Cylindrical electron-hole bilayer TFET with a single surrounding gate and induced quantum confinement

In this paper, for the first time, an electron-hole bilayer TFET based on a cylindrical architecture with a single surrounding gate is proposed. The main regions of the device are composed of germanium, and the gate and a core p(+) Si region are employed to induce the required n-type and p-type layers in an intrinsic Ge channel. Furthermore, two lightly doped source/drain extension regions are embedded to block the direct tunneling between source and drain regions and the channel. Ultra-thin channel along with the gate/core-induced band bending form separate two-dimensional gases of electrons and holes in the channel. Hence, although there is an energy overlap between the conduction band and valence band of the channel even for zero gate bias, no band to band tunneling occurs. The on-set in the proposed TFET is happened when the first subbands of electrons and holes overlap each other. Our TFET exhibits the minimum subthreshold swing of 1 mV/dec, average subthreshold swing of 18.84 mV/dec, sub-60 mV/dec point subthreshold swing over seven decades of drain current, and the I-on/I-off ratio of 6.58 x 10(9). Moreover, owing to the vertical structure, the device provides higher scalability. The performance evaluation for different device parameters is carried out by using numerical simulations.