• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.46.2-46.2
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• 2011

CuInSe2 (CIS)계 화합물은 3족 원소(Ga, Al) 또는 6족 원소(S)를 첨가하여 밴드갭 조절이 가능하다는 장점을 가지고 있다. 실제로 동시 증발법으로 Ga을 첨가하여 만든 CuIn0.7Ga0.3Se2(CIGS) 태양전지는 약20%의 높은 효율 보이고 있다. 그러나 최고 효율을 달성한 동시 증발법은 대면적화가 어렵다는 점이 상용화의 걸림돌로 작용하고 있다. 따라서, 그 대안으로 대면적화가 용이한 스퍼터링 및 셀렌화 공정 연구가 진행되고 있다. 그러나 스퍼터링/셀렌화 공정은 Cu-In-Ga 금속 전구체의 셀렌화 시 Ga이 Mo쪽으로 이동하여 CIS/CGS 2개의 상으로 형성된다는 큰 단점을 갖고 있다. 이를 해결하기 위해 셀렌화 후 다시 H2S 기체 분위기에서 열처리하여 표면 밴드갭을 증가시키는 공정이 사용되고 있으나, 이는 열처리 과정이 2번 필요하다는 단점을 갖고 있다. 이러한 단점을 해결하고자 본 연구에서는 금속 전구체의 구조, 셀렌화 공정 조건 및 전구체 내의 상(phase) 조절을 통해 셀렌화 시 Ga segregation을 억제하고자 하였다. 특히 전구체의 상 조절을 통해서 Ga의 이동을 크게 완화시킬 수 있음을 확인하였다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.1
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• pp.19-31
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• 1996

To invetigate the impurity distribution in GaAs crystal grown by horizontal Bridgman method, we constructd the mathematical model describing heat transfer, mass transfer and fluid flow n transient growth of GaAs. Galerkin finite element method and implicit time integration were used to solve the equations and simulate the transient growth. The concentration distribution is similar to the case of diffusion controlled growth when Gr - 0. With the increase of Gr the concentration profile is distroted and the minimum solute concentration appears near the interface. As solidification prosceeds, interface deflection increases steadily and transverse segregation increases until mixing by flow becomes steady. The axial segregation increases with solidification. But, with high intensity of flow axial segregation becomes steady after short transient. At small and large Gr the result showed a good agreememt with the prediction Smith and Scheil.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.3
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• pp.558-564
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• 2012

We fabricated Ga doped ZnO (GZO) thin films on the glass substrate (Eagle 2000) with various of Ga doping concentration and annealing temperatures using sol-gel method, electrical and optical properties were investigated. When the GZO thin films doped with 1 mol% of Ga and annealed at $600^{\circ}C$, the excellent (002) orientation was observed. In the results of Hall measurement, carrier concentration decreased and resistivity increased due to segregation effect with increasing of the Ga doping concentration. The largest carrier concentration and lowest resistivity were $9.13{\times}10^{18}cm^{-3}$ and $0.87{\Omega}cm$, respectively, in the GZO thin films doped with 1 mol% Ga and annealed at $600^{\circ}C$. All films is higher than 80 % in the visible light region. Energy band gap narrowing due to Burstein-Moss effect was observed with increasing of Ga doping concentration from 1 to 4 mol%.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.2
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• pp.75-78
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• 2009

Si-doped GaAs single crystals were grown by vertical gradient freeze using PBN crucibles. The amount of oxide layer $B_{2}O_{3}$ in PBN crucible was changed($0{\sim}0.2wt%$) and measured the concentration of carriers. The segregation coefficients of Si in GaAs melt decreased rapidly from initial 0.1 to 0.01 as the amount of $B_{2}O_{3}$ increases. At the same time, concentration of carriers was shown to decrease. It is likely that the reaction between dopant Si and $B_{2}O_{3}$ in GaAs melt results in the reduction of Si dopants(donor) while increase in the amount of boron(acceptor). The thin layer of $B_{2}O_{3}$ glass in PBN crucible was proved to be a better way to reduce defect formation rather than the total amount of $B_{2}O_{3}$.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.35 no.2
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• pp.165-170
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• 1990

In order to determine the relationship between dwarf gene and GA$_3$ response, three dwarf cultivars, Fukei 71, Seolak, and Tanginbozu, which were known to have d 50, d 47 and d 35 gene, respectively, were used as parents in this study. Three parents and their F$_1$ and F$_2$ generations were grown. Tillers of each plant were devided into two parts at 15 days after transplanting and was transplanted. One part of them was sprayed with GA$_3$ 50 ppm at booting stage. The internode length were measured at ripening stage in terms of GA$_3$ response. The internode was significantly elongated in Seolak and Tanginbozu, but not in Fukei 71. All F$_1$ plants of the crosses were tall, and their internode and culm were significantly elongated with the spraying of GA$_3$. Dwarf plants which are not responded to GA$_3$ were selected in the F$_2$'s of Seolak/Fukei 71 and Fukei 71/Tanginbozu crosses, and backcrossed to Fukei 71. All of these BC$_1$F$_1$ plants were uniform in the culm length and not responded to GA$_3$ treatment. The dwarf gene, d 50 of Fukei 71 seems to be closely associated with the facter of non-response to GA$_3$.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.669-673
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• 2008

In this study, the new methodology which combines Kohonen self-organizing map(KSOM) neural networks model and the conventional neural networks models such as feedforward neural networks model and generalized neural networks model is introduced to forecast flood stage in Nakdong river, Republic of Korea. It is possible to train without output data in KSOM neural networks model. KSOM neural networks model is used to classify the input data before it combines with the conventional neural networks model. Four types of models such as SOM-FFNNM-BP, SOM-GRNNM-GA, FFNNM-BP, and GRNNM-GA are used to train and test performances respectively. From the statistical analysis for training and testing performances, SOM-GRNNM-GA shows the best results compared with the other models such as SOM-FFNNM-BP, FFNNM-BP, and GRNNM-GA and FFNNM-BP shows vice-versa. From this study, we can suggest the new methodology to forecast flood stage and construct flood warning system in river basin.

• Current Applied Physics
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• v.18 no.12
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• pp.1558-1563
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• 2018

We demonstrate improved surface pit and phase separation in thick InGaN grown on a GaN/Si (111) substrate, using plasma-assisted molecular beam epitaxy with an indium modulation technique. The formation of surface pit and compositional inhomogeneity in the InGaN epilayer are investigated using atomic force microscopy, scanning electron microscopy and temperature-dependent photoluminescence. Indium elemental mapping directly reveals that poor compositional homogeneity occurs near the pits. The indium-modulation epitaxy of InGaN minimizes the surface indium segregation, leading to the reduction in pit density and size. The phase separation in InGaN with a higher pit density is significantly suppressed, suggesting that the pit formation and the phase separation are correlated. We propose an indium migration model for the correlation between surface pit and phase separation in InGaN.

• Journal of the Korean Magnetics Society
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• v.14 no.6
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• pp.213-218
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• 2004

Be-codoped GaMnAs layers were systematically grown via molecular beam epitaxy with varying Mn- and Be-flux. Mn flux was controlled to cover from solid solution type GaMnAs to precipitated GaMnAs. Two Be flux were chosen to exhibit semiconducting and metallic resistivity in the grown layers. The structural, electrical, and magnetic properties of GaAs:(Mn, Be) were investigated. The lightly Be-codoped GaMnAs layers showed ferromagnetism at room temperature, but did not reveal magnetotransport due to small magneto-resistance and high resistance of the matrix. However, room temperature magnetotransport could be observed in the degenerate Be-codoped GaMnAs layers, and which was assisted by the high conductivity of the matrix. The Be-codoping has promoted segregation of new ferromagnetic phase of MnGa as well as MnAs.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.216-216
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• 2012

The purpose of this work is to investigate a back surface field (BSF) on variety wafer resistivity for industrial crystalline silicon solar cells. As pointed out in this manuscript, doping a crucible grown Cz Si ingot with Ga offers a sure way of eliminating the light induced degradation (LID) because the LID defect is composed of B and O complex. However, the low segregation coefficient of Ga in Si causes a much wider resistivity variation along the Ga doped Cz Si ingot. Because of the resistivity variation the Cz Si wafer from different locations has different performance as know. In the light of B doped wafer, we made wider resistivity in Si ingot; we investigated the how resistivities work on the solar cells performance as a BSF quality.

• Korean Journal of Materials Research
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• v.9 no.5
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• pp.515-519
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• 1999

We have investigated the photoreflectance characteristics for In\ulcornerGaAs/GaAs heterojunction structure grown by molecular beam epitaxy (MBE). The E\ulcorner bandgap energy of In\ulcornerGa\ulcornerAs at room temperature was observed at about 1.3 eV. From this result, the indium composition x value was calculated. The shoulder peaks were observed higher than E\ulcorner peaks, and peak positions were shifted toward 12 meV to 70 meV higher energy with increasing doping concentrations. The shoulder peaks can be observed by In segregation and re-evaporation. However, we think that indium re-evaporation cause th shift of shoulder peaks after epilayer growth.