A comparative study of changes on electronic properties between Si and Ge nanowire along [110] direction by application of uniaxial strain

In this review paper, we compare the effect of uniaxial strain on the electronic properties of Si and Ge nanowire along [110] direction based on density-functional theory (DFT). Generally, bulk Si & Ge possess indirect bandgap while both nanowires possess a direct bandgap. The diameters of the nanowires from 1.2-3.7 nm are studied. As bandgap is inversely proportional to wire diameter it can be modulated by uniaxial strain that is applied to the nanowires. Compressive strain increases the bandgap while tensile strain reduces the bandgap for smaller diameter nanowires (~1.2 nm). But when the diameter is increased, bandgap shows parabolic behavior in the compressive strain region. In addition, effective masses of charge carriers can be changed by applying uniaxial strain. Tensile strain increases the effective mass of the hole while compressive strain increases the effective mass of the electron. This paper comparatively shows the bandgap and effective masses of charge carriers are changed due to uniaxial strain for various wire diameters (1.2-3.7 nm) of Si & Ge nanowires.