Zur Diffusion lichtelektrisch angeregter Elektronen und über dendc-Effekt an ZnO-Kristallen

Abstract

In the volume of ZnO single crystals electrons are excited into the conductionband by two-photon absorption of ruby laser light at room temperature. At the edge of the irradiated region there occur a gradient in the concentration and a diffusion of the electrons. As the diffusion is anisotropic in Li-doped ZnO crystals, an axial quadrupole results, which influences measurable charges on the electrodes of the crystal. From the amount of the charge, the product of drift mobility and drift lifetime μ_Dτ_D can be calculated for Li-doped ZnO. Cu-doped ZnO shows no anisotropic diffusion. By means of photoconductivity experiments, μ_Dτ_D can be obtained in this case. Finally the coefficients of thedc-effect of ZnO are measured with a Neodymium laser.