• Journal of the Optical Society of Korea
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• 제19권6호
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• pp.687-694
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• 2015

A photoluminescence (PL) imaging method using a vision camera was employed to inspect InGaN/GaN quantum-well light-emitting diode (LED) epi-wafers. The PL image revealed dark spot defective regions (DSDRs) as well as a spatial map of integrated PL intensity of the epi-wafer. The Shockley-Read-Hall (SRH) nonradiative recombination coefficient increased with the size of the DSDRs. The high nonradiative recombination rates of the DSDRs resulted in degradation of the optical properties of the LED chips fabricated at the defective regions. Abnormal current-voltage characteristics with large forward leakages were also observed for LED chips with DSDRs, which could be due to parallel resistances bypassing the junction and/or tunneling through defects in the active region. It was found that the SRH nonradiative recombination process was dominant in the voltage range where the forward leakage by tunneling was observed. The results indicated that the DSDRs observed by PL imaging of LED epi-wafers were high density SRH nonradiative recombination centers which could affect the optical and electrical properties of the LED chips, and PL imaging can be an inspection method for evaluation of the epi-wafers and estimation of properties of the LED chips before fabrication.

• 한국전기전자재료학회논문지
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• 제25권5호
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• pp.349-352
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• 2012

ZnO thin films were deposited on a-, c- and m- plane oriented 4H-SiC substrates by pulsed laser deposition. ZnO nanowires were formed on substrates by tube furnace. Shape and density of the ZnO nanowires were investigated by field emission scanning electron microscope. Average surface roughness and root mean square surface roughness were measure by atomic force microscope. Optical properties were investigated by Photoluminescence measurement. Density of ZnO nanowires grown on a-, c- and m-plane oriented 4H-SiC substrates were 17.89 ${\mu}m^{-2}$, 9.98 ${\mu}m^{-2}$ and 2.61 ${\mu}m^{-2}$, respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.1033-1036
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• 2004

Si nanocrystallites thin films on p-type (100) Si substrate have been fabricated by pulsed laser deposition using a Nd:YAG laser. After deposition, samples were annealed at the temperatures of 400 to $800^{\circ}C$. Hydrogen passivation was then performed in the forming gas (95% $N_2$ + 5% $H_2$) for 1 hr. Strong violet-indigo photoluminescence has been observed at room temperature from nitrogen ambient-annealed Si nanocrystallites. The variation of photoluminescence (PL) Properties of Si nanocrystallites thin films has been investigated depending on annealing temperatures with hydrogen passivation. From the results of PL, Fourier transform infrared (FTIR), and high-resolution transmission electron microscopy (HRTEM) measurements, it is observed that the origin of violet-indigo PL from the nanocrystalline silicon in the silicon oxide film is related to the quantum size effect of Si nanocrystallites and oxygen vacancies in the SiOx(x : 1.6-1.8) matrix affects the emission intensity.

• 반도체디스플레이기술학회지
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• 제15권2호
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• pp.49-54
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• 2016

$SrAl_{12}O_{19}:Ce_x{^{3+}}$,$Eu_{0.01}{^{2+}}$ phosphors were synthesized through a combustion process and their optical properties were investigated using time-resolved photoluminescence. A PL spectrum showed two dominant peaks which appeared at 300 and 410 nm. It is seen that, as the $Ce^{3+}$ concentration increases, the intensity of 300 nm decreases and the intensity of 410 nm increases. This behavior has been explained by two independent energy transfer mechanism. The first energy transfer occurs from $Ce^{3+}$ ion to $Eu^{3+}$ ion. The second energy transfer takes place from $Ce^{3+}$ ion to $Ce^{3+}-O_{ME}$ complex created in the magnetoplumbite structural host materials. The blue emitting 410 nm peak has been explained by both energy transfer mechanisms.

• 한국광학회지
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• 제3권3호
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• pp.183-190
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• 1992

$Al_x/Ga_{1-x}$ /As/AlAs GaAs 계로 이루어진 비대칭 이중 양자우물 구조의 광학적 특성을 photoluminescence, photoluminescence excitation, time-resolved photoluminescence를 통하여 조사하였다. 양자장벽 AlAs의 두께에 따른 특성 변화를 조사하기 위하여 두께를 15$\AA$., 150$\AA$로 제작하였다. 양자장벽이 15$\AA$인 경우 매우 빠른 전자의 관통 현상을 보여 주었으며, 이로 인해 $Al_x/Ga_{1-x}$As의 여기자 재결합에 해당하는 피크가 관찰되지 않았다. AlAs 양자장벽이 150$\AA$인 경우에는 $Al_x/Ga_{1-x}$As양자우물에서 여기자 재결합에 의한 피크가 50ps 이하로 빠른 decay시간을 보여 주었으며 이것은 양자장벽과의 $\Gamma$-X전이에 의한 것으로 사료되었다. GaAs양자우물에서의 luminescence decay는 두 시료 모두 1ns정도 이었으나, 15$\AA$인 경우에는 약 100ps의 rise시간이 존재하였으며 이것은 정공의 관통에 의한 시간으로 판명되었다.

• 한국재료학회지
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• 제32권10호
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• pp.419-424
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• 2022

Halide perovskite solar cells (PSCs) have improved rapidly over the past few years, and research on the optoelectrical properties of halide perovskite thin films has grown as well. Among the characterization techniques, photoluminescence (PL), a method of collecting emitted photons to evaluate the properties of materials, is widely applied to evaluate improvements in the performance of PSCs. However, since only photons emitted from the film in the escape cone are included, the photons collected in PL are a small fraction of the total photons emitted from the film. Unlike PSCs power conversion efficiency, PL measuring methods have not been standardized, and have been evaluated in a variety of ways. Thus, an in-depth study is needed of the methods used to evaluate materials using PL spectra. In this study, we examined the PL spectra of the perovskite light harvesting layer with different measurement protocols and analyzed the features. As the incident angle changed, different spectra were observed, indicating that the PL emission spectrum can depend on the measuring method, not the material. We found the intensity and energy of the PL spectra changes were due to the path of the emitted photons. Also, we found that the PL of halide perovskite thin films generally contains limited information. To solve this problem, the emitted photons should be collected using an integrating sphere. The results of this study suggest that the emission spectrum of halide perovskite films should be carefully interpreted in accordance with PL measuring method, since PL data is mostly affected by the method.

• Journal of Photoscience
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• 제5권4호
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• pp.153-155
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• 1998

The optical spectroscopic properties of the ordered perovskite structure A2BWO6 doped with Eu3+ have been studied. The experimental result about Eu3+ ordering in the system of A2BWO6 indicate the different structural conditions. Some influence of Eu3+ substitutioin on the different types of cation site have been investigated.

• 한국재료학회지
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• 제16권3호
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• pp.183-187
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• 2006

We present the effects of rapid thermal annealing (RTA) temperature on the structural and optical properties of self-assembled InAs quantum dot (QD) structures grown on GaAs substrates by molecular beam epitaxy (MBE). The photoluminescence (PL) measurements are performed in a closed-cycle refrigerator as a function of temperature for the unannealed and annealed samples. RTA at higher temperature results in the increase in island size, the corresponding decrease in the density of islands, and the redshift in the PL emission from the islands. The temperature dependence of the PL peak energy for the InAs QDs is well expressed by the Varshni equation. The thermal quenching activation energies for the samples unannealed and annealed at $600^{\circ}C$ are found to be $25{\pm}5meV$ and $47{\pm}5$ meV, respectively.

• Transactions on Electrical and Electronic Materials
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• 제14권5호
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• pp.263-267
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• 2013

New random copolymers of phenylsilyl- and alkoxy-substituted phenylenevinylene, DMPS(9)-MEH(1)-PPV, DMPS(5)- MEH(5)-PPV and DMPS(1)-MEH(9)-PPV, have been synthesized by the Gilch dehydrohalogenation route, and the light-emitting properties of these polymers have been studied. The synthesized polymers were completely soluble in common organic solvents, and exhibited good thermal stability, almost up to $380^{\circ}C$. They showed UV-visible absorbance and photoluminescence (PL) in the ranges of 422-510 and 513-590 nm, respectively, according to their feed ratios. Electroluminescent devices were fabricated with these polymers as emitting layers, and ITO and Al as anode and cathode, respectively. DMPS(1)-MEH(9)-PPV, DMPS(5)-MEH(5)-PPV and DMPS(9)-MEH(1)-PPV exhibited EL emission maxima at 575 nm, 565 nm, and 541 nm, respectively.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.1523-1525
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• 2005

$CaZrO_3:Tb$ as a new green-emitting phosphor, has been synthesized by solid state reaction. Photoluminescence and cathodoluminescence properties for the phosphor with a Perovskite structure were investigated. The $CaZrO_3:Tb$ phosphor, which has several emission peaks due to energy transfer from $^5D_4$ to $^7F_J(J=6,5,4,3)$ of $Tb^{3+}$ ion, exhibited strong green luminescence with the main emission peak centered at 545 nm. Optimum Tb concentration was 0.02mol%.