Abstract
In this paper, a TiO2/Al2O3/TiO2/Al2O3/TiO2 (TATAT) stacked structure was developed as a gate dielectric for amorphous ZnSnO (ZTO) thin-film transistor (TFT) applications. The TATAT insulator has a relative permittivity and leakage current density of 11 and 4.44 × 10-7 A/cm2 at 1 MV/cm, respectively. As compared with the AlTiO (ATO) compound dielectric, the ZTO TFT device with a TATAT stacked dielectric exhibited a lower threshold voltage of 0.56 V, a higher Ion/Ioff current ratio of 1.2x 10-8, a larger field-effect mobility of 86.6 cm2/Vs, and a smaller subthreshold swing of 0.2 V/decade. Furthermore, the positive shift of threshold voltage is less than 0.15 V under positive bias stress. The results suggest that stack TATAT films is a promising gate dielectric for solution-processed TFT devices with high mobility and stability.
Highlights
Various high-k materials such as ZrO2, HfO2, TiO2 are adopted as the gate dielectric of the thin-film transistor (TFT) in order to reduce its operating voltage, and decrease the power consumption of electronic products.[1,2,3] most of the high-k dielectric presents issues that maybe degrade both the performance and stability of oxide thin-film transistors (TFTs), such as exhibiting a polycrystalline structure and a rough surface.[4]
The presence of Al2O3 eventually improved the thermal stability of TiO2, keeping the TATAT dielectric amorphous after anneal, which substantially reduced the presence of defect and leakage current path that have generated in the crystalline TiO2 film
TATAT dielectric have smoother surface, TiO2 can act as a surface modification that can significantly improve electrical property of amorphous oxide thin film transistor, which maybe result in the high mobility of TFT devices with TATAT stacked structure.[2]
Summary
Various high-k materials such as ZrO2, HfO2, TiO2 are adopted as the gate dielectric of the TFT in order to reduce its operating voltage, and decrease the power consumption of electronic products.[1,2,3] most of the high-k dielectric presents issues that maybe degrade both the performance and stability of oxide TFTs, such as exhibiting a polycrystalline structure and a rough surface.[4]. Most of the stacked dielectrics have been fabricated by vacuum deposition techniques nowadays, such as atomic layer deposition,[7,8,9,10] or magnetron sputtering.[11] Regarding solution-processed candidate high-k materials, TiO2 dielectrics with high k value (>80) are proposed to mix with Al2O3 for realizing low voltage driven devices.[12,13] And it has been studied to use the electron beam-irradiated stacked TiO2-Al2O3 structure as a passivation layer.[10] there are rare reports on the stacked TiO2-Al2O3 dielectric using solution technique. The ZnSnO (ZTO) thin-film transistors (TFTs) with TATAT gate dielectrics have been fabricated, demonstrating good electrical performance such as a saturation mobility of 86.6 cm2/Vs and an on/off current ratio of 108 etc
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