A transient electrical model of charging for Ge nanocrystal containing gate oxides


A transient electrical model of charging for Ge nanocrystal containing gate oxides

Beyer, V.; von Borany, J.; Klimenkov, M.

The write performance of a multidot memory is investigated in MOS (metal-oxide-semiconductor) capacitors. The oxide of the MOS structure on p-type Si contains a layer of ion beam synthesized Ge nanocrystals (NC's) very close to the Si/SiO2 interface. This structure is modeled in a floating gate-like approach, where the NC's are considered as individual storage nodes and charged by direct tunneling of holes. Quantum confinement and Coulomb blockade effects of small Ge NC's (1-6 nm) are discussed and found to be negligible for the present structure. A close agreement between the calculated write characteristics and experimental data clearly confirms the validity of the model. From the simulation results it is predicted that a flatband voltage shift ΔVfb = -1V could be gathered with programming times tprog < 1µs. The write parameters (pulse voltage and duration) for a given ΔVfb value are mainly determined by the distance of the NCs' to the substrate.

Keywords: nanocrystals; MOS; Ge; memory; quantum confinement; Coulomb blockade

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Publ.-Id: 7476