Mechanical manipulation of electromechanical fields in multi-tunnel piezoelectric semiconductor thin film devices by creating localized transverse mechanical field excitations

Abstract

Piezotronics that couples piezoelectricity and semiconducting electronics of piezoelectric semiconductor (PS) materials through stress/strain is emerging field. To accurately depict physical and mechanical properties of two-dimensional (2D) PS thin film devices and comprehensively reveal underlying mechanisms from the perspective of device research, development, and applied science, a general theoretical framework called 2D higher-order phenomenological theory is established for the first time based on three-dimensional (3D) phenomenological theory and Mindlin plate theory, which is viewed as the basis for theoretically analyzing piezotronic effect and working mechanism in novel electronic devices. As the fundamental building blocks of novel piezotronic devices and a particular application example, the Kirchhoff bending deformation-dependent electromechanical fields about PS thin film bimorph devices have been solved successfully from static characteristic analysis viewpoint based on the established 2D phenomenological theory. Subsequently, a systematic investigation about local modulation and evolution of electromechanical fields has been carried out by creating localized external stimuli fields. To some extent, when there are local transverse mechanical load fluctuations within PS thin film devices, various physical fields alter because of deformation–polarization–carrier coupling effects, which affect the interaction between the mechanical deformations, polarization, and mobile charges in PS devices. A greater local transverse mechanical load yields a higher potential barrier and a deeper potential well, impeding the flow of charge carriers with low energy. Additionally, the potential barriers/wells (including their locations, heights/depths, distribution characteristics, and evolution laws) induced by local transverse mechanical loads are also influenced by other numerous physical and geometric parameters, e.g., load intensity, initial state electron and hole concentrations, thin film thickness, and rectangular element center coordinates. For piezotronic applications, the present research results not only provide a theoretical basis and tuning methodology for mechanically manipulating mobile charges related to potential barriers/wells, but also offer more flexibility for developing novel PS thin film devices with flexural deformations and transverse mechanical field excitations.