Cornell engineers have developed a semiconductor material with a record-setting bandgap and turned it into working devices, opening the door to electronics that handle much higher voltages while wasting less energy.
Semiconductors with wider bandgaps can withstand stronger electric fields before breaking down, making them attractive for applications such as electric vehicles and power-grid infrastructure.
The record-setting material, detailed in a study published Oct. 7 in Nature, is made from silicon-doped aluminum gallium oxide and has a bandgap exceeding 7 electron volts. It represents a major leap beyond the previous record of about 6 electron volts – a threshold that has proved difficult to surpass because materials with wider bandgaps tend to behave more like insulators than semiconductors.
“The first reaction I heard from my scientific friends was, ‘that’s impossible,'” said senior author Darrell Schlom, the Tisch University Professor in the Department of Materials Science and Engineering in the Cornell Duffield College of Engineering. “I must admit that, at first, the result did seem too good to be true.”
Achieving the record required getting electricity to flow through the material in a controllable way. Schlom’s doctoral student and lead author on the study, Jacob Steele, grew the thin films of silicon-doped aluminum gallium oxide using suboxide molecular-beam epitaxy, a technique that allows crystalline materials to be built up one layer at a time under carefully controlled conditions. By incorporating silicon atoms into the material at sufficiently low temperature, he introduced mobile electrons that carry electrical current.
In the colossal bandgap range, defined as greater than 6 electron volts, the silicon-doped films exhibited room-temperature conductivity more than 100 million times higher than previously reported for materials in this category, according to the study. But it wasn’t until his research colleagues fabricated the material into working devices that Schlom realized the result “was real and potentially important for technology.”
Collaborators Huili Grace Xing, the William L. Quackenbush Professor, and Debdeep Jena, the David E. Burr Professor – both hold dual appointments in the Department of Materials Science and Engineering and the School of Electrical and Computer Engineering in Duffield Engineering – oversaw the development of a working diode and a field-effect transistor, dubbed the AlphaFET, using the material. Jena’s doctoral student and co-lead author, Debaditya Bhattacharya, designed, fabricated and measured the device.
“Making a transistor allows us to simultaneously demonstrate an essential building block of electronic systems as well as several of the semiconductor’s unique properties,” Xing said. “That includes control of conductivity over several orders of magnitude by both doping and field effect. The preliminary transistors show more than four orders of magnitude change in current modulated by the capacitively-coupled metal gate and the colossal bandgap channel.”
The record-setting achievement also stands out for using sapphire as the substrate on which the material was grown. Unlike some ultrawide-bandgap materials that are difficult and expensive to manufacture in useful sizes, sapphire is widely available and produced at large scale.
Jena said further work will be needed to make the devices practical, but called the semiconductor advancement a “game-changing platform” that holds immense promise for the near future.
“This will enable efficient electrical propulsion systems for terrestrial and aerial vehicles, power electronics for data centers, and several new applications of interest for commercial and defense applications,” Jena said. “Colossal bandgap semiconductors will also enable telecom relevant quantum cascade lasers and vacuum UV photonic devices that have not been possible in the past.”
David Muller, the Samuel B. Eckert Professor of Engineering in the School of Applied and Engineering Physics, and Naomi Pieczulewski, Ph.D. ’26, contributed to the study by using an electron microscope to investigate defects in the material.
“They saw a large number of defects in this new semiconductor, akin to the state of other semiconductors at the beginning of their development, indicating that there is lots of room to further improve the properties and devices made with this semiconductor as these defects are tamed and the material can operate at its full potential,” Schlom said.
The research was supported by the Air Force Research Laboratory-Cornell Center for Epitaxial Solutions and the National Science Foundation through work conducted at the Cornell NanoScale Facility and the Platform for the Accelerated Realization, Analysis, and Discovery of Interface Materials. The research also used shared facilities at the Cornell Center for Materials Research.
Syl Kacapyr is associate director of marketing and communications for Duffield Engineering.
