Comparison of Beyond 1 GHz <i>C</i>-Plane Freestanding and Sapphire-Substrate GaN-Based micro-LEDs for High-Speed Visible Light Communication
Xinyi Shan, Guobin Wang, Shijie Zhu, Pengjiang Qiu, Runze Lin, Zhou Wang, Zexing Yuan, Qiang Yan, Xugao Cui, Jianfeng Wang, Wengang Bi, Ran Liu, Ke Xu, Pengfei Tian
Abstract
With ever-growing demand for 6G networks technology, visible light communication (VLC) as a vital component of 6G has challenging requirement for superior performance of light source. Herein, 20 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> m blue micro-LED fabricated on 2-inch <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</i> -plane GaN freestanding substrate with high bandwidth over 1 GHz was first demonstrated, and the systematic comparisons to sapphire-substrate micro-LED from the epitaxial materials characterization to optoelectronic properties as well as communication performance were further conducted. GaN-substrate LED wafer has high crystal quality with lower threading dislocation density (TDD), which is two orders of magnitude lower than that of sapphire-substrate LED wafer. The much lower TDD of GaN-substrate LED wafer and better heat dissipation of GaN substrate offer GaN-substrate micro-LED great advantages in optoelectronic properties as well as communication performance. GaN-substrate micro-LED exhibited higher light output power (LOP) especially at high operating current, which is improved by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 21% at 96 mA compared to that of sapphire substrate. Also, GaN-substrate micro-LED achieved a relatively higher bandwidth of 1.282 GHz while maintaining higher LOP with lower operating voltage. And a higher data rate of 4.48 Gbps under 1 m free space link was obtained by GaN-substrate micro-LED, proving it being a promising candidate in high-speed VLC.