Ultra-thin electrode for 1nm atomic transistors

Technology News |
By Nick Flaherty

Researchers in Korea have developed a 2D electrode that can be used for the next generation of 2D atomic transistors with features smaller than 1nm.

The team at the Korea Institute of Science and Technology (KIST) led by Dr. Do Kyung Hwang of the Center for Opto-Electronic Materials and Devices and Professor Kimoon Lee of the Department of Physics at Kunsan National University (President: Jang-ho Lee) succeeded in implementing two-dimensional semiconductor-based electronic and logic devices controlled by a new ultra-thin electrode material (Cl-SnSe2).

This is a breakthrough as it allows single device performs the functions of both N-type and P-type devices, so there is no need to manufacture the N-type and P-type devices separately.

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The polarity control of 2D transistors such as those developed at imec in Belgium and MIT in the US remains a challenge because of the lack of a high-work-function electrode that completely eliminates Fermi-level pinning at metal–semiconductor interfaces. The team were able to show clean van der Waals with chlorine-doped tin diselenide Cl–SnSe2) as the high-work-function contact. This provides an interface that is free of defects and Fermi-level pinning and can pose nearly ideal Schottky barrier heights.

Complementary logic circuits with conventional two-dimensional semiconductor devices are difficult to combine for integrated circuits because they only exhibit the characteristics of either N-type or P-type devices due to the Fermi-level pinning phenomenon. In contrast, if the electrode material developed by the joint research team is used, it is possible to freely control the characteristics of the N-type and P-type devices by minimizing defects with the semiconductor interface.

Using Cl–SnSe2 as contacts, WSe2 2D transistors show pronounced p-type characteristics that are distinctly different from those of the devices with evaporated metal contacts, where n-type transport is observed. This ability to control the polarity enables the fabrication of functional logic gates and circuits, including inverters, NAND, and NOR gates.

“This development will contribute to accelerating the commercialization of next-generation system technologies such as artificial intelligence systems, which have been difficult to use in practical applications due to technical limitations caused by the miniaturization and high integration of conventional silicon semiconductor devices,” said Hwang. “The developed two-dimensional electrode material is very thin; hence, they exhibit high light transmittance and flexibility. Therefore, they can be used for next-generation flexible and transparent semiconductor devices.”


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