Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10707394 | Journal of Crystal Growth | 2011 | 4 Pages |
Abstract
Polytypism in semiconductors including SiC and ZnS is systematically investigated using ab initio pseudopotential approach for the total energy calculations with/without vacancy in 3C (zinc blende), 6H, 4H, and 2H (wurtzite) structures. The calculated total energy E among 3C, 6H, 4H, and 2H implies that 3C and 4H are the most favorable for SiC, while ZnS prefers 3C. Furthermore, it should be noted that the energy differences ÎE among these four structures are very small without the explicit dependence on the hexagonality, whereas the ÎE strongly depends on the hexagonality for AlN and Si without polytypes. The ÎE for SiC with vacancy explicitly reveals the most stable structures, such as 6H with Si-vacancy and 4H with C-vacancy. On the other hand, ZnS with vacancy prefers 2H with S-vacancy. These results qualitatively agree well with the experimental findings, where 3C appears at low temperatures, while 6H and 4H for SiC and 2H for ZnS are favored at high temperatures enhancing vacancy formation. In particular, the calculated vacancy formation energies suggest that C- and Si-rich conditions, respectively, prefer 6H-SiC and 4H-SiC, while 2H-ZnS appears independent of conditions. Consequently, these results suggest that the vacancy formation plays an important role in the polytypism in semiconductors.
Keywords
Related Topics
Physical Sciences and Engineering
Physics and Astronomy
Condensed Matter Physics
Authors
Tomonori Ito, Tomoyuki Kondo, Toru Akiyama, Kohji Nakamura,