LED fabrication via ion implant isolation
View Patent ↗A semiconductor light emitting diode includes a semiconductor substrate, an epitaxial layer of n-type Group III nitride on the substrate, a p-type epitaxial layer of Group III nitride on the n-type epitaxial layer and forming a p-n junction with the n-type layer, and a resistive gallium nitride region on the n-type epitaxial layer and adjacent the p-type epitaxial layer for electrically isolating portions of the p-n junction. A metal contact layer is formed on the p-type epitaxial layer. In method embodiments disclosed, the resistive gallium nitride border is formed by forming an implant mask on the p-type epitaxial region and implanting ions into portions of the p-type epitaxial region to render portions of the p-type epitaxial region semi-insulating. A photoresist mask or a sufficiently thick metal layer may be used as the implant mask.
1. A method of manufacturing a light emitting diode comprising:
forming a second Group III nitride epitaxial region having a second conductivity type on a first Group III nitride epitaxial region having a first conductivity type, the first and second epitaxial regions forming a p-n junction;
forming a patterned metal contact layer on a top surface of the second epitaxial region, the metal contact layer being patterned to expose portions of the surface of the second epitaxial region; and
implanting ions into the second epitaxial region through the patterned exposed portions defined by the metal contact layer until the patterned exposed portions defined by the metal contact layer have a resistivity greater than 2000 ohm-centimeters.
2. The method according to claim 1 , further comprising:
applying a photoresist to the metal contact layer;
patterning the photoresist;
selectively etching portions of the metal contact layer to reveal portions of the surface of the second epitaxial region.
3. The method according to claim 2 , further comprising removing the photoresist prior to implanting ions into the second epitaxial region.
4. The method according to claim 2 , further comprising implanting ions into the second epitaxial region prior to removing the photoresist.
5. The method according to claim 2 further comprising depositing a passivation layer on exposed portions of the second epitaxial layer.
6. The method according to claim 5 comprising depositing a passivation layer selected from the group consisting of silicon dioxide, silicon nitride, insulating polymer and combinations thereof.
7. The method of claim 1 comprising forming an ohmic contact as the metal contact layer.
8. The method of claim 7 comprising forming the ohmic contact from the group consisting of platinum, nickel, gold, titanium, aluminum silver, and combinations thereof.
9. The method according to claim 1 comprising implanting nitrogen ions.
10. The method according to claim 9 comprising implanting monovalent nitrogen ions.
11. The method according to claim 9 comprising implanting divalent nitrogen ions.
12. The method according to claim 9 comprising implanting monovalent nitrogen ions at an energy of at least 20 keV and a dosage of at least 1×10 13 cm −2 .
13. The method according to claim 12 comprising implanting monovalent nitrogen ions at an energy of at least 125 keV and a dosage of at least 1.4×10 13 cm −2 .
14. The method according to claim 9 comprising implanting divalent nitrogen ions at an energy of at least 125 keV and a dosage of at least 2×10 13 cm −2 .
15. The method according to claim 1 comprising implanting ions selected from the group consisting of nitrogen, phosphorus, aluminum, helium, hydrogen and N 2 .
16. A method of passivating a device or its precursor that includes at least a p-type epitaxial layer, an ohmic contact layer on the p-type layer, and a bond pad on the ohmic contact, the method comprising:
masking a portion of the ohmic contact layer and all of the bond pad;
removing the remaining exposed ohmic metal contact layer from the epitaxial layer;
implanting the exposed portions of the epitaxial layer with ions sufficient to render the exposed portions highly resistive; and
removing the mask from the ohmic contact and the bond pad to thereby produce passivated portions of the p-type layer.
17. A method according to claim 16 comprising depositing the ohmic contact and the bond pad prior to the masking step.
18. A method according to claim 16 comprising masking the ohmic contact layer with a photoresist.