P-Metal Geometry Impacts Micro-LEDs Efficiency: Current Spreading and Light Extraction

P-metal geometry has a significant impact on chip current spreading, which, in turn, affects the optoelectronic characteristics of the devices. We designed and fabricated a series of $37~\mu $ m square mesa of micro-LED green chips with different P-metal geometries (ring-shaped, disk-shaped, and cross shaped), and subsequently investigated their optoelectronic characteristics. The results demonstrate that the optimal optoelectronic characteristics are achieved when the P-metal is cross-shaped, with an external quantum efficiency of up to 18.85%. This represents improvements of 12.20% and 3.52% compared to devices with ring-shaped and disk-shaped P-metals, respectively. The analysis suggests that this is because the cross-shaped P-metal structure is better suited to the square mesa and results in a more uniform spreading of the chip current. COMSOL and TracePro simulations were used to analyze the current spreading and light output of chips with different P-metal geometries and verify our hypothesis. This study is expected to be significant in the design and fabrication of micro-LED chips.