The strain effects of the Zn1-xMgxO substrate on the bands structure of wurtzite Nb-doped Zn O bulk materials have been investigated using fi rst-principles calculations based on density functional theory. Firstly, th...The strain effects of the Zn1-xMgxO substrate on the bands structure of wurtzite Nb-doped Zn O bulk materials have been investigated using fi rst-principles calculations based on density functional theory. Firstly, the band gap increases gradually with increasing Nb contents in unstrained Nb-doped Zn O, which is consistent with the experimental results. Secondly, the band gap decreases with increasing substrate stress in Nb-doped Zn O/Zn1-xMgxO. Splitting energies between HHB（Heavy Hole Band） and LHB（Light Hole Band）, HHB and CSB（Crystal Splitting Band） in Zn0.9167Nb0.0833O/Zn1-xMgxO almost remain unchanged with increasing substrate stress, while decrease slightly in Zn0.875Nb0.125O/Zn1-xMgxO. In addition, detailed analysis of the strain effects on the effective masses of electron and hole in Nb-doped Zn O/Zn1-xMgxO is also given.展开更多
The electrostatic discharge(ESD)protection circuit widely exists in the input and output ports of CMOS digital circuits,and fast rising time electromagnetic pulse(FREMP)coupled into the device not only interacts with ...The electrostatic discharge(ESD)protection circuit widely exists in the input and output ports of CMOS digital circuits,and fast rising time electromagnetic pulse(FREMP)coupled into the device not only interacts with the CMOS circuit,but also acts on the protection circuit.This paper establishes a model of on-chip CMOS electrostatic discharge protection circuit and selects square pulse as the FREMP signals.Based on multiple physical parameter models,it depicts the distribution of the lattice temperature,current density,and electric field intensity inside the device.At the same time,this paper explores the changes of the internal devices in the circuit under the injection of fast rising time electromagnetic pulse and describes the relationship between the damage amplitude threshold and the pulse width.The results show that the ESD protection circuit has potential damage risk,and the injection of FREMP leads to irreversible heat loss inside the circuit.In addition,pulse signals with different attributes will change the damage threshold of the circuit.These results provide an important reference for further evaluation of the influence of electromagnetic environment on the chip,which is helpful to carry out the reliability enhancement research of ESD protection circuit.展开更多
Based on the k.p theory of Luttinger-Kohn and Bir-Pikus,analytical E-k solutions for the valence band of strained wurtzite ZnO materials are obtained.Strain effects on valence band edges and hole effective masses in s...Based on the k.p theory of Luttinger-Kohn and Bir-Pikus,analytical E-k solutions for the valence band of strained wurtzite ZnO materials are obtained.Strain effects on valence band edges and hole effective masses in strained wurtzite ZnO materials are also discussed.In comparison with unstrained ZnO materials,apparent movement of valence band edges such as "light hole band","heavy hole band" and "crystal splitting band" at Γ point is found in strained wurtzite ZnO materials.Moreover,effective masses of "light hole band","heavy hole band" and "crystal splitting band" for strained wurtzite ZnO materials as the function of stress are given.The analytical results can provide a theoretical foundation for the understanding of physics of strained ZnO materials and its applications with the framework for an effective mass theory.展开更多
High-power microwave damage to enhanced-mode Ga N high electron mobility transistors(HEMT)is studied considering the mechanical-electrical synergy effect due to the strong piezoelectric properties of Ga N,which has a ...High-power microwave damage to enhanced-mode Ga N high electron mobility transistors(HEMT)is studied considering the mechanical-electrical synergy effect due to the strong piezoelectric properties of Ga N,which has a wurtzite crystal structure.Based on the piezoelectric constitutive equation,the mechanical and electrical energies were equivalently coupled,and the effective numerical model was built in the simulation software.The results indicated that a part of the electrical energy was stored in the device as a form of elastic energy,causing the burnout time of Ga N HEMT to be extended.The effects of different injection voltages and frequencies were analyzed,and the results revealed that elastic energy plays a different role during the process of device damage.These results are of great significance for the design of Ga N HEMTs with better reliability in harsh electromagnetic environments and for improving their protection design.展开更多
基金Funded by the National Natural Science Foundation of China(Nos.61334003,61162025,60776034)
文摘The strain effects of the Zn1-xMgxO substrate on the bands structure of wurtzite Nb-doped Zn O bulk materials have been investigated using fi rst-principles calculations based on density functional theory. Firstly, the band gap increases gradually with increasing Nb contents in unstrained Nb-doped Zn O, which is consistent with the experimental results. Secondly, the band gap decreases with increasing substrate stress in Nb-doped Zn O/Zn1-xMgxO. Splitting energies between HHB（Heavy Hole Band） and LHB（Light Hole Band）, HHB and CSB（Crystal Splitting Band） in Zn0.9167Nb0.0833O/Zn1-xMgxO almost remain unchanged with increasing substrate stress, while decrease slightly in Zn0.875Nb0.125O/Zn1-xMgxO. In addition, detailed analysis of the strain effects on the effective masses of electron and hole in Nb-doped Zn O/Zn1-xMgxO is also given.
基金National Natural Science Foundation of China(61974116)。
文摘The electrostatic discharge(ESD)protection circuit widely exists in the input and output ports of CMOS digital circuits,and fast rising time electromagnetic pulse(FREMP)coupled into the device not only interacts with the CMOS circuit,but also acts on the protection circuit.This paper establishes a model of on-chip CMOS electrostatic discharge protection circuit and selects square pulse as the FREMP signals.Based on multiple physical parameter models,it depicts the distribution of the lattice temperature,current density,and electric field intensity inside the device.At the same time,this paper explores the changes of the internal devices in the circuit under the injection of fast rising time electromagnetic pulse and describes the relationship between the damage amplitude threshold and the pulse width.The results show that the ESD protection circuit has potential damage risk,and the injection of FREMP leads to irreversible heat loss inside the circuit.In addition,pulse signals with different attributes will change the damage threshold of the circuit.These results provide an important reference for further evaluation of the influence of electromagnetic environment on the chip,which is helpful to carry out the reliability enhancement research of ESD protection circuit.
基金supported by the National Natural Science Foundation of China (Grant Nos.60776034,61162025)the Youth Scholar Training Plan of Tibet University for Nationalities (Grant No.13myQP10)the Major Program Training Plan of Tibet University for Nationalities (Grant No.12myZP02)
文摘Based on the k.p theory of Luttinger-Kohn and Bir-Pikus,analytical E-k solutions for the valence band of strained wurtzite ZnO materials are obtained.Strain effects on valence band edges and hole effective masses in strained wurtzite ZnO materials are also discussed.In comparison with unstrained ZnO materials,apparent movement of valence band edges such as "light hole band","heavy hole band" and "crystal splitting band" at Γ point is found in strained wurtzite ZnO materials.Moreover,effective masses of "light hole band","heavy hole band" and "crystal splitting band" for strained wurtzite ZnO materials as the function of stress are given.The analytical results can provide a theoretical foundation for the understanding of physics of strained ZnO materials and its applications with the framework for an effective mass theory.
基金supported by the National Natural Science Foundation of China(Grant No.61974116)the Innovation Fund of Xidian University(Grant No.YJSJ23019)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.ZYTS23029)the China Postdoctoral Science Foundation(Grant No.2019M663927XB)。
文摘High-power microwave damage to enhanced-mode Ga N high electron mobility transistors(HEMT)is studied considering the mechanical-electrical synergy effect due to the strong piezoelectric properties of Ga N,which has a wurtzite crystal structure.Based on the piezoelectric constitutive equation,the mechanical and electrical energies were equivalently coupled,and the effective numerical model was built in the simulation software.The results indicated that a part of the electrical energy was stored in the device as a form of elastic energy,causing the burnout time of Ga N HEMT to be extended.The effects of different injection voltages and frequencies were analyzed,and the results revealed that elastic energy plays a different role during the process of device damage.These results are of great significance for the design of Ga N HEMTs with better reliability in harsh electromagnetic environments and for improving their protection design.
