The invention discloses an epitaxial
wafer of a light-emitting
diode and a preparation method thereof, and belongs to the technical field of semiconductors. The epitaxial
wafer comprises a substrate, a buffer layer, an undoped
gallium nitride layer, an N-type
gallium nitride layer, a defect
blocking layer, a first stress release layer, a second stress release layer, a third stress release layer, a light emitting layer and a P-type
gallium nitride layer, and is characterized in that the buffer layer, the undoped
gallium nitride layer, the N-type
gallium nitride layer, the defect
blocking layer, the first stress release layer, the second stress release layer, the third stress release layer, the light emitting layer and the P-type
gallium nitride layer are sequentially laminated on the substrate, the defect
blocking layer is a
silicon-doped
aluminum gallium nitride layer, the first stress release layer is a
silicon-doped gallium nitride layer, the second stress release layer comprises a plurality of first sub-
layers and a plurality of second sub-
layers which are arranged in an alternately laminating manner, the first sub-
layers are undoped InGaN layers, the second sub-layers are
silicon-doped gallium nitride layers, and the third stress release layer is a silicon-doped InGaN layer; and the
doping concentration of silicon in the defect blocking layer is lower than that of the first stress release layer, the
doping concentration of silicon in the first stress release layer is higher than that of each second sub-layer, and the
doping concentration of silicon in each second sub-layer is lower than that of the third stress release layer. The light emitting efficiency can be improved according to the invention.