Multigigabit Visible Light Communication Based on High-Bandwidth InGaN Quantum Dot Green Micro-LED

Long-wavelength light-emitting diode (LED) devices in the visible band (>492 nm) and their applications in high-speed visible light communication (VLC) have attracted tremendous research interest recently. The electrical-to-optical (E-O) bandwidth of conventional c-plane long-wavelength LEDs is limited by carrier lifetime in InGaN quantum well (QW), which is a fundamental problem limiting the data rate of high-speed VLC systems. In order to achieve an over GHz E-O bandwidth for applicable packaged LEDs, it is necessary to innovate from the material level in the active region. This work aims to break through the modulation bandwidth bottleneck of VLC systems based on green micro-LED. Commercial LEDs suffer a very limited E-O bandwidth due to their long radiative recombination carrier lifetime and large resistance-capacitance delay. Herein, by the utilization of green InGaN quantum dots (QDs) as the active region of micro-LED, this constraint can be remarkably alleviated. Green micro-LEDs containing five layers of InGaN QDs are fabricated, packaged, and then applied in a line-of-sight (LOS) VLC system over a 2 m free-space channel. The VLC system based on a single-pixel 50 and 75-μm diameter green micro-LEDs can achieve high modulation bandwidths up to 1.22 and 1.14 GHz, respectively. Then, real-time non-return-to-zero on–off keying (NRZ-OOK) and offline pulse-amplitude modulation four-level (PAM-4) as two common schemes in short-distance optical communication are adopted to evaluate the VLC system performances. A real-time 2.1 Gbps NRZ-OOK and an offline 5 Gbps PAM-4 VLC links are achieved with BERs of 2.74 × 10–3 and 1.88 × 10–3 above the forward error correction (FEC) criterion of 3.8 × 10–3, respectively. To the best of our knowledge, this is the highest-recorded modulation bandwidth and communication rate for a single-pixel green micro-LED-based VLC system.