Ge- and Ge1-zSnz-Based Gate-Underlap Dual Material Double Gate Tunnel Field Effect Transistor: Modeling, Optimization, and its Application to Biosensors

Herein, an n-channel dual material double gate tunnel field effect transistor (DMDG-TFET) with a gate-drain underlap using Ge and Ge1-zSnz is proposed. An analytical model has been developed to optimize the length of the underlap region for Ge and Ge-Sn alloy as the channel material. The ambipolarity shown by TFET has been utilized to perform a label-free biosensing in response to the change of permittivity of the biomaterials used in the gate-drain underlap region. The use of Ge-Sn alloy as a channel material results in a lower ambipolar current but higher sensitivity to the presence of biomolecules. DMDG with workfunction (4 and 4.4 eV) is used to optimize the device performance. The analytical results have been validated by the results obtained using commercial software (Silvaco TCAD). A high sensitivity of the biosensor device is obtained by utilizing the tunnel FET ambipolar current with optimized gate underlap of L-UD = 55 nm (for Ge) and L-UD = 38 nm (for Ge-Sn alloy).