P掺杂6H-SiC的第一性原理研究

First-Principles Study of P-Doped 6H-SiC

采用基于密度泛函理论的第一性原理赝势平面波法,计算未掺杂与P替换Si、C以及P间隙掺杂6H-SiC的电子结构与光学性质。结果显示未掺杂的6H-SiC是带隙为2.052 eV的间接带隙半导体,P替换Si、C掺杂以及P间隙掺杂6H-SiC带隙均减小,分别为1.787 eV、1.446 eV和0.075 eV,其中P间隙掺杂带隙减小幅度最大。P替换掺杂6H-SiC使得费米能级向导带移动并插入导带中,呈n型半导体。P间隙掺杂价带中的一条能级跨入费米能级,因此在禁带中出现一条P 3p杂质能级,P间隙掺杂6H-SiC转为p型半导体。替换与间隙掺杂使得6H-SiC的介电函数实部增大,介电函数虚部、吸收光谱、反射光谱与光电导率红移,其中P间隙掺杂效果最佳。通过P掺杂材料的电导率增强,对红外波段的利用率明显提高,为6H-SiC在红外光电性能方面的应用提供有效的理论依据。

The electronic structure and optical properties of intrinsic 6 H-SiC,P substituted for Si,C doped and P interstitial doped 6 H-SiC were calculated by the first-principles pseudopotential plane wave method based on density functional theory.The results indicate that intrinsic 6 H-SiC is an indirect band gap semiconductor with a band gap of 2.052 eV.The band gaps of the P substituted for Si,C doped and P interstitial doped 6 H-SiC decrease to 1.787 eV,1.446 eV and 0.075 eV,respectively.The interstitial doping band gap decreases the most.P substitutional doped 6 H-SiC causes the Fermi level guide band to move and insert into the conduction band,and the 6 H-SiC becomes an n-type semiconductor.One level of P interstitial doping valence band crosses into Fermi level,so a P 3 p impurity level appears in the gap band,and 6 H-SiC turns into p-type semiconductor.Substitutional and interstitial doping increase the real part of dielectric function of 6 H-SiC,while the imaginary part of dielectric function,absorption spectrum,reflection spectrum and photoconductivity redshift.Among them,P interstitial doped 6 H-SiC has the best effect.The conductivity of the material is enhanced and the utilization rate of the material in the infrared band is obviously improved by P doping.The results provide effective theoretical basis for the application of 6 H-SiC in infrared photoelectric performance.