Photonic Curing of Solution-Processed Oxide Semiconductors with Efficient Gate Absorbers and Minimal Substrate Heating for High-Performance Thin-Film Transistors.

Abstract

In this study, photonic curing is used to rapidly and effectively convert metal-oxide sol–gels to realize high-quality thin-film transistors (TFTs). Photonic curing offers advantages over conventional thermal processing methods such as ultrashort processing time and compatibility with low-temperature substrates. However, previous work on photonically cured TFTs often results in significant heating of the entire substrate rather than just the thin film at the surface. Here, sol–gel indium zinc oxide (IZO)-based TFTs are photonically cured with efficient gate absorbers requiring as few as five pulses using intense white light delivering radiant energy up to 6 J cm–2. Simulations indicate that the IZO film reaches a peak temperature of ∼590 °C while the back of the substrate stays below 30 °C. The requirements and design guidelines for photonic curing metal-oxide semiconductors for high-performance TFT applications are discussed, focusing on the importance of effective gate absorbers and optimized pulse designs to efficiently and effectively cure sol–gel films. This process yields TFTs with a field-effect mobility of 21.8 cm2 V–1 s–1 and an Ion/Ioff ratio approaching 108, which exceeds the performance of samples annealed at 500 °C for 1 h. This is the best performance and highest metal-oxide conversion for photonically cured oxide TFTs achieved to date that does not significantly heat the entire thickness of the substrate. Importantly, the conversion from sol–gel precursors to the semiconducting metal-oxide phase during photonic curing is on par with thermal annealing, which is a significant improvement over previous pulsed-light processing work. The use of efficient gate absorbers also allows for the reduction in the number of pulses and efficient sol–gel conversion.