Ambipolarity suppression in SiGe/Si- TFET using hetero-dielectric BOX engineering

Abstract

In this paper, an n-channel single gate SiGe/Si tunnel field effect transistor with hetero-dielectric buried oxide region (HD-BOX) is presented to reduce ambipolar current $(\mathbf{I}_{\mathbf{amb}})$. The presence of a lower bandgap SiGe as the source region increases On current. On the other hand, the Off current remains unchanged with larger bandgap Silicon in the channel region. The parasitic Iamb is suppressed further with the introduction of SiO2-HfO2 buried oxide layer. This provides a higher $\mathbf{I}_{\mathbf{on}}/\mathbf{I}_{\mathbf{amb}}$ current ratio as compared to TFET. The reduction of $\mathbf{I}_{\mathbf{amb}}$ is because of higher tunneling width near the channel/ drain interface, that is explained in terms of energy band diagram. The device exhibits Iamb of $5.44\times 10^{-12}\mathbf{A}/\mu \mathbf{m}$ at VGS=−1.0 V with a higher current ratio. The effect of misalignment in the position of the SiO2-HfO2 interface upon the drain current performance is also examined. The simulation process has been achieved using ATLAS 2D device simulator.