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Optoelectronics/Displays??

GaN micro-rods on graphene make bendy LEDs

Posted: 25 Sep 2014 ?? ?Print Version ?Bookmark and Share

Keywords:LED? GaN? flexible? optical? micro-rods?

Graphene for substrates

Ultrathin graphene films consist of weakly bonded layers of hexagonally arranged carbon atoms held together by strong covalent bonds. This makes graphene an ideal substrate "because it provides the desired flexibility with excellent mechanical strengthand it's also chemically and physically stable at temperatures in excess of 1,000C," said Yi.

It's important to note that for the GaN micro-rod growth, the very stable and inactive surface of graphene offers a small number of nucleation sites for GaN growth, which would enhance three-dimensional island growth of GaN micro-rods on graphene.

To create the actual GaN microstructure LEDs on the graphene substrates, the team uses a catalyst-free metal-organic chemical vapor deposition (MOCVD) process they developed back in 2002.

"Among the technique's key criteria, it's necessary to maintain high crystallinity, control over doping, formation of heterostructures and quantum structures, and vertically aligned growth onto underlying substrates," Yi said.

When the team put the bendability and reliability of GaN micro-rod LEDs fabricated on graphene to the test, they found that "the resulting flexible LEDs showed intense electroluminescence (EL) and were reliablethere was no significant degradation in optical performance after 1,000 bending cycles," noted Kunook Chung, the article's lead author and a graduate student in SNU's Physics Department.

The achievement is believed to represent a tremendous breakthrough for next-generation electronics and optoelectronics devicesenabling the use of large-scale and low-cost manufacturing processes.

"By taking advantage of larger-sized graphene films, hybrid heterostructures can be used to fabricate various electronics and optoelectronics devices such as flexible and wearable LED displays for commercial use," said Yi.


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