Analysis of Nitrogen‐Doping Effect on Sub‐Gap Density of States in a‐IGZO TFTs by TCAD Simulation

Abstract

In this work, the impact of nitrogen doping (N‐doping) on the distribution of sub‐gap states in amorphous InGaZnO (a‐IGZO) thin‐film transistors (TFTs) is qualitatively analyzed by technology computer‐aided design (TCAD) simulation. According to the experimental characteris-tics, the numerical simulation results reveal that the interface trap states, bulk tail states, and deep-level sub‐gap defect states originating from oxygen‐vacancy‐ (Vo) related defects can be suppressed by an appropriate amount of N dopant. Correspondingly, the electrical properties and reliability of the a‐IGZO TFTs are dramatically enhanced. In contrast, it is observed that the interfacial and deep-level sub‐gap defects are increased when the a‐IGZO TFT is doped with excess nitrogen, which results in the degeneration of the device’s performance and reliability. Moreover, it is found that tail‐distributed acceptor‐like N‐related defects have been induced by excess N‐doping, which is supported by the additional subthreshold slope degradation in the a‐IGZO TFT.