• Korean Journal of Optics and Photonics
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• v.13 no.1
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• pp.51-57
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• 2002

We have calculated the optimum refractive index and normalized thickness of a single layer antireflection coating on the facet of buried channel waveguides as a function of waveguide width for several waveguide depths using the angular spectrum method and field profiles obtained by the effective index method (EIM) and the variational method (VM), respectively, and discussed the results. In the area of large waveguide width, the optimum parameters of a single layer antireflection coating obtained by both methods are almost the same. However, as waveguide width decreases, the parameters obtained by the VM approach those of a single layer antireflection coating between cladding layer and air, while those obtained by the EIM do not approach those, and the difference between the two parameters is large. The tolerance maps of the quasi-TE and quasi-TM modes obtained by the VM for square waveguides are located in almost the same area regardless of refractive index contrast, while those obtained by the free space radiation mode (FSRM) method for refractive index contrast of 10% are located in the different area. Thus, we think that the tolerance maps obtained by the VM are more exact than those obtained by the FSRM method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.818-821
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• 2012

This paper have analyzed the change of threshold voltage for conduction path of double gate(DG) MOSFET. The threshold voltage roll-off among the short channel effects of DGMOSFET have become obstacles of precise device operation. The analytical solution of Poisson's equation have been used to analyze the threshold voltage, and Gaussian function been used as carrier distribution to analyze closely for experimental results. The threshold voltages for conduction path have been analyzed for device parameters such as channel length, channel thickness, gate oxide thickness and doping concentration. Since this potential model has been verified in the previous papers, we have used this model to analyze the threshold voltage. Resultly, we know the threshold voltage is greatly influenced on the change of conduction path for device parameters of DGMOSFET.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.825-828
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• 2012

This paper have analyzed the change of breakdown voltage for conduction path of double gate(DG) MOSFET. The low breakdown voltage among the short channel effects of DGMOSFET have become obstacles of device operation. The analytical solution of Poisson's equation have been used to analyze the breakdown voltage, and Gaussian function been used as carrier distribution to analyze closely for experimental results. The change of breakdown voltages for conduction path have been analyzed for device parameters such as channel length, channel thickness, gate oxide thickness and doping concentration. Since this potential model has been verified in the previous papers, we have used this model to analyze the breakdown voltage. Resultly, we know the breakdown voltage is greatly influenced on the change of conduction path for device parameters of DGMOSFET.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.11
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• pp.2511-2516
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• 2012

This paper have analyzed the change of threshold voltage for conduction path of double gate(DG) MOSFET. The threshold voltage roll-off among the short channel effects of DGMOSFET have become obstacles of precise device operation. The analytical solution of Poisson's equation have been used to analyze the threshold voltage, and Gaussian function been used as carrier distribution to analyze closely for experimental results. The threshold voltages for conduction path have been analyzed for device parameters such as channel length, channel thickness, gate oxide thickness and doping concentration. Since this potential model has been verified in the previous papers, we have used this model to analyze the threshold voltage. Resultly, we know the threshold voltage is greatly influenced on the change of conduction path for device parameters of DGMOSFET.

• Korean Journal of Optics and Photonics
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• v.13 no.6
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• pp.461-466
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• 2002

Fiber-optic comb filters using a side-polished fiber coupler are proposed as multi-channel isolation filters on wavelength division multiplexing systems. We have demonstrated that the coupling efficiency between two waveguides is improved by the intermediate coupling layer in spite of the decrease of the optical power transfer between two waveguides due to the high-order modes of the overlay waveguide coupled with the side-polished single-mode fiber. When LiNbO$_3$with a 200-${\mu}{\textrm}{m}$-thickness was applied as a planar-overlay-waveguide, the comb filtering characteristics with a 4 nm-channel-spacing were achieved and the maximum power coupling occurred at the 1-${\mu}{\textrm}{m}$-thickness and the refractive index in range 1.52 to 1.53 of an intermediate coupling layer. If the intermediate coupling layer is optimized, an extinction ratio with more than 20 dB can be obtained. These experimental results are in good agreement with the BPM simulation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.865-868
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• 2006

In this paper, the subthreshold swing has been analyzed for double gate FinFET under channel length of 20nm. The analytical current model has been developed, including thermionic current and tunneling current models. The potential distribution by Poisson equation and carrier distribution by Maxwell-Boltzman statistics are used to calculate thermionic emission current, and WKB(Wentzel-Framers-Brillouin) approximation to tunneling current. The cutoff current is obtained by simple adding two currents since two current is independent. The subthreshold swings by this model are compared with those by two dimensional simulation and two values are good agreement. Since the tunneling current increases especially under channel length of 10nm, the characteristics of subthreshold swing is degraded. The channel and gate oxide thickness have to be fabricated as thin as possible to decrease this short channel effects and this process has to be developed. The subthreshold swings as a function of channel doping concentrations are obtained.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.11
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• pp.2621-2626
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• 2013

This paper has presented the potential distribution for asymmetric double gate(DG) MOSFET, and sloved Poisson equation to obtain the analytical solution of potential distribution. The symmetric DGMOSFET where both the front and the back gates are tied together is three terminal device and has the same current controllability for front and back gates. Meanwhile the asymmetric DGMOSFET is four terminal device and can separately determine current controllability for front and back gates. To approximate with experimental values, we have used the Gaussian function as doping distribution in Poisson equation. The potential distribution has been observed for gate bias voltage and gate oxide thickness and channel doping concentration of the asymmetric DGMOSFET. As a results, we know potential distribution is greatly changed for gate bias voltage and gate oxide thickness, especially for gate to increase gate oxide thickness. Also the potential distribution for source is changed greater than one of drain with increasing of channel doping concentration.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.691-694
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• 2013

This paper has presented the potential distribution for asymmetric double gate(DG) MOSFET, and sloved Poisson equation to obtain the analytical solution of potential distribution. The symmetric DGMOSFET where both the front and the back gates are tied together is three terminal device and has the same current controllability for front and back gates. Meanwhile the asymmetric DGMOSFET is four terminal device and can separately determine current controllability for front and back gates. To approximate with experimental values, we have used the Gaussian function as charge distribution in Poisson equation. The potential distribution has been observed for gate bias voltage and gate oxide thickness and channel doping concentration of the asymmetric DGMOSFET. As a results, we know potential distribution is greatly changed for gate bias voltage and gate oxide thickness, especially for gate to increase gate oxide thickness. Also the potential distribution for source is changed greater than one of drain with increasing of channel doping concentration.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.2
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• pp.425-430
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• 2014

This paper analyzed the change of subthreshold current for gate oxide thickness of double gate(DG) MOSFET. Poisson's equation had been used to analyze the potential distribution in channel, and Gaussian function had been used as carrier distribution. The potential distribution was obtained as the analytical function of channel dimension, using the boundary condition. The subthreshold current had been analyzed for gate oxide thickness, and projected range and standard projected deviation of Gaussian function. Since this analytical potential model was verified in the previous papers, we used this model to analyze the subthreshold current. Resultly, analytical model showed that subthreshold current was influenced by parameters of Gaussian function and gate oxide thickness of DGMOSFET.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.4
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• pp.793-798
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• 2012

In this paper, dependence of subthreshold current has been analyzed for doping distribution and channel structure of double gate(DG) MOSFET. The charge distribution of Gaussian function validated in previous researches has been used to obtain potential distribution in Poisson equation. Since DGMOSFETs have reduced short channel effects with improvement of current controllability by gate voltages, subthreshold characteristics have been enhanced. The control of current in subthreshold region is very important factor related with power consumption for ultra large scaled integration. The deviation of threshold voltage has been qualitatively analyzed using the changes of subthreshold current for gate voltages. Subthreshold current has been influenced by doping distribution and channel dimension. In this study, the influence of channel length and thickness on current has been analyzed according to intensity and distribution of doping.