Semiconductor electronic device
A semiconductor electronic device comprises a substrate; a buffer layer formed on the substrate, the buffer layer including not less than two layers of composite layer in which a first semiconductor layer formed of a nitride-based compound semiconductor layer having a lattice constant smaller than a lattice constant of the substrate and a thermal expansion coefficient larger than a thermal expansion coefficient of the substrate and a second semiconductor layer formed of a nitride-based compound semiconductor having a lattice constant smaller than a lattice constant of the first semiconductor layer and a thermal expansion coefficient larger than a thermal expansion coefficient of the substrate are alternately laminated; an intermediate layer provided between the substrate and the buffer layer, the intermediate layer being formed of a nitride-based compound semiconductor having a lattice constant smaller than a lattice constant of the first semiconductor layer and a thermal expansion coefficient larger than a thermal expansion coefficient of the substrate; and a semiconductor active layer formed on the buffer layer, the semiconductor active layer being formed of a nitride-based compound semiconductor, wherein: thicknesses of the first semiconductor layers in the buffer layer are non-uniform thereamong, and at least one of the first semiconductor layer has a thickness greater than a critical thickness, the critical thickness being a thickness above which a direction of warp caused by the first semiconductor layer to the substrate is inverted.
1. A semiconductor electronic device comprising:
a substrate;
a buffer layer formed on the substrate, the buffer layer including not less than two layers of composite layer in which a first semiconductor layer formed of a nitride-based compound semiconductor layer having a lattice constant smaller than a lattice constant of the substrate and a thermal expansion coefficient larger than a thermal expansion coefficient of the substrate and a second semiconductor layer formed of a nitride-based compound semiconductor having a lattice constant smaller than a lattice constant of the first semiconductor layer and a thermal expansion coefficient larger than a thermal expansion coefficient of the substrate are alternately laminated;
an intermediate layer provided between the substrate and the buffer layer, the intermediate layer being formed of a nitride-based compound semiconductor having a lattice constant smaller than a lattice constant of the first semiconductor layer and a thermal expansion coefficient larger than a thermal expansion coefficient of the substrate; and
a semiconductor active layer formed on the buffer layer, the semiconductor active layer being formed of a nitride-based compound semiconductor, wherein:
thicknesses of the first semiconductor layers in the buffer layer are non-uniform thereamong, and
at least one of the first semiconductor layer has a thickness greater than a critical thickness, the critical thickness being a thickness above which a direction of warp caused by the first semiconductor layer to the substrate is inverted.
2. The semiconductor electronic device according to claim 1 , wherein the buffer layer is formed such that the thickness of the first semiconductor layers increases in a direction of lamination.
3. The semiconductor electronic device according to claim 1 , wherein the buffer layer is formed such that the thickness of the first semiconductor layers decreases in a direction of lamination.
4. The semiconductor electronic device according to claim 1 , wherein any one of the first semiconductor layers located at first to fourth positions as counted from the substrate is not less than 400 nm and not greater than 3000 nm in thickness, and is thicker than other first semiconductor layers.
5. The semiconductor electronic device according to claim 1 , wherein the first semiconductor layer having a thickness greater than the critical thickness is located at a portion higher than two thirds of the number of the composite layers of the buffer layer.
6. The semiconductor electronic device according to claim 1 , wherein the first semiconductor layer having a thickness greater than the critical thickness is located at a portion lower than one third of the number of the composite layers of the buffer layer.
7. The semiconductor electronic device according to claim 1 , wherein the first semiconductor layer having a thickness greater than the critical thickness is located between one third and two thirds of the number of the composite layers of the buffer layer.
8. The semiconductor electronic device according to claim 1 , wherein the first semiconductor layer having a thickness greater than the critical thickness is not less than 400 nm and not greater than 3000 nm in thickness.
9. The semiconductor electronic device according to claim 1 , wherein the first semiconductor layer is formed of GaN and the second semiconductor layer is formed of AlxGa1-xN (0<x≦1).
10. The semiconductor electronic device according to claim 1 , wherein the second semiconductor layers are not less than 0.5 nm and not greater than 200 nm in thickness.
11. The semiconductor electronic device according to claim 1 , wherein the substrate is formed of any one of Si, SiC, and ZnO.
12. A semiconductor electronic device comprising:
a substrate;
a buffer layer formed on the substrate, the buffer layer including not less than two layers of composite layer in which a first semiconductor layer formed of a nitride-based compound semiconductor layer having a lattice constant smaller than a lattice constant of the substrate and a thermal expansion coefficient larger than a thermal expansion coefficient of the substrate and a second semiconductor layer formed of a nitride-based compound semiconductor having a lattice constant smaller than a lattice constant of the first semiconductor layer and a thermal expansion coefficient larger than a thermal expansion coefficient of the substrate are alternately laminated;
an intermediate layer provided between the substrate and the buffer layer, the intermediate layer being formed of a nitride-based compound semiconductor having a lattice constant smaller than a lattice constant of the first semiconductor layer and a thermal expansion coefficient larger than a thermal expansion coefficient of the substrate; and
a semiconductor active layer formed on the buffer layer, the semiconductor active layer being formed of a nitride-based compound semiconductor,
wherein the buffer layer is formed such that the thickness of the second semiconductor layers decreases in a direction of lamination.
13. A semiconductor electronic device comprising:
a substrate;
a buffer layer formed on the substrate, the buffer layer including not less than two layers of composite layer in which a first semiconductor layer formed of a nitride-based compound semiconductor layer having a lattice constant smaller than a lattice constant of the substrate and a thermal expansion coefficient larger than a thermal expansion coefficient of the substrate and a second semiconductor layer formed of a nitride-based compound semiconductor having a lattice constant smaller than a lattice constant of the first semiconductor layer and a thermal expansion coefficient larger than a thermal expansion coefficient of the substrate are alternately laminated;
an intermediate layer provided between the substrate and the buffer layer, the intermediate layer being formed of a nitride-based compound semiconductor having a lattice constant smaller than a lattice constant of the first semiconductor layer and a thermal expansion coefficient larger than a thermal expansion coefficient of the substrate; and
a semiconductor active layer formed on the buffer layer, the semiconductor active layer being formed of a nitride-based compound semiconductor,
wherein the buffer layer is formed such that the lattice constant of the second semiconductor layers increases in a direction of lamination.
14. The semiconductor electronic device according to claim 13 , wherein each of the second semiconductor layers is formed of AlxGa1-xN (0<x≦1), and the aluminum composition (x) decreases in a direction of lamination.