Epitaxial structure for improving luminous efficiency and preparation method thereof

The invention provides an epitaxial structure for improving luminous efficiency. The epitaxial structure for improving the luminous efficiency sequentially comprises a substrate, a first GaN (Gallium Nitride) buffer layer, a second GaN buffer layer, an N-type GaN layer, a multi-quantum well (MQW) structure, a light-emitting layer multi-quantum well structure, a p-type GaN layer, a p-type AlGaN (aluminium gallium nitride) layer, a p-type GaN layer and a p-type contact layer from the bottom up, wherein the multi-quantum well structure consists of n layers of InxGa1-XN/GaN multi-quantum wells; the widths, the depths and the barrier heights of the n layers of the multi-quantum wells increase layer by layer; the barrier widths of the n layers of the multi-quantum wells decrease layer by layer; the well widths increasing layer by layer and the barrier widths decreasing layer by layer form regular correspondence; and n is an integer in a range of 2-12. A preparation method of the epitaxial structure for improving the luminous efficiency can optimize concentration distribution of electrons, reduce stresses generated in growth processes of multi-quantum wells, reduce a quantum confined stark effect (QCSE) and improve the luminous efficiency of the multi-quantum wells.