Wafer-scale surface roughening for enhanced light extraction of high power AlGaInP-based light-emitting diodes

Abstract

A new approach to surface roughening was established and optimized in this paper for enhancing the light extraction of high power AlGaInP-based LEDs, by combining ultraviolet (UV) assisted imprinting with dry etching techniques. In this approach, hexagonal arrays of cone-shaped etch pits are fabricated on the surface of LEDs, forming gradient effective-refractive-index that can mitigate the emission loss due to total internal reflection and therefore increase the light extraction efficiency. For comparison, wafer-scale FLAT-LEDs without any surface roughening, WET-LEDs with surface roughened by wet etching, and DRY-LEDs with surface roughened by varying the dry etching time of the AlGaInP layer, were fabricated and characterized. The average output power for wafer-scale FLAT-LEDs, WET-LEDs, and DRY3-LEDs (optimal) at 350 mA was found to be 102, 140, and 172 mW, respectively, and there was no noticeable electrical degradation with the WET-LEDs and DRY-LEDs. The light output was increased by 37.3% with wet etching, and 68.6% with dry etching surface roughening, respectively, without compromising the electrical performance of LEDs. A total number of 1600 LED chips were tested for each type of LEDs. The yield of chips with an optical output power of 120 mW and above was 0.3% (4 chips), 42.8% (684 chips), and 90.1% (1441 chips) for FLAT-LEDs, WET-LEDs, and DRY3-LEDs, respectively. The dry etching surface roughening approach developed here is potentially useful for the industrial mass production of wafer-scale high power LEDs.

Transparent conductor-embedding nanocones for selective emitters: optical and electrical improvements of Si solar cells

“…The angle formation seems to be uniform through the pyramids, however, the sizes are varied by each pyramid ( Fig. 1b ) due to the different etching rate along the (100) plane even in a same solution 39 . Hereafter, this sample is referred as a textured Si sample.…”

Enhanced Light Extraction of Infrared AlGaAs-Based LEDs With Micron Array

“…Micron-scale and nano-scale quasi-periodic structures, such as photonic crystal [5], [6], moth-eye structure [7]- [11], nanodome [12] and truncated cone [13]- [16] can be prepared by the dry etching. Among these structures, the nanostructure array is the state-of-the-art approach with many complex processing processes.…”

Area-Saving and High-Efficiency RGB LED Driver with Adaptive Driving Voltage and Energy-Saving Technique

“…Specifically, the internal quantum efficiency of LEDs has been extensively researched and improved in recent years. The internal quantum efficiency of InGaN LEDs has been improved by use of the large overlap quantum well concept [9][10][11], and the light extraction efficiency of LEDs has been improved by use of the surface roughening technique [12] and microsphere arrays [13,14].…”