As concepts closely related to microwave absorption properties,impedance matching and phase matching were rarely combined with material parameters to regulate properties and explore related mechanisms.In this work,red...As concepts closely related to microwave absorption properties,impedance matching and phase matching were rarely combined with material parameters to regulate properties and explore related mechanisms.In this work,reduction–diffusion method was innovatively applied to synthesize rare earth alloy Y_(2)Fe_(17).In order to regulate the electromagnetic parameters of absorbers,the Y_(2)Fe_(17)N_(3-δ)particles were coated with silica(Y_(2)Fe_(17)N_(3-δ)@SiO_(2))and absorbers with different volume fractions were prepared.The relationship between impedance matching,matching thickness,and the strongest reflection loss peak(RLmin)was presented obviously.Compared to the microwave absorption properties of Y_(2)Fe_(17)N_(3-δ)/PU absorber,Y_(2)Fe_(17)N_(3-δ)@SiO_(2)/PU absorbers are more conducive to the realization of microwave absorption material standards which are thin thickness,light weight,strong absorbing intensity,and broad bandwidth.Based on microwave frequency bands,the microwave absorption properties of the absorbers were analyzed and the related parameters were listed.As an important parameter related to perfect matching,reflection factor(√ε_(r)/μ_(r))was discussed combined with microwave amplitude attenuation.According to the origin and mathematical model of bandwidth,the formula of EAB(RL<-10 dB)was derived and simplified.The calculated bandwidths agreed well with experimental results.展开更多
This paper conducts a research on modulation characteristics of blue light-emitting diodes (LEDs) used in a visible-light communication (VLC) system. Through analysis of the modulation characteristics of LEDs with dif...This paper conducts a research on modulation characteristics of blue light-emitting diodes (LEDs) used in a visible-light communication (VLC) system. Through analysis of the modulation characteristics of LEDs with different emitting sizes, we find that there is a similar linear relationship between LED’s 3dB bandwidth and the operation current density. This experiment also shows that high series resistance is one major issue that limits our LED's modulation speed. To further improve the LED bandwidth, the resistance can be reduced by optimizing device layout as well as reducing material bulk resistance. Clearly, this study provides an approach to increase the modulation bandwidth of GaN-based LEDs for VLC systems.展开更多
The effects of buried oxide（BOX） layer on the capacitance of SiGe heterojunction photo-transistor（HPT）,including the collector-substrate capacitance,the base-collector capacitance,and the base-emitter capacitance,...The effects of buried oxide（BOX） layer on the capacitance of SiGe heterojunction photo-transistor（HPT）,including the collector-substrate capacitance,the base-collector capacitance,and the base-emitter capacitance,are studied by using a silicon-on-insulator（SOI） substrate as compared with the devices on native Si substrates.By introducing the BOX layer into Si-based SiGe HPT,the maximum photo-characteristic frequency ft,0 p.of SO1-based SiGe HPT reaches up to 24.51 GHz,which is 1.5 times higher than the value obtained from Si-based SiGe HPT.In addition,the maximum optical cut-off frequency fβ,opt,namely its 3-dB bandwidth,reaches up to 1.13 GHz,improved by 1.18 times.However,with the increase of optical power or collector current,this improvement on the frequency characteristic from BOX layer becomes less dominant as confirmed by reducing the 3-dB bandwidth of SOI-based SiGe HPT which approaches to the 3-dB bandwidth of Si-based SiGe HPT at higher injection conditions.展开更多
A top-illuminated circular mesa uni-traveling-carrier photodetector（UTC-PD） is proposed in this paper. By employing Gaussian graded doping in In Ga As absorption layer and In P depleted layer, the responsivity and h...A top-illuminated circular mesa uni-traveling-carrier photodetector（UTC-PD） is proposed in this paper. By employing Gaussian graded doping in In Ga As absorption layer and In P depleted layer, the responsivity and high speed response characteristics of the device are optimized simultaneously. The responsivity up to 1.071 A/W（the external quantum efficiency of 86%） is obtained at 1550 nm with a 40-μm diameter device under 10-V reverse bias condition. Meanwhile, the dark current of 7.874 n A and the 3-d B bandwidth of 11 GHz are obtained with the same device at a reverse bias voltage of3 V.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2021YFB3501300)the National Natural Science Foundation of China(Grant No.51731001)the Fund from the State Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization’s Key Research and Development Projects。
文摘As concepts closely related to microwave absorption properties,impedance matching and phase matching were rarely combined with material parameters to regulate properties and explore related mechanisms.In this work,reduction–diffusion method was innovatively applied to synthesize rare earth alloy Y_(2)Fe_(17).In order to regulate the electromagnetic parameters of absorbers,the Y_(2)Fe_(17)N_(3-δ)particles were coated with silica(Y_(2)Fe_(17)N_(3-δ)@SiO_(2))and absorbers with different volume fractions were prepared.The relationship between impedance matching,matching thickness,and the strongest reflection loss peak(RLmin)was presented obviously.Compared to the microwave absorption properties of Y_(2)Fe_(17)N_(3-δ)/PU absorber,Y_(2)Fe_(17)N_(3-δ)@SiO_(2)/PU absorbers are more conducive to the realization of microwave absorption material standards which are thin thickness,light weight,strong absorbing intensity,and broad bandwidth.Based on microwave frequency bands,the microwave absorption properties of the absorbers were analyzed and the related parameters were listed.As an important parameter related to perfect matching,reflection factor(√ε_(r)/μ_(r))was discussed combined with microwave amplitude attenuation.According to the origin and mathematical model of bandwidth,the formula of EAB(RL<-10 dB)was derived and simplified.The calculated bandwidths agreed well with experimental results.
文摘This paper conducts a research on modulation characteristics of blue light-emitting diodes (LEDs) used in a visible-light communication (VLC) system. Through analysis of the modulation characteristics of LEDs with different emitting sizes, we find that there is a similar linear relationship between LED’s 3dB bandwidth and the operation current density. This experiment also shows that high series resistance is one major issue that limits our LED's modulation speed. To further improve the LED bandwidth, the resistance can be reduced by optimizing device layout as well as reducing material bulk resistance. Clearly, this study provides an approach to increase the modulation bandwidth of GaN-based LEDs for VLC systems.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61604106,61774012,and 61901010)the Beijing Future Chip Technology High Precision Innovation Center Research Fund,China(Grant No.KYJJ2016008)+1 种基金the Beijing Municipal Natural Science Foundation,China(Grant No.4192014)the Municipal Natural Science Foundation of Shangdong Province,China(Grant No.ZR2014FL025).
文摘The effects of buried oxide（BOX） layer on the capacitance of SiGe heterojunction photo-transistor（HPT）,including the collector-substrate capacitance,the base-collector capacitance,and the base-emitter capacitance,are studied by using a silicon-on-insulator（SOI） substrate as compared with the devices on native Si substrates.By introducing the BOX layer into Si-based SiGe HPT,the maximum photo-characteristic frequency ft,0 p.of SO1-based SiGe HPT reaches up to 24.51 GHz,which is 1.5 times higher than the value obtained from Si-based SiGe HPT.In addition,the maximum optical cut-off frequency fβ,opt,namely its 3-dB bandwidth,reaches up to 1.13 GHz,improved by 1.18 times.However,with the increase of optical power or collector current,this improvement on the frequency characteristic from BOX layer becomes less dominant as confirmed by reducing the 3-dB bandwidth of SOI-based SiGe HPT which approaches to the 3-dB bandwidth of Si-based SiGe HPT at higher injection conditions.
基金Project supported partially by the National Natural Science Foundation of China(Grant Nos.61274044 and 61077049)the National Basic Research Program of China(Grant No.2010CB327600)+3 种基金the Program of Key International Science and Technology Cooperation Projects,China(Grant No.2011RR000100)the 111 Project of China(Grant No.B07005)the Specialized Research Fund for the Doctoral Program of China(Grant No.20130005130001)the Natural Science Foundation of Beijing,China(Grant No.4132069)
文摘A top-illuminated circular mesa uni-traveling-carrier photodetector（UTC-PD） is proposed in this paper. By employing Gaussian graded doping in In Ga As absorption layer and In P depleted layer, the responsivity and high speed response characteristics of the device are optimized simultaneously. The responsivity up to 1.071 A/W（the external quantum efficiency of 86%） is obtained at 1550 nm with a 40-μm diameter device under 10-V reverse bias condition. Meanwhile, the dark current of 7.874 n A and the 3-d B bandwidth of 11 GHz are obtained with the same device at a reverse bias voltage of3 V.
