Light emitting diode and fabrication method therof
A light-emitting diode includes from bottom to up: a substrate, a first-conductive type semiconductor layer, a super lattice, a multi-quantum well layer and a second-conductive type semiconductor layer. At least one layer of granular medium layer is inserted in the super lattice. The granular medium layer is used for forming V pits with different widths and depths in the super lattice. The multi-quantum well layer fills up the V pits and is over the top surface of the super lattice. The number of micro-particle generations, positions and densities can be adjusted by introducing granular medium layers and controlling the number of layers, position and growth conditions during super lattice growth process, to ensure V pits of different depths and densities. This can change hole injection effect, effectively improve hole injection efficiency and distribution uniformity in all quantum wells, thus improving LED light-emitting efficiency.
1. A light-emitting diode, comprising:
a first-conductive type semiconductor layer;
a super lattice;
a multi-quantum well layer;
a second-conductive type semiconductor layer;
wherein, at least one medium layer having a plurality of grains therein is embedded in the super lattice;
the medium layer is used for forming V pits with different widths and depths in the super lattice;
the multi-quantum well layer fills up the V pits and is over a top surface of the super lattice; and
a density of the plurality of grains in the medium layer is approximately same as that of the V pits.
2. The light-emitting diode of claim 1 , wherein, sizes of the plurality of grains in the medium layer are 0.5-5 nm, and the V pits are 50-500 nm wide.
3. The light-emitting diode of claim 1 , wherein, the depth H of the V pits depends on a total thickness of the super lattice T 1 , a total thickness of the multi-quantum well layer T 2 and a position of the medium layer in the super lattice layer, and satisfies T 2 <H<T 1 +T 2 .
4. The light-emitting diode of claim 1 , wherein, the density of the plurality of grains in the medium layer ranges from 1×10 7 cm −2 to 1×10 9 cm −2 .
5. The light-emitting diode of claim 1 , wherein, the medium layer comprises at least one of Mg x N y , Si x N y , Si x O y , Ti x O y , Zr x O y , Hf x O y , or Ta x O y .
6. The light-emitting diode of claim 1 , wherein, three granular medium layers are inserted during growth of the super lattice.
7. A method of fabricating the light-emitting diode according to claim 1 , the method comprising:
(1) providing a substrate;
(2) growing a first-conductive type semiconductor layer over the substrate;
(3) forming a super lattice over the first-conductive type semiconductor layer, and inserting at least one medium layer having a plurality of grains therein during growth of the super lattice, wherein, the medium layer is used for forming V pits with different widths and depths in the super lattice;
(4) growing a multi-quantum well layer over the V pits and a top surface of the super lattice;
(5) growing a second-conductive type semiconductor layer over the multi-quantum well layer.
8. The fabrication method of claim 7 , wherein: sizes of the plurality of grains in the medium layer are 0.5-5 nm, and the V pits are 50-500 nm wide.
9. The fabrication method of claim 7 , wherein, the depth H of the V pits depends on a total thickness of the super lattice T 1 , a total thickness of the multi-quantum well layer T 2 and a position of the granular medium layer in the super lattice layer, and satisfies T 2 <H<T 1 +T 2 .
10. The fabrication method of claim 7 , wherein, the density of the plurality of grains in the medium layer ranges from 1×10 7 cm −2 to 1×10 9 cm −2 .
11. The fabrication method of claim 7 , wherein, the medium layer comprises at least one of Mg x N y , Si x N y , Si x O y , Ti x O y , Zr x O y , Hf x O y , or Ta x O y .
12. The fabrication method of claim 7 , wherein, a growth temperature for the super lattice is 700-900° C.
13. The fabrication method of claim 7 , wherein, in step (3), at least one medium layer is inserted during growth of the super lattice; thereby facilitating the super lattice to form the V pits at the medium layer from an epitaxial surface due to low growth temperature and poor lateral epitaxial capacity.
14. A light-emitting system comprising a plurality of light-emitting diodes, wherein each light-emitting diode comprises:
a first-conductive type semiconductor layer;
a super lattice;
a multi-quantum well layer;
a second-conductive type semiconductor layer;
wherein, at least one medium layer having a plurality of grains therein is embedded in the super lattice;
the medium layer is used for forming V pits with different widths and depths in the super lattice;
the multi-quantum well layer fills up the V pits and is over a top surface of the super lattice; and
a density of the plurality of grains in the medium layer is approximately same as that of the V pits.
15. The light-emitting system of claim 14 , wherein, sizes of the plurality of grains in the medium layer are 0.5-5 nm, and the V pits are 50-500 nm wide.
16. The light-emitting system of claim 14 , wherein, the depth H of the V pits depends on a total thickness of the super lattice T 1 , a total thickness of the multi-quantum well layer T 2 and a position of the granular medium layer in the super lattice layer, and satisfies T 2 <H<T 1 +T 2 .
17. The light-emitting system of claim 14 , wherein, the density of the plurality of grains in the medium layer ranges from 1×10 7 cm −2 to 1×10 9 cm −2 .
18. The light-emitting system of claim 14 , wherein, the medium layer comprises at least one of Mg x N y , Si x N y , Si x O y , Ti x O y , Zr x O y , Hf x O y , or Ta x O y .
19. The light-emitting system of claim 14 , wherein, three medium layers are inserted during growth of the super lattice.
20. The light-emitting system of claim 14 , wherein, a growth temperature for the super lattice is 700-900° C.