SAW tomography-spatially resolved charge detection by SAW in semiconductor structures for imaging applications

The interaction of surface acoustic waves and free carriers in a nearby semiconducting sheet yields an extremely sensitive method for sensing electrical and optical signals. In the present work we demonstrate the spatially resolved detection of optical signals with a spatial resolution of a few acoustic wavelengths. We exploit the high selectivity of so-called tapered transducers to excite adjustable narrow acoustic beams allowing for the scanning of photogenerated charge distributions. Using a special layout, both x and y-coordinate of the optical signal are readily read out in a single frequency sweep. Complex 2D image information can be gathered when a tomographic imaging technique is applied.