Impact of Channel Thickness Variation on Bandstructure and Source-to-Drain Tunneling in Ultra-Thin Body III-V MOSFETs

In nanoscale MOSFETs with sub-10 nm channels, the source-to-drain tunneling is expected to be a critical bottleneck, especially in III-V devices on account of their extremely low effective masses. Also, to maintain electrostatic integrity at extremely small gate lengths, the channels need to be made ultrathin. In such devices, the bandstructure of the channel material becomes thickness dependent due to quantum confinement effects, and deviates remarkably from that of the bulk material. In this paper, we use first principle density functional theory calculations to evaluate the variation of the effective mass and bandgap with channel thickness. Then, we perform semi-classical ballistic and full quantum non-equilibrium Green's function transport simulations to study the impact on source-to-drain tunneling in III-V nMOSFETs. We demonstrate that the severity of the expected degradation due to source-to-drain leakage is reduced significantly, when the beneficial impacts of change in bandstructure, and multi-valley transport are taken into account.