Indium selenide (InSe), a next-generation 2D semiconductor nanomaterial, has seen attention for its superior electron mobility compared to silicon semiconductors and a saturation speed more than twice as fast, but its applications have been limited. Domestic researchers developed a technology that can enhance the performance of N-type and P-type semiconductors and anodes using indium selenide.
Professor Lee Ga-young of Korea Advanced Institute of Science and Technology (KAIST) and her research team announced on the 30th that they have developed a bipolar multifunctional transistor based on NANO semiconductor indium selenide. Indium selenide is an inorganic compound semiconductor composed of indium and selenium, and it forms a two-dimensional layered structure.
Until now, indium selenide has only been used as an N-type semiconductor material. An N-type semiconductor is one where negatively charged free electrons flow to create current. However, it has been difficult to implement P-type semiconductors with indium selenide. A P-type semiconductor is one that uses positively charged "holes" to generate current, but indium selenide could not induce holes.
The research team designed a new device structure to generate holes using indium selenide material. They successfully implemented bipolar characteristics, allowing electrons and holes to flow selectively by placing electrodes under the indium selenide and improving the metal-semiconductor junction properties. The newly developed bipolar semiconductor device can be applied to both N-type and P-type transistors.
In particular, in this study, both the current off/on ratios for N-type and P-type exceeded 1 billion. A higher off/on ratio indicates that high performance can be achieved even with low power. In the case of silicon semiconductor devices, the typical off/on ratio is generally below 100 million. For bipolar 2D semiconductors capable of driving both N-type and P-type, there has been no instance where both off/on ratios exceeded 100 million at the same time. A 2D semiconductor refers to a semiconductor with a layered structure in the vertical direction.
Professor Lee said, "Multifunctional devices generally require complex processing and structures, making fabrication and integration challenging. However, in this study, we succeeded in creating a multifunctional device that can implement various functions within a single device," adding, "This technology is expected to enhance processing efficiency and improve circuit design flexibility." She further noted, "This research sheds new light on the P-type applicability based on indium selenide and ultimately demonstrates its potential as a complementary multifunctional system."
The results of this research were published in the international journal of nanophysics, "Nano Letters," on the 18th and were also selected as a cover article for the journal.
Reference materials
Nano Letters (2024), DOI: https://doi.org/10.1021/acs.nanolett.4c04624