Design and simulation in GaN based light emitting diodes using focused ion beam generated photonic crystals

Two-dimensional photonic crystal (2D-PC) structures have been designed to increase the light extraction in GaN based semiconductor light-emitting devices (LED). The photonic crystals could be fabricated using the focused ion beam (FIB) in a dual-beam nanotechnology workstation system SMI 3050, both with and without platinum coating. The acceleration voltage of the Ga ion beam was fixed at 30 kV and the ion beam current was 6 nA. The LED area was 155 µm × 85 µm with both top and bottom pads. In addition, we developed Bandsolve simulation tools for the photonic crystal band structures, and the simulation results supported our experimental observations. It was based on the advanced implementation of the plane-wave expansion technique for periodic structures. The radius was varied from 0.05 µm to 0.5 µm and the period was from 0.1 µm to 1 µm. Both square lattice array and hexagonal lattice array patterns have been investigated. It showed the highest monitor intensity for the sample that has a hexagonal array structure, with 0.45 µm in radius and 0.9 µm in period. The optimized parameters would be used as design guides to fabricate 2D-PC air hole arrays on the p-GaN surface for LED structures.