The Performance of Zr-Doped Al-Zn-Sn-O Thin Film Transistor Prepared by Co-Sputtering

In this work, a thin film transistor (TFT) with Zr-doped aluminum-zinc-tin oxide (Zr-AZTO) semiconductor as active layer was investigated. The Zr-AZTO thin films were co-sputtered by ZrO2 and AZTO targets (RF-Sputter) in Ar, and annealed at 350 °C in air atmosphere. With the discharge power of AZTO increasing from 100 W to 120 W, the content of Zr element decreases from 0.63 ± 0.01 at.% to 0.34 ± 0.01 at.%, and the oxygen vacancy decreases from (19.0 ± 0.1)% to (17.3 ± 0.8)%. The results of Zr-AZTO thin film show that the main factor is the co-sputter power of ZrO2 target. With the co-sputter power of ZrO2 increasing from 15 W to 45 W, the content of Zr element increases from 0.63 ± 0.01 at.% to 2.79 ± 0.01 at.%, the content of oxygen vacancy decreases from (19.0 ± 0.1)% to (14.1 ± 0.1)%, Eg increases from 2.76 eV to 2.86 eV, and the root mean square (RMS) roughness firstly decreases from 0.402 nm to 0.387 nm and then increases to 0.490 nm. The Micro Wave Photo Conductivity Decay (μ-PCD, LTA-1620SP) was used to measure the quality of Zr-AZTO thin film and the mean peak and D value decreases from 139.3 mV to 80.9 mV and from 1.54 to 0.77 as the co-sputter power of ZrO2 increases from 15 W to 45 W, which means it has highest localized states and defects in high ZrO2 co-sputter power. The devices prepared at 15 W (ZrO2)/100 W (AZTO) co-sputter show a best performance, with a μsat of 8.0 ± 0.6 cm2/(V∙S), an Ion/Ioff of (2.01 ± 0.34) × 106, and a SS of 0.18 ± 0.03 V/dec. The device of Sample B has a 0.5 V negative shift under −20 V NBS and 9.6 V positive shift under 20 V PBS.