Diode having high brightness and method thereof

A light emitting device, comprising:

• a substrate including a first surface and a second surface opposing the first surface of the substrate;
• a reflective layer disposed on the second surface of the substrate, the reflective layer including aluminum;
• a light emitting structure disposed on the first surface of the substrate, the light emitting structure including a first semiconductor layer, a second semiconductor layer, and an active layer between the first semiconductor layer and the second semiconductor layer, wherein the active layer includes aluminum and indium;
• a transparent conductive layer disposed on the second semiconductor layer;
• a first electrode disposed on the first semiconductor layer;
• a second electrode disposed on the transparent conductive layer;
• a first pad disposed on the first electrode;
• and
• a second pad disposed on the second electrode, the second pad having a thickness of about 500 nanometers or higher,
• wherein the second pad includes Au,
• wherein at least a portion of the second surface of the substrate has a surface roughness of less than 15 nanometers, and
• wherein the reflective layer substantially entirely covers the second surface of the substrate and has a thickness of less than 300 nanometers.