A specific hybrid structure, including 45° sidewalls, a shallower (0.25 μm in depth) microhole array, and a 3-D like backside reflector, is used to fabricate GaN-based light-emitting diodes (LEDs). The 3-D like backside reflector is formed by the deposition of 100 nm-diameter SiO2 nanospheres (NSs) and an Al layer on the sapphire substrate. Based on the use of 45° sidewall and microhole array, the reduced total internal reflection (TIR) and Fresnel reflection and the increased scattering probability and the opportunity of photons to find escape cones can be expected. In addition, the use of 3-D like backside reflector can effectively reflect scatter, and redirect the downward photons emitted from multiple quantum well (MQW) region into arbitrary directions. Thus, the light extraction performance can be substantially improved. In experiment, under an injection current of 400 mA, the studied Device D with this hybrid structure shows enhancements of 47.4%, 47.7%, 33.1%, and 47.8% in light output power (LOP), external quantum efficiency (EQE), luminous flux, and wall-plug efficiency (WPE), respectively, as compared to a conventional LED. Moreover, the related electrical properties are not degraded for the studied Device D. Therefore, this hybrid structure shows a promise for high-performance GaN-based LED applications.
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