Nitride semiconductor substrate
The characteristic of Fe-doped HEMTs is improved. The invention provides a nitride semiconductor substrate having a substrate, a buffer layer made of nitride semiconductors on the substrate, and an active layer composed of nitride semiconductor layers on the buffer layer; the buffer layer containing Fe, the Fe having a concentration profile in which the Fe concentration increases monotonically and gradually in the thickness direction of the buffer layer from an interface between the substrate and the buffer layer, has a maximum value within 2×10 17 to 1.1×10 20 atoms/cm 3 inclusive, and decreases monotonically and gradually toward an interface between the buffer layer and the active layer, and the point of the maximum value being within ±50 nm from the midpoint in the thickness direction of the buffer layer, and being 500 nm or more away from the interface between the buffer layer and the active layer.
1. A nitride semiconductor substrate having a substrate, a buffer layer made of nitride semiconductors on the substrate, and an active layer composed of nitride semiconductor layers on the buffer layer;
the buffer layer containing Fe,
the Fe having a concentration profile in which the Fe concentration increases monotonically and gradually in the thickness direction of the buffer layer from an interface between the substrate and the buffer layer, has a maximum value within a range of 2×10 17 to 1.1×10 20 atoms/cm 3 inclusive, and then decreases monotonically and gradually toward an interface between the buffer layer and the active layer, and
the point of the maximum value being within a range of ±50 nm from the midpoint in the thickness direction of the buffer layer, and being 500 nm or more away from the interface between the buffer layer and the active layer.