Quantum Transport in AlGaSb/InAs TFETs With Gate Field In-Line With Tunneling Direction

Quantum transport simulations are performed in tunneling FETs (TFETs) with the gate electric field in-line with the tunneling junction direction (in-line TFETs). Charge self-consistency and thermalization effects are included in a semiclassical Poisson solution to compute the electrostatic potential. The obtained potential is then used for current calculation with the ballistic nonequilibrium Green´s function method (NEGF) in the tight binding basis. It is shown that the NEGF method predicts a higher subthreshold swing than the often-used dynamic nonlocal (DNL) path band-to-band method. The NEGF method accounts for the direct source-drain tunneling, which is underestimated in the DNL path approach in the studied geometries. Undercut is shown to be essential to obtain switching slope below 60 mV/decade in the in-line TFETs.