A new physics-based self-heating effect model for 4H-SiC MESFETs

A new self-heating effect model for 4H-SiC MESFETs is proposed based on a combination of an analytical and a computer aided design (CAD) oriented drain current model. The circuit oriented expressions of 4H-SiC low-field electron mobility and in-complete ionization rate, which are related to temperature, are presented in this model, which are used to estimate the self-heating effect of 4H-SiC MESFETs. The verification of the present model is made, and the good agreement between simulated results and measured data of DC I-V curves with the self-heating effect is obtained.     

A CAD oriented quasi-analytical large-signal drain current model for 4H-SiC MESFETs

This paper reports that a 4H-SiC MESFET (Metal Semiconductor Field Effect Transistor) large signal drain current model based on physical expressions has been developed to be used in CAD tools. The form of drain current model is based on semi-empirical MESFET model, and all parameters in this model are determined by physical parameters of 4H-SiC MESFET. The verification of the present model embedded in CAD tools is made, which shows a good agreement with measured data of large signal DC I-V characteristics, PAE (power added efficiency), output power and gain.     

Electrical and optical characteristics of vanadium in 4H-SiC

A semi-insulating layer is obtained in n-type 4H-SiC by vanadium-ion implantation. A little higher resistivity is obtained by increasing the annealing temperature from 1450 to 1650℃. The resistivity at room temperature is as high as 7.6×10⁶\Omega .cm. Significant redistribution of vanadium is not observed even after 1650℃ annealing. Temperature-dependent resistivity and optical absorption of V-implanted samples are measured. The activation energy of vanadium acceptor level is observed to be at about E_C-1.1eV.     

对“实验探究型”课堂教学模式的研究

中专教育是培养与21世纪我国现代化建设需求相适应的,具有全面综合素质的专业技术人才,传统的教育模式在某些方面不利于学生创性思维的充分发展,使学生的学习和思维方式受到一定的限制.因此,我们必须加强素质教育,在学校接受课本中的间接经验的过程中,还必须学会获取知识的途径     

Raman scattering studies on manganese ion-implanted GaN

This paper reports that the Raman spectra have been recorded on the metal-organic chemical vapour deposition epitaxially grown GaN before and after the Mn ions implanted. Several Raman defect modes have emerged from the implanted samples. The structures around 182 cm^-1 modes are attributed to the disorder-activated Raman scattering, whereas the 361 cm^-1 and 660 cm^-1 peaks are assigned to nitrogen vacancy-related defect scattering. One additional peak at 280 cm^-1 is attributed to the vibrational mode of gallium vacancy-related defects and/or to disorder activated Raman scattering. A Raman-scattering study of lattice recovery is also presented by rapid thermal annealing at different temperatures between 700 °C and 1050 °C on Mn implanted GaN epilayers. The behaviour of peak-shape change and full width at half maximum (FWHM) of the A₁(LO) (733 cm^-1) and E^H₂ (566 cm^-1) Raman modes are explained on the basis of implantation-induced lattice damage in GaN epilayers.     

Analytical model of electron transport characteristics for 4H-SiC material and devices

Based on 4H-SiC material parameters, three different analytical expressions are used to characterize the electron mobility as the function of electric field. The first model is based on simple saturation of the steady-state drift velocity with electric field (conventional three-parameter model for silicon). The second GaAs-based mobility model partially reflects the peak velocity in high electric fields. The third multi-parameter model proposed in this paper is more realistic since it well reproduces the drift velocity－field characteristics obtained by Monte Carlo calculations, revealing the peak drift velocity with subsequent saturation at higher electric fields. Thus, the drift velocity model presented in this paper is much better for device simulation. In this paper, the influence of mobility model on DC characteristics of 4H-SiC MESFET is calculated and the better accordance with the experimental results is presented with multi-parameter model.     

含温度载荷的管板变形的解析解

根据换热器结构形式建立了用于计算管板变形的力学模型,参考ASMEⅧ-1计算管板的有效弹性常数,并将外筒和换热管束分别等效为会因温度和压力载荷产生轴向变形的弹簧和弹性基础.应用Ritz法建立了管板挠度的解析解,将该解析解与三个不同规模换热器的有限元分析结果进行对比.结果表明,建立的解析解与有限元分析结果吻合良好,验证了推...     

废FCC催化剂与高炉灰催化木屑热解特性研究

将炼油废FCC催化剂(sFCCc)和炼钢高炉灰(BFA)两种典型工业废弃物作为催化剂应用于木屑快速热解过程中,探究了400-700℃木屑的催化热解反应特性。结果表明,两种催化剂均促进了液相产物向气相产物的转化,700℃、BFA催化条件下的气相产率最高为52.60%。sFCCc在500-600℃时具有更强的脱氧活性,气体产物中CO和CO₂产量更高。BFA在600-700℃时具有更高的缩聚脱氢活性,催化生成了更大量的多环芳香类化合物和H₂。热解油主要由酚类物质组成,sFCCc促进了甲氧基酚向苯二酚类物质转化。热解油FT-IR解析结果表明,sFCCc促进了C-O和C=O的脱除,导致酸类和酯类化合物减少,CO₂产率增加。     

非故意掺杂4H-SiC外延材料本征缺陷的热稳定性

采用电子顺磁共振（ESR）和低温光致发光（PL）技术,研究了退火温度对低压化学气相沉积法（LPCVD）制备的非故意掺杂 4H-SiC材料中本征缺陷稳定性的影响.结果发现,当退火时间为10 min和30 min时,本征缺陷浓度均随着退火温度的升高而增大,当退火温度达到1573 K时材料中本征缺陷浓度达到最大,继续升高退火温度将使材料中本征缺陷浓度迅速降低.退火温度对材料中本征缺陷的影响主要是由于退火中本征缺陷的稳定化过程及本征缺陷之间发生强烈的相互作用引起的. 关键词： 高温退火 本征缺陷 电子顺磁共振谱 光致发光     

Ni/4H-SiC肖特基势垒二极管的γ射线辐照效应

对制备的Ni/4H-SiC肖特基势垒二极管（SBD）进行了γ射线辐照试验,并在辐照过程中对器件分别加0和-30?V偏压.经过1?Mrad（Si）总剂量的γ射线辐照后,不同辐照偏压下的Ni/4H-SiC肖特基接触的势垒高度和理想因子没有退化,SiC外延层中的少子寿命也没有退化.辐照后器件的反向电流下降,这是由于器件表面的负界面电荷增加引起的.研究表明,辐照偏压对Ni/4H-SiC SBD的辐照退化效应没有明显的影响. 关键词： 碳化硅 肖特基 辐照效应 偏压