Method of fabricating gallium nitride based semiconductor device

1. A method of fabricating a gallium nitride (GaN) based semiconductor device, the method comprising:

growing GaN based semiconductor layers on a first surface of a GaN substrate, wherein the GaN based semiconductor layers comprise a semiconductor stack and have a dislocation density of about 5×10 6 /cm 2 or less;

separating at least a first portion of the GaN substrate from the semiconductor stack using a wire cutting technique to decrease a thickness of the GaN substrate; and

removing a second portion of the GaN substrate remaining on the semiconductor stack using a laser lift-off.

2. The method of claim 1 , further comprising:

forming a support substrate on the semiconductor stack before separating the first portion of the GaN substrate.

3. The method of claim 1 , further comprising:

forming, before forming the semiconductor stack, a sacrificial layer between the GaN substrate and the semiconductor stack, the sacrificial layer having a bandgap narrower than a bandgap of the GaN substrate.

4. The method of claim 1 , further comprising:

growing a GaN based layer on the first portion of the GaN substrate after the first portion is separated from the semiconductor stack.

5. The method of claim 1 , wherein the semiconductor stack comprises:

a first conductivity type GaN based semiconductor layer;

a second conductivity type GaN based semiconductor layer; and

an active layer disposed between the first and second conductivity type GaN based semiconductor layers,

wherein the GaN based semiconductor device comprises a light emitting diode.

6. The method of claim 3 , wherein the sacrificial layer comprises indium nitride or indium gallium nitride.

7. A method of fabricating a gallium nitride (GaN) based semiconductor device, the method comprising:

growing GaN based semiconductor layers on a first surface of a GaN substrate, wherein the GaN based semiconductor layers comprise a semiconductor stack and have a dislocation density of about 5×10 6 /cm 2 or less;

forming a sacrificial layer between the GaN based semiconductor layers and the GaN substrate;

separating at least a first portion of the GaN substrate from the semiconductor stack using a wire cutting technique to decrease a thickness of the GaN substrate; and

separating a second portion of the GaN substrate from the semiconductor stack using a laser lift-off technique,

wherein the sacrificial layer has a bandgap narrower than a bandgap of the GaN substrate, and the sacrificial layer is configured to absorb light emitted by the laser.

8. A method of fabricating a device, the method comprising:

forming a sacrificial layer on a GaN substrate;

growing at least one GaN based semiconductor layer on the sacrificial layer, wherein the GaN based semiconductor layer has a dislocation density of about 5×10 6 /cm 2 or less;

separating, using a wire, a first portion of the GaN substrate from a remaining portion of the GaN substrate to decrease a thickness of the GaN substrate;

removing the sacrificial layer and the remaining portion of the GaN substrate by using a laser.

9. The method of claim 8 , wherein the sacrificial layer comprises indium nitride or indium gallium nitride.