Investigation of In_xGa_{1-x}As Ultra-Thin-Body Tunneling FETs Using a Full-Band and Atomistic Approach

Using a 2-D, full-band, atomistic, quantum mechanical simulator based on the sp³ d⁵ s^* tight-binding method with spin-orbit coupling, we investigate the performances of single- and double-gate relaxed In_xGa_1-xAs p-i-n ultra-thin-body (UTB) tunneling field-effect transistors (TFETs) with 20 nm to 50 nm gate lengths. The ON-current, OFF-current leakage, and subthreshold slope (SS) properties are analyzed as function of the In concentration in 5 nm thick structures. We find (i) that devices with a high In concentration allow more ON-current, but suffer from higher OFF-currents and lower SS, (ii) that double-gate devices perform better than single-gate ones, and (iii) that a longer gate length reduces the source-to-drain tunneling leakage and the OFF-current of the UTB TFETs.