V-gate GaN high-electron-mobility transistors （HEMTs） are fabricated and investigated systematically. A V-shaped recess geometry is obtained using an improved Si3N4 recess etching technology. Compared with standard ...V-gate GaN high-electron-mobility transistors （HEMTs） are fabricated and investigated systematically. A V-shaped recess geometry is obtained using an improved Si3N4 recess etching technology. Compared with standard HEMTs, the fabricated V-gate HEMTs exhibit a 17% higher peak extrinsic transconductance due to a narrowed gate foot. Moreover, both the gate leakage and current dispersion are dramatically suppressed simultaneously, although a slight degradation of frequency response is observed. Based on a two-dimensional electric field simulation using Silvaco ＂ATLAS＂ for both standard HEMTs and V-gate HEMTs, the relaxation in peak electric field at the gate edge is identified as the predominant factor leading to the superior performance of V-gate HEMTs.展开更多
Post-acceleration of protons in helical coil targets driven by intense,ultrashort laser pulses can enhance ion energy by utilizing the transient current from the targets’self-discharge.The acceleration length of prot...Post-acceleration of protons in helical coil targets driven by intense,ultrashort laser pulses can enhance ion energy by utilizing the transient current from the targets’self-discharge.The acceleration length of protons can exceed a few millimeters,and the acceleration gradient is of the order of GeV/m.How to ensure the synchronization between the accelerating electric field and the protons is a crucial problem for efficient post-acceleration.In this paper,we study how the electric field mismatch induced by current dispersion affects the synchronous acceleration of protons.We propose a scheme using a two-stage helical coil to control the current dispersion.With optimized parameters,the energy gain of protons is increased by four times.Proton energy is expected to reach 45 MeV using a hundreds-of-terawatts laser,or more than 100 MeV using a petawatt laser,by controlling the current dispersion.展开更多
基金Project supported by the Program for New Century Excellent Talents in University, China (Grant No. NCET-12-0915)the National Natural Science Foundation of China (Grant Nos. 61106106 and 61204085)
文摘V-gate GaN high-electron-mobility transistors （HEMTs） are fabricated and investigated systematically. A V-shaped recess geometry is obtained using an improved Si3N4 recess etching technology. Compared with standard HEMTs, the fabricated V-gate HEMTs exhibit a 17% higher peak extrinsic transconductance due to a narrowed gate foot. Moreover, both the gate leakage and current dispersion are dramatically suppressed simultaneously, although a slight degradation of frequency response is observed. Based on a two-dimensional electric field simulation using Silvaco ＂ATLAS＂ for both standard HEMTs and V-gate HEMTs, the relaxation in peak electric field at the gate edge is identified as the predominant factor leading to the superior performance of V-gate HEMTs.
基金the NSFC Innovation Group Project(No.11921006)the National Grand Instrument Project(No.2019YFF01014402)+1 种基金the Guangdong Provincial Science and Technology Plan Project(No.2021B0909050006)the National Science Fund for Distinguished Young Scholars(No.12225501).
文摘Post-acceleration of protons in helical coil targets driven by intense,ultrashort laser pulses can enhance ion energy by utilizing the transient current from the targets’self-discharge.The acceleration length of protons can exceed a few millimeters,and the acceleration gradient is of the order of GeV/m.How to ensure the synchronization between the accelerating electric field and the protons is a crucial problem for efficient post-acceleration.In this paper,we study how the electric field mismatch induced by current dispersion affects the synchronous acceleration of protons.We propose a scheme using a two-stage helical coil to control the current dispersion.With optimized parameters,the energy gain of protons is increased by four times.Proton energy is expected to reach 45 MeV using a hundreds-of-terawatts laser,or more than 100 MeV using a petawatt laser,by controlling the current dispersion.
