Method for the determination of bulk and interface density of states in thin-film transistors

Abstract

In this article we present a method for the accurate determination of interface and bulk density of states (DOS) in thin-film transistors (TFTs), based on the combined analysis of transfer (ID–VGS) and capacitance–voltage characteristics. This analysis has achieved a number of results, eliminating sources of inaccuracies that are known to be present in other methods. A procedure for the determination of the electron and hole flatband conductances and bulk Fermi energy is demonstrated. A recursive procedure is employed to extract the bulk DOS directly from Poisson’s equation. The advantages of this method are the greater immunity to noise from the original data, the use of the complete Fermi function (no 0 K approximation), and the applicability to thin active layers. This method yields the interface state density spectrum as well as the bulk DOS. This information is very important for device design, process characterization, and modeling of TFTs.