Efficient GaN slab vertical light-emitting diode covered with a patterned high-index layer

We demonstrate the enhancement of light extraction from a wide-area (500×500μm2) GaN slab light-emitting diode (LED) that results from covering it with a TiO2-patterned layer. To fabricate this device, a Cu supporter is electroplated onto the p-GaN face followed by detaching the sapphire substrate with a laser lift-off process. At the standard current of 60mA, the wall-plug efficiency of the TiO2-patterned LED is ∼14.8%, i.e., the efficiency is enhanced by a factor of ∼1.8 over that of nonpatterned LEDs. Our three-dimensional finite-difference time-domain computations confirm that this output increases with the index of the patterned layer.