SU-8 planarized InGaN light-emitting diodes with multipixel emission geometry for visible light communications

The potential for visible light communications with SU-8 planarized InGaN light-emitting diodes (LEDs) is investigated experimentally. For large-size LEDs, current crowding occurring near the n-contact is addressed by shrinking the dimensions of the emitters/pixels, along with the use of parallel-connected schemes to achieve multipixel emissions. Through improved heat dissipation, current uniformity, and light extraction efficiency, the resulting LED matrices fabricated with 6 × 6 pixels outperform conventional LEDs in terms of light output power and current-induced spectral shift. It was also found that good control of the SU-8 planarization process and optimizing the number of pixels facilitates the fabrication of high-efficiency LED matrices. In addition, the presence of large junction capacitance caused by the parallel connection of the individual pixels prevents these LED matrices with 6 × 6 pixels from operating at high speed. After eliminating the slow-responding phosphorescent components emitting from the phosphor-converted white LEDs, an open eye diagram at 80 Mb/s is demonstrated over a distance of 100 cm in directed line-of-sight optical links.