Light emitting diode having an insulating substrate

1. A light emitting diode comprising:

an insulating substrate;

a semiconductor stack positioned over the insulating substrate, the semiconductor stack comprising a first surface and a second surface, a distance between the first surface and the insulating substrate is greater than a distance between the second surface and the insulating substrate;

a reverse-tunneling layer over the first surface, the reverse-tunneling layer being a gallium nitride (GaN) based semiconductor;

a first transparent ohmic contact electrode positioned directly on the reverse-tunneling layer, the first transparent ohmic contact electrode comprising an oxide; and

a second transparent ohmic contact electrode positioned over the second surface.

2. The light emitting diode of claim 1 , wherein the insulating substrate comprises sapphire, and the first transparent ohmic contact electrode and the second transparent ohmic contact electrode comprise the same non-metal material.

3. The light emitting diode of claim 1 , wherein the first transparent ohmic contact electrode or the second transparent ohmic contact electrode comprises at least one selected from a group comprising indium tin oxide (ITO) and cadmium tin oxide (CTO).

4. A light emitting diode comprising:

an insulating substrate;

a buffer layer positioned on the insulating substrate;

an n + -type contact layer positioned on the buffer layer, the contact layer comprising a first surface and a second surface;

an n-type cladding layer positioned on the first surface of the n + -type contact layer;

a light-emitting layer positioned on the n-type cladding layer;

a p-type cladding layer positioned on the light-emitting layer;

a p-type contact layer positioned on the p-type cladding layer;

an n + -type reverse-tunneling layer positioned on the p-type contact layer;

a p-type transparent ohmic contact electrode positioned on the n + -type reverse-tunneling layer; and

an n-type transparent ohmic contact electrode positioned on the second surface of the n + -type contact layer;

wherein the p-type transparent ohmic contact electrode and the n-type transparent ohmic contact electrode comprise the same materials.

5. The light emitting diode of claim 4 , wherein the insulating substrate comprises sapphire.

6. The light emitting diode of claim 4 , wherein the p-type transparent ohmic contact electrode and the n-type transparent ohmic contact electrode are made of at least one selected from a group comprising indium tin oxide and cadmium tin oxide.

7. A light emitting diode comprising:

an insulating substrate;

a semiconductor light emitting stack positioned over the insulating substrate, the semiconductor light emitting stack comprising a first surface and a second surface, a distance between the first surface and the insulating substrate is greater than a distance between the second surface and the insulating substrate;

a reverse-tunneling layer over the first surface, the reverse-tunneling layer being a gallium nitride (GaN) based semiconductor;

a first non-metal transparent ohmic contact electrode positioned over the reverse-tunneling layer; and

a second non-metal transparent ohmic contact electrode positioned over the second surface,

wherein the first non-metal transparent ohmic contact electrode and the second non-metal transparent ohmic contact electrode comprise the same oxide material.

8. The light emitting diode of claim 7 , wherein the first non-metal transparent ohmic contact electrode and the second non-metal transparent ohmic contact electrode comprise at least one selected from a group comprising indium tin oxide (ITO) and cadmium tin oxide (CTO).

9. A light emitting diode comprising:

an insulating substrate;

a semiconductor stack positioned over the insulating substrate, the semiconductor stack comprising a first surface and a second surface, a distance between the first surface and the insulating substrate is greater than a distance between the second surface and the insulating substrate;

a reverse-tunneling layer, which is a gallium nitride (GaN) based semiconductor that has a carrier concentration of approximately 1.5×10 20 cm −3 , over the first surface;

a first transparent ohmic contact electrode directly on the reverse-tunneling layer, the first transparent ohmic contact electrode comprising an oxide; and

a second transparent ohmic contact electrode over the second surface.

10. The light emitting diode of claim 9 , wherein the reverse-tunneling layer has a thickness of approximately 20 angstroms.

11. A light emitting diode comprising:

an insulating substrate;

a semiconductor stack positioned over the insulating substrate, the semiconductor stack comprising a first surface and a second surface, a distance between the first surface and the insulating substrate is greater than a distance between the second surface and the insulating substrate;

a reverse-tunneling layer over the first surface, the reverse-tunneling layer being a gallium nitride (GaN) based semiconductor; and

a first transparent ohmic contact electrode directly on the reverse-tunneling layer, the first transparent ohmic contact electrode comprising an oxide.

12. A light emitting diode comprising:

an insulating substrate;

a buffer layer positioned on the insulating substrate;

an n-type contact layer positioned on the buffer layer, the contact layer comprising a first surface and a second surface;

an n-type cladding layer positioned on the first surface of the n-type contact layer;

a light-emitting layer positioned on the n-type cladding layer;

a p-type cladding layer positioned on the light-emitting layer;

a p-type contact layer positioned on the p-type cladding layer;

an n + -type reverse-tunneling layer positioned on the p-type contact layer;

a p-type transparent ohmic contact electrode positioned on the n + -type reverse-tunneling layer; and

an n-type transparent ohmic contact electrode positioned on the second surface of the n + -type contact layer;

wherein the p-type transparent ohmic contact electrode and the n-type transparent ohmic contact electrode comprise the same materials.

13. The light emitting diode of claim 12 , wherein the insulating substrate comprises sapphire.

14. The light emitting diode of claim 12 , wherein the p-type transparent ohmic contact electrode and the n-type transparent ohmic contact electrode are made of at least one selected from a group comprising indium tin oxide and cadmium tin oxide.