Barrier height homogeneity for 4.5 kV 4H-SiC Schottky diodes

4.5 kV SiC Schottky diodes have been fabricated using Ni as the Schottky contact. A manufacturing yield of 40% is reached for the bigger area diodes (1.6×1.6 mm²) and of 70% for the smaller ones (0.4×0.4 mm²). The measured variations of barrier height and ideality factor with temperature do not agree with the thermionic model. This has been interpreted in terms of barrier height inhomogeneities using the Werner model. We extracted an average barrier height and its standard deviation . These two parameters are almost independent of the diode size. The variation of the barrier height distribution with field has also been investigated and shows a dependence similar to that of Schottky diodes realized from other semiconductor materials.     

2D-C/SiC复合材料的单轴拉伸力学行为及其强度

通过单调拉伸和循环加卸载试验, 研究了平纹编织C/SiC复合材料的损伤演化过程及其应力-应变行为. 结果表明, 残余应变、卸载模量和外加应力的关系曲线与拉伸应力-应变曲线具有类似的形状. 基于剪滞理论和混合率建立了材料的损伤本构关系和强度模型, 分析计算表明, 残余应变主要由裂纹张开位移和裂纹间距决定, 而卸载模量主要由界面脱粘率决定; 材料的单轴拉伸行为主要由纵向纤维束决定, 横向纤维对材料的整体模量和强度贡献较小. 理论模拟结果与试验值吻合较好.      

Optically controlled SiCGe/SiC heterojunction transistor with charge-compensation layer

A novel optically controlled SiCGe/SiC heterojunction transistor with charge-compensation technique has been simulated by using commercial simulator.This paper discusses the electric field distribution,spectral response and transient response of the device.Due to utilizing p-SiCGe charge-compensation layer,the responsivity increases nearly two times and breakdown voltage increases 33%.The switching characteristic illustrates that the device is latch-free and its fall time is much longer than the rise time.With an increase of the light power density and wavelength,the rise time and fall time will become shorter and longer,respectively.In terms of carrier lifetime,a compromise should be made between the responsivity and switching speed,the ratio of them reaches maximum value when the minority carrier lifetime equals 90 ns.     

Graphene films grown on sapphire substrates via solid source molecular beam epitaxy

A method for growing graphene on a sapphire substrate by depositing an SiC buffer layer and then annealing at high temperature in solid source molecular beam epitaxy (SSMBE) equipment was presented. The structural and electronic properties of the samples were characterized by reflection high energy diffraction (RHEED), X-ray diffraction Φ scans, Raman spectroscopy, and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The results of the RHEED and Φ scan, as well as the Raman spectra, showed that an epitaxial hexagonal α-SiC layer was grown on the sapphire substrate. The results of the Raman and NEXAFS spectra revealed that the graphene films with the AB Bernal stacking structure were formed on the sapphire substrate after annealing. The layer number of the graphene was between four and five, and the thickness of the unreacted SiC layer was about 1--1.5 nm.     

并联交错PFC技术在磁体电源中的应用

并联交错功率因数校正(powerfactorcorrection,PFC)具有能减小输入电流纹波,减小电感磁芯尺寸,减小输出电容纹波、功率因数高等优点．针对其优点,考虑将该变换器应用到强磁场中心的超导磁体电源的备用方案中,以弥补现在运行电源体积过大的不足．本文主要介绍了并联交错PFC的工作原理,对其参数进行设计和选型,分析了控制方法,利用SiC器件,搭建了１kW 的实验样机,实验验证了方案的可行性,为下一步超导磁体电源的升级改造提供了理论和工程经验。     

Reaching for [6]n SiC‐cyclacenes and [6]n SiC‐acenes: A DFT approach

Density functional theory (DFT) calculations introduced triplet ground states for [6]_n SiC‐cyclacenes and ‐acenes with alternate silabenzene rings including silicon atoms in 2 opposite edges (n = 6, 8, 10, 12). The singlet‐triplet energy gap (ΔE_(S‐T)), binding energy per atom (BE/n), and NBO calculation with very small band gap (ΔE_LUMO‐HOMO) confirmed the triplet ground states. In contrast to polyacenes, the singlet [6]_n SiC‐cyclacenes displayed more stability improvement than triplets, through n increasing. This may open the way for synthesis of larger stable [6]_n SiC‐cyclacenes. The ΔE_(S‐T), BE/n, and the strain energy through homodesmic equations indicated more stability for larger [6]_n SiC‐cyclacenes, which was more noticeable in singlet states. Cyclacenes and acenes with high conductivity and full point charge were introduced as suitable candidates for hydrogen storage.     

Localized defects related to the 14N+ ion irradiation-induced magnetism in SiC

The role of localized defects as they pertain to ferromagnetism in SiC, which contains only s and p electrons, is important but unclear. Here, room temperature, macroscopic magnetization is induced and can be tuned in 6H-SiC using ¹⁴N⁺ ion implantation. First-principles density functional theory computation results confirm that ¹⁴N⁺ ion implantation can enhance the ferromagnetic ordering of the local magnetic moments caused by vacancy and substitution defects. The calculated magnetization values in the energetically favored ferromagnetic ordering (1.47–2.93 emu/g for several vacancy and substitution defects) are larger than our experimental values (0.25 emu/g at 5 K and 0.08 emu/g at 300 K), but the result is qualitatively in agreement.     

S吸附对SiC表面不同重构结构的影响

SiC表面重构的发生会引起表面态密度增加,极大地影响SiC功率器件的性能.本文对4H/6H-SiC(0001)-Si端的(3×3)R30°和(3×3)重构结构及3C-SiC(0001)-Si端的(3×2)和(2×1)重构结构分别进行了S原子的吸附研究.结果表明:吸附S原子可以打开表面重构键,不同重构结构均有向体结构恢复的趋势.(3×3)R30°和(3×3)重构的最佳吸附率分别是1/2ML和1/3ML,S吸附对(3×3)R30°重构的作用更大.(3×2)重构表面在1/6ML下的H3位吸附、(2×1)重构表面在1/2ML下的B位吸附时吸附能最低.S钝化后,3C-SiC比4H/6H-SiC体系表面吸附能小,更稳定,重构结构恢复更理想.     

AlN-Y2O3配比对SiC耐磨材料结构和性能的影响

在AlN-Y2O3添加量为6wt;的前提下,将摩尔比分别为10∶90、20∶80、30∶70和40∶60的AlN、Y2O3引入SiC耐磨材料中,于氧化气氛下经1600℃保温3h烧成,研究了AlN、Y2O3配比对SiC耐磨材料结构和性能的影响.结果表明:AlN、Y2O3配比对SiC耐磨材料的性能影响较大,当其为30∶70时,SiC耐磨材料的性能较优,其体积密度和显气孔率分别为2.66 g/cm3和3.95;,磨损量为0.11 g/min,硬度和抗折强度分别为2774 HV和185 MPa.SiC耐磨材料较优异的烧结性能和力学性能可归因于新生成的Y2Si2O7和3Al2O3·2SiO2充填于SiC颗粒间所起的强化作用.     

大口径轻质SiC反射镜的研究与应用

介绍了大口径轻质碳化硅反射镜镜坯的基本结构、性能测试指标、国内应用及发展前景;阐述了碳化硅凝胶注模成型（Gel-casting）、反应烧结SiC（RB-SiC）与压力成型、常压烧结SiC（SSiC）两种国内主要制备大口径轻质碳化硅反射镜的方法;并对两种方法制备得到的ø1.45 m碳化硅镜坯的性能、测试数据及光学加工后的光学特性进行分析和比对,提出存在的问题,以供商榷,进而促进国内大口径轻质碳化硅反射镜的研究和发展。