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 containing as a major component an ε-phase oxide semiconductor crystal; and a second semiconductor layer positioned on the first semiconductor layer and containing as a major component an oxide semiconductor crystal with a tetragonal crystal structure.
1. A layered structure, comprising:
a first semiconductor layer comprising as a major component an ε-phase oxide semiconductor crystal; and
a second semiconductor layer positioned on the first semiconductor layer and comprising as a major component an oxide semiconductor crystal with a tetragonal crystal structure.
2. The layered structure of claim 1 , wherein
the ε-phase oxide semiconductor crystal comprised in the first semiconductor layer comprises gallium.
3. The layered structure of claim 1 , wherein
the ε-phase oxide semiconductor crystal comprised in the first semiconductor layer comprises ε-Ga 2 O 3 .
4. The layered structure of claim 1 , wherein
the ε-phase oxide semiconductor crystal comprised in the first semiconductor layer comprises a mixed crystal comprising ε-Ga 2 O 3 .
5. The layered structure of claim 1 , wherein
the oxide semiconductor crystal with the tetragonal crystal structure comprised in the second semiconductor layer comprises tin.
6. The layered structure of claim 1 , wherein
the oxide semiconductor crystal with the tetragonal crystal structure comprised in the second semiconductor layer comprises SnO 2 .
7. The layered structure of claim 1 , wherein
the oxide semiconductor crystal with the tetragonal crystal structure comprised in the second semiconductor layer comprises a mixed crystal comprising SnO 2 .
8. The layered structure of claim 1 , further comprising:
three or more layers comprising the first semiconductor layer, the second semiconductor layer, and a third layer positioned on the first semiconductor layer.
9. The layered structure of claim 1 , further comprising:
three or more layers comprising the first semiconductor layer, the second semiconductor layer, and a third layer positioned on the second semiconductor layer.
10. The layered structure of claim 8 , further comprising:
a heterojunction between two semiconductor layers selected from among the three or more layers.
11. The layered structure of claim 8 , wherein
the third layer is an electrically insulating layer.
12. A semiconductor device, comprising:
a layered structure, comprising a first semiconductor layer that comprises an ε-phase oxide semiconductor crystal and a second semiconductor layer that is positioned on the first semiconductor layer and comprises an oxide semiconductor crystal with a tetragonal crystal structure; and
a heterojunction between the first semiconductor layer and the second semiconductor layer.
13. A semiconductor device, comprising:
a layered structure, comprising a first semiconductor layer that comprises an ε-phase oxide semiconductor crystal and a second semiconductor layer that is positioned on the first semiconductor layer and comprises an oxide semiconductor crystal with a tetragonal crystal structure;
a first electrode electrically connected to the layered structure; and
a second electrode electrically connected to the layered structure.
14. The semiconductor device of claim 13 , wherein
the semiconductor device is a transistor.
15. The semiconductor device of claim 13 , wherein
the semiconductor device is a semiconductor memory.
16. The semiconductor device of claim 13 , wherein
the semiconductor device is a light-emitting device or an opto-electronic device.
17. The semiconductor device of claim 13 , wherein
the semiconductor device is a solar cell.
18. The semiconductor device of claim 13 , wherein
the semiconductor device is a power device.
19. The semiconductor device of claim 13 , wherein
the semiconductor device has a high-frequency characteristic.
20. A system, comprising:
a circuit board; and
a semiconductor device, comprising a layered structure that comprises a first semiconductor layer comprising an ε-phase oxide semiconductor crystal, and a second semiconductor layer positioned on the first semiconductor layer and comprising an oxide semiconductor crystal with a tetragonal crystal structure, a first electrode electrically connected to the layered structure, and a second electrode electrically connected to the layered structure, the semiconductor device being electrically connected to the circuit board.