Vibronic states of silicon-silicon dioxide interface traps

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Abstract
Ionic vibrational properties of trap systems present at the silicon-silicon dioxide interface are expected to influence measured data and their interpretation. Similar to the case of deep bulk impurities in semiconductors, these traps require a model, where the eigenenergies of the total defect system, including the captured electrons and the vibrating ion, is taken into account in optical investigations. For thermally governed processes, the same particle picture can be brought into a thermodynamical description, to make more detailed information on interface states possible. Differences between optical threshold energies and thermally obtained energy quantities, Gibbs free energies and enthalpies, together with thermally activated carrier capture and entropy changes during carrier transitions are expected when ionic relaxations are present at the interface. Experimental results, published in the literature, are examined in the light of this model. A number of data exist, which indicate that important parts of a detailed understanding of the silicon dioxide-silicon interface states are lost when treated as bare electronic systems.