• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.10a
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• pp.149-154
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• 1997

광소자 및 새로운 개념의 전력소자 응용을 위하여 Wide Bandgap 반도체에 대한 관심이 급증되고 있다. 특히 직접천이형인 GaN는 청색 발광소자 응용 및 고출력, 고주파용 전력소자 응용에 이상적인 전자물성을 갖고 있다. 따라서 본 연구에서는 GaCl$_3$와 NH$_3$를 source gas로 하는 CVPE법을 사용하여 (0001) sapphire와 비교하였다. 기판의 증착온도 104$0^{\circ}C$에서 source gas의 III/V flow rate를 2로 분석하여 45분간 성장시킨 경우 그 증착속도는 약 40 $\mu\textrm{m}$/hr 정도였으며, 이 때 XRD을 향상시키기 위하여 증착이전에 기판의 표면에 증착온도에서 NH$_3$를 이용한 nitridation 처리를 하였으며, 그 처리시간이 3분일 때 XRD의 FWHM 특성이 가하여 조사한 결과 363 nm에서 peak가 검출되었다. 본 연구에서는 양질의 GaN 박막성장을 위한 증착조건 인자중 source gas의 flow rate가 가장 중요한 변수임을 적정 온도 범위가 75$0^{\circ}C$ 근처로 조사되었다. 실험과 모사결과의 박막 증착 최적온도의 차이는 GaN 증착시의 반응 Kinetics가 느리기 때문인 것으로 해석된다.

• Transactions on Electrical and Electronic Materials
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• v.7 no.1
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• pp.12-15
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• 2006

We present the structural, magnetic, and electrical properties in the (Al,Mn)N films with various Mn concentrations grown by plasma-enhanced molecular beam epitaxy. X-ray diffraction analyses reveal that the (Al,Mn)N films have the wurtzite structure without secondary phases. All (Al,Mn)N films showed the ferromagnetic ordering. Particularly, ($Al_{1-x}Mn_{x}$)N film with x = 0.028 exhibited the highest magnetic moment per Mn atom at room temperature. Since all the films exhibit the insulating characteristics, the origin of ferromagnetism in (Al,Mn)N might be attributed to either indirect exchange interaction caused by virtual electron excitations from Mn acceptor level to the valence band within the samples or a percolation of bound magnetic polarons arisen from exchange interaction of localized carriers with magnetic impurities in a low carrier density regime.

• Journal of Power Electronics
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• v.12 no.1
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• pp.19-23
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• 2012

This paper presents a practical methodology for realistic simulation on reverse characteristics of Wide Bandgap (WBG) SiC and GaN p-n junctions. The adjustment on certain physic-based model parameters, such as the trap density and photo-generation for SiC junction, and impact ionization coefficients and critical field for GaN junction are described. The adjusted parameters were used in Synopsys Medici simulation to obtain a realistic p-n junction avalanche breakdown voltage. The simulation results were verified through benchmarking against independent data reported by others.

• The Magazine of the IEIE
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• v.37 no.8
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• pp.31-40
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• 2010

1947년 트랜지스터의 발명을 시작으로 사이리스터, MOSFET 및 IGBT 등의 전력반도체 소자가 개발되면서 산업, 가전 및 통신 등의 다양한 분야에서 실리콘 기반의 전력반도체 소자가 활용되고 있다. 개발 당시에는 10A/수백V 정도의 전류통전능력 및 전압저지능력을 가지고 있었지만, 현재에는 8000A/12kV급의 대용량 소자까지 생산되고 있다. 이러한 전력반도제 소자는 다양한 응용분야에 서 높은 전압 저지능력, 큰 전류 통전 능력 및 빠른 스위칭 특성을 요구하고 있다. 특히 최근의 전력변환장치들은 고온동작특성 및 고효율화에 대한 요구가 더욱 강조되고 있다. 일반적인 실리콘 전력반도체소자는 물질적인 특성한계로 고온에 서의 동작 시 소자 특성이 떨어지는 특징을 보이고 있어 고온 환경에 적합한 전력반도체 소자의 필요성이 증가되어 실리콘에 비해 밴드�b이 넓은 SiC 및 GaN 등의 wide bandgap 반도체 물질의 연구가 활발히 진행되고 있다. 특히 SiC는 단결정 성장을 통한 웨이퍼화가 용이하고 소자 제작공정이 기존 실리콘공정과 유사하여 많은 연구가 진행되었으며 일부 소자에서 상용화가 진행되었다. 본고에서는 현재 활발히 진행되고 있는 탄화규소 전력반도체소자의 기술동향에 대해 소개하고자 한다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.68-68
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• 2003

SiC는 wide bandgap 물질로서 그 material properties로 인하여, high tmperature, high power, high frequency영역으로의 사용이 기대되는 물질이다. 따라서 SiC에 대한 기본적인 연구와 더불어, 그 소자 제작 및 응용에의 연구가 절실한 시점이다. 이에, SiC 기본적인 소자중 하나인 Schottky diode에 대해 연구하였다. 본 논문은 Schottky contact 물질로써 현재까지 연구가 미비한 Ru을 사용하였다. Ru은 Pt 계열물질로써, 다른 metal에 비하여 열역학적으로 안정하며, 또한 그의 산소 화합물인 RuO2는 다른 oxide에 비하여 전도성 이 높은 장점을 가지고 있다. 따라서 Ru-SiC diode는 이러한 측면에서 연구할 만한 가치가 있다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.9
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• pp.1351-1358
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• 2017

In this work, we investigated radiation hardness of GaN-based transistors which are strong candidates for next-generation power electronics. Field effect transistors with three types of gate structures including metal Schottky gate, recessed gate, and p-AlGaN layer gate were fabricated on AlGaN/GaN heterostructure on Si substrate. The devices were irradiated with energetic protons and alpha-particles. The irradiated transistors exhibited the reduction of on-current and the shift of threshold voltage which were attributed to displacement damage by incident energetic particles at high fluence. However, FET operation was still maintained and leakage characteristics were not degraded, suggesting that GaN-based FETs possess high potential for radiation-hardened electronics.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.628-628
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• 2013

Graphene, a single layer of graphite, has raised extensive interest in a wide scientific community for its extraordinary thermal, mechanical, electrical and other properties [1,2]. However, because of zero-band gap of graphene, it is difficult to apply for electronic applications. To overcome this problem, chemical doping is one of way to opening grahene bandgap. According to experimental results, by changing doping concentration and doping time, it is possible to control work function of graphene. We can obtain results through raman spectroscopy, UPS, Sheet resistance. Moreover, electronic properties of doped graphene were studied by making field effect transistors. We were able to control the doping concentration, dirac point of graphene and work function of graphene by formng n-type, p-type doping materials. In this research, the chemicals of diazonium salts, viologen, etc. were used for extrinsic doping.

• JSTS:Journal of Semiconductor Technology and Science
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• v.2 no.2
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• pp.141-146
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• 2002

The effect of the wide-bandgap Schottky barrier enhancement cap layer on the performance of metal-semiconductor-metal photodetectors (MSMPD's) is presented. Judged by the dc characteristics, no considerable increase in recombination loss of carriers is resulted by the incorporation of the cap layer. However, about 45% of the detection efficiency is lost for the cap-layered MSMPD's even with a graded layer incorporated under pulse operation, and it was found to be due mainly to the capturing and slow release of the photocarriers at the heterointerface. The loss mechanism of the pulse detection efficiency is believed to be responsible for the intersymbol interference and the increased bit-error-rate (BER) observed in MSMPD's when used with a high bit rate pseudo-random-bit-stream (PRBS) data pattern.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.5
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• pp.922-926
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• 2010

We have investigated the grating coupled surface plasmon resonance (GC-SPR) sensors using ZnO nano-grating structures to enhance the sensitivity of an SPR sensor. The GC-SPR sensors were analyzed using the finite-difference time-domain method. The optimum resonance angles of 49 degrees are obtained in the 150 nm wide grating structure with a period of 300 nm for the ZnO thickness of 30 nm. Then, the ZnO nano-grating patterns were fabricated by using laser interference lithography. The measured resonance angle of nano-grating patterns was around 49 degrees. Here, an enhanced evanescent field is obtained due to the surface plasmon on the edge of the bandgap when the ZnO grating structures are used to excite the surface palsmon.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.7
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• pp.991-996
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• 2010

Blue-green and green LEDs have been successfully fabricated grown by MBE, which has introduced the $ZnS_ySe_{1-x-y}:Te_x$ (x=0.04, y~0.11-0.14) ternary epilayer as an active layer. From the I-V characteristics, the built-in voltage (~2.1 V) is very small compared to other wide bandgap LEDs, such as commercial InGaN-based LEDs (>3.2 V). From the C-V profiling, the effective carrier concentration in the p-type ZnMgSSe cladding layer was evaluated as ${\sim}2.8{\times}10^{16}\;cm^{-3}$ for the present LEDs.