Two South Korean Teams Advance Tellurium Semiconductor Technology

Two independent research groups in South Korea have published breakthrough findings on using tellurium in semiconductor technology—one focused on improving transistor performance, the other on developing new memory materials.

POSTECH Develops Technique to Reduce Contact Resistance in Tellurium Transistors

A research team at Pohang University of Science and Technology (POSTECH) has developed a method to dramatically reduce contact resistance in ultra-thin tellurium transistors.

Technical Approach

The team, led by Professor Byoung Hun Lee, applied a "Raised Source and Drain (RSD)" structure to tellurium transistors. In this approach:

• The channel thickness was maintained at 4 nanometers to minimize leakage current.
• Additional tellurium was deposited selectively on the source and drain contact areas using sputtering—a large-area, low-temperature deposition method suitable for mass production.

Performance Results

Experimental results reported by the team showed:

• A reduction in contact resistance from 97.5 kΩ·μm to 1.7 kΩ·μm—a decrease of approximately 50-fold.
• At -196°C, the on-state current increased by more than 17 times.

"We have broken through the chronic dilemma of ultra-thin semiconductors—where thinner channels traditionally resulted in higher resistance—with a novel band engineering approach called 'localized thickness control.'"
— Professor Byoung Hun Lee

Context

According to the researchers, as semiconductor devices become thinner, leakage current decreases but contact resistance at the metal-semiconductor interface increases due to a higher Schottky barrier. The RSD structure is a known technique in silicon processing, now successfully applied to tellurium.

Professor Lee added: "We expect this to become a core platform technology that can be widely applied not only to tellurium but also to enhancing the performance of various 2D and ultra-thin semiconductor devices."

Publication and Funding

The work was published in the journal ACS Nano. It was supported by the Nanomaterials Development Program and the Core Technology Development Project for National Semiconductor Research Laboratory through the National Research Foundation, funded by the Ministry of Science and ICT, Korea.

KAIST Team Observes Electrical Switching Mechanisms in Amorphous Tellurium

A separate research team, led by Professor Joonki Suh from the Korea Advanced Institute of Science and Technology (KAIST) in collaboration with Professor Tae-Hoon Lee's team from Kyungpook National University, has developed an experimental technique to monitor electrical switching processes and phase changes within nano-devices in real-time.

Research Methodology

The team utilized a method of instantaneous melting followed by rapid cooling (quenching) . This process allowed for the stable implementation of amorphous tellurium (a-Te)—a disordered, glass-like state of tellurium—within a nano-device.

Key Observations

The research identified specific threshold voltages and thermal conditions initiating electrical switching, along with segments where energy loss occurs. Key observations included:

• Microscopic Defects: Microscopic defects within amorphous tellurium were found to be crucial for electrical conduction.
• Two-Step Switching: When voltage exceeds a threshold, electricity flows in a two-step process: a rapid current increase along defects, followed by heat accumulation that melts the material.
• Self-Oscillation: Experiments maintaining the amorphous state without excessive current flow demonstrated a self-oscillation phenomenon, where voltage spontaneously increases and decreases.

The researchers stated that this study provides guidelines for the design of semiconductor materials for memory solutions, noting it represents the first successful implementation of amorphous tellurium in an actual electronic device and the systematic elucidation of its fundamental electrical switching principles.

Publication and Support

The findings were published online on January 13th in the journal Nature Communications, with Namwook Hur as the first author and Seunghwan Kim as the second author. Professor Joonki Suh served as the corresponding author.

The research received support from the National Research Foundation of Korea (NRF), the PIM (Processor-in-Memory) AI Semiconductor Core Technology Development Project, the Excellent Young Researcher Program funded by the Ministry of Science and ICT, and Samsung Electronics.