Light-emitting diode

A light-emitting diode, comprising:

• a semiconductor epitaxial structure that has a first surface and a second surface opposite to said first surface, and that includes a first current spreading layer, a first transition layer, a first cladding layer, a second transition layer, a first confinement layer, an active layer, a second confinement layer, a second cladding layer-and a second current spreading layer disposed sequentially in such order from said first surface to said second surface,
• wherein
• said first current spreading layer, said first cladding layer and said first confinement layer-independently have semiconductor materials that are different in an aluminum content,
• said first transition layer has aluminum, and an aluminum content of said first transition layer gradually increases from an interface of said first transition layer with said first current spreading layerto an interface of said first transition layer with said first cladding layer,
• said second transition layer has aluminum, and an aluminum content of said second transition layer gradually decreases from an interface of said second transition layer with said first cladding layerto an interface of said second transition layer with said first confinement layer, and
• said aluminum content of said first confinement layer is smaller than said aluminum content of said first cladding layer.