• 통합자연과학논문집
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• 제2권4호
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• pp.265-269
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• 2009

The photoluminescence was measured in GaAs-AlGaAs double-quantum-well structure at high magnetic field. Although the phototransition characteristics displayed a free-particle transition at low magnetic field, the change of free-particle transition into bound-exciton transition was observed at high magnetic field (above 10 T). A charged exciton formation due to charge-unbalanced electron-hole was identified by using a spin-polarized photoluminescence method. An increase of exciton formation due to the localization of free-particle at magnetic field was observed according to the increase of magnetic field.

• 센서학회지
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• 제14권6호
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• pp.369-373
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• 2005

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 compesed 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 high quality crystal and neutal 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 activation enery of impurity was 59 meV. Therefore, the origins on impurity level acting as a neutral acceptor were associated Ag or Cu elements.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.119-119
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• 2010

We report strong exciton transition and exciton-phonon couplings in photoluminescence (PL) of ZnO thin films grown on MgO/sapphire (buffer/substrate) by plasma-assisted molecular beam epitaxy. The PL spectra at 10 K showed the intensity of the dominant emission, donor-bound exciton transition of front surface (top surface, the latter part in growth) is found to be about 100 times higher than that of back surface (in-depth bottom area, the initial part), while the room temperature PL spectra showed dominant contributions from the free exciton emissions and phonon-replicas of free excitons for front surface and back surface, respectively, It could be attributed to the strong contributions of exciton-phonon coupling. Time resolved PL spectra reveal that the life time of exciton recombination from the front surface are longer than those from back surface. This is most probably due to the fact that reduction of non-radiative recombination in the front surface. This investigation indicates that the existence of native defects or trap centers which can be reduced by the proper initial condition in growth and the exciton-phonon interaction couplings play an important role in optical properties and crystal quality of ZnO thin films.

• Nuclear Engineering and Technology
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• 제6권1호
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• pp.9-13
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• 1974

80$^{\circ}$K에서 카드미움설파이드 단결정에 펄스형 전자빔을 쪼였을 때 자연적으로 방출되는 빛의 스펙트럼을 파장의 함수로 측정하였다 측정된 스펙트럼으로부터 중성도너에 묶일 엑사이톤의 분리에너지가 2.0meV였으며, 계산치는 2.4-3.2meV였다. 이 중성도너에 구속된 엑사이톤과 세로방향 광학 음향양자와는 상호작용을 하지 않으며 분리된 자유엑사이톤과 상호작용을 한다는 결론을 얻었다. 그러므로 상호작용으로 구성되는 스펙트럼의 원점은 중성도너로부터 분리된 자유엑사이톤의 스펙트럼의 위치에 있게 되며 또한 스펙트럼의 분석으로부터 카드미움설파이드의 세로방향 광학음향양자 에너지는 40.SmeV로 밝혀졌다.

• 한국결정성장학회지
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• 제10권3호
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• pp.185-188
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• 2000

CdTe 단결정에서 중성 받게에 구속된 엑시톤 해리를 PL 스펙트럼의 온도의존성을 측정하여 조사하였다. 12 K에서 CdTe 단결정의 자유 엑시톤의 결합 에너지는 10 meV이고,중성받게에 구속된 결합 에너지는 7.17 meV 이며, 또 중성주게에 구속된 결합 에너지는 14 meV이였다. 또한 ($A^{\circ}$, X)의 활성화 에너지의 값으로부터($A^{\circ}$, X)의 해리는 자유 엑시톤에서 해리됨을 알 수 있었다.

• 한국결정성장학회지
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• 제13권3호
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• pp.127-131
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• 2003

Zincblende 구조를 갖는 양질의 ZnTe(100) 박막을 $CaAs(100\pm2^{\circ})$ 기판에 HWE법으로 성장하였다 기판온도에 따른 표면상태와 성장률 그리고 결정성의 변화를 관측하였고, 기판온도가 $470^{\circ}C$일 때 결정성이 가장 우수하였다. 10K 광발광 측정으로부터 열적 인장스트레인에 의하여 분리된 가벼운 양공과 무거운 양공을 관측하였고 이들의 일차 들뜬상태를 관측하였다 무거운 양공의 자유 엑시톤의 이중구조는 엑시톤-폴라리톤 결합에 의한 세로방향 엑시톤과 가로방향 엑시톤 사이의 에너지 차이 때문이다.

• 한국전기전자재료학회논문지
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• 제26권2호
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• pp.83-86
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• 2013

The optical properties of ZnO thin film have been studied using photoluminescence(PL) spectroscopy with the change of sample temperatures from 10 K to 290 K. The spectrum at 10 K showed the characteristic emission lines of ZnO which were as follows: free exciton(FX) at 3.369 eV, neutral donor-bound exciton($D^0X$) at 3.360 eV, two electron satellite(TES) at 3.332 eV, $D^0X$-1LO at 3.289 eV, and donor-acceptor pair(DAP) transiton at 3.217 eV. From the spectral evolution with temperatures, two features could be identified as temperature went higher: (1) the bound excitons changed gradually into free excitons, (2) DAP turned into free electron-acceptor transition(e,$A^0$). The PL intensity of free exciton increased with the increase of temperatures, which was accompanied by the decrease of the intensity of bound excitions and bound excition-related transitons such as TES and $D^0X$-1LO. At 80 K DAP transition disappeared, while (e,$A^0$) transition started to appear at 30 K.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.45-45
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• 2009

우리는 ZnO Template를 사용한 열기상법을 이용하여 수직 배양한 ZnO nanorods와 ZnO Nanopencils를 성장하였고, Dependency temperature Photoluminescence(PL)의 분석을 통하여 광학적 특성에 대해 분석을 하였다. ZnO 나노구조는 100K 이하의 온도에서 donor-bound exciton가 dominant하고, 100K 이상의 온도에서는 free exciton과 그들의 phonon-replica emission이 dominant한 것을 알 수 있었다. 하지만, ZnO nanorods와 nanopencils은 다른 exciton-phonon coupling의 strength에 의한 surface defects에 의해 excitonic emissions의 다른 거동을 보이는 것을 알았다. 이것으로 인해 상온 PL에서 ZnO nanopencil은 nanorods에 비해 52meV의 red shift를 보였다.

• Journal of Korean Vacuum Science & Technology
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• 제4권3호
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• pp.63-67
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• 2000

We have studied the photoluminescence properties of undoped epitaxial layers of GaN on sapphire substrate grown by horizontal low pressure metal organic chemical vapor deposition method in the temperature range of 9-300 K. At 9 K the spectra are dominated by the well resolved interband free excitons A and B as well as bound excitons. Temperature dependence of free exciton transitions was studied and Varshni's coefficients for the temperature variation of bandgap were determined.

• 한국전기전자재료학회논문지
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• 제28권1호
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• pp.17-20
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• 2015

The physical effects of H-plasma treatment on ZnO thin film have been studied using photoluminescence(PL) spectroscopy. Four characteristic peaks have been identified: (i) $D^0X$ peak (neutral donor-bound exciton), showing relatively small integrated intensity after H-plasma treatment, indicates that H-plasma passivates the neutral donors in ZnO at low temperatures. The rapid decrease in the integrated intensity of the peak as the temperature goes up is considered to be due to the ionization of neutral donors. (ii) H-related complex-bound exciton peak appears at the low temperatures (10 K~80 K) after H-plasma treatment, showing the same thermal evolution as $D^0X$ peak. (iii) FX (free exciton) peak starts to show up at 60 K and grows more and more as the temperature goes up, which is considered to be related to the increase in free electron concentration in the film. (iv) violet band is intensified after H-plasma, which means more defects and impurities are generated by H-plasma process.