Light emitting diode

A light emitting diode comprising:

• a source layer comprising a first semiconductor layer, an active layer, and a second semiconductor layer stacked in sequence, wherein the first semiconductor layer comprises a first surface and a second surface opposite to the first surface, and the active layer and the second semiconductor layer are stacked on the second surface in sequence;
• a first electrode covering and contacting the first surface of the first semiconductor layer;
• a second electrode electrically connected with the second semiconductor layer;
• a third optical symmetric layer disposed on and contacting a surface of the second semiconductor layer away from the first semiconductor layer, wherein a refractive index of the third optical symmetric layer is in a range from about 1.2 to about 1.5;
• a metallic layer disposed on and contacting a surface of the third optical symmetric layer away from the first semiconductor layer;
• a fourth optical symmetric layer disposed on and contacting a surface of the metallic layer away from the first semiconductor layer, wherein a refractive index of the fourth optical symmetric layer is in a range from about 1.2 to about 1.5;
• and
• a first optical symmetric layer disposed on and contacting a surface of the fourth optical symmetric layer away from the first semiconductor layer, wherein a refractive index difference between the source layer and the first optical symmetric layer is smaller than or equal to 0.3.