A light emitting diode comprising an epitaxial layer structure, a first electrode, and a second electrode. The first and second electrodes are disposed on one side of the epitaxial layer structure. The epitaxial layer structure includes a transparent ohmic contact layer having a root-means-square (RMS) roughness less than about 3 nm at a surface whereon the second electrode is formed. The epitaxial layer structure includes a p-type epitaxial layer and a n-type epitaxial layer, wherein the n-type epitaxial layer is coupled between the first electrode and the p-type epitaxial layer, and the p-type epitaxial layer is between the second electrode and the n-type epitaxial layer. The first electrode is located on the n-type epitaxial layer.