Charge transport mechanism in La:HfO₂

Currently, it is generally accepted that the charge transport in dielectrics is limited by the Coulomb trap ionization in a strong electric field (Frenkel effect). In the present work, the charge transport mechanism in La:HfO2 was experimentally studied, and four theoretical conductivity models-the Frenkel effect of Coulomb trap ionization, Hill-Adachi model of overlapping Coulomb potentials, Makram-Ebeid and Lannoo model of multiphonon isolated trap ionization, and Nasyrov-Gritsenko phonon-assisted tunneling between traps-were quantitatively analyzed. It was shown that the charge transport mechanism in La: HfO2 is qualitatively described by the Frenkel effect, but the Frenkel effect predicts an abnormally low trap concentration value and a large high-frequency dielectric constant value, which is not consistent with the experiment. The charge transport in La:HfO2 is quantitatively described by the model of phonon-assisted tunneling between neighboring traps.