Photoconductive semiconductor switch(PCSS)can be applied in pulsed high power systems and microwave techniques.However,reducing the damage and increasing the lifetime of silicon carbide(SiC)PCSS are still faced severe...Photoconductive semiconductor switch(PCSS)can be applied in pulsed high power systems and microwave techniques.However,reducing the damage and increasing the lifetime of silicon carbide(SiC)PCSS are still faced severe challenges.In this study,PCSSs with various structures were prepared on 4-inch diameter,500μm thick high-purity semi-insulating 4H-SiC substrates and their on-state resistance and damage mechanisms were investigated.It was found that the PCSS of an Au/TiW/Ni electrode system annealed at 950℃had a minimum on-state resistance of 6.0Ωat 1 kV bias voltage with a 532 nm and 170 mJ pulsed laser by backside illumination single trigger.The backside illumination single trigger could reduce on-state resistance and alleviate the damage of PCSS compared to the frontside trigger when the diameter of the laser spot was larger than the channel length of PCSS.For the 200 s trigger test by a 10 Hz laser,the black branch-like ablation on Au/TiW/Ni PCSS was mainly caused by thermal stress owing to hot carriers.Replacing metal Ni with boron gallium co-doped zinc oxide(BGZO)thin films annealed at 400℃,black branch-like ablation was alleviated while concentric arc damage was obvious at the anode.The major causes of concentric arc are both pulsed laser diffraction and thermal effect.展开更多
The peculiar photoconduction in semi insulating GaAs photoconductive switch being triggered by 1064nm laser pulse is reported.The gap between two electrodes of the switch is 4mm.When it is triggered by laser pulse wi...The peculiar photoconduction in semi insulating GaAs photoconductive switch being triggered by 1064nm laser pulse is reported.The gap between two electrodes of the switch is 4mm.When it is triggered by laser pulse with energy of 0 8mJ and the pulse width of 5ns,and operated at biased electric field of 2 0 and 6 0kV/cm,both linear and nonlinear modes of the switch are observed respectively.Whereas the biased electric field adds to 9 5kV/cm,and the triggered laser is in range of 0 5～1 0mJ,the peculiar performed characteristic is observed:the switch gives a linear waveform firstly,and then after a delay time of about 20～250ns,it outputs a nonlinear waveform again.The physical mechanism of this specific phenomenon is associated with the anti site defects of semi insulating GaAs and two step single photon absorption.The delay time between linear waveform and nonlinear waveform is calculated,and the result matches the experiments.展开更多
The experiment results of ultrawide band electromagnetic radiation with DC biased GaAs photoconductive semiconductor switch combining double ridge horn antenna triggered by high repeat frequency femto-second laser pul...The experiment results of ultrawide band electromagnetic radiation with DC biased GaAs photoconductive semiconductor switch combining double ridge horn antenna triggered by high repeat frequency femto-second laser pulse are reported.The GaAs switches are insulated by solid multi-layer transparent dielectrics and the distance of two electrodes is 3mm.The electrode material of the switch is ohmic contact through alloy technics with definite proportion of Au/Ge/Ni.This switch and double ridge horn antenna are integrated and the receive antenna is connected with the test instrument.From receiving antenna,ultra fast electrical pulse of 200ps rise time and 500ps pulse width is obtained,the repetition rate of the pulse is about 82MHz and the frequency spectrum is in the range of 4.7MHz～14GHz.The radiation characteristic of the ultrafast electrical pulse is analyzed.展开更多
Experiments of a GaAs ultra\|fast Photo\|Conductive Semiconductor Switch (PCSS) are reported. Both the linear and nonlinear modes were observed when triggered by the μJ nano\|second laser. The peak current could...Experiments of a GaAs ultra\|fast Photo\|Conductive Semiconductor Switch (PCSS) are reported. Both the linear and nonlinear modes were observed when triggered by the μJ nano\|second laser. The peak current could be as high as 560A. The rise time of the current pulse responses is less than 200ps when triggered with 76MHz femto\|second laser.展开更多
A mode for the periodicity and weakening surge in semi-insulating GaAs photoconductive semiconductor switches is proposed based on the transferred-electron effect. It is shown that the periodicity and weakening surge ...A mode for the periodicity and weakening surge in semi-insulating GaAs photoconductive semiconductor switches is proposed based on the transferred-electron effect. It is shown that the periodicity and weakening surge is caused by the interaction between the self-excitation of the resonant circuit and transferred electron oscillation of the switch. The bias electric field （larger than Gunn threshold） across the switch is modulated by the AC elec-tric field,when the instantaneous bias electric field E is swinging below Gunn electric field threshold ET but grea-ter than the sustaining field Es （the minimum electric field required to support the domain） at the time of the do-main reaching the anode, and then the delayed-dipole domain mode of switch is obtained. It is the photon-activated carriers that satisfy the requirement of charge domain formation on carrier concentration and device length prod-uct of 10^12 cm^-2,and the semi-insulating GaAs photoconductive semiconductor switch is essentially a type of pho-ton-activated charge domain device.展开更多
A model for theoretical analysis of nonlinear (or high gain) mode of photoconductive semiconductor switches (PCSS's) is proposed.The switching transition of high gain PCSS's can be described with an optically...A model for theoretical analysis of nonlinear (or high gain) mode of photoconductive semiconductor switches (PCSS's) is proposed.The switching transition of high gain PCSS's can be described with an optically activated charge domain. The switching characteristics including rise time,delay and their relationship to electric field strength,optical trigger energies are discussed.The formation and radiation transit,accumulation of the charge domain are related with the triggering and sustaining phases of PCSS's,respectively.The results of the mathematical model on this mechanism agree with experimental results.展开更多
The transient resistance,voltage,and power of a nonlinear GaAs photoconductive semiconductor switch （PCSS） are presented by the finite difference formula to deal with the experiment data, based on the conversation o...The transient resistance,voltage,and power of a nonlinear GaAs photoconductive semiconductor switch （PCSS） are presented by the finite difference formula to deal with the experiment data, based on the conversation of energy in the switch circuit. This method resolves the problem of directly measuring the transient characteristics of PCSS in nonlinear mode. The curve of transient voltage shows that the average electric field of PCSS in the lock-on period is always higher than the Gunn threshold,and increases monotonically. By comparing the transient power curves of the PCSS and the electrical source,it is demonstrated directly that the power shortage leads to the PCSS from the lock-on state into the selfturnoff state,so a controllable turnoff of the PCSS in lock-on by changing the distribution of the circuit power is predicted.展开更多
Gallium arsenide (GaAs) photoconductive semiconductor switches (PCSS's) with a 1.55mm gap spacing trigged by 1553nm femtosecond fiber laser pulse is presented.The switches are biased with 3.33～10.3kV/cm and irrad...Gallium arsenide (GaAs) photoconductive semiconductor switches (PCSS's) with a 1.55mm gap spacing trigged by 1553nm femtosecond fiber laser pulse is presented.The switches are biased with 3.33～10.3kV/cm and irradiated by femtosecond fiber laser operated at a wavelength of 1553nm with pulse width of 200fs and pulse energy of 0.2nJ.The experiments show that,even if the semi-insulating GaAs photoconductive switch operates under the electrical field of 10.3kV/cm,it will be still linear response,and a clear corresponding output electric pulse with the peak voltage of 0.8mV is captured.From the weak photoconductivity on laser intensity,photoabsorption mediated by EL2 deep level defects is suggested,as the primary process for the photoconductivity.展开更多
许多少年朋友在读书写字时,由于长期形成的不规范坐姿,导致视力下降、体形发育变坏。本文介绍的提醒器能够在使用者读写坐姿不端正时,反复发出“请注意,近视!快坐正”的声音,提醒使用者及时端正坐姿。1.工作原理读写坐姿提醒器的电路如...许多少年朋友在读书写字时,由于长期形成的不规范坐姿,导致视力下降、体形发育变坏。本文介绍的提醒器能够在使用者读写坐姿不端正时,反复发出“请注意,近视!快坐正”的声音,提醒使用者及时端正坐姿。1.工作原理读写坐姿提醒器的电路如图1所示。集成电路 A、三极管 V 和扬声器 B 组成了语音发生电路。SQ 是一种玻璃水银导电开关。主要起检测位置倾斜的作用。SA 为整个电路的电源开关。展开更多
This paper reviews the recently developed optical interconnect technologies designed for scalable, low latency and high-throughput comunications within datacenters or high perforrmnce computers. The three typical arch...This paper reviews the recently developed optical interconnect technologies designed for scalable, low latency and high-throughput comunications within datacenters or high perforrmnce computers. The three typical architectures including the broadcast-and-select based Optical Shared Memory Supercomputer Interconnect System （OSMOSIS） switch, the defection routing based Data Vortex switch and the arrayed waveguide grating based Low-latency Interconnect Optical Network Switch （LIONS） switch are discussed in detail. In particular, we investigate the various Ioopback buffering technologies in LIONS and present a proof of principle testbed demonstration showing feasibility of LIONS architecture. Moreover, the performance of LIONS, Data Vortex and OSMOSIS with traditional state-of-the-art electrical switching network based on the Flattened-ButterFly （FBF） architecture in terms of throughput and latency are compared. The sinmlation based perfortmnce study shows that the latency of LIONS is almost independent of the number of input ports and does not saturate even at very high input load.展开更多
Optimized 2×2 switches based on silicon-on-insulator (SOI) were demonstrated. In the design, single mode rib waveguidesand multimode interferences (MMIs) are connected by tapered waveguides to reduce the mode cou...Optimized 2×2 switches based on silicon-on-insulator (SOI) were demonstrated. In the design, single mode rib waveguidesand multimode interferences (MMIs) are connected by tapered waveguides to reduce the mode coupling loss between thetwo types of waveguides. The average insertion loss of the switches is about -16.9 dB and the excess loss of one is measuredof -1.3 dB. The worst crosstalk is larger than 25 dB. Experimental results indicate that some of the main characteristics ofoptical switches are improved in the modified design, which is according with theoretic analysis. The novel design can beused to improve the characteristics of optical switch matrixes based on 2×2 switch units.展开更多
Circuits with switched current are described by an admittance matrix and seeking current transfers then means calculating the ratio of algebraic supplements of this matrix. As there are also graph methods of circuit a...Circuits with switched current are described by an admittance matrix and seeking current transfers then means calculating the ratio of algebraic supplements of this matrix. As there are also graph methods of circuit analysis in addition to algebraic methods, it is clearly possible in theory to carry out an analysis of the whole switched circuit in two-phase switching exclusively by the graph method as well. For this purpose it is possible to plot a Mason graph of a circuit, use transformation graphs to reduce Mason graphs for all the four phases of switching, and then plot a summary graph from the transformed graphs obtained this way. First the author draws nodes and possible branches, obtained by transformation graphs for transfers of EE （even-even） and OO （odd-odd） phases. In the next step, branches obtained by transformation graphs for EO and OE phase are drawn between these nodes, while their resulting transfer is 1 multiplied by z^1/2. This summary graph is extended by two branches from input node and to output node, the extended graph can then be interpreted by the Mason＇s relation to provide transparent current transfers. Therefore it is not necessary to compose a sum admittance matrix and to express this consequently in numbers, and so it is possible to reach the final result in a graphical way.展开更多
The adapted DC-DC converters should be smaller in size and have a small output current ripple to meet the increasing demand for low voltages with high performance and high density micro processors for several microele...The adapted DC-DC converters should be smaller in size and have a small output current ripple to meet the increasing demand for low voltages with high performance and high density micro processors for several microelectronic load applications. This paper proposes a DC-DC converter using variable on-time and variable switching frequency control enhanced constant ripple current control and reduced magnetic components. The proposed converter is realized by making the turn-offtime proportional to the on-time of the converter, according to the input and output voltage, thereby reducing the corresponding current ripple on output voltage in the continuous conduction mode. A Buck DC-DC converter using the proposed control strategy is analyzed in detail, along with some experimental results to show the performance and effectiveness of this converter.展开更多
基金National Key R&D Program of China(2021YFA0716304)Shanghai Science and Technology Programs(22511100300,23DZ2201500)。
文摘Photoconductive semiconductor switch(PCSS)can be applied in pulsed high power systems and microwave techniques.However,reducing the damage and increasing the lifetime of silicon carbide(SiC)PCSS are still faced severe challenges.In this study,PCSSs with various structures were prepared on 4-inch diameter,500μm thick high-purity semi-insulating 4H-SiC substrates and their on-state resistance and damage mechanisms were investigated.It was found that the PCSS of an Au/TiW/Ni electrode system annealed at 950℃had a minimum on-state resistance of 6.0Ωat 1 kV bias voltage with a 532 nm and 170 mJ pulsed laser by backside illumination single trigger.The backside illumination single trigger could reduce on-state resistance and alleviate the damage of PCSS compared to the frontside trigger when the diameter of the laser spot was larger than the channel length of PCSS.For the 200 s trigger test by a 10 Hz laser,the black branch-like ablation on Au/TiW/Ni PCSS was mainly caused by thermal stress owing to hot carriers.Replacing metal Ni with boron gallium co-doped zinc oxide(BGZO)thin films annealed at 400℃,black branch-like ablation was alleviated while concentric arc damage was obvious at the anode.The major causes of concentric arc are both pulsed laser diffraction and thermal effect.
文摘The peculiar photoconduction in semi insulating GaAs photoconductive switch being triggered by 1064nm laser pulse is reported.The gap between two electrodes of the switch is 4mm.When it is triggered by laser pulse with energy of 0 8mJ and the pulse width of 5ns,and operated at biased electric field of 2 0 and 6 0kV/cm,both linear and nonlinear modes of the switch are observed respectively.Whereas the biased electric field adds to 9 5kV/cm,and the triggered laser is in range of 0 5～1 0mJ,the peculiar performed characteristic is observed:the switch gives a linear waveform firstly,and then after a delay time of about 20～250ns,it outputs a nonlinear waveform again.The physical mechanism of this specific phenomenon is associated with the anti site defects of semi insulating GaAs and two step single photon absorption.The delay time between linear waveform and nonlinear waveform is calculated,and the result matches the experiments.
文摘The experiment results of ultrawide band electromagnetic radiation with DC biased GaAs photoconductive semiconductor switch combining double ridge horn antenna triggered by high repeat frequency femto-second laser pulse are reported.The GaAs switches are insulated by solid multi-layer transparent dielectrics and the distance of two electrodes is 3mm.The electrode material of the switch is ohmic contact through alloy technics with definite proportion of Au/Ge/Ni.This switch and double ridge horn antenna are integrated and the receive antenna is connected with the test instrument.From receiving antenna,ultra fast electrical pulse of 200ps rise time and 500ps pulse width is obtained,the repetition rate of the pulse is about 82MHz and the frequency spectrum is in the range of 4.7MHz～14GHz.The radiation characteristic of the ultrafast electrical pulse is analyzed.
文摘Experiments of a GaAs ultra\|fast Photo\|Conductive Semiconductor Switch (PCSS) are reported. Both the linear and nonlinear modes were observed when triggered by the μJ nano\|second laser. The peak current could be as high as 560A. The rise time of the current pulse responses is less than 200ps when triggered with 76MHz femto\|second laser.
文摘A mode for the periodicity and weakening surge in semi-insulating GaAs photoconductive semiconductor switches is proposed based on the transferred-electron effect. It is shown that the periodicity and weakening surge is caused by the interaction between the self-excitation of the resonant circuit and transferred electron oscillation of the switch. The bias electric field （larger than Gunn threshold） across the switch is modulated by the AC elec-tric field,when the instantaneous bias electric field E is swinging below Gunn electric field threshold ET but grea-ter than the sustaining field Es （the minimum electric field required to support the domain） at the time of the do-main reaching the anode, and then the delayed-dipole domain mode of switch is obtained. It is the photon-activated carriers that satisfy the requirement of charge domain formation on carrier concentration and device length prod-uct of 10^12 cm^-2,and the semi-insulating GaAs photoconductive semiconductor switch is essentially a type of pho-ton-activated charge domain device.
文摘A model for theoretical analysis of nonlinear (or high gain) mode of photoconductive semiconductor switches (PCSS's) is proposed.The switching transition of high gain PCSS's can be described with an optically activated charge domain. The switching characteristics including rise time,delay and their relationship to electric field strength,optical trigger energies are discussed.The formation and radiation transit,accumulation of the charge domain are related with the triggering and sustaining phases of PCSS's,respectively.The results of the mathematical model on this mechanism agree with experimental results.
文摘The transient resistance,voltage,and power of a nonlinear GaAs photoconductive semiconductor switch （PCSS） are presented by the finite difference formula to deal with the experiment data, based on the conversation of energy in the switch circuit. This method resolves the problem of directly measuring the transient characteristics of PCSS in nonlinear mode. The curve of transient voltage shows that the average electric field of PCSS in the lock-on period is always higher than the Gunn threshold,and increases monotonically. By comparing the transient power curves of the PCSS and the electrical source,it is demonstrated directly that the power shortage leads to the PCSS from the lock-on state into the selfturnoff state,so a controllable turnoff of the PCSS in lock-on by changing the distribution of the circuit power is predicted.
文摘Gallium arsenide (GaAs) photoconductive semiconductor switches (PCSS's) with a 1.55mm gap spacing trigged by 1553nm femtosecond fiber laser pulse is presented.The switches are biased with 3.33～10.3kV/cm and irradiated by femtosecond fiber laser operated at a wavelength of 1553nm with pulse width of 200fs and pulse energy of 0.2nJ.The experiments show that,even if the semi-insulating GaAs photoconductive switch operates under the electrical field of 10.3kV/cm,it will be still linear response,and a clear corresponding output electric pulse with the peak voltage of 0.8mV is captured.From the weak photoconductivity on laser intensity,photoabsorption mediated by EL2 deep level defects is suggested,as the primary process for the photoconductivity.
文摘许多少年朋友在读书写字时,由于长期形成的不规范坐姿,导致视力下降、体形发育变坏。本文介绍的提醒器能够在使用者读写坐姿不端正时,反复发出“请注意,近视!快坐正”的声音,提醒使用者及时端正坐姿。1.工作原理读写坐姿提醒器的电路如图1所示。集成电路 A、三极管 V 和扬声器 B 组成了语音发生电路。SQ 是一种玻璃水银导电开关。主要起检测位置倾斜的作用。SA 为整个电路的电源开关。
基金the Department of Defense under Contract No.#H88230-08-C-0202the Google Research Awards
文摘This paper reviews the recently developed optical interconnect technologies designed for scalable, low latency and high-throughput comunications within datacenters or high perforrmnce computers. The three typical architectures including the broadcast-and-select based Optical Shared Memory Supercomputer Interconnect System （OSMOSIS） switch, the defection routing based Data Vortex switch and the arrayed waveguide grating based Low-latency Interconnect Optical Network Switch （LIONS） switch are discussed in detail. In particular, we investigate the various Ioopback buffering technologies in LIONS and present a proof of principle testbed demonstration showing feasibility of LIONS architecture. Moreover, the performance of LIONS, Data Vortex and OSMOSIS with traditional state-of-the-art electrical switching network based on the Flattened-ButterFly （FBF） architecture in terms of throughput and latency are compared. The sinmlation based perfortmnce study shows that the latency of LIONS is almost independent of the number of input ports and does not saturate even at very high input load.
基金This work was supported in part by the National Science Founda-tion of China (Grant No.60577044)the Ministry of Scienceand Technology "973" Plan (No.2006CB302803)
文摘Optimized 2×2 switches based on silicon-on-insulator (SOI) were demonstrated. In the design, single mode rib waveguidesand multimode interferences (MMIs) are connected by tapered waveguides to reduce the mode coupling loss between thetwo types of waveguides. The average insertion loss of the switches is about -16.9 dB and the excess loss of one is measuredof -1.3 dB. The worst crosstalk is larger than 25 dB. Experimental results indicate that some of the main characteristics ofoptical switches are improved in the modified design, which is according with theoretic analysis. The novel design can beused to improve the characteristics of optical switch matrixes based on 2×2 switch units.
文摘Circuits with switched current are described by an admittance matrix and seeking current transfers then means calculating the ratio of algebraic supplements of this matrix. As there are also graph methods of circuit analysis in addition to algebraic methods, it is clearly possible in theory to carry out an analysis of the whole switched circuit in two-phase switching exclusively by the graph method as well. For this purpose it is possible to plot a Mason graph of a circuit, use transformation graphs to reduce Mason graphs for all the four phases of switching, and then plot a summary graph from the transformed graphs obtained this way. First the author draws nodes and possible branches, obtained by transformation graphs for transfers of EE （even-even） and OO （odd-odd） phases. In the next step, branches obtained by transformation graphs for EO and OE phase are drawn between these nodes, while their resulting transfer is 1 multiplied by z^1/2. This summary graph is extended by two branches from input node and to output node, the extended graph can then be interpreted by the Mason＇s relation to provide transparent current transfers. Therefore it is not necessary to compose a sum admittance matrix and to express this consequently in numbers, and so it is possible to reach the final result in a graphical way.
文摘The adapted DC-DC converters should be smaller in size and have a small output current ripple to meet the increasing demand for low voltages with high performance and high density micro processors for several microelectronic load applications. This paper proposes a DC-DC converter using variable on-time and variable switching frequency control enhanced constant ripple current control and reduced magnetic components. The proposed converter is realized by making the turn-offtime proportional to the on-time of the converter, according to the input and output voltage, thereby reducing the corresponding current ripple on output voltage in the continuous conduction mode. A Buck DC-DC converter using the proposed control strategy is analyzed in detail, along with some experimental results to show the performance and effectiveness of this converter.
