Charging behavior of MNOS and SONOS memory structures with embedded semiconductor nanocrystals - Computer simulation

Molnár, K. Z. and Turmezei, P. and Horváth, Zsolt József (2013) Charging behavior of MNOS and SONOS memory structures with embedded semiconductor nanocrystals - Computer simulation. In: XXI International Materials Research Congress, Symposium 6B. Low-Dimensional Semiconductor Structures, 1534 . Materials Research Society, Pittsburgh.

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Abstract

The effects of the oxide and nitride thicknesses and of the presence of semiconductor nanocrystals are studied on the charging behaviour of MNOS and SONOS non-volatile memory structures by the calculation of electron and hole tunnelling probability into the nanocrystals or to the nitride conduction or valence band, respectively, and by the simulation of memory hysteresis behaviour. The results are discussed in terms of the actual shape of potential barrier yielding different tunnelling current mechanisms. It is concluded for both MNOS and SONOS structures that the optimal tunnel oxide thickness for the charging behaviour is about 2 nm. Low nitride thickness decreases the efficiency of the injected charge due to its loss via the blocking layer, yielding narrower memory window. The presence of nanocrystals enhances the charge injection resulting in the better performance, but for the structures with thin tunnel oxide layer (below 3-4 nm) only, and if the nanocrystals are located close to the Si substrate at the oxide/nitride interface. The results of simulations are in agreement with the experimental results obtained in MNOS structures with Si or Ge nanocrystals.

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