• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.1
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• pp.88-92
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• 2010

Bottom gate and top gate field-effect transistor based carbon nanotube(CNT) were fabricated by CMOS process. Carbon nanotube directly grown by thermal chemical vapor deposition(CVD) using Ethylene ($C_2H_4$) gas at $700^{\circ}C$. The growth properties of CNTs on the device were analyzed by SEM and AFM. The electrical transport characteristics of CNT FET were investigated by I-V measurement. Transport through the nanotubes is dominated by holes at room temperature. By varying the gate voltage, bottom gate and top gate field-effect transistor successfully modulated the conductance of FET device.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.12
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• pp.2939-2945
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• 2014

This paper has analyzed the change of threshold voltage for oxide structure of symmetric and asymmetric double gate(DG) MOSFET. The asymmetric DGMOSFET can be fabricated with different top and bottom gate oxide thickness, while the symmetric DGMOSFET has the same top and bottom gate oxide thickness. Therefore optimum threshold voltage is considered for top and bottom gate oxide thickness of asymmetric DGMOSFET, compared with the threshold voltage of symmetric DGMOSFET. To obtain the threshold voltage, the analytical potential distribution is derived from Possion's equation, and Gaussian distribution function is used as doping profile. We investigate for bottom gate voltage, channel length and thickness, and doping concentration how top and bottom gate oxide thickness influences on threshold voltage using this threshold voltage model. As a result, threshold voltage is greatly changed for oxide thickness, and we know the changing trend greatly differs with bottom gate voltage, channel length and thickness, and doping concentration.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.05a
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• pp.755-758
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• 2014

This paper has analyzed the change of threshold voltage for oxide structure of symmetric and asymmetric double gate(DG) MOSFET. The asymmetric DGMOSFET can be fabricated with different top and bottom gate oxide thickness, while the symmetric DGMOSFET has the same top and bottom gate oxide thickness. Therefore optimum threshold voltage is considered for top and bottom gate oxide thickness of asymmetric DGMOSFET, compared with the threshold voltage of symmetric DGMOSFET. To obtain the threshold voltage, the analytical potential distribution is derived from Possion's equation, and Gaussian distribution function is used as doping profile. We investigate for bottom gate voltage, channel length and thickness, and doping concentration how top and bottom gate oxide thickness influences on threshold voltage using this threshold voltage model. As a result, threshold voltage is greatly changed for oxide thickness, and we know the changing trend very differs with bottom gate voltage, channel length and thickness, and doping concentration.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.3
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• pp.657-662
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• 2014

This paper has analyzed the subthreshold swings for top and bottom gate voltages of asymmetric double gate(DG) MOSFET. The asymmetric DGMOSFET is four terminal device to be able to separately bias for top and bottom gates. The subthreshold swing, therefore, has to be analyze not only for top gate voltage, but also for bottom gate voltage. In the pursuit of this purpose, Poisson equation has been solved to obtain the analytical solution of potential distribution with Gaussian function, and the subthreshold swing model has been presented. As a result to observe the subthreshold swings for the change of top and bottom gate voltage using this subthreshold swing model, we know the subthreshold swings are greatly changed for gate voltages. Especially we know the conduction path has been changed for top and bottom gate voltage and this is expected to greatly influence on subthreshold swings.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.704-707
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• 2013

This paper has analyzed the subthreshold swings for top and bottom gate voltages of asymmetric double gate(DG) MOSFET. The asymmetric DGMOSFET is four terminal device to be able to separately bias for top and bottom gates. The subthreshold swing, therefore, has to be analyze not only for top gate voltage, but also for bottom gate voltage. In the pursuit of this purpose, Poisson equation has been solved to obtain the analytical solution of potential distribution with Gaussian function, and the subthreshold swing model has been presented. As a result to observe the subthreshold swings for the change of top and bottom gate voltage using this subthreshold swing model, we know the subthreshold swings are greatly changed for gate voltages. Especially we know the conduction path has been changed for top and bottom gate voltage and this is expected to greatly influence on subthreshold swings.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.5
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• pp.992-997
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• 2016

This paper analyzes the deviation of tunneling current for the ratio of top and bottom gate oxide thickness of short channel asymmetric double gate(DG) MOSFET. The ratio of tunneling current for off current significantly increases if channel length reduces to 5 nm. This short channel effect occurs for asymmetric DGMOSFET having different top and bottom gate oxide structure. The ratio of tunneling current in off current with parameters of channel length and thickness, doping concentration, and top/bottom gate voltages is calculated in this study, and the influence of tunneling current to occur in short channel is investigated. The analytical potential distribution is obtained using Poisson equation and tunneling current using WKB(Wentzel-Kramers-Brillouin). As a result, tunneling current is greatly changed for the ratio of top and bottom gate oxide thickness in short channel asymmetric DGMOSFET, specially according to channel length, channel thickness, doping concentration, and top/bottom gate voltages.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.5
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• pp.315-318
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• 1999

We have proposed and fabricated the new bottom-gated polycrystalline silicon (poly-Si) thin film transistor (TFT) with a partial amorphous-Si region by employing the selective laser annealing. The channel layer of the proposed TFTs is composed of poly-Si region in the center and a-Si region in the edge. The TEM image shows that the local a-Si region is successfully fabricated by the effective cut out of the incident laser light in the upper a-Si layer. Our experimental results show that the ON/OFF current ratio is increased significantly by more than three orders in the new poly-Si TFT compared with conventional poly-Si TFT. The leakage current is decreased significantly due to the highly resistive a-Si re TFTs while the ON-series resistance of the local a-Si is reduced significantly due to the considerable inducement of electron carriers by the positive gate bias, so that the ON-current is not decreased much.

• Journal of IKEEE
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• v.24 no.1
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• pp.194-199
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• 2020

The threshold voltage roll-off for an asymmetric junctionless double gate MOSFET is analyzed according to the top and bottom gate oxide thicknesses. In the asymmetric structure, the top and bottom gate oxide thicknesses can be made differently, so that the top and bottom oxide thicknesses can be adjusted to reduce the leakage current that may occur in the top gate while keeping the threshold voltage roll-off constant. An analytical threshold voltage model is presented, and this model is in good agreement with the 2D simulation value. As a result, if the thickness of the bottom gate oxide film is decreased while maintaining a constant threshold voltage roll-off, the top gate oxide film thickness can be increased, and the leakage current that may occur in the top gate can be reduced. Especially, it is observed that the increase of the bottom gate oxide thickness does not affect the threshold voltage roll-off.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.2
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• pp.401-406
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• 2015

The change of subthreshold swing for channel length of asymmetric double gate(DG) MOSFET has been analyzed. The subthreshold swing is the important factor to determine digital chracteristics of transistor and is degraded with reduction of channel. The subthreshold swing for channel length of the DGMOSFET developed to solve this problem is investigated for channel thickness, oxide thickness, top and bottom gate voltage and doping concentration. Especially the subthreshold swing for asymmetric DGMOSFET to be able to be fabricated with different top and bottom gate structure is investigated in detail for bottom gate voltage and bottom oxide thickness. To obtain the analytical subthreshold swing, the analytical potential distribution is derived from Possion's equation, and Gaussian distribution function is used as doping profile. As a result, subthreshold swing is sensitively changed according to top and bottom gate voltage, channel doping concentration and channel dimension.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.4
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• pp.281-285
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• 2020

Oxide semiconductor devices have become increasingly important because of their high mobility and good uniformity. The channel length of oxide semiconductor thin film transistors (TFTs) also shrinks as the display resolution increases. It is well known that reducing the channel length of a TFT is detrimental to the current saturation because of drain-induced barrier lowering, as well as the movement of the pinch-off point. In an organic light-emitting diode (OLED), the lack of current saturation in the driving TFT creates a major problem in the control of OLED current. To obtain improved current saturation in short channels, we fabricated indium gallium zinc oxide (IGZO) TFTs with single gate and double gate structures, and evaluated the electrical characteristics of both devices. For the double gate structure, we connected the bottom gate electrode to the source electrode, so that the electric potential of the bottom gate was fixed to that of the source. We denote the double gate structure with the bottom gate fixed at the source potential as the BGFP (bottom gate with fixed potential) structure. For the BGFP TFT, the current saturation, as determined by the output characteristics, is better than that of the conventional single gate TFT. This is because the change in the source side potential barrier by the drain field has been suppressed.