Field-Effect Mobility Extraction of Solution-Processed InGaZnO Thin-Film Transistors Considering Dielectric Dispersion Behavior of AlO<sub><i>x</i></sub> Gate Insulator
Seon‐Beom Ji, Narkhyeon Seong, Jongjang Park, Hwarim Im, Yong‐Sang Kim, Yongtaek Hong
Abstract
We investigated the effect of the dielectric dispersion behavior of solution-processed aluminum oxide (AlO x ) on the field-effect mobility estimation of the solution-processed indium–gallium–zinc oxide (IGZO) thin-film transistors (TFTs). In the metal–insulator–metal (MIM) structure, solution-processed AlO x dielectric film annealed at 350 °C showed dielectric dispersion behavior, which was attributed to the electric double layer (EDL) due to the mobile ions, such as a hydrogen ion (H + ) or a hydroxyl group (OH – ). The annealing process at a higher temperature of 500 °C reduced the number of mobile ions in the AlO x film and removed the dielectric dispersion behavior in the MIM structure. However, solution-processed IGZO TFTs using the AlO x annealed at 500 °C as gate insulator showed dielectric dispersion-related behavior. We found that the chemical reaction to form a solution-processed IGZO layer supplied the mobile ions to the AlO x film, resulting in the EDL and dielectric dispersion phenomenon. Therefore, the dielectric dispersion should be investigated in the metal–insulator–semiconductor–metal structure, although the dispersive behavior does not occur in the MIM structure. Furthermore, the field-effect mobility (μ FE ) of solution-processed IGZO TFTs was 35.6 and 17.5 cm 2 /V·s with and without consideration of the dielectric dispersion behavior. The μ FE was overestimated by 203% without regard to the dielectric dispersion. Consequently, the dielectric dispersion should be considered to estimate the accurate μ FE of solution-processed IGZO TFTs with solution-processed AlO x as the gate insulator layer.