias, Jung-Kun Lee, and Alp T. Findikoglu

Appl. Phys. Lett. 87, 152104 (2005); http://dx.doi.org/10.1063/1.2103405 (3 pages) | Cited 7 times

Online Publication Date: 4 October 2005

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We studied the dependence of carrier mobility on grain mosaic spread for ⟨001⟩-oriented, 200-to-400-nm-thick Si thin films grown on polycrystalline metal substrates. The Hall mobility increased from 1% to 23% of that in bulk single-crystal Si with decreasing grain mosaic spread from 14° to 2°. For the same range of parameters, a model combining intragrain and grain boundary scattering yielded a decrease of the energy barrier height from 0.1 eV to less than 10−3 eV and an accompanying decrease of trap density from 6×1011 cm−2 to less than 3×1010 cm−2. These results demonstrate that, for polycrystalline Si films, improving the intergrain alignment is an effective and practical alternative to increasing the grain size to achieve enhanced mobility.
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73.61.Cw Elemental semiconductors
72.20.Ee Mobility edges; hopping transport
61.72.Mm Grain and twin boundaries

Influence of the dielectric constant of a polyvinyl phenol insulator on the field-effect mobility of a pentacene-based thin-film transistor

Yunseok Jang, Do Hwan Kim, Yeong Don Park, Jeong Ho Cho, Minkyu Hwang, and Kilwon Cho

Appl. Phys. Lett. 87, 152105 (2005); http://dx.doi.org/10.1063/1.2093940 (3 pages) | Cited 30 times

Online Publication Date: 5 October 2005

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The mobility of pentacene thin-film transistors (TFTs) is correlated with the dielectric properties of their insulators. We varied the dielectric properties of the poly(4-vinylphenol) insulators of such TFTs by changing the molar ratio of the prepolymer/cross-linking agent while keeping the surface potential of the insulator surface constant. It was found that the field-effect mobility of the pentacene TFTs increases with increases in the dielectric constant of the insulators. A small increase in the dielectric constant of the insulator (a 20% increase, 3.6–4.3) was found to result in a dramatic increase in the field-effect mobility of pentacene TFTs by a factor of 3 (0.26 to 0.81 cm2/V s).
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85.30.Tv Field effect devices
77.22.Ch Permittivity (dielectric function)

Improvement of the current-voltage characteristics of a tunneling dielectric by adopting a Si3N4/SiO2/Si3N4 multilayer for flash memory application

Sug Hun Hong, Jae Hyuck Jang, Tae Joo Park, Doo Seok Jeong, Miyoung Kim, Cheol Seong Hwang, and Jeong Yeon Won

Appl. Phys. Lett. 87, 152106 (2005); http://dx.doi.org/10.1063/1.2093932 (3 pages) | Cited 3 times

Online Publication Date: 7 October 2005

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Superior characteristics of an atomic-layer-deposited (ALD) Si3N4 layer and Si3N4/SiO2/Si3N4 stacked layers as a tunneling gate dielectric for nonvolatile flash memory application are reported. Compared to a single layer of SiO2 electric field-sensitive characteristics were obtained by barrier profile engineering with a stacked layer; a lower leakage current at a low field and a higher leakage current at a high field. The stacked dielectric layer showed Fowler–Nordheim tunneling. However, the interfacial potential barrier profile was somewhat smoothed by chemical interaction between the individual layers. The interfacial trap density of this dielectric with an ALD Si3N4 bottom layer was as low as 4×10−10/cm2 eV near the mid-gap energy state, but the reoxidation process degraded the interface quality. The degradation mechanism was studied.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
84.30.Sk Pulse and digital circuits
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