Nenad Novkovski, Albena Paskaleva, Elena Atanassova


Flatband and current-voltage instabilities in unstressed Al/Ta2O5-SiO2/Si structures were studied in details. It has been found that, after an initial run left on fresh samples, both C-V and J-V characteristics exhibit repeatable patterns. Precisely repeatable counterclockwise hysteresis-like loop in C-V characteristics occurs, while no significant hysteretic behaviour is observed in static J-V characteristics. The reduced instability in J-V characteristics is explained by mutual compensation of two opposite effects owing to the presence of trapped positive charges on slow traps in the interfacial SiO2-like layer: (i) flatband voltage shift and (ii) lowering of Fowler-Nordheim tunnelling barrier for holes injected from the Si substrate. Correct determination of equivalent oxide thickness and fast interface state densities requires using the C-V curves obtained during the runs right, because progressive trapping on slow states occurs during the runs left. Value of the oxide charge is to be determined using the value of the flatband voltage obtained from the run left (after an initial run right), since it corresponds to the state of empty slow traps.


C-V hystersis; nanosized dielectric films; interface silicon/silicon dioxide

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DOI: http://dx.doi.org/10.20903/csnmbs.masa.2013.34.1-2.38


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