Effect of a Ru doped SnO$_{2-x}$ buffer layer on thin-film transistors based on SnO$_{2-x}$ channel layer

We report on studies of transparent thin-film transistor (TFT) devices based on SnO$_{2-x}$ thin film. SnO$_{2-x}$ thin films were prepared by pulsed layer deposition with and without Ru-doped SnO$_{2-x}$ buffer layer on r-plane sapphire substrates to investigate the effect of a Ru-doped SnO$_{2-x}$ buffer layer on the electrical properties of SnO$_{2-x}$ channel layer. The Ru-doped SnO$_{2-x}$ buffer layer was found to be very crystalline and insulating at the same time. Using such Ru-doped SnO$_{2-x}$ buffer layer made it possible for the SnO$_{2-x}$ channel layer to have both low carrier density and high mobility, probably due to reduction of the threading dislocation density. AlO$_{x}$ gate insulator layer was deposited by atomic layer deposition and ITO was used as the source, the drain, and the gate electrodes. We will compare the TFT performances with or without the Ru-doped SnO$_{2-x}$ buffer layer and discuss how such buffer layer enables the necessary device parameters for TFT.