Abstract:We made a theoretical study of the carrier distribution and electromechanical fields in a free piezoelectric semiconductor rod of crystals of class 6 mm. Simple analytical expressions for the carrier distribution, electric potential, electric field, electric displacement, mechanical displacement, stress, and strain were obtained from a 1D nonlinear model reduced from the 3D equations for piezoelectric semiconductors. The distribution and fields were found to be either symmetric or antisymmetric about the center of the rod. They are qualitatively the same for electrons and holes. Numerical calculations show that the carrier distribution and the fields are relatively strong near the ends of the rod than in its central part. They are sensitive to the value of the carrier density near the ends of the rod.

Herein, a multiferroic composite semiconductor (MCS) fiber, in which the carriers transport behaviors can be effectively controlled by applying a magnetic field, is proposed. The fiber consists of two outer piezomagnetic (PM) layers, two piezoelectric (PE) layers, and a semiconducting core, and hence exhibits the comprehensive magneto-electro-semiconductive (MES) coupling effects. Based on the basic equations of multiferroic composites and the drift-diffusion model of currents in semiconductor physics, a 1D theoretical model for the laminated MCS fiber with the MES coupling effects is presented, and an analysis of the extensional deformation induced by a magnetic field is conducted. The electrons move toward one end of the fiber under the PE field resulting from the MES coupling mechanism. As a result, this leads to the redistribution of electrons in the fiber. Theoretical results show that the magnetic field as well as the initial concentration of carriers and the volume fraction of the PM or PE layer have obvious effects on the carriers transport properties and mechanical behaviors of the MCS fiber. Compared with the mechanical tuning method of piezotronics, such a magnetic field based tuning method via the MES coupling effects has some advantages because it is remote and contactless.

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Piezoelectric semiconductor (PS) nanostructures have a huge application potential in flexible electronic devices. We study the nonlinear multi-field coupling mechanical behaviors of axially loaded PS rods by taking the von Kármán type of nonlinear strain–displacement relations into account. The one-dimensional equations for extensional PS rods with the geometric nonlinearity are presented. The analytical solutions for an axially loaded PS rod with open-circuit and electrically isolated boundary conditions at the two ends are obtained based on the classical perturbation method. The zeroth-order perturbation solution is exactly the same as the linearized solution. The influences of the first- and second-order solutions on the multi-field coupling responses of the PS rods under different axial loads are investigated.