A High-Performance InAs/GaSb Core-Shell Nanowire Line-Tunneling TFET: An Atomistic Mode-Space NEGF Study

Using a tight-binding mode-space NEGF technique, we explore the essential physics, design and performance potential of the III-V core-shell (CS) nanowire (NW) heterojunction tunneling field-effect transistor (TFET). The CS TFET “line-tunneling” current increases significantly with the core diameter ${d} _{C}$ and outperforms the best III-V axial “point-tunneling” NW heterojunction TFET ${I} _{\mathrm{ ON}}$ by up to $6\times $ for $d_{C} = 6.6$ nm. Reaching such a high level of current at low supply voltage, however, requires and involves specific and sometime unanticipated optimizations and physics that are thoroughly investigated here. In spite of the commonly accepted view, we also show and explain the weak gate-length dependency observed for the line-tunneling current in a III-V TFET. We further investigate the effect of electron-phonon scattering and discrete dopant impurity band tails on optimized CS NW TFETs. Including those non-idealities, the CS-TFET inverter performance significantly outperforms that of the axial TFETs. The low-power (LP) $V_{\mathrm{ DD}} = 0.35\text{V}$ CS-inverter delay is comparable to that of the high-performance (HP) Si CMOS using $V_{\mathrm{ DD}} = 0.55\text{V}$ , which shows promise for an LP TFET technology with HP speed.