Contact for a semiconductor light emitting device
View Patent ↗An AlGaInP light emitting device is formed as a thin, flip chip device. The device includes a semiconductor structure comprising an AlGaInP light emitting layer disposed between an n-type region and a p-type region. N- and p-contacts electrically connected to the n- and p-type regions are both formed on the same side of the semiconductor structure. The semiconductor structure is connected to a mount via the contacts. A growth substrate is removed from the semiconductor structure and a thick transparent substrate is omitted, such that the total thickness of semiconductor layers in the device is less than 15 μm some embodiments, less than 10 μm in some embodiments. The top side of the semiconductor structure may be textured.
1. A method comprising:
growing a semiconductor structure comprising an AlGaInP light emitting layer disposed between an n-type region and a p-type region over a growth substrate;
forming an n-contact electrically connected to the n-type region and a p-contact electrically connected to a p-type contact layer in the p-type region, wherein the n- and p-contacts are both disposed on a same side of the semiconductor structure and wherein at least one of the n- and p-contacts is reflective;
disposing a plurality of alloyed regions and a dielectric layer between the p-type contact layer and the p-contact;
connecting the semiconductor structure to a mount; and
after connecting the semiconductor structure to the mount, removing the growth substrate.
2. The method of claim 1 wherein removing the growth substrate comprises etching the growth substrate with an etch that terminates on an etch stop layer disposed between the semiconductor structure and the growth substrate.
3. The method of claim 2 wherein the etch stop layer is one of AlGaAs, InGaP, and AlGaInP.
4. The method of claim 2 wherein:
the etch stop layer is AlGaAs; and
a portion of the semiconductor structure in direct contact with the etch stop layer is AlGaInP.
5. The method of claim 1 wherein the n- and p-contacts are formed prior to connecting the semiconductor structure to the mount.
6. The method of claim 1 wherein:
the n-contact comprises Au and Ge; and
the n-contact is in direct contact with an n-type semiconductor layer.
7. The method of claim 1 wherein growing the semiconductor structure comprises growing a semiconductor wafer, the method further comprising dicing the semiconductor wafer into individual semiconductor structures prior to connecting the semiconductor structure to the mount.
8. The method of claim 1 wherein the p-contact is reflective and comprises Ag.
9. A method comprising:
growing a semiconductor structure comprising an AlGaInP light emitting layer disposed between an n-type region and a p-type region over a growth substrate;
forming an n-contact electrically connected to the n-type region and a metal p-contact electrically connected to and in direct contact with a p-type contact layer in the p-type region, wherein the n- and metal p-contacts are both disposed on a same side of the semiconductor structure and wherein at least one of the n- and metal p-contacts is reflective;
connecting the semiconductor structure to a mount;
after connecting the semiconductor structure to the mount, removing the growth substrate;
etching away portions of the p-type contact layer prior to forming the metal p-contact; and
disposing a dielectric between the metal p-contact and the p-type region in at least one region corresponding to an etched-away portion of the p-type contact layer.
10. The method of claim 9 wherein
at least a portion of the p-type contact layer is doped to a hole concentration of at least 5×10 18 cm −3 .
11. The method of claim 10 wherein p-type dopants are introduced into the p-type contact layer by one of introduction during growth of the p-type contact layer and diffusion from a vapor source after growth of a contact layer.
12. The method of claim 10 wherein portions of the p-type contact layer doped to a hole concentration of at least 5×10 18 cm −3 are aligned with openings in the dielectric layer.
13. The method of claim 10 wherein growing the semiconductor structure comprises growing the p-type contact layer by metal organic chemical vapor deposition at a growth rate less than 5000 Å per hour.
14. The method of claim 10 wherein the p-type contact layer is one of GaP, AlGaInP, and InGaP.
15. The method of claim 9 wherein the metal p-contact comprises Ag.
16. A method comprising:
growing a semiconductor structure comprising an AlGaInP light emitting layer disposed between an n-type region and a p-type region over a growth substrate;
growing a contact layer in the p-type region;
depositing a layer comprising a dopant over the contact layer, wherein the layer comprising a dopant is one of metal and dielectric;
annealing the semiconductor structure to form a p-type contact layer;
removing the layer comprising a dopant;
forming an n-contact electrically connected to the n-type region and a p-contact electrically connected to the p-type contact layer in the p-type region, wherein the n- and p-contacts are both disposed on a same side of the semiconductor structure and wherein at least one of the n- and p-contacts is reflective;
connecting the semiconductor structure to a mount; and
after connecting the semiconductor structure to the mount, removing the growth substrate.
17. The method of claim 16 further comprising depositing a dielectric layer with openings over the p-type contact layer, prior to depositing the layer comprising a the dopant.
18. The method of claim 16 wherein the p-contact comprises Ag.