Abstract
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.
Highlights
As the lighting industry continues to advance, the light emitting diode (LED) market share is increasing explosively
Double-side patterns were formed on a sapphire substrate in order to create high efficiency LEDs
We simulated patterned sapphire substrate (PSS)-LED devices using a ray tracing method based on the Monte Carlo Method
Summary
As the lighting industry continues to advance, the light emitting diode (LED) market share is increasing explosively. In order to develop low cost, high intensity LEDs for lighting, more studies regarding luminous efficiency improvement and heat dissipation system development are needed.[1,2]. The patterned sapphire substrate (PSS) method has been reported to improve light extraction efficiency and increase the internal light efficiency through a low dislocation effect when growing an epitaxial layer growth on the top of the sapphire substrate.[3,4,5,6] these studies are mostly based on lab experiments that are used to show if the efficiency is increased compared to the existing LEDs, which means the quantitative results are somewhat lacking. There have been studies that quantitatively analyze the improvement of light extraction efficiency through a PSS design in order to develop low cost high intensity LEDs.[1,2,7]. The designed pattern was applied using a nano imprint lithography (NIL) method to create the pattern on the sapphire substrate used to fabricate and evaluate the actual LED sample
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