Photoresponses Improvement of ZnO Thin Film Transistor by Using a HfO2-Al2O3 Double Dielectrics

In this work, we have fabricated two bottom-gate zinc oxide thin film transistors (TFTs) with single-layer HfO2 and double-layer HfO2-Al2O3 dielectrics by atomic layer deposition (ALD). The TFT with HfO2-Al2O3 dielectric exhibited better electrical characteristics, such as a higher field effect mobility of 6.1 cm²/V•s and a lower subthreshold swing of 0.124 V/decade. At the same time, the optical properties is also improved significantly with larger responsivity (6.05 A/W) and UV-to-visible rejection ratio (6.05×10⁴). These results are attributed to lower interface trap states between channel layer and dielectric layer by an Al2O3 interlayer.