Novel electromechanical coupling theory of GaN HEMT structure under mechanical clamping

Abstract

As known, the piezoelectric polarization effect makes GaN HEMT have unique electrical characteristics and more widely applications compared with other III-V semiconductor devices. In this letter, a novel electromechanical coupling theory is proposed and verified for the first time for the GaN HEMT heterojunction structure by applying the mechanical clamping boundary conditions in piezoelectric constitutive equations. The total piezoelectric polarization defined as Pcouple in this new electromechanical coupling theory consist of three parts: the spontaneous polarization Psp, the strain-induced piezoelectric polarization Pstrain due to lattice mismatch in growth, and the bias dependent piezoelectric polarization PEz. The output and transfer characteristics of GaN HEMT have been simulated based on the new electromechanical coupling theory and verified in agreement with the experimental results in trend. This theory helps to extend the understanding of the basic physical mechanism of AlGaN/GaN interface and is of great significance to device design and application for GaN-based materials.