Influence of image and exchange-correlation effects on electron transport in nanoscale DG MOSFETs

The impact of image and many-body exchange-correlation effects on electron transport has been investigated for nanoscale double-gate MOSFETs, using the nonequilibrium Green function method. The simulations have been performed for metal gate and polysilicon gate MOSFETs. When the gate material is metal, the inclusion of image and exchange-correlation effects increases the computed drain current, particularly at high gate voltages. In the case of polysilicon gate, the computed drain current remains almost unchanged at high gate voltages because both effects cancel out. However, at low gate voltages, the drain current is decreased by including these effects. In this study, the wavefunction penetration into the gate oxide and gate electrode has also been taken into account. Clear discrepancies between the drain currents calculated with and without considering the penetration effect can be found at low gate voltages. Further, the electron occupancy of each valley type is markedly changed by including this effect.