Ce掺杂6H-SiC电子结构和光学性质的第一性原理研究

First-principles study of electronic structures and optical properties of Ce doped 6H-SiC

采用基于密度泛函理论的第一性原理计算方法,对未掺杂及Ce掺杂6H-SiC的电子结构和光学性质进行理论计算.计算结果表明,未掺杂6H-SiC是间接带隙半导体,其禁带宽度为2.045 eV,掺杂Ce元素,带隙宽度下降为0.812 eV.未掺杂6H-SiC在价带的低能区,Si-3s、C-2s电子轨道对态密度的贡献较大,在价带的高能区,主要是由Si-3p、Si-3s、C-2p态组成.掺杂后Ce原子的4f轨道主要贡献在导带部分,掺杂后电导率提高.未掺杂时,只有一个介电峰,是价带电子跃迁到导带电子所致,掺杂后有两个介电峰,第一个介电峰是由于导带电子跃迁到Ce原子4f轨道上产生,第二个峰是价带电子向导带电子跃迁产生.未掺杂6H-SiC,在能量为10.31 eV处吸收系数达到最大值,掺杂后在能量为6.57 eV处,吸收系数达到最大值.

The electronic structures and optical properties of undoped and Ce-doped 6H-SiC were calculated by the first principle calculation method based on density functional theory.Undoped 6H-SiC is an indirect bandgap semiconductor,whose gap width is 2.045 eV and Ce doped 6H-SiC is also an indirect bandgap semiconductor,whose gap is reduced to 0.812 eV.The electronic orbits of Si-3s and C-2s mainly contribute to the low energy zone of valence band,and the electronic orbit of Si-3p,Si-3s and C-2p mainly contribute to the high energy zone of conduction band.The orbital hybridization of the 4f electronic orbit of Ce doping mainly contributes to conduction band,and the conductivity of the Ce-doped 6H-SiC is improved.The dielectric peak of undoped 6H-SiC is due to the electron transition from valence band to conduction band.There are two dielectric peaks in the Ce-doped 6H-SiC,where the first dielectric peak is the electron transition from the conduction band to the 4f electronic orbit,and the second peak is the electron transition from valence band to conduction band.The maximum of absorption coefficient of un-doped 6H-SiC is at the peak with photon energy of 10.31 eV and the maximum of absorption coefficient of Ce-doped 6H-SiC is at that with photon energy of 6.57 eV.