Light-emitting diode

1 . A light-emitting diode, comprising an N-type semiconductor layer, a light-emitting layer, a first P-type semiconductor layer, a hole diffusion layer and a second P-type semiconductor layer sequentially stacked in that order;

wherein the hole diffusion layer comprises a first sub-layer, a second sub-layer, and a third sub-layer sequentially stacked in that order along a direction from the first P-type semiconductor layer to the second P-type semiconductor layer; the first sub-layer is an aluminum nitride (AlN) layer, the second sub-layer is one of an aluminum indium gallium nitride (AlInGaN) layer and an aluminum gallium nitride (AlGaN) layer, and the third sub-layer is one of an AlInGaN layer and an AlGaN layer; and

wherein the hole diffusion layer further comprises at least one fourth sub-layer disposed on a side of the third sub-layer facing away from the second sub-layer, and each of the at least one fourth sub-layer comprises an AlGaN layer and a GaN layer stacked.

2 . The light-emitting diode according to claim 1 , wherein each of the first P-type semiconductor layer and the second P-type semiconductor layer is a magnesium-doped (Mg-doped) gallium nitride (GaN) layer.

3 . The light-emitting diode according to claim 1 , wherein each of the first sub-layer, the second sub-layer and the third sub-layer is an undoped layer.

4 . The light-emitting diode according to claim 1 , wherein an aluminum (Al) concentration of the first sub-layer, an Al concentration of the second sub-layer and an Al concentration of the third sub-layer are sequentially decreased in that order.

5 . The light-emitting diode according to claim 1 , wherein a thickness of the first sub-layer is in a range of 0.5 to 2 nanometers (nm), a thickness of the second sub-layer is in a range of 5 to 20 nm, and a thickness of the third sub-layer is a in a range from 5 to 30 nm.

6 . The light-emitting diode according to claim 1 , wherein the at least one fourth sub-layer of the hole diffusion layer is a plurality of fourth sub-layers, and Al concentrations of the plurality of fourth sub-layers are gradually decreased along a direction from the second sub-layer to the third sub-layer.

7 . The light-emitting diode according to claim 1 , further comprising an electron blocking layer arranged between the light-emitting layer and the first P-type semiconductor layer, wherein the electron blocking layer comprises an AlInGaN/InGaN superlattice structure layer and an AlN layer stacked in that order along a direction from the light-emitting layer to the first P-type semiconductor layer.

8 . The light-emitting diode according to claim 7 , wherein the light-emitting layer comprises an InGaN layer and a GaN layer alternately stacked, and a side of the light-emitting layer adjacent to the electron blocking layer is an undoped GaN layer.

9 . A light-emitting diode, comprising an N-type semiconductor layer, a light-emitting layer and a P-type semiconductor layer sequentially stacked in that order, and further comprising a hole diffusion layer located between the light-emitting layer and the P-type semiconductor layer;

wherein the hole diffusion layer comprises a first sub-layer, a second sub-layer and a third sub-layer sequentially stacked in that order along a direction from the light-emitting layer to the P-type semiconductor layer; the first sub-layer is an undoped AlN layer, the second sub-layer is one of an undoped AlInGaN layer and an undoped AlGaN layer, and the third sub-layer is one of an undoped AlInGaN layer and an undoped AlGaN layer; and

wherein the hole diffusion layer further comprises at least one fourth sub-layer disposed on a side of the third sub-layer facing away from the second sub-layer, and each of the at least one fourth sub-layer comprises an AlGaN layer and a GaN layer stacked.

10 . The light-emitting diode according to claim 9 , wherein the P-type semiconductor layer comprises a plurality of Mg-doped GaN layers.

11 . The light-emitting diode according to claim 9 , wherein Al concentrations of the first sub-layer, the second sub-layer and the third sub-layer are sequentially decreased in that order.

12 . The light-emitting diode according to claim 9 , wherein a thickness of the first sub-layer is in a range of 0.5 to 2 nm, a thickness of the second sub-layer is in a range of 5 to 20 nm, and a thickness of the third sub-layer is a in a range from 5 to 30 nm.

13 . The light-emitting diode according to claim 1 , wherein the at least one fourth sub-layer of the hole diffusion layer is a plurality of fourth sub-layers, and Al concentrations of the plurality of fourth sub-layers are gradually decreased along a direction from the second sub-layer to the third sub-layer.

14 . The light-emitting diode according to claim 9 , further comprising an electron blocking layer arranged between the light-emitting layer and the P-type semiconductor layer, wherein the electron blocking layer comprises an AlInGaN/InGaN superlattice structure layer and an AlN layer stacked in that order along a direction from the light-emitting layer to the P-type semiconductor layer.

15 . A light-emitting diode, comprising: an N-type semiconductor layer, a multilayer structure, and a light-emitting layer arranged between the N-type semiconductor layer and the multilayer structure;

wherein the multilayer structure comprises: a Mg-doped P-type semiconductor layer, and a hole diffusion layer between the Mg-doped P-type semiconductor layer and the light-emitting layer;

wherein the hole diffusion layer comprises Al-containing sub-layers being not doped with Mg, and Al concentrations of the respective Al-containing sub-layers are gradually decreased along a direction from the light-emitting layer to the Mg-doped P-type semiconductor layer;

wherein the Al-containing sub-layers comprise a plurality of sequentially stacked single-layered sub-layers and at least one multi-layered sub-layer, and the at least one multi-layered sub-layer is located on a side of the plurality of sequentially stacked single-layered sub-layers facing away from the light-emitting layer; and

wherein each of the at least one multi-layered sub-layer comprises: a layer of containing Al, and another layer of not containing Al on a side of the layer of containing Al facing away from the light-emitting layer.

16 . The light-emitting diode according to claim 15 , wherein the multilayer structure further comprises another Mg-doped P-type semiconductor layer having a lower growth temperature than that of the Mg-doped P-type semiconductor layer and arranged between the hole diffusion layer and the light-emitting layer.