Investigation of Emission Heterogeneity in InGaN/GaN Micro-Light-Emitting Diodes by Photon-Correlation Cathodoluminescence Spectroscopy

The emission properties of InGaN/GaN mu-light-emitting diodes (LEDs) of different sizes and shapes were investigated by spectrally resolved and time-correlated cathodoluminescence spectroscopy. This approach provides high spatial and temporal resolution, allowing us to simultaneously measure CL spectra and carrier lifetimes at the single mu-LED level. It also enables us to investigate the correlation between these parameters within individual mu-LEDs and across multiple devices. Our observations show a large variation in CL intensity between similarly sized mu-LEDs, particularly in the smallest samples. This variation correlates with changes in the emission wavelength and has been attributed to differences in injection efficiency between samples caused by V-pit type defects in the active region.