Proposal and demonstration of oxide-semiconductor/(Si, SiGe, Ge) bilayer tunneling field effect transistor with type-II energy band alignment

A novel bilayer tunneling field effect transistor (TFET) employing an attractive material combination of oxide-semiconductors and group-IV-semiconductors with type-II energy band alignment is proposed and the potential as a steep-slope device is systematically studied by TCAD simulation. Furthermore, the TFET operation by using n-ZnO/p-Si and n-ZnO/p-Ge tunneling junctions combined with n-ZnO junction-less channels has been experimentally demonstrated, for the first time. The careful choice of doping concentration and gate stack engineering have realized record-high ON/OFF current ratio of ~10⁸ among TFETs reported so far and minimum S.S. of ~71 mV/dec.