Exchange-correlation effects in ballistic and dissipative transport in GAA Si nanowire transistors

The impact of exchange and correlation (XC) in the current voltage characteristic of a gate-all-around Si nanowire transistor has been thoroughly investigated in the context of ballistic and dissipative transport. The electron transport is described using the Non Equilibrium Green Function formalism (NEGF). The XC potential is evaluated in the local density approximation. Transfer characteristics for devices with cross-section of 2.2×2.2 nm2 and 3.6×3.6 nm2 have been calculated. The calculation shows that the impact of the XC is larger for the small cross-section, producing an enhancement in the on current of close to 50%. This enhancement is gate bias dependent and has a maximum of a few hundred millivolts after the threshold voltage. The impact of the XC in the on current is comparable to the impact of scattering for the small cross-section but it is smaller at the larger cross section.