Studies of band-gap differences in SiC polytypes

• Main Authors: Li-Ting Mei, 梅麗庭
• Other Authors: Ching Cheng
• Format: Others
• Language: en_US
• Published: 1993
• Online Access: http://ndltd.ncl.edu.tw/handle/66118033817495164884

碩士 === 國立成功大學 === 物理研究所 === 81 === Silicon carbide froms dozens of different structures by stacking identical SiC double layers in different stacking sequences. The majority of the physical properties of SiC polytypes are very similar as the environments of atoms are identical up to the second nearest neighbour for all polytypes. However, the band-gap different is as large as 0.9 eV. In the present studies, we used the nearest-neighbour tight-binding model which assumes the interatomic interactions are the same for all the polytypes to calculate the band structures of SiC polytypes. The large band-gap difference is obtained and the band structure of the zincblende SiC is more reasonable than those previously generated ones. It is found that the large band-gap differece is due to the large variations in the first conduction bands of differenr polytypes. The top valence bands for different polytypes are almost the same. The physical properties which do not involve excitations are therefore expexted to be similar for different polytypes. Investigations of the effect of the interatomic interactionson the band-gap difference showed that the crucial factor is the pp.pi. inter- action bbetween atoms.