Epitaxial substrate, light-emitting diode, and methods for making the epitaxial substrate and the light-emitting diode

Abstract

An epitaxial substrate includes: a base member; and a plurality of spaced apart light-transmissive members, each of which is formed on and tapers from an upper surface of the base member, and each of which is made of a light-transmissive material having a refractive index lower than that of the base member. A light-emitting diode having the epitaxial substrate, and methods for making the epitaxial substrate and the light-emitting diode are also disclosed.

1 . An epitaxial substrate, comprising:
 a base member; and   a plurality of spaced apart light-transmissive members, each of which is formed on and tapers from an upper surface of said base member, and each of which is made of a light-transmissive material having a refractive index lower than that of said base member.   
     
     
         2 . The epitaxial substrate of  claim 1 , wherein each of said light-transmissive members is in a cone-shape, and has a bottom face that contacts said upper surface of said base member and that has a maximum width, and a height from said bottom face, a ratio of said height to said maximum width being not less than 0.25. 
     
     
         3 . The epitaxial substrate of  claim 1 , wherein said light-transmissive members are spaced apart from one another by a distance not greater than 1 μm. 
     
     
         4 . The epitaxial substrate of  claim 1 , wherein said light-transmissive material has a heat resistivity of not less than 1000° C. 
     
     
         5 . The epitaxial substrate of  claim 1 , wherein said light-transmissive material is selected from the group consisting of silicon oxide, silicon oxynitride, and magnesium fluoride. 
     
     
         6 . The epitaxial substrate of  claim 1 , wherein said base member is made from a material selected from the group consisting of aluminum oxide, silicon carbide, silicon, and aluminum nitride. 
     
     
         7 . A method for making an epitaxial substrate, comprising:
 (a) forming over a base member a light-transmissive layer that is made of a light-transmissive material having a refractive index lower than that of the base member;   (b) forming a patterned mask over the light-transmissive layer;   (c) heat-treating the patterned mask at a temperature not higher than a glass transition temperature of the patterned mask;   (d) performing a dry-etching treatment on the light-transmissive layer and the patterned mask that is heat-treated, so that the light-transmissive layer is formed into a plurality of spaced apart light-transmissive members; and   (e) removing the patterned mask from the light-transmissive members.   
     
     
         8 . The method of  claim 7 , wherein each of the light-transmissive members is in a cone-shape, and has a bottom face that contacts an upper surface of said base member and that has a maximum width, and a height from the bottom face, a ratio of the height to the maximum width being not less than 0.25, the light-transmissive members being spaced apart from one another by a distance not greater than 1 μm. 
     
     
         9 . The method of  claim 7 , wherein the light-transmissive material has a heat resistivity of not less than 1000° C. 
     
     
         10 . The method of  claim 7 , wherein the light-transmissive material is selected from the group consisting of silicon oxide, silicon oxynitride, and magnesium fluoride. 
     
     
         11 . The method of  claim 7 , wherein the base member is made from a material selected from the group consisting of aluminum oxide, silicon carbide, silicon, and aluminum nitride. 
     
     
         12 . A light-emitting diode, comprising:
 an epitaxial substrate including a base member, and a plurality of spaced apart light-transmissive members, each of which is formed on and tapers from an upper surface of said base member, and each of which is made of a light-transmissive material having a refractive index lower than that of said base member; and   a light-emitting unit formed on said epitaxial substrate to cover said light-transmissive members.   
     
     
         13 . The light-emitting diode of  claim 12 , wherein each of said light-transmissive members is in a cone-shape, and has a bottom face that contacts said upper surface of said base member and that has a maximum width, and a height from the bottom face, a ratio of the height to the maximum width being not less than 0.25, said light-transmissive members being spaced apart from one another by a distance not greater than 1 μm. 
     
     
         14 . The light-emitting diode of  claim 12 , wherein said light-emitting unit and said light-transmissive members cooperatively define at least one cavity therebetween. 
     
     
         15 . The light-emitting diode of  claim 12 , wherein said base member is made from a material selected from the group consisting of aluminum oxide, silicon carbide, silicon, and aluminum nitride. 
     
     
         16 . The light-emitting diode of  claim 12 , wherein said light-transmissive material is selected from the group consisting of silicon oxide, silicon oxynitride, and magnesium fluoride. 
     
     
         17 . A method for making a light-emitting diode, comprising:
 (a) forming over a base member a light-transmissive layer that is made of a light-transmissive material having a refractive index lower than that of the base member;   (b) forming a patterned mask over the light-transmissive Layer;   (c) heat-treating the patterned mask at a temperature not higher than a glass transition temperature of the patterned mask;   (d) performing a dry-etching treatment on the light-transmissive layer and the patterned mask that is heat-treated, so that the light-transmissive layer is formed into a plurality of spaced apart light-transmissive members, followed by removing the patterned mask from the light-transmissive members; and   (e) forming a light-emitting unit over the light-transmissive members.   
     
     
         18 . The method  claim 17 , wherein each of the light-transmissive members is in a cone-shape, and has a bottom face that contacts an upper surface of said base member and that has a maximum width, and a height from the bottom face, a ratio of the height to the maximum width being not less than 0.25, the light-transmissive members being spaced apart from one another by a distance not greater than 1 μm. 
     
     
         19 . The method of  claim 17 , wherein the step (e) includes:
 laterally and epitaxially growing a first-type semiconductor layer over the light-transmissive members, the first-type semiconductor layer and the light-transmissive members cooperatively defining at least one cavity therebetween.   
     
     
         20 . The method of  claim 17 , wherein the base member is made from a material selected from the group consisting of aluminum oxide, silicon carbide, silicon, and aluminum nitride. 
     
     
         21 . The method of  claim 17 , wherein the light-transmissive material is selected from the group consisting of silicon oxide, silicon oxynitride, and magnesium fluoride.