Inverted light emitting diode having plasmonically enhanced emission
View Patent ↗An LED device having plasmonically enhanced emission is provided. The device includes an inverted LED structure with a coating of metal nanoparticles on the surface chosen to match the plasmonic response to the peak emission from the active quantum well (QW) emission region of the LED. The active QW emission region is separated from the metal nanoparticles on the surface by a thin n-type contact layer disposed on a top side of the active QW emission. A p-type layer is disposed immediately beneath the active QW emission region and injects holes into the active QW emission region. The n-type contact layer is sufficiently thin to permit a coupling of the surface plasmons (SPs) from the metal nanoparticles and the excitons in the active QW emission region. The SP-exciton coupling provides an alternative decay route for the excitons and thus enhances the photon emission from the LED device.
1. A light emitting device having plasmonically enhanced emission, comprising:
an inverted light emitting diode (LED) comprising
a p-type layer disposed on a substrate, the p-type layer comprising a layer of a p-type III-nitride semiconductor material;
a p-type electrode contacted to the p-type layer to provide an Ohmic contact to the p-type layer;
an n-type layer comprising a layer of an n-type III-nitride semiconductor material;
an n-type electrode disposed on a first region of the n-type layer, the n-type electrode being contacted to the n-type layer to provide an Ohmic contact to the n-type layer;
an active quantum well region disposed between the n-type layer and the p-type layer, electrons from the n-type layer and holes from the p-type layer forming electron-hole pairs in the active quantum well region upon the application of current to the inverted LED via the n-type and p-type Ohmic contacts; and
a plasmonic metal coating configured to enhance a light emission from the light emitting device, the plasmonic metal coating comprising a plurality of metal nanoparticles disposed on a second region of the n-type layer, the first and second regions being discrete so that the plasmonic metal coating is separate from the n-type electrode, the plasmonic metal coating having a different structure from the n-type electrode such that the plasmonic metal coating and the n-type electrode form separate and discrete structures on the n-type layer;
wherein the plasmonic metal coating is configured to match a plasmonic response to a peak emission from the active quantum well region and generate a plurality of surface plasmons at an interface of the plasmonic metal coating and the n-type layer, the n-type layer being sufficiently thin to cause the active quantum well region to be within a fringing field of the surface plasmons;
wherein a first plurality of the electron-hole pairs decay via a first decay route to produce a first light emission from the light-emitting device; and
wherein a second plurality of the electron-hole pairs couple with a corresponding plurality of the surface plasmons and decay via a second decay route provided by the coupling of the electron-hole pairs and the surface plasmons to produce a second light emission from the light-emitting device;
the first and second light emissions providing an enhanced light emission from the light-emitting device.
2. The light emitting device according to claim 1 , wherein the n-type layer has a thickness of less than 50 nm.
3. The light emitting device according to claim 1 , wherein the n-type layer has a thickness of less than 30 nm.
4. The light emitting device according to claim 1 , wherein the n-type layer comprises one of GaN, AlGaN, InGaN, InAlGaN.
5. The light emitting device according to claim 1 , wherein the n-type layer is a highly doped n+ AlGan layer having a thickness of about 20 nm.
6. The light emitting device according to claim 1 , wherein the p-type layer comprises one of GaN, AlGaN, InGaN, InAlGaN.
7. The light emitting device according to claim 1 , wherein the p-type layer is deposited on a substrate that is not involved in current transport and has a thickness of about 500 to about 5000 nm.
8. The light emitting device according to claim 1 , wherein the p-type layer is deposited on a p-type substrate and has a thickness of about 10 to about 500 nm.
9. The light emitting device according to claim 1 , wherein the p-type layer is a highly doped p+ GaN layer having a thickness of about 2000 nm.
10. The light emitting device according to claim 1 , wherein the plasmonic metal coating comprises a periodic coating of metal nanoparticles.
11. The light emitting device according to claim 1 , wherein the plasmonic metal coating comprises a coating of one of silver, gold, and copper.