Electrical study of Ge-nanocrystal-based metal-oxide-semiconductor structures for p-type nonvolatile memory applications

Nonvolatile memory structures using Ge nanocrystals embedded in SiO2 have been characterized by room and low temperature current-voltage and capacitance-voltage measurements. The Ge nanocrystals have been fabricated by low pressure chemical vapor deposition process which is shown to be well suited for a real control of the tunnel oxide thickness. The deposition conditions allow a separate control of nc-Ge density and size. Using capacitance-voltage characterizations on nonvolatile memory structures, we have measured the charging and discharging kinetics of holes for tunnel oxides in the range 1.2-2.5 nm. Using current-voltage measurements and simulations, we have also shown that nc-Ge are at the origin of a tunnel-assisted current. Simulations have demonstrated that the hole's charging effects strongly reduce the current density across the nonvolatile memory structure. Combined with a good control of nc-Ge properties, the use of Ge dots with large diameters (>10 nm) seems to be a promising way for p-type memory applications. (C) 2004 American Institute of Physics.