Yasufumi Fujiwara, professor of Osaka University in Japan, has recently created a prototype red LED element by using gallium nitride (GaN) semiconductor. Though blue and green LED elements using GaN semiconductor have already been commercialized, this is the first time that a red LED element has been prototyped by using GaN semiconductor, Fujiwara said.

If red, green and blue LED elements can all be made by using GaN semiconductor, it is possible to form three primary (RGB) colors on the same substrate, realizing an LED display that has a smaller pixel size and a higher resolution.

Fujiwara has developed the red LED element by using GaN added with europium (Eu), a rare earth, in the emission layer. Some researchers have already added Eu to GaN and created red light, but they generate the red light by photoexcitation, using ion-implantation technique to add Eu, Fujiwara said.

At the same time, the research team led by Fujiwara succeeded in obtaining red light by current injection while adding Eu by MOCVD (metal organic chemical vapor deposition) method. The group claims they have developed the world's first red LED element in this respect.

The optical output of the prototype is 1.3μW with a drive current of 20mA and a drive voltage of 6V. Though the optical output is still low, Fujiwara believes that it is possible to further improve the output by optimizing the electrode structure and other features of the prototype.