Three-dimensional quantum simulation of silicon nanowires

Silicon nanowires are perspective core components of future integrated circuits. The feasibility of Si nanowire FETs has been demonstrated by several groups, e.g. by Cui et al. TCAD-oriented simulation tools can accompany the sophisticated fabrication process, providing aid for performance improvement, supporting the basic understanding, and facilitating the development of new structures. Nanowire FETs with small cross sections and ultra-short gates call for a three-dimensional (3D) quantum mechanical treatment of carrier transport beyond the effective mass approximation (EMA). As long as inelastic scattering is neglected, a wave function approach is the method of choice due to its numerical advantage over the non-equilibrium Green´s function (NEGF) technique. However, the computational burden does not allow to treat important effects like phonon scattering and gate tunneling on a full-band (FB) level. These phenomena still require the EMA. In this paper, we describe a FB quantum transport simulator and show FB and EMA simulation results for quantum-ballistic currents in Si nanowire FETs. We focus on the effects of channel orientation, surface roughness, and direct gate tunneling leakage.