High Efficiency GaN Light-Emitting Diodes With Two Dimensional Photonic Crystal Structures of Deep-Hole Square Lattices

We report the enhanced light extraction of a square lattice photonic crystal GaN LED with a lattice constant of 460 nm and holes with a depth of 500 nm drilled through InGaN/GaN multiple quantum wells (MQWs) using laser holography and inductively coupled plasma reactive ion etching. In spite of the etching through the MQWs leading to undesirable surface recombination, the photonic crystal LEDs exhibited 1.37 times higher light extraction than that of the LEDs without photonic crystals at 20 mA. Theoretical studies using the 3-dimensional finite-difference time domain method show that the increase of the extraction efficiency with increasing etch depth is due to the increase of the density of the leaky modes into the air.