METHOD OF LIGHT EMITTING DIODE SIDEWALL PASSIVATION
A Light-Emitting Diode (LED) includes a light-emitting structure having a passivation layer disposed on vertical sidewalls across a first doped layer, an active layer, and a second doped layer that completely covers at least the sidewalls of the active layer. The passivation layer is formed by plasma bombardment or ion implantation of the light-emitting structure. It protects the sidewalls during subsequent processing steps and prevents current leakage around the active layer.
1 . A method of fabricating a LED, comprising:
providing a substrate;
forming a light-emitting structure on the substrate, wherein the light-emitting structure comprises a first doped layer doped with a first impurity of a first conductivity type, a second doped layer doped with a second impurity of a second conductivity type opposite to the first conductivity type, and an active layer between the first doped layer and the second doped layer;
etching the light-emitting structure to form a light-emitting mesa structure having an exposed sidewall; and
passivating the exposed sidewall of the light-emitting mesa structure to form a passivated portion within the light-emitting mesa structure.
2 . The method of claim 1 , wherein the passivating step comprises treating the exposed sidewall of the light-emitting mesa structure with ion implantation.
3 . The method of claim 1 , wherein the passivating step comprises treating the exposed sidewall of the light-emitting mesa structure with plasma.
4 . The method of claim 1 , wherein the passivating step is conducted at a substrate temperature less than 150 degree C.
5 . The method of claim 1 , wherein the passivated portion has a sidewise depth from the edge of the light-emitting mesa structure toward a center of the light-emitting mesa structure, and the sidewise depth is greater than 100 angstroms.
6 . The method of claim 5 , wherein the sidewise depth is between 100 and 500 angstroms.
7 . The method of claim 1 , further comprising forming a photoresist pattern covering a top surface of the light-emitting mesa structure and exposing the exposed sidewall of the light-emitting mesa structure before the passivating step.
8 . The method of claim 1 , further comprising:
forming a contact metal layer on the second doped layer; and
forming a bonding metal layer on the contact metal layer.
9 . The method of claim 8 , wherein the bonding metal layer having a smaller area than the light-emitting mesa structure.
10 . The method of claim 9 , wherein the bonding metal layer covers a sidewall of the contact metal layer.
11 . The method of claim 1 , further comprising dicing the substrate into a plurality of LED dies.
12 . The method of claim 11 , further comprising removing the substrate after the dicing step.
13 . The method of claim 12 , further comprising forming an undoped layer between the substrate and the first doped layer, wherein the step of removing the substrate comprises using laser to vaporize a portion of the undoped layer.
14 . The method of claim 1 , wherein the passivated portion within the light-emitting mesa structure comprises a passivated portion of the first doped layer, and a passivated portion of the second doped layer.
15 . The method of claim 1 , wherein the passivated portion includes argon, nitrogen, oxygen, or krypton.