Tight-Binding Nonequilibrium Green's Function Modeling of Tunnel Field-Effect Transistors

The pursuit of energy-efficient electronic devices has led to the exploration of novel transistor designs, including tunnel field-effect transistors (TFETs). In this master thesis, we embark on a comprehensive study of InAsGaSb TFETs, employing the nonequilibrium Green's function (NEGF) formalism, with a tight-binding (TB) model for band structure. The primary objective is to perform comparative appraisals of the TFET transcharacteristics evaluated with the TB-NEGF model developed in this thesis, versus models based on the Wentzel-Kramers-Brillouin (WKB) approximation coupled with k·p models, and with test cases from the literature. To this aim, we initially developed a robust computational code, based on the TB-NEGF formalism, to simulate the electronic behavior of InAsGaSb TFETs. The code's architecture and theoretical foundations are meticulously explained to provide a comprehensive understanding of its inner operation. With the code in place, our study's main focus shifted towards the comparison of the TFET transcharacteristics with the literature. This endeavor demanded precise calibrations of critical parameters, including the mesh density of energies in both the longitudinal and transversal directions, as well as the spatial mesh density. The optimization of these parameters aimed to find the best trade-off between simulation accuracy and computational time. In this view, efforts are invested in further code optimization and improvements of the algorithm. The results of this research indicate that our developed code successfully replicates the transcharacteristics for all the devices under test, with a high degree of accuracy.