The research office of Professor Fujioka Yogi of the University of Tokyo announced on June 23, 2014 that it has developed a technique for forming a GaN-based LED by sputtering on a glass substrate. In addition to significantly reducing manufacturing costs compared to existing LEDs, it is also possible to implement large-area light-emitting elements such as organic ELs using inorganic LEDs.
Prof. Fujioka's laboratory transferred a graphene multilayer film on a glass substrate of about 2 inches (about 5 cm in diameter), and then formed AlN and n-type GaN on the graphene multilayer film by pulse sputtering. A quantum well or p-type GaN crystal composed of a multilayer structure of GaN and InGaN.
Fujioka said that the technology for making LEDs by sputtering has been developed long ago. "The details of these technologies have not been released, but the experience is accumulated." This technique can be said that a GaN crystal is formed by sputtering on a graphene sheet which is the thinnest graphite sheet, and it is confirmed that actual light can be emitted. LEDs that emit light in three primary colors of red (R), green (G), and blue (B) were produced.
At present, it is impossible to detect the luminous efficiency of white light emission and the external quantum efficiency in a single color state, and the internal quantum efficiency under extremely low temperature conditions is being evaluated. Professor Fujioka said, "The internal quantum efficiency is as low as a few percent compared to LEDs made on sapphire substrates." The future issue is how to increase the internal quantum efficiency to a level comparable to existing LEDs.
Prof. Fujioka's laboratory transferred a graphene multilayer film on a glass substrate of about 2 inches (about 5 cm in diameter), and then formed AlN and n-type GaN on the graphene multilayer film by pulse sputtering. A quantum well or p-type GaN crystal composed of a multilayer structure of GaN and InGaN.
Fujioka said that the technology for making LEDs by sputtering has been developed long ago. "The details of these technologies have not been released, but the experience is accumulated." This technique can be said that a GaN crystal is formed by sputtering on a graphene sheet which is the thinnest graphite sheet, and it is confirmed that actual light can be emitted. LEDs that emit light in three primary colors of red (R), green (G), and blue (B) were produced.
At present, it is impossible to detect the luminous efficiency of white light emission and the external quantum efficiency in a single color state, and the internal quantum efficiency under extremely low temperature conditions is being evaluated. Professor Fujioka said, "The internal quantum efficiency is as low as a few percent compared to LEDs made on sapphire substrates." The future issue is how to increase the internal quantum efficiency to a level comparable to existing LEDs.
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