• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04b
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• pp.42-45
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• 2004

High quality CdTe single crystal for the solar cell fabrication was grown by vertical Bridgman method. The etch pits patterns of {111}surfaces of CdTe etched by Nakagawa solution was observed the {111} A composed of Cd atoms with typical triangle etch pits of pyramid mode. From the photoluminescence measurement on {111}A, we observed free exciton($E_x$) existing only higy quality crystal and neytral acceptor bound exciton($A^0$,X) having very strong peak intensity. Then, the full width at half maximum and binding energy of neutral acceptor bound exciton were 7 meV and 5.9 meV, respectively. By Haynes rule, an actibation energy of impurity was 59 meV. Therefore, the origins on impurity level acting as a neutral acceptor were associated Ag or Cu elements.

• Korean Journal of Metals and Materials
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• v.49 no.10
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• pp.818-822
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• 2011

ZnO nanorods were grown on Au-coated Si substrates by vapor phase transport (VPT) at the growth temperature of $600^{\circ}C$ using a mixture of zinc oxide and graphite powders as source material. Au thin films with the thickness of 5 nm were deposited by ion sputtering. Temperature-dependent photoluminescence (PL) was carried out to investigate the optical properties of the ZnO nanorods. Five peaks at 3.363, 3.327, 3.296, 3.228, and 3.143 eV, corresponding to the free exciton (FX), neutral donor bound exciton ($D^{\circ}X$), first order longitudinal optical phonon replica of free exciton (FX-1LO), FX-2LO, and FX-3LO emissions, were obtained at low-temperature (10 K). The intensity of these peaks decreased and their position was red shifted with the increase in the temperature. The FX emission peak energy of the ZnO nanorods exhibited an anomalous behavior (red-blue-red shift) with the increase in temperature. This is also known as an "S-shaped" emission shift. The thermal activation energy for the exciton with increasing temperature in the ZnO nanorods is found to be about 26.6 meV; the values of Varshni's empirical equation fitting parameters are = $5{\times}10^{-4}eV/K$, ${\beta}=350K$, and $E_g(0)=3.364eV$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.4
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• pp.202-209
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• 2002

The stochiometric mix of evaporating materials for the $CuInSe_2$single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, $CuInSe_2$compound crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $620^{\circ}C$ and $410^{\circ}C$, 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 $CuInSe_2$single crystal thin films measured from Hall effect by van der Pauw method. From the photocurrent spectrum by illumination of perpendicular light on the c-axis of the $CuInSe_2$single crystal thin film, we have found that the values of spin orbit splitting $\Delta$So and the crystal field splitting $\Delta$Cr. From the photoluminescence measurement on $CuInSe_2$single crystal thin film, we observed free exciton ($E_x$) existing only high quality crystal and neutral bound exciton ($A^{\circ}$, X) having very strong peak intensity. Then, the full-width-at-half-maximum (FWHM) and binding energy of neutral donor bound exciton were 7 meV and 5.9 meV, respectivity. By haynes rule, an activation energy of impurity was 59 meV.

• Journal of the Korean Vacuum Society
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• v.8 no.3B
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• pp.297-301
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• 1999

High quality CdTe single crystal for the solar cell fabrication was grown by vertical Bridgman method. The etch pits patterns of {111} surfaces of CdTe etched by Nakagawa solution was observed the {11} A composed of Cd atoms with typical triangle etch pits of pyramid mode. From the photoluminescence measurement of {111} A, we observed free exciton $(E_x)$ existing only high quality crystal and neutral acceptor bound exciton ($A^{\circ}$, X) having very strong peak intensity. Then, the full width at half maximum and binding energy of neutral acceptor bound exciton were 7 meV and 5.9 meV, respectively. By Haynes rule, and activation energy of impurity was 59meV. Therefore, the origins on impurity level acting as a neutral acceptor were associated Ag or Cu elements.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.3
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• pp.196-200
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• 2019

In this study, photoluminescence (PL) analysis was performed to evaluate the optical properties of commercial ZnO substrates. Particular attention was paid to the bound exciton (BX) luminescence, which is usually the strongest emission intensity of commercial substrates. At 15 K, PL analysis revealed that the BX peak due to donor-type impurities (donor-bound-exciton; DX) dominated, while two-electron satellite (TES) emission, donor-accepter pair (DAP) emission, and LO-phonon replica emission were also observed. The impurity concentration of the ZnO substrate was determined to be $10^{15}$ to $10^{16}/cm^3$ by examination of the temperature variation of DAP, while the half width and intensity change of the luminescence revealed that the temperature change of BX can be interpreted almost the same as the analysis of free-exciton emission.

• Journal of Photoscience
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• v.7 no.1
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• pp.27-30
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• 2000

The Photoluminescence (PL) measurement results of a very good quality GaN sample grown by metalorganic chemical vapor deposition (MOCVD) are reported. The temperature dependences of peak position, emission intensity, and the full width at half maximum (FWHM) of free-exciton (FX) A and B are presented. Our results show the fast thermal quenching of FX transition intensities and predominantly acoustic phonon scattering of emission line broadening. The transition-energy-shift following the Varshni's empirical equation, and by using it to fit the data, E$\_$A1/(T) = 3.4861 eV -6.046 $\times$ 10$\^$-4/T$^2$ (620.3+ T) eV, E$\_$B1/(T) = 3.4928 eV -4.777 $\times$ 10$\^$-4/T$^2$ / (408.2+ T) eV and E$\_$A2/ = 3.4991 eV -4.426 $\times$ 10$\^$-4/ T$^2$ / (430.6+ T) eV for A(n=1), B(n=1), and A(n=2) are obtained respectively.

• Journal of Surface Science and Engineering
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• v.35 no.5
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• pp.305-311
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• 2002

Optical measurements have been used to study the biaxial tensile strain in heteroeptaxial ZnTe epilayers on the (100) GaAs substrate by hot wall epitaxy (HWE) with Zn reservoir. It is effect on the low-temperature photoluminescence spectrum of the material. Optimum growth condition has been determined by a four-crystal rocking curve (FCRC) and a low temperature photoluminescence measurement (PL). It was found that Zn partial pressure from Zn reservoir has a strong influence on the quality of grown films. Under the determined optimum growth condition, ZnTe epitaxial films with thickness of 0.72~24.8$\mu\textrm{m}$ were grown for studying the effect of the thickness on crystalline quality. The PL and FCRC results indicated that the quality of ZnTe films becomes higher rapidly with increase of thickness up to 6$\mu\textrm{m}$. The best value of the FWHM of the four crystal rocking curve, 66 arcsec, was obtained on the film with 12$\mu\textrm{m}$ in thickness. The PL spectrum shows the splitted strong free exciton emissions and very weak deep band emissions. These results show the high quality of films.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.158-158
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• 2003

수평 전기로에서 CuGaTe2 다결정을 합성하여 HWE 방법으로 CuGaTe2 단결정 박막을 반절연성 GaAs(100) 위에 성장하였다. CuGaTe2 단결정 박막은 증발원과 기판의 온도를 각각 67$0^{\circ}C$, 41$0^{\circ}C$로 성장하였다. 이때 단결정 박막의 결정성이 10K에서 측정한 광발광 스펙트럼은 954.5nm (1.2989eV) 근처에서 exciton emission 스펙트럼이 가장 강하게 나타났으며, 또한 이중결정 X-선 요동곡선(DCRC)의 반폭치(FWHM)도 139arcsec로 가장 작게 측정되어 최적 성장 조건임을 알 수 있었다. Hall 효과는 van der Paw방법에 의해 측정되었으며, 온도에 의존하는 운반자 농도와 이동도는 293K에서 각각 8.72$\times$$10^{23}$개/㎥, 3.42$\times$$10^{-2}$$m^2$/V.s였다. 상온에서 CuGaTe2 단결정 박막의 광흡수 특성으로부터 에너지 띠간격이 1.22 eV였다 Band edge에 해당하는 광전도도peak의 온도 의존성은 Varshni 관계식으로 설명되었으며, Varshni 관계식의 상수값은 Eg(0) = 1.3982 eV, $\alpha$= 4.27$\times$$10^{-4}$ eV/K, $\beta$= 265.5 K로 주어졌다. CuGaTe2 단결정 박막의 광전류 단파장대 봉우리들로부터 10K에서 측정된 $\Delta$cr (crystal Field splitting)은 0.0791eV, $\Delta$s.o (spin orbit coupling)는 0.2463eV였다. 10K에서 광발광 봉우리의 919.8nm (1.3479eV)는 free exciton(Ex), 954.5nm (1.2989eV)는 donor-bound exciton 인 I2(DO,X)와 959.5nm (1.2921eV)는 acceptor-bound exciton 인 I1(AO,X) 이고, 964.6nm(1.2853eV)는 donor-acceptor pair(DAP) 발광, 1341.9nm (0.9239eV)는 self activated(SA)에 기인하는 광발광 봉우리로 고찰되었다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.156-156
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• 2003

수평 전기로에서 ZnIn$_2$S$_4$ 다결정을 합성하여 HWE(Hot Wall Epitaxy)방법으로 2nIn2S4단결정 박막을 반절연성 GaAs(100)기판 위에 성장시켰다. ZnIn2S4 단결정 박막은 증발원의 온도를 610 $^{\circ}C$, 기판의 온도를 450 $^{\circ}C$로 성장시켰고 성장 속도는 0.5 $\mu\textrm{m}$/hr로 확인되었다. ZrIn2S4 단결정 박막의 결정성의 조사에서 10 K에서 광발광(photoluminescence) 스펙트럼이 433 nm (2.8633eV)에서 exciton emission스펙트럼이 가장 강하게 나타났으며, 또한 이중결정 X-선 요동곡선(DCRC)의 반폭치(FWHM)도 133 arcsec로 가장 작아 최적 성장 조건임을 알 수 있었다. Hall 효과는 van der Pauw방법에 의해 측정되었으며, 온도에 의존하는 운반자 농도와 이동도는 293K에서 각각 8.51$\times$$10^{17}$ electron/$cm^{-3}$ 291 $\textrm{cm}^2$/v-s였다. ZnIn2S4 단결정 박막의 광전류 단파장대 봉우리들로부터 10 K에서 측정된 $\Delta$Cr(crystal field splitting)은 0.1678 eV, $\Delta$So(spin orbit coupling)는 0.0148 eV였다. 10 K의 광발광 측정으로부터 고품질의 결정에서 볼 수 있는 free exciton 과 매우 강한 세기의 중성 주개 bound exciton등의 피크가 관찰되었다. 이때 중성 주개 bound exciton의 반치폭과 결합 에너지는 각각 9 meV와 26 meV 였다. 또한 Haynes rule에 의해 구한 불순물의 활성화 에너지는 130 meV 였다.다.

• Transactions on Electrical and Electronic Materials
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• v.8 no.5
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• pp.191-195
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• 2007

We investigated photoluminescence characteristics of ZnO nano needle-like rods grown on a c-plane $AL_2O_3$ substrate by the hot wall epitaxy method. The nano-rods were vertically well aligned along the ZnO c-axis. The diameters of the ZnO nano-rods ranged from 20 nm to 30 nm and their lengths were between 600 and 700 nm. In the photoluminescence spectrum at 10 K, the exciton emission bound to the neutral donor dominated while defect related emission was weakly observed. With a further increase of temperature, the free exciton emission appeared and eventually became dominant at room temperature.