First-principles study on Al doped 4H-SiC

In this paper, by using first principles calculation based on density functional theory, 4H-SiC heavily doped model was established using CASTEP software. The crystal structure and electronic structure of p-type Al heavily-doped 4H-SiC prepared by laser irradiation of coated Al film have been calculated and studied. The band structure and densities of state corresponding to various doping concentration of Al were analyzed. The results show that the bandgap width decreases with the increase of Al atom doping concentration and the Fermi level enters the valence band, which reflects the characteristics of p-type semiconductor the laser doped 4H-SiC. Combined with the analysis of secondary ion mass spectrometry, the variation of Al doping concentration with depth was obtained. It was found that the uniform doping concentration of Al which is approximately 1×1020 cm–3 is in the depth range of 30 nm. It is proved that the KrF excimer laser can achieve heavy doping of Al atoms in 4H-SiC. With the increase of depth, the laser energy density decreases gradually, and the doping concentration of Al atoms in 4H-SiC decreases. The p-type semiconductor characteristics of 4H-SiC samples prepared by laser irradiation Al film doping were verified, and the variation of Al doping concentration with laser irradiation depth was obtained.