Electromechanical field analysis of PN junctions in bent composite piezoelectric semiconductor beams under shear forces

In piezotronics, PN junctions usually possess both piezoelectricity and semiconductor properties. This allows them to be manipulated mechanically by external forces through the coupling between deformation and free carriers. For a conventional non-piezoelectric PN junction, however, the mechanical manipulation seems difficult to achieve. In this paper, we theoretically demonstrate that this problem may be addressed via structural design. A composite beam model consisting of a piezoelectric dielectric layer and two non-piezoelectric PN junction layers is proposed. Then its electromechanical response under three different types of shear loads is examined based on a one-dimensional phenomenological theory. Results show as expected that the electrical behaviors of the junction can be tuned mechanically when the external force is applied on the interface, which provides a new idea for the design of piezotronic devices. Further, the effects of the doping level, thickness ratio, and material combination are also investigated, providing a comprehensive understanding of the proposed composite model.