Quasi-Fermi-Level Phase Space and its Applications in Ambipolar Two-Dimensional Field-Effect Transistors

Abstract

Quasi-Fermi levels (QFLs) have become a canonical concept in semiconductor device modeling. However, a global model to cover both unipolar and ambipolar transport modes of two-dimensional field-effect transistors (2D FETs) based on QFLs is still needed, as it is challenging to capture quantitatively the effect of QFL splitting on transport. This work establishes a theoretical platform to account for that effect: the quasi-Fermi-level phase space (QFLPS). With QFLPS a unified picture of unipolar and ambipolar transport is drawn, the working modes of 2D FETs acquire more intuitive physical interpretations, and many valuable outcomes for device modeling and circuit design are realized.