Surface Recombinations in III-Nitride Micro-LEDs Probed by Photon-Correlation Cathodoluminescence

III-Nitride micro-LEDs are promising building blocks for the next generation of high performance microdisplays. To reach a high pixel density, it is desired to achieve micro-LEDs with lateral dimensions below 10 μm. With such pixel downscaling, sidewall effects are becoming important, and an understanding of the impact of nonradiative surface recombinations is of vital importance. It is thus required to develop an adapted metric to evaluate the impact of these surface recombinations with a nanoscale spatial resolution. Here, we propose a methodology to quantitatively assess the influence of surface recombinations on the optical properties of InGaN/GaN quantum wells based on spatially resolved time-correlated cathodoluminescence spectroscopy. By coupling this technique to a simple diffusion model, we confirm that the combination of KOH treatment and Al2O3 passivation layer drastically reduces surface recombinations. These findings emphasize the need for nanoscale time-resolved experiments to quantify the local changes in internal quantum efficiency of microdevices.