JSS Editors’ Choice article discusses AlGaN/GaN HEMTs

When it comes to putting technology in space, size and mass are prime considerations. High-power gallium nitride-based high electron mobility transistors (HEMTs) are appealing in this regard because they have the potential to replace bulkier, less efficient transistors, and are also more tolerant of the harsh radiation environment of space. Compared to similar aluminum gallium arsenide/gallium arsenide HEMTs, the gallium nitride-based HEMTs are ten times more tolerant of radiation-induced displacement damage.

Until recently, scientists could only guess why this phenomena occurred: Was the gallium nitride material system itself so inherently disordered that adding more defects had scant effect? Or did the strong binding of gallium and nitrogen atoms to their lattice sites render the atoms more difficult to displace?

The answer, according to scientists at the Naval Research Laboratory, is none of the above.

Examining radiation response

In a recent open access article published in the ECS Journal of Solid State Science and Technology entitled, “On the Radiation Tolerance of AlGaN/GaN HEMTs,” the team of researchers from NRL state that by studying the effect of proton irradiation on gallium nitride-based HEMTs with a wide range of initial threading dislocation defectiveness, they found that the pre-irradiation material quality had no effect on radiation response.

Additionally, the team discovered that the order-of-magnitude difference in radiation tolerance between gallium arsenide- and gallium nitride-based HEMTs is much too large to be explained by differences in binding energy. Instead, they noticed that radiation-induced disorder causes the carrier mobility to decrease and the scattering rate to increase as expected, but the carrier concentration remains significantly less affected than it should be.

(more…)

We’re delving into our archives as part of our continuing Masters Series podcasts. In 1995, ECS and the Chemical Heritage Foundation worked to compile various oral histories of some of the biggest names in electrochemical and solid state science.

One of those key figures was Norman Hackerman, a giant among giants. Hackerman was a world renowned scientist, an outstanding educator, a highly successful administrator, and a champion for basic research. Hear his voice once again as he tells colorful stories of the science, his life, and everything in between.

Listen and download these episodes and others for free through the iTunes Store, SoundCloud, or our RSS Feed. You can also find us on Stitcher.

The Death of Moore’s Law

The future of technology

The iconic Moore’s law has guided Silicon Valley and the technology industry at large for over 50 years. Moore’s prediction that the number of transistors on a chip would double every two years (which he first articulated at an ECS meeting in 1964) bolstered businesses and the economy, as well as took society away from the giant mainframes of the 1960s to today’s era of portable electronics.

But research has begun to plateau and keeping up with the pace of Moore’s law has proven to be extremely difficult. Now, many tech-based industries find themselves in a vulnerable position, wondering how far we can push technology.

Better materials, better chips

In an effort to continue Moore’s law and produce the next generation of electronic devices, researchers have begun looking to new materials and potentially even new designs to create smaller, cheaper, and faster chips.

“People keep saying of other semiconductors, ‘This will be the material for the next generation of devices,’” says Fan Ren, professor at the University of Florida and technical editor of the ECS Journal of Solid State Science and Technology. “However, it hasn’t really changed. Silicon is still dominating.”

Silicon has facilitated the growth predicted by Moore’s law for the past decades, but it is now becoming much more difficult to continue that path.

(more…)

Nanowire cooling

Flexible electrocaloric fabric of nanowire array can cool.
Image: Qing Wang/Penn State

The utilization of nanowires has opened a new branch of science for many researchers. While some have focused on applying this technology to energy systems, researchers from Penn State are using the nanowires to develop solid state personal cooling systems.

A new study from the university shows that nanowires could help develop a material for lightweight cooling systems, which could be incorporated into firefighting gear, athletic uniforms, and other wearables.

“Most electrocaloric ceramic materials contain lead,” says Qing Wang, professor of materials science and engineering at Penn State. “We try not to use lead. Conventional cooling systems use coolants that can be environmentally problematic as well. Our nanowire array can cool without these problems.”

This from Penn State:

Electrocaloric materials are nanostructured materials that show a reversible temperature change under an applied electric field. Previously available electrocaloric materials were single crystals, bulk ceramics, or ceramic thin films that could cool, but are limited because they are rigid, fragile, and have poor processability. Ferroelectric polymers also can cool, but the electric field needed to induce cooling is above the safety limit for humans.

(more…)

Texting while walkingSmartphones are amazing little bundles of electrochemistry. From the sensors that pick up your touch and analyze your voice to the battery that is small and powerful enough to provide enough power to run applications on demand – the innovative science behind smartphones has changed the lives of people around the world.

But sometimes those changes are not completely positive. With increased dependence on smartphones, many people now roam the sidewalk with their nose buried in their phones. According to The Wall Street Journal, the number of distracted pedestrians using cellphones is up 124 percent from 2010. Some researchers are even blaming portable electronic gadgets for 10 percent of pedestrian injuries and a half-dozen deaths each year.

In Germany, these distracted pedestrians have been deemed “sombies,” or “smartphone zombies.” And the German government isn’t just looking to throw out a new buzzword, they’re also seeking to solve this issue.

According to reports from The Local, the city of Augsburg recently installed rows of LED lights into the sidewalk that can sense when distracted pedestrians are approaching and give off a bright flash of red to warn them to not mindlessly wander into the street.

“We realized that the normal traffic light isn’t in the line of sight of many pedestrians these days,” said Tobias Harms of the Augsburg city administration in an interview with The Augsburger Allgemeine. “So we decided to have an additional set of lights – the more we have, the more people are likely to notice them.”

  • Page 3 of 3