TANTALUM CAPACITOR AS A METAL – INSULATOR – SEMICONDUCTOR STRUCTURE

Physical model for tantalum capacitor is given based on metal-insulator–semiconductor (MIS) structure. Metal electrode consist from tantalum with work function 4.1 eV. Insulating layer Ta2O5 has band gap 4.5 eV and semiconductor MnO2 has energy band gap 0.26 eV for MnO2:β modification and 0.58-0.7 eV for MnO2:γ modification. Important role play the interfaces Ta- Ta2O5 and Ta2 O5- MnO2, but the second one play the dominant role for current transport. In normal mode Poole-Frenkel and Schottky emission is dominant. In reverse mode VA characteristic can be approximated also by exponential dependence with ideality factor about 10 and resistance of MnO2 can be estimated. For acceptor-like surface states on Ta2O5 and MnO2 interface strong tunnelling current takes place