Abstract:

This paper theoretically investigates the influence of a cylindrical PN junction on the propagation characteristics of shear cylindrical waves (SCWs) in an infinitely long piezoelectric semiconductor (PS) concentric cylinder structure. This PS concentric cylinder structure is composed of three regions: an inner PS cylinder, an outer PS cylindrical shell, and a cylindrical PN junction at the interface between the two aforementioned regions. First, the basic equations of the PS concentric cylinder structure are derived, taking into account the coupling of the mechanical displacement, electric potential, and charge carrier perturbation in the cylindrical coordinate system. Next, a mathematical model for the SCWs in this PS concentric cylinder structure is established, utilizing the spectral method and considering the physical characteristics of the cylindrical PN junction. Finally, the dispersion and attenuation curves of the SCWs are numerically calculated to discuss the influence of the interface effect resulting from the cylindrical PN junction. It is found that the existence of a cylindrical PN junction can either reduce or enhance the mechanical-to-electrical energy conversion, which is closely related to the doping mode, doping concentration, and curvature radius of the cylindrical interface. A reasonable design of the aforementioned parameters can optimize the wave motion in acoustic equipment formed by PS media with different frequencies or wavelengths. The construction and resolution of the mathematical model as well as the analysis of physical mechanisms can offer theoretical guidance for improving the efficiency of energy conversion from mechanical energy to electrical energy and optimizing the acoustic performance of energy harvesting devices.

Key words: piezoelectric semiconductor (PS), cylindrical PN junction, layered cylinder structure, dispersion relation, spectral method