The effect of impurities on the ideal tensile strength of silicon

Using first-principles electronic structure calculations in the local-density approximation combined with lattice dynamics, we find that undoped silicon is stronger in tension along [111] than n-doped silicon. For p-type doping, a negligible effect is found on ideal tensile strength, whereas heavy n-type-doping causes a reduction of about 6%. The effect is interpreted in terms of the change in electronic structure with strain ε, and the change in the Fermi energy with doping. If E_CB (ε) is the contribution to the total internal energy from occupied conduction band states in n-type material, our results identify the slope of E_CB (ε) as the controlling influence on tensile strength, which we find to be reduced for silicon.