A blue light LED epitaxial wafer, epitaxial growth method and blue light LED chip

Abstract

The present invention provides a blue light LED epitaxial wafer, an epitaxial growth method and a blue light LED chip. The blue light LED epitaxial wafer includes a composite substrate, a pretreatment layer and a buffer layer. The pretreatment layer and the buffer layer are deposited on the composite substrate. The buffer layer has a structure in which a first buffer layer and a second buffer layer are grown in sequence. The composite substrate is a SiO2 pattern substrate. The pretreatment layer and the first buffer layer are both AlN layers. The second buffer layer is a GaN layer. The density of the pretreatment layer is better than that of the first buffer layer. Due to the introduction of the high-density pretreatment layer, SiO2 diffusion in the composite substrate can be effectively reduced. At the same time, the first buffer layer deposited on the pretreatment layer is used for stress release, thereby obtaining a better GaN epitaxial layer, reducing defect density, and improving the crystal quality of the epitaxial layer.

Description

Technical Field

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

[0002] LED chip is a semiconductor electronic component that can emit light. It has the advantages of small size, high brightness and low energy consumption. It is widely used in lighting and other fields. Among them, LED chip is obtained by splitting LED epitaxial wafer. LED epitaxial wafer includes substrate and GaN epitaxial layer grown on the substrate.

[0003] Currently, sapphire, silicon, or silicon carbide are commonly used as substrates. As the application field expands, the requirements for LED chips are also increasing. High-brightness chips are always the goal to be pursued. Therefore, improving the brightness of LED chips has become the most important technical point.

[0004] In recent years, with the continuous improvement of epitaxial technology and the continuous improvement of brightness requirements, composite substrates with greater brightness advantages have been developed to replace conventional sapphire substrates. The composite substrates are SiO2 patterned substrates, which are widely used because of their higher axial light output and brightness advantages within a fixed light collection angle. However, since it is relatively difficult to grow GaN epitaxy on SiO2, the epitaxial technology for composite substrates also has higher challenges. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide a blue light LED epitaxial wafer, an epitaxial growth method and a blue light LED chip, aiming to solve the problem of poor quality of GaN epitaxial crystals grown on SiO2 patterned substrates in the prior art.

[0006] According to an embodiment of the present invention, a blue light LED epitaxial wafer is characterized in that it includes a composite substrate, a pretreatment layer and a buffer layer arranged in a stacked manner, the buffer layer is a structure in which a first buffer layer and a second buffer layer are grown in sequence, the composite substrate is a SiO2 pattern substrate, the pretreatment layer and the first buffer layer are both AlN layers, and the second buffer layer is a GaN layer.

[0007] Preferably, the blue LED epitaxial wafer further comprises a three-dimensionally grown GaN layer, an undoped GaN layer, an n-type doped GaN layer, a stress release layer, a multi-quantum well layer, an electron blocking layer and a p-type doped GaN layer;

[0008] The pretreatment layer, the buffer layer, the three-dimensionally grown GaN layer, the undoped GaN layer, the n-type doped GaN layer, the stress release layer, the multi-quantum well layer, the electron blocking layer and the p-type doped GaN layer are epitaxially grown in sequence on the composite substrate.

[0009] Preferably, the thickness of the pretreatment layer is 10 nm to 30 nm, the thickness of the first buffer layer is 2 nm to 10 nm, and the thickness of the second buffer layer is 15 nm to 35 nm.

[0010] Preferably, the thickness of the three-dimensionally grown GaN layer is 500nm to 2000nm, the thickness of the undoped GaN layer is 800nm ​​to 1200nm, the thickness of the n-type doped GaN layer is 1000nm to 3000nm, the thickness of the stress release layer is 10nm to 50nm, the thickness of the multi-quantum well layer is 10nm to 14nm, the thickness of the electron blocking layer is 20nm to 60nm, and the thickness of the p-type doped GaN layer is 40nm to 200nm.

[0011] Preferably, the stress release layer and the multi-quantum well layer are both periodic structures in which InGaN layers and GaN layers are grown alternately, and the electron blocking layer is a periodic structure in which AlGaN layers and GaN layers are grown alternately.

[0012] According to an embodiment of the present invention, a method for epitaxial growth of a blue LED epitaxial wafer is used to prepare the above-mentioned blue LED epitaxial wafer. The epitaxial growth method includes:

[0013] Providing a composite substrate required for growth;

[0014] growing a pretreatment layer on the composite substrate;

[0015] When growing the buffer layer, growing the buffer layer on the pre-processed layer, the buffer layer includes a first buffer layer and a second buffer layer, and the first buffer layer and the second buffer layer are sequentially grown on the pre-processed layer;

[0016] Wherein, the pretreatment layer and the first buffer layer are both AlN layers, and the second buffer layer is a GaN layer.

[0017] Preferably, the epitaxial growth method further comprises:

[0018] The pretreatment layer, the buffer layer, the three-dimensionally grown GaN layer, the undoped GaN layer, the n-type doped GaN layer, the stress release layer, the multi-quantum well layer, the electron blocking layer and the p-type doped GaN layer are epitaxially grown in sequence on the composite substrate.

[0019] Preferably, the growth temperature of the pretreatment layer is 400° C. to 600° C., and the growth pressure is 0 torr to 5 torr.

[0020] Preferably, the growth temperature of the buffer layer is 800° C. to 850° C., and the growth pressure is 50 torr to 150 torr.

[0021] A blue LED chip according to an embodiment of the present invention includes the above-mentioned blue LED epitaxial wafer.

[0022] Compared with the existing technology: by introducing a pretreatment layer before the buffer layer, wherein the buffer layer is a structure composed of a first buffer layer and a second buffer layer grown in sequence, the composite substrate is a SiO2 pattern substrate, the pretreatment layer and the first buffer layer are both AlN layers, and the second buffer layer is a GaN layer. Specifically, the introduced pretreatment layer can effectively reduce the SiO2 diffusion in the composite substrate. At the same time, the first buffer layer deposited on the pretreatment layer is used for stress release, thereby obtaining a better GaN epitaxial layer, reducing the defect density, and improving the crystal quality of the epitaxial layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the structure of the blue LED epitaxial wafer in the first embodiment of the present invention;

[0024] Figure 2 This is a flow chart of the epitaxial growth method of a blue LED epitaxial wafer according to the second embodiment of the present invention;

[0025] Figure 3 This is a comparison chart of XRD test of the blue LED chip in Example 3 of the present invention;

[0026] Figure 4 This is a comparison chart of the brightness and yield of the blue LED chip in Example 3 of the present invention. DETAILED DESCRIPTION

[0027] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. The drawings illustrate several embodiments of the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present invention.

[0028] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0030] Example 1

[0031] See also Figure 1 , shown is a blue light LED epitaxial wafer in Example 1 of the present invention, including a composite substrate 1, and a pretreatment layer 2, a buffer layer 3, a three-dimensionally grown GaN layer 4, an undoped GaN layer 5, an n-type doped GaN layer 6, a stress release layer 7, a multi-quantum well layer 8, an electron blocking layer 9 and a p-type doped GaN layer 10 epitaxially grown in sequence on the composite substrate 1, wherein the buffer layer 3 includes a first buffer layer 31 and a second buffer layer 32, and the first buffer layer 31 and the second buffer layer 32 are deposited in sequence on the pretreatment layer 2.

[0032] In this embodiment, the composite substrate 1 is a SiO2 graphic substrate, the pretreatment layer 2 and the first buffer layer 31 are both AlN layers, but the AlN layer of the pretreatment layer 2 has better density than the AlN layer of the first buffer layer 31, and the second buffer layer 32 is a GaN layer, which paves the way for the subsequent three-dimensional growth of the GaN layer 4. It can be understood that since the growth process of the epitaxial wafer generally grows gradually from one side of the substrate to the other side, the growth density of the AlN layer can be controlled, and then a pretreatment layer 2 with good AlN layer density and a first buffer layer 31 with slightly poorer density can be prepared.

[0033] By way of example and not limitation, in some preferred embodiments of the present invention, the thickness of the pretreatment layer 2 is 10 nm to 30 nm, for example, 15 nm, 20 nm, 25 nm, etc.; the thickness of the first buffer layer 31 is 2 nm to 10 nm, for example, 7 nm, 8 nm, 9 nm, etc.; the thickness of the second buffer layer 32 is 15 nm to 35 nm, for example, 20 nm, 25 nm, 30 nm, etc.; the thickness of the three-dimensionally grown GaN layer 4 is 500 nm to 2000 nm, for example, 800 nm, 1000 nm, 1200 nm, etc.; the thickness of the undoped GaN layer 5 is 800 nm to 1200 nm, for example, 900 nm, 1000 nm, etc. m, 1100nm, etc.; the thickness of the n-type doped GaN layer 6 is 1000nm~3000nm, for example, 1500nm, 2000nm, 2500nm, etc.; the thickness of the stress release layer 7 is 10nm~50nm, for example, 20nm, 30nm, 40nm, etc.; the thickness of the multi-quantum well layer 8 is 10nm~14nm, for example, 11nm, 12nm, 13nm, etc.; the thickness of the electron blocking layer 9 is 20nm~60nm, for example, 30nm, 40nm, 50nm, etc.; the thickness of the p-type doped GaN layer 10 is 40nm~200nm, for example, 120nm, 140nm, 160nm, etc.

[0034] Specifically, the stress release layer 7 and the multi-quantum well layer 8 are both periodic structures in which InGaN layers and GaN layers grow alternately. Among them, the thickness of the InGaN layer in the multi-quantum well layer 8 structure is 2nm~4nm, and the thickness of the GaN layer is 8nm~10nm. In addition, the electron blocking layer 9 is a periodic structure in which AlGaN layers and GaN layers grow alternately.

[0035] Example 2

[0036] See also Figure 2 , shown is a method for epitaxial growth of a blue LED epitaxial wafer proposed in the second embodiment of the present invention, which is used to prepare the blue LED epitaxial wafer in the first embodiment above. The method specifically includes steps S201 to S209, wherein:

[0037] Step S201 : providing a composite substrate required for growth.

[0038] In this embodiment, the composite substrate is a SiO2 patterned substrate.

[0039] Step S202 : growing a pretreatment layer with a thickness of 10 nm to 30 nm.

[0040] Specifically, a pretreatment layer is deposited in the applied material PVD, which is an AlN layer. The growth temperature is 400℃~600℃ and the pressure is 0torr~5torr. Due to the sputtering growth, the density of AlN in the pretreatment layer is better, which can effectively reduce the diffusion of SiO2.

[0041] Step S203 , growing a first buffer layer with a thickness of 2 nm to 10 nm.

[0042] It should be noted that after the pretreatment layer is grown, the first buffer layer is deposited in MOCVD. The first buffer layer is an AlN layer. The growth temperature is 800℃~850℃ and the growth pressure is 50torr~150torr. Among them, the density of AlN in the first buffer layer grown by metal organic chemical vapor deposition is slightly poor, and it is mainly used for stress release.

[0043] In this embodiment, the thickness of the first buffer layer is 2 nm, and the growth temperature is 820°C.

[0044] By way of example but not limitation, in some preferred embodiments of this embodiment, the first buffer layer is an AlGaN layer or a mixed layer of AlN and AlGaN.

[0045] Step S204 , growing a second buffer layer with a thickness of 15 nm to 35 nm.

[0046] The second buffer layer is a GaN layer, the growth temperature is 800° C. to 850° C., and the growth pressure is 50 torr to 150 torr.

[0047] Step S205 , growing a three-dimensional GaN layer with a growth thickness of 500 nm to 2000 nm.

[0048] Step S206 , growing an undoped GaN layer with a thickness of 800 nm to 1200 nm.

[0049] Step S207 , growing an n-type doped GaN layer with a growth thickness of 1000 nm to 3000 nm.

[0050] Step S208 , growing a stress release layer with a thickness of 10 nm to 50 nm.

[0051] In this embodiment, InGaN layers and GaN layers are alternately grown on the n-type doped GaN layer to form a stress release layer.

[0052] Step S209 , growing a multi-quantum well layer with a thickness of 10 nm to 14 nm.

[0053] Specifically, InGaN layers and GaN layers are alternately grown on the stress release layer to form a multi-quantum well layer, wherein the thickness of the InGaN layer is 2nm to 4nm, and the thickness of the GaN layer is 8nm to 10nm.

[0054] Step S210 , growing an electron blocking layer with a thickness of 20 nm to 60 nm.

[0055] It should be noted that the AlGaN layer and the GaN layer are alternately grown on the multi-quantum well layer to form an electron blocking layer.

[0056] Step S211 , growing a p-type doped GaN layer with a growth thickness of 40 nm to 200 nm.

[0057] In summary, a pretreatment layer is introduced before the buffer layer, wherein the buffer layer is a structure composed of a first buffer layer and a second buffer layer grown in sequence, the composite substrate is a SiO2 graphic substrate, the pretreatment layer and the first buffer layer are both AlN layers, and the second buffer layer is a GaN layer. Specifically, the introduced pretreatment layer can effectively reduce the SiO2 diffusion in the composite substrate. At the same time, the first buffer layer deposited on the pretreatment layer is used for stress release, thereby obtaining a better GaN epitaxial layer, reducing the defect density, and improving the crystal quality of the epitaxial layer.

[0058] Example 3

[0059] A third embodiment of the present invention provides a blue LED chip, comprising the blue LED epitaxial wafer of the first embodiment. The blue LED epitaxial wafer can be epitaxially grown using the epitaxial growth method of the blue LED epitaxial wafer of the second embodiment.

[0060] See also Figure 3 and Figure 4 , Figure 3 This is a comparison chart of XRD tests of blue LED chips prepared from epitaxial wafers grown using the above-mentioned epitaxial growth method. Figure 4 This is a comparison chart of the brightness and yield of blue light LED chips. In this embodiment, the epitaxial wafer is a 4-inch epitaxial wafer, and the chip size is 24mil*37mil. As can be seen from the figure, the crystal quality of the epitaxial wafer of the blue light LED chip is significantly improved. Specifically, the XRD test 002 / 102 both show a significant decrease, and the chip yield and brightness are also significantly improved. Among them, the XRD test 002 / 102 data represent the dislocation density of two crystal directions respectively. The more dislocations, the more divergent the diffraction peak and the larger the output value. Therefore, the smaller the value, the lower the dislocation density and the better the crystal quality.

[0061] It should be noted that the half width of the 002 surface in the XRD test is reduced from 185.3 arc seconds in the existing technology to 125.4 arc seconds, and the half width of the 102 surface in the XRD test is reduced from 175.8 arc seconds in the existing technology to 151.6 arc seconds. The brightness of the 120mA current test is increased from 231.6mW in the existing technology to 235.4mW, and the comprehensive yield of the full test is improved from 89.6% in the existing technology to 92.7%.

[0062] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A blue LED epitaxial wafer, characterized in that: The invention comprises a composite substrate, a pretreatment layer and a buffer layer arranged in a stacked manner, wherein the buffer layer is a structure in which a first buffer layer and a second buffer layer are grown in sequence, the composite substrate is a SiO2 patterned substrate, the pretreatment layer and the first buffer layer are both AlN layers, the second buffer layer is a GaN layer, and the density of the pretreatment layer is better than that of the first buffer layer; The blue LED epitaxial wafer further includes a three-dimensionally grown GaN layer, an undoped GaN layer, an n-type doped GaN layer, a stress release layer, a multi-quantum well layer, an electron blocking layer, and a p-type doped GaN layer; The pretreatment layer, the buffer layer, the three-dimensionally grown GaN layer, the undoped GaN layer, the n-type doped GaN layer, the stress release layer, the multi-quantum well layer, the electron blocking layer and the p-type doped GaN layer are epitaxially grown in sequence on the composite substrate.

2. The blue LED epitaxial wafer according to claim 1, characterized in that: The thickness of the pretreatment layer is 10 nm to 30 nm, the thickness of the first buffer layer is 2 nm to 10 nm, and the thickness of the second buffer layer is 15 nm to 35 nm.

3. The blue LED epitaxial wafer according to claim 1, characterized in that: The thickness of the three-dimensionally grown GaN layer is 500nm to 2000nm, the thickness of the undoped GaN layer is 800nm ​​to 1200nm, the thickness of the n-type doped GaN layer is 1000nm to 3000nm, the thickness of the stress release layer is 10nm to 50nm, the thickness of the multi-quantum well layer is 10nm to 14nm, the thickness of the electron blocking layer is 20nm to 60nm, and the thickness of the p-type doped GaN layer is 40nm to 200nm.

4. The blue LED epitaxial wafer according to claim 1, characterized in that: The stress release layer and the multi-quantum well layer are both periodic structures in which InGaN layers and GaN layers grow alternately, and the electron blocking layer is a periodic structure in which AlGaN layers and GaN layers grow alternately.

5. A method for epitaxial growth of a blue LED epitaxial wafer, characterized in that: For preparing the blue LED epitaxial wafer according to any one of claims 1 to 4, the epitaxial growth method comprises: Providing a composite substrate required for growth; growing a pretreatment layer on the composite substrate; When growing the buffer layer, growing the buffer layer on the pre-processed layer, the buffer layer includes a first buffer layer and a second buffer layer, and the first buffer layer and the second buffer layer are sequentially grown on the pre-processed layer; Wherein, the pretreatment layer and the first buffer layer are both AlN layers, and the second buffer layer is a GaN layer.

6. The epitaxial growth method of a blue LED epitaxial wafer according to claim 5, characterized in that: The epitaxial growth method further comprises: The pretreatment layer, the buffer layer, the three-dimensionally grown GaN layer, the undoped GaN layer, the n-type doped GaN layer, the stress release layer, the multi-quantum well layer, the electron blocking layer and the p-type doped GaN layer are epitaxially grown in sequence on the composite substrate.

7. The epitaxial growth method of a blue LED epitaxial wafer according to claim 5, characterized in that: The growth temperature of the pretreatment layer is 400° C. to 600° C., and the growth pressure is 0 torr to 5 torr.

8. The method for epitaxial growth of a blue LED epitaxial wafer according to claim 5, wherein: The growth temperature of the buffer layer is 800° C. to 850° C., and the growth pressure is 50 torr to 150 torr.

9. A blue LED chip, characterized in that: The invention comprises the blue light LED epitaxial wafer according to any one of claims 1 to 4.

Images