Influences of piezoelectric positive-negative junction on the multi-field coupled waves propagation in the piezoelectric semiconductor

The influences of the piezoelectric positive-negative junction (PN junction) between two semiconductors with different doping types on the multi-field coupled wave propagation are studied in the present work. The layered structures of semiconductors are often used in intelligent devices, and the PN junction plays an important role for performance improvement. Due to the migration and diffusion of carriers, the electric potential and concentration of the carrier are graded distribution in the PN junction. This inhomogeneity results in the reflection and transmission of coupled waves, which are the complex of multiple physical fields including the mechanical, electric, and carrier fields. The state transfer equation method is used to obtain the transfer matrix of the PN junction, and the reflection and transmission waves under the plane strain situation are evaluated numerically. The energy fluxes of the reflection and transmission waves are estimated and used to validate the numerical results by the check of energy conservation. It is found that PN junction effects hinder the wave propagation and drastically enhance the reflection ability of the interface, especially, on the coupled carrier waves, and thus are very important and cannot be ignored for the wave propagation problem. The influences of external applied stress and bias electric field are also discussed.