Non-linear piezoelectricity in wurtzite ZnO semiconductors

In this work we explore the strain dependence of the piezoelectric effect in wurtzite ZnO crystals. We write the polarization in terms of the internal anion-cation displacement, the ionic and dipole charges and use ab initio Density Functional Theory to evaluate the dependence of all quantities on the strain tensor. We determine that similar to III-V semiconductors the piezoelectric effect is nonlinear in the strain tensor. We report the quadratic piezoelectric coefficients and a revised value of the spontaneous polarization. We find that in ZnO nanowires, the non-linear piezoelectric effect leads to predictions in some cases opposite to those obtained using the widely used linear model. (C) 2013 Elsevier Ltd. All rights reserved.