• 한국태양에너지학회 논문집
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• 제23권2호
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• pp.59-70
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• 2003

A stoichiometric mixture of evaporating materials for $CuGaSe_2$ single crystal thin films was prepared from horizontal electric furnace. Using extrapolation method of X-ray diffraction patterns for the polycrystal $CuGaSe_2$, it was found tetragonal structure whose lattice constant $a_0$ and $c_0$ were $5.615{\AA}$ and $11.025{\AA}$, respectively. To obtain the single crystal thin films, $CuGaSe_2$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the hot wall epitaxy (HWE) system. The source and substrate temperatures were $610^{\circ}C$ and $450^{\circ}C$, respectively. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of $CuGaSe_2$ single crystal thin films measured with Hall effect by van der Pauw method are $5.01\times10^{17}cm^{-3}$ and $245cm^2/V{\cdot}s$ at 293K. respectively. The temperature dependence of the energy band gap of the $CuGaSe_2$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g$(T)=1.7998 eV-($8.7489\times10^{-4}$ eV/K)$T^2$/(T+335K). After the as-grown $CuGaSe_2$ single crystal thin films was annealed in Cu-, Se-, and Ga-atmospheres, the origin of point defects of $CuGaSe_2$ single crystal thin films has been investigated by the photoluminescence(PL) at 10 K. The native defects of $V_{CU},\;V_{Se},\;Cu_{int}$ and $Se_{int}$ obtained by PL measurements were classified as a donors or acceptors type. And we concluded that the heat-treatment in the Cu-atmosphere converted $CuGaSe_2$ single crystal thin films to an optical n-type. Also, we confirmed that Ga in $CuGaSe_2$/GaAs did not form the native defects because Ga in $CuGaSe_2$ single crystal thin films existed in the form of stable bonds.

• 한국진공학회지
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• 제7권1호
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• pp.11-16
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• 1998

본 연구에서는 GaAs의 selenium보호막형성 효과를 관찰하기 위하여 $Na_2$Se/NH$_4$OH 용액을 제조하고 X-선 광전자 분광기(X-ray photoelectron spectroscopy)와 photoluminescence(PL)를 이용하여 표면처리된 GaAs의 처리직후 및 대기중 노출에 따른 화학적 결합특성 및 광학적 특성을 관찰하였다. 용액처리 직후, 표면에는 As-Se결합이 형성 되었으며 Se는 한가지 산화상태인 -2가로 존재함이 관찰되었다. 또한 세정처리후의 표면보 다 Se용액처리 이후에 PL의 피이크 세기가 크게 증가됨으로부터 Se 용액처리가 GaAs의 표면상태밀도를 효과적으로 감소시킬 수 있음을 확인할 수 있었다. 그러나 처리 직후 공기 중 노출없이 관찰한 GaAs표면에서 산화막이 국부적으로 관찰되었으며 이렇게 처리과정중 생성된 산화막은 대기중 노출에 따라 산화막 성장을 유도하고 표면처리 효과를 저하시키는 주요인으로 작용함을 알 수 있었다. 이는 Se용액처리된 GaAs표면의 PL강도가 대기중 노출 에 따라 감소하며 세정처리후 GaAs표면의 PL강도와 유사한 값을 나타냄으로 부터도 확인 할 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.352-356
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• 2003

A stoichiometric mixture of evaporating materials for $CuGaSe_2$ single crystal am films was prepared from horizontal electric furnace. Using extrapolation method of X-ray diffraction patterns for the polycrystal $CuGaSe_2$, it was found tetragonal structure whose lattice constant $a_0$ and $c_0$ were $5.615\;{\AA}\;and\;11.025\;{\AA}$, respectively. To obtain the single crystal thin films, $CuGaSe_2$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the hot wall epitaxy (HWE) system. The source and substrate temperatures were $610^{\circ}C$ and $450^{\circ}C$, respectively, The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of $CuGaSe_2$ single crystal thin films measured with Hall effect by van der Pauw method are $9.24{\times}10^{16}\;cm^{-3}$ and $295\;cm^2/V{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the $CuGaSe_2$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)\;:\;1.7998\;eV\;-\;(8.7489\;{\times}\;10^{-4}\;eV/K)T^2(T\;+\;335\;K)$. After the as-grown $CuGaSe_2$ single crystal thin films was annealed in Cu-, Se-, and Ga-atmospheres, the origin of point defects of $CuGaSe_2$ single crystal thin films has been investigated by the photoluminescence(PL) at 10 K. The native defects of $V_{CU}$, $V_{Se}$, $CU_{int}$, and $Se_{int}$, obtained by PL measurements were classified as a donors or accepters type. And we concluded that the heat-treatment in the Cu-atmosphere converted $CuGaSe_2$ single crystal thin films to an optical n-type. Also, we confirmed that Ga in $CuGaSe_2/GaAs$ did not form the native defects because Ga in $CuGaSe_2$ single crystal thin films existed in the form of stable bonds.

• 한국진공학회지
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• 제1권2호
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• pp.254-258
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• 1992

Iodine 화학수송법으로 성장한 Ni-doped CdGa2Se4와 undoped CdGa2Se4 단결정 의 PL 및 PLE 스펙트럼을 조사하였다. Undoped CdGa2Se4 단결정의 PL 스펙트럼에서는 전도대아래 준 연속적으로 분포된 electron trap과 deep level, 그리고 가전자대 위 0.07eV, 0.12eV에 있는 acceptor level 사이의 전자전이에 의한 2개의 emission band를 2.13eV와 1.20eV 영역에서 관측하였으며, Ni-doped 단결정에서는 Ni2+ 이온의 여기상태 3T1(3P)와 바 닥상태 3T1(3F) 사이의 전자전이에 의한 emission band를 1.48eV 영역에서 관측하였다. 이 러한 결과로부터 제안된 CdGa2Se4의 energy band model은 본 연구의 PL mechanism을 설명하는데 가능함을 보여주었다.

• 한국진공학회지
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• 제3권3호
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• pp.346-354
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• 1994

삼원화합물 반도체 CuAlSe2 및 CuGaSe2 단결정의 solid solution 인 CuAl1-xGaxSe2 및 cobalt를 2.0 mol% 첨가한 CuAl1-xGaxSe2 : Co2+ 단결정을 iodine을 수송물질로 사용한 화학수송법으로 성장시켰 다. source material로는 CuAl1-xGaxSe2 의 화학조성비에서 Se를 3.0mol% 과잉으로 첨가하여 합성한 ingot를 사용하였으며 불순물이 첨가된 CuAl1-xGaxSe2:Co2+ 단결정성장시에는 source ma-terial 에 cobalt 분말을 2.0mol% 첨가하였다. X-선 회절무늬로부터 성장된 단결정들이 chalcopyrite 결정구조를 하고 있음을 확인하였으며 격자상수를 구하였다. 광흡수 spectra 측정으로부터 성장된 단결정에서 나타 는 cobalt 불순물에 의한 광흡수 peak가 Td 대칭점에위치한 Co2+ 이온의 에너지 준위들간 전자전이에 의해 나타남을 규명하였다.

• Journal of Magnetics
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• 제12권2호
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• pp.59-63
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• 2007

Ferromagnet/Semiconductor heterostructures have attracted much attention because of their potential applications in spintronic devices. We investigated the electronic structures and magnetism of monolayer Fe on $CuGaSe_2(001)$ by using the all-electron full-potential linearized augmented plane-wave method within a generalized gradient approximation. We considered the monolayer Fe deposited on both the CuGa atoms terminated (CuGa-Term) and the Se atom terminated (Se-Term) surfaces of $CuGaSe_2(001)$. The calculated magnetic moment of the Fe atom on the CuGa-Term was about $2.90\;{{\mu}_B}$. Those of the Fe atoms on the Se-Term were in the range of $2.85-2.98\;{{\mu}_B}$. The different magnetic behaviors of the Fe atoms on two different surfaces were discussed using the calculated layer-projected density of states.

• Current Photovoltaic Research
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• 제1권1호
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• pp.38-43
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• 2013

$Cu(In,Ga)_3Se_5$ is a candidate material for the top cell of $Cu(In,Ga)Se_2$ tandem cells. This phase is often found at the surface of the $Cu(In,Ga)Se_2$ film during $Cu(In,Ga)Se_2$ cell fabrication, and plays a positive role in $Cu(In,Ga)Se_2$ cell performance. However, the exact properties of the $Cu(In,Ga)_3Se_5$ film have not been extensively studied yet. In this work, $Cu(In,Ga)_3Se_5$ films were fabricated on Mo-coated soda-lime glass substrates by a three-stage co-evaporation process. The Cu content in the film was controlled by varying the deposition time of each stage. X-ray diffraction and Raman spectroscopy analyses showed that, even though the stoichiometric Cu/(In+Ga) ratio is 0.25, $Cu(In,Ga)_3Se_5$ is easily formed in a wide range of Cu content as long as the Cu/(In+Ga) ratio is held below 0.5. The optical band gap of $Cu_{0.3}(In_{0.65}Ga_{0.35})_3Se_5$ composition was found to be 1.35eV. As the Cu/(In+Ga) ratio was decreased further below 0.5, the grain size became smaller and the band gap increased. Unlike the $Cu(In,Ga)Se_2$ solar cell, an external supply of Na with $Na_2S$ deposition further increased the cell efficiency of the $Cu(In,Ga)_3Se_5$ solar cell, indicating that more Na is necessary, in addition to the Na supply from the soda lime glass, to suppress deep level defects in the $Cu(In,Ga)_3Se_5$ film. The cell efficiency of $CdS/Cu(In,Ga)_3Se_5$ was improved from 8.8 to 11.2% by incorporating Na with $Na_2S$ deposition on the CIGS film. The fill factor was significantly improved by the Na incorporation, due to a decrease of deep-level defects.

• 한국전기전자재료학회논문지
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• 제20권10호
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• pp.829-838
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• 2007

The stochiometric mix of evaporating materials for the $CdGa_2Se_4$ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, $CdGa_2Se_4$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $630^{\circ}C$ and $420^{\circ}C$, respectively. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD).The carrier density and mobility of $CdGa_2Se_4$ single crystal thin films measured from Hall effect by van der Pauw method are $8.27{\times}10^{17}\;cm^{-3},\;345\;cm^2/V{\cdot}s$ at 293 K. respectively. The temperature dependence of the energy band gap of the $CdGa_2Se_4$ obtained from the absorption spectra was well described by the Varshni's relation, $Eg(T)\;=\;2.6400\;eV\;-\;(7.721{\times}10^{-4}\;eV/K)T^2/(T+399\;K)$. After the as-grown single crystal $CdGa_2Se_4$ thin films were annealed in Cd-, Se-, and Ga -atmospheres, the origin of point defects of single crystal $CdGa_2Se_4$ thin films has been investigated by PL at 10 K. The native defects of $V_{Cd}$, $V_{Se}$, $Cd_{int}$, and $Se_{int}$ obtained by PL measurements were classified as donors or accepters. We concluded that the heat-treatment in the Cd-atmosphere converted single crystal $CdGa_2Se_4$ thin films to an optical p-type. Also, we confirmed that Ga in $CdGa_2Se_4/GaAs$ did not form the native defects because Ga in single crystal $CdGa_2Se_4$ thin films existed in the form of stable bonds.

• 센서학회지
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• 제23권1호
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• pp.51-57
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• 2014

The evaporating materials for $MgGa_2Se_4$ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, $MgGa_2Se_4$ compounded polycrystal powder was deposited on thoroughly etched semi-insulated GaAs(100) substrate by the hot wall epitaxy (HWE) method system. The source and substrate temperatures of optimized growth conditions, were $610^{\circ}C$ and $400^{\circ}C$, respectively.The source and substrate temperatures were $610^{\circ}C$ and $400^{\circ}C$, respectively. The crystalline structure of the single crystal thin films was investigated by double crystal X-ray diffraction (DCXD). The temperature dependence of the energy band gap of the $MgGa_2Se_4$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=2.34\;eV-(8.81{\times}10^{-4}\;eV/K)T^2/(T+251\;K)$. After the as-grown $MgGa_2Se_4$ single crystal thin films was annealed in Mg-, Se-, and Ga-atmospheres, the origin of point defects of $MgGa_2Se_4$ single crystal thin films has been investigated by the photoluminescence (PL) at 10 K. The native defects of $V_{Mg}$, $V_{Se}$ obtained by PL measurements were classified as a donors or acceptors type. And we concluded that the heat-treatment in the Se-atmosphere converted $MgGa_2Se_4$ single crystal thin films to an optical n-type. Also, we confirmed that Ga in $MgGa_2Se_4$/GaAs did not form the native defects because Ga in $MgGa_2Se_4$ single crystal thin films existed in the form of stable bonds.

• 한국결정성장학회지
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• 제17권5호
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• pp.179-186
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• 2007

[ $CdGa_2Se_4$ ] 단결정 박막을 수평 전기로에서 합성한 $CdGa_2Se_4$ 다결정을 증발원으로하여, hot wall epitaxy(HWE) 방법으로 증발원과 기판(반절연성-GaAs(100))의 온도를 각각 $630^{\circ}C,\;420^{\circ}C$로 고정하여 성장하였다. 이때 단결정 박막의 결정성은 광발광 스펙트럼과 이중결정 X-선 요동곡선(DCRC)으로 부터 구하였다. Hall 효과는 van der Pauw 방법에 의해 측정되었으며, 293K에서 운반자 농도와 이동도는 각각 $8.27{\times}10^{17}cm^{-3},\;345cm^2/V{\cdot}s$였다. $CdGa_2Se_4/SI$(Semi-Insulated) GaAs(100) 단결정 박막의 광흡수와 광전류 spectra를 293K에서 10K까지 측정하였다. 광흡수 스펙트럼으로부터 band gap $E_g(T)$는 Varshni 공식에 따라 계산한 결과 $E_g(T)=2.6400eV-(7.721{\times}10^{-4}eV/K)T^2/(T+399K)$였다. 광전류 스펙트럼으로부터 Hamilton matrix(Hopfield quasicubic mode)법으로 계산한 결과 crystal field splitting 에너지 ${\Delta}cr$값이 106.5meV이며 spinorbit 에너지 ${\Delta}so$값은 418.9meV임을 확인하였다. 10K일 때 광전류 세 봉우리들은 $A_{1^-},\;B_{1^-}$와 $C_{11}-exciton$ 봉우리임을 알았다.