InGaN-based blue and red micro-LEDs: Impact of carrier localization

Herein, we investigate micro-light-emitting diodes (mu LEDs) ranging in size from 160 x 160 to 10 x 10 mu m(2) and report that the differences in the behavior of InGaN-based blue (similar to 460 nm) and red (similar to 600 nm) mu LEDs are related to carrier localization. The external quantum efficiency (EQE) of blue mu LEDs decreases with size regardless of sidewall conditions, whereas that of red mu LEDs is insignificant due to carrier localization. Atomic probe tomography examination of 30%, 15%, and 7.5% indium-concentrated InGaN layers used in red mu LEDs shows that higher indium concentrations result in greater indium fluctuations, which promote carrier localization and thus shorten the diffusion length of carriers. Finally, by observing the peak wavelength of electroluminescence and the current density at peak EQE for both blue and red mu LEDs, we find that radiative recombination rate in mu LEDs is likely to be chip size dependent.