Impact of the Surface Recombination on the Thermal Properties for GaN-Based μLEDs

In this report, the internal self-heating characteristics for GaN-based micro-light emitting diodes ( $\mu $ LEDs) are studied by designing and comparing devices with different sizes of $30\times 30\,\,\mu \text{m}^{2}$ and $60\times 60\,\,\mu \text{m}^{2}$ . We find that the surface non-radiative recombination caused by sidewall defects serves as heat source, which is further proven by investigating the $\mu $ LED optoelectronic properties before and after KOH treatment. The results show that smooth surfaces can be obtained after KOH treatment for $\mu $ LEDs. This correspondingly generates less leakage current, reduces the ideality factor to 2.55, and the recombination heat can also be reduced. The reduced self-heating effect gives rise to a reduced redshift for the peak emission wavelength and the full width at half maximum (FWHM) also gets decreased.