Nonlinear Effects in the Piezoresistivity of p‐Type Silicon

Piezoresistivity measurements are carried out on heavily doped ion‐implanted p‐type resistors on the surfaces of cantilever beams cut from a (100) silicon wafer. Tensile and compressive stresses, up to 85 MPa along the [110] direction, are applied by bending the beams with a micrometer. Nonlinear effects are clearly seen in the measurements where the resistor contains sections both parallel and perpendicular to the stress. The results are analyzed in terms of the first‐ and second‐order piezoresistance coefficients. Values of the piezoresistance coefficients are calculated using analytical expressions for the strain dependent energy‐wave vector relations of the valence bands and the known deformation potentials. The results of the calculations are compared with the experimental data including some earlier measurements reported in literature. The calculated values of the first‐order coefficients are found to agree fairly well with the experimental data. The calculated second‐order coefficients are able to describe the observed anisotropy in the nonlinear piezoresistivity of the second order in stress.