报告题目：Analysis of Piezoelectric Semiconductor Structures
报告人： Prof. Jiashi Yang （University of Nebraska-Lincoln, USA）
In piezoelectric semiconductors, the motion of charge carriers can be affected by mechanical fields through the accompanying electric field produced via piezoelectric coupling. Since the nineteen sixties, there have been efforts on using piezoelectric semiconductors to make acoustic wave devices where the effect of mechanical waves on electric currents is called the acoustoelectric effect. Relatively recently, various piezoelectric semiconductor structures have been synthesized such as ZnO fibers, tubes, belts, spirals and films. They have been used to make energy harvesters for converting mechanical energy into electrical energy, field effect transistors, and various physical as well as chemical sensors. Piezoelectric semiconductors are also used in nano-structures such as quantum wells, dots and wires. The study of piezoelectric semiconductor materials and devices is growing rapidly. Part of the study has formed a new research area called piezotronics and piezo-phototronics.
This presentation is a summary of our recent work on theoretical analysis of piezoelectric semiconductor structures such as beams and plates. It includes the effects of doping of impurities, the formation of PN junctions, static, time-harmonic, and transient dynamic motions. The macroscopic drift-diffusion theory of piezoelectric semiconductors consisting of the linear momentum equation, the charge equation of electrostatics, and the conservation of holes and electrons is employed. The equations are simplified by linearization for small carrier concentration perturbations. One- and two-dimensional equations for beams and plates in extension and bending are derived. Solutions to a few basic problems are obtained. Various electromechanical fields are calculated and examined. Composite beams of piezoelectric dielectrics and nonpiezoelectric semiconductors are also discussed.
Jiashi Yang is a professor at the Department of Mechanical and Materials Engineering of University of Nebraska-Lincoln. He received his B.E. and M.E. in Engineering Mechanics in 1982 and 1985 from Tsinghua University; M.S. in Mechanical Engineering in 1988 from Syracuse University; and Ph.D. in Civil Engineering in 1993 from Princeton University. He was a Postdoctoral Fellow from 1993 to 1994 at the University of Missouri-Rolla; and from 1994 to 1995 at Rensselaer Polytechnic Institute. He was employed by Motorola, Inc. as an engineer from 1995 to 1997. Since 1997 he has been an Assistant, Associate, and Full Professor at the University of Nebraska-Lincoln.