Recently, a research team from the University of Electronic Science and Technology of China pioneered stable high-mobility amorphous P-type (hole) semiconductor devices, overcoming over two decades of research bottlenecks in the field. This breakthrough further propels the development of modern information electronics and large-scale complementary metal-oxide-semiconductor (CMOS) technology. The achievement, a collaboration between the University of Electronic Science and Technology of China and Pohang University of Science and Technology in South Korea, was published online in Nature.
Compared to polycrystalline semiconductors, amorphous systems offer numerous advantages such as low cost, ease of processing, high stability, and uniform large-area fabrication. However, traditional amorphous hydrogenated silicon requires exploration of new materials due to insufficient electrical performance. Since the first report in 2004 on amorphous N-type (electron) indium gallium zinc oxide thin-film transistors (TFTs), significant progress has been made in semiconductor electronics and next-generation information display technologies.
Currently, the development of high-performance amorphous P-type semiconductors faces significant challenges, severely impeding the development of novel electronic devices and large-scale N-P complementary metal-oxide-semiconductor (CMOS) technology. Traditional oxide semiconductors suffer from poor hole transport efficiency due to high localized valence band tops and self-compensation effects, making them unsuitable for many applications. Consequently, researchers have devoted considerable effort to developing new non-oxide P-type semiconductors. However, these new materials only exhibit P-type characteristics in polycrystalline form. Furthermore, these materials suffer from inherent defects such as stability and uniformity and are difficult to integrate with existing industrial processes.
In light of this, the team proposed a novel tellurium (Te)-based composite amorphous P-type semiconductor design concept and achieved low-temperature film preparation using industrially compatible thermal evaporation processes, demonstrating the feasibility of application in high-performance, stable P-channel TFT devices and CMOS complementary circuits.
Through theoretical analysis, the research team revealed the important role played by the high-dispersion valence band top and shallow acceptor states composed of tellurium 5p orbitals, laying a crucial foundation for sufficient hole doping and effective hole transport in amorphous systems.
Furthermore, further research indicated that selenium alloying could effectively modulate hole concentration, achieving high-performance P-channel TFT devices with field-effect hole mobility of 15 cm^2/Vs and an on/off current ratio of approximately 10^7. These devices exhibited good bias stress and environmental stability, as well as wafer-scale uniformity. This tellurium-based material system outperforms other emerging amorphous P-type semiconductor materials reported to date, demonstrating superior economy, stability, scalability, and processability. Its fabrication process is perfectly compatible with industrial production lines and backend integration technologies. This composite phase strategy brings new inspiration for designing next-generation stable amorphous P-type semiconductor materials.
This research will drive the research wave of P-type semiconductor devices and take an important step in establishing commercially viable amorphous P-channel TFT technology and low-power CMOS integrated devices.
Related paper information: https://doi.org/10.1038/s41586-024-07360-w
