Effect of Thermal Annealing on Ni/Au Contact to p-GaN

이호성,문진영,김준호,안철현,조형균,이주영,김홍승 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.6

We deposited Ni (13 nm) / Au (30 nm) layers on p-GaN by using the dc sputtering method in order to produce low-resistivity Ohmic contacts. The Ni (13 nm) / Au (30 nm) contact layers were annealed in air for 15 min at various temperatures. The electrical and the structural properties of the Ni/Au contact to p-GaN were investigated. The current-voltage measurement showed that the resistance of the as-deposited sample was very high. However, the sample annealed at 600 ℃ showed Ohmic-like behavior with a specific contact resistance of 1.9 × 10−3 cm2. Further increasing the temperature caused the Ohmic-like behavior to be degraded. Transmission electron microscopy and Auger electron spectroscopy were used to characterize the interfacial structure between the Ni/Au electrode and the p-GaN layers. The Ni layer was in contact with the p-GaN before annealing. However, after annealing, the Au layer had diffused from the top layer to the interface. The Au layer on the p-GaN surface resulting from the indiffusion of Au atoms during annealing may contribute to effective Ohmic contact formation. We deposited Ni (13 nm) / Au (30 nm) layers on p-GaN by using the dc sputtering method in order to produce low-resistivity Ohmic contacts. The Ni (13 nm) / Au (30 nm) contact layers were annealed in air for 15 min at various temperatures. The electrical and the structural properties of the Ni/Au contact to p-GaN were investigated. The current-voltage measurement showed that the resistance of the as-deposited sample was very high. However, the sample annealed at 600 ℃ showed Ohmic-like behavior with a specific contact resistance of 1.9 × 10−3 cm2. Further increasing the temperature caused the Ohmic-like behavior to be degraded. Transmission electron microscopy and Auger electron spectroscopy were used to characterize the interfacial structure between the Ni/Au electrode and the p-GaN layers. The Ni layer was in contact with the p-GaN before annealing. However, after annealing, the Au layer had diffused from the top layer to the interface. The Au layer on the p-GaN surface resulting from the indiffusion of Au atoms during annealing may contribute to effective Ohmic contact formation.

운전조건이 PEM 수전해 셀의 성능에 미치는 영향

장상엽,김재동,박진모,소영석 한국가스학회 2024 한국가스학회지 Vol.28 No.1

재생에너지 자원이 풍부한 제주도에서 수전해 시스템을 활용하여 그린수소를 생산하는 실증단지를 준비 중이며, 수전해 시스템의 장기 운영시 상황을 검토하기 위하여, PEM 수전해 셀을 가속시험평가 하여 수전해 셀의 내구성을 검토하였고, 제주도 풍력기반의 전력패턴을 적용하였을 때 수전해 셀의 내구성을 검토하였다. 가속시험평가(저전류-고전류 반복 인가)를 800시간 진행한 후, PEM 수전해 셀의 성능이 최대 10%, 운전조건에서 5.5% 감소되었으며, 임피던스 분석결과 PEM 수전해 셀의 Ohmic 저항보다 전극의 분극저항이 크게 증가한 것을 확인할 수있다. 그리고 제주도의 풍력패턴을 적용하여 내구성평가를 진행한 경우, PEM 수전해 셀의 성능이 최대 1.6%, 운전조건에서 1% 미만의 성능감소를 보여주었으며, 임피던스 결과 Ohmic 저항 및 전극의 분극저항의 변화가 작은것을 알 수 있다. Green Hydrogen demonstration complex is under conduction in Jeju island which is rich in renewable energy resources and will produces green hydrogen using a water electrolysis systems. In order to check durability of long-term operation, AST(accelerated stress test) was applied and the power pattern based on Jeju Island's wind power was applied. After 800 hours of repeated application of low current and high current, the performance of the PEM water electrolysis cell was reduced by up to 10% and by about 5.5% in operating conditions. As the result of impedance analysis, it can be seen that the electrode polarization resistance greatly increased than ohmic polarization resistance. In addition, when the durability evaluation was conducted by applying the wind power pattern of Jeju Island, the performance of the PEM water electrolysis cell showed up to 1.6% and a decrease of less than 1% in operating conditions. As a result of the impedance, it can be seen that the change of ohmic resistance and electrode polarization resistance is small.

Study on the measurement accuracy of circular transmission line model for low-resistance Ohmic contacts on III-V wide band-gap semiconductors

Tong Liu,Rong Huang,Fangsen Li,Zengli Huang,Jian Zhang,Jianping Liu,Liqun Zhang,Shuming Zhang,An Dingsun,Hui Yang 한국물리학회 2018 Current Applied Physics Vol.18 No.7

The accuracy and error propagation for determining the low specific contact resistance of Ohmic contacts on IIIV wide band-gap semiconductors based on the circular transmission line model have been analyzed and the validity of this method is discussed in detail. The accuracy is more susceptible to the factors including data fitting method, electrical measurement technique and contact area correction. By using the equations of the original circular transmission line model to extract the fitting parameters, the calculation accuracy is much improved and the inapplicability of the linear least-square fitting is prevented. To further improve the accuracy, a four-probe current-voltage measurement technique was adopted to reduce the parasitic series resistances and the uncertainty bound, especially for the Ohmic contact with low sheet resistance of the semiconductor. Moreover, we have studied the size effect of contact pads of patterns and demonstrated that contact area correction is necessary for the semiconductor with high sheet resistance. A comprehensive error analysis is also performed to fully understand all the impact factors on this advanced method of specific contact resistance measurement, which is benefit for device performance evaluation and failure analysis.

State of Health Estimation for Lithium-ion Battery Based on D-UKF

Wang Qiuting,Jiang Yinzhu,Lu Yunhao 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.7

This paper considers an accurate estimation method of State of Health (SOH) for lithium battery. An improved battery model is proposed which is based on equivalent circuit model and battery internal electrochemical characteristics. In our study, Double Unscented Kalman Filtering (D-UKF) algorithm is designed to calculate State of Charge (SOC) and SOH of lithium battery at the same time. The feature of our new method is SOH estimation model is derived based on battery internal resistances. The Ohmic resistance (one of internal resistances) can be identified online based on D-UKF algorithm. Two filters defined as UKF1 and UKF2 are working together to calculate the real-value of SOC and Ohmic resistance to obtain final SOH value. The experimental results indicate that our new battery model considers different value of battery internal resistances on different working condition (as different voltages, different currents). Besides, our study verifies the performance and feasibility of new estimation method based on D-UKF. This new algorithm has the practical value to further study for other types of lithium battery.

Surface and Electrical Properties of Inductively-coupled Plasma-etched N-face n-GaN and a Method of Reducing the Ohmic Contact Resistance of Plasma-damaged N-face n-GaN

Tak Jeong,Hyun Haeng Lee,Kang Ho Kim,Seong Ran Jeon,이승재,Sang Hern Lee,이준기,백종협 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.3

An investigation of the surface and the electrical properties of inductively-coupled plasma (ICP)- etched N-face n-GaN is reported. Furthermore, a method for reducing the Ohmic contact resistance on plasma-damaged N-face n-GaN is proposed. The I−V characteristics show that the Cl2 flow rate used for the ICP etching has a strong influence on the Ohmic behavior of the etched N-face n-GaN. We also found that the surfaces of the ICP-etched N-face n-GaN were damaged by increasing the Cl2 flow rate, resulting in deteriorating Ohmic behavior. However, the plasma damage caused by the ICP etching could be removed by using a KOH etching process, which resulted in a decreased contact resistance.

Transmission Line Model을 이용한 InAs 나노와이어의 오믹접촉 특성 연구

조민혁,최찬호,신재철 한국물리학회 2015 새물리 Vol.65 No.10

In this paper, we examined the metal contact resistance of an InAs nanowire by using the transmission line model (TLM). The InAs nanowires were grown via a catalyst-free, self-assembled growth method using metal-organic chemical-vapor deposition (MOCVD). The heights of the InAs nanowires exceeded 20 μm, but their diameters were very uniform along the growth axis. The metal contact resistance of the InAs nanowire was dramatically reduced by using a rapid thermal annealing (RTA) process. In a nanowire-based device, minimizing the metal contact resistance is essential because of the very small metal-semiconductor contact area. The transmission line model for semiconductor nanowires demonstrated here can contribute to improving the electrical properties of nanowire-based devices. 본 논문에서는 무촉매 자발형성 방식으로 InAs 나노와이어를 성장하고, transmission line model (TLM) 방법을 이용하여 성장된 InAs 나노와이어와 메탈 간의 접촉저항 및 나노와이어의 전기적 특성을 분석하였다. InAs 나노와이어 성장을 위해 화학기상증착 장치가 이용되었으며, 성장된 InAs 나노와이어는 수십 마이크로미터의 길이까지 성장되어도 길이에 따라 일정한 직경을 가지는 특징을 보였다. 일정한 직경을 가지는 나노와이어는 TLM 방법의 측정에서 메탈의 접합면적을 간단하게 예측할 수 있어, 반도체-메탈 접촉저항을 좀더 정확하게 측정할 수 있다. 또한 수십 마이크로미터 길이까지 성장된 InAs 나노와이어는 포토리소그라피 공정을 통한 TLM 패턴 제작을 가능하게 하였다. 작은 메탈 접촉 면적으로 인해 오믹 접합이 특히 중요한 나노와이어 소자에서 접촉 저항을 간단하고 정확하게 측정할 수 있는 방법은 나노와이어를 기반으로 하는 전기 및 광전소자의 특성을 향상 시키는 데 기여할 수 있다.

The Development of an Electroconductive SiC-ZrB₂ Composite through Spark Plasma Sintering under Argon Atmosphere

Lee, Jung-Hoon,Ju, Jin-Young,Kim, Cheol-Ho,Park, Jin-Hyoung,Lee, Hee-Seung,Shin, Yong-Deok The Korean Institute of Electrical Engineers 2010 Journal of Electrical Engineering & Technology Vol.5 No.2

The SiC-$ZrB_2$ composites were fabricated by combining 30, 35, 40, 45 and 50 vol. % of zirconium diboride ($ZrB_2$) powders with silicon carbide (SiC) matrix. The SiC-$ZrB_2$ composites and the sintered compacts were produced through spark plasma sintering (SPS) under argon atmosphere, and its physical, electrical, and mechanical properties were examined. Also, the thermal image analysis of the SiC-$ZrB_2$ composites was examined. Reactions between $\beta$-SiC and $ZrB_2$ were not observed via x-ray diffraction (XRD) analysis. The apparent porosity of the SiC+30vol.%$ZrB_2$, SiC+35vol.%$ZrB_2$, SiC+40vol.%$ZrB_2$, SiC+45vol.%$ZrB_2$ and SiC+50vol.%$ZrB_2$ composites were 7.2546, 0.8920, 0.6038, 1.0981, and 10.0108%, respectively. The XRD phase analysis of the sintered compacts demonstrated a high phase of SiC and $ZrB_2$. Among the $SiC+ZrB_2$ composites, the SiC+50vol.%$ZrB_2$ composite had the lowest flexural strength, 290.54MPa, the other composites had more than 980MPa flexural strength except the SiC+30vol.%$ZrB_2$ composite; the SiC+40vol.%$ZrB_2$ composite had the highest flexural strength, 1011.34MPa, at room temperature. The electrical properties of the SiC-$ZrB_2$ composites had positive temperature coefficient resistance (PTCR). The V-I characteristics of the SiC-$ZrB_2$ composites had a linear shape in the temperature range from room to $500^{\circ}C$. The electrical resistivities of the SiC+30vol.%$ZrB_2$, SiC+35vol.%$ZrB_2$, SiC+40vol.%$ZrB_2$ SiC+45vol.%$ZrB_2$ and SiC+50vol.%$ZrB_2$ composites were $4.573\times10^{-3}$, $1.554\times10^{-3}$, $9.365\times10^{-4}$, $6.999\times10^{-4}$, and $6.069\times10^{-4}\Omega{\cdot}cm$, respectively, at room temperature, and their resistance temperature coefficients were $1.896\times10^{-3}$, $3.064\times10^{-3}$, $3.169\times10^{-3}$, $3.097\times10^{-3}$, and $3.418\times10^{-3}/^{\circ}C$ in the temperature range from room to $500^{\circ}C$, respectively. Therefore, it is considered that among the sintered compacts the SiC+35vol.%$ZrB_2$, SiC+40vol.%$ZrB_2$ and SiC+45vol.%$ZrB_2$ composites containing the most outstanding mechanical properties as well as PTCR and V-I characteristics can be used as an energy friendly ceramic heater or ohmic-contact electrode material through SPS.

The Development of an Electroconductive SiC-ZrB₂ Composite through Spark Plasma Sintering under Argon Atmosphere

Jung-Hoon Lee,Jin-Young Ju,Cheol-Ho Kim,Jin-Hyoung Park,Hee-Seung Lee,Yong-Deok Shin 대한전기학회 2010 Journal of Electrical Engineering & Technology Vol.5 No.2

The SiC-ZrB₂ composites were fabricated by combining 30, 35, 40, 45 and 50 vol. % of zirconium diboride (ZrB₂) powders with silicon carbide (SiC) matrix. The SiC-ZrB₂ composites and the sintered co㎫cts were produced through spark plasma sintering (SPS) under argon atmosphere, and its physical, electrical, and mechanical properties were examined. Also, the thermal image analysis of the SiC-ZrB₂ composites was examined. Reactions between β-SiC and ZrB₂ were not observed via x-ray diffraction (XRD) analysis. The apparent porosity of the SiC+30vol.%ZrB₂, SiC+35vol.%ZrB₂, SiC+40vol.%ZrB₂, SiC+45vol.%ZrB₂ and SiC+50vol.%ZrB₂ composites were 7.2546, 0.8920, 0.6038, 1.0981, and 10.0108%, respectively. The XRD phase analysis of the sintered co㎫cts demonstrated a high phase of SiC and ZrB₂. Among the SiC+ZrB₂ composites, the SiC+50vol. %ZrB₂ composite had the lowest flexural strength, 290.54㎫, the other composites had more than 980㎫ flexural strength except the SiC+30vol.%ZrB₂ composite; the SiC+40vol.%ZrB₂ composite had the highest flexural strength, 1011.34㎫, at room temperature. The electrical properties of the SiC-ZrB₂ composites had positive temperature coefficient resistance (PTCR). The V-I characteristics of the SiC-ZrB₂ composites had a linear shape in the temperature range from room to 500℃. The electrical resistivities of the SiC+30vol.%ZrB₂, SiC+35vol.%ZrB₂, SiC+40vol.%ZrB₂ SiC+45vol.%ZrB₂ and SiC+50vol.%ZrB₂ composites were 4.573×10?³, 1.554×10?³, 9.365×10?⁴, 6.999×10-4, and 6.069×10?⁴Ωㆍ㎝, respectively, at room temperature, and their resistance temperature coefficients were 1.896×10?³, 3.064×10?³, 3.169×10?³, 3.097×10?³, and 3.418×10?³/℃ in the temperature range from room to 500℃, respectively. Therefore, it is considered that among the sintered co㎫cts the SiC+35vol.%ZrB₂, SiC+40vol.%ZrB₂ and SiC+45vol.%ZrB₂ composites containing the most outstanding mechanical properties as well as PTCR and V-I characteristics can be used as an energy friendly ceramic heater or ohmic-contact electrode material through SPS.

손실 저감을 위해 분할된 도체를 가지는 인쇄 회로 기판형 무선충전 코일

신유준(Yujun Shin),박재형(Jaehyoung Park),김종훈(Jonghoon Kim),권병기(Byunggi Kwon),은희현(Heehyun Eun),최석민(Seokmin Choi),안승영(Seungyoung Ahn) 한국전자파학회 2019 한국전자파학회논문지 Vol.30 No.9

본 논문에서는 무선전력전송 시스템 코일의 저항성분에 의해 발생하는 전력손실을 저감하기 위하여 분할된 도체를 갖는 PCB형 코일구조를 제안하였다. 제안된 구조는 유한요소법 자기장 시뮬레이션을 이용하여 설계하였으며, 실제 제작된 코일의 측정을 통해 저감된 저항 값을 가진다는 것을 증명하였다. 또한, 무선전력전송 실험 수행을 통해, 같은 전력을 전송시켰을 때 기존의 구조보다 제안된 구조에서 코일에서 소모되는 전력이 감소한다는 것을 확인하였으며, 열 발생 또한 감소하는 것을 확인하였다. 이를 통해 무선전력전송 시스템의 효율이 증가하는 것을 확인하였다. In this paper, a printed circuit board(PCB)-type coil structure with split conductors is proposed to reduce the power loss caused by coil resistance. Simulated magnetic field measurement reveals that the proposed coil has reduced resistance. In addition, wireless power transfer experiments reveal that when the same power is transferred, the power consumption in the coil with the proposed structure is reduced compared with that having a conventional structure. Moreover, heat generation is also reduced in the coil with the proposed structure. Therefore, the new coil is confirmed to increase the efficiency of wireless power transfer system.

3차원 수치모사를 통한 연료극 지지식 관형 고체산화물 연료전지의 전지 성능에 대한 연결재 구조 효과

황지원(Ji Won Hwang),이정용(Jeong Yong Lee),조동현(Dong Hyun Jo),정현욱(Hyun Wook Jung),김성현(Sung Hyun Kim) 한국청정기술학회 2010 청정기술 Vol.16 No.4

본 연구에서는 유체유동해석프로그램인 Fluent를 이용하여 연료극 지지체식 관형 고체산화물 연료전지(SOFC)에서의 연결재 구조에 따른 성능 변화를 고찰하였다. 실험적 사실과 부합되는 이론적 결과를 확보하기 위해서는 전기적으로 전극과 하나로 되어있는 연결재의 구조가 전지 성능에 어떠한 영향을 미치는지 살피는 것이 중요하다. 두께가 작은 연결재가 단전지 성능을 우수하게 하는 것으로 보아 옴(ohmic) 저항에 직결되는 연결재의 두께가 전지 성능에 있어 주요 변수임을 확인하였다. 일정 두께로 고정된 조건 하에 연결재 폭을 변화시킨 경우, 전지 성능은 상대적으로 큰 차이를 보이지 않았다. 이는 본 연구에서 고려한 SOFC의 관형 구조 특성상 연결재의 폭으로는 원주 방향으로 흘러가는 전류 경로를 효과적으로 단축시킬 수 없기 때문으로 사료된다. Effect of interconnect structure on the cell performance in anode-supported tubular solid oxide fuel cell (SOFC) has been investigated in this study, employing the Fluent CFD solver. For the robust and reliable theoretical analysis corroborating experimental results, it is of great importance to elucidate the role of interconnect which is electrically connected with electrodes on the cell characteristics. From the fact that the thin interconnect provides the enhanced cell performance, it is revealed that the interconnect thickness is a key parameter that is able to effectively control the ohmic resistance. Under the constant thickness condition, the cell performance does not considerably change with the variation of interconnect width. This is because the current passage along with circumferential direction is not effectively altered by the change of interconnect width in tubular SOFC system.