The invention discloses an LED (
light emitting diode)
epitaxy structure and a preparation method thereof. The LED
epitaxy structure successively comprises a substrate, a GaN nucleating layer, multiple pairs of
superlattice buffer
layers, an n-GaN layer, an MQW luminescent layer, a p-GaN layer and a p-type
contact layer from bottom to top, wherein each
superlattice buffer layer is formed by an AlGaN / n-GaN alternately stacked structure. The LED
epitaxy structure is characterized in that Al(n) is defined to represent an Al component value in the nth pair of AlGaN / n-GaN
superlattice buffer layer; N(n) represents the n-type
impurity concentration value in the nth pair of AlGaN / n-GaN superlattice buffer layer; the variation trend of Al(n) is gradually lowered after being gradually raised; and the variation trend of N(n) is gradually lowered after being gradually raised. According to the LED epitaxy structure provided by the invention, lattice stress caused by
lattice mismatch due to that a
sapphire substrate and the GaN lattice are not matched can be effectively and fully released on a bottom layer growth section so as to greatly lower the warping of an epitaxial
wafer in the whole high-temperature growth process and improve the
wavelength concentricity and yield of the epitaxial
wafer. Meanwhile, the GaN lattice quality is effectively improved, the lattice
dislocation density is reduced, and the optical-electrical characteristic of the device is more stable.