A Silicon Tunnel Field-Effect Transistor with an In Situ Doped Single Crystalline Ge Source for Achieving Sub-60 mV/decade Subthreshold Swing

We report the demonstration of an n-channel lateral Si tunnel field-effect transistor (TFET) with a single crystalline Ge source fabricated using the gate-last process. The p Ge source was in situ doped and grown at 320°C. An abrupt interface between Ge source and Si channel with type-II band alignment and a steep source doping profile (～1.5 nm/decade) formed the tunneling junction. This allows the realization of a TFET with a steep subthreshold swing of 49 mV/decade at room temperature and an I_ON/I_OFF ratio of 10⁷.