CN109087977B - Gallium nitride-based light emitting diode epitaxial wafer and preparation method thereof - Google Patents

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

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CN109087977B
CN109087977B CN201810825958.2A CN201810825958A CN109087977B CN 109087977 B CN109087977 B CN 109087977B CN 201810825958 A CN201810825958 A CN 201810825958A CN 109087977 B CN109087977 B CN 109087977B
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type semiconductor
semiconductor layer
gallium nitride
scandium
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CN109087977A (en
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郭炳磊
王群
葛永晖
吕蒙普
胡加辉
李鹏
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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
    • H01L33/14—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 carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure
    • 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
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    • H01L33/0062—Processes for devices with an active region comprising only III-V compounds
    • H01L33/0066—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound
    • H01L33/007—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound comprising nitride compounds

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Abstract

The invention discloses a gallium nitride-based light emitting diode epitaxial wafer and a preparation method thereof, belonging to the technical field of semiconductors. The 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 N-type semiconductor layer comprises a plurality of undoped scandium aluminum nitride layers and a plurality of N-type doped gallium nitride layers, and the plurality of scandium aluminum nitride layers and the plurality of gallium nitride layers are alternately stacked. According to the invention, the undoped scandium aluminum nitride layer and the N-type doped gallium nitride layer are alternately laminated to form the N-type semiconductor layer, and the interface of the scandium aluminum nitride layer and the gallium nitride layer has strong two-dimensional electron gas, so that the transverse expansion capability of electrons can be effectively improved, the uniformity and consistency of the distribution of the electrons in the N-type semiconductor layer can be realized without arranging a current expansion layer, the series resistance of an epitaxial wafer is reduced, and the forward voltage of the chip is reduced.

Description

Gallium nitride-based light emitting diode epitaxial wafer and preparation 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 preparation method thereof.
Background
A Light Emitting Diode (LED) is a semiconductor electronic component capable of Emitting Light. As a novel efficient, environment-friendly and green solid-state illumination light source, LEDs are being rapidly and widely applied in the fields of traffic signal lights, automobile interior and exterior lights, urban landscape lighting, mobile phone backlight sources and the like.
Gallium nitride (GaN) has good thermal conductivity, and also has excellent characteristics of high temperature resistance, acid and alkali resistance, high hardness and the like, so that gallium nitride (GaN) based LEDs are receiving more and more attention and research. The conventional gallium nitride-based LED 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 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 selected from sapphire, the material of the N-type semiconductor layer and the like is generally selected from gallium nitride, the sapphire and the gallium nitride are heterogeneous materials, large lattice mismatch exists between the sapphire and the gallium nitride, and the buffer layer is used for relieving the lattice mismatch between the substrate and the N-type semiconductor layer.
In the process of implementing the invention, the inventor finds that the prior art has at least the following problems:
in a normal chip or a flip chip formed by a chip process using an epitaxial wafer, electrons in an N-type semiconductor layer migrate in a direction perpendicular to a stacking direction of the epitaxial wafer. In order to avoid too high forward voltage of the flip chip or the flip chip, the N-type semiconductor layer is usually thicker. However, when an N-type dopant such as silicon is heavily doped into the N-type semiconductor layer, many defects and impurities are easily introduced, and the introduced defects and impurities affect the spread of electrons in the N-type semiconductor layer, resulting in non-uniform distribution of electrons in the N-type semiconductor layer, and thus lowering the light emission efficiency of the LED.
In order to achieve uniformity and uniformity of electron distribution in the N-type semiconductor layer, a current spreading layer is generally introduced to improve the condition, such as a low silicon-doped gallium nitride layer disposed between the N-type semiconductor layer and the active layer. The introduced current spreading layer is beneficial to spreading electrons in the N-type semiconductor layer, but excessive series resistance is introduced at the same time, so that the forward voltage of the chip is increased.
Disclosure of Invention
The embodiment of the invention provides a gallium nitride-based light-emitting diode epitaxial wafer and a preparation method thereof, which can solve the problem that the expansion capability of electrons in an N-type semiconductor layer is improved under the condition of not influencing the forward voltage of a chip 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, the N-type semiconductor layer includes a plurality of undoped scandium aluminum nitride layers and a plurality of N-type doped gallium nitride layers, and the plurality of scandium aluminum nitride layers and the plurality of gallium nitride layers are alternately stacked.
Optionally, the scandium-aluminum nitride layer is ScxAl1-xN layer, x is more than 0 and less than 0.6.
Optionally, the thickness of the gallium nitride layer is 5 to 20 times that of the scandium aluminum nitride layer.
Optionally, the thickness of the N-type semiconductor layer is 0.5 μm to 5 μm.
Preferably, the number of the scandium-aluminum nitride layers and the number of the gallium nitride layers are both L, L is more than or equal to 10 and less than or equal to 30, and L is an integer.
More preferably, the sum of the thicknesses of one of said layers of scandium-aluminum-nitride and one of said layers of gallium-nitride is in the range 20nm to 250 nm.
Optionally, the gan-based led epitaxial wafer further includes an electron blocking layer disposed between the active layer and the P-type semiconductor layer, and the electron blocking layer includes a scandium aluminum nitride layer.
On the other hand, the embodiment of the invention provides a preparation method of a gallium nitride-based light emitting diode epitaxial wafer, which comprises the following steps:
providing a substrate;
growing a buffer layer, an N-type semiconductor layer, an active layer and a P-type semiconductor layer on the substrate in sequence;
the N-type semiconductor layer comprises a plurality of undoped scandium aluminum nitride layers and a plurality of N-type doped gallium nitride layers, and the plurality of scandium aluminum nitride layers and the plurality of gallium nitride layers are alternately stacked.
Optionally, the growth temperature of the N-type semiconductor layer is 1000 ℃ to 1200 ℃.
Optionally, the growth pressure of the N-type semiconductor layer is 100torr to 500 torr.
The technical scheme provided by the embodiment of the invention has the following beneficial effects:
the undoped scandium aluminum nitride layer and the N-type doped gallium nitride layer are alternately stacked to form the N-type semiconductor layer, and the interface of the scandium aluminum nitride layer and the gallium nitride layer has strong two-dimensional electron gas, so that the transverse expansion capability of electrons can be effectively improved, the uniformity and consistency of the distribution of the electrons in the N-type semiconductor layer are realized without arranging a current expansion layer, the series resistance of an epitaxial wafer is reduced, and the forward voltage of the chip is reduced.
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 an N-type semiconductor layer provided in an embodiment of the invention;
fig. 3 is a flowchart of a method for manufacturing an epitaxial wafer of a gallium nitride-based light emitting diode according to an 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.
Fig. 2 is a schematic structural diagram of an N-type semiconductor layer according to an embodiment of the present invention, and referring to fig. 2, in this embodiment, an N-type semiconductor layer 30 includes a plurality of undoped scandium aluminum nitride layers 31 and a plurality of N-type doped gallium nitride layers 32, and the plurality of scandium aluminum nitride layers 31 and the plurality of gallium nitride layers 32 are alternately stacked.
In fig. 2, the scandium aluminum nitride layer 31 is first stacked and the gallium nitride layer 32 is then stacked. In practical applications, the gallium nitride layer 32 may be stacked first, and then the scandium aluminum nitride layer 31 may be stacked. Meanwhile, in fig. 2, the number of the scandium aluminum nitride layers 31 is the same as the number of the gallium nitride layers 32, and in practical application, the number of the scandium aluminum nitride layers 31 may be 1 more than the number of the gallium nitride layers 32, or the number of the gallium nitride layers 32 may be 1 more than the number of the scandium aluminum nitride layers 31. Preferably, the number of the gallium nitride layers 32 is 1 more than that of the scandium aluminum nitride layers 31, and in this case, the gallium nitride layers 32 are stacked first and last in the N-type semiconductor layer 30, and the matching with other layers is good.
According to the embodiment of the invention, the undoped scandium aluminum nitride layer and the N-type doped gallium nitride layer are alternately laminated to form the N-type semiconductor layer, and the interface of the scandium aluminum nitride layer and the gallium nitride layer has strong two-dimensional electron gas, so that the transverse expansion capability of electrons can be effectively improved, the uniformity and consistency of the distribution of the electrons in the N-type semiconductor layer can be realized without arranging a current expansion layer, the series resistance of an epitaxial wafer is reduced, and the forward voltage of the chip is reduced. And the transverse expansion capability of electrons is improved, so that the mobility of the electrons is improved, and the antistatic breakdown capability of the light-emitting diode is further improved.
Alternatively, the scandium-aluminum nitride layer 31 may be ScxAl1-xAnd x is more than 0 and less than 0.6, and x is preferably 0.3, so that the scandium aluminum nitride layer can be better matched with the gallium nitride layer, and the transverse expansion capability of electrons is effectively improved.
Alternatively, the thickness of the gallium nitride layer 32 may be 5 to 20 times, preferably 12 times, the thickness of the scandium aluminum nitride layer 31. On one hand, the thickness of the gallium nitride layer is larger, the whole gallium nitride layer can be kept as gallium nitride crystals, and meanwhile, enough electrons are provided for composite luminescence in the active layer; on the other hand, the thickness of the scandium aluminum nitride layer and the thickness of the gallium nitride layer are different within a certain range, the scandium aluminum nitride layer can be well matched with the gallium nitride layer, the transverse expansion capability of electrons is effectively improved, and meanwhile the series resistance of an epitaxial wafer is prevented from being increased.
Alternatively, the thickness of the N-type semiconductor layer 30 may be 0.5 to 5 μm, preferably 3 μm. The thickness of the N-type semiconductor layer is not increased, and the increase of the series resistance of the epitaxial wafer is avoided.
Furthermore, the number of the scandium aluminum nitride layer 31 and the gallium nitride layer 32 may be L, where L is equal to or greater than 10 and equal to or less than 30, and is an integer, and L is preferably 20. Under the condition of effectively improving the transverse expansion capability of electrons, the number of each sublayer (namely the number of scandium aluminum nitride layers and gallium nitride layers) in the N-type semiconductor layer is reduced as much as possible, the realization is simplified, and the manufacture is convenient.
Further, the sum of the thicknesses of the one scandium aluminum nitride layer 31 and the one gallium nitride layer 32 is 20nm to 250nm, preferably 140nm, so that the thickness of the entire N-type semiconductor layer is within an appropriate range in accordance with the number of the scandium aluminum nitride layers and the gallium nitride layers.
Alternatively, the doping concentration of the N-type dopant in the gallium nitride layer 32 may be 1018cm-3～1019cm-3Preferably 5 x 1018cm-3. On one hand, a certain amount of electrons can be provided, and the electrons with enough amount are ensured to be injected into the active layer to carry out radiation recombination with the holes for luminescence; and on the other hand, the negative influence on the luminous efficiency of the LED, such as the reduction of the overall crystal quality of the epitaxial wafer, is avoided.
Specifically, sapphire (Al as a main component) may be used as the material of the substrate 102O3) Preferably, [0001 ] is used]Sapphire of crystal orientation. The buffer layer 20 may be made of gallium nitride (GaN). 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 buffer layer 20 may be 15nm to 35nm, preferably 25 nm. The thickness of the quantum well can be 2 nm-4 nm, and is preferably 3 nm; the thickness of the quantum barrier may be 9nm to 20nm, preferably 15 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 800nm, preferably 450 nm; the doping concentration of the P-type dopant in the P-type semiconductor layer 50 may be 1019/cm3～1020/cm3Preferably 5 x 1019cm-3。
Optionally, as shown in fig. 1, the gan-based LED epitaxial wafer may further include an electron blocking layer 60, where the electron blocking layer 60 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.
In one implementation in this embodiment, the electron blocking layer 60 may include an aluminum scandium nitride layer.
The electron blocking layer is made of scandium-aluminum nitride, the energy level of the scandium-aluminum nitride is high, and electrons can be effectively blocked from jumping into the P-type semiconductor layer to perform non-radiative luminescence with holes. Meanwhile, the crystal lattice of the scandium aluminum nitride is matched with the crystal lattice of the gallium nitride, so that the stress and the defect generated by the mismatch of the crystal lattices between the sapphire and the gallium nitride can be relieved, the crystal quality of the electron blocking layer is improved, a leakage channel is prevented from being generated in the electron blocking layer, and the electron blocking layer is not influenced to block electrons from jumping to the P-type semiconductor layer. Therefore, the blocking effect of the electron blocking layer on electrons is ensured, the non-radiative luminescence of the electrons and holes is greatly reduced, the internal quantum efficiency of the LED is improved, and the luminous efficiency of the LED is further improved.
Alternatively, the electron blocking layer 60 may have a thickness of 15nm to 80 nm. The thickness of the electron blocking layer made of scandium aluminum nitride is smaller than that of the electron blocking layer made of aluminum gallium nitride, namely the thickness of the electron blocking layer is reduced, and the forward voltage of the LED is favorably reduced.
Alternatively, the electron blocking layer 60 may consist of one aluminum scandium nitride layer, i.e. the number of aluminum scandium nitride layers in the electron blocking layer is one. Under the condition of ensuring that the electron blocking layer effectively blocks electrons, the method simplifies the implementation and is convenient to manufacture.
It is readily apparent that in the above-described embodiment, the thickness of the scandium aluminum nitride layer may be 15nm to 80nm, preferably 45 nm.
In this case, the scandium-aluminum nitride layer may be ScaAl1-aN layer, 0.1 < a < 0.4, a is preferably 0.2. On the one hand, the electron blocking layer can be guaranteed to play a role in blocking electrons from jumping to the P-type semiconductor layer, and on the other hand, the scandium aluminum nitride layer has high bulk charge density and carrier mobility, so that holes can be transversely expanded in the electron blocking layer, the injection efficiency of the holes is improved, the internal quantum efficiency of the LED is further improved, and the luminous efficiency of the LED is finally improved.
Optionally, the electron blocking layer 60 may be formed by alternately stacking a plurality of scandium aluminum nitride layers and a plurality of P-type doped gallium nitride layers, that is, the number of scandium aluminum nitride layers in the electron blocking layer may also be multiple, and in this case, the electron blocking layer further includes a plurality of P-type doped gallium nitride layers, and the plurality of scandium aluminum nitride layers and the plurality of gallium nitride layers are alternately stacked. The multiple gallium nitride layers and the multiple scandium aluminum nitride layers are alternately stacked, so that the matching degree of the electronic barrier layer and the gallium nitride crystal lattice can be further improved, the stress and the defect generated by the lattice mismatch between the sapphire and the gallium nitride can be effectively relieved, the crystal quality of the electronic barrier layer is enabled, a leakage channel generated in the electronic barrier layer is avoided as far as possible, and the electronic barrier layer can effectively prevent electrons from jumping to the P-type semiconductor layer.
In this case, the number of the scandium aluminum nitride layer and the gallium nitride layer may be M, where M is 4 ≦ M ≦ 10 and is an integer, and M is preferably 7. Under the condition of ensuring that the crystal quality of the electron barrier layer is good, the number of each sublayer in the electron barrier layer (namely the number of the scandium aluminum nitride layer and the gallium nitride layer) is reduced as much as possible, the realization is simplified, and the manufacture is convenient.
Further, the sum of the thicknesses of one scandium aluminum nitride layer and one gallium nitride layer may be 3nm to 8nm, preferably 6nm, in order to match the number of scandium aluminum nitride layers and gallium nitride layers, so that the thickness of the entire electron blocking layer is within a suitable range.
Further, the thickness of the scandium aluminum nitride layer may be 1 to 4 times, preferably 3 times, the thickness of the gallium nitride layer. On one hand, the scandium-aluminum nitride layer is relatively thick, so that electrons can be effectively prevented from jumping into the P-type semiconductor layer to be non-radiatively compounded with the electrons; on the other hand, the difference between the thickness of the gallium nitride layer and the thickness of the scandium aluminum nitride layer is not large, the gallium nitride layer can play a role in matching gallium nitride crystals, the crystal quality of the electron blocking layer is improved, and the blocking effect of the scandium aluminum nitride layer on electrons is guaranteed.
In this case, the scandium-aluminum nitride layer may be ScbAl1-bN layer, 0.2 < b < 0.6, b is preferably 0.4. On the one hand, the electron blocking layer can be guaranteed to play a role in blocking electrons from jumping to the P-type semiconductor layer, and on the other hand, the scandium aluminum nitride layer has high bulk charge density and carrier mobility, so that holes can be transversely expanded in the electron blocking layer, the injection efficiency of the holes is improved, the internal quantum efficiency of the LED is further improved, and the luminous efficiency of the LED is finally improved.
In addition, in the two implementation manners, the scandium-aluminum nitride layer may be doped with a P-type dopant to provide partial holes, so that the holes are injected into the active layer to perform compound light emission with electrons, the internal quantum efficiency of the LED is improved, and the light emission efficiency of the LED is further improved. In practical applications, the scandium aluminum nitride layer may not be doped.
Specifically, when the scandium aluminum nitride layer is doped with a P-type dopant, the doping concentration of the P-type dopant in the scandium aluminum nitride layer may be the same as the doping concentration of the P-type dopant in the gallium nitride layer in the electron blocking layer, so that a better matching effect is achieved.
Alternatively, the doping concentration of the P-type dopant in the gallium nitride layer in the electron blocking layer 60 may be 1017/cm3～1018/cm3Preferably 5 x 1017/cm3. On one hand, a certain number of holes can be provided, which is beneficial to injecting the holes into the active layer to perform radiation recombination luminescence with electrons, so that the internal quantum efficiency of the LED is improved, and the luminous efficiency of the LED is further improved; on the other hand, negative influences on the luminous efficiency of the LED, such as influences on a hole injection active layer in the P-type semiconductor layer, reduction of the crystal quality of the electron blocking layer and the like, are avoided.
In another implementation of this embodiment, the material of the electron blocking layer 60P-type doped aluminum gallium nitride (AlGaN), such as Al, may be usedyGa1-yN，0.1＜y＜0.5。
Specifically, the thickness of the electron blocking layer 60 may be 50nm to 150nm, preferably 100 nm.
Further, as shown in fig. 1, the gan-based led epitaxial wafer may further include a low temperature P-type layer 70, where the low temperature P-type layer 70 is disposed between the active layer 40 and the electron blocking layer 60 to prevent indium atoms in the active layer from being separated out due to a high growth temperature of the electron blocking layer, which affects the light emitting efficiency of the led.
Specifically, the material of the low temperature P-type layer 70 may be the same as the P-type semiconductor layer 50, which is P-type doped gallium nitride in the present embodiment.
Further, the thickness of the low temperature P-type layer 70 may be 50nm to 150nm, preferably 100 nm; the doping concentration of the P-type dopant in the low-temperature P-type layer 70 may be 1020/cm3～1021/cm3Preferably 5 x 1020/cm3。
Optionally, as shown in fig. 1, the gan-based led epitaxial wafer may further include an undoped gan layer 71, and the undoped gan 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.
Further, the thickness of the undoped gallium nitride layer 71 may be 1 μm to 5 μm, preferably 3 μm.
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 a high-temperature buffer layer on the two-dimensional growth layer at a high temperature. The three-dimensional nucleation layer, the two-dimensional recovery layer, and the high-temperature buffer layer are collectively referred to as an undoped gallium nitride layer in this embodiment.
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 can 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 light emitting diode epitaxial wafer may further include a P-type contact layer 73, and the P-type contact layer 73 is laid on the P-type semiconductor layer 50to form ohmic contact with an electrode or a transparent conductive film formed in a chip manufacturing process.
Specifically, the P-type contact layer 73 may be made of P-type doped indium gallium nitride.
Further, the thickness of the P-type contact layer 73 may be 5nm to 20nm, preferably 12.5 nm; the doping concentration of the P-type dopant in the P-type contact layer 73 may be 1021/cm3～1022/cm3Preferably 6 x 1021/cm3。
One specific implementation of the gan-based led epitaxial wafer shown in fig. 1 includes: the semiconductor device 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, wherein 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. Wherein, the material of the substrate 10 adopts sapphire; the buffer layer 20 is made of gallium nitride and has a thickness of 25 nm; the N-type semiconductor layer 30 includes 10 undoped Sc alternately stacked0.1Al0.9N layer and 10N-type doped GaN layers, Sc0.1Al0.9The thickness of the N layer is 20nm, the thickness of the GaN layer is 230nm, and the doping concentration of the N-type dopant in the GaN layer is 5 x 1018cm-3(ii) a The active layer 40 comprises 8 quantum wells and 8 quantum barriers which are alternately stacked, wherein the quantum wells are made of indium gallium nitride, the thicknesses of the quantum wells are 3nm, the quantum barriers are made of gallium nitride, and the thicknesses of the quantum barriers are 15 nm; the P-type semiconductor layer 50 is made of P-type doped gallium nitride with a thickness of 450nm and a doping concentration of 5 x 1019cm-3。
The epitaxial wafer is made into a chip, and the chip and the N-type semiconductor layer are formed by doping with 5 × 10 concentration with a thickness of 3 μm18cm-3Compared with a chip made of an epitaxial wafer with the same structure of other layers, the GaN layer of the N-type dopant has the advantage that the luminous efficiency is improved by 2-3%.
One specific implementation of the gan-based led epitaxial wafer shown in fig. 1 includes: the semiconductor device 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, wherein 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. Wherein, the material of the substrate 10 adopts sapphire; the buffer layer 20 is made of gallium nitride and has a thickness of 25 nm; the N-type semiconductor layer 30 includes 20 undoped Sc alternately stacked0.3Al0.7N layer and 20N-type doped GaN layers, Sc0.3Al0.7The thickness of the N layer is 10nm, the thickness of the GaN layer is 130nm, and the doping concentration of the N-type dopant in the GaN layer is 5 x 1018cm-3(ii) a The active layer 40 comprises 8 quantum wells and 8 quantum barriers which are alternately stacked, wherein the quantum wells are made of indium gallium nitride, the thicknesses of the quantum wells are 3nm, the quantum barriers are made of gallium nitride, and the thicknesses of the quantum barriers are 15 nm; the P-type semiconductor layer 50 is made of P-type doped gallium nitride with a thickness of 450nm and a doping concentration of 5 x 1019cm-3。
The epitaxial wafer is made into a chip, and the chip and the N-type semiconductor layer are formed by doping with 5 × 10 concentration with a thickness of 3 μm18cm-3Compared with a chip made of an epitaxial wafer with the same structure of other layers and composed of the GaN layer of the N-type dopant, the luminous efficiency is improvedThe height is 3 to 4 percent higher.
One specific implementation of the gan-based led epitaxial wafer shown in fig. 1 includes: the semiconductor device 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, wherein 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. Wherein, the material of the substrate 10 adopts sapphire; the buffer layer 20 is made of gallium nitride and has a thickness of 25 nm; the N-type semiconductor layer 30 includes 30 undoped Sc alternately stacked0.5Al0.5N layer and 30N-type doped GaN layers, Sc0.5Al0.5The thickness of the N layer is 2nm, the thickness of the GaN layer is 18nm, and the doping concentration of an N-type dopant in the GaN layer is 5 x 1018cm-3(ii) a The active layer 40 comprises 8 quantum wells and 8 quantum barriers which are alternately stacked, wherein the quantum wells are made of indium gallium nitride, the thicknesses of the quantum wells are 3nm, the quantum barriers are made of gallium nitride, and the thicknesses of the quantum barriers are 15 nm; the P-type semiconductor layer 50 is made of P-type doped gallium nitride with a thickness of 450nm and a doping concentration of 5 x 1019cm-3。
The epitaxial wafer is made into a chip, and the chip and the N-type semiconductor layer are formed by doping with 5 × 10 concentration with a thickness of 3 μm18cm-3Compared with a chip made of an epitaxial wafer with the same structure of other layers, the GaN layer of the N-type dopant has the advantage that the luminous efficiency is improved by 1-2%.
The embodiment of the invention provides a preparation method of a gallium nitride-based light-emitting diode epitaxial wafer, which is suitable for preparing the light-emitting diode epitaxial wafer shown in figure 1. Fig. 3 is a flowchart of a method for manufacturing an epitaxial wafer of a gallium nitride-based light emitting diode according to an embodiment of the present invention, and referring to fig. 3, the method includes:
step 201: a substrate is provided.
Optionally, the step 201 may include:
controlling the temperature to be 1000-1200 ℃ (preferably 1100 ℃), and annealing the substrate for 6-10 minutes (preferably 8 minutes) in a hydrogen atmosphere;
the substrate is subjected to a nitridation process.
The surface of the substrate is cleaned through the steps, impurities are prevented from being doped into the epitaxial wafer, and the growth quality of the epitaxial wafer is improved.
Step 202: a buffer layer, an N-type semiconductor layer, an active layer and a P-type semiconductor layer are sequentially grown on a substrate.
In this embodiment, the N-type semiconductor layer includes a plurality of undoped scandium aluminum nitride layers and a plurality of N-type doped gallium nitride layers, and the plurality of scandium aluminum nitride layers and the plurality of gallium nitride layers are alternately stacked.
Alternatively, the growth temperature of the N-type semiconductor layer may be 1000 to 1200 deg.c, preferably 1100 deg.c. By adopting high-temperature growth, the crystal quality of the N-type semiconductor layer is better, and the luminous efficiency of the LED is favorably improved.
Preferably, the growth pressure of the N-type semiconductor layer may be 100torr to 500torr, and preferably 300 torr. The crystal quality of the N-type semiconductor layer is better by matching with the growth temperature of the N-type semiconductor layer, and the luminous efficiency of the LED is improved.
Specifically, this step 202 may include:
firstly, controlling the temperature to be 400-600 ℃ (preferably 500 ℃), and the pressure to be 400-600 torr (preferably 500torr), and growing a buffer layer on a substrate;
secondly, growing an N-type semiconductor layer on the buffer layer;
thirdly, growing an active layer on the N-type semiconductor layer; wherein the growth temperature of the quantum well is 720 ℃ to 829 ℃ (preferably 770 ℃), and the pressure is 100torr to 500torr (preferably 300 torr); the growth temperature of the quantum barrier is 850-959 deg.C (preferably 900 deg.C), and the pressure is 100-500 torr (preferably 300 torr);
and fourthly, controlling the temperature to be 850-1080 ℃ (preferably 950 ℃) and the pressure to be 100-300 torr (preferably 200torr), and growing the P-type semiconductor layer on the active layer.
Optionally, after the first step, the preparation method may further comprise:
the buffer layer is subjected to in-situ annealing treatment for 5 to 10 minutes (preferably 8 minutes) at a controlled temperature of 1000 to 1200 c (preferably 1100 c) and a pressure of 400to 600torr (preferably 500 torr).
Optionally, before the second step, the preparation method may further include:
and growing an undoped gallium nitride layer on the buffer layer.
Accordingly, an N-type semiconductor layer is grown on the undoped gallium nitride layer.
Specifically, growing an undoped gallium nitride layer on the buffer layer may include:
an undoped gallium nitride layer is grown on the buffer layer at a temperature of 1000 ℃ to 1100 ℃ (preferably 1050 ℃) and a pressure of 100torr to 500torr (preferably 300 torr).
Optionally, before the third step, the preparation 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 fourth step, the preparation 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 temperature is controlled to be 850 ℃ to 1080 ℃ (preferably 950 ℃), the pressure is controlled to be 200torr to 500torr (preferably 350torr), and the electron blocking layer is grown on the active layer.
Preferably, before growing the electron blocking layer on the active layer, the preparation 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 500 ℃ to 800 ℃ (preferably 675 ℃) and the pressure is 50torr to 500torr (preferably 300torr), and the low-temperature P-type layer is grown on the active layer.
Optionally, after the fifth step, the preparation 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 temperature is controlled to be 800 ℃ to 1050 ℃ (preferably 925 ℃), and the pressure is controlled to be 100torr to 300torr (preferably 200torr), and the P-type contact layer is grown on the P-type semiconductor layer.
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, a scandium phosphino-carbene complex is used as a scandium source, silane is used as an N-type dopant, and magnesium metallocene 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 (7)

1. 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 and the active layer are arranged on the substrateThe source layer and the P-type semiconductor layer are sequentially stacked on the substrate, and the N-type semiconductor layer comprises a plurality of undoped scandium aluminum nitride layers and a plurality of N-type doped gallium nitride layers, the plurality of scandium aluminum nitride layers and the plurality of gallium nitride layers are alternately stacked, and the scandium aluminum nitride layers in the N-type semiconductor layer are ScxAl1-xThe x is more than 0 and less than 0.6, and the thickness of the gallium nitride layer is 5-20 times of that of the scandium aluminum nitride layer;
the gallium nitride-based light-emitting diode epitaxial wafer further comprises an electron barrier layer, the electron barrier layer is arranged between the active layer and the P-type semiconductor layer and comprises a scandium aluminum nitride layer, and the scandium aluminum nitride layer in the electron barrier layer is ScaAl1-aN layer, 0.1 < a < 0.4.
2. The GaN-based LED epitaxial wafer according to claim 1, wherein the thickness of the N-type semiconductor layer is 0.5-5 μm.
3. The GaN-based LED epitaxial wafer according to claim 2, wherein the number of the scandium aluminum nitride layers and the number of the gallium nitride layers in the N-type semiconductor layer are both L, L is greater than or equal to 10 and less than or equal to 30, and L is an integer.
4. The GaN-based LED epitaxial wafer as claimed in claim 3, wherein the sum of the thicknesses of one of the scandium-aluminum-nitride layers and one of the gallium-nitride layers in the N-type semiconductor layer is 20nm to 250 nm.
5. A preparation 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, an N-type semiconductor layer, an active layer and a P-type semiconductor layer on the substrate in sequence;
wherein the N-type semiconductor layer comprises a plurality of undoped scandium-aluminum nitride layers and a plurality of N-type doped scandium-aluminum nitride layersThe scandium-aluminum nitride layer and the gallium nitride layer are alternately stacked, and the scandium-aluminum nitride layer in the N-type semiconductor layer is ScxAl1-xThe x is more than 0 and less than 0.6, and the thickness of the gallium nitride layer is 5-20 times of that of the scandium aluminum nitride layer;
the gallium nitride-based light-emitting diode epitaxial wafer further comprises an electron barrier layer, the electron barrier layer is arranged between the active layer and the P-type semiconductor layer and comprises a scandium aluminum nitride layer, and the scandium aluminum nitride layer in the electron barrier layer is ScaAl1-aN layer, 0.1 < a < 0.4.
6. The production method according to claim 5, wherein the growth temperature of the N-type semiconductor layer is 1000 ℃ to 1200 ℃.
7. The method according to claim 6, wherein the growth pressure of the N-type semiconductor layer is 100to 500 torr.
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