Reducing Ambipolar Current in Germanene Nanoribbon Tunneling Field Effect Transistor (GeNR-TFET) using Gate-Drain Overlap and Decreasing Doping Density in the Drain Side

In this research, we investigate the ambipolar current in germanene nanoribbon tunneling field effect transistor (GeNR-TFET) using combination of density functional theory (DFT) and non-equilibrium Green’s function method (NEGF). We propose two different methods to reduce the ambipolar current in the GeNR-TFET: using overlapped gate metal to cover part of the drain side and the other idea is to decrease the doping density in the drain side. The results show that by extension of the metal gate on the drain region, the hole current from the drain to channel reduces and it is possible to reduce this current more by using longer overlapping length. Also, results prove that by decreasing the doping density in the drain side compared with the source region, the ambipolar current declines. We obtain that by mixing two proposed ways, the ambipolar current can significantly be reduced. Suppression of this ambipolar current is an important challenge in digital circuit design.