Photonic crystal light emitting device
View Patent ↗A photonic crystal structure is formed in an n-type layer of a III-nitride light emitting device. In some embodiments, the photonic crystal n-type layer is formed on a tunnel junction. The device includes a first layer of first conductivity type, a first layer of second conductivity type, and an active region separating the first layer of first conductivity type from the first layer of second conductivity type. The tunnel junction includes a second layer of first conductivity type and a second layer of second conductivity type and separates the first layer of first conductivity type from a third layer of first conductivity type. A photonic crystal structure is formed in the third layer of first conductivity type.
1. A light emitting device comprising:
a III-nitride semiconductor structure including an active region disposed between an n-type and a p-type region;
a photonic crystal structure formed in an n-type region; and
a reflector;
wherein the p-type region is substantially planar and the photonic crystal structure does not extend into the p-type region; and
wherein the reflector and the photonic crystal structure are disposed on opposite sides of the active region.
2. The device of claim 1 wherein the photonic crystal structure comprises a periodic variation in a thickness of the n-type region.
3. The device of claim 1 wherein the photonic crystal structure comprises a planar lattice of holes.
4. The device of claim 3 wherein the lattice has a lattice constant a between about 0.1 λ and about 10 λ, where λ is a wavelength of light emitted by the active region.
5. The device of claim 3 wherein the lattice has a lattice constant a and the holes have a diameter between about 0.1a and about 0.5a.
6. The device of claim 3 wherein the holes have a depth between about 0.05 λ and about 5 λ, where λ is a wavelength of light emitted by the active region.
7. The device of claim 3 wherein the lattice is selected from the group consisting of a triangular lattice, a square lattice, a hexagonal lattice, and a honeycomb lattice.
8. The device of claim 3 wherein the lattice includes more than one lattice type.
9. The device of claim 3 wherein a lattice type, lattice constant, hole diameter, and hole depth are selected to create a predetermined radiation pattern.
10. The device of claim 3 wherein a lattice type, lattice constant, hole diameter, and hole depth are selected to create a radiation pattern having a maximum in power emitted in a direction substantially perpendicular to a surface of the semiconductor structure.
11. The device of claim 3 wherein a lattice type, lattice constant, hole diameter, and hole depth are selected to create a radiation pattern having a maximum in power emitted in a direction substantially 30° from an axis perpendicular to a surface of the semiconductor structure.
12. The device of claim 3 wherein a lattice type, lattice constant, hole diameter, and hole depth are selected such that at least 50% of total power emitted from the device is emitted in a 45° cone centered about an axis perpendicular to a surface of the device.
13. The device of claim 3 wherein a lattice type, lattice constant, hole diameter, and hole depth are selected such that at least 25% of total power emitted from the device is emitted in a 30° cone centered about an axis perpendicular to a surface of the device.