Nav: Home

Measurement of semiconductor material quality is now 100,000 times more sensitive

April 09, 2019

The enhanced power of the new measuring technique to characterize materials at scales much smaller than any current technologies will accelerate the discovery and investigation of 2D, micro- and nanoscale materials.

Being able to accurately measure semiconductor properties of materials in small volumes helps engineers determine the range of applications for which these materials may be suitable in the future, particularly as the size of electronic and optical devices continues to shrink.

Daniel Wasserman, an associate professor in the Department of Electrical and Computer Engineering in the Cockrell School of Engineering, led the team that built the physical system, developed the measurement technique capable of achieving this level of sensitivity and successfully demonstrated its improved performance. Their work was reported today in Nature Communications.

The team's design approach was focused on developing the capability to provide quantitative feedback on material quality, with particular applications for the development and manufacturing of optoelectronic devices. The method demonstrated is capable of measuring many of the materials that engineers believe will one day be ubiquitous to next-generation optoelectronic devices.

Optoelectronics is the study and application of electronic devices that can source, detect and control light. Optoelectronic devices that detect light, known as photodetectors, use materials that generate electrical signals from light. Photodetectors are found in smartphone cameras, solar cells and in the fiber optic communication systems that make up our broadband networks. In an optoelectronic material, the amount of time that the electrons remain "photoexcited," or capable of producing an electrical signal, is a reliable indicator of the potential quality of that material for photodetection applications.

The current method used for measuring the carrier dynamics, or lifetimes, of photoexcited electrons is costly and complex and only measures large-scale material samples with limited accuracy. The UT team decided to try using a different method for quantifying these lifetimes by placing small volumes of the materials in specially designed microwave resonator circuits. Samples are exposed to concentrated microwave fields while inside the resonator. When the sample is hit with light, the microwave circuit signal changes, and the change in the circuit can be read out on a standard oscilloscope. The decay of the microwave signal indicates the lifetimes of photoexcited charge carriers in small volumes of the material placed in the circuit.

"Measuring the decay of the electrical (microwave) signal allows us to measure the materials' carrier lifetime with far greater accuracy," Wasserman said. "We have discovered it to be a simpler, cheaper and more effective method than current approaches."

Carrier lifetime is a critical material parameter that provides insight into the overall optical quality of a material while also determining the range of applications for which a material could be used when it's integrated into a photodetector device structure. For example, materials that have a very long carrier lifetime may be of high optical quality and therefore very sensitive, but may not be useful for applications that require high-speed.

"Despite the importance of carrier lifetime, there are not many, if any, contact-free options for characterizing small-area materials such as infrared pixels or 2D materials, which have gained popularity and technological importance in recent years," Wasserman said.

One area certain to benefit from the real-world applications of this technology is infrared detection, a vital component in molecular sensing, thermal imaging and certain defense and security systems.

"A better understanding of infrared materials could lead to innovations in night-vision goggles or infrared spectroscopy and sensing systems," Wasserman said.

High-speed detectors operating at these frequencies could even enable the development of free-space communication in the long wavelength infrared - a technology allowing for wireless communication in difficult conditions, in space or between buildings in urban environments.
-end-
The research was funded by Air Force Research Laboratories and is part of an ongoing collaboration between Wasserman and his Mid-IR Photonics Group at UT, close collaborators at Eglin Air Force Base and researchers from The Ohio State University, University of Wisconsin and Sandia National Laboratories.

University of Texas at Austin

Related Engineers Articles:

Engineers help with water under the bridge and other tough environmental decisions
From energy to water to food, civil engineering projects greatly impact natural resources.
Dartmouth engineers develop new way to know liars' intent
Dartmouth engineering researchers have developed a new approach for detecting a speaker's intent to mislead.
Engineers tap DNA to create 'lifelike' machines
Tapping into the unique nature of DNA, Cornell engineers have created simple machines constructed of biomaterials with properties of living things.
UT engineers develop first method for controlling nanomotors
Engineers at UT Austin develop world's first method for controlling the motion of nanomotors with simple visible light as the stimulus.
Engineers get a grip on slippery surfactants
A Rice University group's innovative surfactant theory removes limitations of a 100-year-old model for interfacial behavior in enhanced oil recovery.
Now you see it: Invisibility material created by UCI engineers
Materials inspired by disappearing Hollywood dinosaurs and real-life shy squid have been invented by UCI engineers, according to new findings in Science this Friday.
Self-sealing miniature 'wound' created by engineers
Biomedical engineers have developed a miniature self-sealing model system for studying bleeding and the clotting of wounds.
Engineers program tiny robots to move, think like insects
While engineers have had success building tiny, insect-like robots, programming them to behave autonomously like real insects continues to present technical challenges.
Engineers create plants that glow
By embedding nanoparticles into the leaves of watercress, MIT engineers have induced the plant to give off dim light for nearly four hours.
Engineers 3-D print a 'living tattoo'
MIT engineers have devised a 3-D printing technique that uses a new kind of ink made from genetically programmed living cells.
More Engineers News and Engineers Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

In & Out Of Love
We think of love as a mysterious, unknowable force. Something that happens to us. But what if we could control it? This hour, TED speakers on whether we can decide to fall in — and out of — love. Guests include writer Mandy Len Catron, biological anthropologist Helen Fisher, musician Dessa, One Love CEO Katie Hood, and psychologist Guy Winch.
Now Playing: Science for the People

#542 Climate Doomsday
Have you heard? Climate change. We did it. And it's bad. It's going to be worse. We are already suffering the effects of it in many ways. How should we TALK about the dangers we are facing, though? Should we get people good and scared? Or give them hope? Or both? Host Bethany Brookshire talks with David Wallace-Wells and Sheril Kirschenbaum to find out. This episode is hosted by Bethany Brookshire, science writer from Science News. Related links: Why Climate Disasters Might Not Boost Public Engagement on Climate Change on The New York Times by Andrew Revkin The other kind...
Now Playing: Radiolab

Breaking Bongo
Deep fake videos have the potential to make it impossible to sort fact from fiction. And some have argued that this blackhole of doubt will eventually send truth itself into a death spiral. But a series of recent events in the small African nation of Gabon suggest it's already happening.  Today, we follow a ragtag group of freedom fighters as they troll Gabon's president - Ali Bongo - from afar. Using tweets, videos and the uncertainty they can carry, these insurgents test the limits of using truth to create political change and, confusingly, force us to ask: Can fake news be used for good? This episode was reported and produced by Simon Adler. Support Radiolab today at Radiolab.org/donate.