Light-output enhancement of GaN-based light-emitting diodes with surface textured ITO

The sophisticated techniques of photolithography and wet-etching are used to fabricate GaN-based LED chips with surface-textured ITO layer to enhance the light output efficiency. It is shown that the light-output power can be efficiently improved by this surface-textured method. After the triangle-lattice of close-packed micro-holes are fabricated, the light-output power of LED chips under the injection current of 20 mA exhibits 11.4% enhancement comparing to the conventional LED chips. However, the forward voltage correspondingly increases 0.178 V. With our proposed micro-structures, the light-output power can also be enhanced by 8.2%, while the forward voltage increases only 0.044 V. It is also shown that the close-packed micro-hole pattern benefits high light-output under small injection current. However, this pattern would induce current-crowding if the injection current become high, and thus the light-output efficiency would decrease significantly. On the other hand, our optimized micro-structure is help for high electric-injection efficiency. This induces a high light-output efficiency, and the efficiency droop can be suppressed. The proposed micro-structure is preferred for high power LED chips under large current injection.