Extraction of Trap Densities in Amorphous In-Ga-Zn-O Thin-Film Transistors by Using Efficient Surface Potential Calculations

A novel extraction method for trap densities in amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) is developed. In this method, a new calculation procedure for efficiently determining surface potentials (SPs) in the a-IGZO layer is used with low-frequency capacitance- voltage (C-V) measurements. To enhance the computational efficiency of the extraction method, we propose an approximate expression relating the front-side and back-side SPs, so that it is possible to determine SPs without conventionally required calculation steps, such as either meshing the a-IGZO layer or calculating the potential profiles for the entire layer. The extraction method is tested by using low-frequency C-V curves of a self-aligned a-IGZO TFT to minimize the influence of parasitic capacitances and resistances. This method is expected to facilitate the extraction of trap densities, and contribute to characterization and modeling of a-IGZO TFTs.