The observed vortices in each BaTiO3 layer aligned along a specific crystal direction and formed a robust striped pattern. Earlier polar textures of this kind had been observed almost exclusively in lead-containing superlattices comprising ultrathin ferroelectric and dielectric titanate layers on oxide substrates. The reported system therefore extends the material and substrate combinations in which polar topological textures can occur. The authors describe the result as a possible route toward incorporating complex ferroelectric states into silicon-based technologies, but the research does not demonstrate a device-level application.

Mechanical strain from the silicon substrate was identified as an important factor in producing the pattern. The first author, doctoral student Valentin Hevelke, said that this was the first realization of periodically ordered vortices in BaTiO3 superlattices on silicon and that silicon provides the strain needed to induce the reported pattern. The samples also showed reversible temperature-dependent behavior: heating caused a structural phase transition and the polar texture disappeared, while cooling to room temperature caused the polar texture to re-form. The supplied release does not quantify switching speed, electrical control, endurance or operation under applied fields, so it does not establish a practical switching process or device function.

Phase-field modelling by a group at Pennsylvania State University reproduced the coupling between the BaTiO3 and SrTiO3 layers through electrostatic forces and mechanical strain. The simulations also explained how the vortex tubes in the BaTiO3 layers align and provided a model for how the polar-texture pattern develops as strain changes. Overall, the work combined direct experimental characterization of a lead-free, silicon-supported superlattice with modelling of the electrostatic and mechanical effects associated with the observed vortex arrangement.

Subject of Research: Experimental study of polar vortices in lead-free BaTiO3/SrTiO3 superlattices on silicon

Article Title: Patterns of polar vortices in lead-free superlattices on silicon

Article References: Patterns of polar vortices in lead-free superlattices on silicon. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: polar vortices, BaTiO3, SrTiO3, silicon, superlattices, ferroelectric materials, molecular-beam epitaxy, phase-field modelling, mechanical strain, Patterns, polar, vortices

The physics behind the excitement lies in a deceptively simple scaling law. In rectifying power electronics, the Baliga figure of merit, which captures how well a semiconductor performs as a switch, is proportional to the bandgap raised to the power of 5.5. That steep exponent means that moving from silicon’s 1.1 electronvolts to gallium nitride’s 3.4 electronvolts already transforms what is possible in converters, chargers and grid infrastructure. Moving to a colossal bandgap above 6 electronvolts, the regime the Cornell-led team now enters, promises another leap in critical electric field and therefore in the voltage a device can block per unit thickness. Thinner devices switch faster, dissipate less heat and shrink the passive components around them, which is why the pursuit of ever-wider bandgaps has become one of the most competitive frontiers in materials science.

Yet widening the bandgap has historically come at a punishing cost: the loss of dopability. The defining trick of semiconductors is that their conductivity can be tuned over many orders of magnitude by deliberately introducing impurity atoms, a capability that underpins every transistor and diode ever made. As bandgaps grow, dopants tend to become so deeply bound that they fail to release their carriers at room temperature, and materials that were once dismissed as insulators, including gallium nitride, silicon carbide, aluminium nitride, gallium oxide and germanium oxide, only became useful semiconductors after years of work reducing defect densities and finding the right dopants. Diamond and cubic boron nitride, despite their superb intrinsic properties, remain locked behind enormous synthesis barriers: high pressures, tiny crystals, prohibitive costs and difficulty scaling. The new result breaks that trend by achieving record bandgap and record conductivity on one of the cheapest substrates in the industry.

The material at the heart of the study is the corundum-structured alloy α-(Al_xGa_1−x)₂O₃, in which gallium atoms in α-gallium oxide are progressively replaced by aluminium to widen the gap. The films were grown by suboxide molecular-beam epitaxy, a technique in which the metal sources are supplied as suboxides rather than pure elements, allowing adsorption-controlled growth of stoichiometric oxide films. The team grew the layers on sapphire, which is itself crystalline aluminium oxide, meaning the substrate is chemically identical to the aluminium-rich end of the alloy system. Sapphire is abundant, inexpensive, available in exceptional crystalline quality and produced at massive scale for everything from watch faces to LED wafers, with crystals as large as hundreds of kilograms grown by the Kyropoulos method. Building colossal-bandgap electronics on such a substrate is a decisive economic advantage over diamond and cubic boron nitride, which require high-pressure synthesis and yield only small, costly samples.

The headline number is conductivity. In the colossal-bandgap regime above 6 electronvolts, the silicon-doped α-(Al_xGa_1−x)₂O₃ films exhibit room-temperature conductivities more than 100 million times higher than all previous reports for materials in this range. Previous efforts to dope the corundum-structure alloy had achieved conductive films only up to bandgaps of about 6.22 electronvolts, and the conductivity collapsed rapidly as aluminium content rose. The new work shows that silicon, acting as a donor on the cation sublattice, can still ionize and release electrons even when the bandgap exceeds 7 electronvolts, provided the growth conditions are tuned correctly. Temperature-dependent Hall measurements on the films revealed carrier freeze-out as samples were cooled, allowing the researchers to extract donor densities and donor activation energies and to confirm that the conduction observed at room temperature arises from thermally activated, deliberately introduced silicon donors rather than accidental defects.

Characterizing such films demanded an unusually broad arsenal of techniques. High-resolution scanning transmission electron microscopy revealed atomically sharp, flat interfaces between the sapphire substrate, the buffer layers and the doped channel, with misfit dislocations confined to the earliest interface. Spectroscopic ellipsometry, performed at multiple angles of incidence and azimuthal orientations to account for the anisotropy of the corundum crystal structure, was used to determine the bandgap of each layer. Secondary ion mass spectrometry quantified the silicon incorporation down to a noise floor of roughly 1.2 times 10 to the 19 per cubic centimetre, while atom probe tomography mapped the three-dimensional distribution of silicon, aluminium and gallium atoms, showing that the alloy mixing follows a random, binomial distribution with no clustering. X-ray diffraction confirmed the crystal phase and composition of the doped overlayers through sharp reflections corresponding to aluminium fractions near 0.52.

Theory played an equal role in interpreting the results. Collaborators at the University of Texas at Austin, including Viet-Anh Ha, Nick Pant and Feliciano Giustino, calculated the theoretical electron mobilities of α-(Al_xGa_1−x)₂O₃ as a function of aluminium content and carrier density using density functional theory and electron-phonon coupling methods. Their calculations, which included phonon scattering, ionized impurity scattering and alloy scattering, and which accounted for the directional dependence of transport parallel and perpendicular to the basal plane, provided benchmarks against which the measured mobilities could be judged. Because the alloy is highly anisotropic, with bandgap energies and dielectric properties that depend on crystallographic direction, such first-principles guidance is essential for designing devices that exploit the material’s best transport directions.

Crucially, the team did not stop at films. They fabricated a Schottky barrier diode, dubbed the AlphaDiode, and a field-effect transistor, the AlphaFET, both with colossal-bandgap channels. The transistor structure stacked an aluminium-rich buffer on sapphire, a silicon-doped α-(Al_0.51Ga_0.49)₂O₃ channel, and a heavily doped regrown contact layer to achieve low-resistance ohmic access to the channel. The demonstration of both a rectifying diode and a transistor proves that the material can be patterned, contacted and switched, the minimum requirements for a practical electronic platform. These first devices are proof of concept rather than production-ready components, but they establish that doping, regrowth and contact formation, the traditional stumbling blocks for ultra-wide-bandgap materials, can all be executed on this oxide system.

The broader significance is strategic. Power electronics built on silicon carbide and gallium nitride are already reshaping electric vehicles, data centres and renewable energy systems, and gallium oxide in its beta phase has attracted intense interest because it can be grown from its own melt. The corundum-structure alloy reported here extends the reachable bandgap beyond anything doped before, and it does so on sapphire wafers that are already manufactured at scale, which the authors argue facilitates rapid development and adoption of colossal-bandgap electronics. The team has filed a provisional patent covering the growth procedure for conductive silicon-doped α-(Al,Ga)₂O₃ and the device structures that use it. Challenges certainly remain, including the modest mobilities typical of oxide alloys, deep donor levels that limit carrier activation, and the need for p-type doping, which remains unsolved. But the central barrier, the belief that semiconductors above 6 electronvolts cannot be made conductive, has now been decisively broken, and with it the assumption that the future of power electronics must be built on ever more expensive and difficult crystals.

Subject of Research: Silicon-doped α-(AlxGa1−x)2O3 as a record 7-eV bandgap semiconductor for colossal-bandgap power electronics

Article Title: A 7-eV bandgap semiconductor based on silicon-doped α-(AlxGa1−x)2O3

Article References: Steele, J., Bhattacharya, D., Nomoto, K., Pieczulewski, N. A., Sorensen, P., Ha, V.-A., Pant, N., Shukla, I., Das, S., Kilic, U., Ramesh, M., Giustino, F., Mazumder, B., Senevirathna, M. K. I., Williams, M. D., Schubert, M., Muller, D. A., Xing, H. G., Jena, D., & Schlom, D. G. (2026). A 7-eV bandgap semiconductor based on silicon-doped α-(AlxGa1−x)2O3. Nature. https://doi.org/10.1038/s41586-026-11085-3

Image Credits: AI Generated

DOI: 10.1038/s41586-026-11085-3

Keywords: colossal-bandgap semiconductor, alpha-gallium oxide, aluminum gallium oxide alloy, silicon doping, suboxide molecular-beam epitaxy, sapphire substrate, power electronics, Baliga figure of merit, Schottky diode, field-effect transistor, wide-bandgap materials, molecular-beam epitaxy

The partnership is not starting from a blank page. Under the memorandum, a joint research team has already completed first-phase, hands-on evaluations of superconducting quantum RF sensors for signals intelligence applications, conducted at the Jesper Munch Quantum Laboratories at Adelaide University in South Australia. Signals intelligence, the discipline of collecting, intercepting and analyzing electronic signals, underpins defense planning, secure communications and emergency response, and the sensors at the heart of this collaboration are designed to give analysts more usable information from the same crowded electromagnetic environment.

The physics behind the approach is rooted in the behavior of electrons inside superconducting materials. In such materials, RF signals have a dramatic effect on the dynamics of electrons, the negatively charged building blocks of atoms. Ultrasensitive, longer-range quantum RF sensing devices exploit changes in electron trajectory to extract more information from the RF environment than conventional antennas can manage. Precision circuits fabricated from superconducting materials convert those microscopic responses into raw data that yields accurate signal measurements, forming the basis of a sensing architecture that its developers argue outperforms traditional hardware in both sensitivity and information content.

Superconducting quantum RF systems leverage the unique properties of superconducting materials to detect and characterize signals across a broad swath of the electromagnetic spectrum. That breadth matters because the practical alternative, especially aboard military ships and aircraft where every cubic meter is contested, is a collection of bulky antennas each tuned to a portion of the spectrum. Compact quantum systems offer the potential to replace those installations outright, collapsing multiple frequency-specific apertures into a single small package.

Staff Engineer Michael Quinn, who leads quantum RF research and development in SwRI’s Defense and Intelligence Solutions Division offices in Warner Robins, Georgia, framed the size advantage as fundamental rather than incremental. Unlike conventional antennas, which grow bulkier as frequencies get lower, quantum RF device size is independent of frequency, he explained. According to Quinn, these systems achieve broad coverage from kilohertz to terahertz with the same compact hardware, providing more critical information while occupying less space. That combination, he noted, is a major advantage for defense and intelligence missions where size, weight and power are critical considerations, the classic SWaP constraints that shape nearly every airborne and shipboard system design.

The hardware that makes this possible is grown, in a literal sense, at Adelaide University. The university’s quantum laboratories house a state-of-the-art molecular beam epitaxy system, or MBE, that builds advanced superconductor and quantum materials one atomic layer at a time, a process its researchers liken to a 3D printer operating at the atomic scale. The MBE transforms raw materials into a Superconducting QUantum Interference Device, better known as a SQUID, which is then supercooled to minus 452.47 degrees Fahrenheit to activate its superconducting properties and its characteristic RF wave response. At those cryogenic temperatures, the device becomes sensitive to extraordinarily faint electromagnetic signals.

Cryogenics remains one of the technology’s biggest practical hurdles, and reducing that burden is an explicit goal of the collaboration. Researchers are exploring new material architectures designed to raise SQUID operating temperatures, cut cooling requirements and improve portability and operational practicality. Every degree by which the operating temperature can climb translates into smaller, lighter and less power-hungry cooling systems, which in turn determines whether quantum RF sensors can leave the laboratory and fly on real platforms. The partnership deliberately pairs Adelaide University’s expertise in superconducting quantum materials and sensor development with SwRI’s strengths in advanced RF engineering, signals processing and operational applications, covering the full chain from atomic-scale fabrication to fielded mission use.

Professor Giuseppe C. Tettamanzi, director of the Jesper Munch Quantum Laboratories and leader of Adelaide University’s superconducting quantum technologies research program, described how the first phase of joint work unfolded. The SwRI team tested and assessed selected performance metrics of the superconducting quantum RF technology developed by Adelaide University, he said. By combining their complementary expertise, he added, the two institutions are accelerating the development and maturation of quantum RF technologies with the potential to address the challenges of increasingly congested electromagnetic environments and complex operational scenarios. Tettamanzi also positioned the project as an example of the value of deep scientific alliances between Australia and the United States in advancing technologies critical to future security and economic prosperity.

The timing of the agreement reflects a broader surge of public investment in quantum science, which spans computing, communications and sensing and is being backed worldwide as well as at state and federal levels in the United States. In Texas, the recent Texas Quantum Initiative supports strategic planning for quantum technology funding and workforce training, an effort that gives in-state organizations such as SwRI a policy backdrop for expanding their quantum portfolios. At the federal level, the U.S. Department of War announced in June a Post Quantum Cryptography Strategy aimed at protecting critical government and military systems from emerging quantum threats, underscoring how quantum technologies are simultaneously viewed as an opportunity for new capabilities and a risk requiring defensive preparation.

For the engineers involved, the collaboration represents a rare chance to work at the frontier of an emerging discipline before it hardens into standard practice. Institute Engineer David Brown, based in Warner Robins and part of SwRI’s quantum technology exploration team, called quantum RF sensing an incredible new area of technology and described the project as a once-in-a-lifetime opportunity to be on the absolute cutting edge of science and explore the application of the most advanced technology of our lifetime. SwRI, he said, is eager to add these groundbreaking capabilities for its government and industry clients. With the memorandum of understanding now in place, the two institutions have established a foundation for future research, technology maturation and opportunities in quantum sensing, advanced RF systems and related mission applications, and the first-phase evaluations suggest the compact, cryogenically cooled sensors they are refining could eventually do the work of antenna farms many times their size.

Subject of Research: Superconducting quantum radio frequency sensing for signals intelligence applications

Article Title: SwRI, Adelaide University sign quantum RF research and development MOU

Article References: SwRI, Adelaide University sign quantum RF research and development MOU. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: quantum sensing, radio frequency, superconductors, SQUID, signals intelligence, SwRI, Adelaide University, molecular beam epitaxy, defense technology, electromagnetic spectrum, quantum materials, research partnership