• Title, Summary, Keyword: QW (quantum well)

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Analysis on the Gain and the Differential Gain due to the Carrier Capture/Escape Process in a Quantum Well Laser (양자우물 레이저의 캐리어 포획 및 탈출에 따른 광 이득과 광 미분 이득 고찰)

  • 방성만;정재용;서정하
    • Journal of the Institute of Electronics Engineers of Korea TE
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    • v.37 no.5
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    • pp.17-27
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    • 2000
  • In a SCH(separate confinement heterostructure) QW(quantum well) laser, we calculated the optical gain, the differential gain and recombination current in the QW and derived the bulk carrier density in the SCH region as a function of the QW current by using the analytical capture escape model. Based upon above relations, we found the optical gain and the differential gain correspond to the ratios of carrier and current injected into the QW.

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Determination of temperature and flux variations during ultra-thin InGaN quantum well growth on a 2" wafer for GaN Green LED

  • Kim, Hyo-Jeong;Kim, Min-Ho;Jeong, Hun-Yeong;Lee, Hyeon-Hwi
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.149-149
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    • 2010
  • The origin of the inhomogeneous distribution of photoluminescence (PL) peak wavelength on a commercial 2" GaN wafer for green light emitting diode has been investigated by wide momentum transfer (Q) range x-ray diffraction (XRD) profile of InGaN/GaN multiple quantum wells. Near the GaN (0004) Bragg peak, wide-Q range XRD (${\Delta}Q$ > $1.4{\AA}-1$) was measured along the growth direction. Wide-Q XRD gives precise and direct information of ultra-thin InGaN quantum well structure. Based on the QW structural information, the variation of PL spectra can be explained by the combined effect of temperature gradient and slightly uneven flow of atomic sources during the QW growth. In narrow variations of indium composition and thickness of QW, an effective indium composition can be a good character to match structural data to PL spectra.

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Peak-to-zero modulation of optical absorption via electrically controllable quantum interference

  • Lee, Byoung-Ho;Kim, Kyoung-Youm
    • Journal of the Optical Society of Korea
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    • v.6 no.2
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    • pp.33-36
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    • 2002
  • We propose a modulation scheme of optical absorption in a coupled asymmetric quantum well (QW) structure via electrically controllable quantum interference. It is based on the parallel-perpendicular energy coupling effect. We show that by applying an external electric Held in the parallel direction (to the QW layers), we can obtain a maximum (peak-type) absorption at a specific wavelength where absorption cancellation would occur due to electrically induced transparency without such an external Held .

Optical properties of a-plane InGaN/GaN multi-quantum wells with green emission

  • Song, Hoo-Young;Kim, Eun-Kyu;Lee, Sung-Ho;Hwang, Sung-Min
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.172-172
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    • 2010
  • In the area of optoelectronic devices based on GaN and related ternary compounds, the two-dimensional system like as quantum wells (QWs) has been investigated as an effective structure for improving the light-emitting efficiency. Generally, the quantum well active regions in III-nitride light-emitting diodes grown on conventional c-plane sapphire substrates have critical problems given by the quantum confined Stark effect (QCSE) due to the effects of strong piezoelectric and spontaneous polarizations. However, the QWs grown on nonpolar templates are free from the QCSE since the polar-axis lies within the growth plane of the template. Also the unique characteristic of linear polarized light emission from nonpolar QW structures is attracting attentions because it is proper to the application of back-light units of liquid crystal display. In this study, we characterized optical properties of the a-plane InGaN/GaN QW structures by temperature-dependent photoluminescence (TDPL) measurements. From the photoluminescence (PL) spectrum measured at 300 K, green emission centered at 520 nm was observed for the QW region. Since indium incorporation on nonpolar QWs is lower than that on c-plane, this high indium-doping on a-plane InGaN QWs is not common. Therefore, the effect of high indium composition on optical properties in a-plane InGaN QWs will be extensively studied.

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Effect of Short Circuit Current Enhancement in Solar Cell by Quantum Well Structure and Quantitative Analysis of Elements Using Secondary Ion Mass Spectrometry (양자우물구조에 의한 태양전지 단락전류 증가 효과와 이차이온 질량분석법에 의한 원소 정량 분석)

  • Kim, Junghwan
    • Applied Chemistry for Engineering
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    • v.30 no.4
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    • pp.499-503
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    • 2019
  • Characteristics of solar cells employing a lattice matched GaInP/GaAs quantum well (QW) structure in a single N-AlGaInP/p-InGaP heterojunction (HJ) were investigated and compared to those of solar cells without QW structure. The epitaxial layers were grown on a p-GaAs substrate with $6^{\circ}$ off the (100) plane toward the <111>A. The heterojunction of solar cell consisted of a 400 nm N-AlGaInP, a 590 nm p-GaInP and 14 periods of a 10 nm GaInP/5 nm GaAs for QW structure and a 800 nm p-GaInP for the HJ structure (control cell). The solar cells were characterized after the anti-reflection coating. The short-circuit current density for $1{\times}1mm^2$ area was $9.61mA/cm^2$ for the solar cell with QW structure while $7.06mA/cm^2$ for HJ control cells. Secondary ion mass spectrometry and external quantum efficiency results suggested that the significant enhancement of $J_{sc}$ and EQE was caused by the suppression of recombination by QW structure.

Estimation of Piezoelectric Fields built in InxGa1-XGaN Quantum Well Structures using Numerical Analysis (InxGa1-XN/GaN 양자우물 구조의 수치 해석을 이용한 압전장 평가)

  • 김경찬;김태근
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.17 no.1
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    • pp.89-93
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    • 2004
  • Piezoelectric fields built in I $n_{x}$G $a_1$$_{-x}$N/GaN (x=0.06∼0.1) quantum wells (QWs) have been estimated by comparing the transition energies, both calculated and measured by photoluminescence (PL). The calculation was numerically carried out with a rectangular QW model, where the effective bandgap considering a bowing facto, energy levels quantized for the lowest lying electrons and heavy holes (1e-lhh), and biaxial compressive strain were included except for the piezoelectric fields. The calculated values were observed to be larger (9∼15 meV) than the measured values by PL, which was considered to be caused by the piezoelectric fields built in InGaN/GaN QW interface. In addition, we observed the energy shift by measuring the EPDPL (excitation power-dependent PL), which was compared with the energy difference caused by the piezoelectric fields.

Optical Properties of ZnO-ZnMgO Quantum Wells Grown by Atomic Layer Deposition Technique (원자층 증착법으로 성장한 ZnO-ZnMgO 양자우물의 광전이 특성)

  • Shin, Y.H.;Kim, Yongmin
    • Journal of the Korean Vacuum Society
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    • v.22 no.1
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    • pp.7-12
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    • 2013
  • We fabricated ZnO-ZnMgO single quantum well (SQW) samples having different well-widths by using the atomic layer deposition technique. The QW samples exhibit different optical transition behaviors with different QW widths. We confirm that when the well-width of 1.5 nm does not have a confined quantum energy level due to the Mg diffusion into the well caused by after-thermal treatment whereas the QWs wider than 1.5 nm show optical transitions between the confined energy levels.

Growth and characterization of single InGaN quantum well in nonpolar a-plane ($11{\bar{2}}0$) InGaN/GaN light-emitting diodes

  • Bang, Kyuhyun;Jung, Sukkoo;Baik, Kwang Hyeon;Myoung, Jae-Min
    • Current Applied Physics
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    • v.17 no.6
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    • pp.842-846
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    • 2017
  • We studied the In incorporation efficiency and composition distribution in a nonpolar a-plane InGaN (a-InGaN) quantum well (QW) layer. The In compositions decreased with increasing growth temperatures due to increased In desorption from InGaN surfaces. It was clear that the In incorporation efficiency on a nonpolar GaN surface is lower than that on a polar c-plane GaN. In addition, the In incorporation rate on an a-InGaN layer could be increased by decreasing the V/III ratio without lowering the growth temperature. In the case of the a-InGaN layer, a composition pulling effect was also observed, suggesting that the In composition of the a-InGaN layer increases along the normal growth direction from the bottom to the top of the InGaN QW layer. Using high-resolution XRD $2{\theta}-{\omega}$ scans, we found that there existed convex graded In compositions ranging from 4 to 12.7% in an a-InGaN QW layer along the growth direction. No wavelength shift with a current injection of 20-100 mA confirmed the absence of a polarization field. The shift in the electroluminescence (EL) peak energy was ~11 meV between the electric field parallel and perpendicular to the c-axis components, which was caused by the valence band splitting due to the in-plane compressive strain of the 10 nm a-InGaN QW layer. The EL polarization anisotropy was clearly observed with a polarization ratio of 55%.

Comparisons of lasing characteristics of InGaAs quantum-dot and quantum well laser diodes (InGaAs 양자점 레이저 다이오드와 양자우물 레이저 다이오드의 특성 비교)

  • Jung, Kyung-Wuk;Kim, Kwang-Woong;Ryu, Sung-Pil;Cho, Nam-Ki;Park, Sung-Jun;Song, Jin-Dong;Choi, Won-Jun;Lee, Jung-Il;Yang, Hae-Suk
    • Journal of the Korean Vacuum Society
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    • v.16 no.5
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    • pp.371-376
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    • 2007
  • We have investigated the lasing characteristics of the InGaAs quantum dot laser diode (QD-LD) and InGaAs quantum well laser diode (QW-LD) operated at the 980 nm wavelength range. The 980-nm lasers are used as a pumping source for a erbium-doped fiber amplifier (EDFA) and it shows high efficiency in long-haul optical fiber network. We have compared the threshold current density, the characteristic temperature, the optical power and the internal efficiency of QD-LD and QW-LD under a pulsed current condition. The QD-LD shows superior performances to the QW-LD. Further optimization of a LD structure is expected to the superior performances of a QD-LD.

Uniformly strained AlGaSb/InGaSb/AlGaSb quantum well on GaAs substrates for balanced complementary metal-oxide-semiconductors

  • Roh, Il Pyo;Kim, Sang Hyeon;Song, Yun Heub;Song, Jin Dong
    • Current Applied Physics
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    • v.17 no.3
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    • pp.417-421
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    • 2017
  • We designed and fabricated an $Al_{0.9}Ga_{0.1}Sb/In_{0.4}Ga_{0.6}Sb/Al_{0.9}Ga_{0.1}Sb$ quantum well (QW) with a balanced band offset for channel materials in future complementary metal-oxide-semiconductor (CMOS) circuits. The QW design was carried out by one-dimensional Schrodinger-Poisson equation system. The QW was grown by molecular beam epitaxy and the crystallinity and the surface morphology were characterized using a transmission electron microscope (TEM) and atomic force microscope (AFM), respectively. The results showed good crystalline behaviors and morphologies without any identifiable morphological defects. Furthermore, we investigated the strain characteristics in $In_{0.4}Ga_{0.6}Sb$ by measuring the Raman shift. We found that $In_{0.4}Ga_{0.6}Sb$has high compressive strain of 1.74% and the strain distribution was uniform.