GUANGZHOU, China, June 14, 2012 — Gallium nitride (GaN) LEDs grown on a layer of silicon were successfully transferred to a layer of copper, enhancing efficiency by 122 percent, say Chinese researchers.
The new copper substrate from Sun Yat-sen University enabled the GaN crystals to release some of the internal stresses generated when they originally formed. This relaxation helped minimize a significant problem for LEDs that reduces their efficiency, known as the quantum confined Stark effect. In comparison with the light output of LEDs on silicon substrates, light output of LEDs on copper was enhanced by 122 percent.
The relocation of the LEDs produced no obvious deterioration in the light emitting-region, or multiple quantum wells, of the crystals.
The researchers attributed the improved efficiency to the removal of the absorptive substrate; the insertion of a metal reflector between the LEDs' structure and the copper submount; the elimination of electrode shading, which also reduces efficiency; and to the rough surface of the exposed buffer layer, which improves crystal orientation on the substrate.
The results were reported in Applied Physics Letters
For more information, visit: eng.sysu.edu.cn/