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Monolithically integrated high-resolution full-color GaN-on-Si micro-LED microdisplay

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Photonics Research 2023年第1期11卷 109-120页

作者： LONGHENG QI XU ZHANG WING CHEUNG CHONG kei may lau Department of Electronic and Computer Engineering The Hong Kong University of Science and TechnologyHong KongChina

Full-color micro-LED displays are being widely developed and regarded as a primary option in current microdisplay technologies to fulfill the urgent demands of metaverse applications in the next *** this paper,a monolithic full-color micro-LED microdisplay with a resolution of 423 pixels per inch is demonstrated through the integration of a blue GaN-on-Si display module and a quantum dots photoresist(QDs-PR)color conversion *** 400×240 active-matrix blue micro-LED display with a dominant wavelength of 440 nm was monolithically fabricated using GaN-on-Si epiwafers and flip-chip bonded on a custom-designed complementary metal-oxide semiconductor backplane.A color conversion module was independently fabricated on a *** substrate by applying red and green QDs-PR arrays and a color filter array through the standard lithography *** the blue GaN-on-Si micro-LED display module and the lithography-based QDs-PR color conversion module,a full-color micro-LED display was achieved with a wide color gamut up to 104%of the standard red,green,and blue and a maximum brightness of over 500 *** influence of blue light leakage resulting from the possible misalignment of flip-chip bonding and crosstalk in the bottom GaN-on-Si display was investigated in which the percentages of efficient pumping light for the blue,green,and red subpixels are around95%,89%,and 92%,*** prototype demonstrates potential scalability and low-cost volume production of high-resolution full-color micro-LED microdisplays soon.

关键词： lithography pumping complementary

Room temperature Ⅲ–Ⅴ nanolasers with distributed Bragg reflectors epitaxially grown on(001) silicon-on-insulators

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Photonics Research 2019年第9期7卷 1081-1086页

作者： YU HAN WAI KIT NG YING XUE KAM SING WONG kei may lau Department of Electronic and Computer Engineering Hong Kong University of Science and TechnologyClear Water BayKowloonHong KongChina Department of Physics and William Mong Institute of Nano Science and Technology Hong Kong University of Science and TechnologyClear Water BayKowloonHong KongChina

Efficient, scalable, bufferless, and compact Ⅲ–V lasers directly grown on(001)-oriented silicon-on-insulators(SOIs) are preferred light sources in Si-photonics. In this article, we present the design and operation of Ⅲ–V telecom nanolaser arrays with integrated distributed Bragg reflectors(DBRs) epitaxially grown on industry-standard(001) SOI wafers. We simulated the mirror reflectance of different guided modes under various mirror architectures, and accordingly devised nanoscale DBR gratings to support high reflectivity around1500 nm for the doughnut-shaped TE01 mode. Building from InP/InGaAs nanoridges grown on SOI, we fabricated subwavelength DBR mirrors at both ends of the nanoridge laser cavities and thus demonstrated room-temperature low-threshold InP/InGaAs nanolasers with a 0.28 μm^2 cross-section and a 20 μm effective cavity length. The direct growth of these bufferless nanoscale Ⅲ–V light emitters on Si-photonics standard(001) SOI wafers opens future options of fully integrated Si-based nanophotonic integrated circuits in the telecom wavelength regime.

关键词： InGaAs InP SOI nanolasers with distributed Bragg reflectors epitaxially grown on Room temperature silicon-on-insulators Bragg

Comparison of growth structures for continuouswave electrically pumped 1.55 μm quantum dash lasers grown on(001) Si

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Photonics Research 2020年第12期8卷 1888-1894页

作者： WEI LUO YING XUE JIE HUANG LIYING LIN BEI SHI kei may lau Department of Electronic and Computer Engineering The Hong Kong University of Science and TechnologyClear Water BayKowloonHong KongChina

Semiconductor lasers directly grown on silicon offer great potential as critical components in high-volume,lowcost integrated silicon photonics *** InAs/InP quantum dash(QDash)lasers on native InP substrate emitting at 1.5μm(C-band)have demonstrated notable performance,the growth of InAs/InP QDash lasers on silicon remains undeveloped because of the 8%lattice mismatch between InP and *** we report advances of growth techniques leading to the first C-band room-temperature continuous-wave electrically pumped QDash lasers on CMOS standard(001)silicon substrates by metalorganic chemical vapor deposition.A correlation between various material characterizations and device performance is analyzed for different QDash laser structures grown on planar nominal(001)*** the optimized QDash growth and improved fabrication process,the lowest threshold current density of 1.5 kA∕cm^(2) was determined on an 8μm×1.5 mmdevice on planar silicon with a single facet output power exceeding 14 *** device results illustrate the good material quality of the QDash lasers grown on silicon,suggesting potential applications for other active components of photonic integrated circuits,such as semiconductor optical amplifiers,modulators,and photodetectors.

关键词： pumped quantum wave

Monolithic full-color active-matrix micro-LED microdisplay using InGaN/AlGaInP heterogeneous integration

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Light(Science & Applications) 2023年第11期12卷 2459-2467页

作者： Longheng Qi Peian Li Xu Zhang Ka Ming Wong kei may lau Department of Electronic and Computer Engineering The Hong Kong University of Science and TechnologyClear Water BayKowloonHong KongChina

A prototype of full-color active-matrix micro-light-emitting diode(micro-LED)micro-display with a pixel density of 391 pixel per inch(ppi)using InGaN/AlGaInP heterogeneous integration is *** blue/green dual-color micro-LED arrays realized on a single metal organic chemical vapor deposition(MOCVD)-grown GaN-on-Si epiwafer and AlGaInP red micro-LED arrays are both monolithically fabricated,followed by the integration with a common complementary metal oxide semiconductor(CMOS)backplane via flip-chip bonding technology to form a doublelayer thin-film display ***-color images with decent color gamut and brightness are successfully displayed through the fine adjustment of driving current densities of RGB *** full-color display combines the advantages of high quantum efficiency of InGaN material on blue/green light and AlGaInP material on red light through heterogeneous integration and high pixel density through monolithic fabrication approach,demonstrating the feasibility and prospects of high brightness,good color performance,and high-resolution micro-LED microdisplays in future metaverse applications.

关键词： AlGaInP integration matrix

Low-efficiency-droop InGaN quantum dot light-emitting diodes operating in the “green gap”

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Photonics Research 2020年第5期8卷 750-754页

作者： CHUNYU ZHAO CHAK WAH TANG BILLY LAI GUANGHUI CHENG JIANNONG WANG kei may lau Department of Electronic and Computer Engineering Hong Kong University of Science and TechnologyClear Water BayKowloonHong KongChina Department of Physics Hong Kong University of Science and TechnologyClear Water BayKowloonHong KongChina

Gallium nitride(Ga N)-based light-emitting diodes(LEDs)are important for lighting and display *** this paper,we demonstrate green-emission(512 nm)In Ga N quantum dot(QD)LEDs grown on a c-plane sapphire substrate by metal-organic chemical vapor deposition.A radiative lifetime of 707 ps for the uniform In Ga N self-assembled QDs is obtained by time-resolved photoluminescence measurement at 18 *** screening of the built-in fields in the QDs effectively improves the performance of QD *** high quantum efficiency and high temperature stability green QD LEDs are able to operate with negligible efficiency droop and with current density up to 106 A∕cm^*** results show that In Ga N QDs may be a viable option as the active medium for stable LEDs.

关键词： diodes sapphire quantum

Optical cross-talk reduction in a quantumdot-based full-color micro-light-emitting-diode display by a lithographic-fabricated photoresist mold

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Photonics Research 2017年第5期5卷 411-416页

作者： HUANG-YU LIN CHIN-WEI SHER DAN-HUA HSIEH XIN-YIN CHEN HUANG-MING PHILIP CHEN TENG-MING CHEN kei-may lau CHYONG-HUA CHEN CHIEN-CHUNG LIN HAO-CHUNG KUO Department of Photonics and Institute of Electro-Optical Engineering National Chiao Tung University Department of Applied Chemistry National Chiao Tung University Department of Electric and Computer Engineering Hong Kong University of Science and Technology Institute of Photonic System National Chiao Tung University

In this study, a full-color emission red–green–blue(RGB) quantum-dot(QD)-based micro-light-emitting-diode(micro-LED) array with the reduced optical cross-talk effect by a photoresist mold has been demonstrated. The UV micro-LED array is used as an efficient excitation source for the QDs. The aerosol jet technique provides a narrow linewidth on the micrometer scale for a precise jet of QDs on the micro-LEDs. To reduce the optical cross-talk effect,a simple lithography method and photoresist are used to fabricate the mold, which consists of a window for QD jetting and a blocking wall for cross-talk reduction. The cross-talk effect of the well-confined QDs in the window is confirmed by a fluorescence microscope, which shows clear separation between QD pixels. A distributed Bragg reflector is covered on the micro-LED array and the QDs' jetted mold to further increase the reuse of UV *** enhanced light emission of the QDs is 5%, 32%, and 23% for blue, green, and red QDs, respectively.

关键词： QDs Optical cross-talk reduction in a quantumdot-based full-color micro-light-emitting-diode display by a lithographic-fabricated photoresist mold

Characteristics of the crack tip field in high-speed railway tunnel linings under train-induced aerodynamic shockwaves

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Underground Space 2024年第5期18卷 199-217页

作者： Yi-Kang Liu Yu-Ling Wang E Deng Yi-Qing Ni Wei-Chao Yang Wai-kei Ao School of Civil Engineering Central South UniversityChangsha 410075China National Rail Transit Electrification and Automation Engineering Technology Research Center(Hong Kong Branch) The Hong Kong Polytechnic UniversityHong Kong 999077China Department of Civil and Environmental Engineering The Hong Kong Polytechnic UniversityHong Kong 999077China The Hong Kong Polytechnic University Shenzhen Research Institute Shenzhen 518057China National Engineering Research Center of High-speed Railway Construction Technology Changsha 410075China

High-speed railway tunnels in various countries have continuously reported accidents of vault falling concrete *** the concrete block falling occurs,serious consequences follow,and traffic safety may be *** aerodynamic shockwave evolves from the initial compression wave may be an important inducement causing the tunnel lining cracks to grow and form falling concrete blocks.A joint calculation framework is established based on ANSYS Fluent,ABAQUS,and FRANC3D for calculating the crack tip field under the aerodynamic *** intensification effect of aerodynamic shockwaves in the crack is revealed,and the evolution characteristics of the crack tip field and the influence factors of stress intensity factor(SIF)are *** show that(1)the aerodynamic shockwave intensifies after entering the crack,resulting in more significant pressure in the crack than the input *** maximum pressure of the inclined and longitudinal cracks is higher than the corresponding values of the circumferential crack,respectively.(2)The maximum SIF of the circumferential,inclined,and longitudinal crack appears at 0.5,0.68,and 0.78 times the crack front *** maximum SIF of the circumferential crack is higher than that of the inclined and longitudinal *** possibility of crack growth of the circumferential crack is the highest under aerodynamic shockwaves.(3)The influence of train speed on the SIF of the circumferential crack is more than 40%.When the train speed,crack depth,and crack length change,the change of pressure in the crack is the direct cause of the change of SIF.

关键词： Falling concrete blocks Tunnel lining cracks Aerodynamic shockwave Intensification effect Crack tip field Stress intensity factor

Improved AlGaN/GaN HEMTs Grown on Si Substrates Using Stacked AlGaN/AlN Interlayer by MOCVD

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Chinese Physics Letters 2011年第5期28卷 206-209页

作者： WANG Yong YU Nai-Sen LI Ming lau kei-may National Key Lab on High Power Semiconductor Lasers Changchun University of Science and TechnologyChangchun 130022 Photonics Technology Center Department of Electronic and Computer EngineeringHong Kong University of Science and TechnologyClear Water BayKowloonHong KongChina

AlGaN/GaN high electron mobility transistors(HEMTs)are grown on 2-inch Si(111)substrates by *** stacked AlGaN/AlN interlayer with different AlGaN thickness and indium surfactant doped is designed and optimized to relieve the tensile stress during GaN epitaxial *** top 1.0μm GaN buffer layer grown on the optimized AlGaN/AlN interlayer shows a crack-free and shining *** XRD results show that GaN(002)FWHM is 480arcsec and GaN(102)FWHM is *** AGaN/GaN HEMTs with optimized and nonoptimized AlGaN/AlN interlayer are grown and processed for comparison and the dc and rf characteristics are *** the dc characteristics of the device with optimized AlGaN/AlN interlayer,maximum drain current density I_(dss)of 737mA/mm,peak transconductance G_(m)of 185mS/mm,drain leakage current density Ids of 1.7μA/mm,gate leakage current density I_(gs)of 24.8μA/mm and off-state breakdown voltage VBR of 67V are achieved with L_(g)/W_(g)/L_(g)/L_(g)=1/10/1/1μ*** the small signal rf characteristics of the device with optimized AlGaN/AlN interlayer,current gain cutoff frequency fT of 8.3 GHz and power gain cutoff frequency fmax of 19.9GHz are achieved with L_(g)/W_(g)/L_(g)/L_(g)=1/100/1/1μ***,the best rf performance with fT of 14.5 GHz and fmax of 37.3 GHz is achieved with a reduced gate length of 0.7μm.

关键词： AlGaN/GaN Si(111) HEMTs MOCVD

Net effect of air pollution controls on health risk in the Beijing-Tianjin-Hebei region during the 2022 winter Olympics and Paralympics

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Journal of Environmental Sciences 2024年第1期135卷 560-569页

作者： Changqing Lin Peter K.K.Louie Alexis K.H.lau Jimmy C.H.Fung Zibing Yuan Minghui Tao Xuguo Zhang Md.Shakhaoat Hossain Chengcai Li Xiang Qian Lao Division of Environment and Sustainability The Hong Kong University of Science and TechnologyHong KongChina Environmental Protection Department Hong Kong Government SARHong KongChina Department of Civil and Environmental Engineering The Hong Kong University of Science and TechnologyHong KongChina Guangdong-Hongkong-Macao Joint Laboratory of Collaborative Innovation for Environmental Quality The Hong Kong University of Science and TechnologyHong KongChina Department of Mathematics The Hong Kong University of Science and TechnologyHong KongChina School of Environment and Energy South China University of TechnologyGuangzhou 510006China Hubei Key Laboratory of Critical Zone Evolution School of Geography and Information EngineeringChina University of GeosciencesWuhan 430074China Department of Public Health and Informatics Jahangirnagar UniversityDhaka 1342Bangladesh Department of Atmospheric and Oceanic Sciences School of PhysicsPeking UniversityBeijing 100871China Jockey Club School of Public Health and Primary Care The Chinese University of Hong KongHong KongChina

Due to the non-linearity in ozone(O_(3))formation,reducing the emission of nitrogen oxides(NO_(x))may increase O_(3) *** the counteractive O_(3) response to NO_(x) reduction,overall impact of air pollution controls can be ambiguous when the assessments focus on the changes in pollutant *** this study,a risk-based method was used to gauge the net effect of air pollution controls on mortality risk in the Beijing–Tianjin–Hebei(BTH)region during the 2022 Winter Olympics and Paralympics(WOP).This mega-event presents a unique opportunity to investigate the efficacy of deep cuts in pollutant *** show that O_(3) concentrations greatly increased as nitrogen dioxide(NO_(2))concentrations decreased in the *** to the active photochemical formations,O_(3) became the dominant pollutant that affected human health during the *** the substantial O_(3) increases,the health benefits of NO_(2) reductions overwhelmed the adverse health effects of O_(3) increases in most regions of the BTH(at 81 out of 112 stations).After considering the impacts of particulate matter,the integrated health risk of air pollution mixtures declined almost everywhere in the *** results underscore the great necessity of changing the assessment paradigm of pollution control from using concentration-based methods to using risk-based *** with the carbon neutrality policy,stringent control of NO_(x)emission from combustion sources is a promising way to achieve synergistic control solutions for air pollution and climate change.

关键词： Ozone Nitrogen dioxide Health risk Carbon neutrality Mega-events