High-Quality Distributed Bragg Reflectors for Resonant-Cavity Light-Emitting Diode Applications

Efficient distributed Bragg reflectors based on AlxGa1—xN/GaN multilayer stacks have been grown by plasma-assisted molecular-beam epitaxy on GaN/Al2O3 templates. The final goal is to incorporate these reflectors as bottom mirrors in a backside (sapphire) resonant-cavity light-emitting diode at 510 nm. The reflectors have been characterised by atomic force microscopy, high-resolution X-ray diffraction and high-resolution transmission electron microscopy. Reflectivity measurements have also been performed, obtaining values between 30% and 50%, depending on the Al content used. The incorporation of the AlxGa1—xN/GaN Bragg reflector as bottom mirror in a RCLED structure improves the output power by a factor of 12 compared with conventional light-emitting diodes.