Epitaxy of SiGe Layers by Ultrahigh Vacuum Chemical Vapor Deposition

Introduction　　Becausethepropertiescanbeadjustedbythestraindistributionandthepossibleintegrationwithstandardsilicontechnology,silicon-germanium(SiGe)heterosystemshavebecomemoreimportantinrecentyears.AnumberofinterestingelectronicandopticaldeviceshavebeendevelopedusingSiGe.Thesedevicesincludeheterostructurefieldeffecttransistors(HFET)[1,2],heterojunctionbipolartransistors[35],andinfrareddetectors[6,7].Futureprospectshaveencouragedthesearchforimproveddepositiontechniquesforsiliconandsilicon…     

X衍射线晶粒加宽线形分析的研究

从晶粒大小分布函数的假定出发，结合Ｆｏｕｒｉｅｒ分析方法的原理，导出了描述Ｘ射线衍射线形的积分表达式，并以此同实验测出的衍射线形进行拟合，结果同传统的Ｆｏｕｒｉｅｒ分析方法得出的结果符合得很好。由于采用了拟合法以及理论上得到的更为符合实际的线形积分表达式，就可以避免传统Ｆｏｕｒｉｅｒ分析方法所产生的弯钩效应，克服把柯西线形近似为晶粒加宽线形的不足，使得最后晶粒大小结果更为准确。     

HV/CVD Grown Relaxed SiGe Buffer Layers for SiGe HMOSFETs

High-vacuum/chemical-vapor deposition (HV/CVD) system was used to grow relaxed SiGe buffer layers on Si substrates. Several methods were then used to analyze the quality of the SiGe films. X-ray diffraction and Raman spectroscopy showed that the upper layer was almost fully relaxed. Second ion mass spectroscopy showed that the Ge compositions were step-graded. Transmission electron microscopy showed that the misfit dislocations were restrained to the graded SiGe layers. Tests of the electrical properties of tensile-strained Si on relaxed SiGe buffer layers showed that their transconductances were higher than that of Si devices. These results verify the high quality of the relaxed SiGe buffer layer. The calculated critical layer thicknesses of the graded Si1-xGex layer on Si substrate and a Si layer on the relaxed SiGe buffer layer agree well with experimental results.