High performance piezotronic devices based on non-uniform strain

Piezotronic and piezophototronic devices have attracted increasing interests in self-powered sensor, piezotronic logic units and flexible energy-harvesting devices. The carrier transport characteristics can be effectively tuned by the piezoelectric charges induced by an externally applied strain, which has been extensively investigated for a uniform strain case. However, a non-uniform strain can induce a giant piezoelectric field at the interface to significantly enhance the piezotronic effect. In this paper, we propose a model that a mechanical stress is gradient distributed along a piezoelectric-semiconductor material. The electric properties of piezotronic p-n junction with non-uniform strain has been simulated by using the finite element method, including the currentvoltage characteristics and carrier concentration. The piezotronic p-n junction involving strain gradient possesses ultrahigh sensitivity (the gauge factor over 2500) due to the enhancement of piezoelectric constant. This investigation further broadens the fundamental theory of piezotronics and offers guidance for designing ultra-high performance piezotronic devices.