A deep ultraviolet LED epitaxial wafer, an epitaxial growth method and an LED chip

Abstract

The present invention provides a deep ultraviolet LED epitaxial wafer, an epitaxial growth method and an LED chip. By providing a hole conduction layer formed by periodically alternating growth of a plurality of two-dimensional AlN sub-layers, and introducing alkaline earth metal elements Mg, Ca, Zn, Sr doping into the hole conduction layer, the two-dimensional AlN sub-layers are P-doped to provide holes. At the same time, due to the introduction of magnetic particles, shallow acceptor impurity levels can be introduced into the AlN structure. Due to the introduction of the shallow acceptor impurity levels, it is more conducive to hole ionization and conduction, thereby improving the luminous efficiency of the deep ultraviolet LED.

Description

Technical Field

[0001] The present invention relates to the technical field of LEDs, and particularly relates to a deep ultraviolet LED epitaxial wafer, an epitaxial growth method and an LED chip. Background Art

[0002] A light emitting diode (LED) is a semiconductor electronic component that can emit light. Due to its small size, high brightness, low energy consumption and other characteristics, it has attracted the attention of more and more researchers.

[0003] In recent years, AlGaN-based deep ultraviolet light emitting diodes have been widely used. For example, they are used in air and water purification, surface disinfection, ultraviolet curing, medical phototherapy and other aspects. The ultraviolet band can usually be divided into: long-wave ultraviolet UVA (320nm - 400nm), medium-wave ultraviolet UVB (280nm - 320nm), short-wave ultraviolet UVC (200nm - 280nm) and vacuum ultraviolet (10nm - 200nm). For AlGaN-based materials, the shorter the wavelength, the higher the Al component. Therefore, high-quality material epitaxy and effective doping face increasing challenges. Although the light output power of deep ultraviolet LEDs has been greatly improved, AlGaN-based deep ultraviolet LEDs still have bottleneck problems of low external quantum efficiency and low luminous power.

[0004] First, there is a large lattice mismatch and thermal mismatch between the high-Al component AlGaN material and the sapphire substrate, resulting in a large dislocation density during the epitaxial growth of AlGaN on the sapphire substrate, forming serious non-radiative recombination centers. Second, the spontaneous and piezoelectric charges induced at the heterojunction interface of the active layer of group III nitrides cause the energy band of the quantum well to tilt, weakening the overlap of the electron and hole wave functions, thereby further reducing the radiative recombination rate. In addition, electron leakage caused by unbalanced hole and electron injection in deep ultraviolet LEDs is also considered an important factor for the low internal quantum efficiency.

[0005] Specifically, as the wavelength of deep ultraviolet gradually becomes shorter, the Al component of the quantum well gradually increases, that is, the Al component of the electron blocking layer gradually increases. Therefore, while the electron blocking layer effectively blocks electrons and prevents electron overflow, it also has an adverse effect on the injection of holes. The physical reason is that in the electron blocking layer of AlGaN or AlN materials, the acceptor impurity level is deeper than that of GaN, and as the Al component increases, the bandgap width of the AlGaN material increases, the acceptor level deepens continuously, and the activation energy continues to increase, resulting in a decrease in the activation efficiency and concentration of hole carriers, thereby reducing the electron injection efficiency and luminous efficiency of deep ultraviolet light emitting diodes. Summary of the Invention

[0006] Based on this, the object of the present invention is to provide a deep ultraviolet LED epitaxial wafer, an epitaxial growth method and an LED chip, aiming to solve the problem in the prior art that due to the relatively high Al component in the quantum well of the AlGaN-based deep ultraviolet light-emitting diode, the hole injection is affected, resulting in low luminous efficiency.

[0007] According to an embodiment of the present invention, a deep ultraviolet LED epitaxial wafer includes a hole conduction layer, and the hole conduction layer is formed by periodically and alternately growing a plurality of two-dimensional AlN sub-layers. Among them, some of the AlN sub-layers in the hole conduction layer are doped with alkaline earth metal elements, and the alkaline earth metal elements are any one or a combination of several of Mg, Ca, Zn, and Sr.

[0008] Furthermore, the deep ultraviolet LED epitaxial wafer further includes a substrate, an AlGaN buffer layer, an undoped AlGaN, an N-type AlGaN layer, a multi-quantum well layer, a P-type AlGaN layer, and a P-type contact layer;

[0009] The AlGaN buffer layer, the undoped AlGaN, the N-type AlGaN layer, the multi-quantum well layer, the hole conduction layer, the P-type AlGaN layer, and the P-type contact layer are sequentially epitaxially grown on the substrate.

[0010] Furthermore, the hole conduction layer is a composite structure formed by periodically and alternately growing undoped AlN sub-layers and AlN sub-layers doped with alkaline earth metal elements. Among them, the AlN sub-layers doped with alkaline earth metal elements are doped with any one or a combination of several of Mg, Ca, Zn, and Sr.

[0011] Furthermore, the hole conduction layer is a composite structure formed by periodically and alternately growing any two, three, four, or five of the undoped AlN sub-layers, the AlN sub-layers doped with Mg, the AlN sub-layers doped with Ca, the AlN sub-layers doped with Zn, and the AlN sub-layers doped with Sr.

[0012] Furthermore, the doping of the alkaline earth metal elements Mg, Ca, Zn, and Sr in the hole conduction layer is carried out under nitrogen-rich conditions, and the molar ratio of group V elements to group III elements is greater than 20000.

[0013] Furthermore, the doping concentration of the alkaline earth metal elements Mg, Ca, Zn, and Sr in the hole conduction layer is 0.01% - 0.5%.

[0014] Furthermore, the growth temperature of the hole conduction layer is 800°C - 1100°C.

[0015] According to an epitaxial growth method of an LED epitaxial wafer in an embodiment of the present invention, which is used to prepare the above-mentioned deep ultraviolet LED epitaxial wafer, the epitaxial growth method includes: growing a hole conduction layer, which is formed by periodically and alternately growing a plurality of two-dimensional AlN sub-layers. Among them, some of the AlN sub-layers in the hole conduction layer are doped with alkaline earth metal elements, and the alkaline earth metal elements are any one or a combination of several of Mg, Ca, Zn, and Sr.

[0016] Further, the epitaxial growth method further includes:

[0017] Providing a substrate required for growth;

[0018] Epitaxially growing an AlGaN buffer layer, an undoped AlGaN, an N-type AlGaN layer, a multi-quantum well layer, the hole conduction layer, a P-type AlGaN layer, and a P-type contact layer on the substrate in sequence.

[0019] An LED chip according to an embodiment of the present invention includes the above-mentioned deep ultraviolet LED epitaxial wafer.

[0020] Compared with the prior art: for the deep ultraviolet LED epitaxial wafer provided by the present invention, by setting a hole conduction layer formed by periodically and alternately growing a plurality of two-dimensional AlN sub-layers, and introducing alkaline earth metal elements Mg, Ca, Zn, and Sr doping into the hole conduction layer, P-doping of the two-dimensional AlN sub-layers is realized to provide holes. At the same time, due to the introduction of magnetic particles, shallow acceptor impurity levels can be introduced into the AlN structure. Due to the introduction of the shallow acceptor impurity levels, it is more conducive to hole ionization and conduction, thereby improving the luminous efficiency of the deep ultraviolet LED. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic structural diagram of a deep ultraviolet LED epitaxial wafer provided by an embodiment of the present invention;

[0022] Figure 2 It is a flowchart of the implementation of an epitaxial growth method of an LED epitaxial wafer provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0023] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. Several embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0024] It should be noted that when an element is referred to as "fixed on" another element, it can be directly on the other element or there may be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used in this article are only for the purpose of illustration.

[0025] Unless otherwise defined, all technical and scientific terms used in this article have the same meaning as those commonly understood by those skilled in the technical field to which this invention belongs. The terms used in the description of the present invention in this article are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used in this article includes any and all combinations of one or more of the related listed items.

[0026] Reference Figure 1 , which is a schematic structural diagram of a deep ultraviolet LED epitaxial wafer provided by an embodiment of the present invention. The deep ultraviolet LED epitaxial wafer includes a substrate 1 and an AlGaN buffer layer 2, an undoped AlGaN layer 3, an N-type AlGaN layer 4, a multi-quantum well layer 5, a hole conduction layer 6, a P-type AlGaN layer 7, and a P-type contact layer 8 sequentially provided on the substrate 1.

[0027] Among them, the hole conduction layer 6 in the deep ultraviolet LED epitaxial wafer is formed by periodically growing a plurality of two-dimensional AlN sub-layers. Specifically, some of the AlN sub-layers in the hole conduction layer 6 are doped with alkaline earth metal elements, and the alkaline earth metal elements are any one or a combination of Mg, Ca, Zn, and Sr. It should be noted that since the bond length formed by Mg, Ca, Zn, Sr atoms and N is longer than the Al-N bond length, stretching the bond length helps to reduce the electrostatic repulsion potential, making the doping system have a lower total energy and being easier to dope. In addition, since the ionic radii of Mg, Ca, Zn, Sr do not differ much from Al, the planar structure of the system is not destroyed; since the electronegativity of Mg, Ca, Zn, Sr atoms is closer to that of Al atoms rather than N atoms, in a nitrogen-rich environment, the impurity atoms are more likely to replace Al atoms and be doped into the single layer. Since each Mg, Ca, Zn, Sr atom has only two valence electrons, which is one less than the three valence electrons of Al atoms, the introduction of each Mg, Ca, Zn, Sr atom brings a hole to the system and introduces a shallow acceptor impurity level in the energy band gap of the system, which is more conducive to the ionization of holes; finally, each substitutional atom will introduce a Bohr magneton. At this time, the material shows magnetism, and a spin-polarized shallow acceptor level is introduced in the forbidden band of the system. This level happens to be at the Fermi level, making the system exhibit semi-metallicity and greatly improving the conductivity, thereby improving the hole conduction.

[0028] In an embodiment of the present invention, the number of cycles of alternating growth of several two-dimensional AlN sublayers in the hole conduction layer 6 provided by the present invention may be 2 to 100, and the present invention does not make specific limitations thereto.

[0029] In an embodiment of the present invention, the hole conduction layer 6 is a composite structure formed by periodically alternating growth of undoped AlN sublayers and AlN sublayers doped with alkaline earth metal elements. Among them, the AlN sublayers doped with alkaline earth metal elements are doped with any one or a combination of several of Mg, Ca, Zn, and Sr. It can be understood that the hole conduction layer 6 can be a composite structure formed by periodically alternating growth of undoped AlN sublayers and AlN sublayers doped with Mg; the hole conduction layer 6 can be a composite structure formed by periodically alternating growth of undoped AlN sublayers and AlN sublayers doped with Ca; the hole conduction layer 6 can be a composite structure formed by periodically alternating growth of undoped AlN sublayers and AlN sublayers doped with Zn; the hole conduction layer 6 can be a composite structure formed by periodically alternating growth of undoped AlN sublayers and AlN sublayers doped with Sr.

[0030] Exemplarily, the hole conduction layer 6 can also be a composite structure formed by periodically alternating growth of undoped AlN sublayers and AlN sublayers doped with Mg / Ca; the hole conduction layer 6 can also be a composite structure formed by periodically alternating growth of undoped AlN sublayers and AlN sublayers doped with Mg / Zn; the hole conduction layer 6 can also be a composite structure formed by periodically alternating growth of undoped AlN sublayers and AlN sublayers doped with Mg / Sr; the hole conduction layer 6 can also be a composite structure formed by periodically alternating growth of undoped AlN sublayers and AlN sublayers doped with Ca / Zn; the hole conduction layer 6 can also be a composite structure formed by periodically alternating growth of undoped AlN sublayers and AlN sublayers doped with Ca / Sr; the hole conduction layer 6 can also be a composite structure formed by periodically alternating growth of undoped AlN sublayers and AlN sublayers doped with Zn / Sr.

[0031] Exemplarily, the hole conduction layer 6 can also be a composite structure formed by periodically alternating growth of undoped AlN sublayers and AlN sublayers doped with Mg / Ca / Zn; the hole conduction layer 6 can also be a composite structure formed by periodically alternating growth of undoped AlN sublayers and AlN sublayers doped with Mg / Ca / Sr; the hole conduction layer 6 can also be a composite structure formed by periodically alternating growth of undoped AlN sublayers and AlN sublayers doped with Ca / Zn / Sr; the hole conduction layer 6 can also be a composite structure formed by periodically alternating growth of undoped AlN sublayers and AlN sublayers doped with Mg / Zn / Sr.

[0032] In an embodiment of the present invention, the hole-conducting layer 6 is a composite structure formed by periodically growing any two, three, four, or five of an undoped AlN sub-layer, an AlN sub-layer doped with Mg, an AlN sub-layer doped with Ca, an AlN sub-layer doped with Zn, and an AlN sub-layer doped with Sr in an alternating manner. Exemplarily, the hole-conducting layer 6 can be a composite structure formed by periodically growing an undoped AlN sub-layer, an AlN sub-layer doped with Mg, and an AlN sub-layer doped with Ca in an alternating manner; the hole-conducting layer 6 can be a composite structure formed by periodically growing an undoped AlN sub-layer, an AlN sub-layer doped with Mg, an AlN sub-layer doped with Ca, an AlN sub-layer doped with Zn, and an AlN sub-layer doped with Sr in an alternating manner, and so on. It should be noted that the above examples are not limitations to the present invention, and the AlN sub-layers can be combined in any order.

[0033] In an embodiment of the present invention, the doping of alkaline earth metal elements Mg, Ca, Zn, and Sr in the hole-conducting layer 6 is carried out under nitrogen-rich conditions, and the molar ratio of group V elements to group III elements is greater than 20000.

[0034] In an embodiment of the present invention, the doping concentration of alkaline earth metal elements Mg, Ca, Zn, and Sr in the hole-conducting layer 6 is 0.01% - 0.5%.

[0035] In an embodiment of the present invention, the growth temperature of the hole-conducting layer 6 is 800°C - 1100°C.

[0036] Correspondingly, an embodiment of the present invention further provides an epitaxial growth method for an LED epitaxial wafer, which is used to prepare the above-mentioned deep ultraviolet LED epitaxial wafer. Refer to Figure 2 , which is a flowchart for implementing an epitaxial growth method for an LED epitaxial wafer provided by an embodiment of the present invention, and specifically includes the following steps:

[0037] S1. Provide a substrate.

[0038] S2. Grow an AlGaN buffer layer on the substrate.

[0039] S3. Grow an undoped AlGaN layer on the side of the AlGaN buffer layer away from the substrate.

[0040] S4. Grow an N-type AlGaN layer on the side of the undoped AlGaN layer away from the substrate.

[0041] S5. Grow a multi-quantum well layer on the side of the N-type AlGaN layer away from the substrate.

[0042] S6. Grow a hole-conducting layer on the side of the multi-quantum well layer away from the substrate.

[0043] S7. Grow a P-type AlGaN layer on the side of the hole conduction layer away from the substrate.

[0044] S8. Grow a P-type contact layer on the side of the P-type AlGaN layer away from the substrate.

[0045] In an embodiment of the present invention, the number of repeating units provided by the present invention can be 2 - 100, and the present invention does not make specific limitations thereon.

[0046] It can be understood that the hole conduction layer fabricated by the technical solution provided in the embodiment of the present invention is composed of a plurality of two-dimensional AlN sub-layers grown periodically in an alternating manner. Among them, some AlN sub-layers in the hole conduction layer are doped with alkaline earth metal elements, and the alkaline earth metal elements are any one or a combination of several of Mg, Ca, Zn, and Sr.

[0047] The growth method of the deep ultraviolet LED epitaxial structure provided in the embodiment of the present invention will be described in more detail below. Among them, the growth method of the deep ultraviolet LED epitaxial structure provided in the embodiment of the present invention includes:

[0048] S1. Provide a substrate.

[0049] In an embodiment of the present invention, the substrate provided by the present invention can be a sapphire substrate. Among them, epitaxial growth is carried out on the c-plane of the sapphire substrate using an MOCVD machine.

[0050] S2. Grow an AlGaN buffer layer on the substrate.

[0051] In an embodiment of the present invention, when growing the AlGaN buffer layer, the MO sources used are TMGa and TMAl, the gas source is NH 3 , and H 2 is used as the carrier gas.

[0052] S3. Grow an undoped AlGaN layer on the side of the AlGaN buffer layer away from the substrate.

[0053] In an embodiment of the present invention, when growing the undoped AlGaN layer, the MO sources used are TMGa and TMAl, the gas source is NH 3 , and H 2 is used as the carrier gas.

[0054] S4. Grow an N-type AlGaN layer on the side of the undoped AlGaN layer away from the substrate.

[0055] S5. Grow a multi-quantum well layer on the side of the N-type AlGaN layer away from the substrate.

[0056] In an embodiment of the present invention, the multiple quantum well layer provided by the present invention may be an Al x Ga (1-x) N layer / Al y Ga (1-y) N layer multiple quantum well structure. The Al x Ga (1-x) N layer is a quantum well, and the Al y Ga (1-y) N is a quantum barrier layer, where 0 < x < y < 1.

[0057] Optionally, when growing the Al x Ga (1-x) N layer / Al y Ga (1-y) N layer multiple quantum well structure, the MO sources used are TMGa, TMAl, and the gas source is NH 3 , and H 2 is used as the carrier gas.

[0058] S6. Grow a hole conduction layer on the side of the multiple quantum well layer away from the substrate.

[0059] In an embodiment of the present invention, the hole conduction layer provided by the present invention may be a hole conduction layer formed by periodically and alternately growing a plurality of two-dimensional AlN sub-layers. Among them, some of the AlN sub-layers in the hole conduction layer are doped with alkaline earth metal elements, and the alkaline earth metal elements are any one or a combination of several of Mg, Ca, Zn, and Sr.

[0060] Specifically, the doping of alkaline earth metal elements Mg, Ca, Zn, and Sr in the hole conduction layer is carried out under nitrogen-rich conditions, the molar ratio of group V elements to group III elements is greater than 20000, the doping concentration of alkaline earth metal elements Mg, Ca, Zn, and Sr in the hole conduction layer is 0.01% - 0.5%, and in addition, the growth temperature of the hole conduction layer is 800°C - 1100°C.

[0061] S7. Grow a P-type AlGaN layer on the side of the hole conduction layer away from the substrate.

[0062] In an embodiment of the present invention, when growing the P-type AlGaN layer provided by the present invention, the MO sources used may be TMGa, TMAl, Cp 2 Mg, the gas source is NH 3 , and H 2 is used as the carrier gas.

[0063] S8. Grow a P-type contact layer on the side of the P-type AlGaN layer away from the substrate.

[0064] In an embodiment of the present invention, the P-type contact layer provided by the present invention may be a P-type AlGaN contact layer. When growing the P-type AlGaN contact layer, the MO sources may be TMGa, TMAl, Cp 2 Mg, and the gas source may be NH 3 , and H 2 is used as the carrier gas.

[0065] The following is a further description of the present invention with specific embodiments:

[0066] Embodiment 1

[0067] The epitaxial growth method of the LED epitaxial wafer in this Embodiment 1 includes the following steps:

[0068] (1) Provide a substrate.

[0069] In an embodiment of the present invention, the substrate provided by the present invention may be a sapphire substrate. Among them, epitaxial growth is carried out on the c-plane of the sapphire substrate using an MOCVD machine.

[0070] (2) Grow an AlGaN buffer layer on the substrate.

[0071] In an embodiment of the present invention, when growing the AlGaN buffer layer, the MO sources are TMGa, TMAl, the gas source is NH 3 , and H 2 is used as the carrier gas.

[0072] (3) Grow an undoped AlGaN layer on the side of the AlGaN buffer layer away from the substrate.

[0073] In an embodiment of the present invention, when growing the undoped AlGaN layer, the MO sources may be TMGa, TMAl, the gas source is NH 3 , and H 2 is used as the carrier gas.

[0074] (4) Grow an N-type AlGaN layer on the side of the undoped AlGaN layer away from the substrate.

[0075] (5) Grow a multi-quantum well layer on the side of the N-type AlGaN layer away from the substrate.

[0076] In an embodiment of the present invention, the multi-quantum well layer provided by the present invention may be a multi-quantum well structure of Al x Ga (1-x) N layer / Al y Ga (1-y) N layer, the Al x Ga (1-x) N layer is the quantum well, and the Al y Ga (1-y)N is the quantum barrier layer, 0 <x<y<1。

[0077] Optionally, the embodiment of the present invention grows Al x Ga (1-x) N layer / Al y Ga (1-y) In the multi-quantum well structure of N layer, the MO source used is TMGa, TMAl, and the gas source is NH 3 , and H 2 As carrier gas.

[0078] (6) Growing a hole conduction layer on the side of the multi-quantum well layer facing away from the substrate.

[0079] Specifically, first, a two-dimensional AlN sublayer doped with Mg is grown on the side of the multi-quantum well layer away from the substrate, and then a two-dimensional AlN sublayer doped with Zn is grown on the side of the two-dimensional AlN sublayer doped with Mg away from the substrate. This growth process is one cycle, and a total of 10 cycles are grown.

[0080] (7) Growing a P-type AlGaN layer on the side of the hole conduction layer facing away from the substrate.

[0081] In one embodiment of the present invention, the P-type AlGaN layer provided by the present invention can be grown using MO sources such as TMGa, TMAl, and Cp2Mg, and gas sources such as NH 3 , and H 2 As carrier gas.

[0082] (8) Growing a P-type contact layer on the side of the P-type AlGaN layer facing away from the substrate.

[0083] In one embodiment of the present invention, the P-type contact layer provided by the present invention may be a P-type AlGaN contact layer. When the P-type AlGaN contact layer is grown, the MO source may be TMGa, TMAl, Cp 2 Mg, gas source is NH 3 , and H 2 As carrier gas.

[0084] Example 2

[0085] This embodiment 2 also provides an epitaxial growth method for an LED epitaxial wafer, which differs from embodiment 1 in that, in step (6), first, a layer of undoped two-dimensional AlN sublayer is grown on the side of the multi-quantum well layer away from the substrate, and then a layer of Mg-doped two-dimensional AlN sublayer is grown on the side of the undoped two-dimensional AlN sublayer away from the substrate. This growth process is one cycle, and a total of 10 cycles are grown.

[0086] Example 3

[0087] Embodiment 3 also provides an epitaxial growth method for an LED epitaxial wafer. The difference from Embodiment 1 is that in step (6), first, an undoped two-dimensional AlN sub-layer is grown on the side of the multi-quantum well layer facing away from the substrate, and then a two-dimensional AlN sub-layer doped with both Zn / Mg is grown on the side of the undoped two-dimensional AlN sub-layer facing away from the substrate. This growth process is one cycle, and a total of 10 cycles are grown.

[0088] Embodiment 4

[0089] Embodiment 4 also provides an epitaxial growth method for an LED epitaxial wafer. The difference from Embodiment 1 is that in step (6), first, an undoped two-dimensional AlN sub-layer is grown on the side of the multi-quantum well layer facing away from the substrate, and then a two-dimensional AlN sub-layer doped with Mg is grown on the side of the undoped two-dimensional AlN sub-layer facing away from the substrate. Finally, a two-dimensional AlN sub-layer doped with Zn is grown on the side of the two-dimensional AlN sub-layer doped with Mg facing away from the substrate. This growth process is one cycle, and a total of 10 cycles are grown.

[0090] Embodiment 5

[0091] Embodiment 5 also provides an epitaxial growth method for an LED epitaxial wafer. The difference from Embodiment 1 is that in step (6), first, an undoped two-dimensional AlN sub-layer is grown on the side of the multi-quantum well layer facing away from the substrate, and then a two-dimensional AlN sub-layer doped with Ca is grown on the side of the undoped two-dimensional AlN sub-layer facing away from the substrate. This growth process is one cycle, and a total of 10 cycles are grown.

[0092] Embodiment 6

[0093] Embodiment 6 also provides an epitaxial growth method for an LED epitaxial wafer. The difference from Embodiment 1 is that in step (6), first, an undoped two-dimensional AlN sub-layer is grown on the side of the multi-quantum well layer facing away from the substrate, and then a two-dimensional AlN sub-layer doped with Sr is grown on the side of the undoped two-dimensional AlN sub-layer facing away from the substrate. This growth process is one cycle, and a total of 10 cycles are grown.

[0094] The LED chips finally prepared in Embodiments 1 to 6 and the LED chips in the prior art are subjected to luminous efficacy tests under the same conditions. The results are shown in the following table:

[0095]

[0096] As can be seen from the table, when a single period in the hole conduction layer is composed of a two-dimensional AlN sub-layer doped with Mg and a two-dimensional AlN sub-layer doped with Zn, the light efficiency improvement is the highest compared with the prior art, which is 2%. For other combination methods, there are also improvements to varying degrees compared with the prior art.

[0097] An embodiment of the present invention further provides an LED chip, including the deep ultraviolet LED epitaxial wafer in any of the above embodiments.

[0098] The above embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the appended claims.

Claims

1. A deep ultraviolet LED epitaxial wafer, characterized in that, it includes a hole conduction layer, and the hole conduction layer is formed by periodically alternating growth of several two-dimensional AlN sub-layers. Among them, the hole conduction layer is a composite structure formed by periodically alternating growth of any two, three, four or five of the undoped AlN sub-layer, the AlN sub-layer doped with Mg, the AlN sub-layer doped with Ca, the AlN sub-layer doped with Zn, and the AlN sub-layer doped with Sr, and a total of 10 cycles are grown; or, the hole conduction layer is a composite structure formed by periodically alternating growth of an undoped AlN sub-layer and an AlN sub-layer doped with any combination of Mg, Ca, Zn, and Sr, and a total of 10 cycles are grown; the deep ultraviolet LED epitaxial wafer further includes a substrate, an AlGaN buffer layer, an undoped AlGaN, an N-type AlGaN layer, a multi-quantum well layer, a P-type AlGaN layer, and a P-type contact layer; the AlGaN buffer layer, the undoped AlGaN, the N-type AlGaN layer, the multi-quantum well layer, the hole conduction layer, the P-type AlGaN layer, and the P-type contact layer are epitaxially grown on the substrate in sequence.

2. The deep ultraviolet LED epitaxial wafer according to claim 1, characterized in that, the growth temperature of the hole conduction layer is 800 °C to 1100 °C.

3. An epitaxial growth method for an LED epitaxial wafer, characterized in that, it is used to prepare the deep ultraviolet LED epitaxial wafer according to any one of claims 1-2, and the epitaxial growth method includes: growing a hole conduction layer, and the hole conduction layer is formed by periodically alternating growth of several two-dimensional AlN sub-layers. Among them, the hole conduction layer is a composite structure formed by periodically alternating growth of any two, three, four or five of the undoped AlN sub-layer, the AlN sub-layer doped with Mg, the AlN sub-layer doped with Ca, the AlN sub-layer doped with Zn, and the AlN sub-layer doped with Sr; or, the hole conduction layer is a composite structure formed by periodically alternating growth of an undoped AlN sub-layer and an AlN sub-layer doped with any combination of Mg, Ca, Zn, and Sr; the deep ultraviolet LED epitaxial wafer further includes a substrate, an AlGaN buffer layer, an undoped AlGaN, an N-type AlGaN layer, a multi-quantum well layer, a P-type AlGaN layer, and a P-type contact layer; the AlGaN buffer layer, the undoped AlGaN, the N-type AlGaN layer, the multi-quantum well layer, the hole conduction layer, the P-type AlGaN layer, and the P-type contact layer are epitaxially grown on the substrate in sequence.

4. An LED chip, characterized in that, it includes the deep ultraviolet LED epitaxial wafer according to any one of claims 1-2.

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