La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 La 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La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La元素,形成P型间接半导体,带隙宽度下降为0.886 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La的5d轨道与6H-SiC的sp3轨道杂化主要贡献在价带部分,而对导带的贡献相对较小,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,其中第一个介电峰是由sp3杂化轨道上的电子跃迁到La原子5d轨道上产生.未掺杂6H-SiC,在能量为10.31处吸收系数达到最大值,掺杂后在能量为7.35 eV处,吸收系数达到最大值.

The electronic structures and optical properties of undoped and La 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 La doped 6H-SiC is also an indirect bandgap semiconductor,whose gap is reduced to 0.886 eV,and it is the type of p.The electronic orbits of Si-3s and C-2s mainly contribute to the low energy zone of valence band,whereas the electronic orbits of Si-3p,Si-3s,C-2p mainly contribute to the high energy zone of conduction band.The orbital hybridization of the 5d electronic orbit of La-doped and the sp3 electronic orbit of the 6H-SiC mainly contributes to the high energy zone of valence band,but scarcely contributes to the conducton band.The conductivity of the La-droped is improved.The dielectric peak of un-droped 6H-SiC is dut to the transition of valence band electrons to conduction band electrons.Two dielectric peak appear in the La-droped 6H-SiC in whch the first dielectric peak is due to the transition of the sp3 electronic orbit to the 5d electronic orbit.The maximum of absorption coefficient of un-droped 6H-SiC is the photon energy of 10.31 eV and the maximum of absorption coefficient of la-droped 6H-SiC is the photo energy of 7.35 eV.