电荷失配对SiC半超结垂直双扩散金属氧化物半导体场效应管击穿电压的影响

Si C半超结垂直双扩散金属氧化物半导体场效应管(VDMOSFET)相对于常规VDMOSFET在相同导通电阻下具有更大击穿电压.在N型外延层上进行离子注入形成半超结结构中的P柱是制造Si C半超结VDMOSFET的关键工艺.本文通过二维数值仿真研究了离子注入导致的电荷失配对4H-Si C超结和半超结VDMOSFET击穿电压的影响,在电荷失配程度为30%时出现半超结VDMOSFET的最大击穿电压.在本文的器件参数下,P柱浓度偏差导致击穿电压降低15%时,半超结VDMOSFET柱区浓度偏差范围相对于超结VDMOSFET可提高69.5%,这意味着半超结VDMOSFET对柱区离子注入的控制要求更低,工艺制造难度更低.     

电荷耦合器件中子辐照诱发的位移效应

为研究电荷耦合器件空间辐照效应、参数退化机理,对国产64×64像元电荷耦合器件进行了中子辐照位移损伤效应研究。样品在中子辐照下,暗信号、暗信号非均匀性和电荷转移效率等关键性能参数退化显著。研究结果表明:暗信号的退化是由于中子辐照产生的体缺陷能级在耗尽层中充当复合-产生中心,增大了热载流子的产生率所致,而各像素单元暗信号退化的不一致性使暗信号非均匀性增大;电荷转移效率显著减小则是由于中子辐照在转移沟道中产生的体缺陷不断捕获、发射电子所引起。在整个实验过程中,饱和输出电压的退化可以忽略不计,表现出较好的抗位移损伤能力。     

电荷耦合器件的γ辐照剂量率效应研究

对电荷耦合器件进行了不同剂量率的γ辐照实验,通过多种参数的测试探讨了剂量率与电荷耦合器件性能退化的关系,并对损伤的物理机理进行分析。辐照和退火结果表明:暗信号和暗信号非均匀性是γ辐照的敏感参数,电荷转移效率和饱和输出电压随剂量累积有缓慢下降的趋势;暗场像素灰度值整体抬升,像元之间的差异显著增加;电荷耦合器件的暗信号增量与剂量率呈负相关性,器件存在潜在的低剂量率损伤增强效应。分析认为,剂量率效应是由界面态和氧化物陷阱电荷竞争导致的。通过电子-空穴对复合模型、质子输运模型和界面态形成对机理进行了解释。     

电极表面光滑程度对水介质高电压击穿的影响

 采用水介质同轴实验装置,改变电极表面的光滑程度,在μs级充电时进行水介质击穿实验,并对实验结果进行了分析和解释。结果表明：抛光电极表面可有效提高水介质耐高电压击穿能力;表面粗糙度为0.4～0.8 μm的抛光电极表面的击穿场强比表面粗糙度为1.6～3.2 μm的粗糙抛光电极表面,更符合Martin公式。电极表面光滑程度的改善,使阴极场致发射电流减弱进而击穿延迟时间变长,气泡也更难以附着在光滑的电极表面,从而可以提高水介质耐高电压击穿能力。     

电极表面光滑程度对水介质高电压击穿的影响

采用水介质同轴实验装置,改变电极表面的光滑程度,在μs级充电时进行水介质击穿实验,并对实验结果进行了分析和解释。结果表明：抛光电极表面可有效提高水介质耐高电压击穿能力;表面粗糙度为0.4～0.8 μm的抛光电极表面的击穿场强比表面粗糙度为1.6～3.2 μm的粗糙抛光电极表面,更符合Martin公式。电极表面光滑程度的改善,使阴极场致发射电流减弱进而击穿延迟时间变长,气泡也更难以附着在光滑的电极表面,从而可以提高水介质耐高电压击穿能力。     

电荷耦合器件在质子辐照下的粒子输运仿真与效应分析

应用蒙特卡洛方法计算了质子在科学级电荷耦合器件(charge-coupled device, CCD) 结构中的能量沉积, 并结合该CCD的质子辐照试验及退火试验数据, 分析了器件的辐射损伤机理. 仿真计算体硅内沉积的位移损伤剂量和栅氧化层的电离损伤剂量, 辐照与退火试验过程中主要考察暗信号、电荷转移效率两个参数的变化规律. 研究结果显示, 暗信号和电荷转移效率的变化规律与位移、电离损伤剂量一致; 退火后暗信号大幅度降低, 辐照导致的表面暗信号增加占总暗信号增加的比例至少为80%; 退火后电荷转移效率恢复较小, 电荷转移效率降低的原因主要为体缺陷. 通过总结试验规律, 推导出了电荷转移效率退化程度的预估公式及其损伤因子k_damage.     

质子与中子辐照对电荷耦合器件暗信号参数的影响及其效应分析

对科学级电荷耦合器件(charge-coupled device, CCD)进行了质子和中子辐照试验及退火试验, 应用蒙特卡洛方法计算了质子和中子在CCD中的能量沉积, 分析了器件的辐射损伤机理. 仿真计算了N⁺埋层内沉积的位移损伤剂量, 辐照与退火试验过程中主要考察暗信号的变化规律. 研究结果显示, 质子与中子辐照均会引发暗信号退化, 其退化的规律与位移损伤剂量变化一致; 退火后, 质子辐照所致CCD暗信号大幅度恢复, 其体暗信号增加量占总暗信号增加量的比例最多为22%; 中子辐照引发的暗信号增长主要为体暗信号. 质子和中子在N⁺埋层产生相同位移损伤剂量的情况下, 两者导致的体暗信号增长量相同, 质子与中子辐照产生的体缺陷对体暗信号增长的贡献是同质的.     

模拟增益对电荷耦合器件信噪比与动态范围影响的实验研究

电荷耦合器件(CCD)是遥感成像系统的核心部件,为了在低照度、低量化位数的情况下获得高信噪比与大动态范围的遥感图像,首先根据CCD的结构与噪声物理性质给出了模拟增益、量化位数与CCD信噪比的关系,接着搭建了CCD的积分球标定系统,依据实验数据建立了散粒噪声、光子响应非均匀性噪声以及基底噪声的数学模型,然后着重分析了低照度情况下模拟增益与信噪比之间的关系,最后搭建了实际成像系统,获取了低照度情况下不同模拟增益系数的遥感图像.结果表明理论分析、实验室积分球标定数据与实际成像图像符合良好,即模拟增益提高1至2倍 关键词： 电荷耦合器件 模拟增益 信噪比 遥感成像系统     

表面电荷与体陷阱对GaN基HEMT器件热电子和量子效应的影响研究

研究了GaN基HEMT器件表面电荷和体陷阱的变化对输出特性的影响.通过分析表面电荷与体陷阱对电流坍塌效应、饱和电流和膝点电压的影响,初步确定了其变化关系.研究结果显示表面电荷的增加能够耗尽二维电子气,减弱电流坍塌效应,降低饱和电流,使膝点电压非正常后移.同时,体陷阱的减小可以有效减弱电流坍塌效应,增大饱和电流,且膝点电压基本保持不变.晶格温度较低时,热电子效应和量子隧穿效应对电流坍塌效应影响显著.采用流体动力学模型,分析了引起电流坍塌效应的内在物理机制,并获得了器件设计和制备的优化方案. 关键词： GaN-HEMT器件 电流坍塌效应 热电子效应 表面电荷     

表面电荷与体陷阱对GaN基HEMT器件热电子和量子效应的影响研究

研究了GaN基HEMT器件表面电荷和体陷阱的变化对输出特性的影响.通过分析表面电荷与体陷阱对电流坍塌效应、饱和电流和膝点电压的影响,初步确定了其变化关系.研究结果显示表面电荷的增加能够耗尽二维电子气,减弱电流坍塌效应,降低饱和电流,使膝点电压非正常后移.同时,体陷阱的减小可以有效减弱电流坍塌效应,增大饱和电流,且膝点电压基本保持不变.晶格温度较低时,热电子效应和量子隧穿效应对电流坍塌效应影响显著.采用流体动力学模型,分析了引起电流坍塌效应的内在物理机制,并获得了器件设计和制备的优化方案.     

Design optimization of high breakdown voltage vertical GaN junction barrier Schottky diode with high-K/low-K compound dielectric structure

A vertical junction barrier Schottky diode with a high-$K$/low-$K$ compound dielectric structure is proposed and optimized to achieve a high breakdown voltage (BV). There is a discontinuity of the electric field at the interface of high-$K$ and low-$K$ layers due to the different dielectric constants of high-$K$ and low-$K$ dielectric layers. A new electric field peak is introduced in the n-type drift region of junction barrier Schottky diode (JBS), so the distribution of electric field in JBS becomes more uniform. At the same time, the effect of electric-power line concentration at the p-n junction interface is suppressed due to the effects of the high-$K$ dielectric layer and an enhancement of breakdown voltage can be achieved. Numerical simulations demonstrate that GaN JBS with a specific on-resistance ($R_{\rm on, sp}$) of 2.07 m$\Omega\cdot$cm$^{2}$ and a BV of 4171 V which is 167% higher than the breakdown voltage of the common structure, resulting in a high figure-of-merit (FOM) of 8.6 GW/cm$^{2}$, and a low turn-on voltage of 0.6 V.     

Experimental and numerical analyses of high voltage 4H-SiC junction barrier Schottky rectifiers with linearly graded field limiting ring

This paper describes the successful fabrication of 4H-SiC junction barrier Schottky(JBS) rectifiers with a linearly graded field limiting ring(LG-FLR). Linearly variable ring spacings for the FLR termination are applied to improve the blocking voltage by reducing the peak surface electric field at the edge termination region, which acts like a variable lateral doping profile resulting in a gradual field distribution. The experimental results demonstrate a breakdown voltage of 5 kV at the reverse leakage current density of 2 mA/cm2(about 80% of the theoretical value). Detailed numerical simulations show that the proposed termination structure provides a uniform electric field profile compared to the conventional FLR termination, which is responsible for 45% improvement in the reverse blocking voltage despite a 3.7% longer total termination length.     

Junction barrier Schottky rectifier with an improved P-well region

<正>A junction barrier Schottky（JBS） rectifier with an improved P-well on 4H-SiC is proposed to improve the V_F-I_R trade-off and the breakdown voltage.The reverse current density of the proposed JBS rectifier at 300 K and 800 V is about 3.3×10^-8 times that of the common JBS rectifier at no expense of the forward voltage drop.This is because the depletion layer thickness in the P-well region at the same reverse voltage is larger than in the P⁺ grid,resulting in a lower spreading current and tunneling current.As a result,the breakdown voltage of the proposed JBS rectifier is over 1.6 kV,that is about 0.8 times more than that of the common JBS rectifier due to the uniform electric field.Although the series resistance of the proposed JBS rectifier is a little larger than that of the common JBS rectifier,the figure of merit（FOM） of the proposed JBS rectifier is about 2.9 times that of the common JBS rectifier.Based on simulating the values of susceptibility of the two JBS rectifiers to electrostatic discharge（ESD） in the human body model（HBM） circuits,the failure energy of the proposed JBS rectifier increases 17%compared with that of the common JBS rectifier.     

Modeling of high permittivity insulator structure with interface charge by charge compensation

An analytical model of the power metal–oxide–semiconductor field-effect transistor(MOSFET)with high permittivity insulator structure(HKMOS)with interface charge is established based on superposition and developed for optimization by charge compensation.In light of charge compensation,the disturbance aroused by interface charge is efficiently compromised by introducing extra charge for maximizing breakdown voltage(BV)and minimizing specific ON-resistance(R_on,sp).From this optimization method,it is very efficient to obtain the design parameters to overcome the difficulty in implementing the R_on,sp–BV trade-off for quick design.The analytical results prove that in the HKMOS with positive or negative interface charge at a given length of drift region,the extraction of the parameters is qualitatively and quantitatively optimized for trading off BV and Ron,sp with JFET effect taken into account.     

Non-recessed-gate quasi-E-mode double heterojunction AlGaN/GaN high electron mobility transistor with high breakdown voltage

A non-recessed-gate quasi-E-mode double heterojunction AlGaN/GaN high electron mobility transistor(quasi-EDHEMT) 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.     

Non-recessed-gate quasi-E-mode double heterojunction AIGaN/GaN high electron mobility transistor with high breakdown voltage

A non-recessed-gate quasi-E-mode double heterojunction A1GaN/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 A1GaN 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%tm 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.     

复合漏电模型建立及阶梯场板GaN肖特基势垒二极管设计

准垂直GaN肖特基势垒二极管(SBD)因其低成本和高电流传输能力而备受关注.但其主要问题在于无法很好地估计器件的反向特性,从而影响二极管的设计.本文考虑了GaN材料的缺陷以及多种漏电机制,建立了复合漏电模型,对准垂直Ga N SBD的特性进行了模拟,仿真结果与实验结果吻合.基于此所提模型设计出具有高击穿电压的阶梯型场板结构准垂直GaN SBD.根据漏电流、温度和电场在反向电压下的相关性,分析了漏电机制和器件耐压特性,设计的阶梯型场板结构准垂直GaN SBD的Baliga优值BFOM达到73.81 MW/cm~2.     

高峰值功率脉冲激光与石英光纤耦合的空气击穿问题

 研究了15 MW峰值功率脉冲激光与600 μm芯径石英光纤耦合中存在的空气击穿现象。对聚焦区域的空气击穿现象进行了理论和实验研究,测得空气击穿阈值为0.79×10⁹ W/cm²。测得固体介质的激光损伤阈值为2.12×10⁹ W/cm²,与理论计算结果相符。提出了七合一光纤耦合器用于解决空气击穿的办法,实验测得7根光纤并束的耦合效率为67.21%。结果表明光纤耦合器可有效解决15 MW峰值功率脉冲激光与600 μm芯径石英光纤的耦合。     

Effect of gate length on breakdown voltage in AlGaN/GaN high-electron-mobility transistor

The effects of gate length L_G on breakdown voltage VBRare investigated in AlGaN/GaN high-electron-mobility transistors(HEMTs) with L_G= 1 μm~20 μm. With the increase of L_G, VBRis first increased, and then saturated at LG= 3 μm. For the HEMT with L_G= 1 μm, breakdown voltage VBRis 117 V, and it can be enhanced to 148 V for the HEMT with L-_G= 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.     

孔洞聚丙烯驻极体膜中空间电荷与孔洞击穿电荷的俘获特性

对孔洞聚丙烯(PP)驻极体膜系统的研究结果表明：孔洞PP膜中空间电荷的俘获特性随注入的空间电荷量或试样表面电位而变化,注入的电荷量较少时空间电荷主要被俘获在表面深陷阱和近表面次深陷阱中,较多的注入电荷量时空间电荷在进一步填充表层(表面和近表面)陷阱的同时,还将填充体内浅陷阱;这三类陷阱中心所对应的电荷脱阱温度分别约为160℃,138℃和92℃.而孔洞击穿电荷不仅被俘获在与试样表层空间电荷陷阱相似的孔洞表层陷阱中,还有相当的量穿过孔洞表层进入体内、成为浅阱俘获孔洞击穿电荷. 关键词： 孔洞聚丙烯膜 空间电荷 孔洞击穿电荷 俘获特性