Acoustoelectric current saturation in c-axis fiber-textured polycrystalline zinc oxide films

Acoustoelectric current saturation, which until now has only been observed in piezoelectric single crystals, is observed in thin polycrystalline zinc oxide films. Epitaxial ZnO films on c-plane sapphire and textured ZnO polycrystalline films on fused silica both exhibit current saturation phenomenon. The values of the saturation current densities are in the range 10(5)-10(6) A/cm(2), depending on the carrier concentration in the film, with corresponding saturation electric fields of 3-5 X 10(3) V/cm. In addition to the current saturation, the electrical properties of the films degraded with the onset of the acoustoelectric effect but could be restored by annealing at 250 degrees C in a vacuum for 30 min. (C) 1996 American Institute of Physics.