• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04b
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• pp.69-72
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• 2002

We establish a visible light emission from porous polycrystalline silicon nano structure(PPNS). The PPNS layer are formed on heavily doped n-type Si substrate. 2um thickness of undoped polycrystalline silicon deposited using LPCVD (Low Pressure Chemical Vapor Deposition) anodized in a HF: ethanol(=1:1) as functions of anodizing conditions. And then a PPNS layer thermally oxidized for 1 hr at $900^{\circ}C$. Subsequently, thin metal Au as a top electrode deposited onto the PPNS surface by E-beam evaporator and, in order to establish ohmic contact, an thermally evaporated Al was deposited on the back side of a Si-substrate. When the top electrode biased at +6V, the electron emission observed in a PPNS which caused by field-induces electron emission through the top metal. Among the PPNSs as functions of anodization conditions, the PPNS anodized at a current density of $10mA/cm^{2}$ for 20 sec has a lower turn-on voltage and a higher emission current. Furthermore, the behavior of electron emission is uniformly maintained.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.2
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• pp.7-12
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• 2007

A SPICE-based 3-dimensional circuit model of LED(Light-Emitting Diode) was developed for the design optimization and analysis of high-brightness LEDs. An LED is represented as an array of pixel LEDs with small preassigned areas, and each of the pixel LEDs is composed of circuit networks representing the thin-film layers(n-metal, n- and p-type semiconductor layers, and p-metal), ohmic contacts, and pn-junctions. Each of the thin-film layers and contact resistances is modeled by a resistance network, and the pn-junction is modeled by a conventional pn-junction diode. It has been found that the simulation results using the model and the corresponding parameters precisely fit the measured LED characteristics.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.331-331
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• 2014

3족 질화물에 기반한 발광다이오드는 비소화물이나 인화물에 비해 여러 가지 장점을 가져 각광받아왔다. 특히, (Al)GaN 에 기반한 자외선 영역 발광 다이오드는 자외선 경화, 소독 등의 여러 가지 응용 가능성을 가진다 [1]. 하지만, 심자외선 영역으로 갈수록 높은 접촉 저항과 투명전극에서의 광흡수에 의해 전류주입 효율과 광추출 효율이 감소하여 결국 외부양자 효율이 더욱 열화되는 특성을 보인다. 이는 넓은 밴드갭을 가지는 물질을 이용하여 p-(Al)GaN 층에서 오믹접촉을 이루어야만 해결이 가능하지만 아직까지 이러한 결과가 보고된 바 없다. 본 연구에서는, 우리는 넓은 밴드갭을 가지는 silicon dioxide (SiO2) 에 전기장을 인가하여 p-GaN, and p-AlGaN 층에 전도성 필라멘트를 형성하여 전기전도도를 부여하는 연구를 진행하였다. p-GaN 과 p-AlGaN 위에서 5 nm 두께의 SiO2는 schottky 한 특성과 280 nm의 파장대역에서 약 97%의 투과율을 보였다. 비록 schottky 장벽이 형성되었지만, 전기전도도가 크게 향상되었으며 심자외선 영역에서 매우 낮은 흡수율을 보였다. 이는 기존의 증착후 열처리를 거쳐 제조된 전극에 비하여 우수한 특성을 지니며 향후 심자외선 영역 발광다이오드의 p-(Al)GaN 층 위에 오믹접촉을 이룰수 있는 가능성을 제시한다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.367-367
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• 2011

태양전지에서 광흡수층으로 널리 쓰이는 CuInSe2은 전기적, 광학적 특성이 우수하고 20%대의 고효율을 기록하며 큰 관심을 받고 있다. 하지만 증발법 및 스퍼터링 등의 기존 진공, 고온 기반 공정 기술은 원천적인 공정비용 절감이 어렵고, 고가의 희귀원소인 In 등의 원료 활용도가 떨어져 실험실 수준에 머무르고 있다. 최근 공정 비용을 최소화와 원료 활용을 극대화를 통해 고효율 CIGS 박막형 태양전지를 제조하기 위해 비진공 방식의 전구체 박막 코팅 및 열처리를 통한 광흡수층 제조에 관한 연구가 활발히 진행되고 있으며, 본 연구는 doctor-blade coating을 이용하여 전구체 박막을 기판 위에 형성하고 열처리 온도에 따른 박막 물성 변화를 관찰함으로써 박막 형성 메커니즘을 밝히는데 주력하였다. 또한 합성된 박막의 전기적, 광학적 특성을 분석하여 태양전지 응용 가능성을 살펴보았다. 본 연구에서는 SEM, XRD, TGA 분석을 통해 Cu, In, Se 전구체들이 각각 binary phase, 즉, Cu2-xSe 및 In2Se3의 metal chalcogenide을 형성하고, 고온에서 서로 결합하여 CuInSe2로 결정화 되는 현상을 관찰하였다. 또한 합성된 CIS 박막은 근적외선 및 가시광 영역에서 높은 광흡수도를 보였으며, 전기적으로 Mo 전극과 ohmic contact을 이룸으로써 CIGS계 태양전지의 광흡수층으로의 적합성을 나타내었다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.11
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• pp.1005-1009
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• 2006

High quality three-dimensional (3D) heterostructures were constructed by selective area (SA) molecular beam epitaxy (MBE) using a specially patterned GaAs (001) substrate to improve the efficiency of tarrier transport. MBE growth parameters such as substrate temperature, V/III ratio, growth ratio, group V sources (As2, As4) were varied to calibrate the selective area growth conditions and the 3D GaAs-AlGaAs heterostructures were fabricated into the ridge type and the V-groove type. Scanning micro-photoluminescence $({\mu}-PL)$ measurements and the following analysis revealed that the gradually (adiabatically) coupled 1D-2DEG (electron gas) field effect transistor (FET) system was successfully realized. These 3D-heterostructures are expected to be useful for the realization of high-performance mesoscopic electronic devices and circuits since it makes it possible to form direct ohmic contact onto the (quasi) 1D electron channel.

• Nuclear Engineering and Technology
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• v.51 no.8
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• pp.1978-1982
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• 2019

The paper presents the electrical performance measurements of a prototype nuclear battery and two types of betavoltaic cells. The electrical performance was assessed by measuring current-voltage properties (I-V) and determining the short-circuit current and the open-circuit voltage. With ⁶³Ni as an irradiation source, the open-circuit voltage and the short-circuit current were determined as 1 V and 64 nA, respectively. The prototype consisted of 10 betavoltaic cells that were prepared using radioactive ⁶³Ni. Electroplating of the radioactive ⁶³Ni on an ohmic contact (Ti-Ni) was carried out at a current density of 20 mA/㎠. Two types of betavoltaic cells were studied: with an external ⁶³Ni source and a ⁶³Ni-covered source. Under irradiation of the ⁶³Ni source with an activity of 10 mCi, the open-circuit voltage V_oc of the fabricated cells reached 151 mV and 109 mV; the short-circuit current density J_sc was measured to be 72.9 nA/cm2 and 64.6 nA/㎠, respectively. The betavoltaic cells had the fill factor of 55% and 50%, respectively.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1216-1219
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• 1994

A reflection type SEED from LP-MOCVD grown InGaAs/GaAs ESQW structures, with 5% In fraction, has been fabricated and its basic characteristics were investigated. Its intrinsic region consists of 50 pairs of alternating $100{\AA}$ $In_{0.05}Ga_{0.95}As$ barrier and $100{\AA}$ GaAs layers. And a multilayer reflector stack of $Al_{0.12}Ga_{0.88}As(641{\AA})-/AlAs(774{\AA})$ was vertically integrated below the p-i-n structures. The device processing includes the mesa etching, insulator deposition, indium metallization, and thermal alloy for Ohmic contact. Photocurrent spectrum measurement showed the exciton absorption peak at 905nm and availability as a optical switching device. This device showed a contrast ratio of 2:1 by the reflectance spectrum measurement.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.9
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• pp.36-45
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• 1992

The Modified Multi-Quantum Well(MMQWAl) structures have been grown by Mental-Organic chemical Vapor Deposition(MOCVD) method and stripe type MMQW laser diodes have been investigated. In the case of GaAs/AlGaAs superlattice and quantum well growth by MOCVD, the periodicity, interface abruptess, Al compositional uniformity and layer thickness have been confirmed though the shallow angle lapping technique, double crystal x-ray diffractometry (DCXD) and photoluminescence (PL) measurement. stripe-type MMQW laser diodes have been fabricated using the process technology of photolithography, chemical etching, ohmic contact, back side removing and cleaving. As the result of the electrical and opticalmeasurement of these laser diodes, we have achieved the series resistance of $1[\Omega}~2{\Omega}$ by current-voltage measurements, the threshold current of 200-300mA by currnt-light measurements and the lasing wavelength of 8000-8400$\AA$ by lasing spectrum measurements.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.6
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• pp.563-567
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• 2006

Indium tin oxide (ITO) used as an electrode in organic light emitting diodes (OLEDs) and organic thin film transistors (OTFTs) was modified by a self-assembled monolayer (SAM). For device fabrication, surface of the ITO was modified by immersion in a solution including various phosphonic acid at room temperature in order to increase work function of an electrode. The work function of ITO with SAM was measured by Kelvin probe. Work function increase of 0.88 eV was observed in ITO with various SAM. Therefore, ohmic contact is achieved in an interface between ITO and organic semiconductors (pentacene). We analyzed the origin of work function increase of ITO with SAM by X-ray photoelectron spectroscopy. We confirmed that increase of oxygen bonding energy attributed to increase the work function of ITO. These results suggested that ITO with the SAM gives a high possibility for high performance of OLEDS and OTFTs.

• Electrical & Electronic Materials
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• v.10 no.1
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• pp.39-44
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• 1997

Bulk type radiation detector of Au/Cd$_{1-x}$ Zn$_{x}$Te(x=20%)/Au structure using Cd$_{1-x}$ Zn$_{x}$Te(x=20%) wafer(3x4xl mm$^{3}$) grown by high pressure Bridgman method has been developed. We etched wafer surfaces with 2% Br-methanol solution and coated gold thin film on the surfaces by electroless deposition method for 5 min. in 49/o HAuCI$_{3}$ 4H20 solution. Initial etch rates of Cd, Zn and Te were 46%, 12% and 42% respectively. After etched, the surface of wafer was slightly revealed to Te rich condition. The leakage current was increased with etch time, but it didn't exceed 3nA at 50volt. The thickness of Au film was about 100nm by Rutherford Backscattering Spectroscopy(RBS). The resolution were 6.7% for 22.1 keV photon from 109 $^{109}$ Cd and 8.2% for 59.5 keV photon from $^{241}$ Am. The radiation detector such as Au/Cd$_{1-x}$ Zn$_{x}$Te(x=20%)/Au structure was more effective to monitor the low energy gamma radiation.iation.