Quantitative Analysis\nand Characterization of Sidewall\nDefects in InGaN-Based Blue Micro-LEDs

Inorganic micro-light-emitting diodes (μLEDs) have\nemerged\nas promising candidates to fulfill the demand for high-performance\ndisplay technologies like immersive virtual or augmented displays.\nHowever, reducing μLED size for increasing pixel density results\nin poor external quantum efficiency (EQE), caused by the pronounced\nimpact of defects-mediated Shockley–Read–Hall (SRH)\nnonradiative recombination at the etched sidewalls. Distinguishing\nthe SRH coefficient, denoted as <i>A</i> coefficient, and\nthe associated energy trap levels specific to the defects on the etched\nsidewalls from those in the bulk can be very advantageous to identify\n the origin of the defects responsible for the size-dependent EQE\ndegradation. This, in turn, facilitates the development of appropriate\nstrategies for high performance μLED-based displays. In this\nstudy, the effect of etched sidewall on the EQE of blue μLEDs\nis distinguished from that of bulk by investigating size- and temperature-dependent\nEQE values versus current density. The energy trap levels of both\nbulk and sidewall defects, as well as the minority carrier lifetime\n(τ<sub>0</sub>) associated with each defect, were estimated\nthrough temperature-dependent characterization of the <i>A</i> coefficient in μLEDs. The τ<sub>0</sub> values associated\nwith sidewall defects are approximately 12 times shorter than those\nfor bulk defects, indicating that the SRH recombination process predominantly\noccurs at the sidewall rather than bulk in μLEDs. This quantitative\nanalysis elucidates the significance of sidewall defect mitigation\nstrategies in advancing high-resolution μLED display technologies.