Berlin 2008 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 12: Dielectric and ferroelectric thin films and nanostructures II

DF 12.4: Vortrag

Donnerstag, 28. Februar 2008, 11:20–11:40, EB 107

The influence of image potential on defect assisted leakage mechanisms — •Grzegorz Kozlowski and Jarek Dabrowski — IHP, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany

We present the results of numerical simulation of tunneling current through a dielectric film. A carrier inside a dielectric film between metallic plates encounters an additional potential resulting from the interaction with its electrical image in the metal. As a result not only the height of barrier is lowered and the bands are bent downwards in vicinity of the metal electrodes, but also the tunneling length is shortened. Besides causing the well-known Schottky effect, this increases the tunneling leakage. Maybe more interestingly, also leakage due to the presence of defects is affected. This is because carriers must be supplied from the electrode to the defect states. Without the image force, in many cases this supply process limits the current that may flow through defects. This limitation may be partially or completely lifted when the image force is taken into account. The image potential lowers both the energy of defect states in vicinity of the electrode and the energy barrier separating these defects from the electrode. We investigate the influence of this effect on the magnitude of leakage current for various leakage mechanisms including trap assisted tunneling and Poole-Frenkel conduction.