基于SM-JTE结构的4H-SiC器件

介绍了高压空间调制结终端扩展(SM-JTE)结构及其优势。结合实际的MOSFET工艺和已有的理论模型,定义了全新的4H-SiC器件TCAD仿真模型参数。首次提出了确定SM-JTE最优长度的方法。基于SM-JTE结构的4H-SiC器件具有优良的击穿特性。SM-JTE结构的长度为230 μm时,SM-JTE的击穿电压可以达到16 kV。针对界面电荷对击穿特性的影响进行了系统仿真研究。仿真结果表明,正界面电荷相比负界面电荷对击穿电压的影响更大,且界面态电荷会引起击穿电压明显下降。该SM-JTE结构可以采用更短的结终端,在同样尺寸的芯片上能制作更多的器件,从而提高生产效率,降低器件成本。     

4H-SiC p-n结基于精确碰撞电离模型的雪崩倍增因子研究

雪崩倍增效应是4H-SiC雪崩光电二极管、功率半导体器件等器件的关键机理。作为其中最重要的物理参数，雪崩倍增因子(M)的精确解析表达式目前未见报道。文章提出4H-SiC p-n结M的精确计算方法及其解析表达式。基于更准确的碰撞电离模型，通过MATLAB对4H-SiC单边突变结(p⁺-n)电子和空穴的碰撞电离积分(I)进行精确的数值计算，给出击穿电压(BV)随掺杂浓度的经验表达式，进一步提出电离积分随外加电压及掺杂浓度的拟合表达式。此外，对外加电压接近BV的情形进行细致的相对误差分析，表明电子电离积分受电场影响显著。对于雪崩光电二极管及功率器件较宽的BV范围，所提出的拟合表达式在外加反向偏压大于0.65BV时具有较高的精确度(相对误差小于5%)。     

台面结终端高压4H-SiC BJTs的击穿特性研究

根据雪崩碰撞理论,本文对具有台面结构的4H-SiC BJTs中所使用的单区和多区结终端结构参数对击穿电压的影响进行了分析和计算。计算结果表明,在单区结终端结构中,通过精确控制有源JTE的掺杂浓度和离子注入深度可以有效提高台面BJTs器件的击穿电压,而多区结终端结构可以在保持击穿电压不变的前提下降低峰值表面电场。同时文中还对正负表面态或界面态对击穿电压的影响做了详细的计算分析。这些结果对于优化台面功率器件的高压特性有着重要的现实意义。     

平面结构4H-SiC BJT击穿特性及终端技术研究

4H-SiC双极晶体管（BJT）主要应用于大功率器件,器件的阻断特性是最重要的性质之一,因此提高器件的耐高压能力非常重要。国内外的高校和研究机构在SiC器件击穿特性的研究方面进行了大量研究。但是目前绝大多数研究都是基于垂直型4H-SiC BJT,而对于平面型4H-SiC BJT击穿特性的研究相对较少。本论文对采取结终端扩展(JTE)和浮空场限环(FFLRs)两种基本结终端结构的平面型器件的击穿特性和击穿机理进行了比较和分析,并在此基础上进行了器件结构优化设计。     

6H-SiC单极功率器件性能的温度关系

基于碳化硅材料电离系数和迁移率的温度依赖性,利用有效电离系数的Fulop近似,推出了6H-SiC单极性功率器件击穿电压和比导通电阻的温度依赖性解析表达式.理论预言的击穿电压和临界电场与先前的实验结果基本一致(误差小于10%),验证了理论模型的适用性.     

晶圆各向异性对4H-SiC基VDMOSFET单粒子效应的影响

研究了晶圆各向异性对4H-SiC基垂直双扩散MOSFET(VDMOSFET)单粒子效应的影响。建立了器件二维仿真结构,选取合适的仿真模型并对参数进行了修正。仿真结果表明,基于(0001)和(11 2-0)晶圆器件的单粒子烧毁(SEB)阈值电压(V_(SEB))分别为350V和255V,SEB发生时的临界击穿电场强度分别为2.4×10~6 V/cm和1.8×10~6 V/cm。在V_d=30V、V_g=-13.9 V的偏置条件下,两种晶圆器件的氧化层最大瞬态电场均为5.6×10~6 V/cm。结果表明晶圆各向异性导致(0001)晶圆器件的抗SEB能力更强,而对单粒子栅穿效应(SEGR)没有影响。     

4H-SiC npn BJT特性研究

基于二维器件仿真软件Medici对4H-SiC双极型晶体管(BJT)进行了建模,包括能带模型、能带窄变模型、迁移率模型、产生复合模型和不完全电离模型,为4H-SiC的工艺与器件提供了设计平台.在此基础上对4H-SiC BJT器件进行了模拟研究.结果显示,器件基极电流I_B=1μA/μm时发射极电流增益β为32.4,击穿电压BV_CEO大于800V,截止频率f_T接近1GHZ.     

高性能锗硅异质结器件击穿特性的研究

对高频下的SiGe HBT器件击穿特性进行了研究。借助TCAD仿真工具,分析了影响器件击穿特性的基区Ge分布与集电区掺杂浓度超结结构。在3种不同Ge分布下,仿真结果表明,基区Ge的均匀分布有利于提高击穿电压;同时将超结结构引入集电区后,SiGe HBT器件的击穿电压提高了36%,由2.5 V提高到3.4 V。     

浮结位置对4H-SiC浮结结势垒肖特基二极管特性的影响(英文)

同质外延层厚度、铝离子注入深度及光刻偏差会导致4H-SiC浮结结势垒肖特基二极管中浮结位置偏离最优值,器件特性变差。通过数值模拟的方法对浮结横向及纵向位置偏差对其电学特性的影响进行了研究。纵向方向,两个梯形电流分布使得通态比电阻随着浮结由主结向下移动而缓慢增加。击穿电压由距离主结3.5μm处的607V增加到5.6μm处的1 030V。随着浮结进一步向下移动,击穿电压急剧下降,最终保持在550V。这个变化趋势可以通过浮结在漂移区中不同纵向位置的电场分布进行解释。横向方向,浮结与主结对准及交叉放置时电场呈周期性分布且非常均匀,浮结均匀的承担了电压,击穿电压较高。浮结横向偏差时,电流导通路径变长,通态比电阻增加。计算结果表明,浮结与主结对准与交叉放置时Baliga品质因子达到了9.8×109 W/cm2,16%高于1.3μm横向偏差时的8.2×109 W/cm2。因此,4H-SiC浮结结势垒肖特基二极管设计时必须考虑工艺偏差对其特性的影响。     

3300 V-10 A SiC肖特基二极管北大核心CSCD

利用一次离子注入同时形成有源区和结终端结构,实现3 300 V 4H-SiC肖特基二极管。器件的正向电压为1.7 V时,电流达到10.3 A,相应电流密度为100 A/cm2,比导通电阻为7.77 mΩ·cm2。在3 300 V反向偏置电压下反向漏电流为226μA。测试同一晶圆上的pn二极管显示,设计的场限环结终端击穿电压可以达到4 000 V,达到仿真结果的95%。分析发现肖特基二极管的漏电流主要由肖特基接触的热场电子发射产生,有源区的肖特基接触线宽直接影响器件的正向电流密度和反向漏电流。设计合适的肖特基接触宽度是实现高性能器件的关键。     

聚对苯撑苯并双(口恶)唑发光及其器件制备

采用光谱技术,研究了聚对苯撑苯并双(口恶)唑(PBO)溶液的光敏发光特性,并用相对法估算出溶液发光效率在50%范围.结合光谱技术、半导体电学和电化学等研究手段,具体研究了以PBO为发光层的单层电致发光器件,研究结果显示,电致发光与薄膜的光致发光有具有相同的发光中心,峰值位于510 nm左右.同时发现,由于存制备过程中不同处理条件使得不同厚度薄膜残留的掺杂物质浓度不同,从而引起薄膜的导电性的不同.使得器件的阈值场强随PBO厚度的减小而逐渐增加.     

系统级封装新型埋入式电源滤波结构的研究

在高密度小尺寸的系统级封装(SiP)中,对供电系统的完整性要求越来越高,多芯片共用一个电源网路所产生的电压抖动除了会影响到芯片的正常工作,还会通过供电网路干扰到临近电路和其他敏感电路,导致芯片误动作,以及信号完整性和其他电磁干扰问题.这种电压抖动所占频带相当宽,几百MHz到几个GHz的中频电源噪声普通方法很难去除.结合埋入式电容和电源分割方法的特点,提出一种新型高性能埋入式电源低通滤波结构直接替代电源/地平面.研究表明,在0.65～4GHz的频带内隔离深度可达-40～75 dB,电源阻抗均在0.25ohm以下,实现了宽频高隔离度的高性能滤波作用.分别用电磁场和广义传输线两种仿真器模拟,高频等效电路模型分析这种低通滤波器的工作原理以及结构对隔离性能的影响,并进行了实验验证.     

Emerging interconnects: a state-of-the-art review and emerging solutions

Aluminium was a primary material for interconnection in integrated circuits (ICs) since their inception. Later, copper was introduced as interconnect material which has better metallic conductivity and resistance to electromigration. As the aggressive technology scaling continues, the copper resistivity increased because of size effects, which causes increase in delay, power dissipation and electromigration. The need to reduce the resistor-capacitor??????? delay, dynamic power utilisation and the crosstalk commotion is as of now the fundamental main impetus behind the presentation of new materials. The purpose of this paper is to do a survey of interconnect material used in IC from introduction of ICs to till date. This paper studies and reviews new materials available for interconnect application which are optical interconnects, carbon nanotube (CNT), graphene nanoribbons (GNRs) and silicon nanowires which are alternatives to copper. While doing a survey of interconnect material, it is found that multiwalled CNTs, multilayer GNR and mixed CNT bundles are promising candidates and are ultimate choice that can strongly address the problems faced by copper but on integration basis copper would last for coming years.     

Arsenic deposition as a precursor layer on silicon (211) and (311) surfaces

We investigate the properties of arsenic (As) covered Si(211) and Si(311) surfaces by analyzing data from x-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED) images. We then create a model using total surface energy calculations. It was found that both Si(211) and Si(311) had 0.68±0.08 surface As coverage. Si(211) had 0.28±0.04 Te coverage and Si(311) had 0.24±0.04 Te coverage. The Si(211) surface replaces the terrace and trench Si atoms with As for a lower surface energy, while the Si edge atoms form dimers. The Si(311) surface replaces all terrace atoms and adsorbs an As dimer every other edge site. These configurations imply an improvement in the mean migration path from the bare silicon surface by allowing the impinging atoms for the next epitaxial layer, tellurium (Te), to bind at every other pair of edge atoms, and not the step terrace sites. This would ensure a nonpolar, B-face growth.     

光子晶体微腔发光二极管

光子晶体微腔因其具有增强自发辐射、定向输出和单模工作的能力而受到广泛关注。介绍了光子晶体微腔发光二极管的基本原理、设计、特性、制作及其典型器件。     

用于单光子TOF测量的时间-幅度变换器

基于新型共源共栅电流源的积分方法,设计了一种用于单光子飞行时间(TOF)测量的时间-幅度变换器(TAC)。该方法有效简化了TAC电路结构,减小了TAC占用面积,显著提高了TOF的满量程范围(FSR)。采用0.18 μm标准CMOS工艺设计。集成TAC的单光子探测器像素单元的填充因子可达到26.8%。后仿真结果表明,该TAC在120 ns的FSR内具有230 ps的定时分辨率,微分非线性(DNL)低于0.05 LSB,积分非线性(INL)低于1.1 LSB。蒙特卡洛仿真表明,512个TAC像素间的不均匀性低于0.5 %。该TAC非常适用于高密度时间相关的单光子计数(TCSPC)探测器阵列。     

Comparative study of maximum power point tracking techniques for hybrid renewable energy system

The power generation demand is increasing day-by-day throughout the world, therefore, the use of hybrid systems becomes a significant solution. The hybrid renewable energy system (HRES) is used for delivering power in various regions in order to overcome intermittence of wind and solar resources. Because of increasing environmental problems, for example, greenhouse gas emission and energy cost have interested novel research into substitute methods in favour of electrical power generation. Maximum Power Point Tracking (MPPT) control method is a vast deal of novel research used for enhancing the efficiency of HRES. The authors have revealed that the hybrid techniques i.e. Global MPPT, fuzzy-neuro systems, Adaptive Neuro-Fuzzy Inference System (ANFIS), Perturbed and Observe (P&O) + Adaptive Neural Network (ANN) etc. can provide best results as compared to other MPPT control methods. This paper offering a state of art review of MPPT control techniques for HRES.     

Joint estimation of TOA and DOA in IR-UWB system using a successive propagator method

Impulse radio ultra-wideband (IR-UWB) ranging and positioning require accurate estimation of time-of-arrival (TOA) and direction-of-arrival (DOA). With receiver of two antennas, both of the TOA and DOA parameters can be estimated via two-dimensional (2D) propagator method (PM), in which the 2D spectral peak searching, however, renders much higher computational complexity. This paper proposes a successive PM algorithm for joint TOA and DOA estimation in IR-UWB system to avoid 2D spectral peak searching. The proposed algorithm firstly gets the initial TOA estimates in the two antennas from the propagation matrix, then utilises successively one-dimensional (1D) local searches to achieve the estimation of TOAs in the two antennas, and finally obtains the DOA estimates via the difference in the TOAs between the two antennas. The proposed algorithm, which only requires 1D local searches, can avoid the high computational cost in 2D-PM algorithm. Furthermore, the proposed algorithm can obtain automatically paired parameters and has better joint TOA and DOA estimation performance than conventional PM algorithm, estimation of signal parameters via rotational invariance techniques algorithm and matrix pencil algorithm. Meanwhile, it has very close parameter estimation to that of 2D-PM algorithm. We have also derived the mean square error of TOA and DOA estimation of the proposed algorithm and the Cramer-Rao bound of TOA and DOA estimation in this paper. The simulation results verify the usefulness of the proposed algorithm.     

超宽带脉冲信号的光学生成方法研究

近年来超宽带(UWB)通信技术迅猛发展,在测量、雷达技术、民用和军事无线通信中有着重要的应用,UWB-over-fiber技术已经成为目前研究的热点,其中就包括UWB脉冲信号的产生方法。区别于传统的电子学方法,光子学产生方法不受电子瓶颈制约,可以实现很高的带宽,并且具有抗电磁干扰、重量轻、结构紧凑的优点。通过对比国内外本领域研究成果,讨论及总结了以下三种原理的UWB脉冲信号的光学生成方法:1)相位调制-强度调制转换(PM-IM);2)半导体光放大器(SOA)的非线性效应;3)频谱塑形和色散所致频域-时域映射,然后对各种方案进行了对比分析。     

一种基于分段CRC的LDPC译码的改进算法

级联多个循环冗余校验(CRC)的LDPC译码算法有效地改善了译码的收敛特性。然而在其译码算法中,当CRC检测的整体漏检概率不够低时,出现误码平台。因此,该文提出了改进算法,通过减少在译码算法中CRC检测的次数,降低整体漏检概率,提高了误码性能。仿真表明改进的算法提高了误码性能,译码复杂度也增加不大。