Improving Light-Emitting Diode Performance through Sapphire Substrate Double-Side Patterning

Here, we present a new double-side patterned sapphire substrate methodology that improves the efficiency of gallium nitride-light emitting diodes (GaN-LEDs). The light extraction efficiency of GaN-based LEDs was analyzed through the use of a ray-tracing simulation. The extraction efficiency was simulated using patterned sapphire substrate LEDs with a variety of shapes, depths, sizes, and spacing. Through the optimal patterning of the various factors, high extraction efficiency was realized and subsequently improved upon. The thermal LED characteristics were analyzed through the use of the COMSOL general heat transfer module. The LEDs patterned on the sapphire substrate were fabricated using nano imprint lithography. We found that the output power of the double-side patterned LED was 52% greater than that of a flat LED. The thermal resistance of the double side patterned LED was 9.5  K/W less than that found for the flat LED.

As the lighting industry continues to advance, the light emitting diode (LED) market share is increasing explosively. The biggest reason for this growth is that LEDs are more energy efficient and have a longer life compared with conventional light sources. The era of full-scale LED applications has arrived as blue and white gallium nitride (GaN) semiconductor based LEDs are commercialized. The LEDs offer the benefits of fast processing speed of a semiconductor and low electricity consumption. As such, they have been accepted into the strategic national product for green growth. The development of the blue GaN LED in the mid-1990s enabled the full-color LED displays that have become a common feature in our daily lives. The high intensity LED market is expanding too fast to measure; efforts to enlarge the chips, improve their luminous efficiency, and the enhancement of their heat dissipation technology support are actively ongoing. However, LEDs have their own problems. The biggest problem is that LED prices are 20 times more expensive than conventional lighting; this is a big burden for their use in households and offices. In order to develop low cost, high intensity LEDs for lighting, more studies regarding luminous efficiency improvement and heat dissipation system development are needed.


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