Light emitting diode with improved structure
View Patent ↗Disclosed is a light emitting diode (LED) with an improved structure. The LED comprises an N-type semiconductor layer, a P-type semiconductor layer and an active layer interposed between the N-type and P-type semiconductor layers. The P-type compound semiconductor layer has a laminated structure comprising a P-type clad layer positioned on the active layer, a hole injection layer positioned on the P-type clad layer, and a P-type contact layer positioned on the hole injection layer. Accordingly, holes are more smoothly injected into the active layer from the P-type semiconductor layer, thereby improving the recombination rate of electrons and holes.
1. A light emitting diode (LED), comprising:
an N-type semiconductor layer;
a P-type semiconductor layer; and
an active layer interposed between the N-type semiconductor layer and the P-type semiconductor layer,
wherein the P-type semiconductor layer comprises a laminated structure, the laminated structure comprising:
a P-type clad layer positioned on the active layer;
a hole injection layer positioned on the P-type clad layer;
a P-type contact layer positioned on the hole injection layer; and
an upper undoped layer interposed between the hole injection layer and the P-type contact layer, the upper updoped layer contacting the hole injection layer,
wherein a doping concentration of the hole injection layer is lower than a doping concentration of the P-type clad layer,
wherein a bandqap of the P-type clad layer is wider than a bandqap of the hole injection layer, and the bandqap of the hole injection layer is equal to a bandqap of the P-type contact layer, and
wherein the hole injection layer, the upper undoped layer contacting the hole injection layer, and the P-type contact layer are semiconductor layers having a substantially identical band gap.
2. The LED as claimed in claim 1 , wherein a doping concentration of the P-type contact layer is higher than the doping concentration of the P-type clad layer.
3. The LED as claimed in claim 2 , wherein the hole injection layer is thicker than the P-type clad layer, and the P-type contact layer is thinner than the P-type clad layer.
4. The LED as claimed in claim 1 , further comprising an undoped layer interposed between the active layer and the P-type clad layer.
5. The LED as claimed in claim 4 , wherein the undoped layer physically contacts both the hole injection layer and the P-type contact layer.
6. The LED as claimed in claim 1 , further comprising a lower undoped layer interposed between the P-type clad layer and the hole injection layer.
7. The LED as claimed in claim 1 , further comprising:
a first undoped layer interposed between the active layer and the P-type clad layer; and
a second undoped layer on the P-type clad layer.
8. The LED as claimed in claim 7 , wherein the first undoped layer physically contacts both the active layer and the P-type clad layer.
9. The LED as claimed in claim 7 , wherein the second undoped layer is interposed between the P-type clad layer and the hole injection layer.
10. The LED as claimed in claim 9 , wherein the first undoped layer physically contacts both the active layer and the P-type clad layer, and the second undoped layer physically contacts both the P-type clad layer and the hole injection layer.