High-efficiency 1-mm² AlGaInP LEDs sandwiched by ITO omni-directional reflector and current-spreading layer

A 1-mm² AlGaInP light-emitting diode (LED) sandwiched by an omni-directional reflector (ODR) and current- spreading layer is presented. The vertical-conducting bottom ODR consists of p-GaP, dispersive dot-contacts of Au-AuBe-Au acting as ohmic contacts, an intermediate low-refractive index layer of indium-tin-oxide, and a silver layer. A Si substrate, which acted as a heat sink, was bonded to the ODR-covered LED structure using a metal-to-metal bonding process. It was found that the maximum output power of the ODR-LED on Si reached 304 mW at 650 mA, and the output power did not saturate up to 650-mA injection current. The external quantum efficiency of 31.8% was obtained at 100 mA, and 19.4% achieved even at currents of up to 800 mA. Furthermore, under a forward current of 350 mA, the ODR-LEDs remained highly reliable after 1000-h testing at room temperature.