Investigation of Crystal Size Impacts on the Tunneling Current in Germanium Nanocrystal Metal-Oxide-Semiconductor Transistors

The crystal size of nano-crystalline germanium dependence depends on the gate current in memory devices has been theoretically investigated when the mean diameter is uniquely controlled by the nominal thickness of the deposition of Ge layer. Because the band gap and dielectric constant of nano-crystalline germanium will be largely affected by crystal size in the regime of nano-scale, the calculated gate currents in nano-crystalline germanium strongly depends on the crystal size, especially on a few nanometers, when the equivalent oxide thickness memoirs the same. The numerical calculations demonstrate that dielectric constant of nano-crystalline germanium impacts on the Fowler-Nordheim tunneling current can be neglected when the oxide field is higher than 3 MV/cm. The results also demonstrate that the leakage current can be reduced by fabricating thinner nc-Ge layer in memory devices.