28 results on '"LEI ZHAO"'
Search Results
2. Charge-mediated voltage modulation of magnetism in Hf0.5Zr0.5O2/Co multiferroic heterojunction
- Author
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Jia Chen, Peiyue Yu, Lei Zhao, Yanru Li, Meiyin Yang, Jing Xu, Jianfeng Gao, Weibing Liu, Junfeng Li, Wenwu Wang, Jin Kang, Weihai Bu, Kai Zheng, Bingjun Yang, Lei Yue, Chao Zuo, Yan Cui, and Jun Luo
- Subjects
General Physics and Astronomy - Abstract
We construct the Hall-bar device with the size of several hundred nanometers based on the HZO/Co multiferroic heterojunction. A remarkable voltage-controlled magnetism is observed in the device that possesses both ferroelectric property and perpendicular magnetic anisotropy (PMA). The nucleation field and coercivity can be modulated by voltage pulse while saturation field keeps stable. The non-volatile and reversible voltage-controlled magnetism is ascribable to interfacial charges caused by ferroelectric polarization. Meanwhile, the effective anisotropy energy density (K u) can also be controlled by voltage pulse, a decrease of 83% and increase of 28% in K u are realized under –3-V and 3-V pulses, respectively. Because the energy barrier is directly proportional to K u under a given volume, a decreased or enhanced energy barrier can be controlled by voltage pulse. Thus, it is an effective method to realize low-power and high-stability magneto-resistive random-access memory (MRAM).
- Published
- 2023
3. Efficiently enhanced energy storage performance of Ba2Bi4Ti5O18 film by co-doping Fe3+ and Ta5+ ion with larger radius
- Author
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Qiong Wu, Lei Zhao, Xinghao Chen, and Shifeng Zhao
- Subjects
General Physics and Astronomy - Abstract
We present an efficient strategy, that is the co-substitution of Fe3+ and Ta5+ ions with large radius for Ti4+ ion, to enhance energy storage performance of Ba2Bi4Ti5O18 film. For the films co-doped with Fe3+ and Ta5+ ions, the maximum polarization under the same external electric field is improved because the radius of Fe3+ and Ta5+ ions is larger than that of Ti4+ ion. Moreover, due to the composition and chemical disorder, the relaxor properties are also slightly improved, which can not be achieved by the film doped with Fe3+ ions only. What is more, for the films doped with Fe3+ ion only, the leakage current density increases greatly due to the charge imbalance, resulting in a significant decrease in breakdown strength. It is worth mentioning that the breakdown strength of Fe3+ and Ta5+ ions co-doped film does not decrease due to the charge balance. Another important point is the recoverable energy storage density of the films co-doped with Fe3+ and Ta5+ ions has been greatly improved based on the fact that the maximum external electric field does not decrease and the maximum polarization under the same external electric field increases. On top of that, the hysteresis of the polarization has also been improved. Finally, the co-doped films with Fe3+ and Ta5+ ions have good frequency and temperature stability.
- Published
- 2022
4. Characterizing entanglement in non-Hermitian chaotic systems via out-of-time ordered correlators
- Author
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Kai-Qian Huang, Wei-Lin Li, Wen-Lei Zhao, and Zhi Li
- Subjects
General Physics and Astronomy - Abstract
We investigate the quantum entanglement in a non-Hermitian kicking system. In the Hermitian case, the out-of-time ordered correlators (OTOCs) exhibit the unbounded power-law increase with time. Correspondingly, the linear entropy, which is a common measurement of entanglement, rapidly increases from zero to almost unity, indicating the formation of quantum entanglement. For strong enough non-Hermitian driving, both the OTOCs and linear entropy rapidly saturate as time evolves. Interestingly, with the increase of non-Hermitian kicking strength, the long-time averaged value of both OTOCs and linear entropy has the same transition point where they exhibit the sharp decrease from a plateau, demonstrating the disentanglment. We reveal the mechanism of disentanglement with the extension of Floquet theory to non-Hermitian systems.
- Published
- 2022
5. Design and verification of a broadband highly-efficient plasmonic circulator*
- Author
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Lei Zhao, Haipeng Li, Weihua Wang, Kui Han, Shu Zhen, Xiaopeng Shen, and Jianfei Han
- Subjects
Physics ,business.industry ,Circulator ,Physics::Optics ,General Physics and Astronomy ,02 engineering and technology ,Microwave transmission ,021001 nanoscience & nanotechnology ,01 natural sciences ,Surface plasmon polariton ,0103 physical sciences ,Broadband ,Return loss ,Insertion loss ,Equivalent circuit ,Optoelectronics ,010306 general physics ,0210 nano-technology ,business ,Plasmon - Abstract
Circulators play a significant role in radar and microwave communication systems. This paper proposes a broadband and highly efficient plasmonic circulator, which consists of spoof surface plasmon polaritons (SSPPs) waveguides and ferrite disks to support non-reciprocal mode coupling. The simulated performance of symmetrically designed circulator shows that it has an insertion loss of roughly 0.5 dB while the isolation and return loss is more than 12 dB in the frequency range of 6.0 GHz–10.0 GHz (relative bandwidth of 50%). Equivalent circuit model has been proposed to explain the operating mechanism of the plasmonic circulator. The equivalent circuit model, numerical simulations, and experimental results are consistent with each other, which demonstrates the good performance of the proposed plasmonic circulator.
- Published
- 2021
6. Chaotic dynamics of complex trajectory and its quantum signature*
- Author
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Jiaozi Wang, Pengkai Gong, Qian Wang, and Wen-Lei Zhao
- Subjects
Physics ,Classical mechanics ,Dynamics (mechanics) ,Chaotic ,General Physics and Astronomy ,Quantum signature ,Trajectory (fluid mechanics) ,Quantum chaos - Abstract
We investigate both the quantum and classical dynamics of a non-Hermitian system via a kicked rotor model with P T symmetry. For the quantum dynamics, both the mean momentum and mean square of momentum exhibit the staircase growth with time when the system parameter is in the neighborhood of the P T symmetry breaking point. If the system parameter is much larger than the P T symmetry breaking point, the accelerator mode results in the directed spreading of the wavepackets as well as the ballistic diffusion in momentum space. For the classical dynamics, the non-Hermitian kicking potential leads to the exponentially-fast increase of classical complex trajectories. As a consequence, the imaginary part of the trajectories exponentially diffuses with time, while the real part exhibits the normal diffusion. Our analytical prediction of the exponential diffusion of imaginary momentum and its breakdown time is in good agreement with numerical results. The quantum signature of the chaotic diffusion of the complex trajectories is reflected by the dynamics of the out-of-time-order correlators (OTOC). In the semiclassical regime, the rate of the exponential increase of the OTOC is equal to that of the exponential diffusion of the complex trajectories.
- Published
- 2020
7. Quantum to classical transition induced by a classically small influence*
- Author
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Wen-Lei Zhao and Quanlin Jie
- Subjects
Physics ,Quantum decoherence ,Quantum mechanics ,General Physics and Astronomy ,Quantum ,Quantum chaos - Abstract
We investigate the quantum to classical transition induced by two-particle interaction via a system of periodically kicked particles. The classical dynamics of particle 1 is almost unaffected in condition that its mass is much larger than that of particle 2. Interestingly, such classically weak influence leads to the quantum to classical transition of the dynamical behavior of particle 1. Namely, the quantum diffusion of this particle undergoes the transition from dynamical localization to the classically chaotic diffusion with the decrease of the effective Planck constant ℏ eff. The behind physics is due to the growth of entanglement in the system. The classically very weak interaction leads to the exponential decay of purity in condition that the classical dynamics of external degrees freedom is strongly chaotic.
- Published
- 2020
8. Prediction of high-mobility two-dimensional electron gas at KTaO 3 -based heterointerfaces
- Author
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Xin-Miao Zhang, Yi Li, Yufei Chen, Fu-Ning Wang, Ming-Lei Zhao, Jian Liu, Chunlei Wang, Jichao Li, Xue-Jin Wang, and Liangmo Mei
- Subjects
Materials science ,Condensed matter physics ,Interface (Java) ,General Physics and Astronomy - Published
- 2019
9. Variation of passivation behavior induced by sputtered energetic particles and thermal annealing for ITO/SiO x /Si system
- Author
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Zhongquan Ma, Jie Yang, Ming Gao, H.W. Du, Jing Xu, and Lei Zhao
- Subjects
010302 applied physics ,Materials science ,Passivation ,Annealing (metallurgy) ,Analytical chemistry ,Dangling bond ,General Physics and Astronomy ,02 engineering and technology ,Carrier lifetime ,Sputter deposition ,021001 nanoscience & nanotechnology ,01 natural sciences ,Indium tin oxide ,X-ray photoelectron spectroscopy ,Sputtering ,0103 physical sciences ,0210 nano-technology - Abstract
The damage on the atomic bonding and electronic state in a SiO x (1.4–2.3 nm)/c-Si(150 m) interface has been investigated. This occurred in the process of depositing indium tin oxide (ITO) film onto the silicon substrate by magnetron sputtering. We observe that this damage is caused by energetic particles produced in the plasma (atoms, ions, and UV light). The passivation quality and the variation on interface states of the SiO x /c-Si system were mainly studied by using effective minority carrier lifetime () measurement as a potential evaluation. The results showed that the samples' was reduced by more than 90% after ITO formation, declined from 107 s to 5 s. Following vacuum annealing at 200 C, the can be restored to 30 s. The components of Si to O bonding states at the SiO x /c-Si interface were analyzed by x-ray photoelectron spectroscopy (XPS) coupled with depth profiling. The amorphous phase of the SiO x layer and the "atomistic interleaving structure" at the SiO x /c-Si interface was observed by a transmission electron microscope (TEM). The chemical configuration of the Si–O fraction within the intermediate region is the main reason for inducing the variation of Si dangling bonds (or interface states) and effective minority carrier lifetime. After an appropriate annealing, the reduction of the Si dangling bonds between SiO x and near the c-Si surface is helpful to improve the passivation effect.
- Published
- 2017
10. Electrical property effect of oxygen vacancies in the heterojunction of LaGaO 3 / SrTiO 3
- Author
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Jian Liu, Liangmo Mei, Jichao Li, Fu-Ning Wang, Han-Zhang Liu, Wenbin Su, Ming-Lei Zhao, Chunlei Wang, and Xin-Miao Zhang
- Subjects
Property (philosophy) ,Materials science ,business.industry ,General Physics and Astronomy ,chemistry.chemical_element ,Heterojunction ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Oxygen ,chemistry ,0103 physical sciences ,Optoelectronics ,010306 general physics ,0210 nano-technology ,business - Published
- 2017
11. Improved algorithm for solving nonlinear parabolized stability equations
- Author
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Lei Zhao, Jianxin Liu, Cun-bo Zhang, and Jisheng Luo
- Subjects
Hypersonic speed ,Direct numerical simulation ,Stability (learning theory) ,General Physics and Astronomy ,Boundary (topology) ,01 natural sciences ,010305 fluids & plasmas ,Physics::Fluid Dynamics ,Nonlinear system ,Robustness (computer science) ,Distortion ,0103 physical sciences ,Applied mathematics ,Mean flow ,010306 general physics ,Mathematics - Abstract
Due to its high computational efficiency and ability to consider nonparallel and nonlinear effects, nonlinear parabolized stability equations (NPSE) approach has been widely used to study the stability and transition mechanisms. However, it often diverges in hypersonic boundary layers when the amplitude of disturbance reaches a certain level. In this study, an improved algorithm for solving NPSE is developed. In this algorithm, the mean flow distortion is included into the linear operator instead of into the nonlinear forcing terms in NPSE. An under-relaxation factor for computing the nonlinear terms is introduced during the iteration process to guarantee the robustness of the algorithm. Two case studies, the nonlinear development of stationary crossflow vortices and the fundamental resonance of the second mode disturbance in hypersonic boundary layers, are presented to validate the proposed algorithm for NPSE. Results from direct numerical simulation (DNS) are regarded as the baseline for comparison. Good agreement can be found between the proposed algorithm and DNS, which indicates the great potential of the proposed method on studying the crossflow and streamwise instability in hypersonic boundary layers.
- Published
- 2016
12. The investigation of ZnO:Al2O3/metal composite back reflectors in amorphous silicon germanium thin film solar cells
- Author
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Lei Zhao, Wenjing Wang, Baojun Yan, Chen Jingwei, Guanghong Wang, Ge Wang, and Hongwei Diao
- Subjects
Materials science ,Diffusion barrier ,Silicon ,Energy conversion efficiency ,General Physics and Astronomy ,chemistry.chemical_element ,Germanium ,law.invention ,chemistry ,law ,Solar cell ,Composite material ,Thin film ,Nichrome ,Layer (electronics) - Abstract
Different aluminum-doped ZnO (AZO)/metal composite thin films, including AZO/Ag/Al, AZO/Ag/nickel—chromium alloy (NiCr), and AZO/Ag/NiCr/Al, are utilized as the back reflectors of p—i—n amorphous silicon germanium thin film solar cells. NiCr is used as diffusion barrier layer between Ag and Al to prevent mutual diffusion, which increases the short circuit current density of solar cell. NiCr and NiCr/Al layers are used as protective layers of Ag layer against oxidation and sulfurization, the higher efficiency of solar cell is achieved. The experimental results show that the performance of a-SiGe solar cell with AZO/Ag/NiCr/Al back reflector is best. The initial conversion efficiency is achieved to be 8.05%.
- Published
- 2013
13. Potts–Ising model for simulation of polarization switching in polycrystalline ferroelectrics
- Author
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Yan-Fei, Zhang, primary, Chun-Lei, Wang, additional, Ming-Lei, Zhao, additional, Ji-Chao, Li, additional, and Rui-Zhi, Zhang, additional
- Published
- 2009
- Full Text
- View/download PDF
14. Spin pumping at the Co2FeAl0.5Si0.5/Pt interface.
- Author
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Yong, Wu, Yue-Lei, Zhao, Qiang, Xiong, Xiao-Guang, Xu, Young, Sun, Shi-Qing, Zhang, and Yong, Jiang
- Subjects
- *
FERROMAGNETIC resonance , *MAGNETIC resonance , *ELECTRIC admittance , *MAGNETIC fields , *NUCLEAR spin - Abstract
Spin pumping at the Co2FeAl0.5Si0.5/Pt and Pt/Co2FeAl0.5Si0.5 interfaces has been studied by ferromagnetic resonance technology (FMR). The spin mixing conductance of the Co2FeAl0.5Si0.5/Pt and Pt/Co2FeAl0.5Si0.5 interfaces was determined to be 3.7×1019 m−2 and 2.1×1019 m−2 by comparing the Gilbert damping in a Co2FeAl0.5Si0.5 single film, Co2FeAl0.5Si0.5/Pt bilayer film and a Pt/Co2FeAl0.5Si0.5/Pt trilayer film. Spin pumping is more efficient in the Co2FeAl0.5Si0.5/Pt bilayer film than in permalloy/Pt bilayer film. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
15. Tunable ultra-wideband terahertz filter based on three-dimensional arrays of H-shaped plasmonic crystals.
- Author
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Cai, Yuan, Shi-Lin, Xu, Jian-Quan, Yao, Xiao-Lei, Zhao, Xiao-Long, Cao, and Liang, Wu
- Subjects
SUBMILLIMETER waves ,METAMATERIALS ,COMPOSITE materials ,ELECTRIC fields ,PIEZOELECTRIC ceramics - Abstract
A face-to-face system of double-layer three-dimensional arrays of H-shaped plasmonic crystals is proposed, and its transmission and filtering properties are investigated in the terahertz regime. Simulation results show that our design has excellent filtering properties. It has an ultra-wide bandgap and passband with steep band-edges, and the transmittance of the passband and the forbidden band are very close to 1 and 0, respectively. As the distance between the two face-to-face plates increases, the resonance frequency exhibits a gradual blueshift from 0.88 THz to 1.30 THz. Therefore, we can dynamically control the bandwidths of bandgap and passband by adding a piezoelectric ceramic plate between the two crystal plates. Furthermore, the dispersion relations of modes and electric field distributions are presented to analyze the generation mechanisms of bandgaps and to explain the location of bandgaps and the frequency shift phenomenon. Due to the fact that our design can provide many resonant modes, the bandwidth of the bandgaps can be greatly broadened. This paper can serve as a valuable reference for the design of terahertz functional devices and three-dimensional terahertz metamaterials. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
16. Resisting shrinkage properties of volume holograms recorded in TiO2 nanoparticle-dispersed acrylamide-based photopolymer.
- Author
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Lei, Zhao, Jun-He, Han, Ruo-Ping, Li, Long-Ge, Wang, and Ming-Ju, Huang
- Subjects
- *
PHOTOPOLYMERS , *HOLOGRAPHIC recording , *MONOMERS , *NANOPARTICLES , *REFRACTIVE index - Abstract
A novel organic—inorganic nanoparticle—photopolymer composite system is developed, and its fundamental holographic recording characteristics are studied. In this hydrophilic TiO2-nanoparticle-dispersed acrylamide photopolymer composite system, the counter-diffusion of monomers and nanoparticles plays a fundamental and key role in hologram grating formation. The experimental results indicate that the volume shrinkage of the nanoparticle—photopolymer film during the holographic recording can be drastically reduced compared with the undoped photopolymer film. It is also found that the diffraction efficiency of the grating recorded in the nanoparticle—photopolymer film depends strongly on the concentration of the TiO2-nanoparticles, and there exists an optimal TiO2-nanoparticle-doping concentration to make the diffraction efficiency and the refractive index modulation reach their maxima. Additionally, the digital data page is stored and reconstructed in the nanoparticle—photopolymer film. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
17. Influence of a drain field plate on the forward blocking characteristics of an AlGaN/GaN high electron mobility transistor.
- Author
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Sheng-Lei, Zhao, Wei-Wei, Chen, Tong, Yue, Yi, Wang, Jun, Luo, Wei, Mao, Xiao-Hua, Ma, and Yue, Hao
- Subjects
- *
ELECTRIC properties of aluminum gallium nitride , *ELECTRIC properties of gallium nitride , *ELECTRON mobility , *BREAKDOWN voltage , *ELECTRIC fields - Abstract
In this paper, the influence of a drain field plate (FP) on the forward blocking characteristics of an AlGaN/GaN high electron mobility transistor (HEMT) is investigated. The HEMT with only a gate FP is optimized, and breakdown voltage VBR is saturated at 1085 V for gate—drain spacing LGD ≥ 8 μm. On the basis of the HEMT with a gate FP, a drain FP is added with LGD = 10 μm. For the length of the drain FP LDF ≤ 2 μm, VBR is almost kept at 1085 V, showing no degradation. When LDF exceeds 2 μm, VBR decreases obviously as LDF increases. Moreover, the larger the LDF, the larger the decrease of VBR. It is concluded that the distance between the gate edge and the drain FP edge should be larger than a certain value to prevent the drain FP from affecting the forward blocking voltage and the value should be equal to the LGD at which VBR begins to saturate in the first structure. The electric field and potential distribution are simulated and analyzed to account for the decrease of VBR. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
18. Multiple ionization of atoms and molecules impacted by very high-q fast projectiles in the strong coupling regime (q/v > 1).
- Author
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Man, Zhou, Xian-Rong, Zou, Lei, Zhao, Xi-Meng, Chen, Shi-Yao, Wang, Wang, Zhou, and Jian-Xiong, Shao
- Subjects
IONIZATION (Atomic physics) ,ATOMS ,MOLECULES ,IONS ,ATOMIC physics - Abstract
In this paper, we present a simple theoretical approach to calculate the multiple ionization of big atoms and molecules induced by very high-q fast projectiles in a strong coupling regime (q/v > 1). The results obtained from this approach are in excellent agreement with the available experimental data. A probable scenario of molecular multiple ionization by fast and very high-q projectiles is discussed. The very small computational time required here and the good agreement with the existing experimental data make it a good candidate for studying the multiple ionization of complex molecules under high linear energy transfers. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
19. Field plate structural optimization for enhancing the power gain of GaN-based HEMTs.
- Author
-
Kai, Zhang, Meng-Yi, Cao, Xiao-Yi, Lei, Sheng-Lei, Zhao, Li-Yuan, Yang, Xue-Feng, Zheng, Xiao-Hua, Ma, and Yue, Hao
- Subjects
PHOTOLITHOGRAPHY ,ELECTRODES ,PHYSICS ,SIMULATION methods & models ,ELECTRIC capacity ,MILLIMETER waves - Abstract
A novel source-connected field plate structure, featuring the same photolithography mask as the gate electrode, is proposed as an improvement over the conventional field plate (FP) techniques to enhance the frequency performance in GaN-based HEMTs. The influences of the field plate on frequency and breakdown performance are investigated simultaneously by using a two-dimensional physics-based simulation. Compared with the conventional T-gate structures with a field plate length of 1.2 μm, this field plate structure can induce the small signal power gain at 10 GHz to increase by 5-9.5 dB, which depends on the distance between source FP and dramatically shortened gate FP. This technique minimizes the parasitic capacitances, especially the gate-to-drain capacitance, showing a substantial potential for millimeter-wave, high power applications. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
20. Abnormal magnetic behaviors induced by the antisite phase boundary in La2NiMnO6.
- Author
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Yue-Lei, Zhao, Yi-Sheng, Chai, Li-Qing, Pan, and Young, Sun
- Subjects
- *
FERROMAGNETIC materials , *SEMICONDUCTORS , *POLYCRYSTALLINE semiconductors , *MAGNETIC fields , *ELECTRON paramagnetic resonance , *ANTIFERROMAGNETIC materials - Abstract
The ferromagnetic semiconductor La2NiMnO6 (LNMO) has recently received much attention due to its high Curie temperature (TC ∼ 280 K), which is close to room temperature. We prepared single-phase LNMO polycrystalline samples and investigated the temperature- and field-dependent magnetic behaviors of bulk LNMO. Between TC and T* = 300 K, we observed upward and downward deviations from the Curie—Weiss law for high and low magnetic fields, respectively. From the electron spin resonance results, we can exclude the existence of the Griffiths phase. On the contrary, our results indicate that the abnormal magnetic behaviors might be induced by antisite phase boundaries with antiferromagnetic interaction. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
21. Prediction of high-mobility two-dimensional electron gas at KTaO3-based heterointerfaces.
- Author
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Fu-Ning Wang, Ji-Chao Li, Yi Li, Xin-Miao Zhang, Xue-Jin Wang, Yu-Fei Chen, Jian Liu, Chun-Lei Wang, Ming-Lei Zhao, and Liang-Mo Mei
- Subjects
TWO-dimensional electron gas ,ELECTRON gas ,CARRIER density ,CHARGE carriers ,THIN films ,ELECTRIC fields - Abstract
First-principles calculations are performed to explore the possibility of generating the two-dimensional electron gas (2DEG) at the interface between LaGaO
3 /KTaO3 and NdGaO3 /KTaO3 (001) heterostructures. Two different models—i.e., the superlattice model and the thin film model—are used to conduct a comprehensive investigation of the origin of charge carriers. For the symmetric superlattice model, the LaGaO3 (or NdGaO3 ) film is nonpolar. The 2DEG with carrier density on the order of 1014 cm−2 originates from the Ta dxy electrons contributed by both LaGaO3 (or NdGaO3 ) and KTaO3 . For the thin film model, large polar distortions occur in the LaGaO3 and NdGaO3 layer, which entirely screens the built-in electric field and prevents electrons from transferring to the interface. Electrons of KTaO3 are accumulated at the interface, contributing to the formation of the 2DEG. All the heterostructures exhibit conducting properties regardless of the film thickness. Compared with the Ti dxy electrons in SrTiO3 -based heterostructures, the Ta dxy electrons have small effective mass and they are expected to move with higher mobility along the interface. These findings reveal the promising applications of 2DEG in novel nanoelectronic devices. [ABSTRACT FROM AUTHOR]- Published
- 2019
- Full Text
- View/download PDF
22. 1.8-kV circular AlGaN/GaN/AlGaN double-heterostructure high electron mobility transistor.
- Author
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Sheng-Lei Zhao, Zhi-Zhe Wang, Da-Zheng Chen, Mao-Jun Wang, Yang Dai, Xiao-Hua Ma, Jin-Cheng Zhang, and Yue Hao
- Subjects
- *
MODULATION-doped field-effect transistors , *HETEROSTRUCTURES , *ELECTRIC field strength , *BREAKDOWN voltage , *ELECTRIC fields - Abstract
In this paper, we present a 1.8-kV circular AlGaN/GaN/AlGaN double-heterostructure high electron mobility transistor (DH HEMT) with a gate-drain spacing . Compared with the regular DH HEMT, our circular structure has a high average breakdown electric-field strength that increases from 0.42 MV/cm to 0.96 MV/cm. The power figure of merit for the circular HEMT is as high as . The divergence of electric field lines at the gate edge and no edge effect account for the breakdown enhancement capability of the circular structure. Experiments and analysis indicate that the circular structure is an effective method to modulate the electric field. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
23. Variation of passivation behavior induced by sputtered energetic particles and thermal annealing for ITO/SiOx/Si system.
- Author
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Ming Gao, Hui-Wei Du, Jie Yang, Lei Zhao, Jing Xu, and Zhong-Quan Ma
- Subjects
SILICON ,COLLOIDS ,ELECTRON microscopes ,PHOTOELECTRON spectroscopy ,ULTRAVIOLET spectroscopy - Abstract
The damage on the atomic bonding and electronic state in a SiO
x (1.4–2.3 nm)/c-Si(150 m) interface has been investigated. This occurred in the process of depositing indium tin oxide (ITO) film onto the silicon substrate by magnetron sputtering. We observe that this damage is caused by energetic particles produced in the plasma (atoms, ions, and UV light). The passivation quality and the variation on interface states of the SiOx /c-Si system were mainly studied by using effective minority carrier lifetime () measurement as a potential evaluation. The results showed that the samples’ was reduced by more than 90% after ITO formation, declined from 107 s to 5 s. Following vacuum annealing at 200 C, the can be restored to 30 s. The components of Si to O bonding states at the SiOx /c-Si interface were analyzed by x-ray photoelectron spectroscopy (XPS) coupled with depth profiling. The amorphous phase of the SiOx layer and the “atomistic interleaving structure” at the SiOx /c-Si interface was observed by a transmission electron microscope (TEM). The chemical configuration of the Si–O fraction within the intermediate region is the main reason for inducing the variation of Si dangling bonds (or interface states) and effective minority carrier lifetime. After an appropriate annealing, the reduction of the Si dangling bonds between SiOx and near the c-Si surface is helpful to improve the passivation effect. [ABSTRACT FROM AUTHOR]- Published
- 2017
- Full Text
- View/download PDF
24. Electrical property effect of oxygen vacancies in the heterojunction of LaGaO3 /SrTiO3.
- Author
-
Fu-Ning Wang, Ji-Chao Li, Xin-Miao Zhang, Han-Zhang Liu, Jian Liu, Chun-Lei Wang, Ming-Lei Zhao, Wen-Bin Su, and Liang-Mo Mei
- Subjects
OXYGEN ,VACANCIES in crystals ,HETEROJUNCTIONS ,DENSITY functional theory ,STRONTIUM titanate ,LANTHANUM gallate - Abstract
Density functional theory within the local density approximation is used to investigate the effect of the oxygen vacancy on the LaGaO
3 /SrTiO3 (001) heterojunction. It is found that the energy favorable configuration is the oxygen vacancy located at the 3rd layer of the STO substrate, and the antiferrodistortive distortion is induced by the oxygen vacancy introduced on the SrTiO3 side. Compared with the heterojunction without introducing oxygen vacancy, the heterojunction with introducing the oxygen vacancy does not change the origin of the two-dimensional electron gas (2DEG), that is, the 2DEG still originates from the dxy electrons, which are split from the t2g states of Ti atom at interface; however the oxygen vacancy is not beneficial to the confinement of the 2DEG. The extra electrons caused by the oxygen vacancy dominantly occupy the 3dx 2−y2 orbitals of the Ti atom nearest to the oxygen vacancy, thus the density of carrier is enhanced by one order of magnitude due to the introduction of oxygen vacancy compared with the density of the ideal structure heterojunction. [ABSTRACT FROM AUTHOR]- Published
- 2017
- Full Text
- View/download PDF
25. Effect of gate length on breakdown voltage in AlGaN/GaN high-electron-mobility transistor.
- Author
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Jun Luo, Sheng-Lei Zhao, Min-Han Mi, Jin-Cheng Zhang, Xiao-Hua Ma, Yue Hao, Wei-Wei Chen, and Bin Hou
- Subjects
- *
MODULATION-doped field-effect transistors , *BREAKDOWN voltage , *POWER electronics , *IONIZATION (Atomic physics) , *ELECTRON mobility - Abstract
The effects of gate length LG on breakdown voltage VBR are investigated in AlGaN/GaN high-electron-mobility transistors (HEMTs) with LG = 1 μm∼ 20 μm. With the increase of LG, VBR is first increased, and then saturated at LG = 3 μm. For the HEMT with LG = 1 μm, breakdown voltage VBR is 117 V, and it can be enhanced to 148 V for the HEMT with LG = 3 μm. The gate length of 3 μm can alleviate the buffer-leakage-induced impact ionization compared with the gate length of 1 μm, and the suppression of the impact ionization is the reason for improving the breakdown voltage. A similar suppression of the impact ionization exists in the HEMTs with LG > 3 μm. As a result, there is no obvious difference in breakdown voltage among the HEMTs with LG = 3 μm∼20 μm, and their breakdown voltages are in a range of 140 V–156 V. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
26. Improvement of the off-state breakdown voltage with field plate and low-density drain in AlGaN/GaN high-electron mobility transistors.
- Author
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Peng Zhang, Sheng-Lei Zhao, Bin Hou, Chong Wang, Xue-Feng Zheng, Jin-Cheng Zhang, Yue Hao, and Xiao-Hua Ma
- Subjects
- *
FLUORINE , *ELECTRIC fields , *GALLIUM nitride , *ELECTRODES , *PHYSICS research - Abstract
We present an AlGaN/GaN high-electron mobility transistor (HEMT) device with both field plate (FP) and low-density drain (LDD). The LDD is realized by the injection of negatively charged fluorine (F–) ions under low power in the space between the gate and the drain electrodes. With a small-size FP and a LDD length equal to only 31% of the gate-drain spacing, the device effectively modifies the electric field distribution and achieves a breakdown voltage enhancement up to two times when compared with a device with only FP. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
27. A two-dimensional fully analytical model with polarization effect for off-state channel potential and electric field distributions of GaN-based field-plated high electron mobility transistor.
- Author
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Wei Mao, Wei-Bo She, Cui Yang, Chao Zhang, Jin-Cheng Zhang, Xiao-Hua Ma, Jin-Feng Zhang, Hong-Xia Liu, Lin-An Yang, Kai Zhang, Sheng-Lei Zhao, Yong-He Chen, Xue-Feng Zheng, and Yue Hao
- Subjects
POLARIZATION (Electricity) ,ELECTRIC fields ,ELECTRON mobility ,ELECTRIC potential ,COMPUTER simulation - Abstract
In this paper, we present a two-dimensional (2D) fully analytical model with consideration of polarization effect for the channel potential and electric field distributions of the gate field-plated high electron mobility transistor (FP-HEMT) on the basis of 2D Poisson's solution. The dependences of the channel potential and electric field distributions on drain bias, polarization charge density, FP structure parameters, AlGaN/GaN material parameters, etc. are investigated. A simple and convenient approach to designing high breakdown voltage FP-HEMTs is also proposed. The validity of this model is demonstrated by comparison with the numerical simulations with Silvaco—Atlas. The method in this paper can be extended to the development of other analytical models for different device structures, such as MIS-HEMTs, multiple-FP HETMs, slant-FP HEMTs, etc. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
28. Non-recessed-gate quasi-E-mode double heterojunction AlGaN/GaN high electron mobility transistor with high breakdown voltage.
- Author
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Min-Han Mi, Kai Zhang, Xing Chen, Sheng-Lei Zhao, Chong Wang, Jin-Cheng Zhang, Xiao-Hua Ma, and Yue Hao
- Subjects
ALUMINUM gallium nitride ,GALLIUM nitride ,HETEROJUNCTIONS ,ELECTRON mobility ,BREAKDOWN voltage ,METAL organic chemical vapor deposition - Abstract
A non-recessed-gate quasi-E-mode double heterojunction AlGaN/GaN high electron mobility transistor (quasi-E-DHEMT) with a thin barrier, high breakdown voltage and good performance of drain induced barrier lowering (DIBL) was presented. Due to the metal organic chemical vapor deposition (MOCVD) grown 9-nm undoped AlGaN barrier, the effect that the gate metal depleted the two-dimensiomal electron gas (2DEG) was greatly impressed. Therefore, the density of carriers in the channel was nearly zero. Hence, the threshold voltage was above 0 V. Quasi-E-DHEMT with 4.1-μm source-to-drain distance, 2.6-μm gate-to-drain distance, and 0.5-μm gate length showed a drain current of 260 mA/mm. The threshold voltage of this device was 0.165 V when the drain voltage was 10 V and the DIBL was 5.26 mV/V. The quasi-E-DHEMT drain leakage current at a drain voltage of 146 V and a gate voltage of −6 V was below 1 mA/mm. This indicated that the hard breakdown voltage was more than 146 V. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
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