A novel structure of 4H-SiC MESFETs is proposed that focuses on surface trap suppression.Characteristics of the device have been investigated based on physical models for material properties and improved trap models.B...A novel structure of 4H-SiC MESFETs is proposed that focuses on surface trap suppression.Characteristics of the device have been investigated based on physical models for material properties and improved trap models.By comparing with the performance of the well-utilized buried-gate incorporated with a field-plate （BG-FP） structure,it is shown that the proposed structure improves device properties in comprehensive aspects. A p-type spacer layer introduced in the channel layer suppresses the surface trap effect and reduces the gate-drain capacitance（C_（gd）） under a large drain voltage.A p-type spacer layer incorporated with a field-plate improves the electric field distribution on the gate edge while the spacer layer induces less C_（gd） than a conventional FP.For microwave applications,4H-SiC MESFET for the proposed structure has a larger gate-lag ratio in the saturation region due to better surface trap isolation from the conductive channel.For high power applications,the proposed structure is able to endure higher operating voltage as well.The maximum saturation current density of 460 mA/mm is yielded.Also,the gate-lag ratio under a drain voltage of 20 V is close to 90%.In addition,5%and 17.8%improvements in f_T and f_（max） are obtained compared with a BG-FP MESFET in AC simulation,respectively.Parameters and dimensions of the proposed structure are optimized to make the best of the device for microwave applications and to provide a reference for device design.展开更多
Millimeter wave technology is one of the technologies developed rapidly in recent years. The research was mainly to study the transmission of millimeter wave through textile material named silk fabric. We observed the...Millimeter wave technology is one of the technologies developed rapidly in recent years. The research was mainly to study the transmission of millimeter wave through textile material named silk fabric. We observed the phenomenon of sub-millimeter-wave transmission and reflection of the silk fabric, and concluded that with the number of silk fabric layers increasing, effect of scattering and absorption of the millimeter wave enhanced. The conclusion could be further employed in millimeter wave and THz imaging, dangerous goods inspection and other security application.展开更多
针对传统微波应用器工频高压寄生参数的问题,提出了一种采用全桥移相LCC串并联谐振网络的主电路拓扑,直接利用高频升压变压器漏感和分布电容作为LCC谐振变换器谐振元件,将寄生参数影响有效利用。设计了一个2 k W/4.6 k V全桥LCC高频谐...针对传统微波应用器工频高压寄生参数的问题,提出了一种采用全桥移相LCC串并联谐振网络的主电路拓扑,直接利用高频升压变压器漏感和分布电容作为LCC谐振变换器谐振元件,将寄生参数影响有效利用。设计了一个2 k W/4.6 k V全桥LCC高频谐振软开关变换器,应用PSIM软件对电路进行仿真分析。仿真结果验证了设计思想的正确性。展开更多
基金Project supported by the Pre-research Foundation of China(No.51308030201)the Special Foundation,China(No.9140A080509DZ0106)the Fundamental Research Funds for the Central Universities,China
文摘A novel structure of 4H-SiC MESFETs is proposed that focuses on surface trap suppression.Characteristics of the device have been investigated based on physical models for material properties and improved trap models.By comparing with the performance of the well-utilized buried-gate incorporated with a field-plate （BG-FP） structure,it is shown that the proposed structure improves device properties in comprehensive aspects. A p-type spacer layer introduced in the channel layer suppresses the surface trap effect and reduces the gate-drain capacitance（C_（gd）） under a large drain voltage.A p-type spacer layer incorporated with a field-plate improves the electric field distribution on the gate edge while the spacer layer induces less C_（gd） than a conventional FP.For microwave applications,4H-SiC MESFET for the proposed structure has a larger gate-lag ratio in the saturation region due to better surface trap isolation from the conductive channel.For high power applications,the proposed structure is able to endure higher operating voltage as well.The maximum saturation current density of 460 mA/mm is yielded.Also,the gate-lag ratio under a drain voltage of 20 V is close to 90%.In addition,5%and 17.8%improvements in f_T and f_（max） are obtained compared with a BG-FP MESFET in AC simulation,respectively.Parameters and dimensions of the proposed structure are optimized to make the best of the device for microwave applications and to provide a reference for device design.
文摘Millimeter wave technology is one of the technologies developed rapidly in recent years. The research was mainly to study the transmission of millimeter wave through textile material named silk fabric. We observed the phenomenon of sub-millimeter-wave transmission and reflection of the silk fabric, and concluded that with the number of silk fabric layers increasing, effect of scattering and absorption of the millimeter wave enhanced. The conclusion could be further employed in millimeter wave and THz imaging, dangerous goods inspection and other security application.
文摘针对传统微波应用器工频高压寄生参数的问题,提出了一种采用全桥移相LCC串并联谐振网络的主电路拓扑,直接利用高频升压变压器漏感和分布电容作为LCC谐振变换器谐振元件,将寄生参数影响有效利用。设计了一个2 k W/4.6 k V全桥LCC高频谐振软开关变换器,应用PSIM软件对电路进行仿真分析。仿真结果验证了设计思想的正确性。
