Tech
Room-temperature terahertz device opens door to 6G networks
In a world first, researchers at Nagoya University in Japan have successfully developed a resonant tunnel diode (RTD) that operates at room temperature made entirely from Group IV semiconductor materials.
The development of an RTD that operates at room temperature means the device could be deployed at scale for next-generation wireless communication systems. The use of only non-toxic Group IV semiconductor materials also supports more sustainable manufacturing processes.
This research marks a pivotal step toward terahertz wireless components that deliver unprecedented speed and data handling capacity with superior energy efficiency.
“Compared to InGaAs-based Group III-V RTDs that include toxic and rare elements, such as indium and arsenic, Group IV compounds-based RTDs are safer, lower cost, and offer advantages for creating integrated production processes,” said senior author Dr. Shigehisa Shibayama from the Nagoya University Graduate School of Engineering.
The results are published in the journal ACS Applied Electronic Materials.
Terahertz waves and quantum devices
Researchers have long struggled to achieve the high-speed and large-volume data transfer needed for sixth-generation (6G) cellular networks.
One promising solution is wireless communication using terahertz waves—electromagnetic waves that vibrate a trillion times per second, enabling ultra-high-speed data transmission. However, many technical challenges remain before this technology can be made practical for consumer applications.
A critical component for realizing terahertz communication is the RTD. This quantum device operates through negative differential resistance, a counterintuitive property where increasing voltage actually decreases current. When part of a properly designed circuit, this property allows the diodes to sustain high-frequency oscillations that would otherwise decay due to electrical losses.

Moving beyond laboratory constraints
The secret behind an RTD lies in its double-barrier structure, where electrons or holes tunnel through layers of different semiconductor materials, each only a few atoms thick. These layers have mainly been created from InGaAs-based Group III-V materials that include toxic and rare elements, such as indium and arsenic.
In previous research by the same group, the researchers created a p-type RTD using only Group IV materials, specifically germanium-tin (GeSn) and germanium-silicon-tin (GeSiSn) alloys. One limitation was that the diode only functioned at extremely low temperatures, around -263°C. Since consumer electronics and wireless systems cannot practically reach this level of cooling, the device would have remained a laboratory curiosity.
Shibayama and his colleagues have now discovered how to use only Group IV materials to produce a p-RTD that functions at room temperatures of around 27°C. This significant improvement opens new possibilities for the widespread adoption of terahertz semiconductor devices.

The research group achieved its breakthrough by introducing hydrogen gas during the layer formation process. They tested three different scenarios:
- introducing hydrogen gas to both the two GeSiSn layers and three GeSn layers
- introducing no hydrogen gas
- introducing hydrogen gas to only the three GeSn layers.
In the last scenario, hydrogen gas restricted island growth and mixing between layers, resulting in a smooth and well-ordered double-barrier structure.
“The RTD cannot function if these layers are mixed,” said Dr. Shibayama.
“If there are defects in the layers, electrons can tunnel through these easier routes, leading to current leakage. This leakage current needs to be reduced for negative differential resistance—the key property of an RTD—to occur.”
More information:
Shota Torimoto et al, Room-Temperature Operation of Ge1–xSnx/Ge1–x–ySixSny Resonant Tunneling Diodes Featured with H2 Introduction during Molecular Beam Epitaxy. ACS Applied Electronic Materials (2025). DOI: 10.1021/acsaelm.5c01049
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Tech
How Trump’s Plot to Grab Iran’s Nuclear Fuel Would Actually Work
President Donald Trump and top defense officials are reportedly weighing whether to send ground troops to Iran in order to retrieve the country’s highly enriched uranium. However, the administration has shared little information about which troops would be deployed, how they would retrieve the nuclear material, or where the material would go next.
“People are going to have to go and get it,” secretary of state Marco Rubio said at a congressional briefing earlier this month, referring to the possible operation.
There are some indications that an operation is close on the horizon. On Tuesday, The Wall Street Journal reported that the Pentagon has imminent plans to deploy 3,000 brigade combat troops to the Middle East. (At the time of writing, the order has not been made.) The troops would come from the Army’s 82nd Airborne Division, which specializes in “joint forcible entry operations.” On Wednesday, Iran’s government rejected Trump’s 15-point plan to end the war, and White House press secretary Karoline Leavitt said that the president “is prepared to unleash hell” in Iran if a peace deal is not reached—a plan some lawmakers have reportedly expressed concern about.
Drawing from publicly available intelligence and their own experience, two experts outlined the likely contours of a ground operation targeting nuclear sites. They tell WIRED that any version of a ground operation would be incredibly complicated and pose a huge risk to the lives of American troops.
“I personally think a ground operation using special forces supported by a larger force is extremely, extremely risky and ultimately infeasible,” Spencer Faragasso, a senior research fellow at the Institute for Science and International Security, tells WIRED.
Nuclear Ambitions
Any version of the operation would likely take several weeks and involve simultaneous actions at multiple target locations that aren’t in close proximity to each other, the experts say. Jonathan Hackett, a former operations specialist for the Marines and the Defense Intelligence Agency, tells WIRED that as many as 10 locations could be targeted: the Isfahan, Arak, and Darkhovin research reactors; the Natanz, Fordow, and Parchin enrichment facilities; the Saghand, Chine, and Yazd mines; and the Bushehr power plant.
According to the International Atomic Energy Agency, Isfahan likely has the majority of the country’s 60 percent highly enriched uranium, which may be able to support a self-sustaining nuclear chain reaction, though weapon-grade material generally consists of 90 percent enriched uranium. Hackett says that the other two enrichment facilities may also have 60 percent highly enriched uranium, and that the power plant and all three research reactors may have 20 percent enriched uranium. Faragasso emphasizes that any such supplies deserve careful attention.
Hackett says that eight of the 10 sites—with the exception of Isfahan, which is likely intact underground, and “Pickaxe Mountain,” a relatively new enrichment facility near Natanz—were mostly or partially buried after last June’s air raids. Just before the war, Faragasso says, Iran backfilled the tunnel entrances to the Isfahan facility with dirt.
The riskiest version of a ground operation would involve American troops physically retrieving nuclear material. Hackett says that this material would be stored in the form of uranium hexafluoride gas inside “large cement vats.” Faragasso adds that it’s unclear how many of these vats may have been broken or damaged. At damaged sites, troops would have to bring excavators and heavy equipment capable of moving immense amounts of dirt to retrieve them
A comparatively less risky version of the operation would still necessitate ground troops, according to Hackett. However, it would primarily use air strikes to entomb nuclear material inside of their facilities. Ensuring that nuclear material is inaccessible in the short to medium term, Faragasso says, would entail destroying the entrances to underground facilities and ideally collapsing the facilities’ underground roofs.
Softening the Area
Hackett tells WIRED that based on his experience and all publicly available information, Trump’s negotiations with Iran are “probably a ruse” that buys time to move troops into place.
Hackett says that an operation would most likely begin with aerial bombardments in the areas surrounding the target sites. These bombers, he says, would likely be from the 82nd Airborne Division or the 11th or 31st Marine Expeditionary Units (MEU). The 11th MEU, a “rapid-response” force, and the 31st MEU, the only Marine unit continuously deployed abroad in strategic areas, have reportedly both been deployed to the Middle East.
Tech
Amazon’s Spring Sale Is So-So, but Cadence Capsules Are a Bright Spot
The WIRED Reviews Team has been covering Amazon’s Big Spring Sale since it began at on Wednesday, and the overall deals have been … not great, honestly. So far, we’ve found decent markdowns on vacuums, smart bird feeders, and even an air fryer we love, but I just saw that Cadence Capsules, those colorful magnetic containers you may have seen on your social media pages, are 20 percent off. (For reference, the last time I saw them on sale, they were a measly 9 percent off.)
If you’re not familiar, they allow you to decant your full-sized personal care products you use at home—from shampoo and sunscreen to serums and pills—into a labeled, modular system of hexagonal containers that are leak-proof, dishwasher safe, and stick together magnetically in your bag or on a countertop. No more jumbled, travel-sized toiletries and leaky, mismatched bottles and tubes.
Cadence Capsules have garnered some grumbling online for being overly heavy or leaking, but I’ve been using them regularly for about a year—I discuss decanting your daily-use products in my guide to How to Pack Your Beauty Routine for Travel—and haven’t experienced any leaks. They do add weight if you’re trying to travel super-light, and because they’re magnetic, they will also stick to other metal items in your toiletry bag, like bobby pins or other hair accessories. This can be annoying, especially if you’re already feeling chaotic or in a hurry.
Otherwise, Capsules are modular, convenient, and make you feel supremely organized—magnetic, interchangeable inserts for the lids come with permanent labels like “shampoo,” “conditioner,” “cleanser,” and “moisturizer.” Maybe you love this; maybe you don’t. But at least if you buy on Amazon, you can choose which label genre you get (Haircare, Bodycare, Skincare, Daily Routine). If this just isn’t your jam, the Cadence website offers a set of seven that allows you to customize the color and lid label of each Capsule, but that set is not currently on sale.
Tech
Fellow Readers, Don’t Miss These E-Reader Sales
This is the older Kindle Scribe, but the price and features are the best you’ll get, especially when it’s on sale like this. I still reach for this model even though I have the newer third generation, and keep in mind the second generation will also get some of the newer software and experiences over time. With the sale, it’s half the price of the newer model.
If you’re already a Kindle reader and looking to upgrade, it’s likely because you want a new feature like a color screen. While the Kobo above is the better buy, if you want to stay in the Kindle ecosystem but add some color to your books, both the Colorsoft and Colorsoft Signature are on sale.
If you’re looking to spend as little as possible, the basic Kindle (11th generation) is still a great e-reader and is currently under $100. It can do almost everything the other Kindles can (except the Scribe) on a snappy black-and-white screen. It doesn’t have a warm front light either, but it’s still a great purchase for the price.
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