Nitride semiconductor device and method of producing the same
A nitride semiconductor device is provided, in which a superlattice strain buffer layer using AlGaN layers having a low Al content or GaN layers is formed with good flatness, and a nitride semiconductor layer with good flatness and crystallinity is formed on the superlattice strain buffer layer. A nitride semiconductor device includes a substrate; an AlN strain buffer layer made of AlN formed on the substrate; a superlattice strain buffer layer formed on the AlN strain buffer layer; and a nitride semiconductor layer formed on the superlattice strain buffer layer, and is characterized in that the superlattice strain buffer layer has a superlattice structure formed by alternately stacking first layers made of Al x Ga 1-x N (0≦x≦0.25), which further contain p-type impurity, and second layers made of AlN.
1. A nitride semiconductor device comprising:
a substrate;
an AlN strain buffer layer made of AlN formed on the substrate;
a superlattice strain buffer layer formed on the AlN strain buffer layer; and
a nitride semiconductor layer formed on the superlattice strain buffer layer,
wherein the superlattice strain buffer layer has a superlattice structure formed by alternately stacking first layers made of Al x Ga 1-x N (0≦x≦0.25), which said first layers further contain p-type impurity, and second layers made of AlN, which said second layers are undoped layers.
2. A nitride semiconductor device comprising:
a substrate;
an AlN strain buffer layer made of AlN formed on the substrate;
a superlattice strain buffer layer formed on the AlN strain buffer layer;
an n-type nitride semiconductor layer formed on the superlattice strain buffer layer;
a light emitting layer formed on the n-type nitride semiconductor layer;
a p-type nitride semiconductor layer formed on the light emitting layer;
an n-side electrode electrically coupled to the n-type nitride semiconductor layer; and
a p-side electrode electrically coupled to the p-type nitride semiconductor layer,
wherein the superlattice strain buffer layer has a superlattice structure formed by alternately stacking first layers made of Al x Ga 1-x N (0≦x≦0.25), which said first layers further contain p-type impurity, and second layers made of AlN, which said second layers are undoped layers.
3. The nitride semiconductor device according to claim 1 , wherein the p-type impurity is any one selected from the group consisting of Mg, Zn, Ca, and Be.
4. The nitride semiconductor device according to claim 1 , wherein a thickness of each of the first layers is 0.1 nm to 3 nm.
5. The nitride semiconductor device according to claim 1 , wherein a concentration of the p-type impurity in the first layers is 5×10 16 cm −3 or more and less than 2×10 19 cm −3 .
6. A method of producing a nitride semiconductor device, comprising the steps of:
forming an AlN strain buffer layer made of AlN on a substrate;
forming a superlattice strain buffer layer on the AlN strain buffer layer; and
forming a nitride semiconductor layer on the superlattice strain buffer layer,
wherein the step of forming the superlattice strain buffer layer is a step of forming a superlattice structure by alternately stacking first layers made of Al x Ga 1-x N (0≦x≦0.25), which said first layers further contain p-type impurity, and second layers made of AlN, which said second layers are undoped layers.
7. A method of producing a nitride semiconductor device, comprising the steps of:
forming an AlN strain buffer layer made of AlN on a substrate;
forming a superlattice strain buffer layer on the AlN strain buffer layer;
forming an n-type nitride semiconductor layer on the superlattice strain buffer layer;
forming a light emitting layer on the n-type nitride semiconductor layer;
forming a p-type nitride semiconductor layer on the light emitting layer;
forming an n-side electrode electrically coupled to the n-type nitride semiconductor layer; and
forming a p-side electrode electrically coupled to the p-type nitride semiconductor layer,
wherein the step of forming the superlattice strain buffer layer is a step of forming a superlattice structure by alternately stacking first layers made of Al x Ga 1-x N (0≦x≦0.25), which said first layers further contain p-type impurity, and second layers made of AlN, which said second layers are undoped layers.
8. The method of producing a nitride semiconductor device according to claim 7 , wherein the step of forming the n-side electrode includes, after forming the p-type nitride semiconductor layer on the light emitting layer, exposing a part of the n-type nitride semiconductor layer on the light emitting layer side, and forming the n-side electrode on the exposed part.
9. The method of producing a nitride semiconductor device according to claim 6 , wherein the p-type impurity is any one selected from the group consisting of Mg, Zn, Ca, and Be.
10. The method of producing a nitride semiconductor device according to claim 6 , wherein a thickness of each of the first layers is 0.1 nm to 3 nm.
11. The method of producing a nitride semiconductor device according to claim 6 , wherein a concentration of the p-type impurity in the first layers is 5×10 16 cm −3 or more and less than 2×10 19 cm −3 .