Silver nanowire（AgNW） film was proposed to apply on the surface of the vertical-cavity surface-emitting lasers（VCSELs） with large aperture in order to obtain a uniform current distribution in the active region and...Silver nanowire（AgNW） film was proposed to apply on the surface of the vertical-cavity surface-emitting lasers（VCSELs） with large aperture in order to obtain a uniform current distribution in the active region and a better optical beam quality.Optimization of the AgNW film was carried out with the sheet resistance of 28.4 Ω/sq and the optical transmission of 94.8% at 850 nm.The performance of VCSELs with and without AgNW film was studied.When the AgNW film was applied to the surface of VCSELs,due to its better current spreading effect,the maximum output optical power increased from 23.4 mW to 24.4 mW,the lasing wavelength redshift decreased from 0.085 nm/mA to 0.077 nm/mA,the differential resistance decreased from 23.95 Ω to 21.13 Ω,and the far field pattern at 50 mA decreased from 21.6° to 19.2°.At the same time,the near field test results showed that the light in the aperture was more uniform,and the far field exhibited a better single peak characteristic.Various results showed that VCSELs with AgNW on the surface showed better beam quality.展开更多
Polarization-stable 980 nm oxide-confined vertical-cavity surface-emitting lasers with 3 μm diamond-shaped aper- ture are fabricated by comprehensively utilizing the anisotropic properties of wet etching and wet nitr...Polarization-stable 980 nm oxide-confined vertical-cavity surface-emitting lasers with 3 μm diamond-shaped aper- ture are fabricated by comprehensively utilizing the anisotropic properties of wet etching and wet nitrogen oxida- tion of Ⅲ-Ⅴ semiconductor materials. Polarization-stable operation along the major axis of the diamond-shaped oxide aperture with 11 dB orthogonal polarization suppression ratio is achieved in a temperature range of 15-55℃ from the threshold to 4 mA.展开更多
A low-threshold and high-power oxide-confined 850-nm AlInGaAs strained quantum-well （QW） vertical-cavity surface-emitting laser （VCSEL） based on an intra-cavity contacted structure is fabricated. A threshold curre...A low-threshold and high-power oxide-confined 850-nm AlInGaAs strained quantum-well （QW） vertical-cavity surface-emitting laser （VCSEL） based on an intra-cavity contacted structure is fabricated. A threshold current of 1.5 mA for a 22 μm oxide aperture device is achieved, which corresponds to a threshold current density of 0.395 kA/cm2. The peak output optical power reaches 17.5 mW at an injection current of 30 mA at room temperature under pulsed opera- tion. While under continuous-wave （CW） operation, the maximum power attains 10.5 mW. Such a device demonstrates a high characteristic temperature of 327 K within a temperature range from -12°C to 96 °C and good reliability under a lifetime test. There is almost no decrease of the optical power when the device operates at a current of 5 mA at room temperature under the CW injection current.展开更多
The maximum power conversion efficiencies of the top-emitting,oxide-confined,two-dimensional integrated 2×2 and4×4 vertical-cavity surface-emitting laser（VCSEL） arrays with the oxide-apertures of 6 μm,16 ...The maximum power conversion efficiencies of the top-emitting,oxide-confined,two-dimensional integrated 2×2 and4×4 vertical-cavity surface-emitting laser（VCSEL） arrays with the oxide-apertures of 6 μm,16 μm,19 μm,26 μm,29 μm,36 μm,39 μm,and 46 urn are fabricated and characterized,respectively.The maximum power conversion efficiencies increase rapidly with the augment of oxide-aperture at the beginning and then decrease slowly.A maximum value of27.91%at an oxide-aperture of 18.6 μm is achieved by simulation.The experimental data are well consistent with the simulation results,which are analyzed by utilizing an empirical model.展开更多
Experimental investigation on resonant tunneling in various GaAs/Al<sub>x</sub>Ga<sub>1-x</sub>Asdouble barrier single well structures has been performed by using tunneling spectroscopy atdiffe...Experimental investigation on resonant tunneling in various GaAs/Al<sub>x</sub>Ga<sub>1-x</sub>Asdouble barrier single well structures has been performed by using tunneling spectroscopy atdifferent temperatures.The results show that in addition to resonant tunneling via GaAs wellstate confined by Al<sub>x</sub>Ga<sub>1-x</sub>As Γ-point barrier there exists resonant tunneling via GaAs well stateconfined by Al<sub>x</sub>Ga<sub>1-x</sub>As X-point barrier for both indirect（x】0.4）and direct（x【0.4）cases.展开更多
A two-dimensional apodized grating coupler for interfacing between single-mode fiber and photonic circuit is demonstrated in order to bridge the mode gap between the grating coupler and optical fiber. The grating groo...A two-dimensional apodized grating coupler for interfacing between single-mode fiber and photonic circuit is demonstrated in order to bridge the mode gap between the grating coupler and optical fiber. The grating grooves of the grating couplers are realized by columns of fully etched nanostructures, which are utilized to digitally tailor the effective refractive index of each groove in order to obtain the Gaussian-like output diffractive mode and then enhance the coupling efficiency.Compared with that of the uniform grating coupler, the coupling efficiency of the apodized grating coupler is increased by 4.3% and 5.7%, respectively, for the nanoholes and nanorectangles as refractive index tunes layer.展开更多
Carbon dioxide,as a greenhouse gas,is expected to be converted into other useful substances by the electrocatalytic CO_(2)reduction reaction(CO_(2)RR)technology.The electrocatalytic cell,or electrochemical cell,used t...Carbon dioxide,as a greenhouse gas,is expected to be converted into other useful substances by the electrocatalytic CO_(2)reduction reaction(CO_(2)RR)technology.The electrocatalytic cell,or electrochemical cell,used to provide the experimental environment for CO_(2)RR plays an irreplaceable role in the study of this process and determines the success or failure of the measurements.In recent years,electrolytic cells that can be applied to in-situ/operational synchrotron radiation(SR)characterization techniques have gradually gained widespread attention.However,the design and understanding of electrolyte systems that can be applied to in-situ/operational SR technologies are still not sufficiently advanced.In this paper,the electrocatalytic cells used to study the CO_(2)RR processes with in-situ/operando SR techniques are briefly introduced,and the types and characteristics of the electrolytic cells are analyzed.The recent advancements of in situ/operando electrolytic cells are discussed using X-ray scattering,X-ray absorption spectroscopy(XAS),light vibration spectroscopy,and X-ray combined techniques.An outlook is provided on the future prospects of this research field.This review facilitates the understanding of the reduction process and electrocatalytic mechanism of CO_(2)RR at the atomic and molecular scales,providing insights for the design of electrolysis cells applicable to SR technologies and accelerating the development of more efficient and sustainable carbon negative technologies.展开更多
Databases for two-dimensional materials host numerous ferromagnetic materials without the vital information of Curie temperature since its calculation involves a manually intensive complex process.In this work,we deve...Databases for two-dimensional materials host numerous ferromagnetic materials without the vital information of Curie temperature since its calculation involves a manually intensive complex process.In this work,we develop a fully automated,hardwareaccelerated,dynamic-translation based computer code,which performs first principles-based computations followed by Heisenberg model-based Monte Carlo simulations to estimate the Curie temperature from the crystal structure.We employ this code to conduct a high-throughput scan of 786 materials from a database to discover 26 materials with a Curie point beyond 400 K.For rapid data mining,we further use these results to develop an end-to-end machine learning model with generalized chemical features through an exhaustive search of the model space as well as the hyperparameters.We discover a few more high Curie point materials from different sources using this data-driven model.Such material informatics,which agrees well with recent experiments,is expected to foster practical applications of two-dimensional magnetism.展开更多
Machine learning techniques have proven invaluable to manage the ever growing volume of materials research data produced as developments continue in high-throughput materials simulation,fabrication,and characterizatio...Machine learning techniques have proven invaluable to manage the ever growing volume of materials research data produced as developments continue in high-throughput materials simulation,fabrication,and characterization.In particular,machine learning techniques have been demonstrated for their utility in rapidly and automatically identifying potential composition-phase maps from structural data characterization of composition spread libraries,enabling rapid materials fabrication-structure-property analysis and functional materials discovery.A key issue in development of an automated phase-diagram determination method is the choice of dissimilarity measure,or kernel function.The desired measure reduces the impact of confounding structural data issues on analysis performance.The issues include peak height changes and peak shifting due to lattice constant change as a function of composition.In this work,we investigate the choice of dissimilarity measure in X-ray diffraction-based structure analysis and the choice of measure’s performance impact on automatic composition-phase map determination.Nine dissimilarity measures are investigated for their impact in analyzing X-ray diffraction patterns for a Fe-Co-Ni ternary alloy composition spread.The cosine,Pearson correlation coefficient,and Jensen-Shannon divergence measures are shown to provide the best performance in the presence of peak height change and peak shifting(due to lattice constant change)when the magnitude of peak shifting is unknown.With prior knowledge of the maximum peak shifting,dynamic time warping in a normalized constrained mode provides the best performance.This work also serves to demonstrate a strategy for rapid analysis of a large number of X-ray diffraction patterns in general beyond data from combinatorial libraries.展开更多
Two-dimensional material-based transistors are being extensively investigated for CMOS(complementary metal oxide semiconductor)technology extension;nevertheless,downscaling appears to be challenging owing to high meta...Two-dimensional material-based transistors are being extensively investigated for CMOS(complementary metal oxide semiconductor)technology extension;nevertheless,downscaling appears to be challenging owing to high metal-semiconductor contact resistance.Here,we propose a functional group-engineered monolayer transistor architecture that takes advantage of MXenes’natural material chemistry to offer low-resistive contacts.We design an automated,high-throughput computational pipeline that first performs hybrid density functional theory-based calculations to find 16 sets of complementary transistor configurations by screening more than 23,000 materials from an MXene database and then conducts self-consistent quantum transport calculations to simulate their current-voltage characteristics for channel lengths ranging from 10 nm to 3 nm.Performance of these devices has been found to meet the requirements of the international roadmap for devices and systems(IRDS)for several benchmark metrics(on current,power dissipation,delay,and subthreshold swing).The proposed balanced-mode,functional-engineered MXene transistors may lead to a realistic solution for the sub-decananometer technology scaling by enabling doping-free intrinsically low contact resistance.展开更多
In order to resolve the prevailing problems in conventional light-emitting diodes (LEDs), novel high-efficiency tunneling-regenerated multi-active-region (TRMAR) LEDs are proposed, which have such advantages as low he...In order to resolve the prevailing problems in conventional light-emitting diodes (LEDs), novel high-efficiency tunneling-regenerated multi-active-region (TRMAR) LEDs are proposed, which have such advantages as low heat generation, carrier overflow level and non-radiation re-combination rate and whose quantum efficiency and the output optical power can be scaled with the number of the active regions. Experiments show that the on-axis luminous intensity of TRMAR LEDs increases linearly with the number of active regions. The novel LEDs have high quantum efficiency under low current injection and their maximum on-axis luminous intensity exceeds 5 candelas at 20 mA current injection at the peak wavelength of 625 nm with a 15?angle cap.展开更多
Two-dimensional apodized grating couplers are proposed with grating grooves realized by a series of nano- rectangles, with the feasibility of digital tailoring the equivalent refractive index of each groove in order t...Two-dimensional apodized grating couplers are proposed with grating grooves realized by a series of nano- rectangles, with the feasibility of digital tailoring the equivalent refractive index of each groove in order to obtain the Gaussian output diffractive mode in order to enhance the coupling efficiency to the optical fiber. According to the requirement of leakage factor distribution for a Gaussian output profile, the corresponding effective re- fractive index of the grating groove, duty cycle, and period are designed according to the equivalent medium theory. The peak coupling efficiency of 93.1% at 1550 nm and 3 dB bandwidth of 82 nm are achieved.展开更多
Magnetic skyrmions,which are topologically protected tiny spin textures,have emerged as information carriers in energy-efficient logic and memory devices.Skyrmions are commonly realized by inducing large Dzyaloshinski...Magnetic skyrmions,which are topologically protected tiny spin textures,have emerged as information carriers in energy-efficient logic and memory devices.Skyrmions are commonly realized by inducing large Dzyaloshinskii–Moriya interaction(DMI)in the interface of heavy metal heterolayers.With the advent of two-dimensional magnetism,it is being envisioned to host intrinsic skyrmions in a monolayer,which will be free from any interfacial defect and stacking order.Here using high-fidelity exchange-correlation functional-based first-principles calculations,we investigate such a possibility in methodically designed non-centrosymmetric MXene structures.From a search space of about 3000 materials,our customized high-throughput computational pipeline systematically harnesses out-of-the-plane and in-plane magnetism along with strong DMI to realize typical‘unipolar’skyrmions in 78 materials and exotic‘bipolar’skyrmions in 13 materials.Micromagnetic and atomistic Monte Carlo simulations further reveal that skyrmions in some of these materials may be stable at room temperature without any external magnetic field.Our study may pave the way for the practical realization of skyrmions-based information technology.展开更多
In this paper TCAD-based simulation of a novel insulated shallow extension （ISE） cylindrical gate all around （CGAA） Schottky barrier （SB） MOSFET has been reported, to eliminate the suicidal ambipolar behavior （...In this paper TCAD-based simulation of a novel insulated shallow extension （ISE） cylindrical gate all around （CGAA） Schottky barrier （SB） MOSFET has been reported, to eliminate the suicidal ambipolar behavior （bias-dependent OFF state leakage current） of conventional SB-CGAA MOSFET by blocking the metal-induced gap states as well as unwanted charge sharing between source/channel and drain/channel regions. This novel structure offers low barrier height at the source and offers high ON-state current. The IoN/Iovr： of ISE-CGAA-SB-MOS- FET increases by 1177 times and offers steeper subthreshold slope （-60 mV/decade）. However a little reduction in peak cut off frequency is observed and to further improve the cut-off frequency dual metal gate architecture has been employed and a comparative assessment of single metal gate, dual metal gate, single metal gate with ISE, and dual metal gate with ISE has been presented. The improved performance of Schottky barrier CGAA MOSFET by the incorporation of ISE makes it an attractive candidate for CMOS digital circuit design. The numerical simulation is performed using the ATLAS-3D device simulator.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61335004 and 61505003)the National High Technology Research and Development Program of China(Grant No.2015AA017101)the National Key Research and Development of China(Grant No.2016YFB0400603)
文摘Silver nanowire（AgNW） film was proposed to apply on the surface of the vertical-cavity surface-emitting lasers（VCSELs） with large aperture in order to obtain a uniform current distribution in the active region and a better optical beam quality.Optimization of the AgNW film was carried out with the sheet resistance of 28.4 Ω/sq and the optical transmission of 94.8% at 850 nm.The performance of VCSELs with and without AgNW film was studied.When the AgNW film was applied to the surface of VCSELs,due to its better current spreading effect,the maximum output optical power increased from 23.4 mW to 24.4 mW,the lasing wavelength redshift decreased from 0.085 nm/mA to 0.077 nm/mA,the differential resistance decreased from 23.95 Ω to 21.13 Ω,and the far field pattern at 50 mA decreased from 21.6° to 19.2°.At the same time,the near field test results showed that the light in the aperture was more uniform,and the far field exhibited a better single peak characteristic.Various results showed that VCSELs with AgNW on the surface showed better beam quality.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61222501 and 61335004the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No 20111103110019
文摘Polarization-stable 980 nm oxide-confined vertical-cavity surface-emitting lasers with 3 μm diamond-shaped aper- ture are fabricated by comprehensively utilizing the anisotropic properties of wet etching and wet nitrogen oxida- tion of Ⅲ-Ⅴ semiconductor materials. Polarization-stable operation along the major axis of the diamond-shaped oxide aperture with 11 dB orthogonal polarization suppression ratio is achieved in a temperature range of 15-55℃ from the threshold to 4 mA.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.60908012 and 61076148)the Foundation of Beijing Municipal Education Commission,China (Grant No.KM201010005030)
文摘A low-threshold and high-power oxide-confined 850-nm AlInGaAs strained quantum-well （QW） vertical-cavity surface-emitting laser （VCSEL） based on an intra-cavity contacted structure is fabricated. A threshold current of 1.5 mA for a 22 μm oxide aperture device is achieved, which corresponds to a threshold current density of 0.395 kA/cm2. The peak output optical power reaches 17.5 mW at an injection current of 30 mA at room temperature under pulsed opera- tion. While under continuous-wave （CW） operation, the maximum power attains 10.5 mW. Such a device demonstrates a high characteristic temperature of 327 K within a temperature range from -12°C to 96 °C and good reliability under a lifetime test. There is almost no decrease of the optical power when the device operates at a current of 5 mA at room temperature under the CW injection current.
基金supported by the National Natural Science Foundation of China(Grant Nos.61222501 and 61335004)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20111103110019)
文摘The maximum power conversion efficiencies of the top-emitting,oxide-confined,two-dimensional integrated 2×2 and4×4 vertical-cavity surface-emitting laser（VCSEL） arrays with the oxide-apertures of 6 μm,16 μm,19 μm,26 μm,29 μm,36 μm,39 μm,and 46 urn are fabricated and characterized,respectively.The maximum power conversion efficiencies increase rapidly with the augment of oxide-aperture at the beginning and then decrease slowly.A maximum value of27.91%at an oxide-aperture of 18.6 μm is achieved by simulation.The experimental data are well consistent with the simulation results,which are analyzed by utilizing an empirical model.
文摘Experimental investigation on resonant tunneling in various GaAs/Al<sub>x</sub>Ga<sub>1-x</sub>Asdouble barrier single well structures has been performed by using tunneling spectroscopy atdifferent temperatures.The results show that in addition to resonant tunneling via GaAs wellstate confined by Al<sub>x</sub>Ga<sub>1-x</sub>As Γ-point barrier there exists resonant tunneling via GaAs well stateconfined by Al<sub>x</sub>Ga<sub>1-x</sub>As X-point barrier for both indirect（x】0.4）and direct（x【0.4）cases.
基金supported by the National Natural Science Foundation of China(Grant Nos.61222501,61335004,and 61505003)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20111103110019)+1 种基金the Postdoctoral Science Foundation of Beijing Funded Project,China(Grant No.Q6002012201502)the Science and Technology Research Project of Jiangxi Provincial Education Department,China(Grant No.GJJ150998)
文摘A two-dimensional apodized grating coupler for interfacing between single-mode fiber and photonic circuit is demonstrated in order to bridge the mode gap between the grating coupler and optical fiber. The grating grooves of the grating couplers are realized by columns of fully etched nanostructures, which are utilized to digitally tailor the effective refractive index of each groove in order to obtain the Gaussian-like output diffractive mode and then enhance the coupling efficiency.Compared with that of the uniform grating coupler, the coupling efficiency of the apodized grating coupler is increased by 4.3% and 5.7%, respectively, for the nanoholes and nanorectangles as refractive index tunes layer.
基金supported by the Innovation Program of the Institute of High Energy Physics,Chinese Academy of Sciences(Grant No.2023000034),Chinathe National Natural Science Foundation of China(Grant No.12275300)+1 种基金the Nature Science Foundation of Heilongjiang Province(Grant No.LH2019A025),Chinathe Project of Education Department of Heilongjiang Province(Grant No.145209101),China.
文摘Carbon dioxide,as a greenhouse gas,is expected to be converted into other useful substances by the electrocatalytic CO_(2)reduction reaction(CO_(2)RR)technology.The electrocatalytic cell,or electrochemical cell,used to provide the experimental environment for CO_(2)RR plays an irreplaceable role in the study of this process and determines the success or failure of the measurements.In recent years,electrolytic cells that can be applied to in-situ/operational synchrotron radiation(SR)characterization techniques have gradually gained widespread attention.However,the design and understanding of electrolyte systems that can be applied to in-situ/operational SR technologies are still not sufficiently advanced.In this paper,the electrocatalytic cells used to study the CO_(2)RR processes with in-situ/operando SR techniques are briefly introduced,and the types and characteristics of the electrolytic cells are analyzed.The recent advancements of in situ/operando electrolytic cells are discussed using X-ray scattering,X-ray absorption spectroscopy(XAS),light vibration spectroscopy,and X-ray combined techniques.An outlook is provided on the future prospects of this research field.This review facilitates the understanding of the reduction process and electrocatalytic mechanism of CO_(2)RR at the atomic and molecular scales,providing insights for the design of electrolysis cells applicable to SR technologies and accelerating the development of more efficient and sustainable carbon negative technologies.
基金The GPU computing nodes used in this study were procured through the research funding from the Department of Science and Technology(DST),Government of India,under grant number DST/TMD/MES/2K18/28.
文摘Databases for two-dimensional materials host numerous ferromagnetic materials without the vital information of Curie temperature since its calculation involves a manually intensive complex process.In this work,we develop a fully automated,hardwareaccelerated,dynamic-translation based computer code,which performs first principles-based computations followed by Heisenberg model-based Monte Carlo simulations to estimate the Curie temperature from the crystal structure.We employ this code to conduct a high-throughput scan of 786 materials from a database to discover 26 materials with a Curie point beyond 400 K.For rapid data mining,we further use these results to develop an end-to-end machine learning model with generalized chemical features through an exhaustive search of the model space as well as the hyperparameters.We discover a few more high Curie point materials from different sources using this data-driven model.Such material informatics,which agrees well with recent experiments,is expected to foster practical applications of two-dimensional magnetism.
基金supported by NIST and NEC and partially supported by ONR N000141512222.
文摘Machine learning techniques have proven invaluable to manage the ever growing volume of materials research data produced as developments continue in high-throughput materials simulation,fabrication,and characterization.In particular,machine learning techniques have been demonstrated for their utility in rapidly and automatically identifying potential composition-phase maps from structural data characterization of composition spread libraries,enabling rapid materials fabrication-structure-property analysis and functional materials discovery.A key issue in development of an automated phase-diagram determination method is the choice of dissimilarity measure,or kernel function.The desired measure reduces the impact of confounding structural data issues on analysis performance.The issues include peak height changes and peak shifting due to lattice constant change as a function of composition.In this work,we investigate the choice of dissimilarity measure in X-ray diffraction-based structure analysis and the choice of measure’s performance impact on automatic composition-phase map determination.Nine dissimilarity measures are investigated for their impact in analyzing X-ray diffraction patterns for a Fe-Co-Ni ternary alloy composition spread.The cosine,Pearson correlation coefficient,and Jensen-Shannon divergence measures are shown to provide the best performance in the presence of peak height change and peak shifting(due to lattice constant change)when the magnitude of peak shifting is unknown.With prior knowledge of the maximum peak shifting,dynamic time warping in a normalized constrained mode provides the best performance.This work also serves to demonstrate a strategy for rapid analysis of a large number of X-ray diffraction patterns in general beyond data from combinatorial libraries.
基金The research was funded by the Mathematical Research Impact Centric Support(MATRICS)scheme of the Science and Engineering Research Board(SERB),Government of India,under the grant number MTR/2019/000047。
文摘Two-dimensional material-based transistors are being extensively investigated for CMOS(complementary metal oxide semiconductor)technology extension;nevertheless,downscaling appears to be challenging owing to high metal-semiconductor contact resistance.Here,we propose a functional group-engineered monolayer transistor architecture that takes advantage of MXenes’natural material chemistry to offer low-resistive contacts.We design an automated,high-throughput computational pipeline that first performs hybrid density functional theory-based calculations to find 16 sets of complementary transistor configurations by screening more than 23,000 materials from an MXene database and then conducts self-consistent quantum transport calculations to simulate their current-voltage characteristics for channel lengths ranging from 10 nm to 3 nm.Performance of these devices has been found to meet the requirements of the international roadmap for devices and systems(IRDS)for several benchmark metrics(on current,power dissipation,delay,and subthreshold swing).The proposed balanced-mode,functional-engineered MXene transistors may lead to a realistic solution for the sub-decananometer technology scaling by enabling doping-free intrinsically low contact resistance.
基金supported by Special Funds for Major State Basic Research Project of China(No.G20000683-02)the National Natural Science Foundation of China(Grant Nos.69889601,60276033,60077004)+2 种基金Chinese 863 Plan(No.2002AA312070)Beijing Natural Science Foundation(No.4002003)Beijing Education Committee Project(No.99270602).
文摘In order to resolve the prevailing problems in conventional light-emitting diodes (LEDs), novel high-efficiency tunneling-regenerated multi-active-region (TRMAR) LEDs are proposed, which have such advantages as low heat generation, carrier overflow level and non-radiation re-combination rate and whose quantum efficiency and the output optical power can be scaled with the number of the active regions. Experiments show that the on-axis luminous intensity of TRMAR LEDs increases linearly with the number of active regions. The novel LEDs have high quantum efficiency under low current injection and their maximum on-axis luminous intensity exceeds 5 candelas at 20 mA current injection at the peak wavelength of 625 nm with a 15?angle cap.
基金supported by the National Natural Science Foundation of China(Nos.61222501 and 61335004)the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20111103110019)
文摘Two-dimensional apodized grating couplers are proposed with grating grooves realized by a series of nano- rectangles, with the feasibility of digital tailoring the equivalent refractive index of each groove in order to obtain the Gaussian output diffractive mode in order to enhance the coupling efficiency to the optical fiber. According to the requirement of leakage factor distribution for a Gaussian output profile, the corresponding effective re- fractive index of the grating groove, duty cycle, and period are designed according to the equivalent medium theory. The peak coupling efficiency of 93.1% at 1550 nm and 3 dB bandwidth of 82 nm are achieved.
基金Fellowship of AK was supported by the Core Research Grant(CRG)scheme of the Science and Engineering Research Board(SERB),Government of India,under Grant No.CRG/2020/000758.Authors strongly believe that such curiosity driven research can only foster in subsidized academic system.
文摘Magnetic skyrmions,which are topologically protected tiny spin textures,have emerged as information carriers in energy-efficient logic and memory devices.Skyrmions are commonly realized by inducing large Dzyaloshinskii–Moriya interaction(DMI)in the interface of heavy metal heterolayers.With the advent of two-dimensional magnetism,it is being envisioned to host intrinsic skyrmions in a monolayer,which will be free from any interfacial defect and stacking order.Here using high-fidelity exchange-correlation functional-based first-principles calculations,we investigate such a possibility in methodically designed non-centrosymmetric MXene structures.From a search space of about 3000 materials,our customized high-throughput computational pipeline systematically harnesses out-of-the-plane and in-plane magnetism along with strong DMI to realize typical‘unipolar’skyrmions in 78 materials and exotic‘bipolar’skyrmions in 13 materials.Micromagnetic and atomistic Monte Carlo simulations further reveal that skyrmions in some of these materials may be stable at room temperature without any external magnetic field.Our study may pave the way for the practical realization of skyrmions-based information technology.
基金UGC,Government of India for providing the necessary financial support
文摘In this paper TCAD-based simulation of a novel insulated shallow extension （ISE） cylindrical gate all around （CGAA） Schottky barrier （SB） MOSFET has been reported, to eliminate the suicidal ambipolar behavior （bias-dependent OFF state leakage current） of conventional SB-CGAA MOSFET by blocking the metal-induced gap states as well as unwanted charge sharing between source/channel and drain/channel regions. This novel structure offers low barrier height at the source and offers high ON-state current. The IoN/Iovr： of ISE-CGAA-SB-MOS- FET increases by 1177 times and offers steeper subthreshold slope （-60 mV/decade）. However a little reduction in peak cut off frequency is observed and to further improve the cut-off frequency dual metal gate architecture has been employed and a comparative assessment of single metal gate, dual metal gate, single metal gate with ISE, and dual metal gate with ISE has been presented. The improved performance of Schottky barrier CGAA MOSFET by the incorporation of ISE makes it an attractive candidate for CMOS digital circuit design. The numerical simulation is performed using the ATLAS-3D device simulator.
基金This work was partly supported by the National Natural Science Foundation of China （Grant No. 61222501） and Doctoral Program of Higher Education of China （No. 20111103110019）.
