• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.907-910
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• 1999

본 논문에서는 고 농도로 불순물이 주입된 영역에서 전자 및 정공 농도를 정교하게 구현하기 위해 Fermi-Dirac 분포함수를 고려한 포아송 방정식의 이산화 방법을 제안하였다. Fermi-Dirac 분포를 근사시키기 위해서 Least-Squares 및 점근선 근사법을 사용하였으며 Galerkin 방법을 근간으로 한 유한 요소법을 이용하여 포아송 방정식을 이산화하였다. 구현한 모델을 검증하기 위해 전력 BJT 시료를 제작하여 자체 개발된 소자 시뮬레이터인 BANDIS를 이용하여 모의 실험을 수행한 결과, 상업용 2차원 소자 시뮬레이터인 MEDICI에 비해 최대 4%이내의 상대 오차를 보였다.

• Proceedings of the IEEK Conference
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• 2001.06b
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• pp.157-160
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• 2001

소자 내부의 전위와 전자 및 정공 의사 페르미 준위에 따른 반송자의 정확한 농도를 얻기 위해 Fermi-Dirac통계를 구현하는 방법을 제시하였다. 또한 Fermi-Dirac통계를 고려하여 반도체 방정식을 이산화하는 방법을 제안한다. 제안된 방법을 검증하기 위해 전력 바이폴라 접합 트랜지스터를 제작하였으며 모의 실험 결과 컬렉터-에미터 전압 대 컬렉터 전류는 현재 업계에서 상용화된 소자의 실측치와 비교하여 최대 15%이내의 상대오차를 보였다.

• The Journal of the Korea Contents Association
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• v.9 no.11
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• pp.309-315
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• 2009

Image reconstruction of Inverse Fourier Transform after Frequency Domain Data is filtered applies to Image signal acquired from MR. There are various kinds of image processing techniques; image preprocessing, image reconstruction, image compression, image restoration image mixture, noise and artifact elimination, and image quality improvement. In this paper, optimum filter applicable to diagnosis in clinic by comparing and analyzing the characteristics of the filter will be explained. Fermi-Dirac filter will improve the image quality better than the previous MR image.

• Journal of IKEEE
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• v.6 no.2 s.11
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• pp.119-127
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• 2002

An algorithm for analyzing the characteristics of the power BJT using numerical analysis method is proposed. The Fermi-Dirac statistics is used to calculate the carrier concentration in highly doped region. Philips Unified mobility model, SRH model and Auger model is used to calculate the recombination current of base region. To verify the accuracy of the proposed method, the collector current of BANDIS is compared with the measured data in the condition of the base current increased from $1.0[{\mu}A]\;to\;3.5[{\mu}A]$. The collector current of BANDIS show a maximum relative error within 8.9% compared with the measured data.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.291.1-291.1
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• 2016

Graphene by one of the two-dimensional (2D) materials has been focused on electronic applications due to its ultrahigh carrier mobility, outstanding thermal conductivity and superior optical properties. Although graphene has many remarkable properties, graphene devices have low on/off current ratio due to its zero bandgap. Despite considerable efforts to open its bandgap, it's hard to obtain appropriate improvements. To solve this problem, heterojunction barristor was proposed based on graphene. Mostly, this heterojunction barristor is made by transition metal dichalcogenides (TMDs), such as molybdenum disulfide ($MoS_2$) and tungsten diselenide ($WSe_2$), which have extremely thickness scalability of TMDs. The heterojunction barristor has the advantage of controlling graphene's Fermi level by applying gate bias, resulting in barrier height modulation between graphene interface and semiconductor. However, charged impurities between graphene and $SiO_2$ cause unexpected p-type doping of graphene. The graphene's Fermi level modulation is expected to be reduced due to this p-doping effect. Charged impurities make carrier mobility in graphene reduced and modulation of graphene's Fermi level limited. In this paper, we investigated theoretically and experimentally a relevance between graphene's Fermi level and p-type doping. Theoretically, when Fermi level is placed at the Dirac point, larger graphene's Fermi level modulation was calculated between -20 V and +20 V of $V_{GS}$. On the contrary, graphene's Fermi level modulation was 0.11 eV when Fermi level is far away from the Dirac point in the same range. Then, we produced two types heterojunction barristors which made by p-type doped graphene and graphene treated 2.4% APTES, respectively. On/off current ratio (32-fold) of graphene treated 2.4% APTES was improved in comparison with p-type doped graphene.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.2
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• pp.14-26
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• 2002

A new model for degenerate semiconductor quantum well devices was developed. In this model, the multi-subband Boltzmann transport equation was formulated by applying the Pauli exclusion principle and coupled to the Schrodinger and Poisson equations. For the solution of the resulted nonlinear system, the finite difference method and the Newton-Raphson method was used and carrier energy distribution function was obtained for each subband. The model was applied to a Si MOSFET inversion layer. The results of the simulation showed the changes of the distribution function from Boltzmann like to Fermi-Dirac like depending on the electron density in the quantum well, which presents the appropriateness of this modeling, the effectiveness of the solution method, and the importance of the Pauli -exclusion principle according to the reduced size of semiconductor devices.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.8
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• pp.913-919
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• 2008

A new design and its experimental results of a microstrip-fed ultra-wideband tapered slot antenna(TSA) for millimeter-wave systems are presented. By utilizing the ultra-wideband microstrip-to-CPS transition(balun), ultra-wideband characteristics of the inherent TSA are retrieved. Also, the design procedure of the TSA is simplified by performing simple impedance matching between balun and antenna. The proposed TSA is shaped by using the Fermi-Dirac tapering function and corrugated at the outer edge. The implemented antenna demonstrates ultra-wideband performance for frequency ranges from 23 to over 58 GHz with the relatively high and flat antenna gain of 12 to 14 dBi and low sidelobe levels. In addition, a 4-element linear antenna array for phased-array systems and mm-wave sensor applications is also presented.

• Laser Solutions
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• v.11 no.4
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• pp.13-20
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• 2008

The damage threshold measurement of gold films is carried out with ultrashort-pulse laser. An enhanced two temperature model is developed to encounter the limitation of linear modeling during ultrashort pulse laser ablation. In which the electron heat capacity is calculated using a quantum mechanical approach based on a Fermi-Dirac distribution, temperature-dependent electron thermal conductivity valid beyond the Fermi temperature is adopted, and reflectivity and absorption coefficient are estimated by applying a temperature-dependent electron relaxation time. The predicted damage threshold using the proposed enhanced modelclosely agreed with experimental results, demonstrating the importance of considering transient thermal and optical properties in the modeling of ultrashort pulse laser ablation.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.7
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• pp.38-46
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• 1993

Based on the close correlation between the optoelectronic and electrical characteristics of laser diodes, this paper is to present an exact model for electrical characteristics of laser diodes with bulk active layers so that the optoelectronic characteristics may be estimated from the electrical Characteristics. Among the considered models, the most exact model is shown to be one which uses the Fermi-Dirac integral and the bimolecular recombination and takes into account the energy-gap shrinkage with the injected carrier density.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.170.1-170.1
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• 2016

$Bi_2Te_3$ has long been studied for its excellent thermoelectric characteristics. Recently, this material has been known as a topological insulator (TI). The surface states within the bulk band gap of a TI, which are protected by the time reversal symmetry, contribute to the conduction at the surface, while the bulk is in insulating state. In contrast to the bulk defects tuning the chemical potential to the Dirac energy, the native defects near the surface are expected not to change the shape of the Fermi surface and the related spin structure. Using scanning tunneling microscopy (STM), we have systematically characterized surface or near surface defects in p- and n- doped $Bi_2Te_3$, and identified their structure by first principles calculations. In addition, bias-polarity dependences of STM images revealed the electron donor/acceptor nature of each defect. A detailed theoretical study of the surface states near the Dirac energy reveals the robustness of the Dirac point, which verifies the effectiveness of the disturbance on the backscattering from various kinds of defects.