First principle simulations of piezotronic transistors

Piezoelectric semiconductors, such as wurtzite structured ZnO, GaN, and InN, have novel properties owing to piezoelectric polarization tuned/controlled electronic transport characteristics. Under an externally applied strain, piezoelectric charges are created at an interface or junction, which are likely to tune and modulate the local band structure. Taking an Ag-ZnO-Ag two-terminal piezotronic transistor as an example, strain-dependent piezoelectric charge distributions and modulation of Schottky barrier heights (SBHs) at metal/semiconductor interfaces have been investigated by the first principle simulations. The width of piezocharge distribution is calculated by the density function theory and the Poisson equation. The modulations of SBHs at two interfaces show opposite trend under the applied strain. This study not only provides an understanding about the piezotronic effect from quantum theory point of view, but also a new method to calculate the key parameter for optimizing the design of piezotronic devices. (C) 2014 Elsevier Ltd. All rights reserved.