Impact ionization in a graphene/SiO2/Si structure under high-field pulsed drive

Abstract

We have investigated the mechanisms of oxide breakdown in a graphene/SiO2/Si (GOS) capacitor structure under high-field pulsed voltage drive. Four different configurations are analyzed and compared in terms of bias polarity and substrate conductivity type: inversion or accumulation bias on a GOS structure formed on n-Si or p-Si substrate. Electric field distributions in the GOS structure are analyzed under strong bias in the breakdown field regime, and the resulting quantum yield of electron impact ionization is calculated for SiO2 and Si regions. Oxide breakdown is found to occur more readily in inversion bias than in accumulation bias. In the case of n-Si GOS under inversion bias, a cascade of impact ionization occurs, first in SiO2 and then into Si, resulting in explosive melting of Si in the depletion region. In the p-Si GOS case, impact ionization occurs mostly in SiO2 and near SiO2/Si interface. In both cases, strong atomic emission is observed, indicating explosive fragmentation/atomization of SiO2 and Si into atoms/ions in excited states.