We present a theoretical study on the equilibrium state of a PN junction, which is created by two piezoelectric semiconductor half spaces doped oppositely, based on the equations of linear piezoelectricity and the conservation of charge for holes and electrons. The nonlinearity associated with the drift currents of electrons and holes, which appears as products of the unknown carrier concentrations and the unknown electric field, is linearized for small carrier concentration perturbations. An analytical solution is rigorously derived, which is able to show the shaping of the PN junction near the interface. The electromechanical fields and concentrations of electrons and holes near the interface of the PN junction, and the forward-bias current-voltage characteristics of the PN junction under different applied stresses, are calculated and discussed. The effects of a few physical parameters on the properties of the PN junction are investigated as well.

We study the extension of a composite fiber of piezoelectric dielectrics and nonpiezoelectric semiconductors. A theoretical analysis is performed using a one-dimensional model. It is shown that mechanical loads cause redistribution of mobile charges in such a composite fiber. Thus, the composite fiber exhibits piezotronic couplings like a homogeneous piezoelectric semiconducting fiber. The couplings are a product property of the composite, enabling the design of piezotronics devices beyond materials with direct piezotronics couplings. The basic behavior of the composite fiber and the effects of various parameters on piezotronic couplings are calculated and examined. It is observed that piezotronic couplings in these fibers are sensitive to material and geometric parameters and can be optimized through design.

Based on three-dimensional equations of piezoelectric semiconductors, we take flexoelectricity into consideration to develop a deformation–polarization–carrier coupling analysis model for the bending of a piezoelectric semiconductor (PS) composite bilayer, which is composed of a piezoelectric semiconductor layer and an elastic layer. Using the derived equations, we investigate the macroscopic responses, such as the distribution of electromechanical field and carrier concentration, of the PS composite bilayer with bending deformation. The induced polarization in the PS composite bilayer exhibits an apparent size-dependent property due to the flexoelectric coupling effect, and thus has a remarkable influence on the piezotronic effect in the PS composite bilayer with nano-thickness. The obtained results are useful for designing novel piezoelectric semiconductor devices.