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 diode (LED) having
a bulk gallium- and nitrogen-containing substrate;
an epitaxial stack comprising an n-type layer, an active region, and a p-type layer disposed on said substrate;
an electrical n-contact contacting said n-type layer;
an electrical p-contact contacting said p-type layer; and
wherein at least one of said substrate, epitaxial stack, said n-contact, and said p-contact is configured to reduce current crowding such that light emitted from the active region has an emission intensity varying no more than +/−20% across the active region at an input power per active region area greater than 2 watts/mm2.
2. The LED of claim 1 , wherein the substrate is a bulk GaN substrate.
3. The LED of claim 1 , wherein the light emitting diode is configured to emit light from the active region having an emission intensity varying no more than +/−10% across the active region at an input power per active region area greater than 2 watts/mm2.
4. The LED of claim 1 , wherein the light emitting diode is configured to emit light from the active region having an emission intensity varying no more than +/−20% across the active region at an input power per active region area greater than 5 watts/mm2.
5. The LED of claim 4 , wherein the light emitting diode is configured to emit light from the active region having an emission intensity varying no more than +/−10% across the active region, at an input power per active region area greater than 5 watts/mm2.
6. The LED of claim 1 , wherein the LED is a flip-chip LED.
7. The LED of claim 1 , wherein the LED emits light with a wavelength in a range of 390 nm to 480 nm.
8. The LED of claim 1 , wherein the LED is characterized by a longest lateral dimension and a thickness, such that the ratio of the longest lateral dimension to the thickness is from 0.05 to 10.
9. The LED of claim 8 , wherein the ratio of the longest lateral dimension to the thickness is from 0.2 to 5.
10. The LED of claim 1 , wherein the substrate has a doping density above 1E17.
11. The LED of claim 1 , wherein the substrate is characterized by a resistivity less than 0.5 Ohm·cm.
12. The LED of claim 11 , wherein the substrate is characterized by a resistivity less than 0.05 Ohm·cm.
13. The LED of claim 1 , wherein the LED emits substantially white light with a CRI above 75.
14. The LED of claim 1 , wherein said substrate has a semipolar or non-polar orientation.
15. The LED of claim 1 , wherein said substrate has a polar orientation.
16. The LED of claim 1 , wherein the LED has a base area, and the active region covers at least 80% of the base area.
17. The LED of claim 16 , wherein the active region covers at least 90% of the base area.
18. The LED of claim 16 , wherein the base area is at least about 250 um×250 um.
19. The LED of claim 1 , wherein the thickness of the LED is at least about 160 um.
20. The LED of claim 1 , wherein the LED has an EQE of at least 50 at an input power per active region area greater than 2 watts/mm2.