Gallium-doped transistors boost computing power

Researchers from the Institute of Industrial Science, the University of Tokyo, have created a transistor from gallium-doped indium oxide (InGaOx). This material can be structured as a crystalline oxide, whose orderly, crystal lattice is suitable for electron mobility.

Transistors are integral components of modern electronics that amplify or switch electrical signals. As electronics become smaller, it is becoming increasingly difficult to continue scaling down silicon-based transistors. Now, the researchers from the University of Tokyo have developed a crystalline oxide transistor that features a ‘gate-all-around’ structure, whereby the gate, which turns the current on or off, surrounds the channel where the current flows.

“By wrapping the gate entirely around the channel, we can enhance efficiency and scalability compared with traditional gates,” said Anlan Chen, lead author of the study.

The researchers knew that they would need to introduce impurities to the indium oxide by ‘doping’ it with gallium. This would make the material react with electricity in a more favourable way. “Indium oxide contains oxygen-vacancy defects, which facilitate carrier scattering and thus lower device stability. We doped indium oxide with gallium to suppress oxygen vacancies and in turn improve transistor reliability,” said Masaharu Kobayashi, senior author.

The researchers used atomic-layer deposition to coat the channel region of a gate-all-around transistor with a thin film of InGaOx, one atomic layer at a time. After deposition, the film was heated to transform it into the crystalline structure needed for electron mobility. This process ultimately enabled the fabrication of a gate-all-around ‘metal oxide-based field-effect transistor’ (MOSFET).

“Our gate-all-around MOSFET, containing a gallium-doped indium oxide layer, achieves high mobility of 44.5 cm²/Vs. Crucially, the device demonstrates promising reliability by operating stably under applied stress for nearly three hours. In fact, our MOSFET outperformed similar devices that have previously been reported,” Chen said.

The research findings have provided the field with a new transistor design that considers the importance of materials and structure, marking a step towards the development of reliable, high-density electronic components suitable for applications with high computational demand, such as big data and artificial intelligence.

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