• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.193-196
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• 1987

We reported that hot electron phenomena in submicron nMOSFET by Monte Carlo method. In order to predict the influence of the hot electron effects on the device reliability, either simple analytical model or a complete two dimensional numerical simulation has been adopted. Results of numerical simulation, based on the static mobility model, may be inaccurate when gate length of MOSFET is scaled down to less than 1um. Most of device simulation packages utilize the static nobility model. Monte Carlo method based on stochastic analysis of carrier movement may be a powerful tool to characterize hot electrons. In this work, energy and velocity distribution of carriers were obtained to predict the relative degree of short channel effects for different device parameters. Our analysis shows a few interesting results when $V_{ds}$ is 5 volt, average electron energy does not increase with gate bias as evidenced by substrate current.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.1
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• pp.91-105
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• 2016

Carbon Nanotube Field-Effect Transistors (CNTFETs) have been studied as candidates for post Si CMOS owing to the better electrostatic control and high mobility. To enhance the immunity against short - channel effects (SCEs), the novel channel and gate engineered architectures have been proposed to improve CNTFETs performance. This work presents a comprehensive study of the influence of channel and gate engineering on the CNTFET switching, high frequency and circuit level performance of carbon nanotube field-effect transistors (CNTFETs). At device level, the effects of channel and gate engineering on the switching and high frequency characteristics for CNTFET have been theoretically investigated by using a quantum kinetic model. This model is based on two-dimensional non-equilibrium Green's functions (NEGF) solved self - consistently with Poisson's equations. It is revealed that hetero - material - gate and lightly doped drain and source CNTFET (HMG - LDDS - CNTFET) structure can significantly reduce leakage current, enhance control ability of the gate on channel, improve the switching speed, and is more suitable for use in low power, high frequency circuits. At circuit level, using the HSPICE with look - up table(LUT) based Verilog - A models, the impact of the channel and gate engineering on basic digital circuits (inverter, static random access memory cell) have been investigated systematically. The performance parameters of circuits have been calculated and the optimum metal gate workfunction combinations of ${\Phi}_{M1}/{\Phi}_{M2}$ have been concluded in terms of power consumption, average delay, stability, energy consumption and power - delay product (PDP). In addition, we discuss and compare the CNTFET-based circuit designs of various logic gates, including ternary and binary logic. Simulation results indicate that LDDS - HMG - CNTFET circuits with ternary logic gate design have significantly better performance in comparison with other structures.

• The Korean Journal of Pharmacology
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• v.27 no.2
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• pp.99-108
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• 1991

The effect of racemic Ketamine HCl was observed on excitable membranes of sciatic nerve fibres and toe muscles from frog. Ketamine significantly depressed the amplitude of the action potential, maximum rate of rise and that of fall of action potentials of sciatic nerve by dose-dependent and time-course manner, and also it produced the inhibition of $K^+-contracture$ in toe muscle. We used two different ways of sucrose gap method to to obtain the better results from sciatic nerve. We observed and compared the effect of ketamine on sciatic nerve with naloxone, 4-AP (4-aminopyridine) and TEA (Tetraethylammonium). Naloxone significantly but not totally blocked the effect of ketamine both on nerve and on skeletal muscle. 4-AP or TEA by itself had a significant depressant effect on the action potentials on nerve by central perfusion (extracellular perfusion), but both of these drugs did not much affect the action of Ketamine on nerve. The reversibility of effect of Ketamine (10 mM) was observed both on nerve and on skeletal muscles when exposed to drug for short duration. The effects of racemic ketamine described may provide to support that one of the mechanisms of the action of Ketamine on nerve and on muscles of frog might be related to non-specifically effect on receptors within the ion channels $(K^+-channel,\;Na^+-channel\;or\;slow\;Ca^{++}\;channel)$ at higher dose which produces anesthetic effect and also it interacts specifically with one of the opioid receptors or subtype of these receptors which is sensitive to Naloxone at lower dose which produces analgesia.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.35T no.2
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• pp.6-12
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• 1998

Thin film SOI(Silicon-on-insulator) device offer unique advantages such as reduction in short channel effects, improvement of subthreshold slope, higher mobility, latch-up free nature, and so on. But these devices exhibit floating-body effet such as current kink which inhibits the proper device operation. In this paper, the SOI NMOSFET with a T-type gate structure is proposed to solve the above problem. To simulate the proposed device with TSUPREM-4, the part of gate oxide was considered to be 30nm thicker than the normal gate oxide. The I-V characteristics were simulated with 2D MEDICI. Since part of gate oxide has different oxide thickness, the gate electric field strength is not same throughout the gate and hence the impact ionization current is reduced. The current kink effect will be reduced as the impact ionization current drop. The reduction of current kink effect for the proposed device structure were shown using MEDICI by the simulation of impact ionization current, I-V characteristics, and hole current distribution.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2324-2332
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• 2017

This paper presents the electrical performances of novel AlGaSb/InGaAs heterojunction-based vertical-tunneling field-effect transistor (VTFET). The device performance was investigated in views of the on-state current ($I_{on}$), drain-induced barrier thinning (DIBT), and subthreshold swing (SS) as the gate length ($L_G$) was scaled down. The proposed TFET with a $L_G$ of 5 nm operated with an $I_{on}$ of $1.3mA/{\mu}m$, a DIBT of 40 mV/V, and an SS of 23 mV/dec at a drain voltage ($V_{DS}$) of 0.23 V. The proposed TFET provided approximately 25 times lower DIBT and 12 times smaller SS compared with the conventional $L_G$ of 5 nm TFET. The AlGaSb/InGaAs VTFET showed extremely high scalability and strong immunity against short-channel effects.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.7
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• pp.1537-1542
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• 2011

In this paper, the subthreshold characteristics have been analyzed for various oxide thickness of double gate MOSFET(DGMOSFET) using Poisson's equation with nonuniform doping distribution. The DGMOSFET is extensively been studying since it can shrink the short channel effects(SCEs) in nano device. The degradation of subthreshold swing(SS) known as SCEs has been presented using analytical for, of Poisson's equation with nonuniform doping distribution for DGMOSFET. The SS have been analyzed for, change of gate oxide thickness to be the most important structural parameters of DGMOSFET. To verify this potential and transport models of thus analytical Poisson's equation, the results have been compared with those of the numerical Poisson's equation, and subthreshold swing has been analyzed using this models for DGMOSFET.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.9
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• pp.2000-2006
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• 2011

In this paper, the drain induced barrier lowering(DIBL) for doping distribution in the channel has been analyzed for double gate MOSFET(DGMOSFET). The DGMOSFET is extensively been studing because of adventages to be able to reduce the short channel effects(SCEs) to occur in convensional MOSFET. DIBL is SCE known as reduction of threshold voltage due to variation of energy band by high drain voltage. This DIBL has been analyzed for structural parameter and variation of channel doping profile for DGMOSFET. For this object, The analytical model of Poisson equation has been derived from Gaussian doping distribution for DGMOSFET. To verify potential and DIBL models based on this analytical Poisson's equation, the results have been compared with those of the numerical Poisson's equation, and DIBL for DGMOSFET has been investigated using this models.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.6
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• pp.688-697
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• 2008

In this paper, an analysis method for indoor optical wireless channel properties based on photon model is presented for characterization of communication environment. In contrast to radio waves, optical waves have very short wave-lengths and very high frequencies, so that material properties become important. Channel models including diffuse reflections and absorption effects due to material surface textures make conventional electromagnetic wave analysis methods based on ray tracing consume enormous time. To overcome these problems, an analysis method using photon model is presented that approximates light intensity by a density of photons. The photon model ensures that simulation time is within a predictable limit.

• JSTS:Journal of Semiconductor Technology and Science
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• v.7 no.2
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• pp.110-119
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• 2007

A new two-dimensional analytical model for dual-material double-gate fully-depleted SOI MOSFET with Pearson-IV type Doping Distribution is presented. An investigation of electrical MOSFET parameters i.e. drain current, transconductance, channel resistance and device capacitance in DM DG FD SOI MOSFET is carried out with Pearson-IV type doping distribution as it is essential to establish proper profiles to get the optimum performance of the device. These parameters are categorically derived keeping view of potential at the center (${\phi}_c$) of the double gate SOI MOSFET as it is more sensitive than the potential at the surface (${\phi}_s$). The proposed structure is such that the work function of the gate material (both sides) near the source is higher than the one near the drain. This work demonstrates the benefits of high performance proposed structure over their single material gate counterparts. The results predicted by the model are compared with those obtained by 2D device simulator ATLAS to verify the accuracy of the proposed model.

• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.3
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• pp.195-203
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• 2005

Recently, a novel multi-bit nonvolatile memory based on double gate (DG) MOSFET is proposed to overcome the short channel effects and to increase the memory density. We need more complex voltage schemes for DG MOSFET devices. In view of peripheral circuits driving memory cells, one should consider various voltage sources used for several operations. It is one of the key issues to minimize the number of voltage sources. This criterion needs more caution in considering a DG nonvolatile memory cell that inevitably requires more number of events for voltage sources. Therefore figuring out the permissible range of operating bias should be preceded for reliable operation. We found that reliable operation largely depends on the depletion conditions of the silicon channel according to charge amount stored in the floating gates and the negative control gate voltages applied for read operation. We used Silvaco Atlas, a 2D numerical simulation tool as the device simulator.