THE EFFECTS 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 epsilon, and the change in the Fermi energy with doping. If E(CB)(epsilon) 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)(epsilon) as the controlling influence on tensile strength, which we find to be reduced for silicon.