Diluted magnetic semiconductor thin film material epitaxial structure and preparation method

Abstract

The application discloses a kind of dilute magnetic semiconductor thin film material epitaxial structure and preparation method, epitaxial structure includes by lower to upper sequentially arranged: p-GaAs substrate, p-ZnTe thin film layer, ZnTe stop layer, (Zn, Cr)Te magnetic layer, AlN insulating layer, Au voltage extraction layer, the doping element of the p-ZnTe thin film layer is N atom.The ZnTe stop layer is grown on p-ZnTe thin film layer and (Zn, Cr)Te magnetic layer, can prevent N atom in p-ZnTe thin film layer diffusion to (Zn, Cr)Te magnetic layer, to change the magnetism characteristic of containing (Zn, Cr)Te magnetic layer, and further improve the effective operating temperature of device.

Description

Technical Field

[0001] This invention relates to the field of transistor fabrication, and more particularly to an epitaxial structure and preparation method of a dilute magnetic semiconductor thin film material. Background Technology

[0002] With the advancement of electronic and network technologies, electronic devices and systems are developing at an increasingly rapid pace, with ever-increasing integration levels. For example, switching transistors made from silicon-based semiconductors can define "0" and "1" through changes in current and voltage, thereby enabling logical operations. As electronic engineering progresses, the feature linewidth of logic operation chips such as CPUs and GPUs has shrunk to 3nm, gradually approaching production limits. Future device development will be constrained by the limits of physical theory, thus necessitating further development of electronic engineering. Meanwhile, the recording, storage, and reading / writing of information utilize magnetic properties. A typical application is the hard disk drive (HDD), which leverages the electron spin properties of magnetic materials for information storage and retrieval.

[0003] On the other hand, with the discovery of giant magnetoresistance and tunneling magnetoresistance, some researchers believe that information can be stored using the electron spin of magnetic materials, and information can be transmitted and processed using the movement of charges, thus improving the efficiency of information storage, transmission, and processing. Currently, the main carriers for information storage are metals or insulators, while semiconductors are used for information transmission and processing. Therefore, to achieve information storage, transmission, and processing on a single logical function unit device, it is necessary to add magnetic elements / atoms to the semiconductor material, such as d-block elements represented by Co, Mn, and Fe, or f-block elements represented by La and Ce. This is also known as dilute magnetic semiconductors. The most extensive research on this type of semiconductor focuses on the magnetic, optical, and electrical properties of the material itself after the addition of d-block elements. This involves the element addition ratio, growth method, crystallization evaluation, and microscale processing.

[0004] In research on dilute magnetic semiconductors, representative examples include (In,Mn)As and (Ga,Mn)As group III-V semiconductor materials. These materials exhibit both magnetic and electrical properties at low temperatures, and have been studied in practice. First-principles calculations reveal that these materials possess only electrical properties at room temperature or higher, while their magnetic properties disappear; that is, their ferromagnetic Curie temperature is below room temperature. First-principles calculations show that by replacing some of the Zn and Cr elements in ZnSe or ZnTe, the material retains both magnetic and electrical properties at room temperature or higher. Some existing techniques have found that when the Cr content in (Zn,Cr)Te is 20%, the ferromagnetic Curie temperature can reach 275K at room temperature. However, while the material exhibits ferromagnetic properties, it has become metallic and lost its semiconductor properties, making it unsuitable for fabricating corresponding electron spin devices. When the Cr content is 10%, the ferromagnetic Curie temperature is 130K, and the material exhibits semiconductor properties, making it suitable for fabricating electron spin devices. Other existing technologies have used this material for epitaxial design and device fabrication. However, the resulting devices can only be magnetized using an external electric field at a temperature of 10K, and their operating temperature is far below room temperature. Therefore, it is necessary to improve the epitaxial structure or the device fabrication method to increase the device's operating temperature. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an epitaxial structure and preparation method for a dilute magnetic semiconductor thin film material.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] In a first aspect, the present invention provides an epitaxial structure of a rare magnetic semiconductor thin film material, comprising, from bottom to top, a p-GaAs substrate, a p-ZnTe thin film layer, a ZnTe blocking layer, a (Zn,Cr)Te magnetic layer, an AlN insulating layer, and an Au voltage lead-out layer, wherein the doping element of the p-ZnTe thin film layer is N atoms.

[0008] Furthermore, the thickness of the p-ZnTe thin film layer is 340-380 nm; the thickness of the ZnTe blocking layer is 6-12 nm; the thickness of the (Zn,Cr)Te magnetic layer is 8-12 nm; the thickness of the AlN insulating layer is 35-45 nm; and the thickness of the Au voltage lead-out layer is 25-35 nm.

[0009] Furthermore, the thickness of the p-GaAs substrate is 657 μm.

[0010] Furthermore, the N atom content of the p-ZnTe thin film layer is 10. 19 cm-3 .

[0011] A second aspect of the present invention provides a method for preparing an epitaxial structure of a dilute magnetic semiconductor thin film material, comprising the following steps:

[0012] A p-ZnTe thin film layer, a ZnTe blocking layer, a (Zn,Cr)Te magnetic layer, an AlN insulating layer, and an Au voltage lead-out layer are sequentially grown on a p-GaAs substrate, wherein the doping element of the p-ZnTe thin film layer is N atoms.

[0013] Furthermore, the method further includes one or more of the following steps:

[0014] Before growth, the p-GaAs substrate is cleaned and dehydrated;

[0015] Before growth, the surface oxide of the p-GaAs substrate is removed.

[0016] Further, the removal of surface oxides from the p-GaAs substrate includes:

[0017] The p-GaAs substrate is heated to a first temperature, which causes the surface oxides of the p-GaAs substrate to be removed and the As atoms of the p-GaAs substrate to evaporate from the surface.

[0018] Heating is used to compensate for As atoms by growing Te atom sources including p-ZnTe thin film layers, ZnTe blocking layers, and (Zn,Cr)Te magnetic layers.

[0019] Furthermore, the growth of the p-ZnTe thin film layer includes the following sub-steps:

[0020] The temperature of the p-GaAs substrate is set to the second temperature. The Zn and Te atomic sources are heated, and the molecular line intensities of Zn and Te are adjusted so that the Zn:Te molecular line intensity ratio reaches the first intensity ratio. N atom doping is performed by radio frequency discharge ion implantation. The first growth time is determined according to the growth rate and preset thickness under the corresponding conditions.

[0021] The growth of the ZnTe barrier layer includes the following sub-steps:

[0022] The temperature of the p-GaAs substrate is set to the third temperature. The Zn atom source and the Te atom source are heated. The molecular line intensities of Zn and Te are adjusted so that the molecular line intensity ratio of Zn:Te reaches the second intensity ratio. The second growth time is then determined according to the growth rate and preset thickness under the corresponding conditions.

[0023] The growth of the (Zn,Cr)Te magnetic layer includes the following sub-steps:

[0024] The temperature of the p-GaAs substrate is set to the fourth temperature. The Zn, Cr, and Te atomic sources are heated, and the molecular line intensities of Zn, Cr, and Te are adjusted so that the molecular line intensity ratio of Zn:Cr:Te reaches the third intensity ratio. The third growth time is then determined based on the growth rate and preset thickness under the corresponding conditions.

[0025] Furthermore, the second, third, and fourth temperatures are the same.

[0026] Furthermore, the growth of the AlN insulating layer includes the following sub-steps:

[0027] The Al atom source is heated to adjust the molecular line strength of Al, and N atoms are implanted using radio frequency discharge ion implantation; the fourth growth time is determined according to the growth rate and preset thickness under the corresponding conditions.

[0028] The growth of the Au voltage lead-out layer includes the following sub-steps:

[0029] The Au voltage lead-out layer was grown using an electron beam evaporation apparatus; the fifth time was used to deposit the layer according to the growth rate and preset thickness under the corresponding conditions.

[0030] The beneficial effects of this invention are:

[0031] (1) In an exemplary embodiment of the present invention, a ZnTe blocking layer is grown on the p-ZnTe thin film layer and the (Zn,Cr)Te magnetic layer to prevent N atoms in the p-ZnTe thin film layer from diffusing to the (Zn,Cr)Te magnetic layer, thereby changing the magnetic properties of the (Zn,Cr)Te magnetic layer and further improving the effective operating temperature of the device (100K).

[0032] (2) In another exemplary embodiment of the present invention, two pretreatment steps are disclosed before growing an epitaxial structure: one is to clean and dehydrate the p-GaAs substrate before growth, that is, to clean the surface of the p-GaAs substrate; the other is to remove the surface oxide of the p-GaAs substrate before growth, so that the quality of the epitaxial structure grown subsequently is better and will not affect the use process.

[0033] (3) In another exemplary embodiment of the present invention, the specific method for removing the surface oxide of the p-GaAs substrate is to heat the p-GaAs substrate to 560°C (first temperature) and hold it for 5 minutes, under which the oxide can be completely removed; after the surface oxide is removed, the As atoms are compensated using a Te atom source.

[0034] By employing the method described in this exemplary embodiment, the goal of removing surface oxides can be achieved, and the Te atom source can be used to compensate for the As atoms evaporated from the p-GaAs substrate surface, reducing the impact of p-GaAs substrate surface lattice defects on the quality of subsequent products. Furthermore, since the Te atom source is present in subsequent fabrication steps (required for growing p-ZnTe thin films, ZnTe barrier layers, and (Zn,Cr)Te magnetic layers), no additional equipment is needed to achieve this goal, thus reducing costs.

[0035] Furthermore, when using the exemplary embodiment of this invention, the pretreatment is preferably performed by first cleaning and dehydrating before removing surface oxides.

[0036] (4) In another exemplary embodiment of the present invention, a specific method for preparing the p-ZnTe thin film layer, the (Zn,Cr)Te magnetic layer, and the ZnTe barrier layer is disclosed. Furthermore, in a preferred exemplary embodiment, the second, third, and fourth temperatures are the same, all being 300°C as described above. Setting the same temperature for the p-GaAs substrate in multiple growth steps eliminates the need for unnecessary adjustments throughout the process.

[0037] (5) In another exemplary embodiment of the present invention, a specific method for preparing the AlN insulating layer and the Au voltage lead-out layer is disclosed. Furthermore, in a preferred exemplary embodiment, compared to the prior art which uses an AlO insulating layer, this exemplary embodiment uses an AlN insulating layer, which allows the use of the radio frequency discharge ion implantation equipment used in the N atom doping process in the growth of the p-ZnTe thin film layer directly, without the need for other equipment, thus reducing costs. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the epitaxial structure of the prior art;

[0039] Figure 2 This is a schematic diagram of an epitaxial structure of a dilute magnetic semiconductor thin film material provided in an exemplary embodiment of the present invention;

[0040] Figure 3 This is a flowchart illustrating a method for preparing an epitaxial structure of a dilute magnetic semiconductor thin film material, as provided in an exemplary embodiment of the present invention.

[0041] Figure 4 This is a graph illustrating the magnetic properties of an epitaxial structure with ZnTe blocking layers of different thicknesses, tested using a superconducting quantum interference device (SQUID) at 2K temperature, as provided in an exemplary embodiment of the present invention.

[0042] Figure 5This is a schematic diagram of the X-ray absorption fine structure curves and dynamic diameter distribution function curves of ZnTe blocking layers of different thicknesses provided in an exemplary embodiment of the present invention;

[0043] Figure 6 This is a schematic diagram illustrating the test results of voltage-controlled magnetic properties of an epitaxial structure with a 12nm thick ZnTe blocking layer at 100K temperature, provided in an exemplary embodiment of the invention.

[0044] Figure 7 This is a schematic diagram of an apparatus for fabricating an epitaxial structure of a rare magnetic semiconductor thin film material, provided in an exemplary embodiment of the present invention. Detailed Implementation

[0045] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] In the description of this invention, it should be noted that the directions or positional relationships indicated by terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0047] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0048] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0049] In existing technologies, epitaxial structures such as Figure 1 As shown, p-ZnTe thin films are sequentially grown on a p-GaAs substrate. 90％ Cr 10％The effective operating temperature of the electron spin device fabricated based on the Te magnetic layer / AlO insulating layer / Au voltage lead-out layer is 10K, which is much lower than that of (Zn) magnetic layer / AlO insulating layer / Au voltage lead-out layer. 90％ Cr 10％ The ferromagnetic Curie temperature of Te is 130K, which makes its practical application performance poor.

[0050] See Figure 2 , Figure 2 The diagram illustrates an epitaxial structure of a rare magnetic semiconductor thin film material provided in an exemplary embodiment of the present invention, comprising, from bottom to top: a p-GaAs substrate, a p-ZnTe thin film layer, a ZnTe blocking layer, a (Zn,Cr)Te magnetic layer, an AlN insulating layer, and an Au voltage lead-out layer, wherein the doping element of the p-ZnTe thin film layer is N atoms.

[0051] Specifically, in this exemplary embodiment, the p-ZnTe thin film layer serves to provide electrons to the (Zn,Cr)Te magnetic layer under the influence of an external electric field. This increases the number of electrons or holes in the (Zn,Cr)Te magnetic layer under the influence of the external electric field, allowing the (Zn,Cr)Te magnetic layer to change its magnetization with changes in the applied voltage. Therefore, it can be used in the fabrication of electron spin devices. One function of the (Zn,Cr)Te magnetic layer is as a space charge region, generating electrons or holes under the influence of an external electric field. Another function is to enable the thin film material to exhibit ferromagnetic properties under the influence of an external magnetic field. Growing an AlN insulating layer on the (Zn,Cr)Te magnetic layer provides a high-field-resistant insulating film, allowing the external voltage to be increased to ±10V. An Au voltage lead-out layer is grown on the AlN insulating layer, serving as the lead-out terminal for the applied voltage. The N atom is a p-type dopant.

[0052] Growing a ZnTe blocking layer on the p-ZnTe thin film and the (Zn,Cr)Te magnetic layer can prevent N atoms from diffusing from the p-ZnTe thin film to the (Zn,Cr)Te magnetic layer, thereby altering the magnetic properties of the (Zn,Cr)Te magnetic layer and further increasing the effective operating temperature of the device. This is because:

[0053] During the thin film growth process, nitrogen atoms are used as the dopant element when growing p-ZnTe thin films. When using existing techniques to directly grow (Zn,Cr)Te magnetic layers after the p-ZnTe thin film is completed, some nitrogen atoms diffuse from the p-ZnTe thin film into the (Zn,Cr)Te magnetic layer due to thermal motion. This results in localized Cr-N bonds, which, under the principle of electroneutrality, reduce the number of Cr 3d electrons in the (Zn,Cr)Te magnetic layer. This reduction in Cr 3d electrons weakens the metastable decomposition probability of Cr atoms, causing adjacent Cr atoms to move away from each other due to binding energy. This weakens the Cr-Cr doublet interaction, leading to a decrease in the ferromagnetic Curie temperature of the (Zn,Cr)Te magnetic layer.

[0054] In this exemplary embodiment, a ZnTe barrier layer is grown between the p-ZnTe thin film layer and the (Zn,Cr)Te magnetic layer, which effectively prevents N atoms from diffusing from the p-ZnTe thin film layer to the (Zn,Cr)Te magnetic layer. Therefore, compared with the epitaxial structure of the prior art, this exemplary embodiment allows the device to operate at a higher temperature.

[0055] It should be noted that the (Zn,Cr)Te magnetic layer can be made using existing (Zn) technology. 90％ Cr 10％ The Te ratio can be implemented, but other ratios can also be used, as long as they can achieve the purpose of this exemplary embodiment.

[0056] More preferably, in an exemplary embodiment, the thickness of the p-ZnTe thin film layer is 340-380 nm; the thickness of the ZnTe blocking layer is 6-12 nm; the thickness of the (Zn,Cr)Te magnetic layer is 8-12 nm; the thickness of the AlN insulating layer is 35-45 nm; and the thickness of the Au voltage lead-out layer is 25-35 nm.

[0057] More preferably, in an exemplary embodiment, the thickness of the p-GaAs substrate is 657 μm.

[0058] More preferably, in an exemplary embodiment, the N atom content of the p-ZnTe thin film layer is 10. 19 cm -3 .

[0059] Having the same inventive concept as the exemplary embodiments described above, another exemplary embodiment of the present invention provides a method for preparing an epitaxial structure of a dilute magnetic semiconductor thin film material, such as... Figure 3 As shown, it includes the following steps:

[0060] A p-ZnTe thin film layer, a ZnTe blocking layer, a (Zn,Cr)Te magnetic layer, an AlN insulating layer, and an Au voltage lead-out layer are sequentially grown on a p-GaAs substrate, wherein the doping element of the p-ZnTe thin film layer is N atoms.

[0061] Specifically, in this exemplary embodiment, the p-ZnTe thin film layer functions to provide electrons to the (Zn,Cr)Te magnetic layer under the influence of an external electric field. This increases the number of electrons or holes in the (Zn,Cr)Te magnetic layer under the influence of the external electric field, allowing the (Zn,Cr)Te magnetic layer to change its magnetization with changes in the applied voltage. Therefore, it can be used in the fabrication of electron spin devices. One function of the (Zn,Cr)Te magnetic layer is as a space charge region, generating electrons or holes under the influence of an external electric field. Another function is to allow the thin film material to exhibit ferromagnetic properties under the influence of an external magnetic field. Growing an AlN insulating layer on the (Zn,Cr)Te magnetic layer provides an insulating film layer that can withstand high electric fields, allowing the external voltage to be increased to ±10V. An Au voltage lead-out layer is grown on the AlN insulating layer as a lead-out terminal for the applied voltage.

[0062] Growing a ZnTe blocking layer on the p-ZnTe thin film and the (Zn,Cr)Te magnetic layer can prevent N atoms from diffusing from the p-ZnTe thin film to the (Zn,Cr)Te magnetic layer, thereby altering the magnetic properties of the (Zn,Cr)Te magnetic layer and further increasing the effective operating temperature of the device. This is because:

[0063] During the thin film growth process, nitrogen atoms are used as the dopant element when growing p-ZnTe thin films. When using existing techniques to directly grow (Zn,Cr)Te magnetic layers after the p-ZnTe thin film is completed, some nitrogen atoms diffuse from the p-ZnTe thin film into the (Zn,Cr)Te magnetic layer due to thermal motion. This results in localized Cr-N bonds, which, under the principle of electroneutrality, reduce the number of Cr 3d electrons in the (Zn,Cr)Te magnetic layer. This reduction in Cr 3d electrons weakens the metastable decomposition probability of Cr atoms, causing adjacent Cr atoms to move away from each other due to binding energy. This weakens the Cr-Cr doublet interaction, leading to a decrease in the ferromagnetic Curie temperature of the (Zn,Cr)Te magnetic layer.

[0064] In this exemplary embodiment, a ZnTe barrier layer is grown between the p-ZnTe thin film layer and the (Zn,Cr)Te magnetic layer, which effectively prevents N atoms from diffusing from the p-ZnTe thin film layer to the (Zn,Cr)Te magnetic layer. Therefore, compared with the epitaxial structure of the prior art, this exemplary embodiment allows the device to operate at a higher temperature.

[0065] The following will describe each preparation step in detail:

[0066] More preferably, in an exemplary embodiment, such as Figure 3 As shown, the method further includes one or more of the following steps:

[0067] Before growth, the p-GaAs substrate is cleaned and dehydrated;

[0068] Before growth, the surface oxide of the p-GaAs substrate is removed.

[0069] Specifically, in this exemplary embodiment, two pretreatment steps are disclosed before growing the epitaxial structure: one is to clean and dehydrate the p-GaAs substrate before growth, that is, to clean the surface of the p-GaAs substrate; the other is to remove the surface oxide of the p-GaAs substrate before growth, so that the quality of the epitaxial structure grown subsequently is better and will not affect the use process.

[0070] It should be noted that these two steps can be used one at a time. For example, if the surface of the p-GaAs substrate can be confirmed to be clean, then the cleaning and dehydration steps are unnecessary; if the surface of the p-GaAs substrate can be confirmed to be free of oxides, then the oxide removal step is unnecessary. Alternatively, they can be used simultaneously. For example, cleaning and dehydration can be performed first, followed by surface oxide removal, or oxide removal can be performed first, followed by cleaning and dehydration.

[0071] More specifically, in one exemplary embodiment, the cleaning and dehydration of the p-GaAs substrate specifically includes:

[0072] The p-GaAs substrate was immersed and cleaned using a sulfuric acid:hydrochloric acid:hydrogen peroxide ratio of 4:1:1, with stirring during the process. The immersion and cleaning time was 5 minutes. Finally, it was cleaned and dehydrated using 99% anhydrous ethanol.

[0073] More preferably, in an exemplary embodiment, the removal of surface oxides from the p-GaAs substrate includes:

[0074] The p-GaAs substrate is heated to a first temperature, which causes the surface oxide of the p-GaAs substrate to be removed and causes the As atoms of the p-GaAs substrate to evaporate from the surface;

[0075] Heating is used to compensate for As atoms by growing Te atom sources including p-ZnTe thin film layers, ZnTe blocking layers, and (Zn,Cr)Te magnetic layers.

[0076] Specifically, in this exemplary embodiment, the method for removing the surface oxides of the p-GaAs substrate involves heating the p-GaAs substrate to 560°C (a first temperature) and holding it for 5 minutes, under which the oxides can be completely removed. However, during the heating process, especially when the temperature exceeds 400°C, As atoms evaporate from the surface of the p-GaAs substrate, causing lattice defects on the surface, requiring compensation for the As atoms. Therefore, after the surface oxide removal is completed, a Te atom source is used to compensate for the As atoms. More specifically, the Te atom source is heated, and the vacuum vapor pressure (molecular line strength) of the Te atoms is controlled to be 5 x 10⁻⁶. -8 Torr.

[0077] By employing the method described in this exemplary embodiment, the goal of removing surface oxides can be achieved, and the Te atom source can be used to compensate for the As atoms evaporated from the p-GaAs substrate surface, reducing the impact of p-GaAs substrate surface lattice defects on the quality of subsequent products. Furthermore, since the Te atom source is present in subsequent fabrication steps (required for growing p-ZnTe thin films, ZnTe barrier layers, and (Zn,Cr)Te magnetic layers), no additional equipment is needed to achieve this goal, thus reducing costs.

[0078] Furthermore, when using this exemplary embodiment, the pretreatment is preferably performed by first cleaning and dehydration followed by surface oxide removal, because surface oxide removal heats the p-GaAs substrate and the Te atom source, which can be directly adapted to the preparation process of subsequent growth steps. If oxide removal is performed first and then cleaning and dehydration are performed, heating will be performed first, followed by cooling and cleaning, and then heating again, which increases the process time.

[0079] More preferably, in an exemplary embodiment, the growth of the p-ZnTe thin film layer includes the following sub-steps:

[0080] The temperature of the p-GaAs substrate is set to the second temperature. The Zn and Te atomic sources are heated, and the molecular line intensities of Zn and Te are adjusted so that the Zn:Te molecular line intensity ratio reaches the first intensity ratio. N atom doping is performed by radio frequency discharge ion implantation. The first growth time is determined according to the growth rate and preset thickness under the corresponding conditions.

[0081] The growth of the ZnTe barrier layer includes the following sub-steps:

[0082] The temperature of the p-GaAs substrate is set to the third temperature. The Zn atom source and the Te atom source are heated. The molecular line intensities of Zn and Te are adjusted so that the molecular line intensity ratio of Zn:Te reaches the second intensity ratio. The second growth time is then determined according to the growth rate and preset thickness under the corresponding conditions.

[0083] The growth of the (Zn,Cr)Te magnetic layer includes the following sub-steps:

[0084] The temperature of the p-GaAs substrate is set to the fourth temperature. The Zn, Cr, and Te atomic sources are heated, and the molecular line intensities of Zn, Cr, and Te are adjusted so that the molecular line intensity ratio of Zn:Cr:Te reaches the third intensity ratio. The third growth time is then determined based on the growth rate and preset thickness under the corresponding conditions.

[0085] Specifically, in this exemplary embodiment, the growth of the p-ZnTe thin film layer includes the following sub-steps:

[0086] The temperature of the p-GaAs substrate is set to a second temperature. In one exemplary embodiment, the second temperature is 300°C. The Zn atom source and the Te atom source are heated, and the molecular line intensities of Zn and Te are adjusted so that the molecular line intensity ratio of Zn:Te reaches a first intensity ratio. In one exemplary embodiment, the molecular line intensities are 4 x 10⁻⁶. -7 Torr, 6x10 -7 The molecular line intensity ratio of Torr, Zn:Te reaches a first intensity ratio of 1:1.5. N atom doping is carried out by radio frequency discharge ion implantation with a radio frequency discharge frequency of 13.56MHz, a discharge power of 100-200W, and an N2 flow rate controlled at 0.1-1CC / min.

[0087] The first growth time is determined according to the growth rate and preset thickness under the corresponding conditions (in a preferred exemplary embodiment, the thickness of the p-ZnTe thin film layer is 340-380nm). Under the above conditions, the growth rate of the p-ZnTe thin film layer is 0.1nm / s, and when the preset thickness of the p-ZnTe thin film layer is preferably 360nm, the first growth time is 1 hour.

[0088] The growth of the ZnTe barrier layer includes the following sub-steps:

[0089] The temperature of the p-GaAs substrate is set to a third temperature. In an exemplary embodiment, the third temperature is 300°C. The Zn atom source and the Te atom source are heated, and the molecular line intensities of Zn and Te are adjusted so that the Zn:Te molecular line intensity ratio reaches a second intensity ratio. In an exemplary embodiment, the molecular line intensities are 4 x 10⁻⁶. -7 Torr, 6x10 -7The molecular line strength ratio of Torr, Zn:Te reaches a second strength ratio of 1:1.5;

[0090] The second growth time is determined according to the growth rate and preset thickness under the corresponding conditions (in a preferred exemplary embodiment, the thickness of the ZnTe barrier layer is 6-12 nm). Under the above conditions, the growth rate of the ZnTe barrier layer is 0.1 nm / s, and when the preset thickness of the ZnTe barrier layer is 6-12 nm, the second growth time is 60-120 seconds.

[0091] The growth of the (Zn,Cr)Te magnetic layer includes the following sub-steps:

[0092] The temperature of the p-GaAs substrate is set to a fourth temperature. In an exemplary embodiment, the fourth temperature is 300°C. The Zn atom source, Cr atom source, and Te atom source are heated, and the molecular line intensities of Zn, Cr, and Te are adjusted so that the molecular line intensity ratio of Zn:Cr:Te reaches a third intensity ratio. In an exemplary embodiment, the molecular line intensities are 9 x 10⁻⁶. -8 Torr, 1x10 -8 Torr and 2x10 -7 The molecular line strength ratio of Torr, Zn:Cr:Te reaches the third strength ratio of 9:1:20;

[0093] The third growth time is determined according to the growth rate and preset thickness under the corresponding conditions (in a preferred exemplary embodiment, the thickness of the (Zn,Cr)Te magnetic layer is 8-12 nm). Under the above conditions, the growth rate of the (Zn,Cr)Te magnetic layer is 0.1 nm / s, and when the preset thickness of the (Zn,Cr)Te magnetic layer is preferably 10 nm, the third growth time is 100 seconds.

[0094] It should be noted that for the growth of the (Zn,Cr)Te magnetic layer, when the molecular line strengths of Zn:Cr:Te are 9x10⁻¹⁰, ... -8 Torr, 1x10 -8 Torr and 2x10 -7 When the molecular line strength ratio of Torr, Zn:Cr:Te reaches the third strength ratio of 9:1:20, the resulting (Zn,Cr)Te magnetic layer is (Zn 90％ Cr 10％ The Te magnetic layer can be adjusted in strength ratio according to actual needs.

[0095] Furthermore, and more preferably, in an exemplary embodiment, the second, third, and fourth temperatures are all the same, specifically 300°C as described above. Setting the same p-GaAs substrate temperature for multiple growth steps eliminates the need for unnecessary adjustments throughout the process. Moreover, this temperature does not reach the temperature (exceeding 400°C) that would cause lattice defects on the p-GaAs substrate surface.

[0096] More preferably, in an exemplary embodiment, the growth of the AlN insulating layer includes the following sub-steps:

[0097] The Al atom source is heated to adjust the molecular line strength of Al, and N atoms are implanted using radio frequency discharge ion implantation; the fourth growth time is determined according to the growth rate and preset thickness under the corresponding conditions.

[0098] The growth of the Au voltage lead-out layer includes the following sub-steps:

[0099] The Au voltage lead-out layer was grown using an electron beam evaporation apparatus; the fifth time was used to deposit the layer according to the growth rate and preset thickness under the corresponding conditions.

[0100] Specifically, in this exemplary embodiment, the growth of the AlN insulating layer includes the following sub-steps:

[0101] The Al atom source is heated to adjust the molecular line strength of Al. In an exemplary embodiment, the growth temperature is set to 280°C, and the molecular line strength of Al is adjusted to 6 x 10⁻⁶. -9 Torr, N atoms are implanted using radio frequency discharge ion implantation, with a radio frequency discharge frequency of 13.56MHz, a discharge power of 3W, and an N2 flow rate controlled at 0.5CC / min;

[0102] The fourth growth time is determined according to the growth rate and preset thickness under the corresponding conditions (in a preferred exemplary embodiment, the thickness of the AlN insulating layer is 35-45 nm). Under the above conditions, the growth rate of the AlN insulating layer is 0.1 nm / s, and when the preset thickness of the AlN insulating layer is preferably 40 nm, the fourth growth time is 400 seconds.

[0103] It should be noted that, compared to the existing technology that uses an AlO insulating layer, this exemplary embodiment uses an AlN insulating layer, which allows the use of the radio frequency discharge ion implantation equipment used in the N atom doping process in the growth of the p-ZnTe thin film to be used directly without the need for other equipment, thus reducing costs.

[0104] The growth of the Au voltage lead-out layer includes the following sub-steps:

[0105] In an exemplary embodiment, an Au voltage extraction layer is grown using an electron beam evaporation apparatus, with the vacuum level controlled at 10. -6Below Torr, the electron beam energy is 15kW;

[0106] The fifth deposition time is determined according to the growth rate and preset thickness (in a preferred exemplary embodiment, the thickness of the Au voltage lead-out layer is 25-35 nm) under the corresponding conditions. Under the above conditions, the growth rate of the Au voltage lead-out layer is 0.3 nm / s, and when the preset thickness of the Au voltage lead-out layer is 30 nm, the fifth deposition time is 100 seconds.

[0107] The following exemplary embodiments will illustrate the specific details of the ZnTe barrier layer thickness, the barrier effect of the ZnTe barrier layer, and improving the effective operating temperature of the device:

[0108] Epitaxial structures with ZnTe blocking layers of various thicknesses were tested using superconducting magnetic flux quantum interference device (SQUID) at a temperature of 2K. The test results are as follows: Figure 4 As shown, the epitaxial structure exhibits significant ferromagnetic properties with increasing ZnTe barrier layer thickness. This implies that the ZnTe barrier layer can prevent N atoms from diffusing from the p-ZnTe thin film to the (Zn,Cr)Te magnetic layer. The magnetization results show that, especially when the applied magnetic field is within ±0.1T, the film exhibits a distinct "S"-shaped magnetization curve when the ZnTe barrier layer thickness is 6-12 nm. However, when the ZnTe barrier layer thickness is approximately 3 nm, the magnetization is much smaller than that of the 6-12 nm thickness. Therefore, the optimal ZnTe barrier layer thickness is considered to be 6-12 nm.

[0109] X-ray absorption fine structure analysis was performed on the epitaxial structures of ZnTe stopper layers of various thicknesses. The test results are as follows: Figure 5 As shown. Among them, Figure 5 The left figure shows the X-ray absorption fine structure curves of epitaxial structures with ZnTe stopper layers of different thicknesses. From the curves, the structural composition around Cr atoms and the changes in Cr electrons can be derived. A series of curves show that when the ZnTe stopper layer thickness is 2.8 nm, the curve shape is close to that of CrN & CrN2, which can be approximated as the presence of N atoms around Cr atoms, and the number of Cr electrons is close to that of CrN & CrN2. As the ZnTe stopper layer thickness increases, the X-ray absorption fine structure curves also change. When the ZnTe stopper layer thickness is 12 nm, the curve shape is close to (Zn... 98.7％ ,Cr 1.3％ The curve for Te can be approximated by assuming that the Cr atoms are surrounded by Te atoms, with no N atoms present. Figure 5 The right figure shows the calculation results of the dynamic path function. Similarly, as the thickness of the ZnTe stopper layer increases, (Zn 90％ ,Cr10％ The fine structure around Cr atoms in the Te thin film is similar to that of the reference Zn. 98.7％ ,Cr 1.3％ The fine structure of the (Zn, Cr)Te thin film. Therefore, it can be considered that the use of the ZnTe blocking layer proposed in the exemplary embodiment of the present invention can block the diffusion of N atoms from the p-ZnTe thin film layer to the (Zn, Cr)Te magnetic layer.

[0110] An epitaxial structure with a 12 nm thick ZnTe stop layer was subjected to an applied voltage at 100 K. The magnetic properties at different voltages were measured using a superconducting magnetic flux quantum interference device (SQUID). The test results are as follows: Figure 6 As shown, when the applied voltage is +10V, the magnetization of the epitaxial structure is smaller than that without an applied voltage. This is because when a positive voltage is applied, the interface between the p-ZnTe thin film and the ZnTe blocking layer carries a negative charge due to electrostatic force, while the interface between the (Zn,Cr)Te magnetic layer and the ZnTe blocking layer carries a positive charge. This causes band bending of Cr 3d electrons, resulting in a decrease in the number of Cr 3d electrons at the Fermi level, thus reducing the magnetization. Conversely, when a negative voltage is applied, the interface between the (Zn,Cr)Te magnetic layer and the ZnTe blocking layer carries a negative charge, leading to an increase in the number of Cr 3d electrons at the Fermi level, thus increasing the magnetization. This result demonstrates that at 100K, the magnitude of the magnetism of the epitaxial structure can be changed by the magnitude of the applied voltage. This exemplary embodiment of the invention provides a possibility for future applications of electron spin (previous technologies only allow for 10K).

[0111] Having the same technical inspiration as the exemplary embodiments described above, another exemplary embodiment of the present invention provides an apparatus for fabricating epitaxial structures of dilute magnetic semiconductor thin film materials, such as... Figure 7 include:

[0112] A molecular beam epitaxy (MBE) equipment is used to sequentially grow a p-ZnTe thin film, a ZnTe blocking layer, a (Zn,Cr)Te magnetic layer, and an AlN insulating layer on a p-GaAs substrate. The MBE equipment includes a Zn atom source implantation device, a Te atom source implantation device, a Cr atom source implantation device, an Al atom source implantation device, and an N atom radio frequency discharge ion implantation device.

[0113] Electron beam evaporation equipment for depositing Au voltage lead layers on AlN insulating layers.

[0114] More preferably, in an exemplary embodiment, the preparation apparatus further includes:

[0115] Cleaning and dehydration equipment is used for cleaning and dehydrating p-GaAs substrates before growth.

[0116] More preferably, in an exemplary embodiment, the molecular beam epitaxy equipment is also used for oxide removal in the pre-growth treatment of the p-GaAs substrate.

[0117] More preferably, in an exemplary embodiment, the molecular beam epitaxy growth apparatus is further used for oxide removal in the pre-growth treatment of the p-GaAs substrate, including:

[0118] The p-GaAs substrate is heated to a first temperature, which causes the surface oxide of the p-GaAs substrate to be removed and causes the As atoms of the p-GaAs substrate to evaporate from the surface;

[0119] Heating is used to compensate for As atoms by growing Te atom sources including p-ZnTe thin film layers, ZnTe blocking layers, and (Zn,Cr)Te magnetic layers.

[0120] More preferably, in an exemplary embodiment, the growth of the p-ZnTe thin film layer includes the following sub-steps:

[0121] In a molecular beam epitaxy (MBE) apparatus, the temperature of the p-GaAs substrate is set to a second temperature. Zn and Te atomic sources are heated, and the molecular line intensities of Zn and Te are adjusted using Zn and Te atomic source implantation devices, respectively, to achieve a Zn:Te molecular line intensity ratio of a first intensity ratio. N-atom doping is performed using an N-atom radio frequency discharge ion implantation device. The growth is carried out for a first time according to the growth rate and preset thickness under the corresponding conditions.

[0122] The growth of the ZnTe barrier layer includes the following sub-steps:

[0123] In a molecular beam epitaxy (MBE) equipment, the temperature of the p-GaAs substrate is set to the third temperature. The Zn atomic source and the Te atomic source are heated. The molecular line intensities of Zn and Te are adjusted by the Zn atomic source injection device and the Te atomic source injection device, respectively, so that the molecular line intensity ratio of Zn:Te reaches the second intensity ratio. The second growth time is determined according to the growth rate and preset thickness under the corresponding conditions.

[0124] The growth of the (Zn,Cr)Te magnetic layer includes the following sub-steps:

[0125] In a molecular beam epitaxy (MBE) equipment, the temperature of the p-GaAs substrate is set to the fourth temperature. The Zn, Cr, and Te atomic sources are heated. The molecular line intensities of Zn, Cr, and Te are adjusted by the Zn, Cr, and Te atomic source injection devices, respectively, so that the molecular line intensity ratio of Zn:Cr:Te reaches the third intensity ratio. The third growth time is then determined based on the growth rate and preset thickness under the corresponding conditions.

[0126] More preferably, in an exemplary embodiment, the second temperature, the third temperature, and the fourth temperature are the same.

[0127] More preferably, in an exemplary embodiment, the growth of the AlN insulating layer includes the following sub-steps:

[0128] In a molecular beam epitaxy (MBE) equipment, an Al atom source is heated, and the molecular line strength of Al is adjusted using an Al atom source implantation device. N atom doping is performed using an N atom radio frequency discharge ion implantation device. The fourth growth time is determined according to the growth rate and preset thickness under the corresponding conditions.

[0129] The growth of the Au voltage lead-out layer includes the following sub-steps:

[0130] The Au voltage lead-out layer was grown using an electron beam evaporation apparatus; the fifth time was used to deposit the layer according to the growth rate and preset thickness under the corresponding conditions.

[0131] Having the same inventive concept as the above exemplary embodiments, another exemplary embodiment of the present invention provides a photonic spin transistor (MOSFET) including the epitaxial structure of the dilute magnetic semiconductor thin film material; or including the epitaxial structure prepared by the preparation method.

[0132] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An epitaxial structure of a dilute magnetic semiconductor thin film material, characterized in that: It includes, from bottom to top, the following layers arranged in sequence: p-GaAs substrate, p-ZnTe thin film layer, ZnTe blocking layer, (Zn,Cr)Te magnetic layer, AlN insulating layer, and Au voltage lead-out layer, wherein the doping element of the p-ZnTe thin film layer is N atoms.

2. The epitaxial structure of a dilute magnetic semiconductor thin film material according to claim 1, characterized in that: The thickness of the p-ZnTe thin film layer is 340-380 nm; the thickness of the ZnTe blocking layer is 6-12 nm; the thickness of the (Zn,Cr)Te magnetic layer is 8-12 nm; the thickness of the AlN insulating layer is 35-45 nm; and the thickness of the Au voltage lead-out layer is 25-35 nm.

3. The epitaxial structure of a dilute magnetic semiconductor thin film material according to claim 2, characterized in that: The thickness of the p-GaAs substrate is 657 μm.

4. The epitaxial structure of a dilute magnetic semiconductor thin film material according to claim 1, characterized in that: The N atom content of the p-ZnTe thin film is 10. 19 cm -3 .

5. A method for preparing an epitaxial structure of a dilute magnetic semiconductor thin film material, characterized in that: Includes the following steps: A p-ZnTe thin film layer, a ZnTe blocking layer, a (Zn,Cr)Te magnetic layer, an AlN insulating layer, and an Au voltage lead-out layer are sequentially grown on a p-GaAs substrate, wherein the doping element of the p-ZnTe thin film layer is N atoms.

6. The method for preparing an epitaxial structure of a dilute magnetic semiconductor thin film material according to claim 5, characterized in that: The method further includes one or more of the following steps: Before growth, the p-GaAs substrate is cleaned and dehydrated; Before growth, the surface oxide of the p-GaAs substrate is removed.

7. The method for preparing an epitaxial structure of a dilute magnetic semiconductor thin film material according to claim 6, characterized in that: The removal of surface oxides from the p-GaAs substrate includes: The p-GaAs substrate is heated to a first temperature, which causes the surface oxide of the p-GaAs substrate to be removed and causes the As atoms of the p-GaAs substrate to evaporate from the surface; Heating is used to compensate for As atoms by growing Te atom sources including p-ZnTe thin film layers, ZnTe blocking layers, and (Zn,Cr)Te magnetic layers.

8. The method for preparing an epitaxial structure of a dilute magnetic semiconductor thin film material according to claim 5, characterized in that: The growth of the p-ZnTe thin film layer includes the following sub-steps: The temperature of the p-GaAs substrate is set to the second temperature. The Zn and Te atomic sources are heated, and the molecular line intensities of Zn and Te are adjusted so that the Zn:Te molecular line intensity ratio reaches the first intensity ratio. N atom doping is performed by radio frequency discharge ion implantation. The first growth time is determined according to the growth rate and preset thickness under the corresponding conditions. The growth of the ZnTe barrier layer includes the following sub-steps: The temperature of the p-GaAs substrate is set to the third temperature. The Zn atom source and the Te atom source are heated. The molecular line intensities of Zn and Te are adjusted so that the molecular line intensity ratio of Zn:Te reaches the second intensity ratio. The second growth time is then determined according to the growth rate and preset thickness under the corresponding conditions. The growth of the (Zn,Cr)Te magnetic layer includes the following sub-steps: The temperature of the p-GaAs substrate is set to the fourth temperature. The Zn, Cr, and Te atomic sources are heated, and the molecular line intensities of Zn, Cr, and Te are adjusted so that the molecular line intensity ratio of Zn:Cr:Te reaches the third intensity ratio. The third growth time is then determined based on the growth rate and preset thickness under the corresponding conditions.

9. The method for preparing an epitaxial structure of a dilute magnetic semiconductor thin film material according to claim 8, characterized in that: The second, third, and fourth temperatures are the same.

10. The method for preparing an epitaxial structure of a dilute magnetic semiconductor thin film material according to claim 5, characterized in that: The growth of the AlN insulating layer includes the following sub-steps: The Al atom source is heated to adjust the molecular line strength of Al, and N atoms are implanted using radio frequency discharge ion implantation; the fourth growth time is determined according to the growth rate and preset thickness under the corresponding conditions. The growth of the Au voltage lead-out layer includes the following sub-steps: The Au voltage lead-out layer was grown using an electron beam evaporation apparatus; the fifth time was used to deposit the layer according to the growth rate and preset thickness under the corresponding conditions.

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