Epitaxial structure of ultraviolet light-emitting device and manufacturing method therefor, and ultraviolet light-emitting device

Abstract

The present invention relates to an epitaxial structure of an ultraviolet light-emitting device and a manufacturing method therefor, and an ultraviolet light-emitting device, belonging to the technical field of semiconductors. The epitaxial structure comprises a substrate, an AlN layer, a n-type electron transport layer, a multi-quantum well light-emitting layer, an electron blocking layer, a p-type hole transport layer and a p-type contact layer which are sequentially grown from bottom to top; the p-type hole transport layer comprises at least one polarity change layer and a metal polarity layer; the polarity change layer comprises a polarity gradient layer and a polarity inversion layer grown on the polarity gradient layer; the metal polarity layer is grown on the polarity inversion layer of the uppermost polarity change layer; the polarity gradient layer gradually changes from a metal polarity to a nitrogen polarity from bottom to top, and the polarity inversion layer changes from the nitrogen polarity to the metal polarity from bottom to top. The present invention can increase the hole carrier concentration and the vertical migration rate, reduce the resistivity of p-type hole transport layers, and further improve the photoelectric conversion efficiency of ultraviolet light-emitting devices.

Description

Epitaxial structure of ultraviolet light-emitting device and preparation method thereof, and ultraviolet light-emitting device TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor, in particular to an epitaxial structure of ultraviolet light-emitting device and preparation method thereof, and ultraviolet light-emitting device. BACKGROUND

[0002] The ultraviolet light-emitting device has the advantages of environmental protection, energy saving, single light-emitting wavelength, etc., and can be applied in sterilization and disinfection, biological detection, etc.

[0003] In the epitaxial structure of the existing ultraviolet light-emitting device, the p-type hole transport layer mainly adopts a single-component p-type AlGaN thin layer. The hole concentration of the p-type hole transport layer with this structure is low, resulting in a high resistivity of the layer. In order to improve the hole concentration, the current technology adopts an AlGaN superlattice method to obtain a high in-plane carrier concentration and a high migration rate. However, the potential barrier difference between the wells and barriers of the superlattice makes the hole migration rate in the vertical direction (towards the quantum well direction) poor, resulting in a small amount of holes actually entering the quantum well. In addition, there is also a pAlGaN layer with gradually changing Al components from high to low as the p-type hole transport layer. This structure can polarize and induce a certain amount of hole carriers, and realize vertical transmission of the hole carriers. However, due to the small difference in polarization intensity between AlN and GaN, the polarization-induced hole carriers are limited.

[0004] In summary, the current epitaxial structure of the ultraviolet light-emitting device has the problems of low hole carrier concentration, low vertical migration rate of the hole carriers, and high resistivity of the p-type hole transport layer, resulting in a low photoelectric conversion efficiency of the current ultraviolet light-emitting device. SUMMARY

[0005] To solve the above technical problems, the present application provides an epitaxial structure of ultraviolet light-emitting device and preparation method thereof, and ultraviolet light-emitting device. The technical scheme of the present application is as follows:

[0006] In a first aspect, an epitaxial structure of ultraviolet light-emitting device is provided, which comprises, from bottom to top, a substrate, an AlN layer, an n-type electron transport layer, a multi-quantum well light-emitting layer, an electron blocking layer, a p-type hole transport layer, and a p-type contact layer.

[0007] The p-type hole transport layer comprises at least one group of polarity change layers and a metal polarity layer. The polarity change layer comprises a polarity gradient layer and a polarity inversion layer grown on the polarity gradient layer. The metal polarity layer is grown on the polarity inversion layer of the uppermost polarity change layer. The polarity gradient layer gradually changes from metal polarity to nitrogen polarity from bottom to top. The polarity inversion layer changes from nitrogen polarity to metal polarity from bottom to top.

[0008] Preferably, in the set of polarity change layers, the thickness of the polarity gradual change layer is 1-500 nm, and the thickness of the polarity reversal layer is 0.1-10 nm.

[0009] Preferably, the Si doping concentration of the n-type electron transport layer is 1×10 18 -1×10 20 cm -3 .

[0010] Preferably, the Al component content in the polarity gradual change layer remains unchanged, or changes from high to low from bottom to top.

[0011] Preferably, in the polarity gradual change layer, the Mg doping concentration gradually changes from 1×10 20 cm -3 to 1×10 21 cm -3 ; and in the metal polarity layer, the Mg doping concentration is 1×10 18 -1×10 20 cm -3 .

[0012] Preferably, the thickness of the AlN layer is 100-5000 nm, the thickness of the n-type electron transport layer is 100-5000 nm, the thickness of the electron blocking layer is 1-50 nm, the thickness of the p-type hole transport layer is 10-200 nm, and the thickness of the p-type contact layer is 1-100 nm.

[0013] Preferably, the Al component content of the electron blocking layer is 0.4-1.0, and the Al component content of the p-type hole transport layer is 0.4-1.0; the number of periods of the multi-quantum well light-emitting layer is 1-10, the barrier layer has a thickness of 3-50 nm and an Al component content of 0.4-0.7, and the well layer has a thickness of 1-5 nm and an Al component content of 0.3-0.6.

[0014] In a second aspect, a preparation method of an epitaxial structure of an ultraviolet light-emitting device is provided, the epitaxial structure of the ultraviolet light-emitting device being the epitaxial structure of the ultraviolet light-emitting device described in the first aspect, and the preparation method comprising:

[0015] S1, growing an AlN layer on a substrate;

[0016] S2, growing an n-type electron transport layer on the AlN layer;

[0017] S3, growing a multi-quantum well light-emitting layer on the n-type electron transport layer;

[0018] S4, growing an electron blocking layer on the multi-quantum well light-emitting layer;

[0019] S5, growing a p-type hole transport layer on the electron blocking layer;

[0020] S6, growing a p-type contact layer on the p-type hole transport layer.

[0021] Preferably, the S5 comprises: growing at least one set of polarity change layer and metal polarity layer in turn from bottom to top, and growing a polarity gradient layer and a polarity reversal layer in turn from bottom to top when growing each set of polarity change layer.

[0022] In a third aspect, an ultraviolet light emitting device is provided, which comprises the epitaxial structure of the ultraviolet light emitting device according to the first aspect.

[0023] All the optional technical solutions described above can be combined in any manner, and the present application does not describe the structure after combination in detail.

[0024] Through the above-mentioned scheme, the beneficial effects of the present application are as follows:

[0025] By setting the p-type hole transport layer to comprise at least one set of polarity change layer and metal polarity layer, the polarity change layer comprising a polarity gradient layer and a polarity reversal layer grown on the polarity gradient layer, and the metal polarity layer grown on the polarity reversal layer of the uppermost polarity change layer, and the polarity gradient layer gradually changing from metal polarity to nitrogen polarity from bottom to top, and the polarity reversal layer changing from nitrogen polarity to metal polarity from bottom to top, since the metal polarity and the nitrogen polarity surfaces have polarization field strengths with opposite polarization directions, the polarization intensity difference of the polarity gradient layer is large, so that after the polarity gradient layer induces more hole carriers, the hole carriers tunnel through the polarization reversal layer, thereby the hole carrier concentration and the longitudinal migration rate can be improved, the resistivity of the p-type hole transport layer can be reduced, and the photoelectric conversion efficiency of the ultraviolet light emitting device can be improved.

[0026] The above description is only a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application, and to implement the content of the description, the following will be described in detail with the preferred embodiments of the present application and with the aid of the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0027] FIG. 1 is a structural schematic diagram of an epitaxial structure of an ultraviolet light emitting device according to an embodiment of the present application.

[0028] FIG. 2 is a structural schematic diagram of a p-type hole transport layer according to an embodiment of the present application.

[0029] FIG. 3 is a structural schematic diagram of a p-type hole transport layer according to another embodiment of the present application. DETAILED DESCRIPTION

[0030] The specific embodiments of the present application will be further described in detail below in combination with the drawings and examples. The following examples are used to illustrate the present application, but are not used to limit the scope of the present application.

[0031] As shown in FIGS. 1-3, the present application provides an epitaxial structure of an ultraviolet light-emitting device, which comprises, from bottom to top, a substrate 1, an AlN layer 2, an n-type electron transport layer 3, a multi-quantum well light-emitting layer 4, an electron blocking layer 5, a p-type hole transport layer 6, and a p-type contact layer 7;

[0032] The p-type hole transport layer 6 comprises at least one set of a polarity variation layer and a metal polarity layer 6-3, the polarity variation layer comprises a polarity gradient layer 6-1 and a polarity inversion layer 6-2 grown on the polarity gradient layer 6-1, and the metal polarity layer 6-3 is grown on the polarity inversion layer 6-2 of the uppermost polarity variation layer, the polarity gradient layer 6-1 gradually changes from metal polarity to nitrogen polarity from bottom to top, and the polarity inversion layer 6-2 changes from nitrogen polarity to metal polarity (aluminum polarity) from bottom to top.

[0033] In the above, the substrate 1 can be a sapphire substrate; the n-type electron transport layer 3 is an n-type doped AlGaN layer; the electron blocking layer 5 is an AlGaN layer; the p-type hole transport layer 6 is a p-type doped AlGaN layer; and the p-type contact layer 7 is a p-type doped GaN layer. In the above layers, the source of Ga is trimethyl gallium and triethyl gallium, the source of Al is trimethyl aluminum, and the source of N is ammonia; silane and dimethyl magnesium are used as n-type and p-type dopants, respectively.

[0034] Specifically, the lower surface of the polarity gradient layer 6-1 is a metal polarity surface, and the upper surface is a nitrogen polarity surface, and the polarities of the upper and lower surfaces of the polarity inversion layer 6-2 are opposite. Since the metal polarity surface and the nitrogen polarity surface have polarization fields with opposite directions, the polarization intensity difference of the polarity gradient layer 6-1 is large, and then the hole carriers are induced in the polarity gradient layer 6-1, and the hole carriers tunnel through the polarity inversion layer 6-2, thereby increasing the hole carrier concentration and the longitudinal migration rate, reducing the resistivity of the p-type hole transport layer 6, and further improving the photoelectric conversion efficiency of the ultraviolet light-emitting device. The setting of the metal polarity layer 6-3 can ensure the growth quality of the p-type contact layer 7 thereon.

[0035] In one specific embodiment, the p-type hole transport layer 6 comprises one set of a polarity variation layer and a metal polarity layer 6-3, as shown in FIG. 2; in another specific embodiment, the p-type hole transport layer 6 comprises several sets of a polarity variation layer and a metal polarity layer 6-3, as shown in FIG. 3. Compared with one set of a polarity variation layer, the setting of several sets of a polarity variation layer can induce more hole carriers, thereby further increasing the hole carrier concentration.

[0036] In one specific embodiment, the polarity change of the polarity gradient layer 6-1 from bottom to top is achieved by controlling the Mg doping concentration, and the Mg doping concentration of the polarity gradient layer 6-1 gradually changes from 1×1018cm-3 to 1×1019cm-3 from bottom to top. 20 cm-3 gradually changes to 1 x 10 21 cm -3 The Mg doping concentration change mode of such a high doping concentration can make the polarity of the polarity gradient layer 6-1 gradually change from metal polarity to nitrogen polarity. In the metal polarity layer 6-3, the Mg doping concentration is 1 x 10 18 -1 x 10 20 cm -3 , and the lower Mg doping concentration can maintain the metal polarity. The metal atoms of the polarity inversion layer 6-2 can be composed of Al, Ga, Mg, etc., or only Mg.

[0037] In one specific embodiment, in a set of polarity change layers, the thickness of the polarity gradient layer 6-1 is 1-500 nm, and the thickness of the polarity inversion layer 6-2 is 0.1-10 nm. The thinner polarity inversion layer 6-2 is conducive to the tunneling of hole carriers.

[0038] In one specific embodiment, the Si doping concentration of the n-type electron transport layer 3 is 1 x 10 18 -1 x 10 20 cm -3 .

[0039] In one specific embodiment, the Al component content in the polarity gradient layer 6-1 can remain unchanged or change from high to low from bottom to top. When the Al component content changes from high to low from bottom to top, a certain amount of hole carriers can be further polarized and induced on the basis of the hole carriers induced on the metal polarity surface and the nitrogen polarity surface of the polarity gradient layer 6-1, thereby further increasing the hole carrier concentration.

[0040] In one specific embodiment, the thickness of the AlN layer 2 is 100-5000 nm, the thickness of the n-type electron transport layer 3 is 100-5000 nm, the thickness of the electron blocking layer 5 is 1-50 nm, the thickness of the p-type hole transport layer 6, i.e., the total thickness of at least one set of polarity change layers and the metal polarity layer 6-3, is 10-200 nm, and the thickness of the p-type contact layer 7 is 1-100 nm.

[0041] In one specific embodiment, the Al component content of the electron blocking layer 5 is 0.4-1.0, and the Al component content of the p-type hole transport layer 6 is 0.4-1.0; the multi-quantum well light-emitting layer 4 is grown by alternately growing barrier layers and well layers, one barrier layer and one well layer form a period, the number of periods of the multi-quantum well light-emitting layer 4 is 1-10, the thickness of the barrier layer is 3-50 nm, and the Al component content is 0.4-0.7, the thickness of the well layer is 1-5 nm, and the Al component content is 0.3-0.6.

[0042] The application further provides a preparation method of the epitaxial structure of the ultraviolet light-emitting device.

[0043] S1, growing an AlN layer 2 on the substrate 1;

[0044] S2, growing an n-type electron transport layer 3 on the AlN layer 2;

[0045] S3, growing a multi-quantum well light-emitting layer 4 on the n-type electron transport layer 3;

[0046] S4, growing an electron blocking layer 5 on the multi-quantum well light-emitting layer 4;

[0047] S5, growing a p-type hole transport layer 6 on the electron blocking layer 5;

[0048] S6, growing a p-type contact layer 7 on the p-type hole transport layer 6.

[0049] In the growth of the layers, the MOCVD equipment is used.

[0050] In the implementation of S1, the substrate 1 is placed in the MOCVD equipment, hydrogen is introduced into the MOCVD equipment, the temperature of the MOCVD equipment is controlled to be 1200-1500 ℃, the substrate 1 is high-temperature cleaned, and then nitrogen and trimethylaluminum are introduced for growth.

[0051] In the implementation of S2, the growth temperature of the MOCVD equipment is controlled to be 900-1300 ℃, and ammonia, silane, trimethylgallium, trimethylaluminum and hydrogen are introduced during growth.

[0052] In the implementation of S3, the growth temperature of the MOCVD equipment is controlled to be 900-1100 ℃, ammonia, silane, trimethylgallium, trimethylaluminum and hydrogen are introduced during growth, and the barrier layer and the well layer are alternately grown.

[0053] In the implementation of S4, the growth temperature of the MOCVD equipment is controlled to be 900-1100 ℃, and ammonia, silane, trimethylgallium, trimethylaluminum and hydrogen are introduced during growth.

[0054] In the implementation of S5, at least one group of polarity change layers and metal polarity layers 6-3 are sequentially grown from bottom to top, and the polarity gradual change layer 6-1 and the polarity inversion layer 6-2 are sequentially grown from bottom to top during the growth of each group of polarity change layers.

[0055] During the growth of the polarity gradual change layer 6-1, the Mg doping concentration is gradually changed from 1×10 20 cm -3 to 1×10 21 cm-3 When the growth polarity of the layer 6-2 is reversed, the Ga source and the Al source can be closed and only Mg metal atoms are deposited, so that the polarity is changed from the nitrogen polarity to the metal polarity; when the metal polarity layer 6-3 is grown, the Mg doping concentration is controlled to be 1×10 18 -1×10 20 cm -3 .

[0056] S5, in the specific growth, is grown at a temperature of 900-1100℃ and a pressure of 20-100torr, with pure H2 as the carrier gas, and ammonia, nitrogen, dimethyl magnesium and trimethyl gallium are introduced during the growth, and the V / III molar ratio is controlled to be 100-10000 and the Mg / III molar ratio is controlled to be 1000-50000.

[0057] S6, in the specific implementation, comprises: controlling the growth temperature of the MOCVD equipment to be 800-1000℃, and introducing ammonia, nitrogen, dimethyl magnesium and trimethyl gallium during the growth.

[0058] The embodiment of the present application further provides an ultraviolet light emitting device, which comprises the epitaxial structure of the ultraviolet light emitting device described in the above embodiment. The ultraviolet light emitting device in the embodiment of the present application can improve the hole carrier concentration and the longitudinal migration rate, reduce the p-type hole transport layer resistivity, and further improve the photoelectric conversion efficiency of the ultraviolet light emitting device by adopting the epitaxial structure of the ultraviolet light emitting device.

[0059] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and it should be noted that, for those skilled in the art, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should also be considered as the protection scope of the present application.

Claims

1. An epitaxial structure for an ultraviolet light emitting device, comprising: The ultraviolet light-emitting device comprises, from bottom to top, a substrate (1), an AlN layer (2), an n-type electron transport layer (3), a multi-quantum well light-emitting layer (4), an electron blocking layer (5), a p-type hole transport layer (6) and a p-type contact layer (7); The p-type hole transport layer (6) comprises at least one set of polarity change layers and a metal polarity layer (6-3), the polarity change layers comprise a polarity gradient layer (6-1) and a polarity inversion layer (6-2) grown on the polarity gradient layer (6-1), and the metal polarity layer (6-3) is grown on the polarity inversion layer (6-2) of the uppermost polarity change layer, the polarity gradient layer (6-1) gradually changes from metal polarity to nitrogen polarity from bottom to top, and the polarity inversion layer (6-2) changes from nitrogen polarity to metal polarity from bottom to top.

2. The epitaxial structure for an ultraviolet light emitting device according to claim 1, wherein In the set of polarity change layers, the thickness of the polarity gradient layer (6-1) is 1-500 nm, and the thickness of the polarity inversion layer (6-2) is 0.1-10 nm.

3. The epitaxial structure of an ultraviolet light emitting device according to claim 1, wherein The Si doping concentration of the n-type electron transport layer (3) is 1 x 10 18 -1 x 10 20 cm -3 .

4. The epitaxial structure for an ultraviolet light emitting device according to claim 1, wherein The Al component content in the polarity gradient layer (6-1) remains unchanged, or changes from high to low from bottom to top.

5. The epitaxial structure for an ultraviolet light emitting device of claim 1, wherein, In the polar gradient layer (6-1), the Mg doping concentration is gradually changed from 1×10 20 cm -3 to 1×10 21 cm -3 from bottom to top; in the metal polar layer (6-3), the Mg doping concentration is 1×10 18 -1×10 20 cm -3 .

6. The epitaxial structure for an ultraviolet light emitting device of claim 1, wherein, The thickness of the AlN layer (2) is 100-5000 nm, the thickness of the n-type electron transport layer (3) is 100-5000 nm, the thickness of the electron blocking layer (5) is 1-50 nm, the thickness of the p-type hole transport layer (6) is 10-200 nm, and the thickness of the p-type contact layer (7) is 1-100 nm.

7. The epitaxial structure for ultraviolet light emitting devices according to claim 1, wherein The Al component content of the electron blocking layer (5) is 0.4-1.0, and the Al component content of the p-type hole transport layer (6) is 0.4-1.0; the number of periods of the multi-quantum well light-emitting layer (4) is 1-10, the barrier layer has a thickness of 3-50 nm and an Al component content of 0.4-0.7, and the well layer has a thickness of 1-5 nm and an Al component content of 0.3-0.

6.

8. A method of producing an epitaxial structure of an ultraviolet light emitting device as claimed in any one of claims 1 to 7, characterized by, The method comprises the following steps: S1, growing an AlN layer (2) on a substrate (1); S2, growing an n-type electron transport layer (3) on the AlN layer (2); S3, growing a multi-quantum well light-emitting layer (4) on the n-type electron transport layer (3); S4, growing an electron blocking layer (5) on the multi-quantum well light-emitting layer (4); S5, growing a p-type hole transport layer (6) on the electron blocking layer (5); S6, growing a p-type contact layer (7) on the p-type hole transport layer (6).

9. The production method according to claim 8, characterized by, The S5 comprises: Growing at least one set of polarity change layers and a metal polarity layer (6-3) from bottom to top, and growing a polarity gradient layer (6-1) and a polarity inversion layer (6-2) from bottom to top when growing each set of polarity change layers.

10. An ultraviolet light emitting device, characterized by comprising: The method comprises the following steps: The method comprises the following steps: The method comprises the following steps:

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