Hot wall epitaxy(HWE)법에 의한 $ZnIn_{2}Se_{4}$ 단결정 박막 성장과 가전자대 갈라짐에 대한 광전류 연구

홍광준,Hong, Kwang-Joon 한국결정성장학회 2008 韓國結晶成長學會誌 Vol.18 No.5

A stoichiometric mixture of evaporating materials for $ZnIn_2Se_4$ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, $ZnIn_2Se_4$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperatures were $630^{\circ}C$ and $400^{\circ}C$, 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 $ZnIn_2Se_4$ single crystal thin films measured from Hall effect by van der Pauw method are $9.41\times10^{16}cm^{-3}$ and $292cm^2/v{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the $ZnIn_2Se_4$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=1.8622eV-(5.23\times10^{-4}eV/K)T^2/(T+775.5K)$. The crystal field and the spin-orbit splitting energies for the valence band of the $ZnIn_2Se_4$ have been estimated to be 182.7 meV and 42.6 meV, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the ${\Delta}so$ definitely exists in the ${\Gamma}_5$ states of the valence band of the $ZnIn_2Se_4/GaAs$ epilayer. The three photo current peaks observed at 10 K are ascribed to the $A_{1}-$, $B_{1}-exciton$ for n = 1 and $C_{27}-exciton$ peaks for n = 27. 수평 전기로에서 $ZnIn_2Se_4$ 단결정을 합성하여 HWE(Hot Wall Epitaxy)방법으로 $ZnIn_2Se_4$ 단결정 박막을 반절연성 GaAs(100) 기판에 성장시켰다. $ZnIn_2Se_4$ 단결정 박막의 성장 조건을 증발원의 온도 $630^{\circ}C$, 기판의 온도 $400^{\circ}C$였고 성장 속도는 0.5 $\mu m/hr$였다. $ZnIn_2Se_4$ 단결정 박막의 결정성의 조사에서 10K에서 광발광(photoluminescence) 스펙트럼이 682.7nm ($1.816{\underline{1}}eV$)에서 exciton emission 스펙트럼이 가장 강하게 나타났으며, 또한 이중결정 X-선 요통곡선(DCRC)의 반폭치(FWHM)도 128 arcsec로 가장 작아 최적 성장 조건임을 알 수 있었다. Hall 효과는 van der Pauw 방법에 의해 측정되었으며, 온도에 의존하는 운반자 농노와 이동도는 293 K에서 각각 $9.41\times10^{16}/cm^{-3}$, $292cm^2/V{\cdot}s$였다. $ZnIn_2Se_4$/SI(Semi-Insulated) GaAs(100) 단결정 박막의 광흡수와 광전류 spectra를 293 K에서 10K까지 측정하였다. 광흡수 스펙트럼으로부터 band gap $E_g(T)$는 varshni공식에 따라 계산한 결과 $E_g(T)=1.8622\;eV-(5.23\times10^{-4}eV/K)T^2/(T+775.5K)$ 이었으며 광전류 스펙트럼으로부터 Hamilton matrix(Hopfield quasicubic mode)법으로 계산한 결과 crystal field splitting energy ${\Delta}cr$값이 182.7meV이며 spin-orbit energy ${\Delta} so$값은 42.6meV임을 확인하였다. 10 K일 때 광전류 봉우리들은 n= 1, 27일때 $A_{1}-$, $B_{1}-$와 $C_{27}-exciton$ 봉우리임을 알았다.

HWE(Hot Wall Epitaxy)에 의한 ZnIn_2S_4 박막 성장과 광전도 특성

홍광준,이관교,정준우,정경아,방진주,장현규,문종대,김혜숙 조선대학교 기초과학연구소 1999 自然科學硏究 Vol.22 No.1

HWE 방법에 의해 ZnIn_2S_4 박막을 Si(00) 기판 위에 성장시켰다. 증발원과 기판의 온도를 각각 610℃, 450℃로 하여 성장시킨 ZnIn_2S_4 박막의 이중 결정 X-선 요동곡선(DCRC)의 반폭치(FWHM)값이 245 arcsec로 가장 작았다. Van der Pauw 방법으로 Hall 효과를 측정하여 운반자농도의 1n n 대 1/T에서 구한 활성화에너지는 0.17eV로 측정되었다. Hall 이동도의 온도 의존성은 30K에서 100K까지는 불순물산란에 기인하고, 100K에서 293K까지는 격자산란에 기인한것으로 고찰되었다. 광전도셀의 특성으로 spectral response, 최대 허용소비전력(MAPD), 광전류와 암전류(pc/dc)의 비 및 응답시간을 측정하였다. S 증기분위기에서 열처리한 광전도 셀의 경우, 감도(??)는 0.99, pc/dc은 1.37x10^7, 그리고 최대 허용소비전력(MAPD)은 336mW, 오름시간(rise time)은 9ms, 내림시간(decay time)은 9.8ms로 가장 좋은 광전도 특성을 얻었다. The ZnIn_2S_4 thin films were grown on the Si(100) wafers by a hot wall epitaxy method(HWE). The source and substrate temperature are 610℃ and 450℃ respectively. The crystalline structure of epilayers was investigated by double crystal X-ray diffraction(DCXD). Hall effect on the sample was measured by the van der Pauw method and studied on the carrier density and mobility dependence on temperature. From Hall data, the mobility was increased in the temperature range 30K to 100K by impurity scattering and decreased in the temperature range 100K to 293K by the lattice scattering. In order to explore the applicability as a photoconductive cell, we measured the sensitivity(??), the ratio of photocurrent to darkcurrent(pc/dc), maximum allowable power dissipation(MAPD), spectral response and response time. The results indicated that the photoconductive characteristic were the best for the samples annealed in S vapor compare with in Zn, In, air and vacuum vapour. Then we obtained the sensitivity of 0.99, the value of pc/dc of 1.37x10^7, the MAPD of 336mW, and the rise and decay time of 9ms and 9.8ms, respectively.

Photoresponse-behavior Analysis of ZnAl<SUB>2</SUB>Se<SUB>4</SUB> Layers by Using Photocurrent Spectroscopy

홍광준,정태수,윤창주 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.4

The photocurrent (PC) variation of photoconductive ZnAl₂Se₄ layers was investigated as a function of temperature. Three PC peaks corresponding to band-to-band transitions were observed. From the relation between the temperature and the PC-peak position, the temperature-dependent band-gap energy E_g was well described by <i>E_g</i>(<i>T</i>) = <i>E_g</i>(0) - (1.94 × 10⁻³)<i>T</i>²/(468 + <i>T</i>). Also, <i>E_g</i>(0) was estimated to be 3.5268, 3.6148, and 3.7178 eV at the valence band states of Γ₄(z), Γ₅(x), and Γ₅(y), respectively. A characteristic splitting of the valence band governed by the selection rule was first observed through the method of PC spectroscopy. We noted that the crystal-field splitting and spin-orbit splitting were 0.088 eV and 0.103 eV, respectively. With decreasing temperature, however, the PC intensities decreased, contrary to our expectation. From the log <i>J</i>_ph <i>vs.</i> 1/<i>T</i> plot, a dominant level of 37.8 meV was observed in the high-temperature region. Thereby, we suggest that this trapping center due to native defects and impurities limits the PC response with decreasing temperature.

Hot wall epitaxy(HWE)법에 의한 ZnAl₂Se₄단결정 박막 성장과 광학적 특성

홍광준 한국물리학회 2011 새물리 Vol.61 No.8

A stoichiometric mixture of evaporating materials for ZnAl₂Se₄single crystal thin films was prepared in a horizontal electric furnace. The ZnAl₂Se₄ polycrystals had a defect chalcopyrite structure, with lattice constants _0= 5.5563Å, c_0 = 10.8897Å. To obtain a single-crystal thin film, We deposited mixed ZnAl₂Se₄ crystals on a thoroughly-etched semi-insulating GaAs(100) substrate by using a hot-wall epitaxy (HWE) system. The source and the substrate temperatures were 620℃and 400℃,respectively. The crystalline structure of the single-crystal thin film was investigated by using double-crystal X-ray rocking curves and X-ray diffraction ω-2Θ scans. The carrier density and the mobility of the ZnAl₂Se₄single-crystal thin film were 8.23×10^(16)cm^(-3) and 287m²/v‧s at 293K, respectively. To identify the band gap energy, We investigated the optical absorption spectra of the ZnAl₂Se₄single-crystal thin film in the temperature region of 10-293 K. The temperature dependence of the direct optical energy gap is well presented by the Varshni's relation, E_g(T) =E_g(0) -(αT²/T+β). The constants of Varshni's equation were E_g (0)= 3.5269 eV, α= 2.03×10^(-3) eV/K and β= 501.9 K for the ZnAl₂Se₄single-crystal thin film. 단결정 성장용 ZnAl₂Se₄ 다결정을 수평 전기로에서 합성하였으며,결정구조는 defect chalcopyrite이고 격자상수 α_0= 5.5563Å,c_0 = 10.8897Å이었다. ZnAl₂Se₄단결정 박막은 hot wall epitaxy (HWE) 방법으로 반절연성 GaAs(100)기판에 성장시켰다. MgGa₂Se₄단결정 박막의 성장 조건은 증발원의 온도 620℃, 기판의 온도 400℃였고 성장 속도는0.5㎛/hr였다. ZnAl₂Se₄ 단결정 박막의 결정성은 이중 결정X-선 회절곡선의 반치폭과 X-선 회절무늬의 ω-2Θ로부터구하여 최적 성장 조건을 알 수 있었다. Hall 효과는 van der Pauw 방법에 의해 측정되었으며, 온도에 의존하는 운반자 농도와 이동도는 293K에서 각각 8.23×10^(16)cm^(-3), 287m²/v‧s였다.ZnAl₂Se₄/SI (Semi-Insulated) GaAs(100)단결정 박막의 광흡수 스펙트럼을 10 K에서 293 K까지 측정하였다. 광흡수 스펙트럼으로부터 구한 에너지 간격 E_g(T)는 Varshni 관계식E_g(T) = E_g(0) -(αT²/T+β)을 잘 만족함을알 수 있었다. 이 때 E_g (0)= 3.5269 eV, α= 2.03×10^(-3) eV/K 그리고 β= 501.9 K 이었다.

HWE 방법에 의한 CdS 박막의 성장과 광전도 특성

홍광준 한국결정성장학회 1996 韓國結晶成長學會誌 Vol.6 No.3

HWE 방법으로 CdS 박막을 quartz plate 위에 성장하였다. CdS 박막을 성장할 때 증발원과 기판의 온도를 각각 $590^{\circ}C$, $400^{\circ}C$로 하였고 성장된 두께는 $2.5\;\mu\textrm{m}$였다. 성장된 CdS 박막의 X-선 회절 무늬로부터 외삽법에 의해 구한 a와 c는 각각 $4.137\;{\AA}$과 $6.713\;{\AA}$인 육방정계임을 알았다. Van der Pauw 방법으로 Hall 효과를 측정하여 운반자 농도와 이동도의 온도 의존성을 연구하였다. 이동도는 30 K에서 200 K까지는 piezoelectric 산란에 기인하고, 200 K에서 293 K까지는 polar optical 산란에 의하여 감소하였다. 광전도 셀의 특성으로 spectral response, 최대 허용 소비전력 (MAPD), 광전류와 암전류비 (pc/dc), 및 응답시간을 측정하였다. Cu 증기 분위기에서 열처리한 광전도 셀의 경우 ${\gamma}=0.99,\;pc/dc=9.42{\times}10^{6}$, MAPD : 318 mW, rise time 10 ms, decay time 9 ms로 가장 좋은 광전도 특성을 얻었다. The CdS thin films are grown on quartz plate by hot wall epitaxy. The source and substrate temperature is $590^{\circ}C$ and $400^{\circ}C$ respectively, and thickness of the film is $2.5\;\mu\textrm{m}$. Using extrapolation method of X-ray diffraction patterns for the CdS thin film, it was found hexagonal structure whose lattice constant a and c were $4.137\;{\AA}$ and $6.713\;{\AA}$, respectively. Hall effect on this sample was measured by the method of van der Pauw and studied on cattirer density and mobility depending on temperature. From hall data, the mobility was likely to be decreased by piezoelectric scattering in the temperature range 30 K to 200 K and by polar optical scattering in the temperature range 200 K to 293 K. In order to explore the applicability as a photoconductive cell we measured the sensitivity ($\gamma$), the ratio of photocurrent to darkcurrent (pc/dc), maximum allowable power dissipation (MAPD), spectral response and response time. The results indicated that for the samples annealed in Cu vapor the photoconductive characteristics are the best. Then we obtained the sensitivity of 0.99, the value of pc/dc of $9.42{\times}10^{6}$, the MAPD of 318 mW, and the rise and decay time of 10 ms and 9 ms, respectively.

Point-Defect Study of CuAlSe2(112) Layers Post-Annealed in Various Ambient

홍광준,윤창주,김혜숙,방진주,문종대,하종호,정태수 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.5I

High quality CuAlSe2(112)/GaAs(100) heteroepitaxial layers were grown by using the hot wall epitaxy method. The optical absorption measurement showed the temperature dependence of the energy band gap on the CuAlSe2 layer to be Eg(T) = 2.8382 eV . (8.68 × 10.4 eV/K)T2/(155 + T). After the as-grown CuAlSe2 layer was annealed in Cu, Se, and Al atmospheres, the origin of point defects in the CuAlSe2 layer were investigated by using photoluminescence (PL) at 10 K. Point defects originating from VCu, VSe, Cuint, and Seint were obtained from the PL measurements and were classified as a donor or acceptor types. These PL results also led us to confirm that the CuAlSe2 layer had obviously converted into an n-type after the Cu atmosphere treatment. Finally, we found that the Al in the CuAlSe2 layer did not form native defects because the Al existed in the form of stable bonds in the CuAlSe2 layer.or.

The temperature-dependent behavior of the photocurrent spectra of CdIn2S4 films

홍광준,Sukjin Yun,Jangbok Kim 한양대학교 세라믹연구소 2006 Journal of Ceramic Processing Research Vol.7 No.4

CdIn2S4 (110) films were grown on semi-insulating GaAs (100) by a hot wall epitaxy method. Using photocurrent (PC) measurements, the PC spectra in the temperature range of 30 to 10 K appeared as three peaks in the short wavelength region. It was found that three peaks, A-, B-, and C-excitons, correspond to the intrinsic transition from the valence band states of Γ4(z), Γ5(x), and Γ5(y) to the exciton below the conduction band state of Γ1(s), respectively. A 0.122 eV crystal field splitting and the 0.017 eV spin orbit splitting were obtained. Thus, the temperature dependence of the optical band gap obtained from the PC measurements was well described by Eg(T)=2.7116 eV−(7.65×10−4 eV/K)T2/(425+T). However, the behavior of the PC was different from that generally observed in other semiconductors. The PC intensities decreased with decreasing temperature. This phenomenon had ever been reported in a PC experiment on bulk crystals grown by the Bridgman method. From the relation of log Jph vs 1/T, where Jph is the PC density, two dominant levels were observed, one at high temperatures and the other at low temperatures. Consequently, the trapping centers due to native defects in the CdIn2S4 film were suggested to be the cause of the decrease in the PC signal with decreasing temperature. CdIn2S4 (110) films were grown on semi-insulating GaAs (100) by a hot wall epitaxy method. Using photocurrent (PC) measurements, the PC spectra in the temperature range of 30 to 10 K appeared as three peaks in the short wavelength region. It was found that three peaks, A-, B-, and C-excitons, correspond to the intrinsic transition from the valence band states of Γ4(z), Γ5(x), and Γ5(y) to the exciton below the conduction band state of Γ1(s), respectively. A 0.122 eV crystal field splitting and the 0.017 eV spin orbit splitting were obtained. Thus, the temperature dependence of the optical band gap obtained from the PC measurements was well described by Eg(T)=2.7116 eV−(7.65×10−4 eV/K)T2/(425+T). However, the behavior of the PC was different from that generally observed in other semiconductors. The PC intensities decreased with decreasing temperature. This phenomenon had ever been reported in a PC experiment on bulk crystals grown by the Bridgman method. From the relation of log Jph vs 1/T, where Jph is the PC density, two dominant levels were observed, one at high temperatures and the other at low temperatures. Consequently, the trapping centers due to native defects in the CdIn2S4 film were suggested to be the cause of the decrease in the PC signal with decreasing temperature.

Optoelectrical properties of ZnO thin films grown by pulsed laser deposition

홍광준,Changsun Park 한양대학교 세라믹연구소 2006 Journal of Ceramic Processing Research Vol.7 No.4

ZnO films on Al2O3 substrates were grown using a pulsed laser deposition method. Through photoluminescence (PL) and Xray diffraction (XRD) measurements, the optimum growth conditions for the ZnO growth were established. The results of the XRD measurements indicate that ZnO films were strongly oriented to the c-axis of the hexagonal structure and epitaxially crystallized under constraints created by the substrate. The full width half maximum for a theta curve of the (0002) peak was 0.201o. Also, from the PL measurements, the grown ZnO films were observed to give free exciton behaviour, which indicates a high quality of the epilayer. The Hall mobility and carrier density of the ZnO films at 293 K were estimated to be 299 cm2/ V s and 8.27×1016 cm−3, respectively. The absorption spectra revealed that the temperature dependence of the optical band gap on the ZnO films was Eg(T)=3.4393 eV−(5.30×10−4 eV/K)T2/(367+T). ZnO films on Al2O3 substrates were grown using a pulsed laser deposition method. Through photoluminescence (PL) and Xray diffraction (XRD) measurements, the optimum growth conditions for the ZnO growth were established. The results of the XRD measurements indicate that ZnO films were strongly oriented to the c-axis of the hexagonal structure and epitaxially crystallized under constraints created by the substrate. The full width half maximum for a theta curve of the (0002) peak was 0.201o. Also, from the PL measurements, the grown ZnO films were observed to give free exciton behaviour, which indicates a high quality of the epilayer. The Hall mobility and carrier density of the ZnO films at 293 K were estimated to be 299 cm2/ V s and 8.27×1016 cm−3, respectively. The absorption spectra revealed that the temperature dependence of the optical band gap on the ZnO films was Eg(T)=3.4393 eV−(5.30×10−4 eV/K)T2/(367+T).

Hot Wall Epitaxy (HWE)법에 의한 AgGa$Se_2$ 단결정 박막 성장과 특성

홍광준,이관교,박진성,Hong, Gwang-Jun,Lee, Gwan-Gyo,Park, Jin-Seong 한국재료학회 2001 한국재료학회지 Vol.11 No.5

AgGaSe$_2$ 단결정 박막은 수평 전기로에서 합성한 $AgGaSe_2$ 다결정을 증발원으로 하여, hot wall epitaxy (HWE) 방법으로 증발원과 기판 (반절연성-GaAs(100)) 의 온도를 각각 $630^{\circ}C$, $420^{\circ}C$로 고정하여 박막 결정 성장을 하였다. 10K에서 측정한 광발광 excition 스펙트럼과 이중결정 X-선 요동곡선 (DCRC) 의 반치폭 (FWHM )을 분석하여 단결정 박막의 최적 성장 조건을 얻었다. Hall효과는 van der Pauw 방법에 의해 측정되었으며, 온도에 의존하는 운반자 농도와 이동도는 293k에서 각각 4.89$\times$$10^{ 16}$/㎤, 129$\textrm{cm}^2$/V.s였다. 광전류 봉우리의 10K에서 단파장대의 가전자대 갈라짐 (splitting)에 의해서 측정된 $\Delta$C$_{r}$ (crystal field splitting)은 0.1762eV, $$\Delta$S_{o}$ (spin orbit splitting)는 0.2494eV였다 10K의 광발광 측정으로부터 고풍질의 결정에서 볼 수 있는 free excitors과 매우 강한 세기의 중성 주개 bound excitors등의 피크가 관찰되었다. 이때 중성 주개 bound ekciton의 반치폭과 결합에너지는 각각 BmeV와 14.1meV였다. 또한 Haynes rule에 의해 구한 불순물의 활성화 에너지는 141meV였다.rule에 의해 구한 불순물의 활성화 에너지는 141meV였다. The stochiometric $AgGaSe_2$ polycrystalline mixture of evaporating materials for the $AgGaSe_2$ single crystal thin film was prepared from horizontal furnace. To obtain the single crystal thin films, $AgGaSe_2$ mixed crystal and semi-insulating GaAs(100) wafer were used as source material and substrate for the Hot Wall Epitaxy (HWE) system, respectively. The source and substrate temperature were fixed at$ 630^{\circ}C$ and $420^{\circ}C$, respectively. The thickness of grown single crystal thin films is 2.1$\mu\textrm{m}$. The single crystal thin films were investigated by photoluminescence and double crystal X-ray diffraction(DCXD) measurement. The carrier density and mobility of AgGaSe$_2$ single crystal thin films measured from Hall effect by van der Pauw method are $4.89\Times10^{17}$ cm$^{-3}$ , 129cm2/V.s at 293K, respectively. From the Photocurrent spectrum by illumination of perpendicular light on the c-axis of the AgGaSe$_2$ single crystal thin film, we have found that the values of spin orbit splitting $$\Delta$S_{o}$ and the crystal field splitting $\Delta$C$_{r}$, were 0.1762eV and 0.2474eV at 10K, respectively. From the photoluminescence measurement of AgGaSe$_2$ single crystal thin film, we observed free excision (EX) observable only in high quality crystal and neutral bound exciton ($D^{o}$ , X) having very strong peak intensity. And, the full width at half maximum and binding energy of neutral donor bound excition were 8mev and 14.1meV, respectively. By Haynes rule, an activation energy of impurity was 141 meV.ion energy of impurity was 141 meV.

Hot Wall Epitaxy(HWE)법에 의한 CdIn₂S₄단결정 박막 성장과 점 결함 연구

홍광준,윤석진 경북대학교 센서기술연구소 2002 센서技術學術大會論文集 Vol.13 No.1