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A high-power GaN-based light-emitting diode (LED) with an inductively coupled plasma (ICP)-transferred nanohemispherical hybrid backside reflector is studied. A self-assembled 100 ± 5 nm SiO2 nanosphere monolayer is drop-coated on the backside of a sapphire substrate as a mask to transfer nanohemispherical patterns onto the backside of the sapphire substrate by ICP. Nanohemispherical patterns could be transferred to the deposited backside reflector. Thus, reflected photons could be redirected and scattered into arbitrary directions for light extraction. As compared with a conventional LED without a backside reflector, at 350 mA, the studied device exhibits a 118.2% enhancement in light output power without the degradation of electrical properties. Note that the adhesion between an ICP-transferred sapphire substrate and the hybrid backside reflector is better than when directly inserting an SiO2 nanosphere monolayer in the device. Thus, the process yield could be enhanced for applying in the solid-state lighting.

Enhanced light extraction efficiency (LEE) of high-power GaN-based light-emitting diodes (LEDs) is achieved by inserting a self-assembled SiO2 nanosphere monolayer between the substrate and backside reflectors. Due to the presence of concave surfaces and photonic crystal-like air voids, downward photons emitted from multiple quantum well toward 3-D backside reflectors, could be reflected, scattered, and redirected into arbitrary directions for light extraction. These textured 3-D backside reflectors with an SiO2 nanosphere monolayer could also extract the lateral light inside device into the normal direction and improve LEE. As compared with a conventional LED without a backside reflector and an LED with a planar hybrid backside reflector, at 350 mA, the studied device with a 3-D hybrid backside reflector exhibits 136.4% (165%) and 23.6% (27.4%) enhancements in light output power (luminous flux) without the degradation of electrical properties. Higher light intensities in light emission mapping image and far-field pattern are also obtained. These results show that a textured 3-D backside reflector could be easily formed by inserting an SiO2 nanosphere monolayer to significantly enhance the performance of high-power GaN-based LEDs.

An interesting approach to improving the light extraction efficiency of high-power GaN-based light-emitting diodes (LEDs) by the use of a 3-D-photonic crystal (3-D-PhC) backside reflector is studied. A 3-D-PhC backside reflector is formed by coating a self-assembled SiO2 nanosphere monolayer between the hybrid reflector and backside of a sapphire substrate. The 3-D-PhC structure is used to enhance light scattering. At 350 mA, as compared with a conventional LED (with a hybrid reflector while only without the 3-D-PhC structure), the studied device exhibits 23.6% enhancement in the light output power without the degradation of electrical properties. Therefore, the performance of high-power GaN-based LEDs could be further improved by using a 3-D-PhC backside reflector.