The sidewall damage, introduced by dry etching, is one of the key problems that seriously hinder the industrialization of high-efficiency micro-light-emitting diodes (LEDs). Unfortunately, current research is primarily based on traditional square or circular structures, often ignoring the orientation of the sidewall crystal planes. To address this issue, in this work, we prepared, respectively, micro-LEDs with full-a-sided (device-A) and full-m-sided (device-M) hexagonal structures of different sizes, breaking the limitations of traditional structures, and the detailed influence of sidewall crystal orientation, without any treatment, under dry etching on the optoelectronic performance of micro-LEDs was investigated. The results show that device-M has a lower nonradiative recombination center density and exhibits superior photoelectric performance. In terms of electrical properties, device-M has smaller additional resistance introduced by etching damage and a lower turn-on voltage. When the radius of the circumscribed circle is 10 μm, the series resistance of device-M is 165.8 Ω, which is 21.2% lower than that of device-A. As for optical properties, the external quantum efficiency (EQE) of device-M has been greatly improved. As the device size decreases from 50 to 10 μm, the peak EQE of device-A drops from 15.69% to 15.03%, and the peak EQE of device-M drops from 16.18% to 15.09%. This work breaks with conventional thinking, proposing sidewall crystal plane engineering and revealing its relationship with performance, thus providing a new direction for the fabrication of micro-LEDs.
Zhang et al. (Mon,) studied this question.