Size-dependent UV-C communication performance of AlGaN micro-LEDs and LEDs

Optimal LED size is an important topic for high-speed UV-C wireless communication but still lacks sufficient investigation. In this work, we study the size effect of UV-C LEDs based on the entire communication system, including modulation bandwidth, channel attenuation, optical coupling between LED and lenses, and energy efficiency (EE) at optimal operating currents. The maximum data rates of the 60, 80, 100, 150, 200, and 300-mu m UV-C LED based systems are 2.64, 2.66, 2.65, 2.64, 2.35, and 2.18 Gbps, respectively, using discrete multitone modulation and bit-power loading method. The higher data rate communication over 2.6 Gbps of the systems with the UV-C LEDs smaller than 150 mu m can be attributed to larger optical modulation bandwidth, spectral efficiency (SE) and average signal-to-noise ratio (SNR) at optimal operating currents, e.g., the optical modulation bandwidth, SE, average SNR, and the ratio of average SNR to light output power of 60-mu m UV-C micro-LED based communication system are 1.10, 1.16, 1.11 and 4.25 times higher than those of the 300-mu m LED based communication system, respectively, demonstrating the advantage of smaller micro-LEDs in UV-C communication. Furthermore, the 60-mu m UV-C micro-LED based communication link can achieve a high EE of 7.88 Gbits/Joule, which is 3.16 times higher than that of the 300-mu m LED based system. Our work gives insights to the studies on the high-speed and high-efficiency UV-C communications.