Vertical nitride based semiconductor light emitting device having improved light extraction efficiency
View Patent ↗The invention provides a nitride semiconductor light emitting device. In the invention, a first conductivity-type nitride semiconductor layer is formed on a conductive substrate having light transmissibility. An active layer is formed on the first conductivity-type nitride semiconductor layer. Also, a second conductivity-type nitride semiconductor layer is formed on the active layer. Further, a conductive light scattering layer made of a conductive material is formed on an underside of the substrate. The conductive light scattering layer has light transmissibility of 70% or more and has a rough pattern formed on an outer surface to scatter light.
1. A vertical nitride semiconductor light emitting device comprising:
a conductive substrate having first and second opposing sides;
a first conductivity-type nitride semiconductor layer;
an active layer disposed on the first conductivity-type nitride semiconductor layer;
a second conductivity-type nitride semiconductor layer disposed on the active layer;
a light scattering layer disposed on the first side of the conductive substrate, the light scattering layer being made of a different material from that of the conductive substrate, the material having a light transmissibility of 70% or more and having a rough pattern disposed on an outer surface to scatter light, wherein the light scattering layer has a refractivity of 1.5 to 2.4, and a critical angle of 36.8 to 73.7;
a first electrode disposed on the light scattering layer having a rough pattern, wherein the light scattering layer and the first electrode are disposed on the same side of the conductive substrate; and
a second electrode disposed on the second conductivity-type nitride layer, wherein the second electrode is disposed on the second side of the conductive substrate and the second electrode includes a reflective metal layer,
wherein the light scattering layer extends from the conductive substrate to at least partially cover sides of the nitride light emitting device.
2. The vertical nitride semiconductor light emitting device according to claim 1 , wherein the light scattering layer comprises one selected from a group consisting of Indium Tin Oxide, SnO 2 , Ga 2 O 3 , ZnO, MgO and In 2 O 3 .
3. The vertical nitride semiconductor light emitting device according to claim 1 , wherein the rough pattern of the light scattering layer comprises microstructural features which are spaced from each other in the range of about 0.001 μm to 10 μm.
4. The vertical nitride semiconductor light emitting device according to claim 1 , further comprising an insulating layer formed between the light scattering layer covering the sides of the device, and the second conductivity-type nitride layer and the active layer.
5. The vertical nitride semiconductor light emitting device according to claim 1 , wherein the reflective metal layer comprises at least one selected from a group consisting of Ag, Al, Rh, Ru, Pt, Au, Cu, Pd, Cr, Ni, Co, Ti, In and Mo and alloys thereof.