Electric field modulation technique for high-voltage AIGaN/GaN Schottky barrier diodes

A novel structure of AIGaN/GaN Schottky barrier diode （SBD） featuring electric field optimization techniques of anode-connected-field-plate （AFP） and magnesium-doped p-type buried layer under the two-dimensional electron gas （2DEG） channel is proposed. In comparison with conventional A1GaN/GaN SBDs, the magnesium-doped p-type buried layer in the proposed structure can provide holes that can help to deplete the surface 2DEG. As a result, surface field strength around the electrode edges is significantly suppressed and the electric field along the channel is distributed more evenly. Through 2D numerical analysis, the AFP parameters （field plate length, LAFP, and field plate height, TAFP） and p-type buried layer parameters （p-type layer concentration, Np, and p-type layer thickness, Tp） are optimized to achieve a three-equal-peak surface channel field distribution under exact charge balance conditions. A novel structure with a total drift region length of 10.5 μm and a magnesium-doped p-type concentration of 1 × 10^17 cm 3 achieves a high breakdown voltage （VB） of 1.8 kV, showing 5 times improvement compared with the conventional SBD with the same device dimension.     

Electric field modulation technique for high-voltage AlGaN/GaN Schottky barrier diodes

A novel structure of AlGaN/GaN Schottky barrier diode(SBD) featuring electric field optimization techniques of anode-connected-field-plate(AFP) and magnesium-doped p-type buried layer under the two-dimensional electron gas(2DEG) channel is proposed.In comparison with conventional AlGaN/GaN SBDs,the magnesium-doped p-type buried layer in the proposed structure can provide holes that can help to deplete the surface 2DEG.As a result,surface field strength around the electrode edges is significantly suppressed and the electric field along the channel is distributed more evenly.Through 2D numerical analysis,the AFP parameters(field plate length,L AFP,and field plate height,T AFP) and p-type buried layer parameters(p-type layer concentration,N P,and p-type layer thickness,T P) are optimized to achieve a three-equal-peak surface channel field distribution under exact charge balance conditions.A novel structure with a total drift region length of 10.5 μm and a magnesium-doped p-type concentration of 1 × 1017cm-3achieves a high breakdown voltage(V B) of 1.8 kV,showing 5 times improvement compared with the conventional SBD with the same device dimension.     

β-环糊精催化下联苯的气-固相溴化反应

β-环糊精(β-CD)是七个葡萄糖单元以α-1,4-糖苷键连成的锥形环状分子,此环中的空腔是疏水性的,因而象酶一样,可提供一个疏水的结合部位来和一些几何形状及大小合适的有机和无机分子形成包结络合物,由于被包结的底物或试剂分子是处于一个低介电常数的微环境中,以及在反应位置上的特殊有利等等,使得环糊精催化下的有机反     

A comparative investigation of an AB- and AA-stacked bilayer graphene sheet under an applied electric field: A density functional theory study

An AB- and AA-stacked bilayer graphene sheet(BLG) under an electric field is investigated by ab initio calculation.The interlayer distance between the two layers,band structures,and atomic charges of the system are investigated in the presence of different electric fields normal to the BLG.The AB- stacked BLG is able to tune the bandgap into 0.234 eV with the increase of the external electronic field to 1 V/nm,however,the AA-stacked BLG is not sensitive to the external electric field.In both the cases,the spacing between the BLG slightly change in terms of the electric field.The charges in the AB- stacked BLG are increased with the increase of the electric field,which is considered to be the reason that causes the bandgap opening in the AB- stacked BLG.     

A novel power UMOSFET with a variable K dielectric layer

A novel split-gate power UMOSFET with a variable K dielectric layer is proposed.This device shows a 36.2% reduction in the specific on-state resistance at a breakdown voltage of 115 V,as compared with the SGE-UMOS device.Numerical simulation results indicate that the proposed device features high performance with an improved figure of merit of Qg × RON and BV2/RON,as compared with the previous power UMOSFET.     

An AlGaN/GaN HEMT with enhanced breakdown and a near-zero breakdown voltage temperature coefficient

An AlGaN/GaN high-electron mobility transistor(HEMT) with a novel source-connected air-bridge field plate(AFP) is experimentally verified.The device features a metal field plate that jumps from the source over the gate region and lands between the gate and drain.When compared to a similar size HEMT device with a conventional field plate(CFP) structure,the AFP not only minimizes the parasitic gate to source capacitance,but also exhibits higher OFF-state breakdown voltage and one order of magnitude lower drain leakage current.In a device with a gate to drain distance of 6 μm and a gate length of 0.8 μm,three times higher forward blocking voltage of 375 V was obtained at VGS =-5 V.In contrast,a similar sized HEMT with a CFP can only achieve a breakdown voltage no higher than 125 V using this process,regardless of device dimensions.Moreover,a temperature coefficient of 0 V/K for the breakdown voltage is observed.However,devices without a field plate(no FP) and with an optimized conventional field plate(CFP) exhibit breakdown voltage temperature coefficients of-0.113 V/K and-0.065 V/K,respectively.     

中低压碳化硅材料、器件及其在电动汽车充电设备中的应用示范

碳化硅（SiC）电力电子器件的高压、高温和高频率特性,使其成为理想的电动汽车充电设备器件,将显著提升电动汽车充电设备的效率和功率密度.开展中低压SiC材料、器件及其在电动汽车充电设备中的示范应用,不仅有利于加快建立我国自主的碳化硅全产业链,而且有助于提高我国电动汽车充电设备的核心竞争力.     

Investigations on mesa width design for 4H–SiC trench super junction Schottky diodes

Mesa width(WM) is a key design parameter for SiC super junction(SJ) Schottky diodes(SBD) fabricated by the trench-etching-and-sidewall-implant method. This paper carries out a comprehensive investigation on how the mesa width design determines the device electrical performances and how it affects the degree of performance degradation induced by process variations. It is found that structures designed with narrower mesa widths can tolerant substantially larger charge imbalance for a given BV target, but have poor specific on-resistances. On the contrary, structures with wider mesa widths have superior on-state performances but their breakdown voltages are more sensitive to p-type doping variation. Medium WMstructures(～ 2 μm) exhibit stronger robustness against the process variation resulting from SiC deep trench etching.Devices with 2-μm mesa width were fabricated and electrically characterized. The fabricated SiC SJ SBDs have achieved a breakdown voltage of 1350 V with a specific on-resistance as low as 0.98 m?·cm~2. The estimated specific drift onresistance by subtracting substrate resistance is well below the theoretical one-dimensional unipolar limit of SiC material.The robustness of the voltage blocking capability against trench dimension variations has also been experimentally verified for the proposed SiC SJ SBD devices.     

An AlGaN/GaN HEMT with enhanced breakdown and near-zero breakdown voltage temperature coefficient

An AlGaN/GaN high-electron mobility transistor (HEMT) with a novel source-connected air-bridge field plate (AFP) is experimentally verified. The device features a metal field plate that jumps from the source over the gate region and lands between the gate and drain. When compared to a similar size HEMT device with conventional field plate (CFP) structure, the AFP not only minimizes the parasitic gate to source capacitance, but also exhibits higher OFF-state breakdown voltage and one order of magnitude lower drain leakage current. In a device with a gate to drain distance of 6 μm and a gate length of 0.8 μm, three times higher forward blocking voltage of 375 V was obtained at V_GS=-5 V. In contrast, a similar sized HEMT with CFP can only achieve a breakdown voltage no higher than 125 V using this process, regardless of device dimensions. Moreover, a temperature coefficient of 0 V/K for the breakdown voltage is observed. However, devices without field plate (no FP) and with optimized conventional field plate (CFP) exhibit breakdown voltage temperature coefficients of -0.113 V/K and -0.065 V/K, respectively.     

Abnormal oxidation in nickel silicide and nickel germanosilicide in sub-micro CMOS

After post-silicidation annealing at various temperatures for 30 min,abnormal oxidation and agglomeration in nickel silicide and nickel germanosilicide are investigated under different conditions of NiSi,with As-,In-,and Sb-doped Si substrates of nickel germanosilicide without any dopants.The NiSi thickness,dopant species,doping concentration,and silicide process conditions are dominant factors for abnormal oxidation and NiSi agglomeration.Larger dopants than Si,thinner NiSi thickness and SiGe substrates,and higher dopant concentrations promote abnormal oxidation and agglomeration.