June 12, 2013, by Graham Kendall
I am Blue
This post was contributed by Professor Ian Harrison
I’m feeling Blue
Look around, blue is everywhere from decorative lights on cars and computer cases to blue ray DVDs that allow you watch the latest hollywood blockbuster in hi-definition. Ever wondered about the material and devices behind the technology and what the economic drivers were? The story behind the major technological advance could have come from greek tragedy or a Hollywood blockbuster.
Normal tungsten lamps are notorious inefficient with only a small fraction of the input energy being converted into light. The majority of the energy is transferred into heat and this explains why a traditional light bulb gets very hot. On the other hand LEDs are much more efficient. They are “solid state” devices using semiconductors to emit light rather than piece of hot tungsten. Red LEDs have been around since the late 60s and other colours like yellow came relatively quickly but efficient green and blue lights did not because of material restrictions.
The basic building building block of solid state lighting is the light emitting diode or LED for short. These devices emit light when current flows through them and the colour depends on the material. The semiconductor Gallium Nitride was known in the 60s to have the appropriate characteristics to make a blue LEDs and so was widely investigated but technological problems with controlling the impurities prevented the manufacture of the pure material from which to make the device and consequently interest in the material waned.
However, the search for Blue LEDs continued and that is where our story begins. Moving on 20 years to the early nineties, we start the fairy tale and enter stage left an unknown Japanese engineer, Nakamura, in an unknown Japanese company, Nichia. Nakamura persuades the Nichia board to give him millions of dollars to develop blue LEDs based on GaN using a relatively new technique called Molecular vapour phase deposition. The results of this research took the semiconductor industry by storm and allowed Nichia to secure a very strong patent for blue LEDS and LASERS which we now use in our blue-ray DVDs. In Hollywood, the story would end here; with Nakamura riding into the sunset hand in hand with Nichia and everyone living happy ever after. As usual Hollywood and real life differ, Nakamura left Nichia in 1999 to join UCSB for a chair sponsored by a rival company Cree followed by several years of litigation.
So what was Nottingham’s contribution to the GaN story? In the early years the impact of Nottingham’s Nitride Group, of which I was a member, was significant because our alternative technique for making GaN had the potential to break Nichia’s patent. It was really an exciting time to be involved in GaN research. I can still remember the anticipation at the Fall meeting of the Materials Research Society conferences in Boston when the latest GaN results would be announced; the gap between Nichia and the rest of the world narrowing and Nichia moving swiftly but surely to the profitable commercialization finishing line. Ultimately, technical problems with our growth technology prevented our material from being used in devices but that’s another story. Subsequently, the interests of the Nottingham group diverged; the physicists focused more on the material aspects and developed new materials based on Gallium Nitride whilst I and the other engineers attention focused on other devices and materials.
Header Image: Such Deep Blue Eyes: Dowvloaded from Google (13 Jun 2013, labeled as free to resue); Original can be seen at http://bit.ly/12Hdp4W