Effects of Chip Size and Thermally Oxidized Al_<i>x</i>Ga_2–<i>x</i>O₃ Sidewall on the Optoelectrical Characteristics of AlGaN-Based Deep Ultraviolet Micro-Light-Emitting Diodes

The thermally oxidized AlxGa2–xO3 sidewall was introduced to deep ultraviolet micro-light-emitting diodes (DUV μ-LEDs) to improve optoelectronic performance. Reducing the chip size of DUV μ-LEDs suppresses the current crowding effect and decreases the forward voltage (Vf) and dynamic resistance at a current density of 102 A/cm2. After the thermally oxidized AlxGa2–xO3 sidewall was introduced, the Vf and dynamic resistance in all DUV μ-LEDs with varying chip sizes increased. The Vf and dynamic resistance are further increased by thickening of the thermally oxidized AlxGa2–xO3 sidewall. The light output power densities of all DUV μ-LEDs with varying chip sizes were enhanced by introducing the thermally oxidized AlxGa2–xO3 sidewall, and the light extraction efficiency could be improved. The light output power density was also enhanced by thickening the thermally oxidized AlxGa2–xO3 sidewall. Although reducing the chip size of the DUV μ-LEDs increased the light extraction, the thermally oxidized AlxGa2–xO3 sidewall further enhanced the light extraction of lateral light emission in the DUV μ-LEDs. In addition, the thermally oxidized AlxGa2–xO3 sidewall enhanced the transverse magnetic polarized light emission in the DUV μ-LEDs, predominating the enhancement in the light output power density of DUV μ-LEDs.