Defect Engineering for High Performance and Extremely Reliable a‐IGZO Thin‐Film Transistor in QD‐OLED

Abstract An amorphous indium‐gallium‐zinc‐oxide (a‐IGZO) thin‐film transistor (TFT), which exhibits the best electrical stability (PBTS ≤ 0.009 V), is implemented to create quantum‐dot organic light‐emitting diode product. Electrical stability has been explained through various mechanisms involving defects related to oxygen and hydrogen. The defects of a‐IGZO are identified and the parameters of the deposition process are utilized to obtain V_o⁺ and V_Zn⁻ values of 1.7 × 10¹⁷ and 2.4 × 10¹⁸ spins cm⁻³, respectively, which are quantified using electron spin resonance for the first time. The defects of the gate insulator (GI) in the upper and lower parts of the a‐IGZO TFT and the oxygen and hydrogen inflow/diffusion generated during the process are also controlled. From well‐controlled a‐IGZO and GI, the defect density at the top‐channel interface and near‐interface of the a‐IGZO TFT is reduced by 85% and 70%, respectively. The defects in the bottom‐channel are also reduced by 83% and 75% for the interface and near‐interface, respectively. Electrical stability is secured by controlling V_o⁺ and V_Zn⁻ and reducing sub‐gap trap density among interface defects that are not directly observed until now. In this paper, it is reported that the best a‐IGZO TFT performance is achieved through defect engineering.