AlN/Si(111)复合衬底上4H-SiC薄膜的异质外延

Heteroepitaxial 4H-SiC Films Growth on AlN/Si(111) Composite Substrates

利用化学气相淀积(CVD)的方法在AlN/Si(111)复合衬底上成功实现了4H-SiC薄膜的异质外延生长,用X射线衍射(XRD)、扫描电子显微镜(SEM)、阴极荧光(CL)等方法对所得样品的结构特征、表面形貌和光学性质进行了表征测量。XRD测量结果显示得到的SiC薄膜的晶体取向单一;室温CL结果表明所得SiC薄膜为4H-SiC,且随着生长温度的升高,SiC薄膜的CL发光效率提高。生长温度、反应气源中C/Si比等工艺参数对SiC薄膜的外延生长及其性质影响的研究表明在AlN/Si(111)复合衬底上外延4H-SiC的最佳衬底温度为1230～1270℃比通常4H-SiC同质外延所需的温度低200～300℃;较为合适的C/Si比值为1.3。

The 4H-SiC films heteroepitaxially deposited on AlN/Si（111） substrates by chemical vapor deposition （CVD） are investigated in this work. X-ray diffraction （XRD）, scanning electron microscope （SEM） and cathode illumination （CL） are used to analyze the structure characters, surface morphology and optics properties of the samples. The XRD spectrum shows that the SiC films have single （0006） orientation. The CL spectra indicates that the type of the prepared SiC films is 4H, and the CL efficiency of SiC films enhances with the increase of the growth temperature. It is found that lower substrate temperature is not beneficial for Si and C atoms to select the proper sites, leading to poor crystalline quality. While higher substrate temperature enhances the etching effect of H2 and desorption of absorbed atoms, which goes against the film growth. In addition, the ratio of C/Si influences on the growth of SiC as well. Excess Si results droplets on the surface, while excess C causes Si vacancies in the material. From these experiments, we point out that the preferred substrate temperature for 4H-SiC heteroepitaxy is between 1230℃ and 1270℃, the proper ratio of C/Si equals to 1.3.