Effects of Schottky Barrier in Low-k SiOC

抄録

This letter discusses the reason for the tunneling behavior of zinc based oxide semiconductor thin film transistors (TFTs). The device was fabricated using SiOC as a gate dielectric, which decreased polarities depending on the combinations of oxygen and carbon ions as opposite polar sites. The threshold voltage shifts in a zinc based oxide semiconductor are presented using the metal oxide semiconductor (MOS) structure analysis of Ohmic/Schottky and Poole-Frenkel (PF) contacts based on the drain-source current (I_DS) and drain-source voltage (V_DS) with change of gate voltage. The transfer characteristic of TFTs and stability were influenced by the polarities of the SiOC gate insulator. The threshold voltage shift effect was explained by a slow trapping of excess carriers in defects located at the SiOC interface. A stable TFT prepared on non-polar SiOC was achieved from PF contact due to the very high height of Schottky barrier. The I_DS-V_DS curve including the Ohmic contact at V_G=0V and Schottky barrier with increase of gate voltage exhibited a tunneling behavior induced by diffusion currents. However, for the TFTs on polar SiOC with the trap charge, it was observed the trapping phenomenon transited from the localized state to band through the low potential barrier SB. The excess charge carriers in a localized trap state caused the threshold voltage shifts.