Nondestructive evaluation of electrical properties of semiconductors using SAW

This work presents a study of the electrical properties of semiconductors using the interaction between surface acoustic waves and a semiconductor in the separated medium configuration (the SAW convolver). This study has been conducted towards developing a new technique for nondestructive evaluation of semiconductor surfaces using surface acoustic waves. The semiconductor is placed a small distance above the delay line, with a uniform airgap between the two media. Although there is no mechanical contact between the two media, the electric fields associated with the surface acoustic waves penetrate into the semiconductor and interact with the free carriers. As a result of this nonlinear interaction, the SAW is attenuated, there is a change in the SAW velocity, and dc acousto-electric voltages are developed across the semiconductor. In the case of two oppositely propagating surface waves, voltage proportional to the convolution of the two input voltages is also generated.