Thermally stable and highly reflective AgAl alloy for enhancing light extraction efficiency in GaN light-emitting diodes

The properties of a AgAl alloy reflector layer deposited on a p-GaN layer for use in high-efficiency GaN flip-chip light-emitting diodes (FCLEDs) were investigated. The AgAl layer showed good adhesion properties compared to a layer of Ag on p-GaN. In addition, no agglomeration was found, indicating that the AgAl layer is thermally stable due to the formation of oxidized Al on the surface and at the interface of the AgAl layer. The InGaN/GaN multiquantum well light-emitting diode with the annealed AgAl layer showed good I-V characteristic and an enhanced optical output power compared to that with an annealed Ag layer due to the high reflectivity (86.7% at 465 nm), smooth surface after annealing, and good Ohmic property of AgAl. These results clearly indicate that a AgAl layer on p-GaN constitutes a promising reflector and Ohmic scheme for achieving high-brightness FCLEDs. (c) 2006 American Institute of Physics.