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Improved 4H-SiC UMOSFET with super-junction shield region

Chinese Physics B 2021年第5期30卷 694-700页

作者： Pei Shen Ying Wang Xing-Ji Li Jian-Qun Yang Cheng-Hao Yu Fei Cao key laboratory of RF Circuits and Systems Ministry of EducationHangzhou Dianzi UniversityHangzhou 310018China National key laboratory of materials Behavior and evaluation technology in space Environment Harbin Institute of TechnologyHarbin 150080China

This article investigates an improved 4H-SiC trench gate metal–oxide–semiconductor field-effect transistor(MOSFET)(UMOSFET)fitted with a super-junction(SJ)shielded *** modified structure is composed of two n-type conductive pillars,three p-type conductive pillars,an oxide trench under the gate,and a light n-type current spreading layer(NCSL)under the *** n-type conductive pillars and the light n-type current spreading layer provide two paths to and promote the diffusion of a transverse current in the epitaxial layer,thus improving the specific on-resistance(R_(on,sp)).There are three p-type pillars in the modified structure,with the p-type pillars on both sides playing the same *** p-type conductive pillars relieve the electric field(E-field)in the corner of the trench ***-dimensional simulation(silvaco TCAD)indicates that Ron,sp of the modified structure,and breakdown voltage(V_(BR))are improved by 22.2%and 21.1%respectively,while the maximum figure of merit(FOM=V_(BR)^(2)/R_(on,sp)) is improved by 79.0%.Furthermore,the improved structure achieves a light smaller low gate-to-drain charge(Q_(gd))and when compared with the conventional UMOSFET(conventional-UMOS),it displays great advantages for reducing the switching energy *** advantages are due to the fact that the p-type conductive pillars and n-type conductive pillars configured under the gate provide a substantial charge balance,which also enables the charge carriers to be extracted *** the end,under the condition of the same total charge quantity,the simulation comparison of gate charge and OFF-state characteristics between Gaussdoped structure and uniform-doped structure shows that Gauss-doped structure increases the V_(BR)of the device without degradation of dynamic performance.

关键词： breakdown voltage specific on-resistance silicon carbide switching energy loss super-junction(SJ) trench gate MOSFET

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The timing of continental collision between India and Asia

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Science Bulletin 2018年第24期63卷 1649-1654页

作者： Yongfei Zheng Fuyuan Wu key laboratory of Crust-Mantle materials and environments Chinese Academy of SciencesSchool of Earth and Space SciencesUniversity of Science and Technology of China State key laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of Sciences

The timing of continental collision between India and Asia has been controversial for a long time because of the difficulty in screening isotopic ages for different types of tectonothermal event along the convergent continental boundary. After distinguishing the collisional orogeny from the precollisional accretionary orogeny and the postcollisional rifting orogeny, an age range of 55 ± 10 Ma is obtained to mark the collisional orogeny in the Early Cenozoic rather than throughout the Cenozoic. This age range provides the resolution to the timing of tectonic reactivation not only for reworking of the marginal arc systems in the Early Cenozoic but also for overprinting of granulite facies metamorphism on eclogites in the Late Cenozoic. In particular, superimposition of the rifting orogeny on both accretionary and collisional orogens in the Late Cenozoic is the key to the reactivation of both Gangdese and Himalayan orogens for contemporaneous metamorphism and magmatism at high thermal gradients. Therefore, rise of the plateau may be caused by underplating of the asthenospheric mantle for rifting orogeny in the composite Himalayan–Tibetan orogens after foundering of their roots in the Late Cenozoic.

关键词： Himalayan orogen Gangdese orogen Neo-Tethys Ocean Accretionary orogeny Collisional orogeny Rifting orogeny

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The vanadium isotopic composition of L ordinary chondrites

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Acta Geochimica 2018年第4期37卷 501-508页

作者： Yongli Xue Chun-hui Li Yuhan Qi Chuantong Zhang Bingkui Miao Fang Huang Institution of Meteorites and Planetary materials Research Guilin University of Technology key laboratory of Planetary Geological Evolution at Universities of Guangxi Province Guilin University of Technology key laboratory of Crust-Mantle materials and environments School of Earth and Space SciencesUniversity of Science and Technology of China

Stable isotopic data of meteorites are critical for understanding the evolution of terrestrial planets. In this study, we report high-precision vanadium （V） isotopic compositions of 11 unequilibrated and equilibrated L chondrites. Our samples show an average δ^51v of -1.25‰ ±0.38‰ （2SD, n = 11）, which is ,- 0.5‰ lighter than that of the bulk silicate Earth constrained by mantle peridotites. Isotopic fractionation in type 3 ordinary chondrites vary from - 1.76‰ to - 1.29‰, whereas the δ^51V of equilibrated chondrites vary from - 1.37‰ to -1.08‰. 551V of L chondrites do not correlate with thermal metamorphism, shock stage, or weathering degree. Future studies are required to explore the reason for V isotope variation in the solar system.

关键词： V isotopes L ordinary chondrites Variation

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Subduction zone geochemistry

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Geoscience Frontiers 2019年第4期10卷 1223-1254页

作者： Yong-Fei Zheng CAS key Labaratory of Crust-Mantle materials and environments School of Earth and Space Sciences University of Science and Technology of China

Crustal recycling at convergent plate boundaries is essential to mantle ***,crustal signatures in the mantle source of basaltic rocks above subduction zones were primarily incorporated in the form of liquid rather than solid *** physicochemical property of liquid phases is determined by the dehydration behavior of crustal rocks at the slab-mantle interface in subduction *** of the significant fractionation in incompatible trace elements but the full inheritance in radiogenic isotopes relative to their crustal sources,the production of liquid phases is crucial to the geochemical transfer from the subducting crust into the *** this process,the stability of specific minerals in subducting crustal rocks exerts a primary control on the enrichment of given trace elements in the liquid *** this reason,geochemically enriched oceanic basalts can be categorized into two types in terms of their trace element distribution patterns in the primitive mantle-normalized *** is island arc basalts(IAB),showing enrichment in LILE,Pb and LREE but depletion in HFSE such as Nb and Ta relative to HREE,The other is ocean island basalts(OIB),exhibiting enrichment in LILE and LREE,enrichment or non-depletion in HFSE but depletion in Pb relative to *** either types,these basalts show the enhanced enrichment of LILE and LREE with increasing their incompatibility relative to normal mid-ocean ridge basalts(MORB).The thermal regime of subduction zones can be categorized into two stages in both time and space,The first stage is characterized by compressional tectonism at low thermal *** a consequence,metamorphic dehydration of the subducting crust prevails at forearc to subarc depths due to the breakdown of hydrous minerals such as mica and amphibole in the stability field of garnet and rutile,resulting in the liberation of aqueous solutions with the trace element composition that is considerably enriched in LILE,Pb and LREE bu

关键词： Subduction zone Basalts Element mobility Geochemical differentiation Crustal metasomatism Mantle geochemistry

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Magnesium isotope geochemistry of the carbonate-silicate system in subduction zones

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National Science Review 2022年第6期9卷 23-33页

作者： Shui-Jiong Wang Shu-Guang Li State key laboratory of Geological Processes and Mineral Resources and Institute of Earth SciencesChina University of Geosciences (Beijing) CAS key laboratory of Crust-Mantle materials and environments School of Earth and Space SciencesUniversity of Science and Technology of China

The lighter magnesium(Mg) isotopic signatures observed in intraplate basalts are commonly thought to result from deep carbonate recycling, provided that the sharp difference in Mg isotopic composition between surface carbonates and the normal mantle is preserved during plate subduction. However, deep subduction of carbonates and silicates could potentially fractionate Mg isotopes and change their chemical compositions. Subducting silicate rocks that experience metamorphic dehydration lose a small amount of Mg, and preserve the original Mg isotopic signature of their protoliths. When the dehydrated fluids dissolve carbonate minerals, they may evolve into lighter Mg isotopic compositions. The solubility of carbonate minerals in fluids decreases in the order of calcite, aragonite, dolomite, magnesite and siderite, leading to selective and partial dissolution of carbonate minerals along the subduction path. At the island arc depth(70–120 km), the metamorphic fluid dissolves mainly Mg-poor calcites, and thus the fluid has difficulty modifying the Mg isotopic system of the mantle wedge and associated arc basalts. At the greater depth of the back arc system or continental margin(>150 km), the supercritical fluid can dissolve Mg-rich carbonate minerals, and its interaction with the mantle wedge could significantly imprint the light Mg isotopic signature onto the mantle rocks and derivatives. Meanwhile, the carbonate and silicate remaining within the subducting slab could experience elemental and isotopic exchange, during which the silicate can obtain a light Mg isotopic signature and high CaO/Al2O3, whereas the carbonates, particularly the Ca-rich limestone, shift Mg isotopes and Mg O contents towards higher values. If this isotopic and elemental exchange event occurs widely during crustal subduction, subducted Ca-rich carbonates can partially transform into being Mg-rich, and a portion of recycled silicates(e.g. carbonated eclogites) can have light Mg isotopic composition

关键词： magnesium isotope fractionation deep carbon cycle subduction carbonate

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New U-Pb Geochronological Constraints on Formation and Evolution of the Susong Complex Zone in the Dabie Orogen

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Acta Geologica Sinica(English Edition) 2017年第5期91卷 1915-1918页

作者： LI Yuan LIU Yican YANG Yang DENG Liangpeng CAS key laboratory of Crust-Mantle materials and environments School of Earth and Space Sciences University of Science and Technology of ChinaHefei 230026 AnhuiChina

Objective The Susong complex zone（SCZ）is a relatively lowgrade metamorphic unit mostly with an epidoteamphibolite facies,located in the southernmost part of the Dabie ***,its rock compositions,ages,

关键词： Pb New U-Pb Geochronological Constraints on Formation and Evolution of the Susong Complex Zone in the Dabie Orogen

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A perspective view on ultrahigh-pressure metamorphism and continental collision in the Dabie-Sulu orogenic belt

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Chinese Science Bulletin 2008年第20期53卷 3081-3104页

作者： ZHENG YongFei CAS key laboratory of Crust-Mantle materials and environments School of Earth and Space Sciences University of Science and Technology of China Hefei 230026 China

The study of continental deep-subduction has been one of the forefront and core subjects to advance the plate tectonics theory in the twenty-first century. The Dabie-Sulu orogenic belt in China crops out the largest lithotectonic unit containing ultrahigh-pressure metamorphic rocks in the world. Much of our understanding of the world's most enigmatic processes in continental deep-subduction zones has been deduced from various records in the Dabie-Sulu rocks. By taking these rocks as the natural laboratory, earth scientists have made seminal contributions to understanding of ultrahigh-pressure metamorphism and continental collision. This paper outlines twelve aspects of outstanding progress, including spatial distribution of the UHP metamorphic rocks, timing of the UHP metamorphism, timescale of the UHP metamorphism, the protolith nature of deeply subducted continental crust, subduction erosion and crustal detachment during continental collision, the possible depths of continental subduction, fluid activity in the continental deep-subduction zone, partial melting during continental collision, element mobility in continental deep-subduction zone, recycling of subducted continental crust, geodynamic mechanism of postcollisional magmatism, and lithospheric architecture of collision orogen. Some intriguing questions and directions are also proposed for future studies.

关键词：大陆岩石圈地壳超高压变质作用切向压缩力

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Detachment within subducted continental crust and multi-slice successive exhumation of ultrahigh-pressure metamorphic rocks: Evidence from the Dabie-Sulu orogenic belt

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Chinese Science Bulletin 2008年第20期53卷 3105-3119页

作者： LIU YiCan LI ShuGuang CAS key laboratory of Crust-Mantle materials and environments School of Earth and Space Sciences University of Science and Technology of China Hefei 230026 China

Although tectonic models were presented for exhumation of ultrahigh-pressure (UHP) metamorphic rocks during the continental collision, there is increasing evidence for the decoupling between crustal slices at various depths within deeply subducted continental crust. This lends support to the multi-slice successive exhumation model of the UHP metamorphic rocks in the Dabie-Sulu orogen. The available evidence is summarized as follows: (1) the low-grade metamorphic slices, which have geotectonic affinity to the South China Block and part of them records the Triassic metamorphism, occur in the northern margin of the Dabie-Sulu UHP metamorphic zone, suggesting decoupling of the upper crust from the underlying basement during the initial stages of continental subduction; (2) the Dabie and Sulu HP to UHP metamorphic zones comprise several HP to UHP slices, which have an increased trend of metamorphic grade from south to north but a decreased trend of peak metamorphic ages correspondingly; and (3) the Chinese Continental Science Drilling (CCSD) project at Donghai in the Sulu orogen reveals that the UHP metamorphic zone is composed of several stacked slices, which display distinctive high and low radiogenic Pb from upper to lower parts in the profile, suggesting that these UHP crustal slices were derived from the subducted upper and middle crusts, respectively. Detachment surfaces within the deeply subducted crust may occur either along an ancient fault as a channel of fluid flow, which resulted in weakening of mechanic strength of the rocks adjacent to the fault due to fluid-rock interaction, or along the low-viscosity zones which resulted from variations of geotherms and lithospheric compositions at different depths. The multi-slice successive exhumation model is different from the traditional exhumation model of the UHP metamorphic rocks in that the latter assumes the detachment of the entire subducted continental crust from the underlying mantle lithosphere and its subse

关键词：大陆潜没地质运动地壳运动超高压变质作用变质岩

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Electrical conductivity of melts: implications for conductivity anomalies in the Earth's mantle

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National Science Review 2021年第11期8卷 133-151页

作者： Bao-Hua Zhang Xuan Guo Takashi Yoshino Qun-Ke Xia key laboratory of Geoscience Big Data and Deep Resource of Zhejiang Province School of Earth Sciences Zhejiang University CAS key laboratory of Crust-Mantle materials and environments School of Earth and Space Sciences University of Science and Technology of China Institute for Planetary materials Okayama University

Magmatic liquids,including silicate and carbonate melts,are principal agents of mass and heat transfer in the Earth and terrestrial planets,and they play a crucial role in various geodynamic processes and in Earth’s *** conductivity data of these melts elucidate the cause of electrical anomalies in Earth’s interior and shed light on the melt *** the improvement in high-pressure experimental techniques and theoretical simulations,major progress has been made on this front in the past several *** review aims to summarize recent advances in experimental and theoretical studies on the electrical conductivity of silicate and carbonate melts of different compositions and volatile contents under high temperature and *** electrical conductivity of silicate melts depends strongly on temperature,pressure,water content and the ratio of non-bridging oxygens to tetrahedral cations(NBO/T).By contrast,the electrical conductivity of carbonate melts exhibits a weak dependence on temperature and pressure due to their fully depolymerized *** electrical conductivity of carbonate melts is higher than that of silicate melts by at least two orders of *** can increase electrical conductivity significantly and reduce the activation energy of silicate ***,this effect is weak for carbonate *** addition,the replacement of alkali-earth elements(Ca2+or Mg2+) with alkali elements causes a significant decrease in the electrical conductivity of carbonate melts.A distinct compensation trend is revealed for the electrical conductivity of silicate and carbonate melts under anhydrous and hydrous *** important applications of laboratory-based melt conductivity are introduced in order to understand the origin of high-conductivity anomalies in the Earth’s *** for future studies are also provided.

关键词： electrical conductivity silicate melt carbonate melt high-conductivity anomaly Earth's mantle

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Distribution,cycling and impact of water in the Earth's interior

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National Science Review 2017年第6期4卷 879-891页

作者： Huaiwei Ni Yong-Fei Zheng Zhu Mao Qin Wang Ren-Xu Chen Li Zhang CAS key laboratory of Crust-Mantle materials and environments School of Earth and Space Sciences University of Science and Technology of China School of Earth Sciences and Engineering Nanjing University

The Earth’s deep interior is a hidden water reservoir on a par with the hydrosphere that is crucial for keeping the Earth as a habitable planet. In particular, nominally anhydrous minerals(NAMs) in the silicate Earth host a significant amount of water by accommodating H point defects in their crystal lattices. Water distribution in the silicate Earth is highly heterogeneous, and the mantle transition zone may contain more water than the upper and lower mantles. Plate subduction transports surface water to various depths, with a series of hydrous minerals and NAMs serving as water carriers. Dehydration of the subducting slab produces liquid phases such as aqueous solutions and hydrous melts as a metasomatic agent of the *** melting of the metasomatic mantle domains sparks off arc volcanism, which, along with the volcanism at mid-ocean ridges and hotspots, returns water to the surface and completes the deep water cycle. There appears to have been a steady balance between hydration and dehydration of the mantle at least since the Phanerozoic. Earth’s water probably originates from a primordial portion that survived the Moon-forming giant impact, with later delivery by asteroids and comets. Water could play a critical role in initiating plate tectonics. In the modern Earth, the storage and cycling of water profoundly modulates a variety of properties and processes of the Earth’s interior, with impacts on surface environments. Notable examples include the hydrolytic weakening effect on mantle convection and plate motion, influences on phase transitions(on the solidus of mantle peridotite in particular) and dehydration embrittlement triggering intermediate-to deep-focus earthquakes. Water can reduce seismic velocity and enhance electrical conductivity, providing remote sensing methods for water distribution in the Earth’s *** unresolved issues around the deep water cycle require an integrated approach and concerted efforts from multiple disciplines.

关键词： water Earth’s interior mantle subduction partial melting

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