Researchers open door to custom-built semiconductor electrodes

Scientists have found a way to build semiconductor electrodes tailored to specific performance requirements, using a new material that combines metals with organic molecules instead of conventional metals alone. The breakthrough is expected to pave the way for custom electrodes that reduce power consumption and boost semiconductor performance.

KAIST announced Monday that a research team led by Professor Park Sun-a of its chemistry department had developed a semiconductor gate electrode using conductive metal-organic frameworks, or MOFs, in collaboration with Pukyong National University, POSTECH and Yonsei University.

Transistors are the basic components of semiconductors, regulating the flow of electrical current in response to electrical signals. The gate electrode controls that flow by applying voltage to switch the transistor on and off.

Metals that conduct electricity well are currently the dominant material for gate electrodes. Their electronic properties, however, are fixed by their chemical nature, making it difficult to freely adjust those properties to match the operating conditions of a given semiconductor.

To overcome that limitation, the research team turned to conductive MOFs — structures formed by bonding metals with organic molecules.

The team used chemical vapor deposition, a technique that reacts gaseous precursors to deposit material, to produce uniform MOF thin films. They then applied photolithography and etching processes — standard tools in semiconductor manufacturing — to pattern the films into fine electrodes of the desired shape.

Particularly notable was the team's use of two different etchants applied in sequence, which minimized material damage during processing. The team confirmed that the MOF's structure and electrical properties were largely preserved after fabrication.

The researchers tested the resulting electrodes on three different semiconductor materials: molybdenum disulfide (MoS₂), molybdenum ditelluride (MoTe₂) and oxide semiconductor IGZO.

Transistors equipped with the MOF electrodes showed current-control performance comparable to devices using conventional platinum electrodes.

The team also demonstrated scalability. When 23 IGZO transistors were fabricated on a single substrate with MOF gate electrodes applied, all 23 operated normally.

The team also verified durability. An IGZO transistor maintained stable performance after gate voltage was applied 400 consecutive times. An MoS₂ transistor likewise retained its electrode operating characteristics after being stored in open air for about a year.

Going forward, the team plans to test a wider range of MOF materials and verify large-area thin-film fabrication, fine-patterning precision and long-term reliability. The researchers also intend to expand the application of MOFs beyond gate electrodes to source and drain electrodes and semiconductor channels.

"This research demonstrated that conductive MOFs can be processed using existing semiconductor manufacturing techniques and used as actual transistor electrodes," Park said. "We expect this to be developed into custom electrodes whose electronic properties can be designed to suit the purpose of each device, enabling broad application in next-generation semiconductors."

The findings were published in the Sept. 15 issue of the international journal Advanced Materials.