Light-output enhancement in a nitride-based light-emitting diode with 22° undercut sidewalls

Abstract

We successfully fabricated nitride-based light-emitting diodes (LEDs) with 22 undercut sidewalls. The 22 etching undercut sidewalls were achieved by controllable inductively coupled plasma reactive ion etching. With a 20-mA current injection, the output powers of the LED with 22 undercut sidewalls and standard LED were 5.1 and 3 mW, respectively-a factor of 1.7 times enhancement. It was found that such undercut sidewalls could enhance the probability of escaping the photons outside from the LED in the near horizontal and in-plane directions. This simple and controllable method is beneficial to fabricate brighter LEDs.Index Terms-Etching profile, GaN, light-emitting diode (LED), light extraction efficiency.

Shape designing for light extraction enhancement bulk-GaN light-emitting diodes

“…The chip dimension was 1000 Â 1000 lm 2 with the thickness of 350 lm matched with experiment samples. The refractive indices and absorption coefficients of the (In)GaN layers, 11,[13][14][15]26,27 and bulk GaN substrates 18,20 were taken into account. The details of structure parameters for the bulk-GaN LEDs are shown in Table I.…”

“…1 To alleviate these issues, many solutions have been developed, such as ZnO-Nanowire Array, 2 photonics crystal structures, 3 grade-refractive-index, [4][5][6] and surface plasmons. [7][8][9] Geometrical chip shaping [10][11][12][13] was another approach to increase the light extraction efficiency. LED structures with circular, 14 Lozenge, 15 and triangular 16 shaped have also been proposed.…”

InGaN light-emitting diodes with indium-tin-oxide photonic crystal current-spreading layer

“…1 However, due to the large refractive contrast at the nitride-air interface, the majority of light emitted from the MQWs is totally internally reflected, resulting in low EQE. 2 Numerous approaches have been adopted to efficiently extract light from devices and prevent unwanted guiding modes, such as geometrical shaping, 3 micro-LEDs, 4 and surface roughening. 5 These methods rely on the formation of non-parallel surfaces to minimize reflections, albeit at different dimensional scales.…”

High Extraction Efficiency of GaN-Based Vertical-Injection Light-Emitting Diodes Using Distinctive Indium–Tin-Oxide Nanorod by Glancing-Angle Deposition

“…1) To increase the luminous efficiency of LEDs, it is necessary to improve the external quantum efficiency, which is defined as the product of the internal quantum efficiency and extraction efficiency. Several methods, including the use of surface roughening techniques, [2][3][4][5] inclined side-wall etching, 6,7) patterned sapphire substrates, 8,9) and highly reflective omnidirectional reflectors (ODRs), 10) have shown improved light extraction efficiencies. Surface roughening is one of the most efficient methods to provide large enhancement for the extraction efficiency owing to the random scattering factors on the roughened surfaces.…”