Nitride semiconductor device and method of manufacturing nitride semiconductor device
A nitride semiconductor device may comprise a p-type layer. The nitride semiconductor device may comprise a first n-type voltage-blocking layer in contact with the p-type layer. The nitride semiconductor device may comprise a second n-type voltage-blocking layer in contact with the first n-type voltage-blocking layer and separated from the p-type layer by the first n-type voltage-blocking layer. A donor concentration in the first n-type voltage-blocking layer may be lower than a donor concentration in the second n-type voltage-blocking layer. A carbon concentration in the first n-type voltage-blocking layer may be lower than a carbon concentration in the second n-type voltage-blocking layer.
1. A nitride semiconductor device comprising:
a p-type layer;
a first n-type voltage-blocking layer in contact with the p-type layer; and
a second n-type voltage-blocking layer in contact with the first n-type voltage-blocking layer and separated from the p-type layer by the first n-type voltage-blocking layer,
wherein a donor concentration in the first n-type voltage-blocking layer is lower than a donor concentration in the second n-type voltage-blocking layer, and
a carbon concentration in the first n-type voltage-blocking layer is lower than a carbon concentration in the second n-type voltage-blocking layer.
2. The nitride semiconductor device according to claim 1 , wherein
the carbon concentration in the first n-type voltage-blocking layer is constant and is at a first concentration,
the carbon concentration in the second n-type voltage-blocking layer is constant and is at a second concentration, and
the first concentration is lower than the second concentration.
3. The nitride semiconductor device according to claim 1 , wherein
the carbon concentration in the first n-type voltage-blocking layer becomes higher as a distance from an interface between the first n-type voltage-blocking layer and the p-type layer increases.
4. The nitride semiconductor device according to claim 1 , wherein
an E3 electron trap concentration in the first n-type voltage-blocking layer is lower than the carbon concentration in the first n-type voltage-blocking layer, and
an E3 electron trap concentration in the second n-type voltage-blocking layer is lower than the carbon concentration in the second n-type voltage-blocking layer.
5. The nitride semiconductor device according to claim 1 , wherein
a thickness of the second n-type voltage-blocking layer is thicker than a thickness of the first n-type voltage-blocking layer.
6. A method of manufacturing a nitride semiconductor device provided with a p-type layer, a first n-type voltage-blocking layer, and a second n-type voltage-blocking layer, the method comprising:
forming the second n-type voltage-blocking layer on a nitride semiconductor substrate by an epitaxial growth method;
forming the first n-type voltage-blocking layer in contact with the second n-type voltage-blocking layer by the epitaxial growth method; and
forming the p-type layer in contact with the first n-type voltage-blocking layer and separated from the second n-type voltage-blocking layer by the first n-type voltage-blocking layer, wherein
a growth rate of the second n-type voltage-blocking layer is higher than a growth rate of the first n-type voltage-blocking layer.
7. The method of manufacturing a nitride semiconductor device according to claim 6 , wherein
the epitaxial growth method is a metalorganic vapor growth method, and
a V/III ratio in growing the second n-type voltage-blocking layer is lower than a V/III ratio in growing the first n-type voltage-blocking layer.
8. The nitride semiconductor device according to claim 1 , wherein
a growth rate of the second n-type voltage-blocking layer is higher than a growth rate of the first n-type voltage-blocking layer.
9. The method of manufacturing a nitride semiconductor device according to claim 6 , wherein
a carbon concentration in the first n-type voltage-blocking layer is lower than a carbon concentration in the second n-type voltage-blocking layer.