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April 12, 2017

Grant funds research into electronics performance

Sometimes you can ask a service technician or engineer to make a house call if something goes wrong with your technology. But there are times when that is really not practical. 

Such as when the problem is on a satellite, in orbit. 

That’s why engineers take great pains to ensure remote electronic devices are as reliable as they are robust; that they can work for many years without significant changes or deterioration in performance. 

An engineering researcher at Southern Illinois University Carbondale is working on new ways to develop a better understanding of processes that erode electronics performance -- right down to the atomic level -- in a bid to boost the reliability of such devices, as well as lengthen their lives and improve accuracy. 

Shaikh Ahmed, professor of electrical and computer engineering, recently received a grant for almost $283,000 from the National Science Foundation to study and model how such devices fail and why. Ahmed’s work could lead to better, hardier electronic devices that are more impervious to the harsh effects of their environments, whatever those may be. 

Ahmed will use theory, mathematics and computer simulations to investigate the physics involved in the matter, looking at factors such as spatial and temporal distribution of defects, the effects of high temperature gradients, high electrical fields and phenomena such as inverse piezoelectric effect, which refers to how a material’s polarization can be flipped through mechanical stresses. 

Ahmed also will examine electrons as “energetic carriers” and how they behave in extremely fast transistors that have potential applications in wireless communication, homeland security radar and satellite systems. He also will look at how such emerging technologies will impact harsh-environment computing, sensor networks, cloud-networking and power conversion electronics. 

“We want to make sure that electronic devices, especially those in remote places, are reliable,” Ahmed said. “In technical terms, this also means that we need to be able to predict, via certain experiments, their lifetime fairly accurately before we deploy them.” 

This is especially true of electronic devices that use newer materials, such as gallium nitrides, in their construction. Such devices exhibit superior performance as compared to the conventional devices, but they also come with significant concerns about their lifetime and reliability, specifically when used in harsh environments, Ahmed said. 

The worsening in performance in such devices mainly is caused by defects at the atomic level, such as missing atoms, misalignment of atoms or the presence of unwanted atoms. Ahmed said. The time it takes to degrade the performance -- what researchers call the “time evolution” -- depends greatly on how electrons in the electrical current interact with such defects. 

“With time, many electrons that are passing through the tiny little channel in the device can get sort of trapped in the defects, which can then impede the flow of other electrons, leading to a reduction in the current flow delivered by the device,” he said. 

In order to reap the benefits the new materials provide in terms of performance, engineers need to know more about their limitations and the physics that causes them to degrade in harsh environments. In the case of gallium nitride-based transistors, the degrading processes are highly variable, dynamic in nature and sometimes happening in extremely fast times. For example, electrons can change direction and energy of motion in as little as a “femtosecond,” or 1 quadrillionth of a second. 

“Capturing such super-fast and stochastic electronic processes experimentally is quite challenging,” Ahmed said. 

To compensate, Ahmed’s lab will turn to computer simulations, developing thousands of lines of new computer code to be run on the world’s fastest supercomputers. Doing so will allow him to study the creation and distribution of atomic defects and emulate the transport and interactions of electrons that lead to permanent degradation in such nanoscale devices. 

“The physics of degradation is not well understood for these devices,” Ahmed said. “The aim of our project is to develop a better understanding of these degradation processes and mechanisms, from a fundamental, atomistic point of view. That will help engineers and scientists boost the performance of these devices and predict how long they will last with improved accuracy.”