4H-SiC晶体表面形貌和多型结构变化研究

Study on Surface Morphology and Polytype Transition of 4H-SiC Single Crystals

利用光学显微镜、显微拉曼光谱仪研究了4H-SiC晶体表面形貌和多型分布。显微镜观察结果显示4H-SiC小面生长螺蜷线呈圆形,沿<112-0>方向容易出现裂缝。裂缝两侧有不同的生长形貌。拉曼光谱结果显示缺陷两侧为不同的晶型,裂缝实际为晶型转化的标志。纵切片观察发现,在4H-SiC和15R-SiC多型交界处产生平行于<112-0>方向裂缝;15R-SiC多型一旦出现,其径向生长方向平行于<112-0>方向,轴向生长方向平行于<0001->方向。

The morphology of as-grown surface and polytype transition of 4H-SiC single crystals had been studied by optical microscopy and Raman spectroscopy.The round spiral steps were observed on the facet of 4H-SiC single crystals.There are some slits arrayed along 112-0direction.The surface morphologies at two sides of the slit interface are quite different.From the Raman spectra,it was known that different SiC polytypes are distributed on two sides of the slit.The slits are actually the signs of the polytype-transition process.By observing the longitudinal cut samples,we found that the slits only appear in the interface between 4H-SiC and 15R-SiC rather than other interfaces.As long as the 15R-SiC polytype is produced,it would grow along 0001- and extend radially along the 112-0direction.