Comparison of size-dependent characteristics of blue and green InGaN microLEDs down to 1a?? <b> <i>??</i> </b> m in diameter

摘要： There is growing interest in microLED devices with lateral dimensions between 1 and 10 lm. However, reductions in external quantum ef?ciency (EQE) due to increased nonradiative recombination at the surface become an issue at these sizes. Previous attempts to study size-dependent EQE trends have been limited to dimensions above 5 lm, partly due to fabrication challenges. Here, we present size-dependent EQE data for InGaN microLEDs down to 1 lm in diameter fabricated using a process that only utilizes standard semiconductor processing techniques (i.e., lithography and etching). Furthermore, differences in EQE trends for blue and green InGaN microLEDs are compared. Green wavelength devices prove to be less susceptible to reductions in ef?ciency with the decreasing size; consequently, green devices attain higher EQEs than blue devices below 10 lm despite lower internal quantum ef?ciencies in the bulk material. This is explained by smaller sur- face recombination velocities with the increasing indium content due to enhanced carrier localization.