Revealing luminescence mechanisms in red InGaN micro-LEDs via spatially resolved, temperature- and current-dependent electroluminescence

In order to elucidate the luminescence mechanisms in red InGaN micro-LEDs, we measured and analyzed spatially resolved and temperature- and current-dependent electroluminescence spectra. Under low current density, a high-energy emission peak other than the red one was observed in regions containing V-pit defects, while the red emission intensity in these V-pit regions is relatively stronger. The above-mentioned phenomenon can be explained by high-energy emission from the quantum wells at the sidewall of V-pits and the carrier leakage channels through the V-pit defects. These channels facilitate electron–hole recombination along the z axis direction. Further temperature- and current-dependent measurements revealed an anomalous temperature-dependent behavior: under an injection current of 1 mA, when the temperature drops below 160 K, the optical power decreases with further cooling. This is mainly ascribed to the transfer of carriers between different localized states, which modifies their distribution and recombination within the xy-plane of the quantum wells. Collectively, our models provide a comprehensive explanation of the carrier dynamics and spatial kinetics of red InGaN LEDs in different emission regions and under varying temperature and current conditions, offering important insights into the emission mechanisms and valuable guidance for the optimization of epitaxial structure design.