High Performance, Low Temperature Solution-Processed Barium and Strontium Doped Oxide Thin Film Transistors

Area of Science:

• Materials Science
• Semiconductor Physics
• Nanotechnology

Background:

• Amorphous mixed metal oxides are key semiconductors for thin-film transistors (TFTs).
• Indium gallium zinc oxide (IGZO) is a leading material in TFT applications.
• Improving the stability and processability of semiconductor layers is crucial for advanced electronics.

Purpose of the Study:

• To investigate alkaline earth (barium or strontium) doped InGaZnO (InBa(Sr)ZnO) as alternative channel layers for TFTs.
• To compare the electrical stress stability of these novel materials with conventional IGZO.
• To explore low-temperature solution-processing methods for fabricating these semiconductors.

Main Methods:

• Solution-processing of metal alkoxide precursors followed by annealing.
• Fabrication of InBa(Sr)ZnO films at high (450 °C) and low (200-225 °C) temperatures.
• Development of an "ink-on-demand" process utilizing alcoholysis reactions.
• Electrical bias stress measurements to evaluate device stability.

Main Results:

• Achieved high field-effect electron mobility up to 26 cm² V⁻¹ s⁻¹ at 450 °C.
• Demonstrated low-temperature processing yielding mobilities up to 4.4 cm² V⁻¹ s⁻¹.
• Sr- and Ba-doped semiconductors exhibited enhanced electrical stability and reduced threshold voltage shift compared to IGZO.
• Stability improvements were observed irrespective of process temperature and preparation method.

Conclusions:

• Alkaline earth doping (Sr, Ba) in InGaZnO enhances TFT electrical stability.
• The enhanced stability is attributed to the higher Gibbs energy of oxidation of Ba and Sr.
• Solution-processable InBa(Sr)ZnO offers a promising alternative to IGZO for stable and efficient TFT applications, even at low processing temperatures.