Enhancement of InGaN-Based vertical LED with concavely patterned surface using patterned sapphire substrate

To improve the external quantum efficiency, we have proposed a new method utilizing surface roughening of vertical-type light-emitting diodes (VT-LEDs) fabricated on hemispherical patterned sapphire substrate by using a laser lift-off technique. The advantages of this method are simple and reproducible in transferring the well-defined patterns on sapphire into GaN layer. The VT-LED with concavely patterned surface showed a nearly twofold increase in the output power compared to the normal planar surface. This improvement in the VT-LED performances is attributed to the increase in the escaping probability of photons from the LED surface.