Effects of Oxygen Content on Output Characteristics of IGZO TFTs under High Current Driving Conditions

Abstract

We study the effects of oxygen content in indium-gallium-zinc oxide (IGZO) thin films on the output characteristics of IGZO thin-film transistors (TFTs) under high current driving conditions. Output curves were characterized at a high gate-to-source voltage (= 40 V) from both oxygen-rich and oxygen-poor IGZO TFTs. Characterization results showed that the drain current (ID) decreased with an increase in the drain-to-source voltage (VDS) under high-VDS conditions in the oxygen-rich IGZO TFTs, but abruptly increased with VDS in the oxygen-poor IGZO TFTs. From the detailed analysis of the transfer and capacitance-voltage curves obtained after output curve characterization by varying the VDS sweep range, the abnormal behavior of the output curves was mainly attributed to the increased number of trapped electrons within the gate dielectric and that of the doubly ionized oxygen vacancies in IGZO during the output curve characterization at high VDSs in oxygen-rich and oxygen-poor IGZO TFTs, respectively. The abnormality of the output curve was more significant in a wider channel device in both TFTs, which was attributed to the increased device temperature due to the self-heating effects.