Adjusting the electromechanical coupling behaviors of piezoelectric semiconductor nanowires via strain gradient and flexoelectric effects

In this paper, the strain gradient is introduced to tune the semiconducting performance of piezoelectric semiconductor (PSC) nanowires by changing their cross sections. A one-dimensional model of the PSC nanowire with a non-homogeneous cross section under axial extension is established. The combined influences of piezoelectricity and flexoelectricity resulting from the strain gradient are taken into account. Approximate closed-form solutions for the distribution of carriers and electromechanical fields of the PSC nanowire are given. The effects of strain gradient, flexoelectricity, and initial carrier concentration on the distribution of carriers, electric field, electric potential, and displacement are discussed. It is observed that non-homogeneous PSC nanowires show strong size-dependent behaviors in connection with their cross-sectional diameters. The strain gradient and flexoelectric effect enhance the electromechanical coupling effect. This research provides a new way to tune inner carrier distributions and electromechanical characteristics for piezoelectric semiconductor devices.