CN115312584A - Gallium nitride epitaxial wafer and preparation method thereof - Google Patents

Gallium nitride epitaxial wafer and preparation method thereof Download PDF

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CN115312584A
CN115312584A CN202111364861.4A CN202111364861A CN115312584A CN 115312584 A CN115312584 A CN 115312584A CN 202111364861 A CN202111364861 A CN 202111364861A CN 115312584 A CN115312584 A CN 115312584A
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gallium nitride
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nitride epitaxial
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李利哲
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Jiangsu Third Generation Semiconductor Research Institute Co Ltd
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Abstract

The application belongs to the technical field of semiconductors, and discloses a gallium nitride epitaxial wafer and a preparation method thereof, aiming at solving the problem that the existing epitaxial wafer is easy to warp due to lattice mismatch or stress. The gallium nitride epitaxial wafer includes: the low-temperature AlN buffer layer, the high-temperature AlN buffer layer, the loose AlGaN layer, the aluminum gradual change layer, the gallium nitride transition layer and the gallium nitride epitaxial layer are sequentially arranged on the substrate. The low-temperature AlN buffer layer and the high-temperature AlN buffer layer can buffer lattice mismatch between the substrate and the gallium nitride transition layer, the loose AlGaN layer can play a role in relieving stress, the aluminum gradual change layer can improve lattice match of the gallium nitride layer above the aluminum gradual change layer, and gallium nitride epitaxy can further reduce stress generated by lattice mismatch between the substrate and the epitaxial layer through the gallium nitride transition layer, so that warping of a large-size epitaxial wafer due to lattice mismatch or stress can be prevented. The gallium nitride epitaxial layer may be prepared by a CVD apparatus.

Description

Gallium nitride epitaxial wafer and preparation method thereof
Technical Field
The application belongs to the technical field of semiconductors, and particularly relates to a gallium nitride epitaxial wafer and a preparation method thereof.
Background
Gallium nitride (GaN) is used as a third-generation wide-band-gap semiconductor material, has high application value in the field of microwave devices due to the characteristics of good physical properties, stability and the like, and is expected to play an important role in the aspects of aviation, high-temperature radiation, radar, communication, automotive electronics and the like. However, the gan single crystal substrate is difficult to prepare, and is usually formed by a heteroepitaxy method, in which the epitaxial wafer is easily warped due to lattice mismatch or stress in a large size, and the problem of warping is more prominent as the size of the substrate increases. Therefore, it is necessary to solve the problems of stress and warpage due to lattice mismatch in the prior art.
Disclosure of Invention
In order to solve the problem that the conventional epitaxial wafer is easy to warp due to lattice mismatch or stress, a gallium nitride epitaxial wafer and a preparation method thereof are provided.
In order to achieve the purpose, the following technical scheme is adopted in the application:
a gallium nitride epitaxial wafer comprises a substrate, wherein a low-temperature AlN buffer layer, a high-temperature AlN buffer layer, a loose AlGaN layer, an aluminum gradient layer, a gallium nitride transition layer and a gallium nitride epitaxial layer are sequentially arranged on the substrate.
Preferably, the loose AlGaN layer is formed by depositing an AlInGaN layer on the high temperature AlN buffer layer and then precipitating all indium.
Preferably, after the formation of the bulk AlGaN layer, the bulk AlGaN layer is purged with nitrogen gas to remove all indium that precipitates from the AlInGaN layer.
Preferably said substrate comprises a sapphire substrate; the thickness of the low-temperature AlN buffer layer is 10-15nm, and the forming temperature is 500-650 ℃; the thickness of the high-temperature AlN buffer layer is 40-55nm, and the forming temperature is 800-1100 ℃; the thickness of the AlInGaN layer is 100-300nm; the thickness of the aluminum gradient layer is 80-150nm; the thickness of the gallium nitride transition layer is 50-100nm.
Preferably, the gallium epitaxial layer consists of a first gallium nitride epitaxial layer and a second gallium nitride epitaxial layer, the total thickness of the gallium epitaxial layer is 1.5-2 microns, and the thickness of the first gallium nitride epitaxial layer is 100-180nm.
The preparation method based on the gallium nitride epitaxial wafer comprises the following steps of: the method comprises the steps that a low-temperature AlN buffer layer, a high-temperature AlN buffer layer and an AlInGaN layer are sequentially arranged on a substrate, indium in the AlInGaN layer is completely separated out to form a loose AlGaN layer, and an aluminum gradient layer, a gallium nitride transition layer and a gallium nitride epitaxial layer are sequentially deposited on the loose AlGaN layer.
The preparation method comprises the following steps:
step S1: placing a substrate into a reaction chamber;
step S2: introducing an aluminum source and a nitrogen source into the reaction chamber, controlling the temperature in the reaction chamber to be a first temperature, and forming a low-temperature AlN buffer layer on the substrate;
and step S3: increasing the temperature in the reaction chamber to a second temperature, and continuously introducing an aluminum source and a nitrogen source to form a high-temperature AlN buffer layer on the low-temperature AlN buffer layer; the second temperature is greater than the first temperature;
and step S4: keeping the introduction of an aluminum source and a nitrogen source, introducing an indium source and a gallium source into the reaction chamber, and forming an AlInGaN layer on the high-temperature AlN buffer layer; then stopping introducing an aluminum source, a nitrogen source, an indium source and a gallium source at the same time, forming a loose AlGaN layer after indium in the AlInGaN layer is completely separated out, and purging the surface of the loose AlGaN layer by using nitrogen to remove the indium completely separated out from the AlInGaN layer;
step S5: controlling the pressure and the temperature in the reaction chamber to be unchanged, reducing the introduction of an aluminum source, and forming an aluminum gradient layer on the surface of the loose AlGaN layer;
step S6: stopping introducing an aluminum source, and forming a gallium nitride transition layer on the surface of the aluminum gradual change layer;
step S7: and forming a gallium nitride epitaxial layer on the gallium nitride transition layer.
Preferably, the gallium nitride epitaxial layer comprises: a first gallium nitride epitaxial layer and a second gallium nitride epitaxial layer; the temperature and the pressure in the reaction chamber in the growth stage of the first gallium nitride epitaxial layer are both higher than the temperature and the pressure in the reaction chamber in the growth stage of the second gallium nitride epitaxial layer, but the growth speed of gallium nitride in the growth stage of the first gallium nitride epitaxial layer is lower than the growth speed of gallium nitride in the growth stage of the second gallium nitride epitaxial layer.
Specifically, the step S2: the nitrogen source is ammonia gas, the aluminum source is trimethyl aluminum, the first temperature is 500-650 ℃, and the thickness of the formed low-temperature AlN buffer layer is 10-15nm;
and step S3: the first temperature is 800-1100 ℃, and the thickness of the formed high-temperature AlN buffer layer is 40-55nm; and step S4: the gallium source is trimethyl gallium, the indium source is trimethyl indium, the pressure in the reaction chamber is 150-200mbar, the temperature is 1050-1100 ℃, and simultaneously 30-60S of introducing the aluminum source, the nitrogen source, the indium source and the gallium source is suspended; controlling the introduction of nitrogen and the direction of the nitrogen, blowing the droplet indium from the surface of the AlInGaN layer, and collecting the blown droplet indium in a recovery device.
Forming a low-temperature AlN buffer layer next to the substrate, wherein when the small and dense grain-shaped aluminum nitride forms the low-temperature AlN buffer layer, a certain gap exists between the island-shaped grains; in order to reduce the surface energy and close the gap by the deformation of the crystal grains, a high-temperature AlN buffer layer is provided on the low-temperature AlN buffer layer. The ability to form a dense high temperature AlN buffer layer at high temperatures can improve the quality of epitaxial wafer formation.
The microstructure of the formed loose AlGaN layer presents an irregular porous structure and can play a role in relieving stress, and the aluminum gradual change layer can improve the lattice matching of the gallium nitride layer above the aluminum gradual change layer. And a gallium nitride transition layer is deposited between the upper part of the aluminum gradual change layer and the gallium nitride epitaxial layer, so that the stress generated by lattice mismatch between the substrate and the epitaxial layer can be further reduced, and the warping of a large-size epitaxial wafer caused by lattice mismatch or stress can be prevented.
It should be noted that the "low temperature" and "high temperature" in the "low-temperature AlN buffer layer" and "high-temperature AlN buffer layer" described in the present application are names for the sake of distinguishing the AlN buffer layers formed at two different temperatures, and the high temperature and the low temperature herein do not refer to a temperature range. The low-temperature AlN buffer layer and the high-temperature AlN buffer layer can be replaced by a first AlN buffer layer and a second AlN buffer layer correspondingly, and the forming temperature of the first AlN buffer layer is lower than that of the second AlN buffer layer.
Drawings
Fig. 1 is a schematic cross-sectional structure view of a gallium nitride epitaxial wafer structure according to an embodiment of the present application.
Fig. 2 is a schematic view of a growth process for preparing an epitaxial layer of gallium nitride according to an embodiment of the present disclosure.
Illustration of the drawings: 1-substrate, 2-low temperature AlN buffer layer, 3-high temperature AlN buffer layer, 4-loose AlGaN layer, 5-aluminum gradual change layer, 6-gallium nitride transition layer and 7-gallium nitride epitaxial layer.
Detailed Description
The above-described scheme is further illustrated below with reference to specific examples. It should be understood that these examples are for illustrative purposes and are not intended to limit the scope of the present application. The conditions employed in the examples may be further adjusted as determined by the particular manufacturer, and the conditions not specified are typically those used in routine experimentation.
In the first embodiment, a gallium nitride epitaxial wafer as shown in fig. 1 includes a substrate 1, on which a low-temperature AlN buffer layer 2, a high-temperature AlN buffer layer 3, a loose AlGaN layer 4, an aluminum graded layer 5, a gallium nitride transition layer 6, and a gallium nitride epitaxial layer 7 are sequentially disposed.
The gallium nitride epitaxy can play a role in relieving stress through the loose AlGaN layer, the lattice matching of the gallium nitride layer above the aluminum gradual change layer can be improved, the gallium nitride transition layer can reduce stress generated by lattice mismatch between the substrate and the epitaxy layer, and warping of a large-size epitaxial wafer due to lattice mismatch or stress can be prevented. The gallium nitride epitaxial layer may be prepared by a CVD apparatus.
Embodiment two, a method for preparing a gallium nitride epitaxial wafer, comprising the following steps: the method comprises the steps of sequentially arranging a low-temperature AlN buffer layer, a high-temperature AlN buffer layer and an AlInGaN layer on a substrate, separating out all indium in the AlInGaN layer to form a loose AlGaN layer, blowing the surface of the loose AlGaN layer by using nitrogen, and then sequentially depositing an aluminum gradual change layer, a gallium nitride transition layer and a gallium nitride epitaxial layer on the loose AlGaN layer.
In a preferred embodiment: the growth flow diagram of the preparation of the gallium nitride epitaxial layer is shown in fig. 2.
Firstly, a substrate is placed in a reaction chamber, wherein the substrate can be a sapphire substrate, a cleaning step is preferentially carried out before the substrate is placed in the reaction chamber, the cleaning can remove pollution particles and impurities on the surface of the substrate, the cleaning comprises wet cleaning and dry cleaning, the wet cleaning is carried out firstly, deionized water is used for cleaning the surface of the substrate, then dry cleaning is carried out, for example, nitrogen is used for blowing the surface of the substrate, and the substrate is dried, so that the influence possibly brought by moisture is reduced;
secondly, controlling the temperature in the reaction chamber at 500-650 ℃, and introducing an aluminum source and a nitrogen source to form a low-temperature AlN buffer layer, wherein the thickness of the low-temperature AlN buffer layer is 10-15nm; then, increasing the temperature in the reaction chamber to 800-1100 ℃, and continuously introducing an aluminum source and a nitrogen source to form a high-temperature AlN buffer layer, wherein the thickness of the high-temperature AlN buffer layer is 40-55nm, the aluminum source is trimethylaluminum, and the nitrogen source is ammonia gas; in the invention, a low-temperature AlN buffer layer is firstly formed on the surface of a substrate, the sapphire substrate is made of alumina and has better lattice matching with AlN, the stress of AlN and the substrate is smaller, and the AlN layer formed at a lower temperature forms a plurality of fine and dense grain-shaped aluminum nitride because the temperature range is 500-650 ℃, and a certain gap exists between island-shaped grains when the aluminum nitride layer is formed, thus forming a polycrystalline AlN layer. The compact high-temperature aluminum nitride layer can be formed at high temperature and is a single crystal AlN layer, the structure is compact, and the formation quality of the epitaxial wafer can be improved.
After the high-temperature AlN buffer layer is formed, keeping the introduction of an aluminum source and a nitrogen source, introducing an indium source and a gallium source into the reaction chamber, forming an AlInGaN layer on the high-temperature AlN buffer layer, wherein the gallium source is trimethyl gallium, the indium source is trimethyl indium, the pressure in the reaction chamber is 150-200mbar, the temperature is 1050-1100 ℃, and the thickness of the formed AlInGaN layer is 100-300nm. The AlInGaN layer is formed for forming a loose AlGaN layer In the follow-up mode, when the AlInGaN layer with a certain thickness is formed, indium In the AlInGaN layer is difficult to precipitate at high temperature when the thickness of the AlInGaN layer is larger than 300nm, in-AlGaN alloy is easy to form, and after the AlInGaN layer with the thickness smaller than 100nm is formed into the loose AlGaN layer, stress relieving is difficult to achieve through a loose structure. Therefore, when the AlInGaN layer is formed in the invention, the thickness is controlled within the range of 100-300nm, so that the loose AlGaN layer can be conveniently formed, and the loose structure can be utilized to play a role in relieving stress.
Then stopping introducing the aluminum source, the nitrogen source, the indium source and the gallium source at the same time, wherein the time for stopping introducing is 30-60S, when the introduction of the reaction source gas is stopped, because the temperature In the reaction chamber is higher, in is easy to precipitate near the deposition temperature (above 1000 ℃), indium can be precipitated from AlInGaN during the time of suspending the introduction, and all indium In the AlInGaN layer can be precipitated during the time;
controlling the pressure and the temperature in the reaction chamber to be unchanged, and reducing the introduction of an aluminum source to form an aluminum gradient layer;
stopping introducing the aluminum source, and forming a gallium nitride transition layer on the surface of the aluminum gradual change layer;
subsequently, a gallium nitride epitaxial layer is formed on the gallium nitride transition layer.
In a preferred embodiment, after all indium in the AlInGaN layer is precipitated, the AlInGaN layer is purged by using nitrogen gas, the introduction of nitrogen gas and the direction of the nitrogen gas are controlled, the precipitated indium in a droplet shape is purged from the surface of the AlInGaN layer, and the purged indium in a droplet shape is collected in a recovery device to prevent other layer structures from being polluted. The indium is precipitated and attached to the surface of the loose AlGaN layer to form droplet indium, the droplet indium is easy to form an alloy layer with an indium structure formed subsequently during subsequent deposition, for example, when a GaN layer is formed subsequently, if the indium exists, the indium and the GaN layer form an In-GaN alloy, and after the alloy layer is formed, on one hand, an epitaxial wafer is difficult to separate from a substrate wafer, and on the other hand, the existence of the indium can change the conductivity of the GaN layer, so that the indium can influence the luminescence performance no matter the indium is used as an LED material or a substrate material of a laser.
Forming an AlInGaN layer on the high-temperature AlN layer, wherein during the formation of AlN, an aluminum source and a nitrogen source are introduced during the formation of AlN, after the high-temperature AlN layer with a preset thickness is formed, the introduction of the aluminum source and the nitrogen source is kept, and an indium source and a gallium source are introduced into the reaction chamber, wherein the aluminum source is trimethylaluminum, the gallium source is trimethylgallium, the indium source is trimethylindium, and the nitrogen source is NH 3 The pressure in the reaction chamber is 150-200mbar, the temperature is 1050-1100 ℃, and Al is formedAnd (4) an InGaN layer, stopping the introduction of an aluminum source, a nitrogen source, an indium source and a gallium source at the same time, and stopping the introduction for 30-60S.
The AlInGaN layer stops growing after being deposited, the stop growing time is 30-60S, indium is easy to precipitate at high temperature (the temperature for forming the AlInGaN layer is 1050-1100 ℃, the temperature can be maintained near the growing temperature during stop growing), the precipitated indium can be attached to the surface of the AlInGaN layer, after the indium in the AlInGaN is precipitated, the AlInGaN layer can be formed into a loose AlGaN layer structure, the indium in the AlInGaN layer is completely precipitated by controlling the stop growing time, and therefore the loose AlGaN layer can be formed.
After the reaction source is temporarily stopped to be led in for a preset time, controlling the temperature in the reaction chamber to be 1150-1200 ℃ (the forming temperature is higher than the temperature when the AlInGaN layer is formed), leading an aluminum source, a gallium source and a nitrogen source into the reaction chamber, and controlling the led-in amount of the aluminum source, the gallium source and the nitrogen source to form Al x Ga 1-x A N-Al gradient layer, wherein x is the content of Al and is not less than 0<1, continuously reducing the introduction amount of an Al source in the introduction process until the aluminum source is not introduced completely, wherein the GaN layer is formed when the aluminum source is not introduced completely, the gallium source is trimethyl gallium, the flow rate of the trimethyl gallium is 150-200sccm, the aluminum source is trimethyl aluminum, the flow rate of the trimethyl aluminum is 150-200sccm, the nitrogen source is ammonia gas, the time from the reduction of the introduction of the aluminum source to the complete non-introduction of the aluminum source is 10-25min, and the thickness of the formed AlxGa1-xN layer is 80-150nm. After the formed loose AlGaN layer, although the stress can be relieved, because the AlGaN layer is internally provided with a loose gap, when a gallium nitride layer is epitaxially formed on the AlGaN layer, because the crystallization quality of the loose structure below is poor, the crystallization quality of an epitaxial layer can be influenced, the quality of an epitaxial wafer can be greatly influenced, and the formation of Al is improved x Ga 1-x The forming temperature of the N aluminum gradual change layer can improve the crystallization quality of the aluminum gradual change layer, the aluminum content is reduced, the formed aluminum gradual change layer is well matched with a gallium nitride epitaxial layer to be formed above the aluminum gradual change layer, and stress generated by lattice mismatch is prevented.
After the introduction amount of the aluminum source is gradually reduced until the aluminum source is not introduced completely, continuously maintaining the temperature and the pressure in the reaction cavity when the aluminum source is not introduced, continuously introducing the nitrogen source and the gallium source to form a gallium nitride transition layer, at the moment, the reaction condition does not need to be changed, only the reaction condition needs to be continuously maintained, and the reaction source is continuously introduced, and after the introduction of the aluminum source is stopped, the time is maintained for 2-10min to form the gallium nitride transition layer with the thickness of 50-100nm, wherein the gallium nitride transition layer mainly improves the crystallization quality of a subsequent gallium nitride epitaxial wafer.
Then, a gallium nitride epitaxial layer is formed on the gallium nitride transition layer, and the subsequent step of forming the gallium nitride epitaxial layer can refer to the specific steps of the invention.
And forming a gallium nitride epitaxial layer with the total thickness of 1.5-2 microns on the gallium nitride transition layer. The method comprises the following steps: the formation of the gallium nitride epitaxial layer includes two stages,
forming a first gallium nitride epitaxial layer and a second gallium nitride epitaxial layer, wherein the specific forming process comprises the following steps:
the first stage is as follows: controlling the temperature of the reaction chamber to 1080-1150 ℃, introducing a gallium source and a nitrogen source, wherein the gallium source is trimethyl gallium, the flow rate of the trimethyl gallium is 150-200sccm, and the nitrogen source is NH 3 Controlling the flow rate of the gallium source and the nitrogen source, controlling the pressure of the reaction chamber at 300-350mbar, controlling the growth speed of GaN at 10-15nm/min, controlling the growth time, and controlling the thickness of the GaN grown at the first stage at 100-180nm. In the first stage, the reaction chamber is controlled to be in a growing high-pressure and high-temperature state, and GaN grows at a low speed, so that a dense GaN layer with good lattice constant matching quality can be formed on the transition GaN layer, the stress between the upper epitaxial layer and the lower layer structure can be further reduced, and the quality of the whole external GaN is improved. However, the growth at this stage is slow, and the growth thickness is not too thick, so that the growth time can be saved.
In the method, the GaN epitaxial wafer is formed in two stages, and in the first stage, the temperature and the pressure are higher, the growth speed is slower, so that a bottom epitaxial wafer with higher quality can be formed,
the growth speed is controlled at the second stage, a thicker epitaxial wafer can be quickly formed, and because the quality of the first layer of epitaxial wafer below is higher, the quality of the epitaxial wafer above is also higher, the stress is smaller, the generation of warping is prevented, and the yield of epitaxial wafer products is improved.
The invention has the beneficial effects that: 1. firstly forming a low-temperature AlN buffer layer and a high-temperature AlN buffer layer on a substrate, wherein the two buffer layers can relieve stress generated by lattice mismatch between an upper GaN layer and the substrate, then firstly forming a loose AlGaN layer on the high-temperature AlN buffer layer to further buffer the stress, the loose AlGaN layer is formed after indium is separated out from the AlInGaN layer, and after the loose AlGaN layer is formed, because the separation of the indium easily affects the structure of a device, blowing the liquid indium on the surface of the loose AlGaN layer by using nitrogen to remove the liquid indium on the surface;
2. the aluminum gradient layer is formed by raising the temperature of the loose AlGaN layer, so that the crystallization quality of the upper layer structure can be improved, and more crystallization defects caused by the loose layer can be prevented;
3. after the aluminum gradient layer, the forming conditions are kept unchanged, the gallium nitride transition layer is formed, the gallium nitride transition layer formed under high temperature and high pressure has good crystallization quality, the crystallization quality of the epitaxial layer can be improved when the gallium nitride epitaxial layer is formed above, and due to the stress relief of the two buffer layers and the loose AlGaN layer, the stress of the epitaxial wafer can be well reduced, and the epitaxial wafer is prevented from warping.
The above-mentioned embodiments are only for illustrating the technical idea and features of the present application, and the purpose of the present application is to enable those skilled in the art to understand the content of the present application and implement the present application, and not to limit the protection scope of the present application. All equivalent changes and modifications made according to the spirit of the present application are intended to be covered by the scope of the present application.

Claims (10)

1. A gallium nitride epitaxial wafer comprising a substrate, characterized in that: the substrate is sequentially provided with a low-temperature AlN buffer layer, a high-temperature AlN buffer layer, a loose AlGaN layer, an aluminum gradual change layer, a gallium nitride transition layer and a gallium nitride epitaxial layer.
2. A gallium nitride epitaxial wafer according to claim 1, wherein: the loose AlGaN layer is formed by depositing an AlInGaN layer on the high-temperature AlN buffer layer and then precipitating all indium.
3. A gallium nitride epitaxial wafer according to claim 2, wherein: after the loose AlGaN layer is formed, the loose AlGaN layer is purged with nitrogen gas to remove all indium precipitated from the AlInGaN layer.
4. A gallium nitride epitaxial wafer according to claim 2, wherein: the substrate comprises a sapphire substrate; the thickness of the low-temperature AlN buffer layer is 10-15nm, and the forming temperature is 500-650 ℃; the thickness of the high-temperature AlN buffer layer is 40-55nm, and the forming temperature is 800-1100 ℃; the thickness of the AlInGaN layer is 100-300nm; the thickness of the aluminum gradient layer is 80-150nm; the thickness of the gallium nitride transition layer is 50-100nm.
5. A gallium nitride epitaxial wafer according to any one of claims 1 to 4, wherein: the gallium epitaxial layer consists of a first gallium nitride epitaxial layer and a second gallium nitride epitaxial layer, the total thickness of the gallium epitaxial layer is 1.5-2 microns, and the thickness of the first gallium nitride epitaxial layer is 100-180nm.
6. A preparation method of a gallium nitride epitaxial wafer is characterized by comprising the following steps: depositing a low-temperature AlN buffer layer, a high-temperature AlN buffer layer, a loose AlGaN layer, an aluminum gradual change layer, a gallium nitride transition layer and a gallium nitride epitaxial layer on the substrate in sequence.
7. A method for producing a gallium nitride epitaxial wafer according to claim 6, wherein: the preparation method comprises the following steps: the method comprises the steps that a low-temperature AlN buffer layer, a high-temperature AlN buffer layer and an AlInGaN layer are sequentially arranged on a substrate, indium in the AlInGaN layer is completely separated out to form a loose AlGaN layer, and an aluminum gradient layer, a gallium nitride transition layer and a gallium nitride epitaxial layer are sequentially deposited on the loose AlGaN layer.
8. A method for producing a gallium nitride epitaxial wafer according to claim 6, wherein: the preparation method comprises the following steps:
step S1: placing a substrate into a reaction chamber;
step S2: introducing an aluminum source and a nitrogen source into the reaction chamber, controlling the temperature in the reaction chamber to be a first temperature, and forming a low-temperature AlN buffer layer on the substrate;
and step S3: increasing the temperature in the reaction chamber to a second temperature, and continuously introducing an aluminum source and a nitrogen source to form a high-temperature AlN buffer layer on the low-temperature AlN buffer layer; the second temperature is greater than the first temperature;
and step S4: keeping introducing an aluminum source and a nitrogen source, introducing an indium source and a gallium source into the reaction chamber, and forming an AlInGaN layer on the high-temperature AlN buffer layer; then stopping introducing an aluminum source, a nitrogen source, an indium source and a gallium source at the same time, forming a loose AlGaN layer after indium in the AlInGaN layer is completely separated out, and purging the surface of the loose AlGaN layer by using nitrogen to remove the indium completely separated out from the AlInGaN layer;
step S5: controlling the pressure and the temperature in the reaction chamber to be unchanged, reducing the introduction of an aluminum source, and forming an aluminum gradient layer on the surface of the loose AlGaN layer;
step S6: stopping introducing an aluminum source, and forming a gallium nitride transition layer on the surface of the aluminum gradual change layer;
step S7: and forming a gallium nitride epitaxial layer on the gallium nitride transition layer.
9. A method for preparing a gallium nitride epitaxial wafer according to claim 6, wherein: the gallium nitride epitaxial layer includes: a first gallium nitride epitaxial layer and a second gallium nitride epitaxial layer; the temperature and the pressure in the reaction chamber in the growth stage of the first gallium nitride epitaxial layer are both higher than the temperature and the pressure in the reaction chamber in the growth stage of the second gallium nitride epitaxial layer, but the growth speed of gallium nitride in the growth stage of the first gallium nitride epitaxial layer is lower than the growth speed of gallium nitride in the growth stage of the second gallium nitride epitaxial layer.
10. A method for producing a gallium nitride epitaxial wafer according to claim 8, wherein:
step S2: the nitrogen source is ammonia gas, the aluminum source is trimethyl aluminum, the first temperature is 500-650 ℃, and the thickness of the formed low-temperature AlN buffer layer is 10-15nm;
and step S3: the first temperature is 800-1100 ℃, and the thickness of the formed high-temperature AlN buffer layer is 40-55nm;
and step S4: the gallium source is trimethyl gallium, the indium source is trimethyl indium, the pressure in the reaction chamber is 150-200mbar, the temperature is 1050-1100 ℃, and simultaneously 30-60S of introducing the aluminum source, the nitrogen source, the indium source and the gallium source is suspended;
controlling the introduction of nitrogen and the direction of the nitrogen, blowing the droplet indium from the surface of the AlInGaN layer, and collecting the blown droplet indium in a recovery device.
CN202111364861.4A 2021-11-17 2021-11-17 Gallium nitride epitaxial wafer and preparation method thereof Pending CN115312584A (en)

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