High mobility indium zinc oxide thin film field-effect transistors by semiconductor layer engineering

Area of Science:

• Materials Science
• Semiconductor Physics
• Thin-Film Technology

Background:

• Indium zinc oxide (IZO) is a promising transparent conductive oxide for thin-film transistors (TFTs).
• Controlling film morphology is crucial for optimizing charge transport in IZO TFTs.
• Previous studies often assumed a direct correlation between precursor concentration and film quality.

Purpose of the Study:

• To investigate the effect of precursor concentration on the performance of IZO thin-film transistors.
• To understand the relationship between film morphology and charge transport properties.
• To develop a model for layer formation in IZO films.

Main Methods:

• Fabrication of IZO thin-film transistors using a solution-based precursor route on silicon substrates.
• Characterization of film thickness variations using scanning probe microscopy.
• Analysis of electron density profiles via X-ray reflection measurements.
• Direct imaging of film morphology using scanning tunneling microscopy.

Main Results:

• Electron mobility in single-layer IZO films initially increased with precursor concentration, then decreased, contrary to saturation expectations.
• Thickness variations within films were identified as detrimental to charge transport.
• Multi-layer IZO films fabricated with low precursor concentrations achieved mobilities up to 19.7 cm²/V·s.
• Optimal precursor concentration varied significantly between single-layer and multi-layer film fabrication.

Conclusions:

• Dense, defect-free IZO films with high electron mobility are best achieved using multiple layers deposited from low-concentration precursor solutions.
• A qualitative model explaining IZO film morphology development based on precursor concentration was established.
• The findings challenge conventional approaches to IZO film deposition and offer a pathway to enhanced device performance.