Imaging of acoustic charge transport in semiconductor heterostructures by surface acoustic waves

We demonstrate room-temperature acoustic charge transport of electrons and holes in an InGaAs/GaAs heterostructure. The carriers are optically generated by interband absorption and then separated, stored, and transported in the piezoelectric potential superlattice of a surface acoustic wave. The charge distribution is detected with a spatial resolution of a few acoustic wavelengths by a second orthogonal probe beam, genererated by so-called tapered transducers. The image information is given as a phase shift signal in frequency space and allows for the direct comparison of the number of generated and transported carriers. Regions of mere carrier drag and full carrier capture and transport are observed simultaneously. © 1999 American Institute of Physics.