Power light emitting diode and method with uniform current density operation
View Patent ↗A light emitting diode device has a bulk gallium and nitrogen containing substrate with an active region. The device has a lateral dimension and a thick vertical dimension such that the geometric aspect ratio forms a volumetric diode that delivers a nearly uniform current density across the range of the lateral dimension.
1. A light emitting device comprising:
a bulk III-Nitride substrate; and
epitaxial layers grown over said substrate comprising at least,
one n-doped layer;
one active region configured to emit light having a peak wavelength of 385-480 nm; and
one p-doped layer; and
wherein said substrate has a dopant concentration above 10 17 cm −3 and an absorption coefficient for said light no greater than 3 cm −1 .
2. The light emitting device of claim 1 , wherein said absorption coefficient is no greater than 2 cm −1 .
3. The light emitting device of claim 2 , wherein said absorption coefficient is no greater than 0.5 cm −1 .
4. The light emitting device of claim 2 , wherein said substrate has a threading dislocation density <10 8 cm −2 .
5. The light emitting device of claim 4 , wherein said substrate has a stacking fault density <10 4 cm −1 .
6. The light emitting device of claim 5 , wherein said substrate has a length greater than about 5 millimeters, and a Wurtzite structure, which is substantially free of other crystal structures.
7. The light emitting device of claim 1 , wherein said substrate and said epitaxial layers have a dislocation density <10 7 cm −2 .
8. The light emitting device of claim 7 , wherein said substrate and said epitaxial layers have a dislocation density <10 6 cm −2 .
9. The light emitting device of claim 1 , wherein said light emitting device has an external quantum efficiency of at least 50% at a power density of 2 watts/mm 2 and a junction temperature of 100 C°.
10. The light emitting device of claim 1 , further comprising a phosphor disposed over said active region to absorb at least a portion of said light.
11. The light emitting device of claim 1 , wherein said light emitting device is one of a light emitting diode or a laser diode.
12. The light emitting device of claim 1 , wherein said at least one active region comprises a total active layer thickness of at least 20 nm.
13. A method of operating a light emitting device comprising a bulk III-Nitride substrate, said method comprising:
driving said light emitting device at a power density of at least 2 watts/mm 2 to emit light having a peak wavelength of 385 nm to 480 nm;
wherein the absorption of said light by said substrate corresponds to an absorption coefficient no greater than 3 cm −1 and said substrate has a dopant concentration above 10 17 cm −3 .
14. The method of claim 13 , wherein, when driving said light emitting device at a power density of at least 2 watts/mm 2 , said light emitting device emits said light at an external quantum efficiency of at least 50%.
15. The method of claim 14 , wherein said light emitting device is driven continuously with a junction temperature greater than 100 degrees Celsius.
16. The method of claim 13 , wherein said absorption coefficient is no greater than 2 cm −1 .
17. The method of claim 16 , wherein said absorption coefficient is no greater than 0.5 cm −1 .
18. The method of claim 13 , wherein said substrate and said plurality of epitaxial layers comprise a dislocation density <10 7 cm −2 .
19. The method of claim 18 , wherein said substrate and said epitaxial layers comprise a dislocation density <10 6 cm −2 .
20. The method of claim 13 , wherein said at least one active region comprises a total active layer thickness of at least 20 nm.
21. The light emitting device of claim 1 , wherein said peak wavelength is 390-430 nm.
22. The light emitting device of claim 1 , wherein said substrate has a resistivity less than 0.05 Ohm-cm.
23. The method of claim 13 , wherein said peak wavelength is 390-430 nm.
24. The method of claim 13 , wherein said substrate has a resistivity less than 0.05 Ohm-cm.