Ultrafast (50 ns) ID–VG Analysis on Oxide Thin-Film Transistors With Morphotropic Phase Boundary State High-κ Gate Insulator

The advancement of oxide thin-film transistors (TFTs) with high-performance is crucial for high-resolution, high-framerate displays as they serve as switching and driving elements. To ensure high mobility characteristics and withstand relatively high supply voltage (5 V), a TFT panel must have a high-
$\kappa $
gate dielectric (DE) with comparatively thick thickness and good interfacial quality. Maintaining a high-
$\kappa $
gate insulator in a moderately thick regime and preventing charge-trapping from deteriorating electrical properties are still difficult tasks. In this study, we employed an oxide TFT with a morphotropic phase boundary (MPB) Hf-Zr-O (HZO) film as a high-
$\kappa $
gate insulator. MPB is a combination of two crystalline phases between the orthorhombic phase of the ferroelectric (FE) phase and the tetragonal phase of the anti-FE (AFE) phase, which exhibits the maximum DE constant (
$\kappa \sim {64}$
) of the HZO film. A 30 nm-thick film of MPB HZO (Hf:Zr = 1:5) was used as the high-gate insulator in TFT. Also, by inserting 1 nm-thick AlO between the oxide channel and the HZO gate insulator, we mitigated the impact of charge trapping on the electrical properties. Ultimately, we used a pulse with a rise duration of 50 ns for ultrafast
${I}_{D}$
–
${V}_{G}$
to estimate intrinsic mobility. The intrinsic mobility of the MPB HZO + AlO device was found to be 20.9 cm2/
$\text{V}\cdot \text{s}$
, which is equivalent to the mobility of a SiO2 gate insulator in the same device. The findings of this research are noteworthy as we assessed the electrical characteristics of oxide TFT using MPB HZO as a gate insulator for the first time.