Performance Boost of Si TFETs by Insertion of III-V Dipole Formation Layer: A First Principle Study

Abstract

Silicon channel tunnel field-effect transistors (TFETs) are known to exhibit low ON-state current due to the wide indirect band gap. In this work, to achieve high ON-state current, we propose a Si TFET with an ultra-thin dipole formation layer (DFL) inserted at the source/channel junction. The inserted DFL forms charge transfer dipoles at the interface, resulting in a staggered band gap. As the consequence, the effective tunnel barrier for electrons is significantly lowered so that ON-state current increases by orders of magnitude. To analyze the characteristics of DFL-inserted Si TFETs, we have solved nonequilibrium Green's function (NEGF) and Poisson's equation using density functional theory (DFT) Hamiltonians. We demonstrate that DFL-inserted Si TFETs show boosted performance over conventional TFETs, exhibiting high ON-state current and steep subthreshold swing (SS).