Charging behaviour of MNOS structures with embedded Ge nanocrystals

Charging behaviour of MNOS structures containing Ge nanocrytals embedded at the SiO ₂/Si ₃N ₄ interface are studied by experiments and by calculating tunnelling probabilities of electrons and holes to the conductance or valence band of the nitride layer, respectively, for structures with and without nanocrystals. It is concluded that the optimal charging behaviour of MNOS structures without nanocrystals can be expected for an oxide thickness of 2-3 nm. The presence of semiconductor nanocrystals at the SiO ₂/Si ₃N ₄ interface enhances strongly the tunnelling probability of electrons and holes for structures with thin oxide layers (2-3 nm) at low electric fields, but they do not influence the charging behaviour of structures at high electric fields. The results of calculations are in agreement with the experimental results obtained on MNOS structures with Ge nanocrystals.