The vertical GaN-on-GaN Schottky barrier diode with boron-implanted termination was fabricated and characterized.Compared with the Schottky barrier diode(SBD)without boron-implanted termination,this SBD effectively im...The vertical GaN-on-GaN Schottky barrier diode with boron-implanted termination was fabricated and characterized.Compared with the Schottky barrier diode(SBD)without boron-implanted termination,this SBD effectively improved the breakdown voltage from 189 V to 585 V and significantly reduced the reverse leakage current by 10^5 times.In addition,a high Ion/Ioff ratio of ~10^8 was achieved by the boron-implanted technology.We used Technology Computer Aided Design(TCAD)to analyze reasons for the improved performance of the SBD with boron-implanted termination.The improved performance of diodes may be attributed to that B+could confine free carriers to suppress electron field crowding at the edge of the diode,which could improve the breakdown voltage and suppress the reverse leakage current.展开更多
The point-contact high-purity germanium detector(HPGe)has the advantages of low background,low energy threshold,and high energy resolution and can be applied in the detection of rare-event physics.However,the performa...The point-contact high-purity germanium detector(HPGe)has the advantages of low background,low energy threshold,and high energy resolution and can be applied in the detection of rare-event physics.However,the performance of HPGe must be further improved to achieve superior energy resolution,low noise,and long-term reliability.In this study,we combine computational simulations and experimental comparisons to deeply understand the passivation mechanism of Ge.The surface passivation effect is calculated and inferred from the band structure and density of interface states,and further con-firmed by the minority carrier lifetime.The first-principles method based on the density functional theory was adopted to systematically study the lattice structure,band structure,and density of state(DOS)of four different systems:Ge–H,Ge–Ge-NH 2,Ge-OH,and Ge-SiO_(x).The electronic char-acteristics of the Ge(100)unit cell with different passi-vation groups and Si/O atomic ratios were compared.This shows that H,N,and O atoms can effectively reduce the surface DOS of the Ge atoms.The passivation effect of the SiO_(x) group varied with increasing O atoms and Si/O atomic ratios.Experimentally,SiO and SiO_(2) passivation films were fabricated by electron beam evaporation on a Ge substrate,and the valence state of Si and resistivity was measured to characterize the film.The minority carrier lifetime of Ge-SiO_(2) is 21.3 ls,which is approximately quadruple that of Ge-SiO.The passivation effect and mechanism are discussed in terms of hopping conduction and surface defect density.This study builds a relationship between the passivation effect and different termination groups,and provides technical support for the potential passivation layer,which can be applied in Ge detectors with ultralow energy thresholds and especially in HPGe for rare-event physics detection experiments in future.展开更多
In this work, the field plate termination is studied for Ga2O3Schottky barrier diodes(SBDs) by simulation. The influence of field plate overlap, dielectric material and thickness on the termination electric field dist...In this work, the field plate termination is studied for Ga2O3Schottky barrier diodes(SBDs) by simulation. The influence of field plate overlap, dielectric material and thickness on the termination electric field distribution are demonstrated.It is found that the optimal thickness increases with reverse bias increasing for all the three dielectrics of SiO2, Al2O3, and HfO2. As the thickness increases, the maximum electric field intensity decreases in SiO2and Al2O3, but increases in HfO2.Furthermore, it is found that SiO2and HfO2are suitable for the 600 V rate Ga2O3SBD, and Al2O3is suitable for both600 V and 1200 V rate Ga2O3SBD. In addition, the comparison of Ga2O3SBDs between the SiC and GaN counterpart reveals that for Ga2O3, the breakdown voltage bottleneck is the dielectric. While, for SiC and GaN, the bottleneck is mainly the semiconductor itself.展开更多
The planar edge termination techniques of junction termination extension （JTE） and offset field plates and fieldlimiting rings for the 4H-SiC P i-N diode were investigated and optimized by using a two-dimensional de...The planar edge termination techniques of junction termination extension （JTE） and offset field plates and fieldlimiting rings for the 4H-SiC P i-N diode were investigated and optimized by using a two-dimensional device simulator ISE-TCAD10.0. By experimental verification, a good consistency between simulation and experiment can be observed. The results show that the reverse breakdown voltage for the 4H-SiC P-i-N diode with optimized JTE edge termination can accomplish near ideal breakdown voltage and much lower leakage current. The breakdown voltage can be near 1650 V, which achieves more than 90 percent of ideal parallel plane junction breakdown voltage and the leakage current density can be near 3 ×10^-5 A/cm2.展开更多
This paper investigates the behaviours of 4H--SiC merged PiN Schottky （MPS） rectifiers with junction termination extension （JTE） by extensive numerical simulations. The simulated results show that the present mode...This paper investigates the behaviours of 4H--SiC merged PiN Schottky （MPS） rectifiers with junction termination extension （JTE） by extensive numerical simulations. The simulated results show that the present model matches the experimental data very well. The influences of the JTE design parameters such as the doping concentration and length of the JTE on the breakdown characteristics are discussed in detail. Then the temperature sensitivity of the forward behaviour is studied in terms of the different designs of 4H--SiC MPS with JTE, which provides a particularly useful guideline for the optimal design of MPS rectifiers with JTE.展开更多
An n-GaO_(x)thin film is deposited on a single-crystal boron-doped diamond by RF magnetron sputtering to form the pn heterojunction.The n-Ga Ox thin film presents a small surface roughness and a large optical band gap...An n-GaO_(x)thin film is deposited on a single-crystal boron-doped diamond by RF magnetron sputtering to form the pn heterojunction.The n-Ga Ox thin film presents a small surface roughness and a large optical band gap of 4.85 e V.In addition,the band alignment is measured using x-ray photoelectron spectroscopy to evaluate the heterojunction properties.The GaO_(x)/diamond heterojunction shows a type-Ⅱstaggered band configuration,where the valence and conduction band offsets are 1.28 e V and 1.93 e V,respectively.These results confirm the feasibility of the use of n-GaO_(x)as a termination structure for diamond power devices.展开更多
Based on the theoretical analysis of the 4H-SiC Schottky-barrier diodes （SBDs） with field plate termination, 4H-SiC SBD with semi-insulating polycrystalline silicon （SIPOS） FP termination has been fabricated. The ...Based on the theoretical analysis of the 4H-SiC Schottky-barrier diodes （SBDs） with field plate termination, 4H-SiC SBD with semi-insulating polycrystalline silicon （SIPOS） FP termination has been fabricated. The relative dielectric con-stant of the SIPOS dielectric first used in 4H-SiC devices is 10.4, which is much higher than that of the SiO2 dielectric, leading to benefitting the performance of devices. The breakdown voltage of the fabricated SBD could reach 1200 V at leak-age current 20 μA, about 70% of the theoretical breakdown voltage. Meanwhile, both of the simulation and experimental results show that the length of the SIPOS FP termination is an important factor for structure design.展开更多
Based on the charge balance principle,an optimal impurity distribution variation of lateral doping termination(OIDVLD)and its ion-injection mask design method are proposed and verified.The comparative simulations and ...Based on the charge balance principle,an optimal impurity distribution variation of lateral doping termination(OIDVLD)and its ion-injection mask design method are proposed and verified.The comparative simulations and experiments show that OID-VLD can achieve better blocking ability and reliability than the traditional VLD(T-VLD).Vertical double diffusion MOSFET(VDMOS)with OID-VLD achieved breakdown voltage(BV)of 1684 V and passed the 168 hours 100℃-110℃-120℃-125℃high-temperature reverse bias(HTRB)test,while VDMOS with T-VLD obtained BV of 1636 V and failed in the 20 hours 120℃HTRB test.展开更多
Doping concentration and thickness of an epitaxy layer are the most essential parameters for power devices.The conventional algorithm extracts these two parameters by calculating the doping profile from its capacitanc...Doping concentration and thickness of an epitaxy layer are the most essential parameters for power devices.The conventional algorithm extracts these two parameters by calculating the doping profile from its capacitance-voltage(C-V)characteristics.Such an algorithm treats the device as a parallel-plane junction and ignores the influence of the terminations.The epitaxy layer doping concentration tends to be overestimated and the thickness underestimated.In order to obtain the epitaxy layer parameters with higher accuracy,a new algorithm applicable for devices with field limited ring(FLR)terminations is proposed in this paper.This new algorithm is also based on the C-V characteristics and considers the extension manner of the depletion region under the FLR termination.Such an extension manner depends on the design parameters of the FLR termination and is studied in detail by simulation and modeling.The analytical expressions of the device C-V characteristics and the effective doping profile are derived.More accurate epitaxy layer parameters can be extracted by fitting the effective doping profile expression to the C-V doping profile calculated from the C-V characteristics.The relationship between the horizontal extension width and the vertical depth of the depletion region is also acquired.The credibility of the new algorithm is verified by experiments.The applicability of our new algorithm to FLR/field plate combining terminations is also discussed.Our new algorithm acts as a powerful tool for analyses and improvements of power devices.展开更多
Edge termination is one of the key technologies for fabricating high voltage Schottky barrier diodes(SBDs),which could effectively reduce the peak electric field along the Schottky contact edge and enhance the breakdo...Edge termination is one of the key technologies for fabricating high voltage Schottky barrier diodes(SBDs),which could effectively reduce the peak electric field along the Schottky contact edge and enhance the breakdown voltage.We adopt a high-resistivity ring structure as the edge termination for planar GaN SBDs.The edge termination is formed by self-aligned boron implantation on the edge of devices to form a highly damaged layer.In the implant dose and energy ranges studied experimentally,the GaN SBDs show improved blocking characteristics in terms of reverse leakage current and breakdown voltage at higher implant dose or implant energy.Meanwhile,the forward turn-on characteristics of the GaN SBDs exhibit no apparent change.展开更多
Fundamental understanding of interfacial charge behaviors is of great significance for the optoelectronic and photovoltaic applications.However, the crucial roles of perovskite terminations in charge transport process...Fundamental understanding of interfacial charge behaviors is of great significance for the optoelectronic and photovoltaic applications.However, the crucial roles of perovskite terminations in charge transport processes have not been completely clear.We investigate the charge transfer behaviors of the CsPbI3/black phosphorus(BP)van der Waals heterostructure by using the density functional theory calculations with a self-energy correction.The calculations at the atomic level demonstrate the type-Ⅱ band alignments of the CsPbI3/BP heterostructure,which make electrons transfer from the perovskite side to monolayer BP.Moreover, the stronger interaction and narrower physical separation of the interfaces can lead to higher charge tunneling probabilities in the CsPbI3/BP heterostructure.Due to different electron affinities, the PbI2-terminated perovskite slab tends to collect electrons from the adjacent materials, whereas the CsI-termination prefers to inject electrons into transport materials.In addition, the interface coupling effect enhances the visible-light-region absorption of the CsPbI3/BP heterostructure.This study highlights the importance of the perovskite termination in the charge transport processes and provides theoretical guidelines to develop high-performance photovoltaic and optoelectronic devices.展开更多
High spin states of the odd-odd nucleus 122^Ⅰ have been investigated via the fusion- evaporation reaction 116^Cd（11^B, 5n） at a beam energy of 68 MeV. The yrast band is extended up to Ⅰ^π= （29＋）. The band term...High spin states of the odd-odd nucleus 122^Ⅰ have been investigated via the fusion- evaporation reaction 116^Cd（11^B, 5n） at a beam energy of 68 MeV. The yrast band is extended up to Ⅰ^π= （29＋）. The band termination at Ⅰ^π= （22^＋） reported in previous studies is confirmed and interpreted as arising from a shape change from collective prolate to noncollective oblate according to Total-Routhian-Surface （TRS） calculations. In addition, the Ⅰ^π=（29^＋） state is assigned to the [πh^11/2 （πg7/2）^2]23/2- [（vhll/2）^3 （vd5/2）^2]35/2- configuration corresponding to the full alignment of all valance nucleons outside the semi-closed shell.展开更多
Effects of initial surface termination on electrical characteristics of La2O3/Al2O3 nanolaminates deposited by atomic layer deposition are studied by conductive atomic force microscopy working in contact mode and stan...Effects of initial surface termination on electrical characteristics of La2O3/Al2O3 nanolaminates deposited by atomic layer deposition are studied by conductive atomic force microscopy working in contact mode and standard electrical characterization methods.It is found that,compared with La2O3/Al2O3 nanolaminates with LaOx as termination,lower interface trap density,less current leakage spots,and higher breakdown voltage are obtained in the La2O3/Al2O3 nanolaminates with AlOx as termination after annealing.A clear promotion of interface silicate layer is observed for La2O3/Al2O3 nanolaminates with AlOx as termination compared with LaOx as termination under the same annealing condition.In addition,the current conduction mechanism in La2O3/Al2O3 nanolaminates is considered as the Poole-Frenkel conduction.All results indicate that the AlOx is a more appropriate termination to deposit La2O3/Al2O3 nanolaminates on Si substrate,which is useful for the high-κ process development.展开更多
Silicon carbide(SiC) is a promising platform for fabricating high-voltage, high-frequency and high-temperature electronic devices such as metal oxide semiconductor field effect transistors in which many junctions or i...Silicon carbide(SiC) is a promising platform for fabricating high-voltage, high-frequency and high-temperature electronic devices such as metal oxide semiconductor field effect transistors in which many junctions or interfaces are involved. The work function(WF) plays an essential role in these devices. However, studies of the effect of conductive type and polar surfaces on the WF of SiC are limited. Here, we report the measurement of WFs of Si-and C-terminated polar surfaces for both p-type and n-type conductive 4H-SiC single crystals by scanning Kelvin probe microscopy(SKPFM). The results show that p-type SiC exhibits a higher WF than n-type SiC.The WF of a C-terminated polar surface is higher than that of a Si-terminated polar surface, which is further confirmed by first-principles calculations. By revealing this long-standing knowledge gap, our work facilitates the fabrication and development of SiC-based electronic devices, which have tremendous potential applications in electric vehicles, photovoltaics, and so on. This work also shows that SKPFM is a good method for identifying polar surfaces of SiC and other polar materials nondestructively, quickly and conveniently.展开更多
Machine learning(ML) is well suited for the prediction of high-complexity,high-dimensional problems such as those encountered in terminal ballistics.We evaluate the performance of four popular ML-based regression mode...Machine learning(ML) is well suited for the prediction of high-complexity,high-dimensional problems such as those encountered in terminal ballistics.We evaluate the performance of four popular ML-based regression models,extreme gradient boosting(XGBoost),artificial neural network(ANN),support vector regression(SVR),and Gaussian process regression(GP),on two common terminal ballistics’ problems:(a)predicting the V50ballistic limit of monolithic metallic armour impacted by small and medium calibre projectiles and fragments,and(b) predicting the depth to which a projectile will penetrate a target of semi-infinite thickness.To achieve this we utilise two datasets,each consisting of approximately 1000samples,collated from public release sources.We demonstrate that all four model types provide similarly excellent agreement when interpolating within the training data and diverge when extrapolating outside this range.Although extrapolation is not advisable for ML-based regression models,for applications such as lethality/survivability analysis,such capability is required.To circumvent this,we implement expert knowledge and physics-based models via enforced monotonicity,as a Gaussian prior mean,and through a modified loss function.The physics-informed models demonstrate improved performance over both classical physics-based models and the basic ML regression models,providing an ability to accurately fit experimental data when it is available and then revert to the physics-based model when not.The resulting models demonstrate high levels of predictive accuracy over a very wide range of projectile types,target materials and thicknesses,and impact conditions significantly more diverse than that achievable from any existing analytical approach.Compared with numerical analysis tools such as finite element solvers the ML models run orders of magnitude faster.We provide some general guidelines throughout for the development,application,and reporting of ML models in terminal ballistics problems.展开更多
We evaluate an adaptive optimisation methodology,Bayesian optimisation(BO),for designing a minimum weight explosive reactive armour(ERA)for protection against a surrogate medium calibre kinetic energy(KE)long rod proj...We evaluate an adaptive optimisation methodology,Bayesian optimisation(BO),for designing a minimum weight explosive reactive armour(ERA)for protection against a surrogate medium calibre kinetic energy(KE)long rod projectile and surrogate shaped charge(SC)warhead.We perform the optimisation using a conventional BO methodology and compare it with a conventional trial-and-error approach from a human expert.A third approach,utilising a novel human-machine teaming framework for BO is also evaluated.Data for the optimisation is generated using numerical simulations that are demonstrated to provide reasonable qualitative agreement with reference experiments.The human-machine teaming methodology is shown to identify the optimum ERA design in the fewest number of evaluations,outperforming both the stand-alone human and stand-alone BO methodologies.From a design space of almost 1800 configurations the human-machine teaming approach identifies the minimum weight ERA design in 10 samples.展开更多
We investigate the behavior of edge modes in the presence of different edge terminations and long-range(LR)hopping.Here,we mainly focus on such model crystals with two different types of structures(type I:“…-P-Q-P-Q...We investigate the behavior of edge modes in the presence of different edge terminations and long-range(LR)hopping.Here,we mainly focus on such model crystals with two different types of structures(type I:“…-P-Q-P-Q-…”and type II:“…=P-Q=P-Q=…”),where P and Q represent crystal lines(CLs),while the symbols“-”and“=”denote the distance between the nearest neighbor(NN)CLs.Based on the lattice model Hamiltonian with LR hopping,the existence of edge modes is determined analytically by using the transfer matrix method(TMM)when different edge terminals are taken into consideration.Our findings are consistent with the numerical results obtained by the exact diagonalization method.We also notice that edge modes can exhibit different behaviors under different edge terminals.Our result is helpful in solving novel edge modes in honeycomb crystalline graphene and transition metal dichalcogenides with different edge terminals.展开更多
Considering the uncertainty of the speed of horizontal transportation equipment,a cooperative scheduling model of multiple equipment resources in the automated container terminal was constructed to minimize the comple...Considering the uncertainty of the speed of horizontal transportation equipment,a cooperative scheduling model of multiple equipment resources in the automated container terminal was constructed to minimize the completion time,thus improving the loading and unloading efficiencies of automated container terminals.The proposed model integrated the two loading and unloading processes of“double-trolley quay crane+AGV+ARMG”and“single-trolley quay crane+container truck+ARMG”and then designed the simulated annealing particle swarm algorithm to solve the model.By comparing the results of the particle swarm algorithm and genetic algorithm,the algorithm designed in this paper could effectively improve the global and local space search capability of finding the optimal solution.Furthermore,the results showed that the proposed method of collaborative scheduling of multiple equipment resources in automated terminals considering hybrid processes effectively improved the loading and unloading efficiencies of automated container terminals.The findings of this study provide a reference for the improvement of loading and unloading processes as well as coordinated scheduling in automated terminals.展开更多
Dear Editor,Ferroptosis,an iron-dependent form of cell death driven by overwhelming lipid peroxidation,represents a vulnerability in cancers,and therapeutic strategies to further potentiate ferroptosis hold great pote...Dear Editor,Ferroptosis,an iron-dependent form of cell death driven by overwhelming lipid peroxidation,represents a vulnerability in cancers,and therapeutic strategies to further potentiate ferroptosis hold great potential for melanoma treatment.展开更多
This paper proposes an adaptive predefined-time terminal sliding mode control(APTSMC)scheme for attitude tracking control of a quadrotor.To create this,an adaptive predefined-time stability controller based on a termi...This paper proposes an adaptive predefined-time terminal sliding mode control(APTSMC)scheme for attitude tracking control of a quadrotor.To create this,an adaptive predefined-time stability controller based on a terminal sliding mode is constructed.The upper bound of convergence time in the proposed scheme can be adjusted by the explicit parameters during the design process of the controller.In addition,it is proved that the attitude tracking error will converge within two periods of the preset time.These two periods are set between two ranges:From the initial values to the sliding mode surface and from the sliding mode surface to the region near the origin.Furthermore,an adaptive law is adopted to eliminate unknown external disturbances and the effects of the uncertainties in the quadrotor model,so it is unnecessary to require the prior knowledge of the upper bound of the perturbations.Simulation results are produced and comparative case studies are carried out to demonstrate that the proposed scheme has faster convergence speed and smaller tracking errors.展开更多
基金Project supported by the National Key R&D Program of China(Grant No.2017YFB0404100)Science and Technology Planning Project of Guangdong Province,China(Grant No.2017B010112001)。
文摘The vertical GaN-on-GaN Schottky barrier diode with boron-implanted termination was fabricated and characterized.Compared with the Schottky barrier diode(SBD)without boron-implanted termination,this SBD effectively improved the breakdown voltage from 189 V to 585 V and significantly reduced the reverse leakage current by 10^5 times.In addition,a high Ion/Ioff ratio of ~10^8 was achieved by the boron-implanted technology.We used Technology Computer Aided Design(TCAD)to analyze reasons for the improved performance of the SBD with boron-implanted termination.The improved performance of diodes may be attributed to that B+could confine free carriers to suppress electron field crowding at the edge of the diode,which could improve the breakdown voltage and suppress the reverse leakage current.
基金supported by the National Natural Science Foundation of China Youth Fund(No.12005017)。
文摘The point-contact high-purity germanium detector(HPGe)has the advantages of low background,low energy threshold,and high energy resolution and can be applied in the detection of rare-event physics.However,the performance of HPGe must be further improved to achieve superior energy resolution,low noise,and long-term reliability.In this study,we combine computational simulations and experimental comparisons to deeply understand the passivation mechanism of Ge.The surface passivation effect is calculated and inferred from the band structure and density of interface states,and further con-firmed by the minority carrier lifetime.The first-principles method based on the density functional theory was adopted to systematically study the lattice structure,band structure,and density of state(DOS)of four different systems:Ge–H,Ge–Ge-NH 2,Ge-OH,and Ge-SiO_(x).The electronic char-acteristics of the Ge(100)unit cell with different passi-vation groups and Si/O atomic ratios were compared.This shows that H,N,and O atoms can effectively reduce the surface DOS of the Ge atoms.The passivation effect of the SiO_(x) group varied with increasing O atoms and Si/O atomic ratios.Experimentally,SiO and SiO_(2) passivation films were fabricated by electron beam evaporation on a Ge substrate,and the valence state of Si and resistivity was measured to characterize the film.The minority carrier lifetime of Ge-SiO_(2) is 21.3 ls,which is approximately quadruple that of Ge-SiO.The passivation effect and mechanism are discussed in terms of hopping conduction and surface defect density.This study builds a relationship between the passivation effect and different termination groups,and provides technical support for the potential passivation layer,which can be applied in Ge detectors with ultralow energy thresholds and especially in HPGe for rare-event physics detection experiments in future.
基金Project supported by the Research Fund of Low Cost Fabrication of GaN Power Devices and System Integration,China(Grant No.JCYJ20160226192639004)the Research Fund of AlGaN HEMT MEMS Sensor for Work in Extreme Environment,China(Grant No.JCYJ20170412153356899)the Research Fund of Reliability Mechanism and Circuit Simulation of GaN HEMT,China(Grant No.2017A050506002)
文摘In this work, the field plate termination is studied for Ga2O3Schottky barrier diodes(SBDs) by simulation. The influence of field plate overlap, dielectric material and thickness on the termination electric field distribution are demonstrated.It is found that the optimal thickness increases with reverse bias increasing for all the three dielectrics of SiO2, Al2O3, and HfO2. As the thickness increases, the maximum electric field intensity decreases in SiO2and Al2O3, but increases in HfO2.Furthermore, it is found that SiO2and HfO2are suitable for the 600 V rate Ga2O3SBD, and Al2O3is suitable for both600 V and 1200 V rate Ga2O3SBD. In addition, the comparison of Ga2O3SBDs between the SiC and GaN counterpart reveals that for Ga2O3, the breakdown voltage bottleneck is the dielectric. While, for SiC and GaN, the bottleneck is mainly the semiconductor itself.
基金Project supported by the Science and Technology Foundation of Hunan Province of China (Grant No. 2008FJ3102)
文摘The planar edge termination techniques of junction termination extension （JTE） and offset field plates and fieldlimiting rings for the 4H-SiC P i-N diode were investigated and optimized by using a two-dimensional device simulator ISE-TCAD10.0. By experimental verification, a good consistency between simulation and experiment can be observed. The results show that the reverse breakdown voltage for the 4H-SiC P-i-N diode with optimized JTE edge termination can accomplish near ideal breakdown voltage and much lower leakage current. The breakdown voltage can be near 1650 V, which achieves more than 90 percent of ideal parallel plane junction breakdown voltage and the leakage current density can be near 3 ×10^-5 A/cm2.
基金Project supported by Shaanxi 13115 Innovation Engineering Foundation (Grant No. 2008ZDKG-30)Pre-research Project(Grant No. 51308040302)
文摘This paper investigates the behaviours of 4H--SiC merged PiN Schottky （MPS） rectifiers with junction termination extension （JTE） by extensive numerical simulations. The simulated results show that the present model matches the experimental data very well. The influences of the JTE design parameters such as the doping concentration and length of the JTE on the breakdown characteristics are discussed in detail. Then the temperature sensitivity of the forward behaviour is studied in terms of the different designs of 4H--SiC MPS with JTE, which provides a particularly useful guideline for the optimal design of MPS rectifiers with JTE.
基金Project supported by the Key-Area Research and Development Program of Guangdong Province,China(Grant No.2020B0101690001)。
文摘An n-GaO_(x)thin film is deposited on a single-crystal boron-doped diamond by RF magnetron sputtering to form the pn heterojunction.The n-Ga Ox thin film presents a small surface roughness and a large optical band gap of 4.85 e V.In addition,the band alignment is measured using x-ray photoelectron spectroscopy to evaluate the heterojunction properties.The GaO_(x)/diamond heterojunction shows a type-Ⅱstaggered band configuration,where the valence and conduction band offsets are 1.28 e V and 1.93 e V,respectively.These results confirm the feasibility of the use of n-GaO_(x)as a termination structure for diamond power devices.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61234006 and 61274079)the Key Specific Projects of Ministry of Education of China(Grant No.625010101)the Science Project of State Grid,China(Grant No.SGRI-WD-71-13-004)
文摘Based on the theoretical analysis of the 4H-SiC Schottky-barrier diodes （SBDs） with field plate termination, 4H-SiC SBD with semi-insulating polycrystalline silicon （SIPOS） FP termination has been fabricated. The relative dielectric con-stant of the SIPOS dielectric first used in 4H-SiC devices is 10.4, which is much higher than that of the SiO2 dielectric, leading to benefitting the performance of devices. The breakdown voltage of the fabricated SBD could reach 1200 V at leak-age current 20 μA, about 70% of the theoretical breakdown voltage. Meanwhile, both of the simulation and experimental results show that the length of the SIPOS FP termination is an important factor for structure design.
基金Project supported by the Key Research and Development Program of Jiangsu Province,China(Grant No.BE2020010)the Natural Science Foundation of Guangdong Province,China(Grant No.2023A1515012652)。
文摘Based on the charge balance principle,an optimal impurity distribution variation of lateral doping termination(OIDVLD)and its ion-injection mask design method are proposed and verified.The comparative simulations and experiments show that OID-VLD can achieve better blocking ability and reliability than the traditional VLD(T-VLD).Vertical double diffusion MOSFET(VDMOS)with OID-VLD achieved breakdown voltage(BV)of 1684 V and passed the 168 hours 100℃-110℃-120℃-125℃high-temperature reverse bias(HTRB)test,while VDMOS with T-VLD obtained BV of 1636 V and failed in the 20 hours 120℃HTRB test.
基金Project supported by the National Key Research and Development Program of China(Grant No.2018YFB0104701)。
文摘Doping concentration and thickness of an epitaxy layer are the most essential parameters for power devices.The conventional algorithm extracts these two parameters by calculating the doping profile from its capacitance-voltage(C-V)characteristics.Such an algorithm treats the device as a parallel-plane junction and ignores the influence of the terminations.The epitaxy layer doping concentration tends to be overestimated and the thickness underestimated.In order to obtain the epitaxy layer parameters with higher accuracy,a new algorithm applicable for devices with field limited ring(FLR)terminations is proposed in this paper.This new algorithm is also based on the C-V characteristics and considers the extension manner of the depletion region under the FLR termination.Such an extension manner depends on the design parameters of the FLR termination and is studied in detail by simulation and modeling.The analytical expressions of the device C-V characteristics and the effective doping profile are derived.More accurate epitaxy layer parameters can be extracted by fitting the effective doping profile expression to the C-V doping profile calculated from the C-V characteristics.The relationship between the horizontal extension width and the vertical depth of the depletion region is also acquired.The credibility of the new algorithm is verified by experiments.The applicability of our new algorithm to FLR/field plate combining terminations is also discussed.Our new algorithm acts as a powerful tool for analyses and improvements of power devices.
基金the National Basic Research Program of China under Grant Nos 2010CB327504,2011CB922100 and 2011CB301900the National Natural Science Foundation of China under Grant Nos 60936004 and 11104130+1 种基金the Natural Science Foundation of Jiangsu Province under Grant Nos BK2011556 and BK2011050the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Edge termination is one of the key technologies for fabricating high voltage Schottky barrier diodes(SBDs),which could effectively reduce the peak electric field along the Schottky contact edge and enhance the breakdown voltage.We adopt a high-resistivity ring structure as the edge termination for planar GaN SBDs.The edge termination is formed by self-aligned boron implantation on the edge of devices to form a highly damaged layer.In the implant dose and energy ranges studied experimentally,the GaN SBDs show improved blocking characteristics in terms of reverse leakage current and breakdown voltage at higher implant dose or implant energy.Meanwhile,the forward turn-on characteristics of the GaN SBDs exhibit no apparent change.
基金Supported by the National Natural Science Foundation of China(Grant Nos.51972266, 51672214, 11304248, and 11247230)the Natural Science Basic Research Plan in Shaanxi Province of China(Grant No.2014JM1014)+2 种基金the Scientific Research Program Funded by Shaanxi Provincial Education Department(Grant No.2013JK0624)the Fund Program for the Scientific Activities of Selected Returned Overseas Professionals in Shaanxi Province of Chinathe Youth Bai-Ren Project in Shaanxi Province of China
文摘Fundamental understanding of interfacial charge behaviors is of great significance for the optoelectronic and photovoltaic applications.However, the crucial roles of perovskite terminations in charge transport processes have not been completely clear.We investigate the charge transfer behaviors of the CsPbI3/black phosphorus(BP)van der Waals heterostructure by using the density functional theory calculations with a self-energy correction.The calculations at the atomic level demonstrate the type-Ⅱ band alignments of the CsPbI3/BP heterostructure,which make electrons transfer from the perovskite side to monolayer BP.Moreover, the stronger interaction and narrower physical separation of the interfaces can lead to higher charge tunneling probabilities in the CsPbI3/BP heterostructure.Due to different electron affinities, the PbI2-terminated perovskite slab tends to collect electrons from the adjacent materials, whereas the CsI-termination prefers to inject electrons into transport materials.In addition, the interface coupling effect enhances the visible-light-region absorption of the CsPbI3/BP heterostructure.This study highlights the importance of the perovskite termination in the charge transport processes and provides theoretical guidelines to develop high-performance photovoltaic and optoelectronic devices.
基金supported by National Natural Science Foundation of China (Nos.10675053,10475033)National Basic Research Program of China(No.2007CB815005)
文摘High spin states of the odd-odd nucleus 122^Ⅰ have been investigated via the fusion- evaporation reaction 116^Cd（11^B, 5n） at a beam energy of 68 MeV. The yrast band is extended up to Ⅰ^π= （29＋）. The band termination at Ⅰ^π= （22^＋） reported in previous studies is confirmed and interpreted as arising from a shape change from collective prolate to noncollective oblate according to Total-Routhian-Surface （TRS） calculations. In addition, the Ⅰ^π=（29^＋） state is assigned to the [πh^11/2 （πg7/2）^2]23/2- [（vhll/2）^3 （vd5/2）^2]35/2- configuration corresponding to the full alignment of all valance nucleons outside the semi-closed shell.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61604016 and 51802025)China Postdoctoral Science Foundation(Grant No.2017M613028)+1 种基金the Fundamental Research Funds for the Central Universities,China(Grant Nos.300102319209 and 300102310501)the Innovation,and Entrepreneurship Training Program for Undergraduates(Grant Nos.202010710231 and 201910710564).
文摘Effects of initial surface termination on electrical characteristics of La2O3/Al2O3 nanolaminates deposited by atomic layer deposition are studied by conductive atomic force microscopy working in contact mode and standard electrical characterization methods.It is found that,compared with La2O3/Al2O3 nanolaminates with LaOx as termination,lower interface trap density,less current leakage spots,and higher breakdown voltage are obtained in the La2O3/Al2O3 nanolaminates with AlOx as termination after annealing.A clear promotion of interface silicate layer is observed for La2O3/Al2O3 nanolaminates with AlOx as termination compared with LaOx as termination under the same annealing condition.In addition,the current conduction mechanism in La2O3/Al2O3 nanolaminates is considered as the Poole-Frenkel conduction.All results indicate that the AlOx is a more appropriate termination to deposit La2O3/Al2O3 nanolaminates on Si substrate,which is useful for the high-κ process development.
基金financially supported by the Beijing Municipal Science and Technology Project (Grant No. Z231100006023015)the Major Scientific and Technological Research and Development of Shunyi District of Beijingthe Chinese Academy of Sciences。
文摘Silicon carbide(SiC) is a promising platform for fabricating high-voltage, high-frequency and high-temperature electronic devices such as metal oxide semiconductor field effect transistors in which many junctions or interfaces are involved. The work function(WF) plays an essential role in these devices. However, studies of the effect of conductive type and polar surfaces on the WF of SiC are limited. Here, we report the measurement of WFs of Si-and C-terminated polar surfaces for both p-type and n-type conductive 4H-SiC single crystals by scanning Kelvin probe microscopy(SKPFM). The results show that p-type SiC exhibits a higher WF than n-type SiC.The WF of a C-terminated polar surface is higher than that of a Si-terminated polar surface, which is further confirmed by first-principles calculations. By revealing this long-standing knowledge gap, our work facilitates the fabrication and development of SiC-based electronic devices, which have tremendous potential applications in electric vehicles, photovoltaics, and so on. This work also shows that SKPFM is a good method for identifying polar surfaces of SiC and other polar materials nondestructively, quickly and conveniently.
文摘Machine learning(ML) is well suited for the prediction of high-complexity,high-dimensional problems such as those encountered in terminal ballistics.We evaluate the performance of four popular ML-based regression models,extreme gradient boosting(XGBoost),artificial neural network(ANN),support vector regression(SVR),and Gaussian process regression(GP),on two common terminal ballistics’ problems:(a)predicting the V50ballistic limit of monolithic metallic armour impacted by small and medium calibre projectiles and fragments,and(b) predicting the depth to which a projectile will penetrate a target of semi-infinite thickness.To achieve this we utilise two datasets,each consisting of approximately 1000samples,collated from public release sources.We demonstrate that all four model types provide similarly excellent agreement when interpolating within the training data and diverge when extrapolating outside this range.Although extrapolation is not advisable for ML-based regression models,for applications such as lethality/survivability analysis,such capability is required.To circumvent this,we implement expert knowledge and physics-based models via enforced monotonicity,as a Gaussian prior mean,and through a modified loss function.The physics-informed models demonstrate improved performance over both classical physics-based models and the basic ML regression models,providing an ability to accurately fit experimental data when it is available and then revert to the physics-based model when not.The resulting models demonstrate high levels of predictive accuracy over a very wide range of projectile types,target materials and thicknesses,and impact conditions significantly more diverse than that achievable from any existing analytical approach.Compared with numerical analysis tools such as finite element solvers the ML models run orders of magnitude faster.We provide some general guidelines throughout for the development,application,and reporting of ML models in terminal ballistics problems.
文摘We evaluate an adaptive optimisation methodology,Bayesian optimisation(BO),for designing a minimum weight explosive reactive armour(ERA)for protection against a surrogate medium calibre kinetic energy(KE)long rod projectile and surrogate shaped charge(SC)warhead.We perform the optimisation using a conventional BO methodology and compare it with a conventional trial-and-error approach from a human expert.A third approach,utilising a novel human-machine teaming framework for BO is also evaluated.Data for the optimisation is generated using numerical simulations that are demonstrated to provide reasonable qualitative agreement with reference experiments.The human-machine teaming methodology is shown to identify the optimum ERA design in the fewest number of evaluations,outperforming both the stand-alone human and stand-alone BO methodologies.From a design space of almost 1800 configurations the human-machine teaming approach identifies the minimum weight ERA design in 10 samples.
基金supported by the National Natural Science Foundation of China(Grant No.11847061)Domestic Visiting Program for Young and Middle-aged Teachers in Shanghai Universities.
文摘We investigate the behavior of edge modes in the presence of different edge terminations and long-range(LR)hopping.Here,we mainly focus on such model crystals with two different types of structures(type I:“…-P-Q-P-Q-…”and type II:“…=P-Q=P-Q=…”),where P and Q represent crystal lines(CLs),while the symbols“-”and“=”denote the distance between the nearest neighbor(NN)CLs.Based on the lattice model Hamiltonian with LR hopping,the existence of edge modes is determined analytically by using the transfer matrix method(TMM)when different edge terminals are taken into consideration.Our findings are consistent with the numerical results obtained by the exact diagonalization method.We also notice that edge modes can exhibit different behaviors under different edge terminals.Our result is helpful in solving novel edge modes in honeycomb crystalline graphene and transition metal dichalcogenides with different edge terminals.
基金supported by the National Key R&D Program of China(Grant No.2017YFC0805309)Natural Science Foundation of Fujian Province(Grant No.2021J01820)Department of Education of Fujian Province Project(Grant Nos.JAT190294 and JAT210230).
文摘Considering the uncertainty of the speed of horizontal transportation equipment,a cooperative scheduling model of multiple equipment resources in the automated container terminal was constructed to minimize the completion time,thus improving the loading and unloading efficiencies of automated container terminals.The proposed model integrated the two loading and unloading processes of“double-trolley quay crane+AGV+ARMG”and“single-trolley quay crane+container truck+ARMG”and then designed the simulated annealing particle swarm algorithm to solve the model.By comparing the results of the particle swarm algorithm and genetic algorithm,the algorithm designed in this paper could effectively improve the global and local space search capability of finding the optimal solution.Furthermore,the results showed that the proposed method of collaborative scheduling of multiple equipment resources in automated terminals considering hybrid processes effectively improved the loading and unloading efficiencies of automated container terminals.The findings of this study provide a reference for the improvement of loading and unloading processes as well as coordinated scheduling in automated terminals.
基金This work was supported by grants from the National Natural Science Foundation of China(82103183,82102803,82272849)the Natural Science Foundation of Hunan Province(2022JJ40767,2021JJ40976)+1 种基金the Natural Science Fund for Outstanding Youths in Hunan Province(2023JJ20093)the National Key Research and Development Program(2022YFC2504700).
文摘Dear Editor,Ferroptosis,an iron-dependent form of cell death driven by overwhelming lipid peroxidation,represents a vulnerability in cancers,and therapeutic strategies to further potentiate ferroptosis hold great potential for melanoma treatment.
文摘This paper proposes an adaptive predefined-time terminal sliding mode control(APTSMC)scheme for attitude tracking control of a quadrotor.To create this,an adaptive predefined-time stability controller based on a terminal sliding mode is constructed.The upper bound of convergence time in the proposed scheme can be adjusted by the explicit parameters during the design process of the controller.In addition,it is proved that the attitude tracking error will converge within two periods of the preset time.These two periods are set between two ranges:From the initial values to the sliding mode surface and from the sliding mode surface to the region near the origin.Furthermore,an adaptive law is adopted to eliminate unknown external disturbances and the effects of the uncertainties in the quadrotor model,so it is unnecessary to require the prior knowledge of the upper bound of the perturbations.Simulation results are produced and comparative case studies are carried out to demonstrate that the proposed scheme has faster convergence speed and smaller tracking errors.
