Improvement of Light Extraction From Patterned Polymer Encapsulated GaN-Based Flip-Chip Light-Emitting Diodes by Imprinting

Light extraction improvement of GaN-based light-emitting diodes using patterned undoped GaN bottom reflection gratings

“…Almost all of these methods are seeking to extract the trapped light in greater quantity and faster speed. Those methods being explored are placing photonic crystals or nanostructure grating on one of LED layers to modify the effective index of refraction at the boundary [6][7], randomized roughening on the surface of the device [7][8], slanted device configurations that result in pyramidal shapes [7], and inverted "flip-chip" designs that put the epitaxial side upwards or downwards [4] [9].…”

Enhanced Light Extraction Efficiency from GaN Light Emitting Diodes using Photonic Crystal Grating Structures

“…We produce the optimized structure and list the results in the Table 5.1. The best cases for single gratings from each grating type were taken from our previous studies [16,31], which also compare to and agree with experimental data provided by Peking University [9] [18]. Ref.…”

“…Instead of light reflecting at grating surfaces, the light instead scatters at these surfaces. A variety of methods, including wet etching with an amorphous sacrificial layer [6][7][8][9] or by laser etching to obtain a more periodic spacing [10][11][12][13][14], can etch a transmission grating on a semiconductor surface. In previous literature, the same patterning can also apply, with a similar effect, to an Ag reflector plate in either pillar or hole grating shapes to form a reflection grating [15][16].…”

“…It is also not practical to fabricate all the double grating cases to obtain the best cases. Even this thesis is only limited to one particular GaN LED structure developed by Peking University [9]; we simulate at least 181 cases based on the microstructure gratings and present very interesting results. In addition, etching also involves positional defects, and so the grating structure is not a perfectly periodic crystal.…”

“…Ref. [9] and [18] show the published experimental data on our simulated LED structure. Ref [9] only has electroluminescence (EL) data.…”