A team composed of researchers from The Frontier Research Laboratory at the Samsung Advanced Institute of Technology (Yongin-si Gyeonggi-do, South Korea) and the Department of Materials Science and Engineering, Seoul National University (Seoul, South Korea) have reported an apparent breakthrough in LED technology that may allow production of devices on ordinary glass. This, in turn, may enable a reduction in the cost to produce LED based displays as well as the ability to produce very large sized LED devices.
Until now, LEDs have typically been fabricated on sapphire substrates or on silicon wafers. Since both approaches have limitations, the idea of fabricating LEDs on glass substrates has great appeal. To this point, the researchers report success in fabricating nearly single crystalline Gallium Nitride (GaN) on amorphous glass substrates.
According to the report "The new process involves first laying down a bed of titanium metal on the glass to serve as a base template to help direct the growth of the GaN. Next, a very thin film of GaN (just a starter bit grown at a low temperature) is applied on top of the titanium metal. This will be the useful layer at the end of the process. After that, a sheet of silicon dioxide is applied over the GaN; it has very small holes in it that serve to direct how the crystals will grow as they come up through it. Rather like very tiny molds. The whole works is then subjected to very high temperatures to promote the crystal growth of the GaN. After that, the GaN can be processed using the same techniques that are used now with crystals grown on a sapphire or silicon."
The area-type electroluminescent emission was found to be reliable, stable and produce a luminance of 600 cd/m2. The emission was observed to be quite uniform at different locations on the substrate. The spectra, however, were much broader than for comparable single crystal devices due to the peak wavelength varying across the facets of the pyramidal shaped crystals.
The researchers stated that "To the best of our knowledge, this is the first demonstration of such electroluminescence emission from GaN grown on glass."
To put the accomplishment of the new process into context, the largest size GaN LEDs available today are on the order of 2-inches. The new technology can produce GaN LEDs up to 400 times larger.
The fabrication process developed by the researchers utilizes standard materials and processes and appears to be straightforward and uncomplicated. On the other hand, comments in the press attributed to industry experts suggest that the process is also "time consuming, cumbersome, and because of the multiple steps required, too expensive to be used in a production type environment."
None-the-less, the team sees that "This method should provide a new and attractive tool for realizing ideal high-performance electroluminescence devices that demonstrate both low cost and high device performance, as well as scalability to large sizes."
The researchers see potential applications for the technology as including the production of pixels in large area inorganic LED televisions. GaN LED technology may also be utilized to produce large, cheap and efficient flat light sources.
The research discussed in this article was published in the October 9th on-line edition of Nature Photonics. A link to the site presenting part of the article and where the complete article can be purchased, can be found here.
Since the research is currently at the proof-of-concept stage, many improvements in the technology should still be possible. The researchers specifically note the potential of reducing leakage currents through further optimization. Current speculation is that the technology may take another 10 years to reach a state of development sufficient for use in commercial applications.
At its current state of readiness, the technology is highly interesting. If the technology can achieve its full potential, the pay off could be huge. This is a technology very much worth watching. -Arthur Berman