Experimental study of light output power for vertical GaN-based light-emitting diodes with various textured surface and thickness of GaN layer

Abstract

The light output power (LOP) of vertical-type GaN-based light emitting diodes (LED) with surface roughness (texture) can be changed by texture size, density, and thickness of GaN film or by the combined effects of texture formation and thickness of GaN film. We have investigated these changes experimentally and note that the enhancement of the LOP by a factor of 2.4 can be improved with optimum texturing parameters as compared to that without texturing. In addition, the LOP of GaN-based LEDs under the same texture density increase slightly as thickness of GaN film decreases. Base on these results, we have evidently demonstrated that the enhancement factors of LOP are related to the correlation between texture size (density) and thickness of GaN film.

GaAs pillar array-based light emitting diodes fabricated by metal-assisted chemical etching

“…23 The aforementioned RIE-based techniques are routinely employed in surface-texturing of III-V's for the enhancement of light output efficiency of light emitting diodes (LEDs). 31 Although LEDs may be engineered with internal quantum yields approaching unity, 32 the emission of light from a planar and high refractive index active region into free space is limited by a narrow escape cone and, therefore, prone to internal reflection and re-absorption. 32,33 As such, exterior designs such as truncated inverted pyramid geometries 34,35 are widely used for minimizing internal reflection in commercial LEDs.…”

Improved light extraction efficiency of GaN-based vertical LEDs using hierarchical micro/subwavelength structures

“…Previously, dry etched micropatterns, KOH wet etched for rough surface, and photochemical etching methods have been used to achieve improved light extraction, which in turn has resulted in significant increases in LEE in GaN-based VLEDs. [15][16][17][18][19][20][21][22] However, GaN-based VLEDs with HSs have not yet been reported despite their important functions. 6) In this paper, we present GaN-based VLEDs with biomimetic HSs; these GaN-based VLEDs consist of coneshaped MSs and tapered SWSs (nanotips), formed using the thermal reflow and self-masked dry etching (SMDE) processes, 23,24) respectively.…”

Fabrication of p‐pad‐up GaN‐based thin‐film light‐emitting diodes with electroplated metallic substrates

“…However, heat dissipation is a serious problem for conventional LEDs driven at high current density due to the poor thermal conductivity of the sapphire substrate [4]. To solve this problem, flip-chip and vertical-structure thin-film LEDs (TF-LEDs) with better heat dissipation and higher light extraction efficiency have been exploited [5][6][7]. Flip-chip LEDs are mounted on high thermal conductivity substrates, and light extraction efficiency is improved because there are no bonding pads or wires on top of these devices.…”