Template, nitride semiconductor ultraviolet light-emitting element, and method of manufacturing template
A template includes a sapphire substrate with a (0001) plane or a plane inclined by a predetermined angle with respect to the (0001) plane as a main surface, and an AlN layer composed of AlN crystals having an epitaxial crystal orientation relationship with the main surface directly formed on the main surface of the sapphire substrate. In the template, an average particle diameter of the AlN crystals of the AlN layer at a thickness of 20 nm from the main surface is 100 nm or less.
1. A method of manufacturing a template, the method comprising a step of epitaxially growing AlN crystals directly on a main surface of a sapphire substrate with one of a (0001) plane and a plane inclined by a predetermined angle with respect to the (0001) plane as the main surface to form an AlN layer,
wherein
the step includes epitaxially growing the AlN crystals under a growth condition that an average particle diameter of the AlN crystals on a surface of the AlN layer epitaxially grown from the main surface to a thickness of 20 nm is 100 nm or less and the AlN layer epitaxially grown to the thickness of 20 nm covers 90% or more of the main surface;
wherein the step further includes epitaxially growing the AlN layer with using MOVPE method by starting supply of an Al source gas at the same time or earlier than an N source gas to suppress excessive nitriding of the main surface of the sapphire substrate and make the AlN layer +C-axis oriented; and
wherein the step includes epitaxially growing the AlN layer under a growth condition that an RMS value of surface roughness of the AlN layer epitaxially grown from the main surface to a thickness of 20 nm is equal to or less than an RMS value of surface roughness of an AlN layer epitaxially grown from the main surface to a thickness of 300 nm.
2. The method of manufacturing a template according to claim 1 , wherein the step includes epitaxially growing the AlN layer under a growth condition that the average particle diameter of the AlN crystals on the surface of the AlN layer epitaxially grown from the main surface to a thickness of 300 nm is 300 nm or less.
3. The method of manufacturing a template according to claim 1 , wherein the step includes epitaxially growing the AlN layer under a growth condition that the RMS value of surface roughness of the AlN layer epitaxially grown from the main surface to a thickness of 20 nm is 5 nm or less.
4. The method of manufacturing a template according to claim 1 , wherein the step includes epitaxially growing the AlN layer under a growth condition that an RMS value of surface roughness of the AlN layer epitaxially grown from the main surface to a thickness of 300 nm is 10 nm or less.
5. The method of manufacturing a template according to claim 1 , wherein the step includes epitaxially growing the AlN layer under a growth condition that the AlN crystals on the surface of the AlN layer epitaxially grown from the main surface to a thickness of 300 nm are +C-axis oriented.
6. The method of manufacturing a template according to claim 1 , wherein the step includes setting a growth temperature of the AlN layer at 1150° C. or higher and 1300° C. or lower.