Imaging of carrier dynamics in semiconductor heterostructures by surface acoustic waves

Surface acoustic waves (SAW) are an ideal tool for the noninvasive detection of conductivity and carrier distributions in otherwise unstructured semiconductor systems. Here we demonstrate a technique that allows for spatially resolved experiments with a resolution of a few acoustic wavelengths. Extremely narrow acoustic paths, excited by tapered interdigital transducers, are employed to probe conductivity profiles. The method is used to resolve the spatial form of a photogenerated electron–hole plasma and allows for the direct observation of room-temperature drag and transport of electrons and holes in the coherent phonon wind of an intense SAW beam. By the application of a tomographic technique we are able to reconstruct 2D charge distributions.