LED with conductively joined bonding structure
View Patent ↗An LED is disclosed that includes a conductive submount, a bond pad having a total volume less than 3×10 −5 mm 3 conductively joined to the submount, a first ohmic contact on the bond pad opposite from the submount, an epitaxial region comprising at least a p-type layer and an n-type layer on the first ohmic contact, and an electrode to the epitaxial region opposite from the first ohmic contact.
1. An LED chip comprising:
a conductive submount ( 24 );
a bond pad ( 31 ) having a total volume less than 3×10 −5 mm 3 conductively joined to said submount;
a first ohmic contact ( 18 ) on said bond pad opposite from said submount;
an epitaxial region ( 12 ) comprising at least a p-type layer ( 16 ) and an n-type layer ( 14 ) on said first ohmic contact; and
a second ohmic contact ( 22 ) to said epitaxial region opposite from said first ohmic contact.
2. An LED chip as recited in claim 1 , wherein said bond pad comprises a metal solder.
3. An LED chip as recited in claim 1 , wherein said bond pad comprises Au.
4. An LED chip as recited in claim 1 , wherein said bond pad is selected from the group consisting of Au/Sn, Pb/Sn, Sn and Sn/Ag.
5. An LED chip as recited in claim 1 , wherein said bond pad has a total volume less than about 2.5×10 −5 mm 3 .
6. An LED chip as recited in claim 1 , wherein said bond pad is formed in the shape of a parallelepiped.
7. An LED chip as recited in claim 6 wherein said bond pad has a generally square periphery.
8. An LED chip as recited in claim 6 wherein said epitaxial region has a width of about 250 μm or more, and wherein said bond pad has a height of about 1.2 μm or less and a width of about 150 μm or less.
9. An LED chip as recited in claim 1 wherein said bond pad is formed in the shape of a cylinder.
10. An LED chip as recited in claim 9 , wherein said epitaxial region has a width of about 250 μm of more, and wherein said bond pad has a height of about 2 μm or less and a diameter less than one half the width of said epitaxial layer.
11. An LED chip as recited in claim 10 , wherein said bond pad has a diameter of about 120 μm or less.
12. An LED chip as recited in claim 1 wherein said bond pad is formed in the shape of a polyhedron having opposing parallel faces and a star-shaped periphery.
13. An LED chip as recited in claim 12 , wherein the distance from an edge of said bond pad to an edge of said epitaxial region is at least about 50 μm.
14. An LED chip according to claim 1 wherein the shear strength between said bond pad and said submount exceeds 140 g.
15. An LED chip according to claim 14 wherein the shear strength between said bond pad and said submount is between about 300 and 600 g.
16. An LED chip as recited in claim 14 , wherein said epitaxial region comprises a perimeter and said bond pad comprises a metal solder that is located entirely within said perimeter of said epitaxial region.
17. An LED chip as recited in claim 14 , wherein the total volume of said bond pad is less than the space volume between said first ohmic contact and said submount.
18. An LED chip as recited in claim 1 wherein said epitaxial layers are selected from the group consisting of GaN, AlGaNInP, InGaAs, AlGaAs and SiC.