A multi-wavelength light-emitting diode epitaxial structure comprises of a substrate and at least three light-emitting elements, wherein the light-emitting elements are sequentially stacked on the substrate. For each two adjacent light-emitting elements, the light-emitting element disposed closer to the light-exiting surface has a higher bandgap than that of the light-emitting element disposed farther from the light-exiting surface. Each of the light-emitting elements comprises of an active layer and two cladding layers disposed on two opposite sides of the active layer, and each active layer includes a multiple quantum well structure. Cladding layers of different refractive indexes are arranged incrementally from the substrate to the light-exiting surface. Any given two adjacent cladding layers from two light-emitting elements have a combined thickness of 1 μm or less. The emission wavelengths of the light-emitting elements are ultraviolet or infrared bands.
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