Ion Beam Surface Modification of GaN Films for High Efficient Light Emitting Diodes

Abstract

Focused gallium (Ga) ion beam technology has been proposed to modify the surface of GaN thin lms. Due to the signicant advancement in nitride semiconductors, the solid-state light emitting diodes will gradually replace uorescent lamps in the next decade. However, further improvements in light extraction and power eciency are still highly desired. GaN is limited by its high refractive index, with low light escape cone angle at about 24.6• . The external quantum eciency is low due to the unwanted reection and absorption. As the patterning technology scales down to the nanometer level, photonic crystal lattice in the visible light wavelength range can be achieved. Therefore, we improved the external eciency by the new design of hexagonal photonic crystal lattice with air hole arrays in the diameter of 150 nm and the depth of 120 nm. The Ga beam was accelerated at 30 kV and the ion current was 100 pA. The plane wave expansion method along with the nite dierence time domain was useful to investigate the quantum connement. The nanopatterning by the focused ion beam could save time and processing step. In addition, we have successfully prepared blue InGaN/GaN samples with hexagonal period of 200 nm. The device micro-photoluminescence results have demonstrated that the peak illumination intensity was improved by 30%.