Selective Etching of Micropipes During Initial Homoepitaxial Growth Stage on Nearly On-Axis 4H-SiC Substrates

Abstract

The initial homoepitaxial growth behavior on nearly on-axis 4H-SiC substrates was investigated. We have observed circular etch pits on the surface of on-axis substrate in the presence of source gases. However, there were no circular etch pits on the surface of off-axis substrates. In addition, the surface etched by H2 gas did not show circular etch pits even on nearly on-axis substrates. The shape of the circular etch pits was similar to spiral one. The initial growth behavior of epilayers was also investigated with various C/Si ratios of source gases (0.6<C/Si<2.0). The circular etch pits were observed independent of the source gas ratio. It implies that the source gases promote the selective etching, while the H2 gas etches SiC defect-independent. The spiral shape of etch pits seems to be produced from the screw dislocation with large burgers vector of micropipes. Therefore, the circular shape etch pits were not observed in an off-axis substrate.