Silicon nitride with silicon nanocrystals formed by low-energy silicon plasma immersion ion implantation has been investigated as a charge trapping layer of a polycrystalline silicon-oxide-nitride-oxide-silicon-type nonvolatile memory device. Compared with the control sample without silicon nanocrystals, silicon nitride with silicon nanocrystals provides excellent memory characteristics, such as larger width of capacitance-voltage hysteresis, higher program∕erase speed, and lower charge loss rate at elevated temperature. These improved memory characteristics are derived by incorporation of silicon nanocrystals into the charge trapping layer as additional accessible charge traps with a deeper effective trap energy level.

We have investigated the temperature-dependent currentvoltage (IV) characteristics of Ti Schottky structure on the Si-on-insulator (SOI) in the temperature range of 175375 K by steps of 25 K. As decreasing temperature, the barrier height and ideality factor of Ti/SOI Schottky contact were found to be decreased and increased, respectively, indicating a considerable deviation from the ideal thermionic emission model in its current conduction mechanism. From the linear relationship between the barrier heights and ideality factors, the homogeneous barrier height was calculated to be 0.76 eV. The mean barrier height of 0.87 eV and the modified Richardson constant value of 30.63 A·cm ¹2 ·K ¹2 were obtained using modified Richardson plot. On the basis of a thermionic emission mechanism with a Gaussian distribution of the barrier heights, the temperature-dependent IV behavior of Ti/SOI Schottky contact was explained in terms of barrier height inhomogeneities at the interface between Ti and SOI.

Size-dependent charge storage was observed in metal–insulator–semiconductor structures containing amorphous Si quantum dots (a-Si QDs) grown by plasma-enhanced chemical vapor deposition. For a-Si QDs as large as 2 nm in diameter, one electron or one hole was stored in each a-Si QD. For small-sized a-Si QDs of 1.4 nm in diameter, however, the width of capacitance–voltage hysteresis was decreased, indicating that the charge density in the a-Si QDs was reduced. This can be attributed to the lowered tunneling barrier in the small-sized a-Si QDs resulting from a large quantum confinement effect. Long-term charge storage was observed in the fully charged a-Si QDs; this is attributed to a suppression of the discharge process by electrostatic repulsion among the charged dots.

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