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 semiconductor device made by the steps comprising:
(a) disposing epitaxial layers on a substrate, said substrate comprising bulk III-Nitride with n-doping above 1E17 cm-3, said epitaxial layers comprising at least one doped epi layer;
(b) disposing a second contact at least partially on said doped epi layer;
(c) treating a surface of said substrate by dry etching to define a n-GaN surface; and
(d) disposing an n-contact directly on said n-GaN surface, said n-contact being ohmic.
2. The device of claim 1 , wherein steps (a) and (b) are performed before steps (c) and (d).
3. The device of claim 2 , wherein said dry etching also defines at least one mesa on said substrate.
4. The device of claim 1 , wherein said dry etching involves using a chlorine-based chemistry.
5. The device of claim 1 , wherein said dry etching involves inductively-coupled plasma etching.
6. The device of claim 1 , further comprising, prior to step (a), n-doping said substrate above 1E17 cm-3.
7. The device of claim 1 , wherein said substrate is part of a wafer and steps (a)-(d) are wafer level, and further comprising (e) dicing said wafer to define said device.
8. The device of claim 1 , wherein second contact is a p contact.
9. The device of claim 8 , wherein the device is a light emitting diode (LED).
10. The device of claim 1 , wherein the substrate has a resistivity less than about 0.050 Ω-cm.
11. A semiconductor device having a height H and lateral dimension L, and comprising:
a bulk substrate comprising III-Nitride with an n-doping above 1E17 cm-3 and having an etched n-GaN surface;
an n-contact disposed directly on said n-GaN surface, said n-contact being ohmic;
epitaxial layers disposed on said substrate and comprising at least one doped epi layer; and
a second contact at least partially disposed on said doped epi layer.
12. The device of claim 11 , wherein H/L is at least 0.05, thereby facilitating current spreading through said epitaxial layers across the device.
13. The device of claim 12 , wherein said H/L is less than 10.
14. The device of claim 13 , wherein said H/L is greater than 0.2 and less than 2.
15. The device of claim 11 , wherein said substrate has a resistivity less than about 0.050 Ω-cm.
16. The device of claim 11 , wherein said substrate has a vertical resistance Rv and a lateral resistance Rl, wherein Rv/Rl is no greater than about 1.
17. The device of claim 11 , wherein the n-contact is metallic.
18. The device of claim 17 , wherein said n-contact comprises one of Ti/Al/Ni/Au or combinations of these metals, or Ti/Al/Ti/Au or combinations of these metals, and has a thickness ranging from about 100 nm to about 7 μm.
19. The device of claim 11 , wherein said second contact is one of a metallic contact or a transparent contact.
20. The device of claim 11 , wherein the device is one of a lateral device, a vertical device, or a flip-chip device.
21. The device of claim 11 , wherein second contact is a p contact.
22. The device of claim 11 , wherein the device is a light emitting diode (LED).
23. The device of claim 11 , wherein said bulk substrate comprises one of GaN, InGaN, or AlGaN.
24. The device of claim 23 , wherein said bulk substrate has a polar orientation.
25. The device of claim 11 , wherein said epitaxial layers have a thickness ranging from about 1 nm to about 10 um and a dopant concentration ranging from about 1E16 cm-3 to about 5E20 cm-3.