Osaka Univ. GaN red LED

Yasufumi Fujiwara, professor at the Division of Materials and Manufacturing Science, the Graduate School of Engineering, Osaka University, prototyped a 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 it, Fujiwara said.

When red, green and blue LED elements are 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.

This time, the red LED element was developed 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.

On the other hand, the research group 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 small, Fujiwara considers that it is possible to further enhance the output by optimizing the electrode structure and other features of the LED element.