Highly Stable, Crystalline InGaO Thin-Film Transistors by 7% Lanthanum Incorporation.

Area of Science:

• Materials Science
• Electronics Engineering
• Semiconductor Physics

Background:

• High-mobility metal oxide semiconductor (MOS) thin-film transistors (TFTs) are crucial for modern electronics.
• Increasing indium (In) concentration in MOS enhances mobility but leads to depletion mode and instability.
• Developing stable, high-performance MOS TFTs requires addressing the trade-offs of high In content.

Purpose of the Study:

• To investigate the effect of lanthanum (La) incorporation on the properties of indium-gallium oxide (InGaO) films.
• To optimize LaInGaO TFTs for improved device performance and stability.
• To evaluate the potential of LaInGaO TFTs for large-area, cost-effective electronic applications.

Main Methods:

• Spray pyrolysis deposition of InGaO films at 375 °C substrate temperature.
• Incorporation of varying La ratios (3–20%) into the InGaO matrix.
• Fabrication and characterization of coplanar LaInGaO TFTs, including electrical performance and stability tests.

Main Results:

• La incorporation increased mass density and optical bandgap, while degrading crystallinity.
• Optimized 7% LaInGaO TFTs achieved a threshold voltage of 0.01 V and mobility of 30.63 cm²/V·s.
• Enhanced bias temperature and photostability were observed in 7% LaInGaO TFTs compared to pristine InGaO TFTs.
• Gate driver circuits using 7% LaInGaO TFTs showed fast switching times (437.3 ns rising, 557.9 ns falling).

Conclusions:

• Lanthanum incorporation effectively improves the stability and performance of InGaO-based TFTs.
• The optimized 7% LaInGaO composition offers a promising pathway for reliable, high-performance TFTs.
• Spray-pyrolyzed LaInGaO TFTs are suitable for cost-effective, large-area electronic applications.