Interface-fitted finite element modeling of mechanically and geometrically modulated piezoelectric PN junctions

Piezoelectric PN junctions can actively tune barrier configurations and carrier transport through mechanically induced piezoelectric fields, providing a novel pathway for applications in piezotronic transistors, mechanically gated diodes, and mechanical sensors. However, the multidimensional mechanisms by which mechanically and geometrically modulated piezoelectric PN junction responses remain insufficiently understood. In this paper, a theoretical framework for piezoelectric PN junctions is developed by imposing continuity of the electron and hole quasi-Fermi levels at the interface. Based on the constrained variational principle, an interface-fitted finite element method (FEM) is then proposed to address the interface model in piezoelectric PN junctions. Numerical results show that mechanical loading applied within the barrier region most effectively modulates the junction response. A larger tensile stress can induce a stronger piezoelectric field, which may cause barrier inversion and make minority carrier concentrations exceed majority carrier concentrations within the barrier region. Meanwhile, within the investigated range, an optimal combination of tensile stress and length-to-height ratio maximizes the output current density. The proposed interface-fitted FEM not only provides a quantitative tool for regulating the performance of piezoelectric PN junctions, but also offers a flexible framework for analyzing complex interface problems and designing practical piezotronic devices.