We investigate blue light-emitting diodes (LEDs) containing photonic crystals (PhCs) that are fabricated hi InGaN/GaN multiple quantum wells by plasma etching. Sulfide passivation of the etched surfaces in the LEDs using thioacetamide/ammonium solution effectively reduces the content of surface defects that induce defect-related recombination and the reverse leakage current through the sidewall surface of PhCs. Sulfide passivation enhances the optical output power of the PhC LEDs by 71% at 20 mA compared with that of planar LEDs. The large enhancement of optical power is attributed to out-coupling of confined light by the PhCs and the. effective recovery of internal quantum efficiency by sulfide passivation.