EPITAXIAL WAFER, METHOD FOR PREPARING THE SAME AND DISPLAY DEVICE
An epitaxial wafer, a method for preparing the same and a display device are provided. The epitaxial wafer includes an N-type doped layer, a functional well structure and a P-type doped structure arranged in a stacked manner. The functional well structure is disposed between the N-type doped layer and the P-type doped structure, and the functional well structure includes a light emitting substructure and a transition substructure disposed between the light emitting substructure and the N-type doped layer. In the light emitting substructure, the functional well structure is a multiple quantum well structure, and a barrier layer in the multiple quantum well structure has a weak blocking effect on holes, which can increase a migration distance of holes, thereby increasing the number of quantum wells emitting light and improving the light emitting efficiency of the epitaxial wafer.
1 . An epitaxial wafer, comprising an N-type doped layer, a functional well structure and a P-type doped structure arranged in a stacked manner;
wherein the functional well structure is disposed between the N-type doped layer and the P-type doped structure, and the functional well structure comprises a light emitting substructure and a transition substructure disposed between the light emitting substructure and the N-type doped layer.
2 . The epitaxial wafer according to claim 1 , wherein the light emitting substructure comprises a multi-period light emitting layer disposed between the transition substructure and the P-type doped structure.
3 . The epitaxial wafer according to claim 2 , wherein the light emitting substructure further comprises a redundant barrier layer disposed between the multi-period light emitting layer and the P-type doped structure.
4 . The epitaxial wafer according to claim 1 , wherein the functional well structure comprises one of a group III-V multiple quantum well structure and a group II-VI multiple quantum well structure.
5 . The epitaxial wafer according to claim 2 , wherein the multi-period light emitting layer comprises a plurality of light emitting stack layers, wherein each of the plurality of light emitting stack layers comprises a first barrier layer and a first well layer, and the first barrier layer is disposed between the first well layer of a same light emitting stack layer and the N-type doped layer.
6 . The epitaxial wafer according to claim 5 , wherein the first well layer comprises an In w Ga 1-w N layer, where 0.1≤w≤0.4, and the first barrier layer comprises an N-type doped GaN layer.
7 . The epitaxial wafer according to claim 5 , wherein the first well layer has a thickness ranging from 2.0 nm to 4.0 nm, and the first barrier layer has a thickness ranging from 9.0 nm to 14.0 nm.
8 . The epitaxial wafer according to claim 5 , wherein the multi-period light emitting layer comprises five to ten light emitting stack layers.
9 . The epitaxial wafer according to claim 3 , wherein the redundant barrier layer comprises an intrinsic layer.
10 . The epitaxial wafer according to claim 3 , wherein the redundant barrier layer comprises one of a group III-V intrinsic layer and a group II-VI intrinsic layer.
11 . The epitaxial wafer according to claim 9 , wherein the redundant barrier layer comprises a GaN intrinsic layer.
12 . The epitaxial wafer according to claim 5 , wherein the redundant barrier layer has a thickness equal to a thickness of the first barrier layer.
13 . The epitaxial wafer according to claim 1 , wherein the transition substructure comprises a plurality of transition stack layers, and each of the plurality of transition stack layers comprises a second barrier layer and a second well layer, wherein the second barrier layer is disposed between the second well layer of a same transition stack layer and the N-type doped layer.
14 . The epitaxial wafer according to claim 13 , wherein the second well layer comprises an In x Ga 1-x N layer, where 0<x≤0.3, and the second barrier layer comprises an N-type doped Al y Ga 1-y N layer, where 0≤y≤0.2.
15 . The epitaxial wafer according to claim 14 , wherein a component content of Al in the second barrier layer at a side away from the N-type doped layer is greater than the component content of Al in the second barrier layer at a side adjacent to the N-type doped layer.
16 . The epitaxial wafer according to claim 15 , wherein the component content of Al in the second barrier layer gradually increases in a direction away from the N-type doped layer; or
the component content of Al in the second barrier layer gradually increases from layer to layer in the direction away from the N-type doped layer.
17 . The epitaxial wafer according to claim 13 , wherein the second well layer has a thickness ranging from 2.0 nm to 4.0 nm, and the second barrier layer has a thickness ranging from 7.0 nm to 12.0 nm.
18 . The epitaxial wafer according to claim 13 , wherein the transition substructure comprises three to five transition stack layers.
19 . The epitaxial wafer according to claim 1 , wherein the P-type doped structure comprises a P-type layer and a multi-period doped layer disposed between the P-type layer and the functional well structure.
20 . The epitaxial wafer according to claim 19 , wherein the multi-period doped layer comprises a plurality of doped stack layers, and each of the plurality of doped stack layers comprises a ternary doped layer and a binary doped layer, wherein the ternary doped layer is disposed between the binary doped layer of a same doped stack layer and the functional well structure.
21 . The epitaxial wafer according to claim 19 , wherein a concentration of a P-type dopant in the multi-period doped layer at a side away from the N-type doped layer is greater than the concentration of the P-type dopant in the multi-period doped layer at a side adjacent to the N-type doped layer.
22 . The epitaxial wafer according to claim 21 , wherein the concentration of the P-type dopant in the multi-period doped layer increases periodically in a direction away from the N-type doped layer.
23 . The epitaxial wafer according to claim 22 , wherein the concentration of the P-type dopant is consistent in the same doped stack layer; or
the concentration of the P-type dopant increases layer by layer in the direction away from the N-type doped layer in the same doped stack layer; or
the concentration of the P-type dopant gradually increases in the direction away from the N-type doped layer in the same doped stack layer.
24 . The epitaxial wafer according to claim 20 , wherein the ternary doped layer comprises a P-type doped InGaN layer, and the binary doped layer comprises a P-type doped GaN layer.
25 . The epitaxial wafer according to claim 24 , wherein a component content of Ga in the multi-period doped layer at a side away from the N-type doped layer is less than the component content of Ga in the multi-period doped layer at a side adjacent to the N-type doped layer; and
a component content of In in the InGaN layer in the multi-period doped layer at the side away from the N-type doped layer is greater than the component content of In in the InGaN layer in the multi-period doped layer at the side adjacent to the N-type doped layer.
26 . The epitaxial wafer according to claim 25 , wherein the component content of Ga periodically decreases and the component content of In periodically increases in a direction away from the N-type doped layer in the multi-period doped layer.
27 . The epitaxial wafer according to claim 26 , wherein the component content of Ga is consistent and the component content of In in the InGaN layer is consistent in the same doped stack layer; or
the component content of Ga decreases layer by layer in the direction away from the N-type doped layer in the same doped stack layer; or
the component content of Ga gradually decreases and the component content of In in the InGaN layer gradually increases in the direction away from the N-type doped layer in the same doped stack layer.
28 . The epitaxial wafer according to claim 20 , wherein each of the plurality of doped stack layers has a thickness ranging from 5 nm to 10 nm.
29 . The epitaxial wafer according to claim 20 , wherein the multi-period doped layer has at least five doped stack layers.
30 . The epitaxial wafer according to claim 1 , wherein a concentration of a P-type dopant in the P-type doped structure is in a range from 3×10 18 atoms/cm 3 to 5×10 20 atoms/cm 3 .
31 . The epitaxial wafer according to claim 1 , wherein the N-type doped layer comprises at least one of a GaN layer, an AlGaN layer and an AlInGaN layer.
32 . The epitaxial wafer according to claim 31 , wherein a concentration of an N-type dopant in the N-type doped layer is in a range from 8×10 18 atoms/cm 3 to 1×10 21 atoms/cm 3 .
33 . The epitaxial wafer according to claim 1 , wherein the functional well structure further comprises a stress adjustment structure disposed between the N-type doped layer and the transition substructure.
34 . The epitaxial wafer according to claim 33 , wherein the stress adjustment structure comprises a plurality of stress adjustment stack layers, and each of the plurality of stress adjustment stack layers comprises a third well layer and a third barrier layer, wherein the third barrier layer is disposed between the third well layer of a same adjustment stack layer and the N-type doped layer.
35 . The epitaxial wafer according to claim 34 , wherein the third well layer comprises an In z Ga 1-z N layer, where 0<z≤0.1, and the third barrier layer comprises a GaN layer.
36 . The epitaxial wafer according to claim 34 , wherein the third well layer has a thickness ranging from 1.0 nm to 2.5 nm, and the third barrier layer has a thickness ranging from 2.0 nm to 4.0 nm.
37 . The epitaxial wafer according to claim 34 , wherein the stress adjustment structure comprises at least nine stress adjustment stack layers.
38 . The epitaxial wafer according to claim 1 , further comprising an undoped layer, a buffer layer and a substrate;
wherein the substrate is disposed on a side of the N-type doped layer away from the P-type doped structure;
the buffer layer is disposed between the substrate and the N-type doped layer; and
the undoped layer is disposed between the buffer layer and the N-type doped layer.
39 . The epitaxial wafer according to claim 38 , wherein the undoped layer comprises at least one of a GaN layer, an AlGaN layer and an AlInGaN layer.
40 . The epitaxial wafer according to claim 38 , wherein the buffer layer comprises at least one of an AlN layer, a GaN layer, an AlGaN layer and an AlInGaN layer.
41 . The epitaxial wafer according to claim 38 , wherein the buffer layer has a thickness ranging from 15 nm to 50 nm.
42 . A display device, comprising an epitaxial wafer according to claim 1 .