CN109192827B - Gallium nitride-based light emitting diode epitaxial wafer and growth method thereof - Google Patents

Gallium nitride-based light emitting diode epitaxial wafer and growth method thereof Download PDF

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CN109192827B
CN109192827B CN201810847761.9A CN201810847761A CN109192827B CN 109192827 B CN109192827 B CN 109192827B CN 201810847761 A CN201810847761 A CN 201810847761A CN 109192827 B CN109192827 B CN 109192827B
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buffer layer
layer
oxygen
type semiconductor
substrate
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CN109192827A (en
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林智远
董彬忠
王江波
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HC Semitek Zhejiang Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/12—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a stress relaxation structure, e.g. buffer layer
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/005—Processes
    • H01L33/0062—Processes for devices with an active region comprising only III-V compounds
    • H01L33/0075—Processes for devices with an active region comprising only III-V compounds comprising nitride compounds
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/26—Materials of the light emitting region
    • H01L33/30—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table
    • H01L33/32—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen

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Abstract

The invention discloses a gallium nitride-based light emitting diode epitaxial wafer and a growth method thereof, belonging to the technical field of semiconductors. The GaN-based light emitting diode epitaxial wafer comprises a substrate, a buffer layer, an N-type semiconductor layer, an active layer and a P-type semiconductor layer, wherein the buffer layer, the N-type semiconductor layer, the active layer and the P-type semiconductor layer are sequentially stacked on the substrate, the buffer layer is made of aluminum nitride doped with oxygen, and the doping concentration of oxygen in the part, close to the substrate, of the buffer layer is greater than that of oxygen in the part, close to the N-type semiconductor layer, of the buffer layer. According to the invention, oxygen is doped into the material aluminum nitride of the buffer layer, and the doping concentration of the oxygen in the part of the buffer layer close to the substrate is greater than that of the oxygen in the part of the buffer layer close to the N-type semiconductor layer, so that the gradual transition from two different lattices of the sapphire to the gallium nitride-based material can be realized, and the lattice mismatch between the sapphire and the gallium nitride-based material can be effectively relieved.

Description

Gallium nitride-based light emitting diode epitaxial wafer and growth method thereof
Technical Field
The invention relates to the technical field of semiconductors, in particular to a gallium nitride-based light emitting diode epitaxial wafer and a growth method thereof.
Background
A Light Emitting Diode (LED) is a semiconductor electronic component capable of Emitting Light. Gallium nitride (GaN) -based materials are an important third-generation semiconductor material, and have a wide application prospect in the fields of semiconductor illumination, power electronics, high-frequency communication and the like. Since the nineties of the twentieth century, gallium nitride-based light emitting diodes were gradually commercialized, and the gap of the conventional light emitting diodes in the blue light band was filled.
The epitaxial wafer is a primary finished product in the manufacturing process of the light-emitting diode. The conventional gallium nitride-based LED epitaxial wafer comprises a substrate, an N-type semiconductor layer, an active layer and a P-type semiconductor layer, wherein the N-type semiconductor layer, the active layer and the P-type semiconductor layer are sequentially laminated on the substrate. The P-type semiconductor layer is used for providing holes for carrying out compound luminescence, the N-type semiconductor layer is used for providing electrons for carrying out compound luminescence, the active layer is used for carrying out radiation compound luminescence of the electrons and the holes, and the substrate is used for providing a growth surface for the epitaxial material.
The material of the substrate is generally selectedSapphire, the N-type semiconductor layer, the active layer and the P-type semiconductor layer are made of gallium nitride-based materials, and the lattice difference between the sapphire and the gallium nitride-based materials is large. In order to obtain better material quality and higher production efficiency, in the manufacturing process of the gallium nitride-based light emitting diode epitaxial wafer which is mainstream at present, a sapphire substrate (the main component is Al) is generally required2O3) The aluminum nitride buffer layer is grown in advance, and the aluminum nitride buffer layer is introduced to bring the effects of stress release, nucleation center supply and the like to the gallium nitride-based material, so that the transition of the lattice structure is realized. However, the aluminum nitride buffer layer adopted in the current mainstream technology is a single-layer structure with uniformly distributed components, and the potential of performance improvement of the gallium nitride-based light emitting diode caused by the aluminum nitride buffer layer cannot be fully exerted.
Disclosure of Invention
The embodiment of the invention provides a gallium nitride-based light emitting diode epitaxial wafer and a growth method thereof, which can solve the problem that the potential of the aluminum nitride buffer layer for improving the performance of the gallium nitride-based light emitting diode cannot be fully exerted in the prior art. The technical scheme is as follows:
in one aspect, an embodiment of the present invention provides a gallium nitride-based light emitting diode epitaxial wafer, where the gallium nitride-based light emitting diode epitaxial wafer includes a substrate, a buffer layer, an N-type semiconductor layer, an active layer, and a P-type semiconductor layer, where the buffer layer, the N-type semiconductor layer, the active layer, and the P-type semiconductor layer are sequentially stacked on the substrate, a material of the buffer layer is aluminum nitride doped with oxygen, and a doping concentration of oxygen in a portion of the buffer layer close to the substrate is greater than a doping concentration of oxygen in a portion of the buffer layer close to the N-type semiconductor layer.
Optionally, the buffer layer is a single-layer structure, and the doping concentration of oxygen in the single-layer structure is gradually reduced along the stacking direction of the gan-based led epitaxial wafer.
Optionally, the buffer layer is a stacked structure, and the doping concentration of oxygen in the stacked structure decreases layer by layer along the stacking direction of the gan-based led epitaxial wafer.
Preferably, the maximum value of the molar concentration of oxygen in the buffer layer is 3% to 20%, and the minimum value of the molar concentration of oxygen in the buffer layer is 0% to 8%.
Optionally, the buffer layer has a thickness of 5nm to 100 nm.
On the other hand, the embodiment of the invention provides a growth method of a gallium nitride-based light emitting diode epitaxial wafer, which comprises the following steps:
providing a substrate;
growing a buffer layer on the substrate;
growing an N-type semiconductor layer, an active layer and a P-type semiconductor layer on the buffer layer in sequence;
the buffer layer is made of aluminum nitride doped with oxygen, and the doping concentration of oxygen in the part of the buffer layer close to the substrate is greater than that of oxygen in the part of the buffer layer close to the N-type semiconductor layer.
Optionally, the growing a buffer layer on the substrate includes:
placing the substrate into a reaction chamber of a growth device;
and introducing nitrogen and oxygen into the reaction cavity, growing a buffer layer on the substrate, wherein the buffer layer is of a single-layer structure, the volume of the introduced nitrogen is unchanged during the growth of the single-layer structure, and the volume of the introduced oxygen is gradually reduced.
Optionally, the growing a buffer layer on the substrate includes:
placing the substrate into a reaction chamber of a growth device;
and introducing nitrogen and oxygen into the reaction cavity, growing a buffer layer on the substrate, wherein the buffer layer is of a laminated structure, the volume of the introduced nitrogen is unchanged during the growth of the laminated structure, and the volume of the introduced oxygen is reduced layer by layer.
Preferably, the maximum value of the flow rate of the oxygen gas when the buffer layer is grown is 2.5% to 10% of the flow rate of the nitrogen gas when the buffer layer is grown, and the minimum value of the flow rate of the oxygen gas when the buffer layer is grown is 0% to 5% of the flow rate of the nitrogen gas when the buffer layer is grown.
Preferably, the power of the growth device when growing the portion of the buffer layer close to the substrate is smaller than the power of the growth device when growing the portion of the buffer layer close to the N-type semiconductor layer.
The technical scheme provided by the embodiment of the invention has the following beneficial effects:
oxygen is doped into the aluminum nitride through the material of the buffer layer, and the doping concentration of the oxygen in the part of the buffer layer close to the substrate is greater than that of the oxygen in the part of the buffer layer close to the N-type semiconductor layer; the oxygen doping concentration of the buffer layer near the substrate is higher, and the main component is Al2O3The crystal lattice of the sapphire is matched; meanwhile, the doping concentration of oxygen in the part, close to the N-type semiconductor layer, of the buffer layer is small and is matched with the crystal lattice of the gallium nitride-based material. The buffer layer sets up between the substrate that adopts the sapphire and the N type semiconductor layer that adopts the gallium nitride base material, can realize the gradual transition from two kinds of different lattices of sapphire to gallium nitride base material, effectively alleviate the lattice mismatch between sapphire and the gallium nitride base material, fully release the stress that the lattice mismatch produced between sapphire and the gallium nitride base material, improve the defect that the lattice mismatch produced between sapphire and the gallium nitride base material, progressively reduce dislocation density, the crystallinity becomes good, promote the crystal quality of epitaxial wafer by a wide margin, reduce the polarization of active layer, promote LED's internal quantum efficiency, luminance and light efficiency, reduce LED's reverse electric leakage simultaneously, strengthen LED's antistatic performance.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a gan-based led epitaxial wafer according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of a buffer layer according to an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of another buffer layer provided in an embodiment of the present invention;
fig. 4 is a flowchart of a method for growing an epitaxial wafer of a gallium nitride-based light emitting diode according to an embodiment of the present invention;
FIG. 5 is a schematic diagram illustrating a variation of the volume of oxygen introduced during the growth of a buffer layer according to an embodiment of the present invention;
fig. 6 is a schematic diagram illustrating another variation of the volume of oxygen introduced during the growth of the buffer layer according to the embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
Fig. 1 is a schematic structural diagram of a gallium nitride-based light emitting diode epitaxial wafer according to an embodiment of the present invention, and referring to fig. 1, the gallium nitride-based light emitting diode epitaxial wafer includes a substrate 10, a buffer layer 20, an N-type semiconductor layer 30, an active layer 40, and a P-type semiconductor layer 50, and the buffer layer 20, the N-type semiconductor layer 30, the active layer 40, and the P-type semiconductor layer 50 are sequentially stacked on the substrate 10.
In this embodiment, the buffer layer 20 is made of aluminum nitride doped with oxygen, and the doping concentration of oxygen in the portion of the buffer layer 20 close to the substrate 10 is greater than that in the portion of the buffer layer 20 close to the N-type semiconductor layer 30.
Since the doping concentration of oxygen is greater in the portion of the buffer layer 20 near the substrate 10 than in the portion of the buffer layer 20 near the N-type semiconductor layer 30, the lattice constant of the portion of the buffer layer 20 near the substrate 10 is smaller than that of the portion of the buffer layer 20 near the N-type semiconductor layer 30, while the dislocation density of the portion of the buffer layer 20 near the substrate 10 is higher than that of the portion of the buffer layer 20 near the N-type semiconductor layer 30.
In the embodiment of the invention, oxygen is doped into the aluminum nitride serving as the material of the buffer layer, and the doping concentration of the oxygen in the part of the buffer layer close to the substrate is highThe doping concentration of oxygen in the buffer layer is close to the N-type semiconductor layer; the oxygen doping concentration of the buffer layer near the substrate is higher, and the main component is Al2O3The crystal lattice of the sapphire is matched; meanwhile, the doping concentration of oxygen in the part, close to the N-type semiconductor layer, of the buffer layer is small and is matched with the crystal lattice of the gallium nitride-based material. The buffer layer sets up between the substrate that adopts the sapphire and the N type semiconductor layer that adopts the gallium nitride base material, can realize the gradual transition from two kinds of different lattices of sapphire to gallium nitride base material, effectively alleviate the lattice mismatch between sapphire and the gallium nitride base material, fully release the stress that the lattice mismatch produced between sapphire and the gallium nitride base material, improve the defect that the lattice mismatch produced between sapphire and the gallium nitride base material, progressively reduce dislocation density, the crystallinity becomes good, promote the crystal quality of epitaxial wafer by a wide margin, reduce the polarization of active layer, promote LED's internal quantum efficiency, luminance and light efficiency, reduce LED's reverse electric leakage simultaneously, strengthen LED's antistatic performance.
In a specific implementation, the doping concentration of oxygen in the portion of the buffer layer 20 close to the substrate 10 is greater than 0, and the doping concentration of oxygen in the portion of the buffer layer 20 close to the N-type semiconductor layer 30 may be greater than 0 and may also be equal to 0.
Alternatively, the thickness of the buffer layer 20 may be 5nm to 100nm, preferably 50 nm.
If the thickness of the buffer layer is less than 5nm, the lattice mismatch between the sapphire and the gallium nitride-based material may not be effectively alleviated due to the too small thickness of the buffer layer; if the thickness of the buffer layer is greater than 100nm, waste may be caused due to too large thickness of the buffer layer, increasing the production cost.
Alternatively, the molar concentration of oxygen in each portion of buffer layer 20 may be 0% to 25%.
If the molar concentration of oxygen in each part of the buffer layer is more than 25%, the lattice matching between the buffer layer and the gallium nitride-based material is poor probably due to the overhigh molar concentration of oxygen in the buffer layer, the crystal quality of an epitaxial wafer is affected, and the internal quantum efficiency, the brightness and the light efficiency of the LED cannot be effectively improved.
Fig. 2 is a schematic structural diagram of a buffer layer according to an embodiment of the present invention, where circles in fig. 2 schematically represent oxygen doped in the buffer layer, and a larger number of circles in a certain region indicates a higher oxygen doping concentration in the region. Referring to fig. 2, in one implementation manner of the present embodiment, the buffer layer 20 may have a single-layer structure, and the doping concentration of oxygen in the single-layer structure is gradually decreased along the stacking direction of the gan-based led epitaxial wafer.
In the above implementation, the buffer layer 20 does not have a boundary of the sub-layers, and the sub-layers cannot be divided; the doping concentration of oxygen in the whole structure is changed continuously, and the doping concentration is reduced gradually along the laminating direction of the epitaxial wafer of the gallium nitride-based light-emitting diode.
By adopting the implementation mode, the doping concentration of oxygen is gradually changed, the lattice constant of the buffer layer is correspondingly and gradually changed, the transition is smooth, the crystal quality of the epitaxial wafer can be improved to the maximum extent, and the internal quantum efficiency, the brightness and the light efficiency of the LED are improved.
Preferably, the doping concentration of oxygen in the single-layer structure may be linearly decreased along the stacking direction of the gan-based led epitaxial wafer. In practical application, the doping concentration of oxygen in the single-layer structure can also be reduced in a nonlinear way along the lamination direction of the gallium nitride-based light-emitting diode epitaxial wafer.
Alternatively, the molar concentration of oxygen in the buffer layer 20 may be 3% to 20%, preferably 12%.
If the maximum value of the molar concentration of oxygen in the buffer layer is less than 3%, the molar concentration of oxygen in the buffer layer is too low due to the fact that the maximum value of the molar concentration of oxygen in the buffer layer is too small, and lattice mismatch between sapphire and the gallium nitride-based material cannot be effectively relieved; if the maximum value of the molar concentration of oxygen in the buffer layer is greater than 20%, the molar concentration of oxygen in the buffer layer is too high due to the fact that the maximum value of the molar concentration of oxygen in the buffer layer is too large, the lattice matching between the buffer layer and the gallium nitride-based material is poor, the crystal quality of an epitaxial wafer is affected, and the internal quantum efficiency, the brightness and the light efficiency of the LED cannot be effectively improved.
Alternatively, the minimum value of the molar concentration of oxygen in the buffer layer 20 may be 0% to 8%, preferably 4%.
If the minimum value of the molar concentration of oxygen in the buffer layer is greater than 8%, the molar concentration of oxygen in the buffer layer is too high due to too large minimum value of the molar concentration of oxygen in the buffer layer, the lattice matching between the buffer layer and the gallium nitride-based material is poor, the crystal quality of an epitaxial wafer is affected, and the internal quantum efficiency, the brightness and the light efficiency of the LED cannot be effectively improved.
For example, the molar concentration of oxygen in the buffer layer 20 gradually decreases from 20% to 0%.
Fig. 3 is a schematic structural diagram of another buffer layer provided in an embodiment of the present invention, where fig. 3 also schematically shows doped oxygen in the buffer layer by circles, and a larger number of circles in a certain region indicates a higher doping concentration of oxygen in this region. Referring to fig. 3, in another implementation manner of the present embodiment, the buffer layer 20 may have a stacked structure, and the doping concentration of oxygen in the stacked structure decreases layer by layer along the stacking direction of the gan-based led epitaxial wafer.
In the above implementation, the buffer layer 20 includes a plurality of sub-layers that may be divided into sequential stacks; the doping concentration of oxygen in the single sub-layer is kept unchanged, and the doping concentration of oxygen in all the sub-layers is reduced layer by layer along the lamination direction of the GaN-based light emitting diode epitaxial wafer.
By adopting the implementation mode, the implementation process is simpler, and the stability of the product is better.
Alternatively, the doping concentrations of oxygen in the respective sublayers in the stacked structure may be in an arithmetic progression. In practical applications, the doping concentration of oxygen in each sub-layer in the stack structure may also be non-uniformly reduced.
Specifically, the tolerance of the arithmetic progression may be 1% to 5%, such as 3%.
Alternatively, the maximum value of the molar concentration of oxygen in the buffer layer 20 may be 3% to 20%.
If the maximum value of the molar concentration of oxygen in the buffer layer is less than 3%, the molar concentration of oxygen in the buffer layer is too low due to the fact that the maximum value of the molar concentration of oxygen in the buffer layer is too small, and lattice mismatch between sapphire and the gallium nitride-based material cannot be effectively relieved; if the maximum value of the molar concentration of oxygen in the buffer layer is greater than 20%, the molar concentration of oxygen in the buffer layer is too high due to the fact that the maximum value of the molar concentration of oxygen in the buffer layer is too large, the lattice matching between the buffer layer and the gallium nitride-based material is poor, the crystal quality of an epitaxial wafer is affected, and the internal quantum efficiency, the brightness and the light efficiency of the LED cannot be effectively improved.
Alternatively, the minimum value of the molar concentration of oxygen in the buffer layer 20 may be 0% to 8%.
If the minimum value of the molar concentration of oxygen in the buffer layer is greater than 8%, the molar concentration of oxygen in the buffer layer is too high due to too large minimum value of the molar concentration of oxygen in the buffer layer, the lattice matching between the buffer layer and the gallium nitride-based material is poor, the crystal quality of an epitaxial wafer is affected, and the internal quantum efficiency, the brightness and the light efficiency of the LED cannot be effectively improved.
Alternatively, the number of sublayers in the stack may be 2 to 10, such as 6.
If the number of sublayers in the stacked structure is more than 10, it may be difficult to precisely control the growth effect of each sublayer and its interface due to the too large number of sublayers in the stacked structure, and the production cost may also be increased.
Alternatively, the thickness of the individual sublayers in the stacked structure may be 3nm to 10nm, such as 6 nm.
If the thickness of each sublayer in the stacked structure is less than 3nm, the lattice mismatch between the sapphire and the gallium nitride-based material may not be effectively alleviated due to the too small thickness of each sublayer in the stacked structure; if the thickness of each sub-layer in the stacked structure is greater than 10nm, material may be wasted due to too large thickness of each sub-layer in the stacked structure, increasing production costs.
For example, the buffer layer 20 includes a sub-layer 21, a sub-layer 22, and a sub-layer 23 stacked in this order, and the molar concentration of oxygen in the sub-layer 21 is 20%, the molar concentration of oxygen in the sub-layer 22 is 10%, and the molar concentration of oxygen in the sub-layer 23 is 0%.
Specifically, sapphire may be used as the material of the substrate 10. In practical applications, the material of the substrate 10 may also be any one of silicon carbide, silicon, gallium nitride, zinc oxide, gallium arsenide, gallium phosphide, magnesium oxide, and copper. The surface of the Substrate 10 may be a plane, or may be a curved surface with a certain pattern formed by a process, such as a Patterned Sapphire Substrate (PSS). For example, the substrate 10 is PSS, the pattern on the PSS is a plurality of cones arranged in an array, the diameter of the cone is 2.8 μm, the height of the cone is 1.8 μm, and the interval between the cones is 3 μm.
The material of the N-type semiconductor layer 30 may be N-type doped gallium nitride. The active layer 40 may include a plurality of quantum wells and a plurality of quantum barriers, which are alternately stacked; the quantum well may be indium gallium nitride (InGaN), and the quantum barrier may be gallium nitride (gan). The P-type semiconductor layer 50 may be made of P-type doped gallium nitride.
Further, the thickness of the N-type semiconductor layer 30 may be 1 μm to 3 μm, preferably 1.5 μm; the doping concentration of the N-type dopant in the N-type semiconductor layer 30 may be 1018cm-3～3*1019cm-3Preferably 6 x 1018cm-3. The thickness of the quantum well can be 3nm to 4nm, and is preferably 3.5 nm; the thickness of the quantum barrier can be 9 nm-15 nm, preferably 12 nm; the number of quantum wells is the same as the number of quantum barriers, and the number of quantum barriers may be 5 to 11, preferably 8. The thickness of the P-type semiconductor layer 50 may be 100nm to 300nm, preferably 200 nm; the doping concentration of the P-type dopant in the P-type semiconductor layer 50 may be 1018/cm3～1020/cm3Preferably 1019/cm3。
Optionally, as shown in fig. 1, the gan-based led epitaxial wafer may further include a high temperature buffer layer 71, and the high temperature buffer layer 71 is disposed between the buffer layer 20 and the N-type semiconductor layer 30 to alleviate lattice mismatch between the substrate and the N-type semiconductor layer.
In a specific implementation, the buffer layer is a thin layer of gallium nitride that is first grown on the substrate at a low temperature, and is therefore also referred to as a low temperature buffer layer. Then, the longitudinal growth of gallium nitride is carried out on the low-temperature buffer layer, and a plurality of mutually independent three-dimensional island-shaped structures called three-dimensional nucleation layers can be formed; then, transverse growth of gallium nitride is carried out on all the three-dimensional island structures and among the three-dimensional island structures to form a two-dimensional plane structure which is called a two-dimensional recovery layer; and finally, growing a thicker gallium nitride layer called an intrinsic gallium nitride layer on the two-dimensional growth layer at a high temperature. The three-dimensional nucleation layer, the two-dimensional recovery layer, and the intrinsic gallium nitride layer are collectively referred to as a high-temperature buffer layer in this embodiment.
Further, the thickness of the three-dimensional nucleation layer may be 400nm to 600nm, preferably 500 nm. The thickness of the two-dimensional recovery layer may be 500nm to 800nm, preferably 650 nm. The thickness of the intrinsic gallium nitride layer may be in the range 1 μm to 2 μm, such as 1.5 μm.
Optionally, as shown in fig. 1, the gan-based LED epitaxial wafer may further include a stress release layer 72, where the stress release layer 72 is disposed between the N-type semiconductor layer 30 and the active layer 40 to release stress generated by lattice mismatch between sapphire and gan, so as to improve crystal quality of the active layer, facilitate radiation recombination of electrons and holes in the active layer for light emission, improve internal quantum efficiency of the LED, and further improve light emission efficiency of the LED.
Specifically, the stress relieving layer 72 may include a plurality of indium gallium nitride layers and a plurality of gallium nitride layers, which are alternately stacked.
Further, the thickness of the indium gallium nitride layer in the stress release layer 72 may be 1nm to 3nm, preferably 2 nm; the thickness of the gallium nitride layer can be 20 nm-40 nm, preferably 30 nm; the number of the indium gallium nitride layers is the same as that of the gallium nitride layers, and the number of the gallium nitride layers may be 3 to 9, preferably 6.
Optionally, as shown in fig. 1, the gan-based LED epitaxial wafer may further include an electron blocking layer 73, where the electron blocking layer 73 is disposed between the active layer 40 and the P-type semiconductor layer 50to prevent electrons from jumping into the P-type semiconductor layer to combine with holes in a non-radiative manner, thereby reducing the light emitting efficiency of the LED.
Specifically, the electron blocking layer 73 may be made of P-type doped aluminum gallium nitride (AlGaN),such as AlyGa1-yN，0.1＜y＜0.5。
Further, the thickness of the electron blocking layer 73 may be 50nm to 100nm, preferably 75 nm.
Preferably, as shown in fig. 1, the gan-based led epitaxial wafer may further include a low temperature P-type layer 74, where the low temperature P-type layer 74 is disposed between the active layer 40 and the electron blocking layer 73, so as to avoid indium atoms in the active layer from being precipitated due to the high growth temperature of the electron blocking layer, which affects the light emitting efficiency of the led.
In one implementation of this embodiment, the low temperature P-type layer 74 may be substantially the same as the P-type semiconductor layer 50 except that the growth temperature of the low temperature P-type layer 74 is lower than the growth temperature of the P-type semiconductor layer 50.
In another implementation of the present embodiment, the material of the low temperature P-type layer 74 may be P-type doped gallium nitride.
Further, the thickness of the low-temperature P-type layer 74 may be 30nm to 50nm, preferably 40 nm; the P-type dopant doping concentration in the low temperature P-type layer 74 may be 1020/cm3～1021/cm3Preferably 5 x 1020/cm3。
Optionally, as shown in fig. 1, the light emitting diode epitaxial wafer may further include a P-type contact layer 75, and the P-type contact layer 75 is laid on the P-type semiconductor layer 50to form an ohmic contact with an electrode or a transparent conductive film formed in a chip manufacturing process.
Specifically, the P-type contact layer 75 may be made of P-type doped indium gallium nitride.
Further, the thickness of the P-type contact layer 75 may be 5nm to 100nm, preferably 50 nm; the doping concentration of the P-type dopant in the P-type contact layer 75 may be 1021/cm3～1022/cm3Preferably 6 x 1021/cm3。
The embodiment of the invention provides a growth method of a gallium nitride-based light-emitting diode epitaxial wafer, which is suitable for growing the gallium nitride-based light-emitting diode epitaxial wafer shown in figure 1. Fig. 4 is a flowchart of a growth method of a gan-based led epitaxial wafer according to an embodiment of the present invention, and referring to fig. 4, the growth method includes:
step 201: a substrate is provided.
Optionally, the growing method may further include:
the substrate is pretreated.
Specifically, the pretreatment method may include chemical cleaning, high-temperature baking, and the like to remove impurities on the surface of the substrate and improve the state of the surface of the substrate. For example, the substrate is pretreated by nitrogen purging and high-temperature baking. Wherein, the high-temperature baking temperature can be 550 ℃.
Preferably, the pre-treatment of the substrate may comprise
Step 202: a buffer layer is grown on a substrate.
In this embodiment, the buffer layer is made of aluminum nitride doped with oxygen, and the doping concentration of oxygen in a portion of the buffer layer close to the substrate is higher than that in a portion of the buffer layer close to the N-type semiconductor layer.
In an implementation manner of this embodiment, the step 202 may include:
putting the substrate into a reaction cavity of growth equipment;
and introducing nitrogen and oxygen into the reaction cavity, growing a buffer layer on the substrate, wherein the buffer layer is of a single-layer structure, the volume of the introduced nitrogen is unchanged when the single-layer structure grows, and the volume of the introduced oxygen is gradually reduced.
Fig. 5 is a schematic diagram of a variation of the volume of the introduced oxygen gas during the growth of the buffer layer according to an embodiment of the present invention, and referring to fig. 5, in the above implementation, during the growth of the buffer layer, the volume of the introduced nitrogen gas is kept unchanged, and the volume of the introduced oxygen gas is gradually reduced, so that the doping concentration of the oxygen in the grown buffer layer is correspondingly reduced, that is, the doping concentration of the oxygen in the single-layer structure is gradually reduced along the stacking direction of the gan-based led epitaxial wafer.
Alternatively, the maximum value of the flow rate of oxygen when growing the buffer layer may be 2.5% to 10% of the flow rate of nitrogen when growing the buffer layer to match the maximum value of the molar concentration of oxygen in the buffer layer.
Alternatively, the minimum value of the flow rate of oxygen when growing the buffer layer may be 0% to 5% of the flow rate of nitrogen when growing the buffer layer to match the minimum value of the molar concentration of oxygen in the buffer layer.
Alternatively, the power of the growth apparatus when growing the portion of the buffer layer near the substrate may be smaller than the power of the growth apparatus when growing the portion of the buffer layer near the N-type semiconductor layer. When the buffer layer grows in the area close to the substrate, the power of the growth equipment is lower, the arc discharge can be reduced, the generation of particles is reduced, and the pollution to the substrate is avoided; meanwhile, when the buffer layer grows in the region far away from the substrate, the power of the growing equipment is high, the crystallization quality can be improved, a good starting point is provided for the growth of gallium nitride, the growth speed of the buffer layer is improved, and the productivity is improved.
In another implementation manner of this embodiment, this step 202 may include:
putting the substrate into a reaction cavity of growth equipment;
and introducing nitrogen and oxygen into the reaction cavity, growing a buffer layer on the substrate, wherein the buffer layer is of a laminated structure, the volume of the introduced nitrogen is unchanged when the laminated structure is grown, and the volume of the introduced oxygen is reduced layer by layer.
Fig. 6 is a schematic view of another variation of the volume of the introduced oxygen during the growth of the buffer layer according to the embodiment of the present invention, and referring to fig. 6, in the above implementation, during the growth of the buffer layer, the volume of the introduced nitrogen is kept unchanged, and simultaneously the volume of the introduced oxygen is reduced after each sub-layer is grown, and the doping concentration of oxygen in each sub-layer is correspondingly reduced, that is, the doping concentration of oxygen in the stacked structure is reduced layer by layer along the stacking direction of the gan-based led epitaxial wafer.
During concrete implementation, the volume of the introduced nitrogen is unchanged during the growth of the laminated structure, the volume of the introduced oxygen is reduced layer by layer, the buffer layer can grow in one reaction cavity, the volume of the introduced oxygen is adjusted to be realized simultaneously, the buffer layers can also grow in a plurality of reaction cavities in sequence, and the volume of the introduced oxygen in each reaction cavity is realized in different manners. When the buffer layers are grown in the reaction chambers with different volumes of the introduced oxygen in sequence, the volumes of the introduced oxygen in the reaction chambers can be kept unchanged, the state of the obtained sub-layer is stable, and the performance fluctuation of the LED finally manufactured by the epitaxial wafer grown on the buffer layers with different heats is small.
Alternatively, the maximum value of the flow rate of oxygen when growing the buffer layer may be 2.5% to 10% of the flow rate of nitrogen when growing the buffer layer to match the maximum value of the molar concentration of oxygen in the buffer layer.
Alternatively, the minimum value of the flow rate of oxygen when growing the buffer layer may be 0% to 5% of the flow rate of nitrogen when growing the buffer layer to match the minimum value of the molar concentration of oxygen in the buffer layer.
Alternatively, the power of the growth apparatus when growing the portion of the buffer layer near the substrate may be smaller than the power of the growth apparatus when growing the portion of the buffer layer near the N-type semiconductor layer.
In practical applications, the buffer layer may be grown by Physical Vapor Deposition (PVD), or by Metal-organic Chemical Vapor Deposition (MOCVD).
Specifically, when the PVD technique is used for growing the buffer layer, the diameter of the reaction chamber may be 50 cm-60 cm, the height of the reaction chamber may be 70 cm-80 cm, the sputtering voltage may be 10V-10 kV, and the pressure inside the reaction chamber may be 3 × 10-5Torr to 1 Torr; the reaction gas adopts argon and nitrogen, and the flow rate of the argon introduced into the reaction cavity per unit volume is 1 multiplied by 100sccm/m3～5×103sccm/m3The flow rate of the introduced nitrogen gas is 5X 100sccm/m3～2×104sccm/m3The flow rate of the introduced oxygen is 0sccm/m3～2×103sccm/m3。
For example, when the buffer layer is a single-layer structure, the substrate is first placed in the reaction chamber; argon was then bubbled into the reaction chamber and dc power P1 was applied. Then controlling the temperature in the reaction cavity to be T (such as 500 ℃), and controlling the pressure in the reaction cavity to be Q (such as 3 mTorr-7 mTorr); argon gas with the flow rate of a (such as 30 sccm-60 sccm) and nitrogen gas with the flow rate of b (such as 100 sccm-200 sccm) are introduced into the reaction cavity. Then, oxygen gas with the flow rate of c1 (such as 2 sccm-6 sccm) is introduced into the reaction chamber, and direct current power P2 (such as 3000W-5000W) is applied, so that aluminum nitride with higher oxygen doping concentration is grown in the region of the buffer layer close to the substrate. After a certain time (such as 5 s-8 s), the flow rate of the oxygen introduced into the reaction cavity and the applied direct current power are gradually changed. And finally, introducing oxygen with the flow rate of c2 (such as 0sccm) into the reaction chamber, applying direct current power P3 (such as 4500W-6500W), and growing aluminum nitride with low oxygen doping concentration in the region of the buffer layer close to the N-type semiconductor layer. Wherein, P3 is more than P2 is more than or equal to (5 multiplied by P1), (c2/b) < (c 1/b). The duration of the whole process can be 20 s-30 s, and the thickness of the formed gallium nitride layer can be 10 nm-30 nm.
For another example, when the buffer layer is a laminated structure, the substrate is first placed in the reaction chamber; argon was then bubbled into the reaction chamber and dc power P1 was applied. Then controlling the temperature in the reaction chamber to be T1 (such as 450 ℃), and controlling the pressure in the reaction chamber to be Q1 (such as 3 mTorr-7 mTorr); argon gas with the flow rate of a1 (such as 30 sccm-60 sccm), nitrogen gas with the flow rate of b1 (such as 100 sccm-200 sccm) and oxygen gas with the flow rate of c1 (such as 2 sccm-6 sccm) are introduced into the reaction cavity, and direct current power P2 (such as 3000W-5000W) is applied, so that aluminum nitride (such as 5 nm-15 nm in thickness) with high doping concentration of oxygen is grown in the region of the buffer layer close to the substrate. And then gradually changing the flow of the gas introduced into the reaction cavity and the applied direct current power. Finally, the temperature in the reaction cavity is controlled to be T2 (such as 500 ℃), and the pressure in the reaction cavity is Q2 (such as 3 mTorr-7 mTorr); argon gas with a flow rate of a2 (such as a 2-a 1), nitrogen gas with a flow rate of b2 (such as b 2-b 1) and oxygen gas with a flow rate of c2 (such as c 2-c 1/2) are introduced into the reaction chamber, and direct current power P3 (such as 4500W-6500W) is applied, so that aluminum nitride (such as 5 nm-10 nm in thickness) with low oxygen doping concentration is grown in a region of the buffer layer close to the N-type semiconductor layer. Wherein, P3 is more than P2 is more than or equal to (5 multiplied by P1), (c2/b2) < (c1/b 1).
Step 203: and sequentially growing an N-type semiconductor layer, an active layer and a P-type semiconductor layer on the buffer layer.
In practical applications, the N-type semiconductor layer, the active layer and the P-type semiconductor layer may be grown by using the MOCVD technique.
Specifically, the step 203 may include:
a first step of growing an N-type semiconductor layer on the buffer layer at a temperature of 1000 to 1100 ℃ (preferably 1050 ℃) and a pressure of 100to 500torr (preferably 300 torr);
secondly, growing an active layer on the N-type semiconductor layer; wherein the growth temperature of the quantum well is 720 ℃ to 800 ℃ (preferably 760 ℃), and the pressure is 100torr to 500torr (preferably 300 torr); the growth temperature of the quantum barrier is 900 ℃ -950 ℃ (preferably 925 ℃), and the pressure is 100 torr-500 torr (preferably 300 torr);
and thirdly, controlling the temperature to be 850-950 ℃ (preferably 900 ℃) and the pressure to be 100-300 torr (preferably 200torr), and growing the P-type semiconductor layer on the active layer.
Optionally, before the first step, the manufacturing method may further include:
and growing a high-temperature buffer layer on the buffer layer.
Accordingly, an N-type semiconductor layer is grown on the high temperature buffer layer.
Specifically, growing a high temperature buffer layer on the buffer layer may include:
controlling the temperature to be 1000-1040 ℃ (preferably 1020 ℃), and the pressure to be 400-600 torr (preferably 500torr), and growing a three-dimensional nucleation layer on the buffer layer;
controlling the temperature to be 1040-1080 ℃ (preferably 1060 ℃) and the pressure to be 400-600 torr (preferably 500torr), and growing a two-dimensional recovery layer on the three-dimensional nucleation;
the intrinsic gallium nitride layer is grown on the two-dimensional restoration layer under a temperature of 1050 ℃ to 1100 ℃ (preferably 1050 ℃) and a pressure of 100torr to 500torr (preferably 300 torr).
Optionally, before the second step, the manufacturing method may further include:
and growing a stress release layer on the N-type semiconductor layer.
Accordingly, an active layer is grown on the stress relieving layer.
Specifically, growing the stress relief layer on the N-type semiconductor layer may include:
the temperature is controlled to be 800 ℃ to 1100 ℃ (preferably 950 ℃) and the pressure is controlled to be 100torr to 500torr (preferably 300torr), and the stress release layer is grown on the N-type semiconductor layer.
Optionally, before the third step, the manufacturing method may further include:
an electron blocking layer is grown on the active layer.
Accordingly, a P-type semiconductor layer is grown on the electron blocking layer.
Specifically, growing an electron blocking layer on the active layer may include:
the electron blocking layer is grown on the active layer at a temperature of 900 to 1000 deg.C (preferably 950 deg.C) and a pressure of 200to 500torr (preferably 350 torr).
Preferably, before growing the electron blocking layer on the active layer, the manufacturing method may further include:
a low temperature P-type layer is grown on the active layer.
Accordingly, an electron blocking layer is grown on the low temperature P-type layer.
Specifically, growing the low temperature P-type layer on the active layer may include:
the temperature is controlled to be 750 ℃ to 850 ℃ (preferably 800 ℃) and the pressure is controlled to be 100torr to 500torr (preferably 300torr), and the low-temperature P type layer is grown on the active layer.
Optionally, after the third step, the manufacturing method may further include:
and growing a P-type contact layer on the P-type semiconductor layer.
Specifically, growing the P-type contact layer on the P-type semiconductor layer may include:
the P-type contact layer is grown on the P-type semiconductor layer at a temperature of 850 to 1000 deg.C (preferably 925 deg.C) and a pressure of 100to 300torr (preferably 200 torr).
After the completion of the epitaxial growth, the temperature is lowered to 650 to 850 ℃ (preferably 750 ℃), the epitaxial wafer is annealed in a nitrogen atmosphere for 5 to 15 minutes (preferably 10 minutes), and then the temperature of the epitaxial wafer is lowered to room temperature.
The control of the temperature and the pressure both refer to the control of the temperature and the pressure in a reaction chamber for growing the epitaxial wafer, and specifically refer to the reaction chamber of a Metal-organic Chemical Vapor Deposition (MOCVD) device. During implementation, trimethyl gallium or triethyl gallium is used as a gallium source, high-purity ammonia gas is used as a nitrogen source, trimethyl indium is used as an indium source, trimethyl aluminum is used as an aluminum source, silane is used as an N-type dopant, and magnesium diclocide is used as a P-type dopant.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (5)

1. A gallium nitride-based light emitting diode epitaxial wafer comprises a substrate, a buffer layer, an N-type semiconductor layer, an active layer and a P-type semiconductor layer, wherein the buffer layer, the N-type semiconductor layer, the active layer and the P-type semiconductor layer are sequentially laminated on the substrate; the power of the growth equipment when the part of the buffer layer close to the substrate is grown is smaller than that when the part of the buffer layer close to the N-type semiconductor layer is grown; the buffer layer grows in a plurality of reaction cavities in sequence, and the volumes of oxygen introduced into the reaction cavities are different; when the buffer layer grows, firstly introducing argon into the reaction cavity and applying direct current power, then controlling the temperature and the pressure intensity in the reaction cavity, introducing argon, nitrogen and oxygen into the reaction cavity and applying the direct current power, wherein the direct current power applied when the argon, the nitrogen and the oxygen are introduced into the reaction cavity is more than or equal to 5 times of the direct current power applied when the argon is introduced into the reaction cavity.
2. The GaN-based LED epitaxial wafer according to claim 1, wherein the maximum value of the molar concentration of oxygen in the buffer layer is 3-20%, and the minimum value of the molar concentration of oxygen in the buffer layer is 0-8%.
3. The GaN-based LED epitaxial wafer according to claim 1 or 2, wherein the buffer layer has a thickness of 5nm to 100 nm.
4. A growth method of a gallium nitride-based light emitting diode epitaxial wafer is characterized by comprising the following steps:
providing a substrate;
growing a buffer layer on the substrate;
growing an N-type semiconductor layer, an active layer and a P-type semiconductor layer on the buffer layer in sequence;
the buffer layer is made of aluminum nitride doped with oxygen, the buffer layer is of a laminated structure, and the doping concentration of oxygen in the laminated structure is gradually reduced along the laminating direction of the GaN-based light-emitting diode epitaxial wafer; the power of the growth equipment when the part of the buffer layer close to the substrate is grown is smaller than that when the part of the buffer layer close to the N-type semiconductor layer is grown; the buffer layer grows in a plurality of reaction cavities in sequence, and the volumes of oxygen introduced into the reaction cavities are different; when the buffer layer grows, firstly introducing argon into the reaction cavity and applying direct current power, then controlling the temperature and the pressure intensity in the reaction cavity, introducing argon, nitrogen and oxygen into the reaction cavity and applying the direct current power, wherein the direct current power applied when the argon, the nitrogen and the oxygen are introduced into the reaction cavity is more than or equal to 5 times of the direct current power applied when the argon is introduced into the reaction cavity.
5. The growth method according to claim 4, wherein a maximum value of the flow rate of oxygen when growing the buffer layer is 2.5% to 10% of the flow rate of nitrogen when growing the buffer layer, and a minimum value of the flow rate of oxygen when growing the buffer layer is 0% to 5% of the flow rate of nitrogen when growing the buffer layer.
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