• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.12
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• pp.888-893
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• 2013

In this paper, we prepared $Cu(In,Ga)Se_2$ thin films by using co-evaporation method, and analyzed the properties of the thin films. During the thin film preparation process, we confirmed $InGaSe_2$ phase was formed at $400^{\circ}C$ in first stage, and also confirmed the thin films showed the vacancy decrease. In second and third stage, we confirmed the density increase of crystalline structure at over $480^{\circ}C$ and the formation of $Cu(In_{0.7}Ga_{0.3})Se_2$ phase. As the result of SEM and XRD analysis of the films which were before and after heat-treated, we confirmed the disappearance of $Cu_2Se_2$ and the formation of $Cu(In_{0.7}Ga_{0.3})Se_2$ single phase after the heat-treatment, We, therefore, confirmed the heat-treatment did not affect the absorbency spectra of the thin films.

• Transactions on Electrical and Electronic Materials
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• v.4 no.6
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• pp.13-16
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• 2003

Mn-doped $ZnGa_{2}O_{4}$:$Mn^{2+}$ (M=S, Se) thin film phosphors have been grown using a pulsed laser deposition technique under various growth conditions. The structural characterization carr~ed out on a series of $ZnGa_{2}O_{4}$:$Mn^{2+}$ (M=S, Se) films grown on MgO(l00) substrates usmg Zn-rich ceramic targets. Oxygen pressure was varied from 50 to 200 mTorr and Zn/Ga ratio was the function of oxygen pressure. XRD patterns showed that the lattice constants of the $ZnGa_{2}O_{4}$:$Mn^{2+}$ (M=S, Se) thin film decrease with the substitution of sulfur and selenium for the oxygen in the $ZnGa_2O_4$. Measurements of photoluminescence (PL) properties of $ZnGa_{2}O_{4}$:$Mn^{2+}$ (M=S, Se) thin films have indicated that MgO(100) is one of the most promised substrates for the growth of high quality $ZnGa_2O_{4-x}M_{x}$:$Mn^{2+}$ (M=S, Se) thin films. In particular, the incorporation of Sulfur or Selenium into $ZnGa_2O_4$ lattice could induce a remarkable increase in the intensity of PL. The increasing of green emission intensity was observed with $ZnGa_2O_{3.925}Se_{0.075}:$Mn^{2+}$ and $ZnGa_2O_{3.925}S_{0.05}$:$Mn^{2+}$ films, whose brightness was increased by a factor of 3.1 and 1.4 in comparison with that of $ZnGa_{2}O_{4}$:$Mn^{2+}$ films, respectively. These phosphors may promise for application to the flat panel displays.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.375-375
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• 2011

Cu(In1-xGax)Se2 (CIGS)박막증착법 중 금속 전구체의 셀렌화 공정법은 다른 제조 방법에 비해 대면적 생산에 유리하고, 비교적 공정 과정이 간단하다는 장점이 있다. 이 제조 방법은 금속 전구체를 만든 후에 셀렌화 공정을 하게 된다. 셀렌화 공정은 대부분 H2Se 가스를 사용하지만 유독성으로 사용하는데 주의해야 한다. 본 실험은 H2Se를 사용하지 않고 Se원료를 주입하기 위해 Se cracker를 사용했고 금속 전구체 증착과 셀렌화를 동시에 하는 반응성 스퍼터링 후 열처리 법을 이용하여 CIGS 박막을 증착 했다. CIGS의 박막의 Cu/[In+Ga], Ga/[In+Ga]비를 변화시켜 특성변화를 관찰했다. Cu/[In+Ga]비가 감소할수록 CIGS의 결정방향인 (112) 이 우세하게 발달했고 Ga/[In+Ga]비가 증가할수록 CIGS의 결정면 사이의 값이 작아지기 때문에 CIGS peak의 2-Theta 값이 증가하게 된다. CIGS 박막 태양전지의 구조는 Al/Ni/ITO/i-ZnO/CdS/CIGS/Mo/glass 제작했다. CIGS박막의 조성비가 Cu/[In+Ga]=0.84, Ga/[In+Ga]=0.24인 박막태양전지에서 개방전압 0.48 V, 단락전류밀도 33.54 mA/cm2, 충실도 54.20% 그리고 변환효율 8.63%를 얻었다.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.289-290
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• 2006

We report a study of Zn(S)Se/GaAs heterojunction solar cells grown by molecular beam epitaxy (MBE). Zn(S)Se/GaAs heterostructures prepared under different conditions were characterized in-situ by reflection high-energy electron diffraction (RHEED). Structural and electrical properties were investigated with double crystal X-ray diffraction and current-voltage characteristics, respectively. The fabricated $n-ZnS_{0.07}Se_{0.93}/p-GaAs$ solar cell (SC #2) exhibited open circuit voltage($V_{oc}$) of 0.37 V, short circuit current($I_{sc}$) of $1.7{\times}10^{-2}$ mA, fill factor of 0.62 and conversion efficiency of 7.8 % under 38.5 $mW/cm^2$ illumination.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.1
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• pp.1-5
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• 2000

Optical and electrical properties of GaSe:Er\ulcorner single crystals grown by the Bridgenman technique have been investigated by using optical absorption and h\Hall-effect measurement system. The Hall coefficients were mea-sured by using a high impedance electrometer in the temperature range from 360K to 150K. The temperature dependence of hole concentration show the characteristic of a partially compensated p-type semiconductor. Carrier density(N\ulcorner) of GaSe doped with Erbium was measured about 3.25$\times$10\ulcorner [cm\ulcorner] at temperature 300K, which was higher than undoped specimen. Photon energy gap (E\ulcorner) of GaSe:Er\ulcorner specimen was measured about 1.79eV.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.6
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• pp.252-259
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• 2005

Single crystal $CuGaSe_2$ layers were grown on thoroughly etched semi-insulating CaAs(100) substrate at $450^{\circ}C$ with hot wall epitaxy (HWE) system by evaporating $CuGaSe_2$ source at $610^{\circ}C$. The crystalline structure of the single crystal thin films was investigated by the photoluminescence (PL) and double crystal X-ray diffraction (DCXD). The carrier density and mobility of single crystal $CuGaSe_2$ thin films measured with Hall effect by Van der Pauw method are $4.87{\times}10^{17}cm^{-3}$ and $129cm^2/V{\cdot}s$ 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, $E_g(T)=1.7998eV-(8.7489{\times}10^{-4}eV/K)T^2/(T+335K)$. The voltage, current density of maxiumun power, fill factor, and conversion, efficiency of $n-CdS/p-CuGaSe_2$, heterojunction solar cells under $80mW/cm^2$ illumination were found to be 0.41 V, $21.8mA/cm^2$, 0.75 and 11.17%, respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.2
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• pp.52-56
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• 2007

We have installed an ultra high vacuum (UHV) molecular beam epitaxy (MBE) system and investigated into the characteristics of MBE-grown ZnSe/GaAs [001] using scanning electron microscopy (SEM), atomic force microscopy (AFM), we confirmed that layer's surface was dense and uniform of molecular layer. We used x-ray diffractometer (XRD) and confirmed two peaks correspond to GaAs [001] substrate and ZnSe epilayer, respectively. We observed photoluminescence (PL) peak approximately at 437 nm and measured PL mapping of 2 inch ZnSe epilayer.

• Korean Journal of Materials Research
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• v.21 no.8
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• pp.461-467
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• 2011

Cu(In, Ga)$Se_2$ (CIGS) precursor films were electrodeposited on Mo/glass substrates in acidic solutions containing $Cu^{2+}$, $In^{3+}$, $Ga^{3+}$, and $Se^{4+}$ ions at -0.6 V (SCE) and pH. 1.8. In order to induce recrystallization, the electrodeposited $Cu_{1.00}In_{0.81}Ga_{0.09}Se_{2.08}$ (25.0 at.% Cu + 20.2 at.% In + 2.2 at.% Ga + 52.0 at.% Se) precursor films were annealed under a high Se gas atmosphere for 15, 30, 45, and 60 min, respectively, at $500^{\circ}C$. The Se amount in the film increased from 52 at.% to 62 at.%, whereas the In amount in the film decreased from 20.8 at.% to 9.1 at.% as the annealing time increased from 0 (asdeposited state) to 60 min. These results were attributed to the Se introduced from the furnace atmosphere and reacted with the In present in the precursor films, resulting in the formation of the volatile $In_2Se$. CIGS precursor grains with a cauliflower shape grew as larger grains with the $CuSe_2$ and/or $Cu_{2-x}Se$ faceted phases as the annealing times increased. These faceted phases resulted in rough surface morphologies of the CIGS films. Furthermore, the CIGS layers were not dense because the empty spaces between the grains were not removed via annealing. Uniform thicknesses of the $MoSe_2$ layers occurred at the 45 and 60 min annealing time. This implies that there was a stable reaction between the Mo back electrode and the Se diffused through the CIGS film. The results obtained in the present research were sufficiently different from comparable studies where the recrystallization annealing was performed under an atmosphere of Ar gas only or a low Se gas pressure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.124-125
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• 2007

Single crystal $CdGa_2Se_4$ layers were grown on a thoroughly etched semi-insulating GaAs(100) substrate at $420^{\circ}C$ with the hot wall epitaxy (HWE) system by evaporating the polycrystal source of $CdGa_2Se_4$ at $630^{\circ}C$ prepared from horizontal electric furnace. The photocurrent and the absorption spectra of $CdGa_2Se_4$/SI(Semi-Insulated) GaAs(100) are measured ranging from 293K to 10K. 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, $E_g$(T) = 2.6400 eV - $(7.721{\times}10^{-4}\;eV/K)T^2$/(T + 399 K). Using the photocurrent spectra and the Hopfield quasicubic model, the crystal field energy$({\Delta}cr)$ and the spin-orbit splitting energy$({\Delta}so)$ for the valence band of the $CdGa_2Se_4$ have been estimated to be 106.5 meV and 418.9 meV at 10 K, respectively. The three photocurrent peaks observed at 10 K are ascribed to the $A_{1^-},\;B_{1^-},\;and\;C_{11^-}$ exciton peaks.

• Korean Journal of Materials Research
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• v.15 no.10
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• pp.657-661
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• 2005

[ $ZnHgGa_4Se_8\;and\;ZnHgGa_4Se_8::Co^{2+}$ ] single crystals were grown by the Bridgman-Stockbarger method. The single crystals crystallized into a defect chalcopyrite structure. The optical energy band gap of the single crystals was investigated in the temperature range 11-300K. The optical energy band gap of the $ZnHgGa_4Se_8:Co^{2+}$ single crystal was smaller than that of the $ZnHgGa_4Se_8$ single crystal. The temperature dependence of the optical energy band gap of the single crystals was well fitted by the Varshni equqtion. The impurity optical absorption spectrum of the $ZnHgGa_4Se_8:Co^{2+}$ single crystal was measured in the wavelength region 300-2300 m at 80 K. Impurity absorption peaks in the spectrum were analyzed within the framework of the crystal field theory and were attributed to the electron transitions between the energy levels of $Co^{2+}$ sited in the Td symmetry point.