Enhancing current spreading by designed P-electrode shapes for high efficiency and high modulation bandwidth micro-LEDs

Micro-LEDs are excellent candidates for high-resolution displays and visible-light communication (VLC). However, current crowding can significantly degrade the efficiency and modulation bandwidth of micro-LEDs, posing challenges to further development in applications. In this study, three sizes of micro-LEDs (22, 34, and 46 µm) with disk-, cross-, and ring-shaped P-electrodes were fabricated and characterized. The results demonstrated that optimizing the P-electrode shape enhances both efficiency and modulation bandwidth. The ABC + f(n) model was used to analyze the EQE, which helped in identifying the physical mechanisms for different P-electrode shapes. Notably, for the smallest 22 µm micro-LEDs, the ring-shaped P-electrode design significantly improves current spreading and enhances carrier radiative recombination, resulting in a 16.95% increase in external quantum efficiency (EQE), a 20.92% rise in light-output power (LOP), and a 14.39% enhancement in modulation bandwidth, reaching up to 151 MHz, as compared to conventional disk-shaped P-electrode micro-LEDs. Trace Pro simulation results further demonstrated that ring-shaped P-electrodes optimize the light extraction efficiency of the device. This work provides valuable guidance for fabricating high-efficiency and high-modulation-bandwidth micro-LEDs for advanced display and high-speed VLC applications.