A Low-Leakage Zinc Oxide Transistor by Atomic Layer Deposition

In this work, we report an atomic layer deposited (ALD) zinc oxide (ZnO) transistor with low off-state leakage current ( $\text{I}_{ \mathrm{\scriptscriptstyle OFF}}$ ) ~ ${3} \times {10}^{-{18}}$ A/ $\mu \text{m}$ at high temperatures up to 147 °C, measured by devices with interdigitated electrodes with a wide channel width ( $\text{W}_{\text {ch}}{)}$ of $10000~\mu \text{m}$ , where the low $\text{I}_{ \mathrm{\scriptscriptstyle OFF}}$ is still under the detection limit. The impact of ALD growth temperature and annealing on the electrical performance is systematically studied. It is found that low temperature deposition and post deposition annealing are effective to enhance the performance of the ALD ZnO transistors. $\mu _{\text {FE}}$ as high as 32.8 cm2/ $\text{V}\cdot \text{s}$ , on/off ratio ~ $10^{{12}}$ and subthreshold slope (SS) down to 75.3 mV/dec at room temperature are achieved. These results suggest ALD ZnO is a promising channel material for low off-state leakage current device applications.