Engineers at Cornell University have made a semiconductor with a record-wide “bandgap” of more than 7 electron volts, and they’ve already turned it into a working transistor. Materials this extreme normally behave like insulators, so getting one to carry current at all is a real step, the team reports in Nature.
Why it matters: a huge share of the world’s electricity passes through power electronics, in car chargers, data centres and the grid. Wider-bandgap materials can handle much stronger electric fields, which could one day mean smaller converters that waste less energy as heat.
What a bandgap is, in plain words
Think of a bandgap as a wall that electrons must jump over before they can carry current. Silicon’s wall is low, at about 1.1 electron volts (eV, a tiny unit of energy). A taller wall makes a material harder to break down under high voltage.
There’s a catch: make the wall too tall and hardly any electrons get over it, so the material stops conducting. That’s why the old record sat at about 6 eV. It’s also why the chargers in your home use gallium nitride and silicon carbide, materials with wider bandgaps than silicon that are still practical to make.
How the Cornell team did it
The material is aluminium gallium oxide. Changing its mix of aluminium and gallium tunes the bandgap from 5.4 to 8.6 eV, but aluminium-rich versions have always conducted badly. The team, led by Darrell Schlom, grew thin films one atomic layer at a time on sapphire, and added silicon to supply mobile electrons.
The results above 6 eV, a range they call “colossal bandgap”, are striking:
- Conductivity: at room temperature, more than 100 million times higher than any earlier report in this range.
- Real devices: a diode and a transistor called the AlphaFET. The transistor’s current changes by more than four orders of magnitude, meaning more than 10,000 times between on and off.
- A cheap base: sapphire is plentiful and made at large scale, unlike diamond or cubic boron nitride, the previous record holder.
Don’t expect it in your charger yet
This is lab hardware. Electron microscopes found many defects in the films, and Schlom compares the material to other semiconductors at the very start of their development. The team says more work is needed to make the devices practical. We found no independent test of the results yet, so treat them as a strong first report.
What happens next
The next job is cleaner films with fewer defects, then devices that show the high-voltage strength the bandgap promises. The team points to electric vehicles, aircraft propulsion, the power grid and data centres as possible uses, along with lasers for telecoms.
Read next
- Altermagnetism: the third kind of magnet, and why chips care
- Rapidus 2nm: Japan’s bid to build the world’s tiniest chips
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Sources
- Cornell semiconductor sets record for widest bandgap – Cornell Chronicle, November 2026
- A 7-eV bandgap semiconductor based on silicon-doped α-(AlxGa1−x)2O3 – Nature, 7 October 2026
- Sapphire-grown semiconductor film sets bandgap record – Phys.org, 22 October 2026
