SiC多型体的电子结构和光学特性研究(英文)

ELECTRONIC STRUCTURE AND OPTICAL PROPERTIES OF SiC POLYTYPES

在局域密度近似下 ,采用平面波超软赝势法对 Si C多型体的能带和光谱特性进行了研究。计算了 4种 Si C多型体的能带、介电常数等并进行了比较。计算表明 :4H-Si C导带最低点在布里渊区 M点 ,6H-Si C导带最低点在布里渊区 ML 线上 U( 0 ,0 .1 76,0 ) ( 2 π/ a)点。在布氏区垂直于 Z轴方向的AH和 L H段能带是二重简并的。能带得介电常数的计算表明 Si C是各向异性材料。局域密度近似下的密度泛函理论对能隙的计算结果小于实验结果。

Unsing the first principle plane wave ultrasoft pseudo potential method of density functional theory (DFT) in the local optical approximation (LDA), the electronic structure and the linear optical properties of SiC polytypes are investigated. Results on band structure are presented and compared. Optical properties of the SiC polytypes up to 40 eV energy of a photon are calculated and the dielectric functions are resolved into components perpendicular and parallel to the z axis. Calculations find the conduction band minima in 4H- at M point and in 6H SiC at U(0,0.176,0)(2π/a) point in the Brillouin zone.Bands versus wave vectors along the lines AH and LH on the surface of the BZ are twofold degenerate in crystals with C 6v 4 point group. There is substantial anisotropy in different directions in the SiC crystal structure. The DFT LDA band gap is smaller than the experimental data.