Manufacturing semiconductor devices has traditionally involved high temperatures and vacuum vessels, limiting efficiency and scalability. Researchers at the University of Illinois Urbana-Champaign have developed a process for creating high-performing transistors from solution-deposited semiconductors, offering a more efficient and scalable alternative.
Surprisingly, the semiconductor with the best performance has higher defect concentrations than its parent material. These defects, organized into ordered pairs, are actually the reason behind the record-high performance of the materials produced through the solution deposition process. This discovery has paved the way for functional circuits and systems like displays, opening up possibilities for various applications requiring high-performance electronics covering large areas.
The researchers have outlined a procedure for fabricating devices from an ordered defect compound semiconductor called CuIn5Se8, prepared by solution deposition. They have successfully created high-speed logic circuits operating in megahertz and a micro-display with a resolution of 508 pixels per inch. These transistors have the capability to drive inorganic micro-LEDs, providing a brighter and more durable alternative to current organic LEDs, but requiring more powerful transistors for each pixel.
The promise of solution deposition lies in its ability to occur at atmospheric pressure and lower temperatures, making it a desirable alternative to standard vapor deposition in terms of manufacturing throughput, cost, and substrate compatibility. While vapor deposition techniques produce materials with few defects, solution deposition must be further developed to achieve the same level of performance.
The researchers focused on copper-indium-selenium materials for their tunability, eventually developing a solution deposition process for these materials. By adjusting the proportions, they discovered a material suitable for electronics purposes, outperforming other solution-processable semiconductors and most semiconductors currently used in displays.
The new material, CuIn5Se8, boasts a charge mobility 500 times greater than amorphous silicon semiconductors used in large LCD displays and four times greater than metal oxide semiconductors used in organic LED displays. This high mobility positions CuIn5Se8 as a viable option for larger high-performance displays, offering comparable performance to low-temperature polycrystalline silicon used in smartphone displays but without the need for laser annealing.
The researchers also found that the ordered defect compound in CuIn5Se8 significantly improves charge mobility, leading to enhanced performance. By integrating these defect-tolerant semiconductors into displays with gallium nitride based micro-LEDs, they have demonstrated the potential for high-speed electronics and higher-performance displays.
While the process is ready for commercialization, the researchers are working to make it more environmentally friendly by replacing hydrazine, currently used in the process, with safer chemicals. The study, “Solution Processable Ordered Defect Compound Semiconductors for High-Performance Electronics,” is available online for further exploration.