GaSb-InAs n-TFET With Doped Source Underlap Exhibiting Low Subthreshold Swing at Sub-10-nm Gate-Lengths

In this letter, a sub-10-nm n-type GaSb-InAs heterojuction tunnel field-effect transistor (Het-j TFET), having n⁺-doped underlap layer of InAs between source and channel is proposed, which exhibits low subthreshold swing (SS) over a large range of currents. The proposed device is compared with conventional p-i-n GaSb-InAs Het-j TFET having the same physical gate length of 9 nm. Using ballistic tight binding-based Non-Equilibrium Green´s Function (NEGF)-Poisson quantum simulations, we present I_D - V_GS curves and band diagrams for both the devices and provide analytical justification for the observed improvement in the SS. We also study the variations in device characteristics due to the length and doping of the underlap layer in the proposed device. It is observed that an underlap length of 6 nm is optimal to achieve a low SS in the proposed device.