• Korean Journal of Optics and Photonics
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• v.23 no.1
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• pp.6-11
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• 2012

A bidirectional TDM-PON link to support 2.5 Gb/s upstream signals of 256 ONUs was considered for an extended transmission distance of 50 km. The power budget of the link was 58 dB for the upstream signal and a SOA was applied as a link extender which had a 25 dB gain. Receiver sensitivity of the upstream signal was -25 dBm for -30 dBm input power to the SOA. When the input power was -10 dBm, pulse overshooting caused by gain transient of the SOA was maximum at 45% and the signal performance degradation gave a power penalty of 1.55 dB for $10^{-12}$ BER. However the penalties diminished rapidly and became negligible as the input power went below -15 dBm. So this input power dynamic range of up to -15 dBm means that it is not positively necessary to use gain control methods for the next generation TDM-PON systems.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.3
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• pp.201-206
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• 2019

This report constitutes the first demonstration in Korea of single-crystal lateral gallium oxide ($Ga_2O_3$) as a metal-oxide-semiconductor field-effect-transistor (MOSFET), with a breakdown voltage in excess of 480 V. A Si-doped channel layer was grown on a Fe-doped semi-insulating ${\beta}-Ga_2O_3$ (010) substrate by molecular beam epitaxy. The single-crystal substrate was grown by the edge-defined film-fed growth method and wafered to a size of $10{\times}15mm^2$. Although we fabricated several types of power devices using the same process, we only report the characterization of a finger-type MOSFET with a gate length ($L_g$) of $2{\mu}m$ and a gate-drain spacing ($L_{gd}$) of $5{\mu}m$. The MOSFET showed a favorable drain current modulation according to the gate voltage swing. A complete drain current pinch-off feature was also obtained for $V_{gs}<-6V$, and the three-terminal off-state breakdown voltage was over 482 V in a $L_{gd}=5{\mu}m$ device measured in Fluorinert ambient at $V_{gs}=-10V$. A low drain leakage current of 4.7 nA at the off-state led to a high on/off drain current ratio of approximately $5.3{\times}10^5$. These device characteristics indicate the promising potential of $Ga_2O_3$-based electrical devices for next-generation high-power device applications, such as electrical autonomous vehicles, railroads, photovoltaics, renewable energy, and industry.

• Korean Journal of Materials Research
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• v.24 no.8
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• pp.434-442
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• 2014

Serious environmental problems have been caused by the greenhouse effect due to carbon dioxide($CO_2$) or nitrogen oxides($NO_x$) generated by the use of fossil fuels, including oil and liquefied natural gas. Many countries, including our own, the United States, those of the European Union and other developed countries around the world; have shown growing interest in clean energy, and have been concentrating on the development of new energy-saving materials and devices. Typical non-fossil-fuel sources include solar cells, wind power, tidal power, nuclear power, and fuel cells. In particular, organic solar cells(OSCs) have relatively low power-conversion efficiency(PCE) in comparison with inorganic(silicon) based solar cells, compound semiconductor solar cells and the CIGS [$Cu(In_{1-x}Ga_x)Se_2$] thin film solar cells. Recently, organic cell efficiencies greater than 10 % have been obtained by means of the development of new organic semiconducting materials, which feature improvements in crystalline properties, as well as in the quantum-dot nano-structure of the active layers. In this paper, a brief overview of solar cells in general is presented. In particular, the current development status of the next-generation OSCs including their operation principle, device-manufacturing processes, and improvements in the PCE are described.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.3
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• pp.332-336
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• 2024

High-energy bandgap material silicon carbide (SiC) is gaining attention as a next-generation power semiconductor material, and in particular, SiC-based MOSFETs are developed as representative power semiconductors to increase the breakdown voltage (BV) of conventional planar structures. However, as the size of SJ (Super Junction) MOSFET devices decreases and the depth of pillars increases, it becomes challenging to uniformly form the doping concentration of pillars. Therefore, a structure with different doping concentrations segmented within the pillar is being researched. Using Silvaco TCAD simulation, a SJ VVD (vertical variation doping profile) MOSFET with three different doping concentrations in the pillar was studied. Simulations were conducted for the width of the pillar and the doping concentration of N-epi, revealing that as the width of the pillar increases, the depletion region widens, leading to an increase in on-specific resistance (R_on,sp) and breakdown voltage (BV). Additionally, as the doping concentration of N-epi increases, the number of carriers increases, and the depletion region narrows, resulting in a decrease in R_on,sp and BV. The optimized SJ VVD MOSFET exhibits a very high figure of merit (BFOM) of 13,400 KW/cm², indicating excellent performance characteristics and suggesting its potential as a next-generation highperformance power device suitable for practical applications.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.375-375
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• 2014

Layered semiconductor materials can be a promising candidate for large-area thin film transistors (TFTs) due to their relatively high mobility, low-power switching, mechanically flexibility, optically transparency, and amenability to a low-cost, large-area growth technique like thermal chemical vapor deposition (CVD). Unlike 2D graphene, series of transition metal dichalcogenides (TMDCs), $MX_2$ (M=Ta, Mo, W, X=S, Se, Te), have a finite bandgap (1~2 eV), which makes them highly attractive for electronics switching devices. Recently, 2D $MoS_2$ materials can be expected as next generation high-mobility thin-film transistors for OLED and LCD backplane. In this paper, we investigate in detail the electrical characteristics of 2D layered $MoS_2$ local bottom-gated transistor with the same device structure of the conventional thin film transistor, and expect the feasibility of display application.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.47-52
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• 2005

A lot of information storage devices have been introduced and developed for recently years. The trends of those devices are high capacity, compact size, low power consumption, reliability, and removability for data interchange with other device. As a satisfaction of these trends, near-field technique is in the spotlight as the next generation device. In order for a near-field recording to be successfully implemented in the storage device, a slider and suspension is introduced as actuating mechanism. The optical slider is designed considering near-filed optics. Suspension is not only supports slider performance, and tracking servo capacity but also meets the optical characteristics such as tilt aberration, and guarantee to satisfy shock performances for the mobility fir the actuator. In this study, the optical slider and the suspension for near-field probe array are designed and analyzed considering dynamic performance of head-gimbal assembly and shock simulation..

• Journal of the Economic Geographical Society of Korea
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• v.6 no.2
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• pp.293-306
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• 2003

This paper aims to clarify the change in industrial structure and industry itself, and makes suggestions for the industrial development direction at transitional periods in the Chungcheongbuk-do(province) region. Because profits of regional gross production in Chungcheongbuk-do region flow out of the region, basic industries must be brought up. For this phenomenon, main manufacturing must be developed for the industrial power of the next generation of high added values that combined with digital industry; the petrochemistry, semiconductor industry as major type of industry, and automobile industry as minor type of industry. Also for supporting industry, education service, health and welfare, research and development services that are knowledge-based service industries in Chungcheongbuk-do region, must be formated the network among corporations and constructed regional innovation system linked with educational institutions, precision chemistry industry and biology technology as major type of industry, and precision machinery and tools industry as minor type of industry.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1293-1294
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• 2006

OLEDs based on organic thin films are similar to semiconductor base light-emitting diodes in that they were also considered to be one of the next generation flat-panel displays. They are attractive because of low-operating voltage, low power consumption, ease of fabrication, and low cost. In this study, we used poly (3,4-ethylenedioxythiophene)/poly (4-styrenesulfonate) (PE DOT : PSS) as a hole injection layer. In this experiment spin coating method was used with various speed rate. The fundamental structure of the OLEDs was ITO/PEDOT:PSS/NPB/$Alq_3$/Al. As a result, we obtained the enhancement performance of OLEDs when the spin coating speed was 4000 rpm. We obtained a maximum luminance of 24334 $cd/m^2$ at a current density of 967 $mA/cm^2$.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.4
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• pp.8-16
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• 2023

The importance of next-generation packaging technologies is being emphasized as a solution as the miniaturization of devices reaches its limits. To address the bottleneck issue, there is an increasing need for 2.5D and 3D interconnect pitches. This aims to minimize signal delays while meeting requirements such as small size, low power consumption, and a high number of I/Os. Hybrid bonding technology is gaining attention as an alternative to conventional solder bumps due to their limitations such as miniaturization constraints and reliability issues in high-temperature processes. Recently, there has been active research conducted on SiCN to address and enhance the limitations of the Cu/SiO₂ structure. This paper introduces the advantages of Cu/SiCN over the Cu/SiO₂ structure, taking into account various deposition conditions including precursor, deposition temperature, and substrate temperature. Additionally, it provides insights into the core mechanisms of SiCN, such as the role of Dangling bonds and OH groups, and the effects of plasma surface treatment, which explain the differences from SiO₂. Through this discussion, we aim to ultimately present the achievable advantages of applying the Cu/SiCN hybrid bonding structure.

• Journal of IKEEE
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• v.24 no.1
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• pp.19-24
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• 2020

This paper presents a 3-level, 2-level SVPWM technique with 100 kHz switching using Verilog HDL, one of the languages of FPGA. In the case of IGBT devices mainly used in inverters, they have a switching frequency around 20kHz. Recent research and development of next-generation power semiconductor devices such as GAN has enabled switching of more than 100kHz, which can miniaturize power converters, and apply various new algorithms due to the injection of harmonics. In the existing system using the IGBT, the control using the DSP is common, but the controller configuration for 100 kHz switching requires the use of FPGA. Therefore, this paper explains the theory and implementation of SVPWM applied to two-level and three-level inverters using FPGAs and verifies the performance through the output waveform. In addition, this paper implements 3-level SVPWM by using only one carrier instead of using two carriers in the conventional method.