Dirac-vortex microcavity laser based on InAs/InGaAs quantum dots have been experimentally realized on silicon substrate.The topological laser features a large spectral range and high robustness against variations such...Dirac-vortex microcavity laser based on InAs/InGaAs quantum dots have been experimentally realized on silicon substrate.The topological laser features a large spectral range and high robustness against variations such as cavity size.展开更多
The efficiency of conventional quantum well light-emitting diodes(LEDs) decreases drastically with reducing areal size. Here we show that such a critical size scaling issue of LEDs can be addressed by utilizing N-pola...The efficiency of conventional quantum well light-emitting diodes(LEDs) decreases drastically with reducing areal size. Here we show that such a critical size scaling issue of LEDs can be addressed by utilizing N-polar In Ga N nanowires. We studied the epitaxy and performance characteristics of N-polar In Ga N nanowire LEDs grown on sapphire substrate by plasma-assisted molecular beam epitaxy. A maximum external quantum efficiency-11% was measured for LEDs with lateral dimensions as small as 750 nm directly on wafer without any packaging. The effect of electron overflow and Auger recombination on the device performance is also studied. This work provides a viable approach for achieving high-efficiency nano and micro LEDs that were not previously possible.展开更多
Micro or submicron scale light-emitting diodes(μLEDs)have been extensively studied recently as the next-generation display technology.It is desired that μLEDs exhibit high stability and efficiency,submicron pixel si...Micro or submicron scale light-emitting diodes(μLEDs)have been extensively studied recently as the next-generation display technology.It is desired that μLEDs exhibit high stability and efficiency,submicron pixel size,and potential monolithic integration with Si-based complementary metal-oxide-semiconductor(CMOS)electronics.Achieving such uLEDs,however,has remained a daunting challenge.The polar nature of Ill-nitrides causes severe wavelength/color instability with varying carrier concentrations in the active region.The etching-induced surface damages and poor material quality of high indium composition InGaN quantum wells(QWs)severely deteriorate the performance of uLEDs,particularly those emitting in the green/red wavelength.Here we report,for the first time,μLEDs grown directly on Si with submicron lateral dimensions.The μLEDs feature ultra-stable,bright green emission with negligible quantum-confined Stark effect(QCSE).Detailed elemental mapping and numerical calculations show that the QCSE is screened by introducing polarization doping in the active region,which consists of InGaN/AlGaN QWs surrounded by an AlGaN/GaN shell with a negative Al composition gradient along the c-axis.In comparison with conventional GaN barriers,AlGaN barriers are shown to effectively compensate for the tensile strain within the active region,which significantly reduces the strain distribution and results in enhanced indium incorporation without compromising the material quality.This study provides new insights and a viable path for the design,fabrication,and integration of high-performance μLEDs on Si for a broad range of applications in on-chip optical communication and emerging augmented reality/mixed reality devices,and so on.展开更多
In this work,a high-performance fiber strain sensor is fabricated by constructing a double percolated structure,consisting of carbon nanotube(CNT)/thermoplastic polyurethane(TPU)continuous phase and styrene butadiene ...In this work,a high-performance fiber strain sensor is fabricated by constructing a double percolated structure,consisting of carbon nanotube(CNT)/thermoplastic polyurethane(TPU)continuous phase and styrene butadiene styrene(SBS)phase,incompatible with TPU(CNT/TPU@SBS).Compared with other similar fiber strain sensor systems without double percolated structure,the CNT/TPU@SBS sensor achieves a lower percolation threshold(0.38 wt.%)and higher electrical conductivity.The conductivity of 1%-CNT/TPU@SBS(4.12×10^(-3) S·m^(-1))is two orders of magnitude higher than that of 1%-CNT/TPU(3.17×10^(-5) S·m^(-1))at the same CNT loading of 1 wt.%.Due to double percolated structure,the 1%-CNT/TPU@SBS sensor exhibits a wide strain detection range(0.2%-100%)and an ultra-high sensitivity(maximum gauge factor(GF)is 32411 at 100%strain).Besides,the 1%-CNT/TPU@SBS sensor shows a high linearity(R^(2)=0.97)at 0%-20%strain,relatively fast response time(214 ms),and stability(500 loading/unloading cycles).The designed sensor can efficiently monitor physiological signals and movements and identify load distribution after being woven into a sensor array,showing broad application prospects in wearable electronics.展开更多
文摘Dirac-vortex microcavity laser based on InAs/InGaAs quantum dots have been experimentally realized on silicon substrate.The topological laser features a large spectral range and high robustness against variations such as cavity size.
文摘The efficiency of conventional quantum well light-emitting diodes(LEDs) decreases drastically with reducing areal size. Here we show that such a critical size scaling issue of LEDs can be addressed by utilizing N-polar In Ga N nanowires. We studied the epitaxy and performance characteristics of N-polar In Ga N nanowire LEDs grown on sapphire substrate by plasma-assisted molecular beam epitaxy. A maximum external quantum efficiency-11% was measured for LEDs with lateral dimensions as small as 750 nm directly on wafer without any packaging. The effect of electron overflow and Auger recombination on the device performance is also studied. This work provides a viable approach for achieving high-efficiency nano and micro LEDs that were not previously possible.
基金The work was supported by NS Nanotech Inc.We also acknowledge the financial support of the University of Michigan College of Engineering and NSF grant#DMR-0723032 and technical support from the Lurie Nanofabrication Facility and Michigan Center for Materials Characterization.Y.X.acknowledges support by the National Science Foundation Graduate Research Fellowship under Grant 1841052.
文摘Micro or submicron scale light-emitting diodes(μLEDs)have been extensively studied recently as the next-generation display technology.It is desired that μLEDs exhibit high stability and efficiency,submicron pixel size,and potential monolithic integration with Si-based complementary metal-oxide-semiconductor(CMOS)electronics.Achieving such uLEDs,however,has remained a daunting challenge.The polar nature of Ill-nitrides causes severe wavelength/color instability with varying carrier concentrations in the active region.The etching-induced surface damages and poor material quality of high indium composition InGaN quantum wells(QWs)severely deteriorate the performance of uLEDs,particularly those emitting in the green/red wavelength.Here we report,for the first time,μLEDs grown directly on Si with submicron lateral dimensions.The μLEDs feature ultra-stable,bright green emission with negligible quantum-confined Stark effect(QCSE).Detailed elemental mapping and numerical calculations show that the QCSE is screened by introducing polarization doping in the active region,which consists of InGaN/AlGaN QWs surrounded by an AlGaN/GaN shell with a negative Al composition gradient along the c-axis.In comparison with conventional GaN barriers,AlGaN barriers are shown to effectively compensate for the tensile strain within the active region,which significantly reduces the strain distribution and results in enhanced indium incorporation without compromising the material quality.This study provides new insights and a viable path for the design,fabrication,and integration of high-performance μLEDs on Si for a broad range of applications in on-chip optical communication and emerging augmented reality/mixed reality devices,and so on.
基金This work was supported by the National Natural Science Foundation of China(Grant No.12102374)the National Key Research and Development Program(Grant No.2019YFE0120300)+2 种基金the Sichuan Science and Technology Program(Grant No.2021YFH0031)the International Cooperation Project of Chengdu(Grant No.2019-GH02-00054-HZ)the Innovative Research Team of SWPU(Grant No.2017CXTD01).
文摘In this work,a high-performance fiber strain sensor is fabricated by constructing a double percolated structure,consisting of carbon nanotube(CNT)/thermoplastic polyurethane(TPU)continuous phase and styrene butadiene styrene(SBS)phase,incompatible with TPU(CNT/TPU@SBS).Compared with other similar fiber strain sensor systems without double percolated structure,the CNT/TPU@SBS sensor achieves a lower percolation threshold(0.38 wt.%)and higher electrical conductivity.The conductivity of 1%-CNT/TPU@SBS(4.12×10^(-3) S·m^(-1))is two orders of magnitude higher than that of 1%-CNT/TPU(3.17×10^(-5) S·m^(-1))at the same CNT loading of 1 wt.%.Due to double percolated structure,the 1%-CNT/TPU@SBS sensor exhibits a wide strain detection range(0.2%-100%)and an ultra-high sensitivity(maximum gauge factor(GF)is 32411 at 100%strain).Besides,the 1%-CNT/TPU@SBS sensor shows a high linearity(R^(2)=0.97)at 0%-20%strain,relatively fast response time(214 ms),and stability(500 loading/unloading cycles).The designed sensor can efficiently monitor physiological signals and movements and identify load distribution after being woven into a sensor array,showing broad application prospects in wearable electronics.
