(color online) Schematic structures of (a) conventional single-material-gate (SMG) line TFET (LTFET) and (b) proposed heteromaterial-gate (HMG) LTFET based on a Si/Ge heterojunction. The channel of the HMG LTFET consists of three parts: the pocket region above the source and the two gap regions connecting the pocket and drain regions. The pocket gate and gap gate are named M1 and M2. The green dashed box shows the equivalent lateral n-type junctionless transistor (JLT) gated by M2.