Sputtering method reduces GaN LED prod'n cost
Researchers from the University of Tokyo have developed a technology for creating GaN LEDs on glass substrate that could not only reduce manufacturing costs but could also help to develop OLED light panels. They used a sputtering method to transcribe the GaN LEDs onto the glass substrate. The team has not yet measured luminous efficiency or external quantum efficiency for any single colour but are in the process of testing the efficiency of the internal quantum at low temperatures.
InGaN-based light-emitting diodes (LEDs) have been widely accepted as highly efficient light sources capable of replacing incandescent bulbs but applications of InGaN LEDs are limited to small devices because their fabrication process involves expensive epitaxial growth of InGaN by metalorganic vapour phase epitaxy on single-crystal wafers.
The researchers have used a low-cost epitaxial growth process, such as sputtering on large-area substrates, to fabricate large-area InGaN light-emitting displays.
By using multilayer graphene buffer layers, the growth of highly c-axis-oriented GaN films even on amorphous substrates was feasible. The research team fabricated red, green and blue InGaN LEDs and confirmed their successful operation.
The researchers believe that by demonstrating that full-colour LEDs can be fabricated on amorphous substrates and sputtering is frequently used in the LCD industry so a process could be adapted to fabricate large-area inorganic LED displays on glass substrates.
The researchers point out that modern technology in the glass industry can offer roll-to-roll processing of flexible glass foils and a combination of these techniques can lead to the development of large-area flexible inorganic devices.
- Paul Buckley
EE Times Europe