Relative stabilities of Si polytypes under the biaxial stress: A first principles study*

Silicon is one of the most important elements for semiconductors and usually takes the diamond structure (3C). On the other hand, several experimental studies for synthesis of other polytypes of Si (2H [1] and 4H [2] phases) have been reported. The synthesis of the polytypes is of high importance and high interest due to the differences of electronic properties including the variation of band gap values and the effective mass values. In this work, we have studied the possibility of CVD homoepitaxial growth of the hexagonal Si polytypes on the 3H (3C) Si substrate under compression with biaxial stress. From the density functional theory (DFT), it is found that the 4H phase takes lower total energy than the 3H (3C) phase at the reduced lattice constant α. Hence, the 4H phase may grow on the (111) substrate under the biaxial stress. Furthermore, from the density functional perturbation theory (DFPT), it is found that there is possibility to synthesize not only the 4H phase but also the 2H phase at higher temperatures [3].

 

[1] R. H. Wentorf, Jr. and J. S. Kasper, Science 139, 338 (1963).

 [2] S. Pandolf et al., Nano Lett. 18, 5989 (2018).

 [3] R. Kita, M. Toyoda, and S. Saito, Phys. Rev. Mater. 5, 063402 (2021)