Effects of Chip\nSize and Thermally Oxidized Al<sub><i>x</i></sub>Ga<sub>2–<i>x</i></sub>O<sub>3</sub> Sidewall on the Optoelectrical\nCharacteristics of AlGaN-Based\nDeep Ultraviolet Micro-

The thermally oxidized Al<sub><i>x</i></sub>Ga<sub>2–<i>x</i></sub>O<sub>3</sub> sidewall was\nintroduced to deep ultraviolet\nmicro-light-emitting diodes (DUV μ-LEDs) to improve optoelectronic\nperformance. Reducing the chip size of DUV μ-LEDs suppresses\nthe current crowding effect and decreases the forward voltage (<i>V</i><sub>f</sub>) and dynamic resistance at a current density\nof 10<sup>2</sup> A/cm<sup>2</sup>. After the thermally oxidized Al<sub><i>x</i></sub>Ga<sub>2–<i>x</i></sub>O<sub>3</sub> sidewall was introduced, the <i>V</i><sub>f</sub> and dynamic resistance in all DUV μ-LEDs with varying chip\nsizes increased. The <i>V</i><sub>f</sub> and dynamic resistance\nare further increased by thickening of the thermally oxidized Al<sub><i>x</i></sub>Ga<sub>2–<i>x</i></sub>O<sub>3</sub> sidewall. The light output power densities of all DUV μ-LEDs\nwith varying chip sizes were enhanced by introducing the thermally\noxidized Al<sub><i>x</i></sub>Ga<sub>2–<i>x</i></sub>O<sub>3</sub> sidewall, and the light extraction efficiency\ncould be improved. The light output power density was also enhanced\nby thickening the thermally oxidized Al<sub><i>x</i></sub>Ga<sub>2–<i>x</i></sub>O<sub>3</sub> sidewall. Although\nreducing the chip size of the DUV μ-LEDs increased the light\nextraction, the thermally oxidized Al<sub><i>x</i></sub>Ga<sub>2–<i>x</i></sub>O<sub>3</sub> sidewall further\nenhanced the light extraction of lateral light emission in the DUV\nμ-LEDs. In addition, the thermally oxidized Al<sub><i>x</i></sub>Ga<sub>2–<i>x</i></sub>O<sub>3</sub> sidewall\nenhanced the transverse magnetic polarized light emission in the DUV\nμ-LEDs, predominating the enhancement in the light output power\ndensity of DUV μ-LEDs.