Semiconductor thin film structures and electronic devices including the same
A semiconductor thin film structure may include a substrate, a buffer layer on the substrate, and a semiconductor layer on the buffer layer, such that the buffer layer is between the semiconductor layer and the substrate. The buffer layer may include a plurality of unit layers. Each unit layer of the plurality of unit layers may include a first layer having first bandgap energy and a first thickness, a second layer having second bandgap energy and a second thickness, and a third layer having third bandgap energy and a third thickness. One layer having a lowest bandgap energy of the first, second, and third layers of the unit layer may be between another two layers of the first, second, and third layers of the unit layer.
1. A semiconductor thin film structure, comprising:
a substrate;
a buffer layer on the substrate, the buffer layer including
a plurality of unit layers, each unit layer of the plurality of unit layers including
a first layer having first bandgap energy and a first thickness,
a second layer having second bandgap energy and a second thickness, and
a third layer having third bandgap energy and a third thickness,
wherein one layer having a lowest bandgap energy of the first, second, and third layers of the unit layer is between two other layers of the first, second, and third layers of the unit layer,
wherein,
the first layer of the unit layer is proximate to the substrate in relation to the second layer and the third layer of the unit layer,
the third layer of the unit layer is distal to the substrate in relation to the first layer and the second layer of the unit layer,
the second thickness is smaller than the first thickness, and
the second thickness is smaller than the third thickness; and
a semiconductor layer on the buffer layer, such that the buffer layer is between the semiconductor layer and the substrate.
2. The semiconductor thin film structure of claim 1 , wherein
the first layer is configured to adjust warpage of the substrate.
3. The semiconductor thin film structure of claim 1 , wherein
the first bandgap energy is higher than the second bandgap energy, and
the first bandgap energy is lower than the third bandgap energy.
4. The semiconductor thin film structure of claim 1 , wherein
the first thickness is greater than the second thickness, and
the first thickness is greater than the third thickness.
5. The semiconductor thin film structure of claim 1 , wherein
a sum of the first thickness and the second thickness is in a range of about 200% of the third thickness to about 1500% of the third thickness.
6. The semiconductor thin film structure of claim 5 , wherein
the sum of the first thickness and the second thickness is in a range of about 400% of the third thickness to about 900% of the third thickness.
7. The semiconductor thin film structure of claim 1 , wherein
the third layer is configured to at least partially inhibit a current flow in the buffer layer in a thickness direction of the buffer layer.
8. The semiconductor thin film structure of claim 1 , wherein
a magnitude of a difference between the second bandgap energy and the third bandgap energy is equal to or greater than about 200% of a magnitude of a difference between the second bandgap energy and the first bandgap energy.
9. The semiconductor thin film structure of claim 1 , wherein
the first layer includes Al y Ga (1-y) N(0<w≤0.5).
10. The semiconductor thin film structure of claim 9 , wherein
the second layer includes Al y Ga (1-y) N(0<y≤0.1, y<w).
11. The semiconductor thin film structure of claim 10 , wherein
the third layer includes Al x Ga (1-x) N (w<x≤1) .
12. The semiconductor thin film structure of claim 11 , wherein
the third layer includes Al x Ga (1-x) N(0.7≤x≤1).
13. The semiconductor thin film structure of claim 11 , wherein
each unit layer further includes
a fourth layer on the third layer of the unit layer, the fourth layer having a fourth bandgap energy, the fourth bandgap energy having a variable magnitude in a thickness direction of the fourth layer, such that a magnitude of the fourth bandgap energy varies in the thickness direction of the fourth layer between a magnitude of the third bandgap energy and a magnitude of the first bandgap energy.
14. The semiconductor thin film structure of claim 13 , wherein,
the fourth layer includes Al z Ga (1-z) N,
z has a different value depending on a position of the fourth layer in a thickness direction of the buffer layer, and
an average value z(average) of the z value satisfies y<w<z(average)<x.
15. The semiconductor thin film structure of claim 11 , wherein
each unit layer further includes
a fourth layer between the second layer of the unit layer and the third layer of the unit layer, the fourth layer having a fourth bandgap energy, the fourth bandgap energy having a variable magnitude in a thickness direction of the fourth layer, such that a magnitude of the fourth bandgap energy varies in the thickness direction of the fourth layer between a magnitude of the second bandgap energy and a magnitude of the third bandgap energy.
16. The semiconductor thin film structure of claim 15 , wherein,
the fourth layer includes Al v Ga (1-v) N,
v has a different value depending on a position of the fourth layer in a thickness direction of the buffer layer, and
an average value v(average) of the v value satisfies y<w<v(average)<x.
17. The semiconductor thin film structure of claim 9 , wherein
the second layer includes In y Ga (1-y) N(0≤y≤0.2), and
the third layer includes AlN.
18. The semiconductor thin film structure of claim 1 , wherein
the first layer includes GaN.
19. The semiconductor thin film structure of claim 18 , wherein
the second layer includes InGaN, and
the third layer includes AlN.
20. The semiconductor thin film structure of claim 1 , wherein
each unit layer further includes
a fourth layer on the third layer of the unit layer, the fourth layer having a fourth bandgap energy, the fourth bandgap energy having a variable magnitude in a thickness direction of the fourth layer, such that a magnitude of the fourth bandgap energy varies in the thickness direction of the fourth layer between a magnitude of the third bandgap energy and a magnitude of the first bandgap energy.
21. The semiconductor thin film structure of claim 1 , wherein each unit layer further includes
a fourth layer between the second layer of the unit layer and the third layer of the unit layer, the fourth layer having a fourth bandgap energy, the fourth bandgap energy having a variable magnitude in a thickness direction of the fourth layer, such that a magnitude of the fourth bandgap energy varies in the thickness direction of the fourth layer between a magnitude of the second bandgap energy and a magnitude of the third bandgap energy.
22. The semiconductor thin film structure of claim 1 , wherein
each layer of the first layer, the second layer, and the third layer includes Al, In, Ga, and N, and includes a quaternary nitride having a different composition ratio.
23. A semiconductor thin film structure, comprising:
a substrate;
a buffer layer on the substrate, the buffer laver including
a plurality of unit layers, each unit layer of the plurality of unit layers including
a first layer having first bandgap energy and a first thickness,
a second layer having second bandgap energy and a second thickness, and
a third layer having third bandgap energy and a third thickness,
wherein one layer having a lowest bandgap energy of the first, second, and third lavers of the unit layer is between two other layers of the first, second, and third lavers of the unit layer; and
a semiconductor layer on the buffer layer, such that the buffer layer is between the semiconductor layer and the substrate,
wherein an average value of bandgap energy of layers included in each unit layer of the plurality of unit layers decreases in a direction from the substrate toward the semiconductor layer.
24. An electronic device, comprising:
the semiconductor thin film structure of claim 1 ;
a source electrode and a drain electrode which are in contact with separate, respective sides of the semiconductor layer and are isolated from direct contact with each other; and
a gate electrode on the semiconductor layer.
25. The electronic device of claim 24 , further comprising:
a depletion layer between the semiconductor layer and the gate electrode.
26. The electronic device of claim 25 , wherein
the depletion layer includes p-GaN.