Study on the mechanical and optical properties of SiSn alloy by first principles

Abstract

Group-IV semiconductor alloys are important materials for in-chip and inter-chip optoelectronic applications in silicon-based high-performance large-scale integrated circuits. As photovoltaic materials, silicon–tin alloys can improve the performance of solar cells by expanding the spectral range and increasing absorption. Silicon–tin alloys have broad application prospects within the communication wavelength range of 1.0–1.6 µm. In this work, the lattice constants, mechanical and optical properties of Si32−xSnx alloy are calculated. Generalized gradient approximation with Hubbard correction parameter U was used for exchange-correlation potential. The calculation results demonstrate that the lattice constant and formation energy increase with increasing number of tin atoms. In terms of mechanical properties, Si32−xSnx alloy shows mechanical stability and strong resistance to resist external forces, and it is not prone to volume deformation. It shows metallicity and tends to be ductile. In terms of optical properties, the width of the bandgap of Si32−xSnx alloy decreases with increasing tin concentration. The absorption of visible and infrared lights of Si32−xSnx alloy increases with increasing tin concentration. The dielectric properties of Si32−xSnx alloy are significantly changed by the addition of tin atoms. Doping prolongs the carrier lifetime of Si32−xSnx alloy, and its lifetime reaches maximum when x equals 6.