Strain effect analysis on the electrical conductivity of Si/Si1−xGex nanocomposite thin films

• Strain effect on electrical conductivity of Si/SiGe nano thin films is investigated.
• A modeling approach for the strain effect analysis is presented.
• 1% External strain can cause a change of up to 40% in the electrical conductivity.
• The observed strain effect is explained through detailed subband calculations.

In this work, the effect of various externally applied strains on the electrical conductivity of Si/Si1−xGex nanocomposite thin films is studied. A degenerate two-band k ⋅ p theory is utilized to calculate the variation of the electronic band structure in the semiconductor nanocomposite thin films as a function of externally applied strains. The strain-dependent electrical conductivity of the material is computed by using a two dimensional real-space Non-Equilibrium Green’s Function (NEGF) self-consistently coupled with the Poisson equation. In the analysis, [1 0 0] uniaxial, [1 0 0]/[0 0 1] and [1 0 0]/[0 1 0] biaxial strains are considered for the through-thickness electron transport in [1 0 0] direction. Numerical results demonstrate that the external strains have a significant influence on the electrical conductivity of the nanocomposite thin films. We show that the electrical conductivity variation can be attributed to combined effects of strain-induced splitting of the conduction band edges and change in band offset, electron quantum confinement, and size of the inclusion material in the thin films.