Study of InGaN-Based Light-Emitting Diodes on a Roughened Backside GaN Substrate by a Chemical Wet-Etching Process

Abstract

The InGaN-based light-emitting diodes (LEDs) with a roughened backside on the N-face surface of GaN substrate were fabricated through a chemical wet-etching process to increase light-extraction efficiency. The stable crystallographic etching planes were formed as the GaN {10 (11) over bar} planes. When the near-ultraviolet and blue LED were operated as a forward current of 20 mA, the output power of LEDs was improved from 13.2 and 19.9 mW to 25.6 and 24.0 mW, respectively. The different enhanced ratio is attributed to the different transmittance as a function of wavelength is caused from hexagonal pyramid on N-face GaN substrate after wet-etching process

High efficiency and output power of near-ultraviolet light-emitting diodes grown on GaN substrate with back-side etching

“…Moreover, the vertical depths of pyramids were in the range of approximately 0.08-0.4 µm. The related details can be found in [12]. Figure 4 shows RT EL spectra of these fabricated LEDs with 20 mA current injection.…”

N-face GaN substrate roughening for improved performance GaN-on-GaN LED

“…Roughening N-face (backside) of the GaN substrate has been widely demonstrated as a mean to enhance the LEE (Fu et al, 2011;Lin et al, 2009). In comparison to dry etching, wet etching is a more preferable technique for the substrate roughening because it is straightforward and can be done using a simple setup.…”

“…Based on published works by Fu et al (2011), Jeong et al (2015, Guo et al (2013), the light extraction of the LED can be increased further by increasing the density of hexagonal pyramids. By far, considerable attempts have been done to increase the density, mostly, by controlling the etching temperature (Wang et al, 2013), etching time (Saifaddin et al, 2019;Hu et al, 2016) and concentration of etchant, in particular KOH (Jung et al, 2010).…”

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

“…In recent literatures, the bulk GaN light-emitting diodes has been attracted a great interest [18][19][20] for its high-performance and low droop at the high current densities. The enhancement of output power for bulk GaN-based LEDs by special chip shaping designs, 20 chemical wet-etching process, 21 and two-steps roughening method 22 have been reported. The relatively thick light-output window layer gets more chances to extract the guided mode confined in bulk GaN layer to free space.…”