Light Extraction Enhancement of GaN-Based Light-Emitting Diodes With Textured Sidewalls and ICP-Transferred Nanohemispherical Backside Reflector

Textured-sidewall GaN-based light-emitting diodes (LEDs) with convex and 45° patterns and an inductively coupled plasma (ICP)-transferred nanohemispherical backside reflector, formed using an ICP etching process, are fabricated and studied. For devices with textured sidewalls, the scattering probability of photons at the GaN/air interface is increased and the light extraction efficiency is enhanced since photons are allowed to find escape cones in the horizontal direction. With the ICP-transferred nanohemispherical backside reflector, reflected photons can be easily scattered and redirected in arbitrary directions for light extraction and thus have more opportunities to escape the devices. The LED with 45° sidewalls and a backside reflector exhibited the significant improvements of 55.8%, 49.3%, 47.2%, and 55.4% in light output power, luminous flux, external quantum efficiency, and wall-plug efficiency, respectively, compared to those of a conventional LED without these specific designs (Device A). In addition, the higher intensities in a light emission mapping image and improved far-field patterns are obtained for the studied device. The enhanced optical performance is mainly attributed to the increased light extraction in all directions due to a significant reduction in the total internal reflection by the textured sidewalls and a backside reflector. Therefore, textured-sidewall structures and an ICP-transferred nanohemispherical backside reflector are promising for high-power GaN-based LED applications.