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 HfO
₂
and double-layer HfO
₂
-Al
₂
O
₃
dielectrics by atomic layer deposition (ALD). The TFT with HfO
₂
-Al
₂
O
₃
dielectric exhibited better electrical characteristics, such as a higher field effect mobility of 6.1 cm
²
/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 (6.05×10
⁴
). These results are attributed to lower interface trap states between channel layer and dielectric layer by an Al
₂
O
₃
interlayer.