Enhanced Electrical Performance and Low Frequency Noise of In2O3 Thin-Film Transistors Using Al2O3/CeGdOx Bilayer Gate Dielectrics

This work reports gadolinium-doped cerium oxide (CeO
₂
) as gate dielectric, and appropriate doping of Gd can effectively prevent oxygen vacancy-related defects in CeO
₂
thin films. Atomic layer deposition (ALD)-derived 3 nm Al
₂
O
₃
passivation layer on CeGdO
_x
has the advantage of further reducing the leakage current of CeGdO
_x
MOS capacitors due to the wide bandgap and compactness of Al
₂
O
₃
. Then, Al
₂
O
₃
/CeGdO
_x
bilayer dielectric-based In
₂
O
₃
thin-film transistors (TFTs) are constructed; electrical performances are systematically explored under the effect of Gd doping compared with pristine Al
₂
O
₃
/CeO
₂
-gated TFT. Al
₂
O
₃
/CeGdO
_x
(30 at% Gd) TFT demonstrates high performances with
${I}_{\text {ON}}/{I}_{\text {OFF}}$
ratio of 1.45
$\times 10^{{7}}$
, saturation mobility of 27.28 cm
²
/V
$\cdot $
s, subthreshold swing (SS) of 0.091 V/decade, interfacial trap states of
$1.64\times 10^{{11}}$
cm
⁻²
, as well as remarkable positive bias stress (PBS) stability. Low-frequency noise (LFN) together with X-ray photoelectron spectroscopy (XPS) illustrates that Gd doping in CeO
₂
contributes to the reduction of interface trap density, improving electrical performance. Moreover, a resistor-loading inverter based on Al
₂
O
₃
/CeGdO
_x
-gated TFT exhibits superior voltage transfer characteristics (VTC) with a voltage gain of 16 at 5 V, demonstrating the potential application of Al
₂
O
₃
/CeGdO
_x
-based TFTs for future digital circuits.