Enhanced Stability in Zr-Doped ZnO TFTs With Minor Influence on Mobility by Atomic Layer Deposition

Abstract

We developed a novel method to fabricate Zr-doped ZnO (ZrZnO) thin films via low-temperature atomic layer deposition technique. ZrZnO films were deposited by diethylzinc (DEZ)/tetrakiszirconium (TDMAZr)/H2O cycles instead of the traditional DEZ/H2O/TDMAZr/H2O cycles and applied in thin-film transistors (TFTs). It is found that ZrZnO-TFTs with a Zn-Zr-O:ZnO atomic ratio of 1:49, i.e., ZrZnO (1:49) exhibit excellent properties, such as a minimum subthreshold swing value of 0.37 V/dec, a maximum ${I}_{ \mathrm{\scriptscriptstyle ON}}/{I}_{ \mathrm{\scriptscriptstyle OFF}}$ value of $2.4\times 10^{{7}}$ , a largermobility of 12.38 cm2/ $\text {V}\cdot \text {s}$ , and a smaller threshold voltage shift ( $\Delta {V}_{\text {th}}$ ) of 0.61 V under temperature stress from 25 °C to 105 °C, which are superior compared with TFTs with ZnO channel doped by ZrO2 layer. The stability of ZnO TFTs was improved greatly by Zr-Zn-O doping. Moreover, the field-effect mobility of ZrZnO-TFTs was rarely influenced. Temperature-stress test was carried out to build up the correlation model in terms of the defect structures, subgap states, and stability. These results could provide a newaccess to understand the device instability of ZrZnO TFTs.