Nitride semiconductor template and nitride semiconductor device
There is provided a method for manufacturing a nitride semiconductor template constituted by forming a nitride semiconductor layer on a substrate, comprising: (a) preparing a pattern-substrate as the substrate, with a concavo-convex pattern formed on a front surface of the pattern-substrate, (b) forming a first layer by epitaxially growing a nitride semiconductor containing aluminum on the concavo-convex pattern of the pattern-substrate, in a thickness of not flattening a front surface; (c) applying annealing to the first layer; and (d) forming a second layer by epitaxially growing a nitride semiconductor containing aluminum so as to overlap on the first layer after performing (c), and in a thickness of flattening a front surface, and constituting the nitride semiconductor layer by the first layer and the second layer.
1. A nitride semiconductor template, comprising:
a substrate having a plurality of convex portions formed into a cone or a polygonal pyramid on a main surface, the convex portions being arranged to create a six-fold symmetry pattern; and
a nitride semiconductor layer having:
a first layer formed on the main surface of the substrate, and having a thickness that does not flatten a front surface of the first layer, and made of a nitride semiconductor containing aluminum; and
a second layer formed so as to overlap on the first layer, and having a thickness that flattens a front surface of the second layer, and made of a nitride semiconductor containing aluminum,
wherein the main surface of the substrate is constituted as a continuous flat surface in a region excluding the convex portions,
the first layer is constituted as a continuous film on the continuous flat surface of the substrate, and is not formed on a top of the convex portion and at least on a top-side surface of a slope of the convex portion,
an average dislocation density on the front surface of the first layer on the continuous flat surface of the substrate is 1×10 9 numbers/cm 2 or less,
the first layer and the second layer contain oxygen as an impurity,
the first layer and the second layer have different oxygen concentrations, and
the nitride semiconductor layer has a thickness of 5 μm or less from an upper surface of the continuous flat surface of the substrate to a front surface of the nitride semiconductor layer.
2. The nitride semiconductor template according to claim 1 , wherein the first layer on the continuous flat surface of the substrate has a thickness of more than 100 nm and 800 nm or less.
3. A nitride semiconductor device, comprising:
the nitride semiconductor template of claim 1 ; and
a nitride semiconductor lamination structure grown and formed on the nitride semiconductor template.
4. The nitride semiconductor template according to claim 1 , wherein the nitride semiconductor layer has a thickness of more than 800 nm from an upper surface of the continuous flat surface of the substrate to a front surface of the nitride semiconductor layer.
5. The nitride semiconductor template according to claim 1 , wherein the second layer has a lower oxygen concentration than the oxygen concentration in the first layer.