• 한국전기전자재료학회논문지
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• 제11권12호
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• pp.1122-1127
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• 1998

Group II-AF_2$films such as $CaF_2$, $SrF_2$, and $BaF_2$ have been commonly used many practical applications such as silicon on insulatro(SOI), three-dimensional integrated circuits, buffer layers, and gate dielectrics in filed effect transistor. This paper presents electrical and structural properties of fluoride films as a gate dielectric layer. Conventional gate dielectric materials of TFTs like oxide group exhibited problems on high interface trap charge density($D_it$), and interface state incorporation with O-H bond created by mobile hydrogen and oxygen atoms. To overcome such problems in conventional gate insulators, we have investigated $CaF_2$ films on Si substrates. Fluoride films were deposited using a high vacuum evaporation method on the Si and glass substrate. $CaF_2$ films were preferentially grown in (200) plane direction at room temperature. We were able to achieve a minimum lattice mismatch of 0.74% between Si and $CaF_2$ films. Average roughness of $CaF_2$ films was decreased from 54.1 ${\AA}$ to 8.40 ${\AA}$ as temperature increased form RT and $300^{\circ}C$. Well fabricated MIM device showed breakdown electric field of 1.27 MV/cm and low leakage current of $10^{-10}$ A/$cm^2$. Interface trap charge density between $CaF_2$ film and Si substrate was as low as $1.8{\times}10^{11}cm^{-2}eV^{-1}$.

• 한국재료학회지
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• 제31권10호
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• pp.539-545
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• 2021

The effect of Sm₂O₃ doping on the microstructure and electrical properties of the ZPCCA-based varistors is comprehensively investigated. The increase of doping content of Sm₂O₃ results in better densification (from 5.70 to 5.82 g/cm³) and smaller mean grain size (from 7.8 to 4.1 ㎛). The breakdown electric field increases significantly from 2568 to 6800 V/cm as the doping content of Sm₂O₃ increases. The doping of Sm₂O₃ remarkably improves the nonlinear properties (increasing from 23.9 to 91 in the nonlinear coefficient and decreasing from 35.2 to 0.2 µA/cm² in the leakage current density). Meanwhile, the doping of Sm₂O₃ reduces the donor concentration (the range of 2.73 × 10¹⁸ to 1.18 × 10¹⁸ cm^-3) of bulk grain and increases the barrier height (the range of 1.10 to 1.49 eV) at the grain boundary. The density of the interface states decreases in the range of of 5.31 × 10¹² to 4.08 × 10¹² cm^-2 with the increase of doping content of Sm₂O₃. The dielectric constant decreases from 1594.8 to 507.5 with the increase of doping content of Sm₂O₃.

• 한국재료학회지
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• 제34권2호
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• pp.111-115
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• 2024

Silicon carbide (SiC) has emerged as a promising material for next-generation power semiconductor materials, due to its high thermal conductivity and high critical electric field (~3 MV/cm) with a wide bandgap of 3.3 eV. This permits SiC devices to operate at lower on-resistance and higher breakdown voltage. However, to improve device performance, advanced research is still needed to reduce point defects in the SiC epitaxial layer. This work investigated the electrical characteristics and defect properties using DLTS analysis. Four deep level defects generated by the implantation process and during epitaxial layer growth were detected. Trap parameters such as energy level, capture-cross section, trap density were obtained from an Arrhenius plot. To investigate the impact of defects on the device, a 2D TCAD simulation was conducted using the same device structure, and the extracted defect parameters were added to confirm electrical characteristics. The degradation of device performance such as an increase in on-resistance by adding trap parameters was confirmed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.55-55
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• 2009

Silicon Carbide (SiC) is a material with a wide bandgap (3.26eV), a high critical electric field (~2.3MV/cm), a and a high bulk electron mobility (${\sim}900cm^2/Vs$). These electronic properties allow high breakdown voltage, high frequency, and high temperature operation compared to Silicon devices. Although various SiC DMOSFET structures have been reported so far for optimizing performances. the effect of channel dimension on the switching performance of SiC DMOSFETs has not been extensively examined. In this paper, we report the effect of the interface states ($Q_s$) on the transient characteristics of SiC DMOSFETs. The key design parameters for SiC DMOSFETs have been optimized and a physics-based two-dimensional (2-D) mixed device and circuit simulator by Silvaco Inc. has been used to understand the relationship with the switching characteristics. To investigate transient characteristic of the device, mixed-mode simulation has been performed, where the solution of the basic transport equations for the 2-D device structures is directly embedded into the solution procedure for the circuit equations. The result is a low-loss transient characteristic at low $Q_s$. Based on the simulation results, the DMOSFETs exhibit the turn-on time of 10ns at short channel and 9ns at without the interface charges. By reducing $SiO_2/SiC$ interface charge, power losses and switching time also decreases, primarily due to the lowered channel mobilities. As high density interface states can result in increased carrier trapping, or recombination centers or scattering sites. Therefore, the quality of $SiO_2/SiC$ interfaces is important for both static and transient properties of SiC MOSFET devices.

• 한국전기전자재료학회논문지
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• 제30권9호
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• pp.535-540
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• 2017

The changes in the electrical characteristics of CMOS ICs due to coupling with a narrow-band electromagnetic wave were analyzed in this study. A magnetron (3 kW, 2.45 GHz) was used as the narrow-band electromagnetic source. The DUT was a CMOS logic IC and the gate output was in the ON state. The malfunction of the ICs was confirmed by monitoring the variation of the gate output voltage. It was observed that malfunction (self-reset) and destruction of the ICs occurred as the electric field increased. To confirm the variation of electrical characteristics of the ICs due to the narrow-band electromagnetic wave, the pin-to-pin resistances (Vcc-GND, Vcc-Input1, Input1-GND) and input capacitance of the ICs were measured. The pin-to-pin resistances and input capacitance of the ICs before exposure to the narrow-band electromagnetic waves were $8.57M{\Omega}$ (Vcc-GND), $14.14M{\Omega}$ (Vcc-Input1), $18.24M{\Omega}$ (Input1-GND), and 5 pF (input capacitance). The ICs exposed to narrow-band electromagnetic waves showed mostly similar values, but some error values were observed, such as $2.5{\Omega}$, $50M{\Omega}$, or 71 pF. This is attributed to the breakdown of the pn junction when latch-up in CMOS occurred. In order to confirm surface damage of the ICs, the epoxy molding compound was removed and then studied with an optical microscope. In general, there was severe deterioration in the PCB trace. It is considered that the current density of the trace increased due to the electromagnetic wave, resulting in the deterioration of the trace. The results of this study can be applied as basic data for the analysis of the effect of narrow-band high-power electromagnetic waves on ICs.

• 대한공간정보학회지
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• 제23권3호
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• pp.69-75
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• 2015

안전한 도로주행을 위하여 설치된 도로시설물들은 주야간에도 식별할 수 있도록 제작되었으나, 기상악화 시 제 기능을 발휘하지 못하고 있다. 최근에는 원거리에서도 명확하게 인식할 수 있는 전기전자기술로 제작하고 있으나, 이들은 고장이 빈번하여 수시로 교체해야 하므로 교통정온화와 유지관리에 많은 문제점들이 나타나고 있다. 본 연구는 이러한 문제를 해결하기 위하여 교통사고가 빈번한 지역에 반영구적으로 이용할 수 있는 LED 표시등을 설치하고, 이를 시스템과 연계하여 유지 관리할 수 있는 모니터링시스템을 개발하였다. 이를 위하여 시스템은 윈도우 운영체계 기반으로 하였고, 무선통신망과 연결하여 P.C에서 운용될 수 있도록 개발하였다. 그 결과 현장에 설치된 LED 표시등의 배터리 상태정보를 실시간으로 분석을 할 수 있었고, 그 수명주기를 예측함으로서 효율적으로 관리할 수 있었다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권8호
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• pp.340-346
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• 2002

Capacitor material utilized in the downsizing passive devices and integration of passive devices requires the physical and electrical properties at given area such as capacitor thickness reduction, relative dielectric constant increase, low leakage current and thermal stability. common capacitor materials, $Al_2O_3$, $SiO_2$, $Si_3N_4$, $SiO_2$/$Si_3N_4$, TaN and et al., used until recently have reached their physical limits in their application to integration of passive devices. $Ta_2O_{5}$ is known to be a good alternative to the existing materials for the capacitor application because of its high dielectric constant (25~35), low leakage current and high breakdown strength. Despite the numerous investigations of $Ta_2O_{5}$ material, there have little been established the clear understanding of the annealing effect on capacitance characteristic and conduction mechanism. This study presents the dielectric properties $Ta_2O_{5}$ MIM capacitor structure Processed by $O_2$ RTA oxidation. X-ray diffraction patterns showed the existence of amorphous phase in $600^{\circ}C$ annealing under the $O_2$ RTA and the formation of preferentially oriented-$Ta_2O_{5}$ in 650, $700^{\circ}C$ annealing and the AES depth profile showed $O_2$ RTA oxidation effect gives rise to the $O_2$ deficientd into the new layer. The leakage current density respectively, at 3~1l$\times$$10_{-2}$(kV/cm) were $10_{-3}$~$10_{-6}$(A/$\textrm{cm}^2$). In addition, behavior is stable irrespective of applied electric field. the frequency vs capacitance characteristic enhanced stability more then $Ta_2O_{5}$ thin films obtained by $O_2$ reactive sputtering. The capacitance vs voltage measurement that, Vfb(flat-band voltage) was increase dependance on the $O_2$ RTA oxidation temperature.

• Journal of the Optical Society of Korea
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• 제13권1호
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• pp.8-14
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• 2009

In a laser-plasma wakefield accelerator, the ponderomotive force of an ultrashort high intensity laser pulse excites a longitudinal wave or plasma bubble in a way similar to the excitation of a wake wave behind a boat as it propagates on the water surface. Electric fields inside the plasma bubble can be several orders of magnitude higher than those available in conventional RF-based particle accelerator facilities which are limited by material breakdown. Therefore, if an electron bunch is properly phase-locked with the bubble's acceleration field, it can gain relativistic energies within an extremely short distance. Here, in the bubble regime we show the generation of stable and reproducible sub GeV, and GeV-class electron beams. Supported by three-dimensional particle-in-cell simulations, our experimental results show the highest acceleration gradients produced so far. Simulations suggested that the plasma bubble elongation should be minimized in order to achieve higher electron beam energies.

• 한국인터넷방송통신학회논문지
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• 제21권6호
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• pp.25-32
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• 2021

본 논문에서는 비교적 구현이 쉽고, 최종 결합 포트의 전송 선로 길이를 짧게 구현할 수 있는 모드 변환기에 대해 제안하고, 8-way 공간 결합기에 적용하여 제작 및 시험을 하였다. 제안하는 모드 변환기는 그라운드와 연결되어 있는 Doorknob 형태의 원형 디스크에서 변환된 신호를 원형 도파관 내에서 개방을 시켜 TM₀₁ 모드로 변환이 이루어진다. 8-way 도파관 공간 결합기는 H-평면에서 입력된 8개의 신호를 중심의 원형 도파관에서 결합이 이루어지고, 최종 결합 모드는 TM₀₁이 되도록 설계를 하였다. 시험 결과는 삽입손실 0.4dB 이하, 결합효율 95%이상의 우수한 성능을 확인하였다. 또한 전계 분석을 통해 새로운 모드 변환 구조의 절연 파괴 전압 및 방전 임계전력을 계산하여 고출력에 적합함을 확인하였다. 본 연구를 통해 확인된 결과는 향후 고출력 고효율 SSPA에 다방면으로 적용이 가능할 것으로 기대된다.

• 한국결정성장학회지
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• 제32권4호
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• pp.121-127
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• 2022

초광역대 반도체인 β-Ga₂O₃은 고전력 반도체 소재에 대한 유망한 응용으로 인해 큰 주목을 받고 있다. 5가지 다른 다형 중 가장 안정적인 상인 β-Ga₂O₃는 4.9 eV의 넓은 밴드갭과 8 MV/cm의 높은 항복 전계를 갖는다. 또한, 이는 용융 소스로부터 성장될 수 있어 전력반도체용 SiC, GaN 및 다이아몬드와 같은 다른 와이드 밴드갭 반도체보다 더 높은 성장률과 더 낮은 제조 비용으로 성장이 가능하다. 이 연구에서 β-Ga₂O₃ 단결정 성장은 EFG(edge-defined film-fed growth) 방법에 의해 성장되었다. 성장 방향과 주면을 각각 β-Ga₂O₃ 결정의 [010] 방향과 (100)면으로 성장하였다. Raman 분석의 스펙트럼으로 β-Ga₂O₃ 잉곳의 결정상과 불순물을 확인하였고, 고해상도 X선 회절(HRXRD)을 이용하여 결정 품질과 결정 방향을 분석하였다. 또한 EFG 방법으로 성장한 β-Ga₂O₃ 리본형태의 잉곳을 각 위치별로 결정 품질과 다양한 특성을 체계적으로 분석하였다.