Quantum tunneling transistor; heat in thin films; transparent conducting oxide.
Researchers from MIT and University of Udine fabricated a transistor that uses ultrathin layers of gallium antimonide and indium arsenide arranged in vertical nanowire heterostructures with a diameter of 6nm. The quantum tunneling effects of the material enable it to simultaneously achieve low-voltage operation and high performance.
“This is a technology with the potential to replace silicon, so you could use it with all the functions that silicon currently has, but with much better energy efficiency,” said Yanjie Shao, an MIT postdoc, in a press release.
The small size and 3D geometry of the transistors enabled quantum confinement, where an electron is confined to a space that is so small that it can’t move around, resulting in a change in the effective mass of the electron and the properties of the material.
“We have a lot of flexibility to design these material heterostructures so we can achieve a very thin tunneling barrier, which enables us to get very high current,” said Shao. “This is the first time we have been able to achieve such sharp switching steepness with this design.”
When the researchers tested their devices, the sharpness of the switching slope was below the fundamental limit that can be achieved with conventional silicon transistors. They said the devices also performed about 20 times better than similar tunneling transistors. [1]
Researchers from the University of Virginia, University of Rhode Island, and Intel investigated how thermal conductivity works in ultra-thin copper films to confirm a key principle governing heat flow.
The team focused on Matthiessen’s rule, which helps predict how different scattering processes influence electron flow, to see if it still held true for nanoscale materials. Using steady-state thermoreflectance (SSTR), the team measured copper’s thermal conductivity and cross-checked it with electrical resistivity data to see whether the rule could reliably describe the way heat moves through copper thin films.
“Think of it as a roadmap,” said Patrick E. Hopkins, professor of engineering at UVA, in a release. “With the validation of this rule, chip designers now have a trusted guide to predict and control how heat will behave in tiny copper films. This is a game-changer for making chips that meet the energy and performance demands of future technologies.” [2]
Researchers from the University of Minnesota and California Institute of Technology developed an ultra-wide band gap material that allows electrons to move faster while remaining transparent to both visible and ultraviolet light.
“This breakthrough is a game-changer for transparent conducting materials, enabling us to overcome limitations that have held back deep ultra-violet device performance for years,” said Bharat Jalan, professor in the University of Minnesota’s Department of Chemical Engineering and Materials Science, in a statement.
The transparent conducting oxide is a thin-layered heterostructure comprised of SrSnO3/La:SrSnO3/GdScO3 that demonstrated enhanced transparency and conductivity in the deep-ultraviolet spectrum, with potential use in high-power and optoelectronic devices operating in demanding environments.
“Through detailed electron microscopy, we saw this material was clean with no obvious defects, revealing just how powerful oxide-based perovskites can be as semiconductors if defects are controlled,” said Andre Mkhoyan, professor in the University of Minnesota Department of Chemical Engineering and Materials Science, in a statement. [3]
[1] Shao, Y., Pala, M., Tang, H. et al. Scaled vertical-nanowire heterojunction tunnelling transistors with extreme quantum confinement. Nat Electron (2024). https://doi.org/10.1038/s41928-024-01279-w
[2] Islam, M.R., Karna, P., Tomko, J.A. et al. Evaluating size effects on the thermal conductivity and electron-phonon scattering rates of copper thin films for experimental validation of Matthiessen’s rule. Nat Commun 15, 9167 (2024). https://doi.org/10.1038/s41467-024-53441-9
[3] Fengdeng Liu et al.,Deep-ultraviolet transparent conducting SrSnO3 via heterostructure design. Sci. Adv. 10, eadq7892 (2024). https://doi.org/10.1126/sciadv.adq7892
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