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

Abstract

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.

Ge nanocrystals in alumina matrix: A structural study

“…Ge has a smaller band-gap than Si which makes it compatible with currently used metal oxide semiconductor (MOS) technology and also improves its write/erase speed [5,6]. Promising non-volatile properties of Ge-NCs were reported by several groups [7][8][9][10].…”

Two-dimensional arrays of ordered, highly dense and ultra-small Ge nanocrystals on thin SiO2layers

“…This produces two phenomena: a faster charging process in Ge islands and a larger potential barrier for carrier leakage to the substrate, resulting in a larger retention time [3][4][5][6][7]. Recent theoretical studies have demonstrated the better retention properties of Ge NC memories, compared with those based on Si NCs and an ideal size for Ge islands of ~15 nm [8].…”

Synthesis and memory effect study of Ge nanocrystals embedded in LaAlO3 high-k dielectrics

“…However, research results in several groups have demonstrated the superior properties of Ge-based nanocrystal memories over those based on Si. [4][5][6] The Ge nanocrystals offer improved nonvolatile charge retention time due to their smaller band gap. The smaller band gap provides both a higher confinement barrier for the retention mode and a smaller barrier for the program and erase modes.…”