Study of fully-depleted Ge double-gate n-type Tunneling Field-Effect Transistors for improvement in on-state current and sub-threshold swing

In this paper, a fully-depleted (FD) Ge double-gate (DG) n-type Tunneling Field-Effect Transistors (TFET) structure is studied in detail by two-dimensional numerical simulation. The simulation results indicated that the on-state current Ion and on-off ratio of the FD Ge DG-TFET increases about 1 order of magnitude comparing with the Conventional Ge DG-TFET, and Ion=3.95×10-5 A/μm and the below 60 mV/decade subthreshold swing S=26.4 mV/decade are achieved with the length of gate LD=20 nm, the workfuntion of metal gate Φm=0.2 eV and the doping concentration of n+-type-channel ND=1×1018 cm-3. Moreover, the impacts of Φm, ND and LD are investigated. The simulation results indicated that the off-state current Ioff includes the tunneling current at the middle of channel IB the gated-induced drain leakage (GIDL) current IGIDL. With optimized Φm and ND, Ioff is reduced about 2 orders of magnitude to 2.5×10-13 A/μm with LD increasing from 40 nm to 100 nm, and on-off ratio is increased to 1.58×107.