• Journal of the Korea Convergence Society
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• v.6 no.2
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• pp.49-55
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• 2015

Quantum dot technology can be complementary application of the bulk material, and that a wide range of applications that can take advantage of the characteristic convergence technology. With the development of quantum dot technology, it is important to analyze Marketability of quantum technology, business opportunity. In this study, patents, papers, market, analysis of the project will be to investigate the quantum information research trends. Research results are expected to be used as a basis for research and development path setting and strategic planning of the quantum dot. In particular, this study found the performance of quantum dot research through patents and papers analyzed. In addition, fast-growing field, the field to lead the commercialization were derived. Compared to the advanced research and national research was to diagnose the domestic research into quantum dots.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.93-93
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• 1999

양자점(Quantum dot : QD)를 이용한 소자를 만들기 위해서는 수직방향으로의 적층이 필수적이다. 양자점의 적층은 수직적으로 같은 위치에 정렬하므로, 고려되어야 할 요소로는 양자점간의 파동함수의 중첩(coupling)에 의한 특성변화, 적층의 진행에 따른 변형(strain)의 증가로 기인되는 volcano 모양으로 나타나는 결함등이 있다. 이러한 결함은 nonradiative recombination center로 작용하여 오히려 효율이 떨어지게 되는 현상이 발생하게 되므로 본 연구에서는 적층횟수에 따른 발광효율의 변화를 조사하여 소자응용에 적절한 적층 조건을 조사하였다. 시료성장은 molecular beam epitaxy (MBE) 장치를 이용하여 GAs(100) 기판위에 GaAs buffer를 58$0^{\circ}C$에서 150nm 성장후 InAs/GaAs 양자점과 50$0^{\circ}C$에서 적층회수 1, 3, 6, 10, 15, 20회로 하였으며 적층성장 이후 GaAs cap layer를 성장하였다. GaAs spacing과 cap layer의 성장온도 역시 50$0^{\circ}C$이며 시료의 분석은 photoluminescence (PL)과 scanning transmission electron microscope (STEM)으로 하였다. 적층횟수를 바꾸어 시료를 성장하기 전에 적층횟수를 10회로 고정하고 spacing 두께를 2.8nm, 5.6nm, 11.2nm로 바꾸어 성장하여 PL 특성을 관찰하여본 결과 spacing이 2.8nm인 경우 수직적으로 정렬된 양자점 간에 coupling이 매우 커서 single layer QD의 PL peak에 비해 약 100nm 정도 파장이 증가하였고, spacing의 두께가 11.2nm 일 경우는 single layer QD와 거의 같은 파장의 빛을 방출하여 중첩이 거의 일어나지 않지만 두꺼운 spacing때문에 PL세기가 감소하였다. 한편, 적층회수에 따른 광학적 특성을 PL로 조사하여 본 결과 peak 파장은 적층횟수가 1회에서 3회로 증가했을 때는 blue shift 하다가 이후 적층이 증가함에 따라 red shift 하였다. 그리고 10층 이상의 적층에서는 excited state에서 기인된 peak이 검출되었다. 이렇나 원인은 적층수가 증가함에 따라 carrier life time이 증가하여 exciter state에 carrier가 존재할 확률이 증가하기 때문으로 생각된다. 또한 PL 세기가 다소 증가하다가 10층 이상의 경우는 다시 감소함을 알 수 있었다. 반치폭도 3층과 6층에서 가장 적은 값을 보였다. 이와 같은 결과는 결함생성과 관련하여 STEM 분석으로 해석되어질 수 있는데 6층 적층시는 양자점이 수직적으로 정렬되어 잘 형성됨을 관찰할 수 있었고 적층에 따른 크기 변화도 거의 나타나지 않았다. 그러나 10층 15층 적층시 몇가지 결함이 형성됨을 볼수 있었고 양자점의 정렬도 완전하게 이루어지지 않음을 볼 수 있었다. 그러므로 수직적층된 InAs 양자점의 광학적 특성은 성장조건에 따른 결함생성과 밀접한 관련이 있으며 상세한 논의가 이루어질 것이다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.3
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• pp.351-359
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• 1996

We have investigated the effect of hydrogen plasma on the formation of InAs QDs (quantum dots) structure by using a CBE (chemical beam epitaxy)system equipped with ECR (electron cyclotron resonance) plasma source. It is confirmed that the formation of self-organized InAs-QDs on GaAs is started after the growth of InAs layer up to 2.6 ML (monolayer) with the irradiation of hydrogen plasma while it is started after 1.9 ML without hydrogen gas and hydrogen plasma through the observation of RHEED patterns. Density and size of the QDs formed at $T_{sub}=370^{\circ}C$ are $1.9{\times}10^{11}cm^{-2}$ and 17.7 nm without hydrogen plasma, and $1.3{\times}10^{11}cm^{-2}$ and 19.4 nm with hydrogen plasma, respectively. It is also observed from the PL(photoluminescence) measurement on InAs-QDs that red shift in PL peak energy and broadening in FWHM (full width at half maximum)of PL peak caused by the effects of hydrogen plasma on the increment of size and its distribution. These effects of hydrogen plasma are considered as a act of atomic hydrogen which enhances the layer-growth of InAs on GaAs resulted from the relief of misfit strain between GaAs substrate and InAs.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.268-268
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• 2011

GaAs (001) 기판에 MBE를 이용하여 자발형성법으로 성장한 InAs 양자점(QDs: quantum dots)의 광학적 특성을 PL (photoluminescence)과 TRPL (time-resolved PL)을 이용하여 분석하였다. InAs 양자점 성장 동안 In 공급은 계속하면서 As 공급을 주기적으로 차단과 공급을 반복하면서 성장하였다. As 차단과 공급을 1초, 2초, 그리고 3초씩 하면서 InAs 양자점을 성장하였다. 기준시료는 In과 As 공급을 중단하지 않고 20초 동안 성장하였다. As interruption mode로 성장한 시료들의 QD density는 기준시료에 비해 증가하였으며, size distribution도 기준시료에 비해 향상되었다. 기준시료와 비교하였을 때, As interruption mode로 성장한 시료들의 PL 피크는 적색이동 (red-shift)를 보였으며, PL 세기는 2배 이상 증가하였다. PL 소멸곡선은 파장이 증가함에 따라 점차 느려지다가 PL 피크에서 가장 느린 소멸을 보인 후 다시 점차 빠르게 소멸하였다. 시료의 온도를 10 K에서 60 K까지 증가하였을 때 PL 피크 에너지는 변하지 않았으며, PL 소멸시간은 서서히 증가함을 보였다. 온도를 더 증가하였을 때 PL 피크 에너지는 적색이동 하였으며 PL 소멸시간도 빠르게 감소함을 보였다. As interruption mode로 성장한 양자점 시료의 구조적 특성 변화에 의한 광학적 특성 변화를 확인하였다.

• Korean Journal of Optics and Photonics
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• v.35 no.3
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• pp.95-106
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• 2024

In the 21st century, white light-emitting diodes (LEDs) are widely used as backlighting for liquid crystal displays and as a light source for general illumination. However, white LEDs used in lighting often use a single yellow phosphor on top of a blue LED chip, which lacks the ability to reproduce natural colors in objects under conventional illumination accurately. Recently, researchers have been actively working on realizing high color-rendering lighting by incorporating red quantum dots to improve the spectrum in the long-wavelength band, which is deficient in conventional white LEDs. In particular, how to develop and apply remote quantum dot components to ensure long-term reliability is currently under active research. This paper introduces recent research on remote quantum dot components and the current status of developing high color-rendering lightings with them. Especially, we focus on various factors that are important to consider in optimizing the optical structure of the quantum dot components and discuss the future directions and prospects of research for high color-rendering lighting technology.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.2
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• pp.78-81
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• 2020

Quantum dot efficiency was increased to evaluate reliability and optical characteristics using incidental materials. Quantum dot was manufactured by wrapping a sandwich type quantum layer using a product with a barrier property to prevent water and oxygen because it is vulnerable to oxygen and moisture. We used the three quantum dot films consisting of quantum dot only and quantum dot products consisting of film and barrier film combined with PET in the quantum dot product to evaluate the change over 650 hours under high temperature and high humidity conditions at 60℃ and 90 % humidity. As a result, the quantum dot product with Barrier Film has lowered luminance by 8 %, CIE x by 2 % and CIE y by 8 %. Quantum dot products exposed to moisture and oxygen were oxidized and measured low before measurement.

• Journal of the Korean Vacuum Society
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• v.18 no.5
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• pp.352-357
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• 2009

The InAs multi-quantum dots (MQDs) solar cell and InGaAs multi-quantum wells (MQWs) solar cell to cover 1.1 eV and 1.3 eV were designed by 1D poisson, respectively. The MQDs and MQWs of 5, 10, 15 layers were grown by molecular beam epitaxy. The photo luminescence results showed that the 5 period stacked MQDs have the highest intensity at around 1.1 eV with 57.6 meV full width at half maximum (FWHM). Also we can observe 10 period stacked MQWs peak position which has highest intensity at 1.31 eV with 12.37 meV FWHM. The density and size of QDs were observed by reflection high energy electron diffraction pattern and atomic force microscope. Futhermore, AlGaAs/GaAs sandwiched tunnel junctions were modified according to the width of GaAs layer on p-type GaAs substrates. The structures with GaAs width of 30 nm and 50 nm have backward diode characteristics. In contrast, tunnel diode characteristics were observed in the 20 nm of that of sample.

• Journal of the Korean Vacuum Society
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• v.22 no.2
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• pp.86-91
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• 2013

The optical properties of InAs quantum dots (QDs) grown on GaAs substrates grown by molecular beam epitaxy have been studied using photoluminescence (PL) and time-resolved PL measurements. InAs QDs were grown using an arsenic interruption growth (AIG) technique, in which the As flux was periodically interrupted by a closed As shutter during InAs QDs growth. In this study, the shutter of As source was periodically opened and closed for 1 (S1), 2 (S2), or 3 s (S3). For comparison, an InAs QD sample (S0) without As interruption was grown in a pure GaAs matrix for 20 s. The PL intensity of InAs QD samples grown by AIG technique is stronger than that of the reference sample (S0). While the PL peaks of S1 and S2 are redshifted compared to that of S0, the PL peak of S3 is blueshifted from that of S0. The increase of the PL intensity for the InAs QDs grown by AIG technique can be explained by the reduced InAs clusters, the increased QD density, the improved QD uniformity, and the improved aspect ratio (height/length). The redshift (blueshift) of the PL peak for S1 (S3) compared with that for S0 is attributed to the increase (decrease) in the QD average length compared to the average length of S0. The PL intensity, PL peak position, and PL decay time have been investigated as functions of temperature and emission wavelength. S2 shows no InAs clusters, the increased InAs QD density, the improved QD uniformity, and the improved QD aspect ratio. S2 also shows the strongest PL intensity and the longest PL decay time. These results indicate that the size (shape), density, and uniformity of InAs QDs can be controlled by using AIG technique. Therefore the emission wavelength and luminescence properties of InAs/GaAs QDs can also be controlled.

• Proceedings of the Korean Vacuum Society Conference
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• 2006.02a
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• pp.215-215
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• 2006

• Proceedings of the Korean Vacuum Society Conference
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• 2006.02a
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• pp.213-213
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• 2006