Electron microscopy study of contact layers in n-type 4H-SiC after diffusion welding

In the present work the results of transmission electron microscopy (TEM) and electron diffraction investigations of subcontact layers in n⁰-n^- 4H-SiC epistructure after diffusion welding (DW) are given. TEM examinations show that at the boundary between aluminium and silicon carbide the interface layer of ~ 25 nm thickness exists and this layer is of strip character. The image of contact area obtained in diffracted SiC rays (dark field) apparently confirms that stripy zone belongs to silicon carbide. Diffraction picture obtained from bulk zone of silicon carbide looks like monocrystalline, but the pattern obtained from the subcontact layer (stripy zone) gives the evidence of existence of small-grained phase. Deciphering of this electron-diffraction pattern reveals the presence of such elements as residue SiC, Al, Si, and inclusions of graphite.