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Centeral Electric Field and Threshold Voltage in Accumulation Mode Junctionless Cylindrical Surrounding Gate MOSFET Hakkee Jung
International Journal of Electrical and Computer Engineering (IJECE) Vol 8, No 2: April 2018
Publisher : Institute of Advanced Engineering and Science

Transfer characteristics is presented using analytical potential distribution of accumulation-mode junctionless cylindrical surrounding-gate (JLCSG) MOSFET, and deviation of center electric field at threshold voltage is analyzed for channel length and oxide thickness. Threshold voltages presented in this paper is good agreement with results of other compared papers, and transfer characteristics is agreed with those of two-dimensional simulation. The most important factor to determine threshold voltage is center electric field at source because the greater part of electron flows through center axis of JLCSG MOSFET. As a result of analysis for center electric field at threshold voltage, center electric field is decreased with reduction of channel length due to drain induced barrier lowering. Center electric field is increased with decrease of oxide thickness, and deviation of center electric field for channel length is significantly occurred with decrease of oxide thickness.

Subthreshold swing model using scale length for sub-10 nm junction-based double-gate MOSFETs Hakkee Jung
International Journal of Electrical and Computer Engineering (IJECE) Vol 10, No 2: April 2020
Publisher : Institute of Advanced Engineering and Science

We propose an analytical model for subthreshold swing using scale length for sub-10 nm double gate (DG) MOSFETs. When the order of the calculation for the series type potential distribution is increased it is possible to obtain accuracy, but there is a problem that the calculation becomes large. Using only the first order calculation of potential distribution, we derive the scale length λ1 and use it to obtain an analytical model of subthreshold swing. The findings show this subthreshold swing model is in concordance with a 2D simulation. The relationship between the channel length and silicon thickness, which can analyze the subthreshold swing using λ1, is derived by the relationship between the scale length and the geometric mean of the silicon and oxide thickness. If the silicon thickness and oxide film thickness satisfy the condition of (Lg-0.215)/6.38 > tsi(=tox), it is found that the result of this model agrees with the results using higher order calculations, within a 4% error range.

Threshold voltage roll-off for sub-10 nm asymmetric double gate MOSFET Hakkee Jung
International Journal of Electrical and Computer Engineering (IJECE) Vol 9, No 1: February 2019
Publisher : Institute of Advanced Engineering and Science

Threshold voltage roll-off is analyzed for sub-10 nm asymmetric double gate (DG) MOSFET. Even asymmetric DGMOSFET will increase threshold voltage roll-off in sub-10 nm channel length because of short channel effects due to the increase of tunneling current, and this is an obstacle against the miniaturization of asymmetric DGMOSFET. Since asymmetric DGMOSFET can be produced differently in top and bottom oxide thickness, top and bottom oxide thicknesses will affect the threshold voltage roll-off. To analyze this, thermal emission current and tunneling current have been calculated, and threshold voltage roll-off by the reduction of channel length has been analyzed by using channel thickness and top/bottom oxide thickness as parameters. As a result, it is found that, in short channel asymmetric double gate MOSFET, threshold voltage roll-off is changed greatly according to top/bottom gate oxide thickness, and that threshold voltage roll-off is more influenced by silicon thickness. In addition, it is found that top and bottom oxide thickness have a relation of inverse proportion mutually for maintaining identical threshold voltage. Therefore, it is possible to reduce the leakage current of the top gate related with threshold voltage by increasing the thickness of the top gate oxide while maintaining the same threshold voltage.

SPICE model of drain induced barrier lowering in sub-10 nm junctionless cylindrical surrounding gate MOSFET Hakkee Jung
International Journal of Electrical and Computer Engineering (IJECE) Vol 10, No 2: April 2020
Publisher : Institute of Advanced Engineering and Science

We propose a SPICE Drain Induced Barrier Lowering (DIBL) model for sub-10 nm Junctionless Cylindrical Surrounding Gate (JLCSG) MOSFETs. The DIBL shows the proportionl relation to the -3 power of the channel length Lg and the 2 power of silicon thickness in MOSFET having a rectangular channel, but this relation cannot be used in cylindrical channel because of the difference in channel structure. The subthreshold currents, including the tunneling current from the WKB (Wentzel-Kramers-Brillouin) approximation as well as the diffusion-drift current, are used in the model. The constant current method is used to define the threshold voltage as the gate voltage at a constant current, (2πR/Lg)10-7 A for channel length and channel radius R. The central potential of the JLCSG MOSFET is determined by the Poisson equation. As a result, it can be seen that the DIBL of the JLCSG MOSFET is proportional to the –2.76 power of the channel length, to the 1.76 power of the channel radius, and linearly to the oxide film thickness. At this time, we observe that the SPICE parameter, the static feedback coefficient, has a value less than 1 1, and this model can be used to analyze the DIBL of the JLCSG MOSFET.

Analysis of on-off current ratio in asymmetrical junctionless double gate MOSFET using high-k dielectric materials Hakkee Jung; Byungon Kim
International Journal of Electrical and Computer Engineering (IJECE) Vol 11, No 5: October 2021
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/ijece.v11i5.pp3882-3889

The variation of the on-off current ratio is investigated when the asymmetrical junctionless double gate MOSFET is fabricated as a SiO2/high-k dielectric stacked gate oxide. The high dielectric materials have the advantage of reducing the short channel effect, but the rise of gate parasitic current due to the reduction of the band offset and the poor interface property with silicon has become a problem. To overcome this disadvantage, a stacked oxide film is used. The potential distributions are obtained from the Poission equation, and the threshold voltage is calculated from the second derivative method to obtain the on-current. As a result, this model agrees with the results from other papers. The on-off current ratio is in proportion to the arithmetic average of the upper and lower high dielectric material thicknesses. The on-off current ratio of 104 or less is shown for SiO2, but the on-off current ratio for TiO2 (k=80) increases to 107 or more.

Threshold Voltage Roll-off by Structural Parameters for Sub-10 nm Asymmetric Double Gate MOSFET Hakkee Jung
TELKOMNIKA (Telecommunication Computing Electronics and Control) Vol 16, No 5: October 2018
Publisher : Universitas Ahmad Dahlan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12928/telkomnika.v16i5.10248

This study is to analyze threshold voltage roll-off according to structural parameters of sub-10 nm asymmetric double gate MOSFET. In case of sub-10nm channel length, because of short channel effects resulting from the rapid increase of tunneling current, even asymmetric double gate (DG) MOSFET, which has been developed for reducing short channel effects, will increase threshold voltage roll-off, and this is an obstacle against the miniaturization of asymmetric DGMOSFET. Especially, since asymmetric DGMOSFET can be produced differently in top and bottom oxide thickness, top/bottom oxide thickness will affect the threshold voltage roll-off. To analyze this, thermal emission current and tunneling current model have been calculated, and threshold voltage roll-off in accordance with the reduction of channel length has been analyzed by using channel thickness and top/bottom oxide thickness as parameters. As a result, it is found that, in short channel asymmetric double gate MOSFET, threshold voltage roll-off is changed greatly according to top/bottom gate oxide thickness, and that threshold voltage roll-off, in particular, is generated more greatly according to silicon thickness. In addition, it is found that top and bottom oxide thickness have a relation of inverse proportion mutually for maintaining identical threshold voltage

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