Layered structure, semiconductor device including layered structure, and semiconductor system including semiconductor device
In a first aspect of a present inventive subject matter, a layered structure includes a first semiconductor layer including an ε-phase crystalline oxide semiconductor with a first composition, and a second semiconductor layer including an ε-phase crystalline oxide semiconductor with a second composition that is different from the first composition of the first semiconductor layer, and the second semiconductor layer is layered on the first semiconductor layer.
1. A layered structure, comprising:
a first semiconductor layer comprising a first ε-phase crystalline oxide semiconductor with a first composition; and
a second semiconductor layer comprising a second ε-phase crystalline oxide semiconductor with a second composition that is different from the first composition of the first semiconductor layer, the second semiconductor layer layered on the first semiconductor layer.
2. The layered structure of claim 1 , wherein
the first semiconductor layer comprises as a major metal component at least one selected from among gallium, indium and aluminum.
3. The layered structure of claim 1 , wherein
the first semiconductor layer comprises a mixed crystal, the mixed crystal comprising as a major metal component at least two selected from among gallium, indium and aluminum.
4. The layered structure of claim 1 , wherein
the first semiconductor layer comprises ε-Ga 2 O 3 .
5. The layered structure of claim 1 , wherein
the first semiconductor layer comprises a mixed crystal comprising ε-Ga 2 O 3 .
6. The layered structure of claim 1 , wherein
the second semiconductor layer comprises gallium as a major metal component.
7. The layered structure of claim 1 , wherein
the second semiconductor layer comprises ε-Ga 2 O 3 .
8. The layered structure of claim 1 , wherein
the second semiconductor layer comprises a mixed crystal comprising ε-Ga 2 O 3 .
9. The layered structure of claim 1 , wherein
the second semiconductor layer comprises aluminum.
10. The layered structure of claim 1 , wherein
the second semiconductor layer comprises (GaInAl) 2 O 3 .
11. The layered structure of claim 1 , further comprising:
three or more semiconductor layers comprising the first semiconductor layer and the second semiconductor layer.
12. The layered structure of claim 1 , further comprising:
a heterojunction between the first semiconductor layer and the second semiconductor layer.
13. The layered structure of claim 11 , further comprising:
a heterojunction between two semiconductor layers selected from among the three or more semiconductor layers.
14. The layered structure of claim 11 , further comprising:
an electrically insulating layer.
15. A semiconductor device, comprising:
a layered structure comprising:
a first semiconductor layer comprising a first ε-phase crystalline oxide semiconductor with a first composition; and
a second semiconductor layer comprising a second ε-phase crystalline oxide semiconductor with a second composition that is different from the first composition of the first semiconductor layer, the second semiconductor layer layered on the first semiconductor layer;
a first electrode electrically connected to the layered structure; and
a second electrode electrically connected to the layered structure.
16. The semiconductor device of claim 15 , wherein
the semiconductor device is a power device.
17. The semiconductor device of claim 16 , wherein
the semiconductor device is a semiconductor device with a high-frequency characteristic.
18. The semiconductor device of claim 16 , wherein
the semiconductor device is a high-electron-mobility transistor or a heterojunction bipolar transistor.
19. A system, comprising:
a circuit board; and
a semiconductor device comprising:
a layered structure comprising:
a first semiconductor layer comprising a first ε-phase crystalline oxide semiconductor with a first composition; and
a second semiconductor layer comprising a second ε-phase crystalline oxide semiconductor with a second composition that is different from the first composition of the first semiconductor layer, the second semiconductor layer layered on the first semiconductor layer;
a first electrode electrically connected to the layered structure; and
a second electrode electrically connected to the layered structure.