Towards band gap engineering via biaxial and axial strain in group IV crystals

• Published in: Computational materials science 2020-08, Vol.181, p.109729, Article 109729
• Main Authors: Janik, Norbert, Scharoch, Pawel, Kudrawiec, Robert
• Format: Article
• Language: English
• Subjects: DFT; Electronic structure; Group IV; Semiconductors; Strains
• ISSN: 0927-0256; 1879-0801
• DOI: 10.1016/j.commatsci.2020.109729

•Physical properties of strained C, Si, Ge and Sn dimond-like crystals studied.•Structural and elastic properties evaluated.•Strain dependent changes in band structures studied.•Effective masses and examples of related mobilities calculated.•Deformation potentials found. [Display omitted] Applying strain is one of major ways for tuning the electronic structure. In this work, DFT based ab initio studies of the effect of strain on electronic structure of group IV crystals were performed. Isotropic as well as axial and biaxial strains with respect to [100], [110] and [111] directions were considered. First, the structural and elastic characteristics were evaluated. The band structures evolution were represented by changes in energy gaps between valence band maximum at the Γ point of the Brillouin Zone and conduction band minima at Γ, as well as minima lying along Λ and Δ lines. The important and known features observed are: sharp non-smooth behavior close to zero strain, the removal of the star degeneracy along Λ and Δ lines, the transitions from indirect to direct band gap as well as closing/opening the gaps. The typical deformation potentials were calculated for Si and Ge directly from ab initio data, using the slab method for establishing unified energy reference point. The evaluated effective masses in valleys along Λ and Δ lines exhibit a sudden increase in electron or hole effective masses under small strains, which is also reflected in significant changes in carrier mobility. An excellent agreement of computational results with available experimental data is observed, except for the deformation potentials related to the VB top absolute position, whose values seem to remain still an open question.