Method of manufacturing a compound semiconductor substrate in a flattened growth substrate

1. A method of fabricating a semiconductor substrate, the method comprising:

growing a first compound semiconductor layer on a first surface of a substrate;

etching the first compound semiconductor layer using HF, KOH, or NaOH to make a first surface of the first compound semiconductor layer irregular;

forming cavities in the first compound semiconductor layer;

separating the first compound semiconductor layer from the first surface of the substrate;

flattening the first surface of the substrate after separating the first compound semiconductor layer; and

growing a second compound semiconductor layer on the flattened first surface of the substrate,

wherein:

forming the cavities comprises removing a patterned layer disposed on the first compound semiconductor layer; and

the patterned layer comprises an oxide region.

2. The method of claim 1 , wherein the flattening of the first surface of the substrate is performed using a reactive ion etching (RIE) process.

3. The method of claim 1 , wherein the substrate comprises GaN and sapphire.

4. The method of claim 3 , further comprising forming a third compound semiconductor layer on the first surface of the first compound semiconductor layer.

5. The method of claim 4 , wherein the first compound semiconductor layer comprises a different material than the third compound semiconductor layer.

6. The method of claim 4 , wherein the third compound semiconductor layer is formed at a temperature of over 1000 degrees Celsius.

7. The method of claim 4 , wherein the sapphire of the substrate is exposed by the cavities.

8. The method of claim 1 , wherein the cavities are formed at an interface between the substrate and the first compound semiconductor layer.

9. A method of fabricating a semiconductor substrate, the method comprising:

growing a first compound semiconductor layer on a first surface of a substrate;

etching the first compound semiconductor layer using HF, KOH, or NaOH to make a first surface of the first compound semiconductor layer irregular;

forming cavities in the first compound semiconductor layer;

separating the first compound semiconductor layer from the first surface of the substrate;

flattening the first surface of the substrate after separating the first compound semiconductor layer; and

growing a second compound semiconductor layer on the flattened first surface of the substrate,

wherein:

forming the cavities comprises removing a patterned layer disposed on the first compound semiconductor layer; and

the patterned layer comprises an oxide region and a metallic material.

10. The method of claim 9 , wherein the cavities are formed at an interface between the substrate and the first compound semiconductor layer.

11. A method of fabricating a semiconductor substrate, the method comprising:

growing a first compound semiconductor layer on a first surface of a substrate;

etching the first compound semiconductor layer using HF, KOH, or NaOH to make a first surface of the first compound semiconductor layer irregular;

forming cavities in the first compound semiconductor layer;

separating the first compound semiconductor layer from the first surface of the substrate;

flattening the first surface of the substrate after separating the first compound semiconductor layer;

growing a second compound semiconductor layer on the flattened first surface of the substrate;

forming a third compound semiconductor layer on the first surface of the first compound semiconductor layer; and

disposing a second substrate on the first compound semiconductor layer after the first compound semiconductor layer is separated from the substrate,

wherein the substrate comprises GaN and sapphire.

12. The method of claim 11 , wherein the first compound semiconductor layer comprises a different material than the third compound semiconductor layer.

13. The method of claim 11 , wherein the third compound semiconductor layer is formed at a temperature of over 1000 degrees Celsius.

14. The method of claim 11 , wherein the sapphire of the substrate is exposed by the cavities.

15. The method of claim 11 , wherein the cavities are formed at an interface between the substrate and the first compound semiconductor layer.

16. A method of fabricating a semiconductor substrate, the method comprising:

growing a first compound semiconductor layer on a first surface of a substrate;

etching the first compound semiconductor layer using HF, KOH, or NaOH to make a first surface of the first compound semiconductor layer irregular;

forming cavities in the first compound semiconductor layer;

separating the first compound semiconductor layer from the first surface of the substrate;

flattening the first surface of the substrate after separating the first compound semiconductor layer;

growing a second compound semiconductor layer on the flattened first surface of the substrate;

forming a third compound semiconductor layer on the first surface of the first compound semiconductor layer; and

disposing a second substrate on the first compound semiconductor layer after the first compound semiconductor layer is separated from the substrate,

wherein:

the substrate comprises GaN and sapphire; and

the second substrate is disposed on the third compound semiconductor layer.

17. The method of claim 16 , wherein the first compound semiconductor layer comprises a different material than the third compound semiconductor layer.

18. The method of claim 16 , wherein the third compound semiconductor layer is formed at a temperature of over 1000 degrees Celsius.

19. The method of claim 16 , wherein the sapphire of the substrate is exposed by the cavities.

20. The method of claim 16 , wherein the cavities are formed at an interface between the substrate and the first compound semiconductor layer.