Two-dimensional quantum mechanical modeling of band-to-band tunneling in indirect semiconductors

A quantum mechanical procedure to calculate phonon-assisted tunneling current in indirect semiconductors in a two-dimensional structure is demonstrated. Applying the procedure to two types of double-gate silicon tunnel field-effect transistor (TFET) structures, it is observed that semiclassical predictions strongly overestimate the subthreshold swing and the device current. Furthermore, while the semiclassical simulation suggests a higher current for one of the investigated TFET devices, a proper quantum mechanical calculation comes to the opposite conclusion. This result, which is expected to apply to direct semiconductors as well, proves the importance of correct quantum mechanical tunneling models for performance predictions of novel devices such as TFETs.