Finding the Achilles' heel of GaN-based LEDs in harsh radiation environments
2014-12-08
(Press-News.org) Gallium nitride (GaN) based devices are attractive for harsh environment electronics because of their high chemical and the mechanical stability of GaN itself that has a higher atomic displacement energy than other semiconductor materials.
However, degradation mechanisms of GaN device under radiation environments is not clear mainly because devices consist of many different types of semiconductors, such as p-type and n-type layers in light emitting diode (LED), and each layer has different hardness to radiation.
Now, researchers at the Electronics-Inspired Interdisciplinary Research Institute (EIIRIS) and Department of Electrical and Electronic Information Engineering at Toyohashi University of Technology, and the Japan Atomic Energy Agency (JAEA) describe the physical mechanism of an observed increase in the resistance of p-type GaN irradiated with 380 keV protons compared with n-type GaN.
The GaN-based LED structure shown in Fig.1 was irradiated with protons and the resulting electrical properties measured. Notably, the electrodes to measure the resistance of the p-type and n-type layers were produced independently using the clean room facilities at EIIRIS and the ion implanter in JAEA.
The two terminal resistance of the n-type GaN did not vary from its initial value after 1x1014 cm-2 proton irradiation, and remained of the same order after 1x1015 cm-2 protons. However, a clear increase of the resistance was found in the p-type GaN after 1x1014 cm-2 irradiation. The resistance increased further by six orders of magnitude after 1x1015 cm-2.
The observed increase of the resistance in p-type GaN is explained as being due to the lower initial carrier density than in n-type GaN due to a lack of efficient p-type doping technology for GaN, which is a key for the realization of novel devices operable in harsh environments.
INFORMATION:
Reference:
Authors: Hiroshi Okada, Yuki Okada, Hiroto Sekiguchi, Akihiro Wakahara, Shin-ichiro Sato, and Takeshi Ohshima.
Title of original paper: Study of Proton Irradaition Effects on p- and n-Type GaN Based-on Two-Terminal Resistance Dependence on 380 keV Proton Fluence.
Journal, volume, pages and year: IEICE Transactions on Electronics E97-C, 409 (2014).
Digital Object Identifier (DOI): 10.1587/transele.E97.C.409
Affiliations: Electronics-Inspired Interdisciplinary Research Institute (EIIRIS), and Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, and Japan Atomic Energy Agency (JAEA)
Department website: http://www.eiiris.tut.ac.jp
This article is featured in the December 2014 issue of the Toyohashi Tech e-Newsletter:
http://www.tut.ac.jp/english/newsletter/research_highlights/research03.html
[Attachments] See images for this press release:
ELSE PRESS RELEASES FROM THIS DATE:
2014-12-08
Macrophages are best known for their Pac Man-like ability to gobble up cellular debris and pathogens in order to thwart infection. A new study in The Journal of Cell Biology describes how these immune cells also help resolve inflammation by inducing white blood cells called neutrophils to leave wounded tissue.
Neutrophils are "first responders" that are attracted to wounds by signaling molecules called reactive oxygen species (ROS) that activate a protein kinase. When neutrophils finish their work, inflammation is partly resolved through apoptosis, or cell suicide, and ...
2014-12-08
What does it mean for expectant mothers and hospitals when there are large-scale closures of maternity units? A new study led by researchers at The Children's Hospital of Philadelphia provides an inside view from hospital staff members in Philadelphia, where 13 out of 19 obstetric units closed in a 15-year period.
The researchers found that sharp surges in patient volume in the remaining units strained the healthcare system, eroded workforce morale, and fragmented care for mothers and babies until hospitals adjusted to added demands.
"While the degree of obstetric ...
2014-12-08
WASHINGTON, DC (December 8, 2014)-- Despite the promise of health reform, millions of U.S. children still lack quality health coverage or have trouble getting the services they need to stay healthy or to develop properly, according to two articles published in the December issue of Health Affairs. To address these gaps in coverage, broad reforms aimed at improving the quality of coverage for all children are needed, according to the authors.
In the first article, Sara Rosenbaum, JD, the Harold and Jane Hirsh Professor of Health Law and Policy at Milken Institute School ...
2014-12-08
WASHINGTON, DC - December 9, 2014 - Seasonal flu vaccines may protect individuals not only against the strains of flu they contain but also against many additional types, according to a study published this week in mBio®, the online open-access journal of the American Society for Microbiology.
The work, directed by researchers at St. Jude Children's Research Hospital in Memphis, Tenn., found that some study participants who reported receiving flu vaccines had a strong immune response not only against the seasonal H3N2 flu strain from 2010, when blood samples were ...
2014-12-08
San Francisco children living in non-redeveloped public housing are 39 percent more likely to repeatedly visit emergency rooms, according to new research from UC San Francisco and UC Berkeley.
"The average emergency department (ED) visit costs two to five times more than an office visit, and many children visit EDs for potentially preventable reasons," said Nancy Adler, PhD, senior author of the research, and vice chair of the department of psychiatry and director of the Center for Health and Community at UCSF. "There is a clear need to better understand the range of ...
2014-12-08
(SALT LAKE CITY)- It's a virus that has long been characterized as dangerous and even deadly, but new research shows infant deaths from respiratory syncytial virus (RSV) are actually quite uncommon in the 21st century.
Researchers at the University of Utah have shown there are approximately 42 deaths annually associated with RSV in the United States, and of those deaths, the majority are in infants and young children that have complex preexisting chronic conditions.
"The news is very good for parents and their babies," says Carrie Byington, M.D., professor of pediatrics ...
2014-12-08
Two-dimensional (2D) layered materials are now attracting a lot of interest due to their unique optoelectronic properties at atomic thicknesses. Among them, graphene has been mostly investigated, but the zero-gap nature of graphene limits its practical applications. Therefore, 2D layered materials with intrinsic band gaps such as MoS2, MoSe2, and MoTe2 are of interest as promising candidates for ultrathin and high-performance optoelectronic devices.
Here, Pil Ju Ko and colleagues at Toyohashi University of Technology, Japan have fabricated back-gated field-effect phototransistors ...
2014-12-08
Physical activity increases oxidative stress, and therefore, as an antioxidant vitamin C might have particularly evident effects on people who are participating in vigorous exercise. In several studies, vitamin C administration attenuated the increases in oxidative stress markers caused by exercise. Furthermore, vitamin C is involved in the metabolism of histamine, prostaglandins, and cysteinyl leukotrienes, all of which appear to be mediators in the pathogenesis of exercise-induced bronchoconstriction.
A meta-analysis of three studies found that vitamin C halved post-exercise ...
2014-12-08
A new analysis of an important trial of the blood pressure-lowering procedure, renal denervation, shows that the main results may have been affected by a number of confounding factors that partially explain the unexpected blood pressure responses in patients.
The analysis, published in the European Heart Journal [1], identified factors in the SYMPLICITY HTN-3 trial, such as variations in the way the procedure was performed and changes in patients' medications and drug adherence, which may have had a significant impact on the results.
Results of the SYMPLICITY HTN-3 ...
2014-12-08
An international research team that includes researchers from Lawrence Livermore National Laboratory has captured the highest-resolution protein snapshots ever taken with an X-ray laser, revealing how a key protein in a photosynthetic bacterium changes shape when hit by light.
Human biology is a massive collection of chemical reactions and all involve proteins, known as the molecules of life. Scientists have been moving steadily toward their ultimate goal of following these life-essential reactions step by step in real time, at the scale of atoms and electrons.
"These ...
LAST 30 PRESS RELEASES:
[Press-News.org] Finding the Achilles' heel of GaN-based LEDs in harsh radiation environments
