Improving the light extraction efficiency of InGaN-based red micro-LEDs via indium tin oxide transparent p-electrodes

Transparent p-electrodes can increase light extraction efficiency in micro-LEDs. We replaced conventional metal p-electrodes with highly transparent ITO p-electrodes. InGaN-based red micro-LEDs (50 µm x 50 µm) with ITO and metal p-electrodes demonstrated a very low leakage current (≤ 10-7 A/cm2) in the reverse bias regime and a similar slope in the forward bias regime, indicating identical current injection behavior for both devices. We obtained light output power enhancement by a factor of ≥ 1.2 with ITO p-electrodes thanks to their higher light extraction over metals. A peak on-wafer EQE of 0.71% with a 614 nm emission at a current density as low as 7.5 A/cm2 was obtained for micro-LEDs with ITO-p-electrodes while the on-wafer EQE of metal-based ones remained at 0.59%, showing an increase by a factor of 1.2 via ITO p-electrodes. ITO and metal-based devices exhibited an FWHM of ~53 nm and identical emission behavior in the low current injection regime. In light of these results, we show that transparent p-electrodes can significantly improve the performance of red micro-LEDs and support paving the way for future monolithic RGB display applications.