Abstract: A method for recycling a sapphire substrate is disclosed. The method includes the steps of: high-temperature baking, wherein an intact epitaxial wafer to be scrapped is placed and baked in a baking oven at a high temperature of from 600° C. to 1000° C., and wherein the epitaxial wafer contains the sapphire substrate; and high-temperature rinsing in a concentrated acid, wherein the baked epitaxial wafer is then rinsed in the concentrated acid having a concentration ranging from 60% to 99% at a high temperature of from 160° C. to 300° C. The method can be used for recycling both patterned and smooth sapphire substrates.

Abstract: A GaN-based LED epitaxial structure comprises a non-doped GaN buffer layer, an undoped GaN layer, an N-type GaN layer, an InGaN/GaN superlattice quantum well structure, a multiple quantum well luminous layer structure, an AlGaN layer, a low-temperature P-type layer, a P-type electron blocking layer and a P-type GaN layer which are sequentially stacked, wherein the non-doped GaN buffer layer comprises a sandwich structure consisting of a GaN layer, an AlGaN layer and a GaN layer which are sequentially stacked. For the GaN-based LED epitaxial structure and the preparation method thereof, the non-doped GaN buffer layer with the sandwich structure consisting of the GaN layer, the AlGaN layer and the GaN layer is used as a buffer layer, the buffer layer changes light scattering directions by using materials with different refractive indexes and thus the luminous efficiency can be improved.

Abstract: In order to address the high recycling cost, high complexity and other problems encountered by the prior art, the present invention proposes a method for recycling a sapphire substrate, which is applicable to both patterned and smooth sapphire substrates and involves only two steps: high-temperature baking and high-temperature rinsing in a concentrated acid. It entails a simple process which can be completed with high efficiency in a short period by easy operations at significantly reduced cost.

Abstract: A GaN-based LED epitaxial structure comprises a non-doped GaN buffer layer, an undoped GaN layer, an N-type GaN layer, an InGaN/GaN superlattice quantum well structure, a multiple quantum well luminous layer structure, an AlGaN layer, a low-temperature P-type layer, a P-type electron blocking layer and a P-type GaN layer which are sequentially stacked, wherein the non-doped GaN buffer layer comprises a sandwich structure consisting of a GaN layer, an AlGaN layer and a GaN layer which are sequentially stacked. For the GaN-based LED epitaxial structure and the preparation method thereof, the non-doped GaN buffer layer with the sandwich structure consisting of the GaN layer, the AlGaN layer and the GaN layer is used as a buffer layer, the buffer layer changes light scattering directions by using materials with different refractive indexes and thus the luminous efficiency can be improved.