Light emitting diodes including optically matched substrates
View Patent ↗Light emitting diodes include a diode region comprising a gallium nitride-based n-type layer, an active region and a gallium nitride-based p-type layer. A substrate is provided on the gallium nitride-based n-type layer and optically matched to the diode region. The substrate has a first face remote from the gallium nitride-based n-type layer, a second face adjacent the gallium nitride-based n-type layer and a sidewall therebetween. At least a portion of the sidewall is beveled, so as to extend oblique to the first and second faces. A reflector may be provided on the gallium nitride-based p-type layer opposite the substrate. Moreover, the diode region may be wider than the second face of the substrate and may include a mesa remote from the first face that is narrower than the first face and the second face.
1. A light emitting diode comprising:
a diode region comprising a gallium nitride-based n-type layer, an active region and a gallium nitride-based p-type layer;
a substrate on the gallium nitride-based n-type layer and optically matched to the diode region, the substrate having a first face remote from the gallium nitride-based n-type layer, a second face adjacent the gallium nitride-based n-type layer and a sidewall therebetween, at least a portion of the sidewall being beveled so as to extend oblique to the first and second faces;
a reflector on the gallium nitride-based p-type layer remote from the substrate;
a first bonding layer on the reflector remote from the substrate;
an ohmic contact on the gallium nitride-based n-type layer remote from the substrate; and
a second bonding layer on the ohmic contact remote from the substrate,
wherein the first face further comprises two intersecting grooves therein that form an X-shape in plan view.
2. A light emitting diode according to claim 1 wherein the ohmic contact comprises reflective material.
3. A light emitting diode according to claim 1 wherein the substrate is directly on the gallium nitride-based n-type layer to define an interface therebetween, wherein the interface is planar.
4. A light emitting diode according to claim 1 wherein the first face of the substrate is textured.
5. A light emitting diode according to claim 1 wherein the substrate comprises silicon carbide.
6. A light emitting diode according to claim 1 further comprising a first barrier layer between the reflector and the first bonding layer and a second barrier layer between the ohmic contact and the second bonding layer.
7. A light emitting diode according to claim 1 wherein the gallium nitride-based n-type layer includes a thick portion that is on the active region and a thin portion that is offset from the active region and wherein the ohmic contact is on the thin portion, remote from the substrate.
8. A light emitting diode according to claim 1 wherein the first and second bonding layers are coplanar.
9. A light emitting diode according to claim 8 :
wherein the ohmic contact comprises reflective material;
wherein the substrate is directly on the gallium nitride-based n-type layer to define an interface therebetween, wherein the interface is planar; and
wherein the substrate comprises silicon carbide.
10. A light emitting diode according to claim 9 further comprising a first barrier layer between the reflector and the first bonding layer and a second barrier layer between the ohmic contact and the second bonding layer.
11. A light emitting diode according to claim 9 wherein the gallium nitride-based n-type layer includes a thick portion that is on the active region and a thin portion that is offset from the active region and wherein the ohmic contact is on the thin portion, remote from the substrate.
12. A light emitting diode comprising:
a substrate having a first face and a second face that is wider than the first face; and
a semiconductor diode region on the second face, remote from the first face, that is optically matched to the substrate and that is wider than the second face, so that a portion of the semiconductor diode region overhangs beyond a widest portion of the second face,
wherein the substrate includes at least one groove in the first face and a beveled sidewall between the first and second faces.
13. A light emitting diode according to claim 12 wherein the diode region includes a first portion adjacent the second face that is wider than the second planar face and a second portion remote from the second face that is narrower than the first portion to define a mesa.
14. A light emitting diode according to claim 13 wherein the second portion is also narrower than the second face.
15. A light emitting diode according to claim 14 further comprising a contact on the mesa remote from the first portion that is narrower than the mesa.
16. A light emitting diode according to claim 14 wherein the second portion is also at least as narrow as the first face.
17. A light emitting diode according to claim 12 :
wherein the substrate is on the diode region and has a sidewall between the first face and the second face, at least a portion of the sidewall being beveled so as to extend oblique to the first and second faces.
18. A light emitting diode according to claim 17 wherein the substrate is directly on the diode region to define an interface therebetween, wherein the interface is planar.
19. A light emitting diode according to claim 12 wherein the substrate comprises silicon carbide.
20. A light emitting diode according to claim 13 :
wherein the diode region comprises an active region; and
wherein the active region is confined to the mesa.
21. A light emitting diode comprising:
a diode region comprising an n-type layer, an active region and a p-type layer;
an anode contact on the p-type layer; and
a cathode contact on the n-type layer,
wherein the anode contact and the cathode contact are coplanar and the cathode contact is thicker than the anode contact; and
a substrate having an inner face on the n-type layer remote from the coplanar anode and cathode contacts, an outer face and a beveled sidewall between the inner face and the outer face,
wherein the substrate includes at least one groove in the outer face.
22. A light emitting diode according to claim 21 wherein the coplanar anode and cathode contacts are configured for flip-chip mounting of the light emitting diode.
23. A light emitting diode according to claim 21 in combination with a mounting support, wherein the coplanar anode and cathode contacts are mounted on the mounting support.
24. A light emitting diode according to claim 23 wherein the coplanar anode and cathode contacts are mounted directly on the mounting support.
25. A light emitting diode according to claim 23 in further combination with a dome that extends from the mounting support to surround the light emitting diode.
26. A light emitting diode comprising:
a substrate having a first face and a second face that is wider than the first face;
a semiconductor diode region on the second face, remote from the first face, that is optically matched to the substrate; and
a pair of electrical contacts for the diode region that are both on the diode region remote from the substrate;
wherein the substrate includes at least two intersecting grooves in the first face that form an X-shape in plan view, and a beveled sidewall between the first and second faces.
27. A light emitting diode according to claim 26 wherein the pair of electrical contacts have coplanar outer surfaces.
28. A light emitting diode according to claim 26 wherein the pair of electrical contacts comprise reflective electrical contacts.
29. A light emitting diode according to claim 12 wherein the at least one groove comprises two intersecting grooves that form an X-shape in plan view.
30. A light emitting diode according to claim 21 wherein the at least one groove comprises two intersecting grooves that form an X-shape in plan view.