Abstract
The optical and electrical characteristics of InGaN‐based blue light‐emitting diodes (LEDs) grown on patterned sapphire substrates (PSSs) with different pattern heights and on planar sapphire by atmospheric‐pressure metal‐organic chemical vapor deposition were investigated. Compared with planar sapphire, it was found that the LED electroluminescence intensity is significantly enhanced on PSSs with pattern heights of 0.5 (21%), 1.1 (57%), 1.5 (81%), and 1.9 (91%) μm at an injected current of 20 mA. The increased light intensity exhibits the same trend in a TracePro simulation. In addition, it was also found that the level of leakage current depends on the density of V‐shape defects, which were measured by scanning electron microscopy.
Highlights
InGaN-based light-emitting diodes (LEDs) are useful for a wide range of visiblelight applications
The light output intensity showed remarkable improvement for pattern heights of 0.5, 1.1, 1.5, and 2.0 μm; the intensities for these heights were about 21, 57, 81, and 91% higher than for the LED on a normal planar sapphire substrate at an operating current of 20 mA
This paper evaluates the effect of different pattern heights on the light extraction efficiency of InGaN-based blue LEDs
Summary
InGaN-based light-emitting diodes (LEDs) are useful for a wide range of visiblelight applications. The critical angle is roughly 24.6◦, which indicates that less light is extracted from the surface [4] For this reason, several alternative approaches have been introduced to improve light extraction efficiency, including approaches that make use of p-GaN roughness [5], indium tin oxide (ITO) mesh [6], a laser liftoff process [7], and a patterned sapphire substrate (PSS) [8,9,10,11]. Defects that are related to the use of different pattern heights in the sapphire substrate, such as degraded electrical performance, have rarely been examined. We evaluated the leakage current and used SEM measurements to characterize its relationship to V-pit defects
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