Light emitting diode epitaxial wafer and preparation method thereof, and light emitting diode

Abstract

The application discloses a light emitting diode epitaxial wafer and a preparation method thereof and a light emitting diode. The light emitting diode epitaxial wafer comprises a substrate and a composite buffer layer, a non-doped GaN layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer and a P-type GaN layer deposited on the substrate in sequence; and the composite buffer layer comprises an graphene oxide layer, an AlON layer, an AlInN layer and an N-polar three-dimensional AlGaN layer. The application can reduce the dislocation density of the epitaxial layer, release the stress between the substrate and the GaN epitaxial layer, improve the epitaxial quality, reduce the non-radiation recombination caused by defects, and thus improve the light emitting efficiency of the light emitting diode.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a light-emitting diode epitaxial wafer and its fabrication method, and a light-emitting diode. Background Technology

[0002] LED epitaxial structures using sapphire as a substrate typically include an AlN buffer layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, and a P-type GaN layer. While using an AlN buffer layer can improve the crystal quality of the GaN epitaxial layer, the non-conductive nature of sapphire means that GaN-based LED chips using it as a substrate can generally only be fabricated with a single-sided structure. Furthermore, sapphire's poor thermal conductivity increases the difficulty of device packaging, leading to increased junction temperature during operation and a decrease in the LED chip's photoelectric performance. Moreover, the sapphire substrate is difficult to peel off, increasing the difficulty and cost of subsequent chip manufacturing and device packaging. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a light-emitting diode epitaxial wafer that facilitates substrate stripping, improves the thermal conductivity of the LED chip, improves the crystal quality of the GaN epitaxial layer, reduces non-radiative recombination caused by defects, and improves the luminous efficiency of the light-emitting diode.

[0004] The technical problem to be solved by the present invention is to provide a method for preparing an epitaxial wafer of a light-emitting diode, which produces a light-emitting diode with high luminous efficiency.

[0005] To achieve the above-mentioned technical effects, the present invention provides a light-emitting diode epitaxial wafer, comprising a substrate and a composite buffer layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer and a P-type GaN layer sequentially deposited on the substrate; the composite buffer layer comprises a graphene oxide layer, an AlON layer, an AlInN layer and an N-polar three-dimensional AlGaN layer.

[0006] As an improvement to the above technical solution, the thickness of the graphene oxide layer is 1 nm to 100 nm.

[0007] As an improvement to the above technical solution, the proportion of O component in the AlON layer is 0.01 to 0.5.

[0008] The thickness of the AlON layer is 5nm to 50nm.

[0009] As an improvement to the above technical solution, in the AlON layer, the proportion of O component gradually decreases along the epitaxial direction.

[0010] As an improvement to the above technical solution, the proportion of Al component in the AlInN layer is 0.5 to 0.9.

[0011] The thickness of the AlInN layer is 1 nm to 100 nm.

[0012] As an improvement to the above technical solution, in the AlInN layer, the proportion of Al component gradually decreases along the epitaxial direction.

[0013] As an improvement to the above technical solution, the proportion of Al component in the N-polar three-dimensional AlGaN layer is 0.01 to 0.5.

[0014] The thickness of the N-polar three-dimensional AlGaN layer is 50 nm to 500 nm.

[0015] Accordingly, the present invention also discloses a method for preparing a light-emitting diode epitaxial wafer, which includes the following steps:

[0016] A substrate is provided on which a composite buffer layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, and a P-type GaN layer are sequentially grown; the composite buffer layer includes a graphene oxide layer, an AlON layer, an AlInN layer, and an N-polar three-dimensional AlGaN layer.

[0017] As an improvement to the above technical solution, the deposition temperature of the graphene oxide layer is 800℃~1000℃, the deposition pressure is 50Torr~100Torr, and O2 is introduced after deposition for oxidation treatment at a temperature of 800℃~1000℃.

[0018] The deposition temperature of the AlON layer is 500℃~700℃, and the deposition pressure is 50Torr~300Torr;

[0019] The deposition temperature of the AlInN layer is 800℃~1000℃, and the deposition pressure is 50Torr~500Torr;

[0020] The deposition temperature of the N-polar three-dimensional AlGaN layer is 800℃~1000℃, the deposition pressure is 50Torr~300Torr, and after deposition, NH3 is introduced for treatment at a temperature of 800℃~1200℃.

[0021] Accordingly, the present invention also discloses a light-emitting diode, including the above-mentioned light-emitting diode epitaxial wafer.

[0022] Implementing the embodiments of the present invention has the following beneficial effects:

[0023] The buffer layer structure of the light-emitting diode provided by this invention includes a graphene oxide layer, an AlON layer, an AlInN layer, and an N-polar three-dimensional AlGaN layer. The graphene oxide layer possesses excellent mechanical, thermal, and optical properties, facilitating the complete peeling of the LED structure, dissipating heat from the LED chip accumulation, controlling crystal defects, and improving the quality of subsequent epitaxial growth. The AlON layer reduces GaN crystal growth on the PSS sidewalls, improves GaN crystal quality, and alleviates stress caused by lattice and thermal mismatch between the substrate and the epitaxial layer. The deposition of the AlInN layer alleviates the lattice mismatch between the AlON layer and the N-polar three-dimensional AlGaN layer, improving the crystal quality of the subsequently deposited N-polar three-dimensional AlGaN layer. Finally, the deposition of the N-polar three-dimensional AlGaN layer improves the semiconductor surface quality while reducing the linear dislocation density of the heterojunction epitaxial layer, reducing non-radiative recombination of electrons and holes, and improving the luminous efficiency of the light-emitting diode. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the light-emitting diode epitaxial wafer provided in an embodiment of the present invention;

[0025] Figure 2 This is a flowchart of the method for fabricating a light-emitting diode epitaxial wafer provided in an embodiment of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments.

[0027] like Figure 1 As shown, an embodiment of the present invention provides a light-emitting diode epitaxial wafer, including a substrate 1 and a composite buffer layer 2, an undoped GaN layer 3, an N-type GaN layer 4, a multiple quantum well layer 5, an electron blocking layer 6, and a P-type GaN layer 7 sequentially deposited on the substrate 1; the composite buffer layer 2 includes a graphene oxide layer, an AlON layer, an AlInN layer, and an N-polar three-dimensional AlGaN layer.

[0028] In one embodiment, the thickness of the graphene oxide layer is 1 nm to 100 nm. If the thickness of the graphene oxide layer is less than 1 nm, the subsequent growth quality cannot be improved; if the thickness of the graphene oxide layer is greater than 100 nm, it will result in waste. For example, the thickness of the graphene oxide layer is 1 nm, 5 nm, 10 nm, 20 nm, 50 nm, 80 nm, or 100 nm, but is not limited to these. The graphene oxide layer has excellent mechanical, thermal, and optical properties. Using the graphene oxide layer as a buffer layer can facilitate the complete peeling of the LED structure from the substrate. In addition, graphene oxide has excellent thermal conductivity, which can dissipate the heat accumulated in the LED chip.

[0029] In one embodiment, the O component in the AlON layer is 0.01 to 0.5%. If the O component percentage is less than 0.01, it cannot alleviate the stress between the substrate and the epitaxial layer; if the O component percentage is greater than 0.5, it will cause a decrease in crystal quality. For example, the O component percentage in the AlON layer is 0.01, 0.1, 0.2, 0.25, 0.3, 0.4, or 0.5, but is not limited thereto; preferably, the O component percentage is 0.01 to 0.1. In one embodiment, the thickness of the AlON layer is 5 nm to 50 nm. For example, the thickness of the AlON layer is 5 nm, 10 nm, 15 nm, 20 nm, 30 nm, 40 nm, or 50 nm, but is not limited thereto. Growing an AlON layer can control crystal defects, improve the quality of subsequent GaN crystal growth, and alleviate the stress caused by lattice mismatch and thermal mismatch between the substrate and the epitaxial layer. Furthermore, the AlON layer can also reduce GaN crystal growth on the PSS sidewalls, improving the quality of the GaN crystal.

[0030] In one embodiment, the proportion of O component in the AlON layer gradually decreases along the epitaxial direction, thereby ensuring the crystal quality of the AlON layer while preventing oxygen from penetrating into subsequent epitaxial structure layers.

[0031] In one embodiment, the Al content in the AlInN layer is 0.5 to 0.9%. Exemplary examples include 0.5, 0.55, 0.6, 0.7, 0.8, 0.85, or 0.9, but these are not limited to. The AlInN layer can improve the lattice matching between the AlON layer and the N-polar three-dimensional AlGaN layer. In one embodiment, the thickness of the AlInN layer is 1 nm to 100 nm. Exemplary examples include 1 nm, 10 nm, 20 nm, 50 nm, 70 nm, 90 nm, or 100 nm, but these are not limited to.

[0032] In one embodiment, the proportion of Al component in the AlInN layer gradually decreases along the epitaxial direction. By controlling the ratio of Al and In elements, the lattice mismatch between the AlON layer and the N-polar three-dimensional AlGaN layer is further reduced, thereby improving the crystal quality of the subsequently deposited N-polar three-dimensional AlGaN layer.

[0033] In one embodiment, the Al composition ratio in the N-polar three-dimensional AlGaN layer is 0.01 to 0.5. Exemplary examples include Al composition ratios of 0.01, 0.1, 0.2, 0.25, 0.3, 0.4, or 0.5, but these are not limited to. In one embodiment, the thickness of the N-polar three-dimensional AlGaN layer is 50 nm to 500 nm. Exemplary examples include thicknesses of 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 300 nm, or 500 nm, but these are not limited to. The deposited N-polar three-dimensional AlGaN layer effectively improves the crystal quality of the undoped GaN layer by controlling the nucleation density. Furthermore, the nitriding treatment to convert to N-polarity can improve the semiconductor surface quality while reducing the line dislocation density of the heterojunction epitaxial layer, reducing the polarization effect, and improving the luminous efficiency of the light-emitting diode.

[0034] Correspondingly, such as Figure 2 As shown, the present invention also provides a method for fabricating a light-emitting diode epitaxial wafer, comprising the following steps:

[0035] S100 provides a substrate.

[0036] S200 sequentially grows a composite buffer layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, and a P-type GaN layer on the substrate. The composite buffer layer includes a graphene oxide layer, an AlON layer, an AlInN layer, and an N-polar three-dimensional AlGaN layer.

[0037] In one embodiment, the method for preparing the graphene oxide layer includes the following steps:

[0038] PECVD was used to grow graphene layers, with the reaction chamber temperature controlled at 800℃~1000℃, pressure at 50Torr~100Torr, RF power at 15W~22W, and the reaction atmosphere consisting of CH4 and H2 with a flow ratio of 1:(1~20). After the graphene layer growth was completed, an oxidation treatment was performed in an O2 atmosphere to form a graphene oxide layer at a temperature of 800℃~1000℃.

[0039] In one embodiment, the method for preparing the AlON layer includes the following steps:

[0040] PVD growth was employed, with the reaction chamber temperature controlled at 500℃~700℃ and the pressure at 50Torr~300Torr. Ar was used as the protective gas, metallic Al was used as the sputtering target, and the reaction atmosphere consisted of O2 and N2 with a flow ratio of 1:(1~100).

[0041] Preferably, during the growth process, the flow ratio of O2 to N2 gradually decreases.

[0042] In one embodiment, the method for preparing the AlInN layer includes the following steps:

[0043] MOCVD growth was employed, with the reaction chamber temperature controlled at 800℃~1000℃ and the pressure at 50Torr~500Torr, and N source, Al source and In source were introduced.

[0044] In one embodiment, the method for preparing the N-polar three-dimensional AlGaN layer includes the following steps:

[0045] MOCVD growth was employed, with the reaction chamber temperature controlled at 800℃~1000℃ and the pressure at 50Torr~300Torr. N source, Ga source, and Al source were introduced to deposit an AlGaN layer. Then, NH3 was introduced to treat the AlGaN layer, forming an N-polar contact surface to obtain an N-polar AlGaN layer. The NH3 treatment temperature was 900℃~1100℃.

[0046] The present invention will be further illustrated below with specific embodiments.

[0047] Example 1

[0048] This embodiment provides a light-emitting diode epitaxial wafer, including a substrate and a composite buffer layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, and a P-type GaN layer sequentially deposited on the substrate. The composite buffer layer includes a graphene oxide layer, an AlON layer, an AlInN layer, and an N-polar three-dimensional AlGaN layer.

[0049] The thickness of the graphene oxide layer is 50 nm.

[0050] The O component in the AlON layer accounts for 0.1%, and the thickness is 40 nm.

[0051] The Al component in the AlInN layer accounts for 0.9%, and the thickness is 45 nm.

[0052] The Al composition in the N-polar three-dimensional AlGaN layer is 0.1%, and the thickness is 100 nm.

[0053] The above-mentioned method for fabricating an epitaxial wafer of a light-emitting diode includes the following steps:

[0054] S100 provides a substrate.

[0055] The S200 process sequentially grows a composite buffer layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, and a P-type GaN layer on the substrate. The composite buffer layer includes a graphene oxide layer, an AlON layer, an AlInN layer, and an N-polar three-dimensional AlGaN layer.

[0056] Specifically, the preparation method of the graphene oxide layer includes the following steps:

[0057] PECVD was used to grow graphene layers, with the reaction chamber temperature controlled at 900℃, pressure at 70 Torr, RF power at 18W, and reaction atmosphere of CH4 and H2 with a flow ratio of 1:10. After the graphene layer growth was completed, it was oxidized in an O2 atmosphere to form graphene oxide layer at a temperature of 900℃.

[0058] The method for preparing the AlON layer includes the following steps:

[0059] PVD growth was employed, with the reaction chamber temperature controlled at 600℃ and the pressure at 75 Torr. Ar was used as the protective gas, metallic Al was used as the sputtering target, and the reaction atmosphere consisted of O2 and N2 with a flow rate ratio of 1:10.

[0060] The method for preparing an AlInN layer includes the following steps:

[0061] MOCVD growth was employed, with the reaction chamber temperature controlled at 950℃ and the pressure at 200 Torr, and N, Al, and In sources introduced.

[0062] The method for preparing an N-polar three-dimensional AlGaN layer includes the following steps:

[0063] MOCVD growth was employed, with the reaction chamber temperature controlled at 865℃ and the pressure at 150 Torr. N, Ga, and Al sources were introduced to deposit an AlGaN layer. NH3 was then introduced to treat the AlGaN layer, forming an N-polar contact surface, thus obtaining an N-polar AlGaN layer. The NH3 treatment temperature was 1000℃.

[0064] Example 2

[0065] This embodiment provides a light-emitting diode epitaxial wafer, which differs from Embodiment 1 in that the proportion of O component in the AlON layer decreases from 0.1 to 0.01 along the epitaxial direction. Correspondingly, in the preparation method, the flow ratio of O2 to N2 decreases from 1:10 to 1:100. All other aspects are the same as in Embodiment 1.

[0066] Example 3

[0067] This embodiment provides a light-emitting diode epitaxial wafer, which differs from Embodiment 2 in that the proportion of Al component in the AlInN layer decreases from 0.9 to 0.7 along the epitaxial direction. All other aspects are the same as in Embodiment 2.

[0068] Comparative Example 1

[0069] This comparative example provides a light-emitting diode epitaxial wafer, which differs from Example 1 in that the composite buffer layer does not include a graphene oxide layer; correspondingly, the preparation method does not include the preparation step of the graphene oxide layer. All other aspects are the same as in Example 1.

[0070] Comparative Example 2

[0071] This comparative example provides a light-emitting diode epitaxial wafer, which differs from Example 1 in that the composite buffer layer does not include an AlON layer; correspondingly, the fabrication method does not include the AlON layer fabrication step. All other aspects are the same as in Example 1.

[0072] Comparative Example 3

[0073] This comparative example provides a light-emitting diode epitaxial wafer, which differs from Example 1 in that the composite buffer layer does not include an AlInN layer; correspondingly, the fabrication method does not include the step of fabricating the AlInN layer. All other aspects are the same as in Example 1.

[0074] Comparative Example 4

[0075] This comparative example provides a light-emitting diode epitaxial wafer, which differs from Example 1 in that the composite buffer layer does not include an N-polar three-dimensional AlGaN layer; correspondingly, the fabrication method does not include the step of fabricating an N-polar three-dimensional AlGaN layer. All other aspects are the same as in Example 1.

[0076] Performance testing:

[0077] The light-emitting diode epitaxial wafers obtained in Examples 1 to 3 and Comparative Examples 1 to 4 were made into 10mil×24mil LED chips, and the luminous brightness was tested at 120mA / 60mA current. The luminous efficacy improvement of Examples 1 to 3 and Comparative Examples 2 to 4 compared with Comparative Example 1 was calculated, and the results are shown in Table 1.

[0078] Table 1. Photoelectric performance test results of LED epitaxial wafers

[0079]

[0080] As can be seen from the table, the structure of the LED epitaxial wafer of the present invention can effectively improve the luminous brightness of the LED.

[0081] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A light-emitting diode epitaxial wafer, characterized in that, It includes a substrate and a composite buffer layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, and a P-type GaN layer sequentially deposited on the substrate; the composite buffer layer includes a graphene oxide layer, an AlON layer, an AlInN layer, and an N-polar three-dimensional AlGaN layer. The thickness of the graphene oxide layer is 1 nm to 100 nm; the proportion of O component in the AlON layer is 0.01 to 0.

5. The thickness of the AlON layer is 5nm~50nm.

2. The light-emitting diode epitaxial wafer as described in claim 1, characterized in that, In the AlON layer, the proportion of O component gradually decreases along the epitaxial direction.

3. The light-emitting diode epitaxial wafer as described in claim 2, characterized in that, The Al component in the AlInN layer accounts for 0.5~0.9%; The thickness of the AlInN layer is 1nm to 100nm.

4. The light-emitting diode epitaxial wafer as described in claim 3, characterized in that, In the AlInN layer, the proportion of Al component gradually decreases along the epitaxial direction.

5. The light-emitting diode epitaxial wafer as described in claim 1, characterized in that, The Al component in the N-polar three-dimensional AlGaN layer accounts for 0.01~0.5%; The thickness of the N-polar three-dimensional AlGaN layer is 50nm~500nm.

6. A method for preparing a light-emitting diode epitaxial wafer, used to prepare a light-emitting diode epitaxial wafer as described in any one of claims 1 to 5, characterized in that, Includes the following steps: A substrate is provided on which a composite buffer layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, and a P-type GaN layer are sequentially grown; the composite buffer layer includes a graphene oxide layer, an AlON layer, an AlInN layer, and an N-polar three-dimensional AlGaN layer.

7. The method for fabricating a light-emitting diode epitaxial wafer as described in claim 6, characterized in that, The deposition temperature of the graphene oxide layer is 800℃~1000℃, the deposition pressure is 50Torr~100Torr, and after deposition, O2 is introduced for oxidation treatment at a temperature of 800℃~1000℃. The deposition temperature of the AlON layer is 500℃~700℃, and the deposition pressure is 50Torr~300Torr; The deposition temperature of the AlInN layer is 800℃~1000℃, and the deposition pressure is 50Torr~500Torr; The deposition temperature of the N-polar three-dimensional AlGaN layer is 800℃~1000℃, the deposition pressure is 50Torr~300Torr, and after deposition, NH3 is introduced for treatment at a temperature of 800℃~1200℃.

8. A light-emitting diode, characterized in that, The light-emitting diode includes a light-emitting diode epitaxial wafer as described in any one of claims 1 to 5.

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