• 반도체디스플레이기술학회지
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• 제20권3호
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• pp.32-38
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• 2021

We developed an inductively coupled plasma (ICP) etcher for GaN etching using a parallel plasma electrode source with a multifunctional chuck matched to it in order for the low power consumption and low process cost in comparison with the conventional ICP system with a helical-type plasma electrode source. The optimization process condition using it for the micro light-emitting diode (µ-LED) chip fabrication was established, which is an ICP RF power of 300 W, a chuck power of 200 W, a BCl₃/Cl₂ gas ratio of 3:2. Under this condition, the mesa structure with the etch depth over 1 ㎛ and the etch angle over 75° and also with no etching residue was obtained for the µ-LED chip. The developed ICP showed the improved values on the process pressure, the etch selectivity, the etch depth uniformity, the etch angle profile and the substrate temperature uniformity in comparison with the commercial ICP. The µ-LED chip fabricated using the developed ICP showed the similar or improved characteristics in the L-I-V measurements compared with the one fabricated using the conventional ICP method

• Journal of the Korean Physical Society
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• 제73권12호
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• pp.1879-1883
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• 2018

We analyzed the deep-trap states of GaN/InGaN ultraviolet light-emitting diodes (UV LEDs) before and after electrical stress. After electrical stress, the light output power dropped by 5.5%, and the forward leakage current was increased. The optical degradation mechanism could be explained based on the space-charge-limited conduction (SCLC) theory. Specifically, for the reference UV LED (before stress), two sets of deep-level states which were located 0.26 and 0.52 eV below the conduction band edge were present, one with a density of $2.41{\times}10^{16}$ and the other with a density of $3.91{\times}10^{16}cm^{-3}$. However, after maximum electrical stress, three sets of deep-level states, with respective densities of $1.82{\times}10^{16}$, $2.32{\times}10^{16}cm^{-3}$, $5.31{\times}10^{16}cm^{-3}$ were found to locate at 0.21, 0.24, and 0.50 eV below the conduction band. This finding shows that the SCLC theory is useful for understanding the degradation mechanism associated with defect generation in UV LEDs.

• 한국진공학회지
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• 제14권2호
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• pp.84-90
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• 2005

분자선에피를 이용한 $In_{0.2}Ga_{0.8}N/GaN$ 이종접합 구조의 에피성장에 미치는 플라즈마의 rf전력의 영향에 대해 고찰하였다. 플라즈마를 발생시키는 rf 전력과 플라즈마 챔버압력의 조건에 따라 성장표면에 도달하는 분자나 원자의 에너지와 flux가 조절되어 에피성장 속도와 물질적 특성을 변화시킨다. 전력이 너무 낮거나 높은 조건에서 표면거칠기와 광특성이 각각 저하된 결과를 보였으며, 적정한 전력인 400W에서 성장한 $In_{0.2}Ga_{0.8}N/GaN$이 종접합 구조에서 날카로운 계면과 강한 photoluminescence 피크를 보였다. 이러한 현상에 대한 원인으로 고에너지 입자들이 성장표면에서 작용하는 기구들인 플라즈마에 의한 탈착과 표면확산, 성장표면의 하부에 주입되는 결함의 발생에 대하여 논하였다.

• 전력전자학회논문지
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• 제25권3호
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• pp.204-212
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• 2020

In this study, device suitability analysis is performed by comparing the performance of SiC MOSFET and GaN Transistor, which are WBG power semiconductor devices in the induction heating (IH) system. WBG devices have the advantages of low conduction resistance, switching losses, and fast switching due to their excellent physical properties, which can achieve high output power and efficiency in IH systems. In this study, SiC and GaN are applied to a general half-bridge series resonant converter topology to compare the conduction loss, switching loss, reverse conduction loss, and thermal performance of the device in consideration of device characteristics and circuit conditions. On this basis, device suitability in the IH system is analyzed. A half-bridge series resonant converter prototype using the SiC and GaN of a 650-V rating is constructed to verify device suitability through performance comparison and verified through an experimental comparison of power loss and thermal performance.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.21-21
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• 2003

To increase the light-emission efficiency of LED, we increased the internal and external quantum efficiency by suppressing the defect formation in the quantum well and by increasing the light extraction efficiency in LED, respectively. First, the internal quantum efficiency was improved by investigating the effect of a low temperature (LT) grown p-GaN layer on the In$\sub$0.25/GaN/GaN MQW in green LED. The properties of p-GaN was optimized at a low growth temperature of 900oC. A green LED using the optimized LT p-type GaN clearly showed the elimination of blue-shift which is originated by the MQW damage due to the high temperature growth process. This result was attributed to the suppression of indium inter-diffusion in MQW layer as evidenced by XRD and HR-TEM analysis. Secondly, we improved the light-extraction efficiency of LED. In spite of high internal quantum efficiency of GaN-based LED, the external quantum efficiency is still low due to the total internal reflection of the light at the semiconductor-air interface. To improve the probability of escaping the photons outside from the LED structure, we fabricated nano-sized cavities on a p-GaN surface utilizing Pt self-assembled metal clusters as an etch mask. Electroluminescence measurement showed that the relative optical output power was increased up to 80% compared to that of LED without nano-sized cavities. I-V measurement also showed that the electrical performance was improved. The enhanced LED performance was attributed to the enhancement of light escaping probability and the decrease of resistance due to the increase in contact area.

• 전기전자학회논문지
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• 제22권2호
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• pp.427-431
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• 2018

본 논문에서는 최근 전력반도체 산업에서 활용되어지는 와이드밴드갭 반도체 중에 하나인 $Ga_2O_3$를 이용한 에피웨이퍼 성장에 관련되어 서술하였다. GaN 성장시 활용되어지는 HVPE법을 이용하여 Sn이 도핑된 $Ga_2O_3$ 기판웨이퍼에 평균 $5.3{\mu}m$ 두께로 성장시켰다. 일반적으로 화합물반도체의 에피 두께가 $5{\mu}m$일 경우 SiC의 경우 600V 전력반도체소자를 제작할 수 있으며, $Ga_2O_3$ 에피웨이퍼의 경우에는 1000V이상의 전력소자를 제작할 수 있다. 성장된 에피웨이퍼의 J-V 측정 결과 $2.9-7.7m{\Omega}{\cdot}cm^2$의 온저항을 얻을 수 있었으며, 역방향의 경우 상당히 높은 전압에서도 누설전류가 거의 없음을 알 수 있었다.

• 전자통신동향분석
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• 제29권6호
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• pp.53-62
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• 2014

본고는 최근 화두가 되고 있는 에너지 절감을 위해 고효율, 친환경의 WBG(Wide Band-Gap) 화합물반도체인 SiC(Silicon Carbide), GaN(Gallium Nitride) 전력반도체 소자 및 전력변환 모듈의 기술동향과 ETRI에서 연구개발 진행 중인 GaN 전력반도체 관련 기술에 대해 기술한다. WBG 전력반도체는 기존의 실리콘 전력반도체와 비교하여 열 특성 향상, 고속 스위칭, 고전압/고전류 특성 및 스위칭 손실 최소화 등이 가능하고 이에 따른 시스템의 소형화 및 전력효율 향상 효과를 얻을 수 있다. 특히, GaN 전력반도체 소자는 시장이 가장 넓게 형성되어 있는 900V 이하에 적용이 가능하며, 앞으로 시장이 커질 것으로 예상되는 HEV(Hybrid Electric Vehicle)/EV(Electric Vehicle)의 친환경 자동차에도 활용될 것으로 기대되고 있다. 본고는 최근의 일본과 미국에서의 WBG 전력반도체에 대한 관심 및 투자 방향과 GaN 전력반도체 소자에 대한 해외 기업의 업계동향에 대해서도 함께 살펴본다. 이러한 WBG 전력반도체에 대한 해외 선진업체의 산업동향과 더불어 ETRI에서 연구개발 중인 GaN 전력반도체 기술현황에 대해 전력소자 설계 및 제조공정, 패키징, 전력모듈 설계 제작 기술을 포함하여 기술한다.

• 전력전자학회논문지
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• 제22권4호
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• pp.297-304
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• 2017

The purpose of this paper is to analyze losses because of switching devices and the secondary side circuit diodes of 500 W full bridge dc-dc converter by applying gallium nitride (GaN) field-effect transistor (FET), which is one of the wide band gap devices. For the detailed device analysis, we translate the specific resistance relation caused by the GaN FET material property into algebraic expression, and investigate the influence of the GaN FET structure and characteristic on efficiency and system specifications. In addition, we mathematically compare the diode rectifier circuit loss, which is a full bridge dc-dc converter secondary side circuit, with the synchronous rectifier circuit loss using silicon metal-oxide semiconductor (Si MOSFET) or GaN FET, which produce the full bridge dc-dc converter analytical value validity to derive the final efficiency and loss. We also design the heat sink based on the mathematically derived loss value, and suggest the heat sink size by purpose and the heat divergence degree through simulation.

• JSTS:Journal of Semiconductor Technology and Science
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• 제17권2호
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• pp.204-209
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• 2017

We have investigated a Mo/Au gate scheme for use in AlGaN/GaN-on-Si HFETs. AlGaN/GaN-on-Si HFETs were fabricated with Ni/Au or Mo/Au gates and their electrical characteristics were compared after thermal stress tests. While insignificant difference was observed in DC characteristics, the Mo/Au gate device exhibited lower on-resistance with superior pulsed characteristics in comparison with the Ni/Au gate device.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2012년도 춘계학술대회
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• pp.686-689
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• 2012

본 논문에서는 ISE-TCAD를 이용하여 GaN 기반의 LED특성을 분석하였다. LED는 GaN 버퍼층을 기반으로 GaN 장벽과 InGaN 양자우물로 구성된 활성 영역, AlGaN EBL(Electron Blocking Layer)과 AlGaN HBL(Hole Blocking Layer)로 이루어져 있다. Auger 재결합률, 양자 우물의 폭과 수, EBL의 Al 몰분율의 변화에 따른 LED의 출력 전력 특성을 분석하고 효율 개선을 위한 몇 가지 기준을 제시하였다.