Analysis of piezoelectric PN homojunction and heterojunction considering flexoelectric effect and strain gradient

In this paper, a one-dimensional model of piezoelectric PN junction under static extension has been established. The combined influences of flexoelectricity and strain gradient are taken into account simultaneously. Closed-form expressions for the distributions of carrier concentrations and electromechanical fields of piezoelectric PN homojunction and heterojunction are given. It is observed that flexoelectricity and strain gradient have a significant impact on the distributions of electromechanical fields along the junction. The distributions of electromechanical fields for homojunction are origin-symmetric approximately, while the corresponding results for heterojunction show evident asymmetric behaviors. The electromechanical coupling behaviors of PN junction are enhanced under the action of external forces. Compared with homojunction, the distributions of electromechanical fields for heterojunction are more sensitive to the action of external force. This research offers a new idea to tune carrier transport and electromechanical characteristics of PN junction.