Tuesday, 18 May 2010

Some papers (May 2010) I've found interesting...

Substrate Noise Coupling Mechanisms in Lightly Doped CMOS Transistors

Bronckers, S.;   Van der Plas, G.;   Vandersteen, G.;   Rolain, Y.;  
Interuniversity Microelectronics Centre (IMEC), Leuven, Belgium 
This paper appears in: Instrumentation and Measurement, IEEE Transactions on
Issue Date: June 2010
Volume:
59 Issue:6
On page(s): 1727 - 1733
ISSN: 0018-9456
Digital Object Identifier: 10.1109/TIM.2009.2024370 
Date of Publication: 03 May 2010
Date of Current Version: 10 May 2010

Substrate noise issues are a showstopper for the smooth integration of analog and digital circuitries on the same die. For the designer, it is not known how substrate noise couples into the transistors of the analog circuitry. This paper reveals the dominant coupling mechanisms with simulations and the corresponding measurements in a 0.13-$muhbox{m}$ triple-well common-source complementary metal–oxide–semiconductor (CMOS) transistor integrated on a lightly doped substrate. Substrate noise couples in either the ground or the bulk of the transistor. It is demonstrated that the importance of the coupling mechanisms depends on the resistance of the ground interconnect. For the technology node used, measurements show that substrate noise isolation is optimal for a ground resistance of 0.8 $Omega$.


Thermal shot noise in top-gated single carbon nanotube field effect transistors

Chaste, J.;   Pallecchi, E.;   Morfin, P.;   Feve, G.;   Kontos, T.;   Berroir, J.-M.;   Hakonen, P.;   Placais, B.;  
Laboratoire Pierre Aigrain, Ecole Normale Supérieure, CNRS (UMR 8551), Université P. et M. Curie, Université D. Diderot, 24, rue Lhomond, 75231 Paris Cedex 05, France 
This paper appears in: Applied Physics Letters
Issue Date: May 2010
Volume:
96 Issue:19
On page(s): 192103 - 192103-3
ISSN: 0003-6951
Digital Object Identifier: 10.1063/1.3425889 
Date of Current Version: 13 May 2010


The high-frequency transconductance and current noise of top-gated single carbon nanotube transistors have been measured and used to investigate hot electron effects in one-dimensional transistors. Results are in good agreement with a theory of one-dimensional nanotransistor. In particular the prediction of a large transconductance correction to the Johnson–Nyquist thermal noise formula is confirmed experimentally. Experiment shows that nanotube transistors can be used as fast charge detectors for quantum coherent electronics with a resolution of
13 μe/
 Hz

in the 0.2–0.8 GHz band. 

Dielectric constants of atomically thin silicon channels with double gate

Kageshima, Hiroyuki;   Fujiwara, Akira;  
NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198, Japan 
This paper appears in: Applied Physics Letters
Issue Date: May 2010
Volume: 96 Issue:19
On page(s): 193102 - 193102-3
ISSN: 0003-6951
Digital Object Identifier: 10.1063/1.3427364 
Date of Current Version: 13 May 2010
Dielectric constants of Si (111) nanofilms with the double gate are studied in the full inversion regime by using the first-principles calculation. The calculations show that the dielectric constants are significantly smaller than that of the bulk. Further, the dielectric constants depend on the conduction type as well as on the film thickness. They also oscillate with a 2-bilayer-thickness for the p-channel case as the film thickness decreases. The suppressed dielectric constants are found in the channel center as well as in the channel surface. These findings open the way to artificial control of the dielectric constant in semiconductor nanostructures.
 

Charge carrier densities in chemically doped organic semiconductors verified by two independent techniques

Lehnhardt, M.;   Hamwi, S.;   Hoping, M.;   Reinker, J.;   Riedl, T.;   Kowalsky, W.;  
Institute for High-Frequency Technology, Technical University of Braunschweig, Schleinitzstr. 22, D-38106 Braunschweig, Germany 
This paper appears in: Applied Physics Letters
Issue Date: May 2010
Volume: 96 Issue:19
On page(s): 193301 - 193301-3
ISSN: 0003-6951
Digital Object Identifier: 10.1063/1.3427416 
Date of Current Version: 13 May 2010

The charge carrier density of the p-type doped organic semiconductor 2,7-bis(9-carbazolyl)-9,9-spirobifluorene is determined for varied doping concentrations. As p-type dopant molybdenum trioxide is used. We determine the carrier density by measuring the polaron induced optical absorption and by a capacitance-voltage analysis. We show that both results are in excellent agreement. An almost linear dependence of the charge carrier density on the doping concentration is observed. Carrier densities on the order of 1018 cm-3 at a dopant concentration of 1 mol % can be achieved. Overall, a low doping efficiency on the order of 2%–4.5% is evidenced.


The effect of traps on the performance of graphene field-effect transistors

Zhu, J.;   Jhaveri, R.;   Woo, J. C. S.;  
Department of Electrical Engineering, University of California–Los Angeles, Los Angeles, California 90095-1594, USA 
This paper appears in: Applied Physics Letters
Issue Date: May 2010
Volume:
96 Issue:19
On page(s): 193503 - 193503-3
ISSN: 0003-6951
Digital Object Identifier: 10.1063/1.3428785 
Date of Current Version: 13 May 2010

This paper studies the performance degradation of graphene field-effect transistors due to the presence of traps. The mobile charge modulation by gate voltage is degraded because of immobile trapped charges. As a result the current is reduced and the on/off ratio is decreased. Extracted mobility using transconductance method is shown to be underestimated considerably due to the effect of traps.
 

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