Analysis of electromechanical couplings and nonlinear carrier transport in flexoelectric semiconductors

Abstract

Abstract In recent years, a linearization method has been extensively employed to investigate the electromechanical fields and carrier distribution in flexoelectric semiconductors, where the assumption of a small perturbation of carrier concentration is adopted. However, this method fails to accurately describe the realistic physical process in which a considerable variation of carrier concentration takes place. Based on fully coupled nonlinear equations, this paper presents a finite element approach to study the electromechanical couplings and nonlinear carrier transport in flexoelectric semiconductors. This method is applied to calculate the electrostatic potential in a bent piezoelectric semiconductive nanowire (NW) going beyond simple considerations and to simulate the nonlinear current–voltage (I–V) characteristics of a mechanically loaded flexoelectric p–n junction. The results indicate that the inherently nonlinear drift of carriers gives rise to the asymmetric distribution of the electric potential relative to the NW axis in the upper body. Flexoelectricity brings about a remarkable enhancement in output voltage and is responsible for the linear variation of electric potential along the length direction of the NW unless close to two ends. Furthermore, the barrier height and I–V relations of a flexoelectric p–n junction can be effectively tuned by mechanical forces due to the flexoelectric effect, the effect of which relies on the size of the p–n junction configuration. This work is a good starting point to comprehend the coupling of flexoelectricity and nonlinear carrier transport in static and dynamic cases, and offers an effective approach to numerically deal with the issues involved in flexoelectronics and piezoelectronics at the nanoscale.