High-Performance Ti-Doped Zinc Oxide TFTs With Double-Layer Gate Dielectric Fabricated at Low Temperature

In this study, titanium (Ti)-doped zinc oxide thin film transistors (TiZO TFTs) with a double-layer gate dielectric were successfully fabricated on glass at low temperature. A stacked 7 nm-thick Al
₂
O
₃
/180 nm-thick SiO
₂
dielectric layer was used to improve the electrical performance of the TFTs, especially their leakage characteristics. Compared with the SiO
₂
single dielectric, the devices with the double-layer Al
₂
O
₃
/SiO
₂
dielectric layer showed optimized electrical properties. The saturation mobility (μ
_sat
), threshold voltage (v
_th
), subthreshold swing (SS), and I
_on
/I
_off
ratio obtained were 127 cm
²
V
^-1
s
^-1
, 1.09 V, 131 mV/decade, and 3.7 × 10
⁸
, respectively. Furthermore, the thickness of Al
₂
O
₃
in the double-layer gate dielectric was found to have considerable influence on the performance of the TiZO TFTs.