LED having vertical structure and method for fabricating the same
A light emitting diode (LED) having a vertical structure and a method for fabricating the same. The light emitting diode (LED) having a vertical structure includes a support layer; a first electrode formed on the support layer; a plurality of semiconductor layers formed on the first electrode; a conductive semiconductor layer formed on the plurality of semiconductor layers, and provided with an outer surface having a tilt angle of a designated degree; and a second electrode formed on the conductive semiconductor layer.
1. A method for fabricating a light emitting diode, comprising:
forming a mask layer on a surface of a substrate;
forming a conductive semiconductor layer on the mask layer, wherein the conductive semiconductor layer is formed on the surface of the substrate to have a side surface having a tilt angle with respect to the surface of the substrate, and wherein the tilt angle is configured to improve the light extraction efficiency of the diode;
forming a semiconductor structure comprising a first-type semiconductor layer, an active layer, and a second-type semiconductor layer on the conductive semiconductor layer, wherein the conductive semiconductor layer is thicker than the semiconductor structure to serve as a template for growing the semiconductor structure;
forming a first electrode on the semiconductor structure;
forming a support layer on the first electrode;
separating the substrate; and
forming a second electrode on a surface of the conductive semiconductor layer.
2. The method according to claim 1 , wherein the mask layer is formed on a buffer layer.
3. The method according to claim 2 , wherein the buffer layer comprises a gallium nitride-based semiconductor (Al x In y Ga 1-x-y N: 0≦(x,y)≦1) layer.
4. The method according to claim 1 , wherein forming the mask layer comprises:
forming a dielectric layer on the substrate; and
patterning the dielectric layer into a circular or polygonal shape.
5. The method according to claim 4 , wherein a horizontal sectional shape of the conductive semiconductor layer is substantially the same as the circular or polygonal shape of the dielectric layer.
6. The method according to claim 4 , wherein a horizontal sectional shape of the conductive semiconductor layer has more sides than the polygonal shape of the dielectric layer.
7. The method according to claim 4 , wherein the dielectric layer comprises silicon oxide or silicon nitride.
8. The method according to claim 1 , wherein the conductive semiconductor layer comprises a conductive GaN layer having a thickness of 1˜300 μm.
9. The method according to claim 1 , wherein the conductive semiconductor layer is formed by a hydride vapor phase epitaxy (HVPE) method.
10. The method according to claim 1 , wherein the substrate comprises a GaN substrate formed by a hydride vapor phase epitaxy (HVPE) method.
11. The method according to claim 1 , wherein the semiconductor structure is formed by a metal organic chemical vapor deposition (MOCVD) method.
12. The method according to claim 1 , wherein separating the substrate is performed by a laser lift-off process or a wet etching process.
13. The method according to claim 1 , wherein the first electrode comprises:
an electrical contact; and
a reflective electrode on the electrical contact.
14. The method according to claim 1 , wherein the first electrode comprises a reflective ohmic electrode.
15. The method according to claim 1 , wherein the tilt angle of the conductive semiconductor layer is an angle of the side surface with respect to the surface of the conductive semiconductor layer, which is in the range of 35˜65°.
16. The method according to claim 1 , wherein at least one of the support layer, the first electrode, the semiconductor structure, the conductive semiconductor layer, and the second electrode has a horizontal sectional shape of a polygon, which is more than a rectangle.
17. The method according to claim 1 , wherein the support layer comprises at least one of a silicon (Si) substrate, a gallium arsenide (GaAs) substrate, a germanium (Ge) substrate, a metal substrate including nickel (Ni) or copper (Cu), and a substrate including metal.
18. The method according to claim 1 , wherein the semiconductor structure is in direct contact with the conductive semiconductor layer.
19. The method according to claim 1 , further comprising forming a seed metal on the first electrode.
20. The method according to claim 1 , wherein a side surface of the semiconductor structure has a tilt angle different from the tilt angle of the conductive semiconductor layer.
21. The method according to claim 1 , wherein the tilt angle of the conductive semiconductor layer is an angle of the side surface with respect to the surface of the conductive semiconductor layer, which is in the range of 53˜56°.
22. The method according to claim 1 , wherein the tilt angle of the conductive semiconductor layer is configured such that the surface of the conductive semiconductor layer is larger than a surface of the conductive semiconductor layer contacting the semiconductor structure.
23. The method according to claim 1 , wherein the side surface of the conductive semiconductor layer is configured to reduce a possibility of internal total reflection of the light emitted from the semiconductor structure, thereby improving the light extraction efficiency of the diode.
24. The method according to claim 1 , wherein the conductive semiconductor layer is configured to emit the light from the semiconductor structure through the surface of the conductive semiconductor layer.