Dirac electrons possess a valley degree of freedom,which is currently under investigation as a potential information carrier.We propose an approach to generate and manipulate the valley-switching current(VSC)through A...Dirac electrons possess a valley degree of freedom,which is currently under investigation as a potential information carrier.We propose an approach to generate and manipulate the valley-switching current(VSC)through Andreev reflection using an interferometer-based superconductor hybrid junction.The interferometer comprises a ring-shaped structure formed by topological kink states in the a-T_(3) lattice via carefully designed electrostatic potentials.Our results demonstrate the feasibility of achieving a fully polarized VSC in this device without contamination from cotunneling electrons sharing the same valley as the incident electron.Furthermore,we show that control over the fully polarized VSC can be achieved by applying a nonlocal gate voltage or modifying the global parameter a.The former alters the dynamic phase of electrons while the latter provides an a-dependent Berry phase,both directly influencing quantum interference and thereby affecting performance in terms of generating and manipulating VSC,crucial for advancements in valleytronics.展开更多
We theoretically investigate the influence of off-resonant circularly polarized light field and perpendicular electric field on the quantum transport in a monolayer silicene-based normal/superconducting/normal junctio...We theoretically investigate the influence of off-resonant circularly polarized light field and perpendicular electric field on the quantum transport in a monolayer silicene-based normal/superconducting/normal junction.Owing to the tunable band structure of silicene,a pure crossed Andreev reflection process can be realized under the optical and electrical coaction.Moreover,a switch effect among the exclusive crossed Andreev reflection,the exclusive elastic cotunneling and the exclusive Andreev reflection,where the former two are the nonlocal transports and the third one is the local transport,can be obtained in our system by the modulation of the electric and light fields.In addition,the influence of the relevant parameters on the nonlocal and local transports is calculated and analyzed as well.展开更多
The Josephson effect in the superconductor/ferromagnet/superconductor （SFS） graphene Josephson junction is studied using the Dirac Bogoliubov-de Gennes （DBdG） formalism. It is shown that the SFS graphene junction ...The Josephson effect in the superconductor/ferromagnet/superconductor （SFS） graphene Josephson junction is studied using the Dirac Bogoliubov-de Gennes （DBdG） formalism. It is shown that the SFS graphene junction drives 0–π transition with the increasing of p=h0L/vF？, which captures the effects of both the exchange field and the length of the junction; the spin-down current is dominant. The 0 state is stable for p 〈 pc （critical value pc ≈ 0.80） and the π state is stable for p 〉 pc, where the free energy minima are at φg=0 and φg=π, respectively. The coexistence of the 0 and π states appears in the vicinity of pc.展开更多
Nitrogen doping is a promising way to modulate the electrical properties of graphene to realize graphene-based electronics and promise fascinating properties and applications.Herein,we report a method to noncovalently...Nitrogen doping is a promising way to modulate the electrical properties of graphene to realize graphene-based electronics and promise fascinating properties and applications.Herein,we report a method to noncovalently assembly titanium(Ⅳ) bis(ammoniumlactato) dihydroxide(Ti complex) on nitrogen-doped graphene to create a reliable hybrids which can be used as a reversible chemical induced switching.As the adsorption and desorption of Ti complex in sequential treatments,the conductance of the nitrogen-doped graphene transistors was finely modulated.Control experiments with pristine graphene clearly demonstrated the important effort of the nitrogen in this chemical sensor.Under optimized conditions,nitrogen-doped graphene transistors open up new ways to develop multifunctional devices with high sensitivity.展开更多
A simple and effective approach to improve the switching characteristics of AlGaN/AlN/GaN heterostructure field effect transistors （HFETs） by applying a voltage bias on the substrate is presented. With the increase ...A simple and effective approach to improve the switching characteristics of AlGaN/AlN/GaN heterostructure field effect transistors （HFETs） by applying a voltage bias on the substrate is presented. With the increase of the substrate bias, the OFF-state drain current is much reduced and the ON-state current keeps constant. Both the ON/OFF current ratio and the subthreshold swing are demonstrated to be greatly improved. With the thinned substrate, the improvement of the switching characteristics with the substrate bias is found to be even greater. The above improvements of the switching characteristics are attributed to the interaction between the substrate bias induced electrical field and the bulk traps in the GaN buffer layer, which reduces the conductivity of the GaN buffer layer.展开更多
The skin effect in the reversely switched dynistor （RSD） devices is investigated in this paper. Based on the plasma bipolar drift model of the RSD, the current density distributions on the chip are simulated with co...The skin effect in the reversely switched dynistor （RSD） devices is investigated in this paper. Based on the plasma bipolar drift model of the RSD, the current density distributions on the chip are simulated with considering the skin effect. The results indicate that the current density on the border can be several hundred to a thousand A/cm2 higher than that in the center of the chip. The skin effect becomes more prominent as the voltage increases and the inductance decreases in the main circuit. The phenomenon that most of a certain group of chips break over on the border has proved the existence of the skin effect.展开更多
射频前端芯片的多功能一体化设计对晶体管模型的功能及其复用能力提出了更高的要求。然而,传统模型无法实现多功能复用,导致模型参数提取步骤多、建模效率低。对此,本文提出了一种基于准物理区划分(Quasi-physical zone division, QPZD...射频前端芯片的多功能一体化设计对晶体管模型的功能及其复用能力提出了更高的要求。然而,传统模型无法实现多功能复用,导致模型参数提取步骤多、建模效率低。对此,本文提出了一种基于准物理区划分(Quasi-physical zone division, QPZD)理论的多功能的器件物理基建模方法,模型具备非线性、噪声和开关特性的表征能力。首先,本文阐述了QPZD的建模原理,分别介绍了基于QPZD的非线性、微波噪声和开关三类单功能模型理论,并基于统一的核心模型方程提出了上述模型的一体化融合方法及其多功能模型架构。其次,介绍了包括自热效应、环境温度效应和陷阱效应在内的色散效应的建模方法。最后,从晶体管在片测试验证和射频前端多功能芯片设计验证两个角度对建立的模型进行了验证。仿真实测对比结果表明,模型的非线性、噪声和开关特性的综合仿真精度大于80.33%。本文的建模方法对多功能射频前端关键芯片的全面和精准设计具有重要的指导意义。展开更多
基金supported by the National Natural Science Foundation of China(Grant No.12174051).
文摘Dirac electrons possess a valley degree of freedom,which is currently under investigation as a potential information carrier.We propose an approach to generate and manipulate the valley-switching current(VSC)through Andreev reflection using an interferometer-based superconductor hybrid junction.The interferometer comprises a ring-shaped structure formed by topological kink states in the a-T_(3) lattice via carefully designed electrostatic potentials.Our results demonstrate the feasibility of achieving a fully polarized VSC in this device without contamination from cotunneling electrons sharing the same valley as the incident electron.Furthermore,we show that control over the fully polarized VSC can be achieved by applying a nonlocal gate voltage or modifying the global parameter a.The former alters the dynamic phase of electrons while the latter provides an a-dependent Berry phase,both directly influencing quantum interference and thereby affecting performance in terms of generating and manipulating VSC,crucial for advancements in valleytronics.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11504084 and 11647164)the Natural Science Foundation for Colleges and Universities in Jiangsu Province,China(Grant Nos.18KJB140005,17KJD170004,and 16KJB140008)
文摘We theoretically investigate the influence of off-resonant circularly polarized light field and perpendicular electric field on the quantum transport in a monolayer silicene-based normal/superconducting/normal junction.Owing to the tunable band structure of silicene,a pure crossed Andreev reflection process can be realized under the optical and electrical coaction.Moreover,a switch effect among the exclusive crossed Andreev reflection,the exclusive elastic cotunneling and the exclusive Andreev reflection,where the former two are the nonlocal transports and the third one is the local transport,can be obtained in our system by the modulation of the electric and light fields.In addition,the influence of the relevant parameters on the nonlocal and local transports is calculated and analyzed as well.
基金Project supported by the National Natural Science Foundation of China(Grant No.11074088)
文摘The Josephson effect in the superconductor/ferromagnet/superconductor （SFS） graphene Josephson junction is studied using the Dirac Bogoliubov-de Gennes （DBdG） formalism. It is shown that the SFS graphene junction drives 0–π transition with the increasing of p=h0L/vF？, which captures the effects of both the exchange field and the length of the junction; the spin-down current is dominant. The 0 state is stable for p 〈 pc （critical value pc ≈ 0.80） and the π state is stable for p 〉 pc, where the free energy minima are at φg=0 and φg=π, respectively. The coexistence of the 0 and π states appears in the vicinity of pc.
文摘Nitrogen doping is a promising way to modulate the electrical properties of graphene to realize graphene-based electronics and promise fascinating properties and applications.Herein,we report a method to noncovalently assembly titanium(Ⅳ) bis(ammoniumlactato) dihydroxide(Ti complex) on nitrogen-doped graphene to create a reliable hybrids which can be used as a reversible chemical induced switching.As the adsorption and desorption of Ti complex in sequential treatments,the conductance of the nitrogen-doped graphene transistors was finely modulated.Control experiments with pristine graphene clearly demonstrated the important effort of the nitrogen in this chemical sensor.Under optimized conditions,nitrogen-doped graphene transistors open up new ways to develop multifunctional devices with high sensitivity.
基金supported by the National Natural Science Foundation of China(Grant Nos.11174182 and 61306113)the Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.20110131110005)
文摘A simple and effective approach to improve the switching characteristics of AlGaN/AlN/GaN heterostructure field effect transistors （HFETs） by applying a voltage bias on the substrate is presented. With the increase of the substrate bias, the OFF-state drain current is much reduced and the ON-state current keeps constant. Both the ON/OFF current ratio and the subthreshold swing are demonstrated to be greatly improved. With the thinned substrate, the improvement of the switching characteristics with the substrate bias is found to be even greater. The above improvements of the switching characteristics are attributed to the interaction between the substrate bias induced electrical field and the bulk traps in the GaN buffer layer, which reduces the conductivity of the GaN buffer layer.
基金supported by the National Natural Science Foundation of China under Grant No.50577028the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No.20050487044the China Postdoctoral Science Foundation under Grant No.20080440931
文摘The skin effect in the reversely switched dynistor （RSD） devices is investigated in this paper. Based on the plasma bipolar drift model of the RSD, the current density distributions on the chip are simulated with considering the skin effect. The results indicate that the current density on the border can be several hundred to a thousand A/cm2 higher than that in the center of the chip. The skin effect becomes more prominent as the voltage increases and the inductance decreases in the main circuit. The phenomenon that most of a certain group of chips break over on the border has proved the existence of the skin effect.
文摘射频前端芯片的多功能一体化设计对晶体管模型的功能及其复用能力提出了更高的要求。然而,传统模型无法实现多功能复用,导致模型参数提取步骤多、建模效率低。对此,本文提出了一种基于准物理区划分(Quasi-physical zone division, QPZD)理论的多功能的器件物理基建模方法,模型具备非线性、噪声和开关特性的表征能力。首先,本文阐述了QPZD的建模原理,分别介绍了基于QPZD的非线性、微波噪声和开关三类单功能模型理论,并基于统一的核心模型方程提出了上述模型的一体化融合方法及其多功能模型架构。其次,介绍了包括自热效应、环境温度效应和陷阱效应在内的色散效应的建模方法。最后,从晶体管在片测试验证和射频前端多功能芯片设计验证两个角度对建立的模型进行了验证。仿真实测对比结果表明,模型的非线性、噪声和开关特性的综合仿真精度大于80.33%。本文的建模方法对多功能射频前端关键芯片的全面和精准设计具有重要的指导意义。
