• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.6
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• pp.88-97
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• 1994

We describe the design, fabrication, and performance of the optical fiber-photodiode 1$\times$12 arry module using mesa-type InS10.53T GaS10.47TAS/INP 1$\times$12 PIN photodiode array. We fabricated the PIN PD array for high-speed optical fiber parallel data link optimizing quantum efficiency, operating speed sensitivity from the PIN-FET structure, and electrical AC crosstalk. For each element of the array, the diameter of the photodetective area is 80 $\mu$m, the diameter of the p-metal pad is 90 $\mu$m, and the photodiode seperation is 250 $\mu$m to use Si v-groove. Ground conductor line is placed around diodes and p-metal pads are formed in zigzag to reduce Ac capacitance coupling between array elements. The dark current (IS1dT) is I nA and the capacitance(CS1pDT) is 0.9 pF at -5 V. No signifcant variations of IS1dT and CPD from element to element in the array were observed. We calulated the coupling efficiency for 10/125 SMF and 50/125 GI MMF, and measured the responsivity of the PD array at the wavelength is 1.55 $\mu$ m. Responsivities are 0.93 A/W for SMF and 0.96 A/W for MMF. The optical fiber-PD array module is useful in numerous high speed digital and analog photonic system applications.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.390-392
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• 2013

The research was observed the characteristic of ZnO based oxide semiconductors for the transparent conducting display. The optical-physical properties of ZnO based oxide semiconductors) grown on p-Si wafer were presented. ZnO based oxide semiconductors was prepared by the RF magnetron sputtering system. The characteristic of ZnO based oxide semiconductorswas strongly influenced by the amount of localized electron state by the defects. The PL spectra moved to long wave number with increasing the defects in the film. The mobility of a-IGZO film was increased with increasing the oxygen gas flow rate. The resistivity of ZnO based oxide semiconductors was also related to the mobility of ZnO based oxide semiconductors, and the mobility increased at the sample with low resistivity. The electric characteristic of a-IGZO TFTs showed that it is an n-type semiconductor.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1274-1276
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• 1993

The silicon-nitride films formed by laser CVD method are used for passivating GaAs surfaces. The electrical Properties of metal-insulator-GaAs structure are studied to determined the interfacial characteristics by C-V curves and deep level transient spectroscopy(DLTS). The SiN films are photolysisly deposited from $SiH_4\;and\;NH_3$ in the range of $100^{\circ}C-300^{\circ}C$ on P type, (100) GaAs. The hysteresis is reduced and interface trap density is lowered to $10^{12}-10^{13}$ at $100^{\circ}C-200^{\circ}C$. The surface leakage current is studied too. The passivated GaAs have a little leakage current compared to non passivated GaAs.

• Korean Journal of Materials Research
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• v.31 no.12
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• pp.727-731
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• 2021

In this study, we have investigated a selective emitter using a UV laser on BBr₃ diffusion doping layer. The selective emitter has two regions of high and low doping concentration alternatively and this structure can remove the disadvantages of homogeneous emitter doping. The selective emitters were fabricated by using UV laser of 355 nm on the homogeneous emitters which were formed on n-type Si by BBr₃ diffusion in the furnace and the heavy boron doping regions were formed on the laser regions. In the optimized laser doping process, we are able to achieve a highly concentrated emitter with a surface resistance of up to 43 Ω/□ from 105 ± 6 Ω/□ borosilicate glass (BSG) layer on Si. In order to compare the characteristics and confirm the passivation effect, the annealing is performed after Al₂O₃ deposition using an ALD. After the annealing, the selective emitter shows a better effect than the high concentration doped emitter and a level equivalent to that of the low concentration doped emitter.

• Journal of Powder Materials
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• v.31 no.3
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• pp.255-262
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• 2024

Nano-oxide dispersion-strengthened (ODS) superalloys have attracted attention because of their outstanding mechanical reinforcement mechanism. Dispersed oxides increase the material's strength by preventing grain growth and recrystallization, as well as increasing creep resistance. In this research, atomic layer deposition (ALD) was applied to synthesize an ODS alloy. It is useful to coat conformal thin films even on complex matrix shapes, such as nanorods or powders. We coated an Nb-Si-based superalloy with TiO₂ thin film by using rotary-reactor type thermal ALD. TiO₂ was grown by controlling the deposition recipe, reactor temperature, N₂ flow rate, and rotor speed. We could confirm the formation of uniform TiO₂ film on the surface of the superalloy. This process was successfully applied to the synthesis of an ODS alloy, which could be a new field of ALD applications.

• Journal of the Korean Magnetics Society
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• v.11 no.5
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• pp.222-225
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• 2001

The planar type inductors have a good potential for the application of miniaturized low power DC-DC converters. For those high quality application, the reduction of coil loss and also magnetic films which have good high frequency properties are required. Fabricated inductor was consisted of FeTaN/Ti magnetic film and electroplated Cu coil thickness of 100$\mu\textrm{m}$ and $SiO_2$ as a insulating layer. The inductor was designed double rectangular spiral shape for magnetic field highly confining within the device. The measured value of inductance and resistance were 980 nH and 1.7 $\Omega$ at 1 MHz as operating frequency of device. The Q factor is 3.55 at 1 MHz.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.20-20
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• 2003

We developed 30 ㎽-AlInGaN based violet laser diodes. The fabrication procedures of the laser diodes are described as follows. Firstly, GaN layers having very low defect density were grown on sapphire substrates by lateral epitaxial overgrowth method. The typical dislocation density was about 1-3$\times$10$^{6}$ /$\textrm{cm}^2$ at the wing region. Secondly, AlInGaN laser structures were grown on LEO-GaN/sapphire substrates by MOCVD. UV activation method, instead of conventional annealing, was conducted to achieve good p-type conduction. Thirdly, ridge stripe laser structures were fabricated. The cavity mirrors were formed by cleaving method. Three pairs of SiO$_2$ and TiO$_2$ layers were deposited on the rear facet for mirror coating. Lastly, laser diode chips were mounted on AlN submount wafers by epi-down bonding method. The lifetime of the laser diodes was over 10,000 hrs at room temperature under automatic power controlled condition. We expect the performance of the LDs to be improved by the optimization of the growth and fabrication process. The detailed characteristics and important issues of the laser diodes will be discussed at the conference.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.48-48
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• 2007

P-type transparent conducting $CuGaO_2$ thin films have been prepared by DC/RF sputtering using Quartz(0001) and sapphire(0001) substrates. The target was fabricated by heating a stoichiometric mixture of CuO and $Ga_2O_3$ at 1373K for 12h under $N_2$ atmosphere. The film were deposited under mixture gas of Ar and $O_2(Ar:O_2=4:1)$ during 10~30min. and the as-deposited films were annealed at 1123K and $N_2$ atmosphere. Room temperature conductivity and the activation energy of the sintered body in the temperature range of 223K ~ 423K were 0 004S/cm, 1.9eV, respectively. XRD revealed that all of the as-deposited films were amorphous. Heating of the films deposited on Quartz substrates above 1123K resulted in crystallization with a second phase of $CuSiO_3$, which was assumed owing to reaction with Quartz substrate. The single phase of $CuGaO_2$ was obtained at the film deposited on the sapphire substrates. The transmittance after annealing of DC- and RF-sputtered films were 55~75% at 550nm. From the transmittance and reflectance measurement. the direct band gap of the DC/RF-sputtered films were 3.63eV and 3.57eV. and there was little difference between DC and RF sputtered films.

• Korean Journal of Materials Research
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• v.21 no.10
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• pp.573-579
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• 2011

Highly textured Ag, Al and Al:Si back reflectors for flexible n-i-p silicon thin-film solar cells were prepared on 100-${\mu}m$-thick stainless steel substrates by DC magnetron sputtering and the influence of their surface textures on the light-scattering properties were investigated. The surface texture of the metal back reflectors was influenced by the increased grain size and by the bimodal distribution that arose due to the abnormal grain growth at elevated deposition temperatures. This can be explained by the structure zone model (SZM). With an increase in the deposition temperatures from room temperature to $500^{\circ}C$, the surface roughness of the Al:Si films increased from 11 nm to 95 nm, whereas that of the pure Ag films increased from 6 nm to 47 nm at the same deposition temperature. Although Al:Si back reflectors with larger surface feature dimensions than pure Ag can be fabricated at lower deposition temperatures due to the lower melting point and the Si impurity drag effect, they show poor total and diffuse reflectance, resulting from the low reflectivity and reflection loss on the textured surface. For a further improvement of the light-trapping efficiency in solar cells, a new type of back reflector consisting of Ag/Al:Si bilayer is suggested. The surface morphology and reflectance of this reflector are closely dependent on the Al:Si bottom layer and the Ag top layer. The relationship between the surface topography and the light-scattering properties of the bilayer back reflectors is also reported in this paper.

• Korean Journal of Soil Science and Fertilizer
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• v.10 no.1
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• pp.39-48
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• 1977

The results of the determination of the optimum level of nitrogen fertilizer experiment for rice paddy at 21 locations over the country in 1975 year are as follows. 1. The yields of control and N-fertilized plots of ordinary variety (Japonica type) were normal paddy soil>sandy paddy soil>poorly drained paddy soil. Control plots of Tongil variety, (Indica type) however, were sandy poorly drained soil>sandy normal paddy soil=clay poorly drained soil, and N-fertilized plots were normal paddy soil>sandy poorly drained soil>sandy soil>clay poorly drained soil. In other words Tongil variety has higher adaptability to sandy soil under no nitrogen. 2. The yield response to N-fertilizer was higher in normal paddy soil than sandy soil. The productivity per 1kg of nitrogen was 16.6kg in normal paddy soil, 10.5 in sandy soil, and 8.6-11.4 in poorly drained soil for Tongil variety. For ordinary variety, they were 12.6, 6.3, 6.6-9.3kg respectively. 3. Ripening ratio for ordinary variety and ripening ratio and grain weight for Togil variety were higher in sandy soil than normal paddy soil. The main reason why the N-response in mormal paddy soil is higher was appeared to be higher number of effective tillers in normal paddy soil. 4. The optimum rates of N-fertilizer in average were 19.4 in normal paddy soil, 14.6 in sandy soil, and 11.6-13.4kg/10a in poorly drained soil for Tongil variety. For ordinary variety they were 15.9, 10.2, and 8.7-12.7kg/10a respectively. 5. The optimum rate of nitrogen was increased with the increase of productivity in normal paddy soils. In sandy soils and poorly drained soils it was not proved. 6. The optimum rates of N-fertilizer calculated from field experiment were somewhat different from the optimum rates calculated from $SiO_2/OM$ ratio. However, the values calculated both ways showed high correlation. It would be recommendable, therefore, to use $SiO_2/OM$ ratio to calculate the optimum rates of N-fertilizer after revising this equation considering different rice varieties and soil types or water management and climate.