Van der Waals epitaxy method of high-quality AlGaN material on amorphous substrateTechnical Field
The invention belongs to the technical field of semiconductors, and particularly relates to a van der Waals epitaxial method of a high-quality AlGaN material on an amorphous substrate.
Background
In the field of optoelectronic devices, alGaN materials are widely applied because the forbidden bandwidth is adjustable from 3.4eV to 6.2eV and the coverage wavelength range is large. The high Al component AlGaN material has the advantages of direct band gap, large forbidden band width, high breakdown voltage, high chemical stability, high thermal stability and the like, is suitable for high-voltage and high-power devices, high-speed and high-frequency devices and ultraviolet light electric devices, and has great application potential in the fields of integrated circuit lithography, ultraviolet light curing, solar blind ultraviolet detection, sterilization, disinfection, health care and the like. There are many methods for preparing AlGaN materials, such as metal organic vapor deposition (MOCVD), molecular Beam Epitaxy (MBE), physical Vapor Deposition (PVD), physical Vapor Transport (PVT), and the like. MOCVD is the mainstream method of current scientific research and industrial manufacture by comprehensively considering growth cost, epitaxial time and material quality. However, when AlGaN materials, particularly high Al component materials, are grown, the existing MOCVD epitaxy process for GaN growth is not effective. Because of the difficulty in material growth, it is difficult to use a homogeneous substrate for epitaxy, and lattice mismatch and thermal mismatch existing in heteroepitaxy make the stress of an epitaxial layer not be released effectively, so that many defects exist in the initial stage of epitaxy, and a high-quality film cannot be grown. Compared with Ga atoms, al atoms are more difficult to migrate in the growth process, island growth is easy to occur on the surface of a sample, and the flatness of a grown film is affected. Along with the improvement of the Al component, the crystal quality is obviously reduced, and the epitaxial layer with high Al component is easy to crack and has limited thickness. In addition, residual stress in the material also affects the material energy band structure, so that the movement of a luminescent peak and an absorption peak of the device is caused, dislocation defects in the material are easy to generate non-radiative recombination, leakage current and other problems, and the performance of the device is also affected. Material quality issues have greatly limited the application of AlGaN-based optoelectronic devices.
The van der Waals epitaxial growth method utilizes a novel two-dimensional material as an insertion layer to epitaxially grow a nitride material, and opens up a new epitaxial path for AlGaN-based semiconductor materials. The intra-layer structure of the two-dimensional material is a strong bond lattice formed by covalent bonds or ionic bonds, and weak van der Waals force interactions are formed between the two-dimensional material layers, between the two-dimensional material and the substrate and between the two-dimensional material and the epitaxial layer. The substrate and the interface defect dislocation are difficult to enter the epitaxial layer, the lattice mismatch and the thermal mismatch degree between the epitaxial layer and the substrate are obviously reduced, the residual stress in the epitaxial layer is greatly reduced, and the quality of the epitaxial growth material is improved.
In addition to improving material quality, van der Waals epitaxy can also be used to achieve epitaxial growth of special structures, such as growth of two-dimensional AlGaN materials. On a van der Waals substrate formed by a two-dimensional material and a substrate easy to bond, the van der Waals substrate is subjected to hydrogenation treatment to passivate the two-dimensional material and form a conveying channel, and a source for growing AlGaN material is introduced subsequently.
There is still much room for development in the research of van der waals epitaxial growth of nitrides. At present, the van der Waals epitaxy research of nitride mainly has two directions, namely firstly, utilizing a two-dimensional material to shield the influence of a substrate on an epitaxial layer, realizing narrow van der Waals epitaxy only by virtue of van der Waals force between the two-dimensional material and an epitaxial layer, and secondly, utilizing a van der Waals substrate formed by the two-dimensional material and a substrate together, and realizing generalized van der Waals epitaxy by virtue of the combined action of the two-dimensional material, the van der Waals force between the epitaxial layer and the strong bond between the substrate and the epitaxial layer. The van der Waals epitaxy of the nitride is realized by completely utilizing the van der Waals interaction between the two-dimensional material and the epitaxial layer, the epitaxial growth process is regulated and controlled by the two-dimensional material, and even the crystallization quality of the substrate possibly does not need to be considered, so that the amorphous substrate is expected to realize high-quality epitaxy, but the two-dimensional material with extremely high quality is required, the growth and transfer requirements on the two-dimensional material are extremely high, and the process of industrial application is difficult, while the van der Waals epitaxy realized by utilizing the composite regulation and control effect of the two-dimensional material and the substrate in the van der Waals substrate can better regulate and control the nucleation growth process of the epitaxial layer, but the quality of the substrate and the two-dimensional material greatly influence the quality of the epitaxial layer, so that the van der Waals epitaxy on the single crystal substrate is mostly used.
Therefore, research on a van der Waals epitaxial method of high-quality AlGaN materials on an amorphous substrate is urgently needed, the difficulties of random orientation and nucleation of epitaxial growth on the amorphous substrate are overcome, meanwhile, the stress born by an epitaxial layer can be reduced, dislocation density is reduced, and the growth of the high-quality AlGaN materials is realized.
Disclosure of Invention
Therefore, in order to solve the technical problems, the invention provides a van der Waals epitaxy method of a high-quality AlGaN material on an amorphous substrate, which utilizes a double-layer two-dimensional material to grow a two-dimensional AlGaN material prefabricated layer on the amorphous substrate, and realizes the epitaxy method of the homogeneous van der Waals epitaxy high-quality AlGaN material on the basis, and the difficulties of random orientation and nucleation of the epitaxy growth on the amorphous substrate are overcome through a two-step growth process, and meanwhile, the stress born by an epitaxial layer is greatly reduced and the dislocation density is reduced through the two-layer two-dimensional material.
In order to achieve the above object, the present invention provides a van der waals epitaxial method of high quality AlGaN material on an amorphous substrate, comprising the steps of:
transferring a first two-dimensional material layer on an amorphous substrate;
processing the first two-dimensional material layer to improve the epitaxial condition of the amorphous substrate and provide adsorption atom bonding sites;
Transferring a second two-dimensional material layer on the treated first two-dimensional material layer, and carrying out hydrogenation passivation treatment on the second two-dimensional material layer to inhibit three-dimensional growth of AlGaN materials and provide an atomic transport channel for growth of the following two-dimensional AlGaN materials;
Providing a metal source and an N source, and performing van der Waals epitaxial growth on a two-dimensional AlGaN material to form a two-dimensional AlGaN material prefabricated layer between the first two-dimensional material layer and the second two-dimensional material layer;
and growing the AlGaN material by homovan der Waals epitaxy, and growing by adopting a two-step method, wherein a nucleation layer is grown at a low temperature, and then growing at a high temperature, so as to form a three-dimensional AlGaN material film on the second two-dimensional material layer.
Preferably, the amorphous substrate is made of quartz.
Preferably, the amorphous substrate is made of polycrystalline material which is difficult to epitaxially grow a single crystal thin film, and the polycrystalline material comprises mica and ceramic.
Preferably, the first two-dimensional material layer is an h-BN film or a transition metal dichalcogenide material film.
Preferably, the second two-dimensional material layer is a graphene film.
Preferably, the method for transferring the first two-dimensional material layer and the second two-dimensional material layer is wet transfer or dry transfer, wherein the solution used in the wet transfer does not react with the amorphous substrate.
Preferably, the treatment method for the first two-dimensional material layer is chemical solution treatment, plasma treatment, or high-temperature reaction treatment in a gas atmosphere.
Preferably, when the first two-dimensional material layer is an h-BN film, HCl solution and deionized water are adopted to treat the h-BN film respectively, so that h-BN surface dangling bonds are increased.
Preferably, the hydrogenation passivation treatment is specifically implemented by introducing H2 for passivating the second two-dimensional material layer and bonds existing between the second two-dimensional material layer and the first two-dimensional material layer, and simultaneously forming a channel at the defect of the first two-dimensional material to provide an atom transport channel for the growth of the following two-dimensional AlGaN material.
Preferably, the preparation methods of the two-dimensional AlGaN material prefabricated layer and the three-dimensional AlGaN material film are MOCVD or MBE.
The invention adopts the technical proposal has the advantages that:
According to the van der Waals epitaxy method of the high-quality AlGaN material on the amorphous substrate, nucleation sites are provided by utilizing the two-dimensional material, a two-dimensional AlGaN material prefabricated layer grows between a first two-dimensional material layer and a second two-dimensional material layer, the growth thickness is low, a high-quality buffer layer is obtained in a short time, a van der Waals substrate is constructed, conditions are provided for the subsequent three-dimensional growth of the AlGaN material, then the van der Waals substrate formed by the two-dimensional AlGaN material prefabricated layer and the second two-dimensional material layer is utilized to realize homogeneous van der Waals epitaxy, and potential fluctuation of the two-dimensional AlGaN prefabricated layer penetrates through the second two-dimensional material layer to play roles in attracting atomic nucleation and regulating atomic arrangement. The method of the invention adopts two layers of two-dimensional materials to further relieve the influence of the amorphous substrate on the epitaxial layer, greatly reduces stress and dislocation, improves crystal quality, is expected to obtain the material close to single crystal AlGaN, greatly improves the growth quality of the AlGaN material on the amorphous substrate, provides help for large-area application of AlGaN-based photoelectric devices, and has the advantages of simple process, obvious effect, wide application prospect and the like.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic flow chart of a Van der Waals epitaxy method of high quality AlGaN material on an amorphous substrate of the invention;
fig. 2 is a schematic structural diagram of the epitaxial wafer obtained in fig. 1;
the figure shows that the substrate is 1-amorphous, the first two-dimensional material layer is 2-two-dimensional material layer is 3-two-dimensional material layer, the prefabricated layer of 4-two-dimensional AlGaN material is 4-two-dimensional AlGaN material, and the three-dimensional AlGaN material film is 5-three-dimensional.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
As shown in fig. 1 and 2, the present invention provides a van der waals epitaxial method of high quality AlGaN material on an amorphous substrate, comprising the steps of:
transferring a first two-dimensional material layer 2 on an amorphous substrate 1;
Processing the first two-dimensional material layer 2 to improve the epitaxial condition of the amorphous substrate 1 and provide adsorption atom bonding sites;
Transferring a second two-dimensional material layer 3 on the treated first two-dimensional material layer 2, and carrying out hydrogenation passivation treatment on the second two-dimensional material layer 3 to inhibit three-dimensional growth of AlGaN materials and provide an atomic transport channel for growth of the following two-dimensional AlGaN materials;
Providing a metal source and an N source, and performing van der Waals epitaxial growth on a two-dimensional AlGaN material to form a two-dimensional AlGaN material prefabricated layer 4 between the first two-dimensional material layer 2 and the second two-dimensional material layer 3;
The homovan der Waals epitaxial growth AlGaN material is grown by a two-step method, a nucleation layer is grown at a low temperature, and then a three-dimensional AlGaN material film 5 is formed on the second two-dimensional material layer 3.
The principle of the van der Waals epitaxy method of the high-quality AlGaN material on the amorphous substrate provided by the invention is that the two-dimensional material layers are connected by the weakly coupled van der Waals force, so that the van der Waals epitaxy method is easy to strip, transfer and combine, not only can provide nucleation sites on the amorphous substrate, but also can realize the van der Waals epitaxy, and grow the two-dimensional and three-dimensional AlGaN material. In addition, in the process of realizing the van der Waals epitaxy on the van der Waals substrate, the low-temperature-high-temperature two-step method adopted to grow the AlGaN material can obviously improve the quality of the van der Waals epitaxy.
The amorphous substrate 1 may be made of quartz, and the amorphous substrate 1 may be made of polycrystalline material which is difficult to epitaxially grow a single crystal thin film, and the polycrystalline material includes mica and ceramic. The amorphous substrate 1 has stable material property and is suitable for transferring two-dimensional materials.
The first two-dimensional material layer 2 may be an h-BN film or a transition metal dichalcogenide material film, etc. The second two-dimensional material layer 3 is a graphene film, and the nucleation capability of the hydrogenated and passivated AlGaN material is weaker than that of the first two-dimensional material layer 2. For example, when the first two-dimensional material layer 2 is an h-BN film and the second two-dimensional material layer 3 is a graphene film, both the h-BN film and the graphene film are two-dimensional materials synthesized by CVD or the like. The h-BN can regulate and control the epitaxial growth of the two-dimensional AlGaN material, reduce the influence of the amorphous substrate 1 on an epitaxial layer and reduce the stress and dislocation density of the epitaxial layer, and the graphene is used for realizing the growth of the two-dimensional AlGaN material and homoepitaxy of the AlGaN material, fully plays the advantages of van der Waals epitaxy, further reduces the stress and dislocation density of the epitaxial material and improves the quality of the material.
The method for transferring the first two-dimensional material layer 2 and the second two-dimensional material layer 3 is a wet transfer method or a dry transfer method, and the like, wherein the solution used in the wet transfer does not react with the amorphous substrate.
The treatment method for the first two-dimensional material layer 3 is chemical solution treatment, plasma treatment or high-temperature reaction treatment in a gas atmosphere. For example, when the first two-dimensional material layer 2 is an h-BN film and the second two-dimensional material layer 3 is a graphene film, the h-BN film is transferred onto the amorphous substrate 1, and after the transfer is completed, the h-BN film is treated by HCl solution and deionized water, so that h-BN surface dangling bonds are increased, and nucleation sites are provided for the growth of the two-dimensional AlGaN material. After the treatment is completed, transferring the graphene film onto the h-BN film, and completing the construction of the Van der Waals substrate. For the amorphous substrate 1, the surface of the amorphous substrate 1 lacks adsorption sites forming a stable structure, even if nucleation islands are formed, the orientation is random, and by introducing h-BN treated by HCl solution, a large number of uniform nucleation sites are provided for Van der Waals epitaxy, and the orientation is relatively consistent, so that the nucleation and growth of an epitaxial layer are facilitated. Meanwhile, a two-dimensional AlGaN material prefabricated layer grows on the h-BN, the growth thickness is not high, a high-quality buffer layer is obtained in a short time, and conditions are provided for the subsequent three-dimensional growth of the AlGaN material.
The hydrogenation passivation treatment is specifically that H2 is introduced to passivate the second two-dimensional material layer 3 and bonds existing between the second two-dimensional material layer 3 and the first two-dimensional material layer 2, and meanwhile, a channel is formed at the defect of the first two-dimensional material to provide an atom transport channel for the growth of the following two-dimensional AlGaN material. For example, when the first two-dimensional material layer 2 is an h-BN film and the second two-dimensional material layer 3 is a graphene film, the hydrogenation treatment of the graphene film can passivate bonds possibly existing at the defect positions between graphene and h-BN, and meanwhile, channels are formed at the defect positions of graphene, so that an atom transport channel is provided for the subsequent growth of two-dimensional AlGaN materials. In addition, graphene located above h-BN plays a protective role for h-BN.
The preparation methods of the two-dimensional AlGaN material prefabricated layer 4 and the three-dimensional AlGaN material film 5 are MOCVD or MBE. For example, when the first two-dimensional material layer 2 is an h-BN film and the second two-dimensional material layer 3 is a graphene film, a large amount of uniform N-O bond site two-dimensional AlGaN materials introduced by HCl solution treatment of the h-BN film grow to provide stable bond sites. And (3) continuously growing a three-dimensional AlGaN material film by MOCVD or MBE, adopting a two-step growth method, firstly utilizing the potential fluctuation distribution of the two-dimensional AlGaN material penetrating through the graphene and the suspension bond attraction atom nucleation at the defect position of the graphene to form a nucleation layer, changing the growth condition, increasing the temperature to transversely grow and combine to form a continuous film, then increasing the growth temperature to realize the continuous growth of the epitaxial layer, and finally obtaining the high-quality three-dimensional AlGaN material film.
Example 1
A high-quality three-dimensional AlGaN material film on an amorphous substrate is prepared by the following steps:
After cutting and polishing the quartz substrate, sequentially ultrasonically cleaning the quartz substrate in ultrapure water, acetone, isopropanol and deionized water for 10 minutes, and drying the quartz substrate by using N2 after cleaning;
Transferring a two-dimensional material H-BN film onto a quartz substrate by utilizing wet transfer, spin-coating PMMA polymer material on the surface of the H-BN film on a copper substrate, soaking the substrate/H-BN film/PMMA in H2O2 and HCl mixed diluent after solidification, corroding for 1H, carefully transferring the Cu to the quartz substrate after Cu corrosion is finished, and sequentially soaking in isopropanol, acetone, ethanol and deionized water for 10 minutes to remove PMMA;
after the transfer is finished, soaking the h-BN film for 10 minutes by using an HCl solution and deionized water respectively, increasing h-BN surface dangling bonds, providing N-O bonds for the growth of the two-dimensional AlGaN material, and improving nucleation density;
Transferring the graphene film onto the h-BN film by a wet method, wherein the transfer method is the same as that of the h-BN film;
The hydrogenation treatment was carried out for 30 minutes by means of MOCVD equipment at 700℃with 80sccm H2. At 950 ℃, simultaneously introducing TMAL 120sccm and TMGa 120sccm for 30s, then introducing NH3 sccm for 30s, and repeating the process until a multi-layer two-dimensional AlGaN material grows;
The two-step growth is carried out by utilizing MOCVD equipment, firstly introducing NH3 3600sccm at 700 ℃ for nitriding treatment for 150s, then introducing NH3 3600sccm and TMAL 80sccm for growing a low-temperature nucleation layer for 200s, then introducing TMAL 150sccm, TMGa 150sccm and NH3 800sccm for growing a high-temperature AlGaN layer at 1240 ℃ for continuous growth until a three-dimensional AlGaN material film with the target thickness is obtained.
The synthesis process of the H-BN film comprises the steps of synthesizing the H-BN by a CVD method, annealing a copper substrate for 2 hours under the condition of introducing 200sccm Ar at 1050 ℃ in a dual-temperature-zone LPCVD device, heating precursor ammonia borane to 110 ℃, maintaining the substrate temperature at 1050 ℃, and introducing 150sccm Ar and 50sccm H2 to grow the H-BN film.
The graphene film is synthesized by CVD method, copper substrate is placed in LPCVD equipment, 500sccm Ar and 200sccm H2、20sccm CH4 are introduced at 1050 deg.C for 1H growth.
Example 2
A high-quality three-dimensional AlGaN material film on an amorphous substrate is different from the high-quality three-dimensional AlGaN material film in example 1 in that the h-BN film and the graphene film are both transferred by a dry transfer method, namely, the two-dimensional material h-BN film is transferred to a quartz substrate by dry transfer, a PDMS film is stuck to the surface of the h-BN film, no bubbles are generated between the PDMS film and the h-BN film, a sample deionized water is soaked for 20 minutes, the PDMS film and a copper substrate are slowly separated, after separation, the PDMS/h-BN film is carefully transferred to the quartz substrate, no bubbles are generated again, the sample on the quartz substrate is heated at 90 ℃ for 60 minutes to reduce the viscosity between the PDMS and the h-BN film, and finally, the PDMS and the h-BN film are separated, and the h-BN film is obtained on the quartz substrate. Other procedures are the same as in embodiment 1, and a detailed description thereof is omitted.
The invention adopts the technical proposal has the advantages that:
According to the van der Waals epitaxy method of the high-quality AlGaN material on the amorphous substrate, nucleation sites are provided by utilizing the two-dimensional material, a two-dimensional AlGaN material prefabricated layer grows between a first two-dimensional material layer and a second two-dimensional material layer, the growth thickness is low, a high-quality buffer layer is obtained in a short time, a van der Waals substrate is constructed, conditions are provided for the subsequent three-dimensional growth of the AlGaN material, then the van der Waals substrate formed by the two-dimensional AlGaN material prefabricated layer and the second two-dimensional material layer is utilized to realize homogeneous van der Waals epitaxy, and potential fluctuation of the two-dimensional AlGaN prefabricated layer penetrates through the second two-dimensional material layer to play roles in attracting atomic nucleation and regulating atomic arrangement. The method of the invention adopts two layers of two-dimensional materials to further relieve the influence of the amorphous substrate on the epitaxial layer, greatly reduces stress and dislocation, improves crystal quality, is expected to obtain the material close to single crystal AlGaN, greatly improves the growth quality of the AlGaN material on the amorphous substrate, provides help for large-area application of AlGaN-based photoelectric devices, and has the advantages of simple process, obvious effect, wide application prospect and the like.
It should be noted that the above-mentioned embodiments are merely for illustrating the technical solution of the present invention, and not for limiting the same, and although the present invention has been described in detail with reference to the above-mentioned embodiments, it should be understood by those skilled in the art that the technical solution described in the above-mentioned embodiments may be modified or some or all of the technical features may be equivalently replaced, and these modifications or substitutions do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the present invention.