Abstract
We report improvement of improvement effectiveness of the light extraction efficiency of 10 W operated InGaN-based vertical light-emitting diodes via n-GaN surface roughening, using a commercial photoresist (PR) developer as an etching solution, which was compared with a conventional KOH-based solution. With the conventional KOH-based solution for n-GaN surface roughening, although both the depth and density of the etch pyramid initially increased with etching time, the depth eventually decreased and the density also decreased gradually, resulting in degradation in improvement effectiveness of extraction efficiency. Using the commercial PR developer for etching, however, after an initial increase in both the depth of the etch pyramid and its density, the depth and density were maintained without degradation, confirming the improvement in improvement effectiveness of extraction efficiency as well as the improvement in run to run fabrication uniformity. This may be due that with developer the GaN surface is etched only along the dislocation and is not etched over the non-defect region even as etching time goes on.
Highlights
Light-emitting diodes (LEDs) have many advantages as light sources, such as high-energy efficiency, long lifetimes, small size, excellent color rendering, and coverage of the entire optical spectrum from infrared (IR) to ultraviolet (UV)
We report improvement of improvement effectiveness of the light extraction efficiency of 10 W operated InGaN-based vertical light-emitting diodes via n-GaN surface roughening, using a commercial photoresist (PR) developer as an etching solution, which was compared with a conventional KOH-based solution
The external quantum efficiency is defined as the ratio of the number of photons in free space to the number of electrons injected into the LED; the external quantum efficiency is equal to the product of the internal quantum efficiency and the extraction efficiency
Summary
Light-emitting diodes (LEDs) have many advantages as light sources, such as high-energy efficiency, long lifetimes, small size, excellent color rendering, and coverage of the entire optical spectrum from infrared (IR) to ultraviolet (UV). The internal quantum efficiency is defined as the ratio of the number of photons from the active region to the number of electrons injected into the LED. The surface roughening method is used to minimize the total internal reflection of the LED material through artificial roughening of the semiconductor’s surface This method is used widely due to its relatively simple fabrication process and improved extraction efficiency. A commercial PR developer was suggested to be used for n-GaN surface roughening, and showed the improvement of improvement effectiveness of the light extraction efficiency of 10 W operated InGaN-based vertical LEDs with it, in comparison with the conventional KOH-based solution, in addition to the improvement in run to run fabrication uniformity. The detail etching mechanisms of InGaN surface etching was provided to explain the enhanced effects with the PR developer
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