Cross-scale mechanical manipulation of mobile charges in centrosymmetric semiconductors via interplay between piezoelectricity and flexoelectricity

Abstract

Flexoelectricity, an electromechanical coupling between strain gradient and electrical polarization in dielectrics or semiconductors, has attracted significant scientific interest. It is reported that large flexoelectric behaviors can be obtained at the nanoscale because of the size effect. However, the flexoelectric responses of centrosymmetric semiconductors (CSs) are extremely weak under a conventional beam-bending approach, owing to weak flexoelectric coefficients and small strain gradients. The flexoelectric-like effect is an enhanced electromechanical effect coupling the flexoelectricity and piezoelectricity. In this paper, a composite structure consisting of piezoelectric dielectric layers and a CS layer is proposed. The electromechanical response of the CS is significantly enhanced via antisymmetric piezoelectric polarization. Consequently, the cross-scale mechanically tuned carrier distribution in the semiconductor is realized. Meanwhile, the significant size dependence of the electromechanical fields in the semiconductor is demonstrated. The flexoelectronics suppression is found when the semiconductor thickness reaches a critical size (0.8 µm). In addition, the first-order carrier density of the composite structure under local loads is illustrated. Our results can suggest the structural design for flexoelectric semiconductor devices.