• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.44 no.4
• /
• pp.483-489
• /
• 1995

To investigate the mechanism generated by irradiation in the insulator layer irradiated MIS (Metal - Insulator - Semiconductor) device, the various types of MIS capacitors depending on insulator thickness, insulator types and implanted impurities are fabricated on the P-type wafer. MIS capacitors exposed by 1Mrad Co$^{60}$ .gamma.-ray are measured for flat band voltage and charge density shifts pre- and post-irradiation. The measuring results of post-irradiation show the flat band voltage shifting toward negative direction and charge density increasing regardless of parameters. This results have a good agreement with calculated data by computer simulation. Si$_{3}$N$_{4}$ layers have a good radiation-hardness than SiO$_{2}$ layers compared to the results of post-irradiation. Also, radiation-induced negative trap is discovered in the implanted insulator layer. Using numerical analysis, four continuty equations (conduction-band electrons continuity equation, valence-band holes continuity equation, trapped electrons continuity equation, trapped holes continuity equation) are solved and charge distributions according to the distance and Si-Insulator interface states are investigated.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.11 no.1
• /
• pp.40-50
• /
• 2011

A two-dimensional (2D) analytical model for the potential distribution and threshold voltage of short-channel ion-implanted GaAs MESFETs operating in the sub-threshold regime has been presented. A double-integrable Gaussian-like function has been assumed as the doping distribution profile in the vertical direction of the channel. The Schottky gate has been assumed to be semi-transparent through which optical radiation is coupled into the device. The 2D potential distribution in the channel of the short-channel device has been obtained by solving the 2D Poisson's equation by using suitable boundary conditions. The effects of excess carrier generation due to the incident optical radiation in channel region have been included in the Poisson's equation to study the optical effects on the device. The potential function has been utilized to model the threshold voltage of the device under dark and illuminated conditions. The proposed model has been verified by comparing the theoretically predicted results with simulated data obtained by using the commercially available $ATLAS^{TM}$ 2D device simulator.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.47 no.10
• /
• pp.1-6
• /
• 2010

In this paper, RF Capacitance-Voltage(C-V) curve of short-channel MOSFET has been extracted from the room temperature to $225^{\circ}C$ using a RF method based on measured S-parameter data, and its high-temperature dependent characteristics are empirically modeled. It is observed that the voltage shift according to the variation of temperature in the weak inversion region of RF C-V curves is lower than the threshold voltage shift, but it is confirmed that this phenomenon is unexplainable with a long-channel theoretical C-V equation. The new empirical equation is developed for high-temperature dependent modeling of short-channel MOSFET C-V curves. The accuracy of this equation is demonstrated by observing good agreements between the modeled and measured C-V data in the wide range of temperature. It is also confirmed that the channel capacitance decreases with increasing temperature at high gate voltage.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.38 no.6
• /
• pp.431-440
• /
• 1989

This paper proposes a new PWM cycloconverter which can step up input voltage. With input reactors ac power supply acts as current source, and with output capacitors the balanced output voltage is build-up. The converter is modeled with fourth order state equation using dq transformation and the steady state characteristics are evaluated. It is shown that the proposed converter can generate the output voltage 2-5 times greater than input voltage. The output voltage and input current have sinusoidal and smooth waveforms and the converter is capable of voltage build-up. The characteristics of the proposed converter is verified simulation and experiment.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.13 no.6
• /
• pp.539-545
• /
• 2013

In this paper, a behavioral current-voltage model with intermediate states is proposed for analog applications of unipolar resistive memories, where intermediate resistance values between SET and RESET state are used to store analog data. In this model, SET and RESET behaviors are unified into one equation by the blending function and the percentage volume fraction of each region is modeled by the Johnson-Mehl-Avrami (JMA) equation that can describe the time-dependent phase transformation of unipolar memory. The proposed model is verified by the measured results of $TiO_2$ unipolar memory and tested by the SPECTRE circuit simulation with CMOS read and write circuits for unipolar resistive memories. With the proposed model, we also show that the behavioral model that combines the blending equation and JMA kinetics can universally describe not only unipolar memories but also bipolar ones. This universal behavioral model can be useful in practical applications, where various kinds of both unipolar and bipolar memories are being intensively studied, regardless of polarity of resistive memories.

• Journal of information and communication convergence engineering
• /
• v.9 no.6
• /
• pp.733-737
• /
• 2011

This paper has studied subthreshold characteristics for double gate(DG) MOSFET using Gaussian function in solving Poisson's equation. Typical two dimensional analytical transport models have been presented for symmetrical Double Gate MOSFETs (DGMOSFETs). Subthreshold swing and threshold voltage are very important factors for digital devices because of determination of ON and OFF. In general, subthreshold swings have to be under 100mV/dec, and threshold voltage roll-off small in short channel devices. These models are used to obtain the change of subthreshold swings and threshold voltage for DGMOSFET according to channel doping profiles. Also subthreshold swings and threshold voltages have been analyzed for device parameters such as channel length, channel thickness and channel doping profiles.

• Proceedings of the KIEE Conference
• /
• 1991.11a
• /
• pp.35-38
• /
• 1991

Recent, problems on the voltage-instability have been paid attention in power system and methods to find the limit of voltage-stability, concerned with these problems, were developed. However, these methods are short of precision on the limit of voltage-instability. Here, using the second-order load flow, constraint equation(d Pi/d Vi=0) and its patial differentiations are precisely formulated. Also, since the taylor series expansion of power flow equations terminates at the second-order terms, partial differentiations of constraint equation, that is Hessian, are constant. Then, Hessian matrix are calculated once during iteration process.

• ETRI Journal
• /
• v.32 no.1
• /
• pp.68-72
• /
• 2010

The coupling between the transverse and longitudinal components of the channel electron motion in NMOS devices leads to a reduction in the barrier height. Therefore, this study theoretically investigates the effects of the in-plane velocity of channel electrons on the capacitance-voltage characteristics of nano NMOS devices under inversion bias. Numerical calculation via a self-consistent solution to the coupled Schrodinger equation and Poisson equation is used in the investigation. The results demonstrate that such a coupling largely affects capacitance-voltage characteristic when the in-plane velocity of channel electrons is high. The ballistic transport ensures a high in-plane momentum. It suggests that such a coupling should be considered in the quantum capacitance-voltage modeling in ballistic transport devices.

• Proceedings of the KIEE Conference
• /
• 2001.07b
• /
• pp.745-747
• /
• 2001

This paper deals with the dynamic characteristics of flat core LOA. The LOA system was represented by the voltage equation of coil and the mechanical equation of motion. Also, driving system was simply composed voltage source inverter and generates square-wave. It is measured that dynamic characteristic vary as square-wave.

• Journal of Power Electronics
• /
• v.7 no.1
• /
• pp.13-20
• /
• 2007

LLC resonant converters display many advantages over the conventional LC series resonant converter such as narrow frequency variation over wide range of load and input variation and zero voltage switching even under no load conditions. This paper presents analysis and design consideration for the half bridge LLC resonant converter. Using the fundamental approximation, the gain equation is obtained, where the leakage inductance in the transformer secondary side is also considered. Based on the gain equation, the practical design procedure is investigated to optimize the resonant network for a given input/output specifications. The design procedure is verified through an experimental prototype of the 115W half-bridge LLC resonant converter.