Physical properties of Si–Ge alloys in C2/m phase: a comprehensive investigation

A new phase of C2/m Ge₁₆ is first proposed in this paper. The structures and mechanical, anisotropic, electronic, transport and optical properties of Si–Ge alloys in the C2/m phase are studied using first principles calculations. All Ge₁₆ and Si_16−xGe_x alloys in the C2/m phase are proven to have mechanical and dynamic stability. By analyzing the three-dimensional (3D) perspective of the effective mass and Young's modulus, obvious anisotropies of transport and mechanical properties are found. Higher-resolution full band structures are obtained to determine the positions of the valence band maximum (VBM) and conduction band minimum (CBM). All materials have a higher photoelectron absorption than that of diamond Si. A high electronic mobility (16 527 cm² V⁻¹ s⁻¹) and hole mobility (3033 cm² V⁻¹ s⁻¹) are found in C2/m Si₈Ge₈ and Si₄Ge₁₂, respectively. Based on the large mobility and photoelectron absorption, the Si–Ge alloys in the C2/m phase are promising materials for electronics and optoelectronics applications. (paper)