Thermally Stable Mirror Structures for Vertical-Conducting GaN/Mirror/Si Light-Emitting Diodes

Vertical-conducting GaN/mirror/Si light-emitting diodes (LEDs) with thermally stable mirrors have been fabricated using a combination of wafer-bonding and laser liftoff techniques. The thermal stabilities of NiO-Ag, NiO-Ag-Ni, and NiO-Au-Ag mirrors and their effects on the performance of mirror-substrate LEDs were studied. It is found that the NiO-Ag-Ni mirror presents the best performance, where the specific contact resistance and the reflectivity can achieve 5.1times10^-3 Omega-cm² and 92% at 470 nm after oxidation annealing at 500degC for 10 min. The top Ni layer could protect the Ag mirror from clustering during the thermal treatment process. The output powers of the GaN-sapphire and GaN/mirror/Si LEDs with NiO-Au-Ag and NiO-Ag-Ni mirrors show 4.5, 4.3, and 13 mW, respectively.