Semiconductor structure and method of manufacturing a semiconductor structure

Abstract

The application relates to a semiconductor structure and a preparation method of the semiconductor structure, and the semiconductor structure comprises: a first AlGaN / AlN / GaN heterostructure, a first two-dimensional electron gas channel existing at the interface between the AlN layer and the GaN layer in the first AlGaN / AlN / GaN heterostructure; a second AlGaN / AlN / GaN heterostructure, a second two-dimensional electron gas channel existing at the interface between the AlN layer and the GaN layer in the second AlGaN / AlN / GaN heterostructure; and a third AlGaN / AlN / GaN heterostructure, a third two-dimensional electron gas channel existing at the interface between the AlN layer and the GaN layer in the third AlGaN / AlN / GaN heterostructure; the difference between the electron concentration in the first two-dimensional electron gas channel, the electron concentration in the second two-dimensional electron gas channel and the electron concentration in the third two-dimensional electron gas channel is less than a preset value, thereby adjusting the carrier distribution, so as to achieve the purposes of reducing the device resistance value, reducing the reverse leakage current and reducing the heat generation in the working state of the device.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor, in particular to a semiconductor structure and a preparation method of the semiconductor structure. BACKGROUND

[0002] Because of the existence of 2DEG (two-dimensional electron gas) with high carrier concentration and mobility at the AlGaN / GaN heterojunction interface, in order to reduce the series resistance of the electronic device based on the AlGaN / GaN heterojunction material, various multi-heterojunction AlGaN / GaN heterojunction materials have been designed in the existing research. The common heterojunction material is a multi-heterojunction AlGaN / GaN heterojunction material with equal thickness of each AlGaN barrier layer. Because of the existence of negative polarization charge at the GaN / AlGaN heterojunction interface, the 2DEG concentration at each AlGaN / GaN heterojunction interface is quite different. Because the 2DEG concentration closest to the substrate is larger, it is difficult to be depleted, so the reverse leakage current of the electronic device with a recessed gate prepared based on the multi-heterojunction AlGaN / GaN heterojunction material is higher. And because the 2DEG concentration is quite different, the heat generation of each layer is different when working, which will affect the performance of the device. SUMMARY

[0003] To solve the above technical problems, the present application designs a semiconductor structure and a preparation method of the semiconductor structure, adjusts the carrier distribution, reduces the device resistance value, reduces the reverse leakage current of the electronic device and reduces the heat generation of the device in the working state.

[0004] The present application designs a semiconductor structure, which comprises:

[0005] A first AlGaN / AlN / GaN heterostructure, a first two-dimensional electron gas channel exists at the interface between the AlN layer and the GaN layer in the first AlGaN / AlN / GaN heterostructure;

[0006] A second AlGaN / AlN / GaN heterostructure, a second two-dimensional electron gas channel exists at the interface between the AlN layer and the GaN layer in the second AlGaN / AlN / GaN heterostructure;

[0007] A third AlGaN / AlN / GaN heterostructure, a third two-dimensional electron gas channel exists at the interface between the AlN layer and the GaN layer in the third AlGaN / AlN / GaN heterostructure;

[0008] The difference between the electron concentration in the first two-dimensional electron gas channel, the electron concentration in the second two-dimensional electron gas channel and the electron concentration in the third two-dimensional electron gas channel is less than a preset value.

[0009] In one of the embodiments, the thickness of the AlGaN layer in the first AlGaN / AlN / GaN heterostructure is the same as the thickness of the AlGaN layer in the third AlGaN / AlN / GaN heterostructure, and both are smaller than the thickness of the AlGaN layer in the second AlGaN / AlN / GaN heterostructure.

[0010] In one of the embodiments, the thickness of the GaN layer in the first AlGaN / AlN / GaN heterostructure, the thickness of the GaN layer in the second AlGaN / AlN / GaN heterostructure, and the thickness of the GaN layer in the third AlGaN / AlN / GaN heterostructure are the same; the thickness of the AlN layer in the first AlGaN / AlN / GaN heterostructure, the thickness of the AlN layer in the second AlGaN / AlN / GaN heterostructure, and the thickness of the AlN layer in the third AlGaN / AlN / GaN heterostructure are the same.

[0011] In one of the embodiments, the first AlGaN / AlN / GaN heterostructure, the second AlGaN / AlN / GaN heterostructure, and the third AlGaN / AlN / GaN heterostructure are all unintentionally doped heterostructures, and the background carrier concentration of the first AlGaN / AlN / GaN heterostructure, the background carrier concentration of the second AlGaN / AlN / GaN heterostructure, and the background carrier concentration of the third AlGaN / AlN / GaN heterostructure are all 0.5*10 16 cm -3 ~1.5*10 16 cm -3 .

[0012] In one of the embodiments, the semiconductor structure further comprises:

[0013] a substrate;

[0014] a nucleation layer on the surface of the substrate;

[0015] a buffer layer on the surface of the nucleation layer away from the substrate; the first AlGaN / AlN / GaN heterostructure is on the surface of the buffer layer away from the nucleation layer.

[0016] The present application also designs a preparation method of a semiconductor structure, which comprises:

[0017] forming a first AlGaN / AlN / GaN heterostructure, wherein a first two-dimensional electron gas channel exists at the interface between the AlN layer and the GaN layer in the first AlGaN / AlN / GaN heterostructure;

[0018] a second AlGaN / AlN / GaN heterostructure is formed on the surface of the first AlGaN / AlN / GaN heterostructure, and a second two-dimensional electron gas channel exists at the interface between the AlN layer and the GaN layer in the second AlGaN / AlN / GaN heterostructure;

[0019] a third AlGaN / AlN / GaN heterostructure is formed on the surface of the second AlGaN / AlN / GaN heterostructure, and a third two-dimensional electron gas channel exists at the interface between the AlN layer and the GaN layer in the third AlGaN / AlN / GaN heterostructure;

[0020] The difference between the electron concentration in the first two-dimensional electron gas channel, the electron concentration in the second two-dimensional electron gas channel, and the electron concentration in the third two-dimensional electron gas channel is less than a preset value.

[0021] In one of the embodiments, the thickness of the AlGaN layer in the first AlGaN / AlN / GaN heterostructure formed is the same as the thickness of the AlGaN layer in the third AlGaN / AlN / GaN heterostructure formed, and is less than the thickness of the AlGaN layer in the second AlGaN / AlN / GaN heterostructure formed.

[0022] In one of the embodiments, the thickness of the GaN layer in the first AlGaN / AlN / GaN heterostructure formed, the thickness of the GaN layer in the second AlGaN / AlN / GaN heterostructure formed, and the thickness of the GaN layer in the third AlGaN / AlN / GaN heterostructure formed are the same; and the thickness of the AlN layer in the first AlGaN / AlN / GaN heterostructure formed, the thickness of the AlN layer in the second AlGaN / AlN / GaN heterostructure formed, and the thickness of the AlN layer in the third AlGaN / AlN / GaN heterostructure formed are the same.

[0023] In one of the embodiments, the first AlGaN / AlN / GaN heterostructure, the second AlGaN / AlN / GaN heterostructure and the third AlGaN / AlN / GaN heterostructure are epitaxially grown by a metal organic chemical vapor deposition process, and each of the first AlGaN / AlN / GaN heterostructure, the second AlGaN / AlN / GaN heterostructure and the third AlGaN / AlN / GaN heterostructure is a non-intentionally doped heterostructure, and the background carrier concentration of the first AlGaN / AlN / GaN heterostructure, the background carrier concentration of the second AlGaN / AlN / GaN heterostructure and the background carrier concentration of the third AlGaN / AlN / GaN heterostructure are all 0.5×10 16 cm -3 ~1.5×10 16 cm -3 .

[0024] In one of the embodiments, the method further comprises, before forming the first AlGaN / AlN / GaN heterostructure:

[0025] providing a substrate;

[0026] forming a nucleation layer on a surface of the substrate;

[0027] forming a buffer layer on a surface of the nucleation layer away from the substrate; and forming the first AlGaN / AlN / GaN heterostructure on a surface of the buffer layer away from the nucleation layer.

[0028] The present application has the following advantages:

[0029] The semiconductor structure and the preparation method of the semiconductor structure, wherein the semiconductor structure comprises a first AlGaN / AlN / GaN heterostructure, a second AlGaN / AlN / GaN heterostructure and a third AlGaN / AlN / GaN heterostructure, and a first two-dimensional electron gas channel exists at the interface between the AlN layer and the GaN layer in the first AlGaN / AlN / GaN heterostructure; a second two-dimensional electron gas channel exists at the interface between the AlN layer and the GaN layer in the second AlGaN / AlN / GaN heterostructure; and a third two-dimensional electron gas channel exists at the interface between the AlN layer and the GaN layer in the third AlGaN / AlN / GaN heterostructure; the difference between the electron concentration in the first two-dimensional electron gas channel, the electron concentration in the second two-dimensional electron gas channel and the electron concentration in the third two-dimensional electron gas channel is less than a preset value, so as to realize the purposes of reducing the resistance value of the device, reducing the reverse leakage current and reducing the heat generation in the working state of the device. The application also discloses a preparation method of the semiconductor structure, which discloses the positional relationship among the first AlGaN / AlN / GaN heterostructure, the second AlGaN / AlN / GaN heterostructure and the third AlGaN / AlN / GaN heterostructure, the positional relationship among the layers of each heterostructure and the position of each two-dimensional electron gas channel, and the above semiconductor structure can be prepared according to the method. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 FIG. 1 is a schematic diagram of the semiconductor structure in one embodiment of the application.

[0031] Figure 2 FIG. 2 is a distribution diagram of the carrier in the semiconductor structure with the change of the structure depth in one embodiment of the application.

[0032] Figure 3 FIG. 3 is a distribution diagram of the energy band in the semiconductor structure with the change of the structure depth in one embodiment of the application. The dotted line is the Fermi energy level position line; and the solid line is the energy band curve of the semiconductor structure.

[0033] Figure 4 FIG. 4 is a flow chart of the preparation method of the semiconductor structure in one embodiment of the application.

[0034] Figure 5 FIG. 5 is a flow chart of the preparation method of the semiconductor structure in another embodiment of the application.

[0035] BRIEF DESCRIPTION OF DRAWINGS

[0036] 1. first AlGaN / AlN / GaN heterostructure; 11. GaN layer of the first AlGaN / AlN / GaN heterostructure; 12. AlN layer of the first AlGaN / AlN / GaN heterostructure; 13. AlGaN layer of the first AlGaN / AlN / GaN heterostructure; 2. second AlGaN / AlN / GaN heterostructure; 21. GaN layer of the second AlGaN / AlN / GaN heterostructure; 22. AlN layer of the second AlGaN / AlN / GaN heterostructure; 23. AlGaN layer of the second AlGaN / AlN / GaN heterostructure; 3. third AlGaN / AlN / GaN heterostructure; 31. GaN layer of the third AlGaN / AlN / GaN heterostructure; 32. AlN layer of the third AlGaN / AlN / GaN heterostructure; 33. AlGaN layer of the third AlGaN / AlN / GaN heterostructure; 4. substrate; 5. nucleation layer; 6. buffer layer. DETAILED DESCRIPTION

[0037] In order to make the above objectives, features and advantages of the present application more clear and easily understood, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced in a number of different manners according to other embodiments, and those skilled in the art can make similar improvements without departing from the scope of the present application, and therefore the present application is not limited to the specific embodiments disclosed below.

[0038] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0039] In addition, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features referred to. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0040] In the present application, unless specifically defined otherwise, the terms "mounting", "connected", "connecting", "fixed", "fixing", and the like are used broadly and encompass both direct and indirect mounting, connecting, and fixing, and can further include fixed, detachable, or integral mounting, connecting, and fixing, and mechanical or electrical connecting, and can further include direct or indirect connection through an intermediate medium, and can further include internal communication between two elements or interaction between two elements, unless otherwise specifically defined and limited. The specific meanings of the above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances.

[0041] In the present application, unless specifically defined otherwise, the first feature "on" or "under" the second feature can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature "above", "over", and "on" the second feature can be that the first feature is directly above or obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "under", and "under" the second feature can be that the first feature is directly below or obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0042] It should be noted that when an element is referred to as "fixed" or "disposed" on another element, it can be directly on the other element or there can be a mediating element. When an element is referred to as "connected" to another element, it can be directly connected to the other element or there can be a mediating element. The terms "vertical", "horizontal", "up", "down", "left", "right", and the like used herein are for illustrative purposes only and are not the only implementation.

[0043] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and are not intended to limit the present application.

[0044] For the semiconductor mutant heterojunction, due to the existence of the conduction band bottom energy mutation amount DeltaEc, then in the interface vicinity appears "peak" and "notch"; in fact, for the effect of the conduction band electron in the heterojunction, the "peak" is also the potential barrier of electron, and the "notch" is also the potential well of electron. Therefore, in fact, the electric field in the "peak" has the effect of driving electron, that is, forming the depletion layer; the electric field in the "notch" has the effect of driving hole and accumulating electron, and under suitable conditions, an electron accumulation layer (i.e. surface conductive channel) can be formed. If the depth of the "notch" potential well is large enough, the electron in the "notch" potential well can only move in the plane in each direction (i.e. close to the heterojunction interface), that is, the electron is two-dimensional motion; further, if the effective mass concept is introduced, the electron in the heterojunction potential well can be considered as "two-dimensional electron gas" (2DEG) with certain effective mass.

[0045] Since the AlGaN / GaN heterojunction interface exists 2DEG (two-dimensional electron gas) with high carrier concentration and mobility, in order to reduce the series resistance of the electronic device based on the AlGaN / GaN heterojunction material, various multi-heterojunction AlGaN / GaN heterojunction materials have been designed in the existing research. Common heterojunction materials are multi-heterojunction AlGaN / GaN heterojunction materials with equal thickness of each AlGaN barrier layer. Due to the existence of negative polarization charge at the GaN / AlGaN heterojunction interface, the 2DEG concentration at each AlGaN / GaN heterojunction interface is quite different. Since the 2DEG concentration closest to the substrate is large, it is difficult to be depleted, so the reverse leakage current of the electronic device with a recessed gate prepared based on the multi-heterojunction AlGaN / GaN heterojunction material is high. And due to the large difference in the 2DEG concentration of each layer, the heat generation of each layer is different during operation, which affects the performance of the device.

[0046] To solve the above technical problems, the present application designs a semiconductor structure and a preparation method of the semiconductor structure, adjusts the carrier distribution, reduces the resistance value of the device, and reduces the reverse leakage current of the electronic device and the heat generation under the working state of the device.

[0047] The present application designs a semiconductor structure, as Figure 1As shown, the semiconductor structure comprises: a first AlGaN / AlN / GaN heterostructure 1, a first two-dimensional electron gas channel existing at the interface between the AlN layer 12 and the GaN layer 11 in the first AlGaN / AlN / GaN heterostructure 1; a second AlGaN / AlN / GaN heterostructure 2, a second two-dimensional electron gas channel existing at the interface between the AlN layer 22 and the GaN layer 21 in the second AlGaN / AlN / GaN heterostructure 2; a third AlGaN / AlN / GaN heterostructure 3, a third two-dimensional electron gas channel existing at the interface between the AlN layer 32 and the GaN layer 31 in the third AlGaN / AlN / GaN heterostructure 3; and the difference between the electron concentration in the first two-dimensional electron gas channel, the electron concentration in the second two-dimensional electron gas channel and the electron concentration in the third two-dimensional electron gas channel is less than a preset value.

[0048] In one embodiment, the electron concentration in the first two-dimensional electron gas channel, the electron concentration in the second two-dimensional electron gas channel and the electron concentration in the third two-dimensional electron gas channel are all the same.

[0049] Specifically, in order to make the electron concentration in the first two-dimensional electron gas channel, the electron concentration in the second two-dimensional electron gas channel and the electron concentration in the third two-dimensional electron gas channel the same, and based on the process error consideration, it is necessary to make the difference between the electron concentration in the first two-dimensional electron gas channel, the electron concentration in the second two-dimensional electron gas channel and the electron concentration in the third two-dimensional electron gas channel as small as possible, that is, the preset value is as small as possible.

[0050] The semiconductor structure of the present application comprises a first AlGaN / AlN / GaN heterostructure 1, a second AlGaN / AlN / GaN heterostructure 2 and a third AlGaN / AlN / GaN heterostructure 3, and a first two-dimensional electron gas channel exists at the interface between the AlN layer 12 and the GaN layer 11 in the first AlGaN / AlN / GaN heterostructure 1; a second two-dimensional electron gas channel exists at the interface between the AlN layer 22 and the GaN layer 21 in the second AlGaN / AlN / GaN heterostructure 2; a third two-dimensional electron gas channel exists at the interface between the AlN layer 32 and the GaN layer 31 in the third AlGaN / AlN / GaN heterostructure 3; and the difference between the electron concentration in the first two-dimensional electron gas channel, the electron concentration in the second two-dimensional electron gas channel and the electron concentration in the third two-dimensional electron gas channel is less than a preset value, so as to achieve the purpose of reducing the device resistance value, reducing the reverse leakage current and reducing the heat generation in the working state of the device.

[0051] In one of the embodiments, the thickness of the AlGaN layer 13 in the first AlGaN / AlN / GaN heterostructure 1 is the same as the thickness of the AlGaN layer 33 in the third AlGaN / AlN / GaN heterostructure 3, and is less than the thickness of the AlGaN layer 23 in the second AlGaN / AlN / GaN heterostructure 2.

[0052] Specifically, the thickness of the AlGaN layer 13 in the first AlGaN / AlN / GaN heterostructure 1 and the thickness of the AlGaN layer 33 in the third AlGaN / AlN / GaN heterostructure 3 can include 6-10 nm, for example, 6 nm, 7 nm, 8 nm, 9 nm or 10 nm can be used; in this embodiment, the thickness of the AlGaN layer 13 in the first AlGaN / AlN / GaN heterostructure 1 and the thickness of the AlGaN layer 33 in the third AlGaN / AlN / GaN heterostructure 3 are both 8 nm.

[0053] Specifically, the thickness of the AlGaN layer 23 in the second AlGaN / AlN / GaN heterostructure 2 can include 30-50 nm, for example, 30 nm, 35 nm, 40 nm, 45 nm or 50 nm can be used; in this embodiment, the thickness of the AlGaN layer 23 in the second AlGaN / AlN / GaN heterostructure 2 is 40 nm.

[0054] In one of the embodiments, the thickness of the GaN layer 11 in the first AlGaN / AlN / GaN heterostructure 1, the thickness of the GaN layer 21 in the second AlGaN / AlN / GaN heterostructure 2 and the thickness of the GaN layer 31 in the third AlGaN / AlN / GaN heterostructure 3 are the same; the thickness of the AlN layer 12 in the first AlGaN / AlN / GaN heterostructure 1, the thickness of the AlN layer 22 in the second AlGaN / AlN / GaN heterostructure 2 and the thickness of the AlN layer 32 in the third AlGaN / AlN / GaN heterostructure 3 are the same.

[0055] Specifically, the thickness of the GaN layer 11 in the first AlGaN / AlN / GaN heterostructure 1, the thickness of the GaN layer 21 in the second AlGaN / AlN / GaN heterostructure 2 and the thickness of the GaN layer 31 in the third AlGaN / AlN / GaN heterostructure 3 can include 8-12 nm, for example, 8 nm, 9 nm, 10 nm, 11 nm or 12 nm can be used; in this embodiment, the thickness of the GaN layer 11 in the first AlGaN / AlN / GaN heterostructure 1, the thickness of the GaN layer 21 in the second AlGaN / AlN / GaN heterostructure 2 and the thickness of the GaN layer 31 in the third AlGaN / AlN / GaN heterostructure 3 are all 10 nm.

[0056] Specifically, the thickness of the AlN layer 12 in the first AlGaN / AlN / GaN heterostructure 1, the thickness of the AlN layer 22 in the second AlGaN / AlN / GaN heterostructure 2, and the thickness of the AlN layer 32 in the third AlGaN / AlN / GaN heterostructure 3 can include 0.5-1.5 nm, for example, 0.5 nm, 0.8 nm, 1 nm, 1.2 nm, or 1.5 nm can be used; in the embodiment, the thickness of the AlN layer 12 in the first AlGaN / AlN / GaN heterostructure 1, the thickness of the AlN layer 22 in the second AlGaN / AlN / GaN heterostructure 2, and the thickness of the AlN layer 32 in the third AlGaN / AlN / GaN heterostructure 3 are all 1 nm.

[0057] In one embodiment, the first AlGaN / AlN / GaN heterostructure 1, the second AlGaN / AlN / GaN heterostructure 2, and the third AlGaN / AlN / GaN heterostructure 3 are all non-intentionally doped heterostructures, and the background carrier concentration of the first AlGaN / AlN / GaN heterostructure 1, the background carrier concentration of the second AlGaN / AlN / GaN heterostructure 2, and the background carrier concentration of the third AlGaN / AlN / GaN heterostructure 3 are all 0.5*10 16 cm -3 -1.5*10 16 cm -3 .

[0058] Specifically, the background carrier concentration of the first AlGaN / AlN / GaN heterostructure 1, the background carrier concentration of the second AlGaN / AlN / GaN heterostructure 2, and the background carrier concentration of the third AlGaN / AlN / GaN heterostructure 3 can all be 0.5*10 16 cm -3 , 1*10 16 cm -3 , or 1.5*10 16 cm -3 , etc.

[0059] Specifically, if the polarization charge at the AlGaN / GaN heterojunction interface considers both the spontaneous polarization effect and the piezoelectric polarization effect, and also considers the influence of piezoelectric polarization on the dielectric constant of the AlGaN / GaN heterojunction, then the total polarization intensity P of the AlGaN / GaN heterojunction at the interface can be expressed as equation (1) as follows:

[0060]

[0061] Where a0 and a are the lattice constants of AlGaN and GaN, respectively; ε is the dielectric constant of AlGaN; n 2DEGis the concentration of electrons in the two-dimensional electron gas; ΔP SP is the difference between the spontaneous polarization of GaN and the spontaneous polarization of AlGaN; e ij and C ij are the piezoelectric coefficient and the elastic constant of AlGaN, respectively, i.e. e 31 and e 33 are the piezoelectric coefficient and the elastic constant of AlGaN, respectively, i.e. e 13 and C 33 are the piezoelectric coefficient and the elastic constant of AlGaN, respectively.

[0062] The Poisson equation describing the charge distribution in the AlGaN / GaN heterostructure can then be expressed as equation (2) as follows:

[0063]

[0064] wherein ε 11 and ε 33 are the components of the dielectric constant in the form of a second-rank tensor of the material in the direction perpendicular to the c-axis and in the direction parallel to the c-axis, respectively; represents the electrostatic potential; the charge ρ includes free charge and ionic charge; P is the polarization intensity; e 33 is the piezoelectric coefficient of AlGaN; C 33 is the elastic constant of AlGaN.

[0065] For AlGaN / GaN heterojunction materials, there are a large number of negative polarization charges on the surface, and if these negative polarization charges are not compensated by positive charges, the 2DEG near the AlGaN / GaN interface will be completely depleted. It is generally believed that these negative polarization charges are compensated by the donor-like surface states ionized on the surface of the AlGaN / GaN heterojunction, and the electrons ionized gather near the AlGaN / GaN heterojunction interface to form 2DEG. In the present application, the surface donor state distribution n surface of the AlGaN / GaN heterojunction material is set as shown in equation (3) as follows:

[0066]

[0067] wherein n is the maximum value of the surface donor state density, and n can be set as 0.5×10 16 cm -2 ·eV -1 ~ 1.5×10 16 cm -2 ·eV -1 , and in the present embodiment, n is preferably 1×10 16 cm -2 ·eV -1 ; E is the energy level; Eg is the band gap; CBM is the energy level of the conduction band bottom at the surface; E sThe distribution range of the surface donor state is determined, which can be set as 0.6; the highest energy level occupied by the surface donor state is set as 1 eV below the conduction band bottom, i.e. Φ c = 1 eV. By adjusting the thickness of the AlGaN barrier layer of each layer, the concentration of free electrons in the first two-dimensional electron gas channel, the second two-dimensional electron gas channel and the third two-dimensional electron gas channel at the AlN / GaN interface in the application is close. For the first AlGaN / AlN / GaN heterojunction 1, the second AlGaN / AlN / GaN heterojunction 2 and the third AlGaN / AlN / GaN heterojunction 3 in the application, they are non-intentionally doped heterojunctions, so the semiconductor structure including the first AlGaN / AlN / GaN heterojunction 1, the second AlGaN / AlN / GaN heterojunction 2 and the third AlGaN / AlN / GaN heterojunction 3 can be an N-type semiconductor structure. The carrier distribution diagram of the semiconductor structure is as shown in Figure 2 , and the energy band distribution diagram of the corresponding semiconductor structure is as shown in Figure 3 , Figure 3 The dashed line is the Fermi level position line; the solid line is the energy band curve of the semiconductor structure. The background carrier concentration of the first AlGaN / AlN / GaN heterojunction 1, the background carrier concentration of the second AlGaN / AlN / GaN heterojunction 2 and the background carrier concentration of the third AlGaN / AlN / GaN heterojunction 3 can be between 0.5×10 16 cm -3 ~1.5×10 16 cm -3 , specifically, the background carrier concentration of the first AlGaN / AlN / GaN heterojunction 1, the background carrier concentration of the second AlGaN / AlN / GaN heterojunction 2 and the background carrier concentration of the third AlGaN / AlN / GaN heterojunction 3 can be 0.5×10 16 cm -3 , 1×10 16 cm -3 or 1.5×10 16 cm -3 , in the embodiment, the background carrier concentration of the first AlGaN / AlN / GaN heterojunction 1, the background carrier concentration of the second AlGaN / AlN / GaN heterojunction 2 and the background carrier concentration of the third AlGaN / AlN / GaN heterojunction 3 are all preferably 1×10 16 cm -3 .

[0068] In one embodiment, please continue to refer to Figure 1, the semiconductor structure further comprises: a substrate 4; a nucleation layer 5 located on the surface of the substrate 4; a buffer layer 6 located on the surface of the nucleation layer 5 away from the substrate 4; a first AlGaN / AlN / GaN heterostructure 1 located on the surface of the buffer layer 6 away from the nucleation layer 5.

[0069] Specifically, the substrate 4 can include but is not limited to a silicon substrate, a silicon carbide substrate or a sapphire substrate; in the embodiment, the substrate 4 adopts a silicon carbide substrate.

[0070] Specifically, the nucleation layer 5 can include but is not limited to a GaN layer or an AlN layer; in the embodiment, the nucleation layer 5 adopts an AlN layer.

[0071] Specifically, the buffer layer 6 can include but is not limited to a GaN layer or an AlN layer; in the embodiment, the buffer layer 6 adopts a GaN layer.

[0072] Specifically, the thickness of the buffer layer 6 can be between 2000-3000nm, for example, 2000nm, 2500nm or 3000nm can be adopted.

[0073] In combination with Figure 1 and in reference to Figure 4 , the application also designs a preparation method of a semiconductor structure, the preparation method of the semiconductor structure comprising:

[0074] S401: forming a first AlGaN / AlN / GaN heterostructure 1, a first two-dimensional electron gas channel existing at the interface between the AlN layer 12 and the GaN layer 11 in the first AlGaN / AlN / GaN heterostructure 1;

[0075] S402: forming a second AlGaN / AlN / GaN heterostructure 2 on the surface of the first AlGaN / AlN / GaN heterostructure 1, a second two-dimensional electron gas channel existing at the interface between the AlN layer 22 and the GaN layer 21 in the second AlGaN / AlN / GaN heterostructure 2;

[0076] S403: forming a third AlGaN / AlN / GaN heterostructure 3 on the surface of the second AlGaN / AlN / GaN heterostructure 2, a third two-dimensional electron gas channel existing at the interface between the AlN layer 32 and the GaN layer 31 in the third AlGaN / AlN / GaN heterostructure 3;

[0077] The difference between the electron concentration in the first two-dimensional electron gas channel, the electron concentration in the second two-dimensional electron gas channel and the electron concentration in the third two-dimensional electron gas channel is less than a preset value.

[0078] Specifically, the semiconductor structure can be Figures 1 to 3 The semiconductor structure in the embodiment, the specific structure of the semiconductor structure is described in the followingFigures 1 to 3 and the related description, which will not be repeated here.

[0079] The method for preparing the semiconductor structure discloses the positional relationship between the first AlGaN / AlN / GaN heterostructure 1, the second AlGaN / AlN / GaN heterostructure 2 and the third AlGaN / AlN / GaN heterostructure 3 and the positions of the first two-dimensional electron gas channel, the second two-dimensional electron gas channel and the third two-dimensional electron gas channel, and the semiconductor structure can be prepared according to the method.

[0080] In one embodiment, the thickness of the AlGaN layer 13 in the formed first AlGaN / AlN / GaN heterostructure 1 is the same as the thickness of the AlGaN layer 33 in the formed third AlGaN / AlN / GaN heterostructure 3, and is smaller than the thickness of the AlGaN layer 23 in the formed second AlGaN / AlN / GaN heterostructure 2.

[0081] Specifically, the thickness of the AlGaN layer 13 in the first AlGaN / AlN / GaN heterostructure 1 and the thickness of the AlGaN layer 33 in the third AlGaN / AlN / GaN heterostructure 3 can include 6-10 nm, for example, 6 nm, 7 nm, 8 nm, 9 nm or 10 nm; in this embodiment, the thickness of the AlGaN layer 13 in the first AlGaN / AlN / GaN heterostructure 1 and the thickness of the AlGaN layer 33 in the third AlGaN / AlN / GaN heterostructure 3 are both 8 nm.

[0082] Specifically, the thickness of the AlGaN layer 23 in the second AlGaN / AlN / GaN heterostructure 2 can include 30-50 nm, for example, 30 nm, 35 nm, 40 nm, 45 nm or 50 nm; in this embodiment, the thickness of the AlGaN layer 23 in the second AlGaN / AlN / GaN heterostructure 2 is 40 nm.

[0083] In one embodiment, the thickness of the GaN layer 11 in the formed first AlGaN / AlN / GaN heterostructure 1, the thickness of the GaN layer 21 in the formed second AlGaN / AlN / GaN heterostructure 2 and the thickness of the GaN layer 31 in the formed third AlGaN / AlN / GaN heterostructure 3 are the same; the thickness of the AlN layer 12 in the formed first AlGaN / AlN / GaN heterostructure 1, the thickness of the AlN layer 22 in the formed second AlGaN / AlN / GaN heterostructure 2 and the thickness of the AlN layer 32 in the formed third AlGaN / AlN / GaN heterostructure 3 are the same.

[0084] Specifically, the thickness of the GaN layer 11 in the first AlGaN / AlN / GaN heterostructure 1, the thickness of the GaN layer 21 in the second AlGaN / AlN / GaN heterostructure 2, and the thickness of the GaN layer 31 in the third AlGaN / AlN / GaN heterostructure 3 can include 8-12 nm, for example, 8 nm, 9 nm, 10 nm, 11 nm or 12 nm can be used; in the embodiment, the thickness of the GaN layer 11 in the first AlGaN / AlN / GaN heterostructure 1, the thickness of the GaN layer 21 in the second AlGaN / AlN / GaN heterostructure 2, and the thickness of the GaN layer 31 in the third AlGaN / AlN / GaN heterostructure 3 are all 10 nm.

[0085] Specifically, the thickness of the AlN layer 12 in the first AlGaN / AlN / GaN heterostructure 1, the thickness of the AlN layer 22 in the second AlGaN / AlN / GaN heterostructure 2, and the thickness of the AlN layer 32 in the third AlGaN / AlN / GaN heterostructure 3 can include 0.5-1.5 nm, for example, 0.5 nm, 0.8 nm, 1 nm, 1.2 nm or 1.5 nm can be used; in the embodiment, the thickness of the AlN layer 12 in the first AlGaN / AlN / GaN heterostructure 1, the thickness of the AlN layer 22 in the second AlGaN / AlN / GaN heterostructure 2, and the thickness of the AlN layer 32 in the third AlGaN / AlN / GaN heterostructure 3 are all 1 nm.

[0086] In one embodiment, the first AlGaN / AlN / GaN heterostructure 1, the second AlGaN / AlN / GaN heterostructure 2 and the third AlGaN / AlN / GaN heterostructure 3 can be epitaxially grown by a metal organic chemical vapor deposition process, the first AlGaN / AlN / GaN heterostructure 1, the second AlGaN / AlN / GaN heterostructure 2 and the third AlGaN / AlN / GaN heterostructure 3 are all unintentionally doped heterostructures, the background carrier concentration of the first AlGaN / AlN / GaN heterostructure 1, the background carrier concentration of the second AlGaN / AlN / GaN heterostructure 2 and the background carrier concentration of the third AlGaN / AlN / GaN heterostructure 3 are all 0.5×10 16 cm -3 -1.5×10 16 cm -3 .

[0087] Specifically, the background carrier concentration of the first AlGaN / AlN / GaN heterostructure 1, the background carrier concentration of the second AlGaN / AlN / GaN heterostructure 2 and the background carrier concentration of the third AlGaN / AlN / GaN heterostructure 3 can all be 0.5×1016 cm -3 , 1 x 10 16 cm -3 or 1.5 x 10 16 cm -3 , etc.

[0088] Specifically, the background carrier concentration of the first AlGaN / AlN / GaN heterostructure 1, the background carrier concentration of the second AlGaN / AlN / GaN heterostructure 2 and the background carrier concentration of the third AlGaN / AlN / GaN heterostructure 3 can be 0.5 x 10 16 cm -3 , 1 x 10 16 cm -3 or 1.5 x 10 16 cm -3 In the embodiment, the background carrier concentration of the first AlGaN / AlN / GaN heterostructure 1, the background carrier concentration of the second AlGaN / AlN / GaN heterostructure 2 and the background carrier concentration of the third AlGaN / AlN / GaN heterostructure 3 are preferably 1 x 10 16 cm -3 .

[0089] Continuing to refer to Figure 5 In one embodiment, the method further comprises, before forming the first AlGaN / AlN / GaN heterostructure 1:

[0090] providing a substrate 4;

[0091] forming a nucleation layer 5 on the surface of the substrate 4;

[0092] forming a buffer layer 6 on the surface of the nucleation layer 5 away from the substrate 4; and forming the first AlGaN / AlN / GaN heterostructure 1 on the surface of the buffer layer 6 away from the nucleation layer 5.

[0093] That is, as shown in Figure 5 the method for preparing the semiconductor structure in the embodiment comprises the following steps:

[0094] S501: providing a substrate 4;

[0095] S502: forming a nucleation layer 5 on the surface of the substrate 4;

[0096] S503: forming a buffer layer 6 on the surface of the nucleation layer 5 away from the substrate 4;

[0097] S504: a first AlGaN / AlN / GaN heterostructure 1 is formed on the surface of the buffer layer 6 away from the nucleation layer 5; a first two-dimensional electron gas channel exists at the interface between the AlN layer 12 and the GaN layer 11 in the first AlGaN / AlN / GaN heterostructure 1;

[0098] S505: a second AlGaN / AlN / GaN heterostructure 2 is formed on the surface of the first AlGaN / AlN / GaN heterostructure 1; a second two-dimensional electron gas channel exists at the interface between the AlN layer 22 and the GaN layer 21 in the second AlGaN / AlN / GaN heterostructure 2;

[0099] S506: a third AlGaN / AlN / GaN heterostructure 3 is formed on the surface of the second AlGaN / AlN / GaN heterostructure 2; a third two-dimensional electron gas channel exists at the interface between the AlN layer 32 and the GaN layer 31 in the third AlGaN / AlN / GaN heterostructure 3;

[0100] The difference between the electron concentration in the first two-dimensional electron gas channel, the electron concentration in the second two-dimensional electron gas channel, and the electron concentration in the third two-dimensional electron gas channel is less than a preset value.

[0101] In one of the embodiments, the electron concentration in the first two-dimensional electron gas channel, the electron concentration in the second two-dimensional electron gas channel, and the electron concentration in the third two-dimensional electron gas channel are all the same.

[0102] Specifically, to make the electron concentration in the first two-dimensional electron gas channel, the electron concentration in the second two-dimensional electron gas channel, and the electron concentration in the third two-dimensional electron gas channel the same, and based on the process error consideration, it is necessary to make the difference between the electron concentration in the first two-dimensional electron gas channel, the electron concentration in the second two-dimensional electron gas channel, and the electron concentration in the third two-dimensional electron gas channel as small as possible, i.e., the preset value is as small as possible.

[0103] Specifically, the substrate 4 can include a silicon substrate, a silicon carbide substrate, or a sapphire substrate; in the embodiment, the substrate 4 adopts the silicon carbide substrate.

[0104] Specifically, the nucleation layer 5 can include a GaN layer or an AlN layer; in the embodiment, the nucleation layer 5 adopts the AlN layer.

[0105] Specifically, the buffer layer 6 can include a GaN layer or an AlN layer; in the embodiment, the buffer layer 6 adopts the GaN layer.

[0106] Specifically, the thickness of the buffer layer 6 can be between 2000-3000 nm, for example, 2000 nm, 2500 nm, or 3000 nm can be adopted.

[0107] The semiconductor structure and the preparation method of the semiconductor structure, wherein the semiconductor structure comprises a first AlGaN / AlN / GaN heterostructure 1, a second AlGaN / AlN / GaN heterostructure 2 and a third AlGaN / AlN / GaN heterostructure 3, and a first two-dimensional electron gas channel exists at the interface between the AlN layer 12 and the GaN layer 11 in the first AlGaN / AlN / GaN heterostructure 1; a second two-dimensional electron gas channel exists at the interface between the AlN layer 22 and the GaN layer 21 in the second AlGaN / AlN / GaN heterostructure 2; a third two-dimensional electron gas channel exists at the interface between the AlN layer 32 and the GaN layer 31 in the third AlGaN / AlN / GaN heterostructure 3; the difference between the electron concentration in the first two-dimensional electron gas channel, the electron concentration in the second two-dimensional electron gas channel and the electron concentration in the third two-dimensional electron gas channel is less than a preset value, so as to achieve the purposes of reducing the device resistance value, reducing the reverse leakage current and reducing the heat generation in the working state of the device. The application also discloses a preparation method of the semiconductor structure, which discloses the positional relationship among the first AlGaN / AlN / GaN heterostructure 1, the second AlGaN / AlN / GaN heterostructure 2 and the third AlGaN / AlN / GaN heterostructure 3, the positional relationship among the layers of each heterostructure and the position of each two-dimensional electron gas channel, and the above semiconductor structure can be prepared according to the method.

[0108] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, but as long as the combinations of the technical features do not conflict, they should be considered within the scope of the present disclosure.

[0109] The above-described embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, a number of variations and improvements can be made, which are within the scope of the present application. Therefore, the scope of protection of the present application should be subject to the appended claims.

Claims

1. A semiconductor structure, characterized in that, The semiconductor structure includes: The first AlGaN / AlN / GaN heterostructure has a first two-dimensional electron gas channel at the interface between the AlN layer and the GaN layer. The second AlGaN / AlN / GaN heterostructure has a second two-dimensional electron gas channel at the interface between the AlN layer and the GaN layer. The third AlGaN / AlN / GaN heterostructure has a third two-dimensional electron gas channel at the interface between the AlN layer and the GaN layer. The difference between the electron concentration in the first two-dimensional electron gas channel, the electron concentration in the second two-dimensional electron gas channel, and the electron concentration in the third two-dimensional electron gas channel is less than a preset value; Wherein, the thickness of the AlGaN layer in the first AlGaN / AlN / GaN heterostructure and the thickness of the AlGaN layer in the third AlGaN / AlN / GaN heterostructure are 6nm~10nm, and the thickness of the AlGaN layer in the second AlGaN / AlN / GaN heterostructure is 30nm~50nm; The thickness of the AlN layer in the first AlGaN / AlN / GaN heterostructure, the thickness of the AlN layer in the second AlGaN / AlN / GaN heterostructure, and the thickness of the AlN layer in the third AlGaN / AlN / GaN heterostructure are 0.5 nm to 1.5 nm. The thickness of the GaN layer in the first AlGaN / AlN / GaN heterostructure, the thickness of the GaN layer in the second AlGaN / AlN / GaN heterostructure, and the thickness of the GaN layer in the third AlGaN / AlN / GaN heterostructure are 8nm~12nm; The background carrier concentrations of the first AlGaN / AlN / GaN heterostructure, the second AlGaN / AlN / GaN heterostructure, and the third AlGaN / AlN / GaN heterostructure are all 0.5 × 10⁻⁶. 16 cm -3 ~1.5×10 16 cm -3 .

2. The semiconductor structure according to claim 1, characterized in that, The thickness of the AlGaN layer in the first AlGaN / AlN / GaN heterostructure is the same as the thickness of the AlGaN layer in the third AlGaN / AlN / GaN heterostructure, and both are less than the thickness of the AlGaN layer in the second AlGaN / AlN / GaN heterostructure.

3. The semiconductor structure according to claim 2, characterized in that, The thickness of the GaN layer in the first AlGaN / AlN / GaN heterostructure, the thickness of the GaN layer in the second AlGaN / AlN / GaN heterostructure, and the thickness of the GaN layer in the third AlGaN / AlN / GaN heterostructure are the same; the thickness of the AlN layer in the first AlGaN / AlN / GaN heterostructure, the thickness of the AlN layer in the second AlGaN / AlN / GaN heterostructure, and the thickness of the AlN layer in the third AlGaN / AlN / GaN heterostructure are the same.

4. The semiconductor structure according to claim 1, characterized in that, The first AlGaN / AlN / GaN heterostructure, the second AlGaN / AlN / GaN heterostructure, and the third AlGaN / AlN / GaN heterostructure are all unintentionally doped heterostructures.

5. The semiconductor structure according to any one of claims 1 to 4, characterized in that, The semiconductor structure also includes: Substrate; Nucleation layer, located on the surface of the substrate; A buffer layer is located on the surface of the nucleation layer away from the substrate; the first AlGaN / AlN / GaN heterostructure is located on the surface of the buffer layer away from the nucleation layer.

6. A method for fabricating a semiconductor structure, characterized in that, The method for preparing the semiconductor structure includes: A first AlGaN / AlN / GaN heterostructure is formed, wherein a first two-dimensional electron gas channel exists at the interface between the AlN layer and the GaN layer in the first AlGaN / AlN / GaN heterostructure. A second AlGaN / AlN / GaN heterostructure is formed on the surface of the first AlGaN / AlN / GaN heterostructure, and a second two-dimensional electron gas channel exists at the interface between the AlN layer and the GaN layer in the second AlGaN / AlN / GaN heterostructure. A third AlGaN / AlN / GaN heterostructure is formed on the surface of the second AlGaN / AlN / GaN heterostructure, and a third two-dimensional electron gas channel exists at the interface between the AlN layer and the GaN layer in the third AlGaN / AlN / GaN heterostructure. The difference between the electron concentration in the first two-dimensional electron gas channel, the electron concentration in the second two-dimensional electron gas channel, and the electron concentration in the third two-dimensional electron gas channel is less than a preset value; Wherein, the thickness of the AlGaN layer in the first AlGaN / AlN / GaN heterostructure and the thickness of the AlGaN layer in the third AlGaN / AlN / GaN heterostructure are 6nm~10nm, and the thickness of the AlGaN layer in the second AlGaN / AlN / GaN heterostructure is 30nm~50nm; The thickness of the AlN layer in the first AlGaN / AlN / GaN heterostructure, the thickness of the AlN layer in the second AlGaN / AlN / GaN heterostructure, and the thickness of the AlN layer in the third AlGaN / AlN / GaN heterostructure are 0.5 nm to 1.5 nm. The thickness of the GaN layer in the first AlGaN / AlN / GaN heterostructure, the thickness of the GaN layer in the second AlGaN / AlN / GaN heterostructure, and the thickness of the GaN layer in the third AlGaN / AlN / GaN heterostructure are 8nm~12nm; The background carrier concentrations of the first AlGaN / AlN / GaN heterostructure, the second AlGaN / AlN / GaN heterostructure, and the third AlGaN / AlN / GaN heterostructure are all 0.5 × 10⁻⁶. 16 cm -3 ~1.5×10 16 cm -3 .

7. The method for preparing a semiconductor structure according to claim 6, characterized in that, The thickness of the AlGaN layer in the first AlGaN / AlN / GaN heterostructure is the same as the thickness of the AlGaN layer in the third AlGaN / AlN / GaN heterostructure, and both are less than the thickness of the AlGaN layer in the second AlGaN / AlN / GaN heterostructure.

8. The method for preparing a semiconductor structure according to claim 7, characterized in that, The thickness of the GaN layer in the first AlGaN / AlN / GaN heterostructure, the thickness of the GaN layer in the second AlGaN / AlN / GaN heterostructure, and the thickness of the GaN layer in the third AlGaN / AlN / GaN heterostructure are the same; the thickness of the AlN layer in the first AlGaN / AlN / GaN heterostructure, the thickness of the AlN layer in the second AlGaN / AlN / GaN heterostructure, and the thickness of the AlN layer in the third AlGaN / AlN / GaN heterostructure are the same.

9. The method for preparing a semiconductor structure according to claim 6, characterized in that, The first AlGaN / AlN / GaN heterostructure, the second AlGaN / AlN / GaN heterostructure, and the third AlGaN / AlN / GaN heterostructure are epitaxially grown using metal-organic chemical vapor deposition (MOCVD). All three AlGaN / AlN / GaN heterostructures are unintentionally doped heterostructures.

10. The method for preparing a semiconductor structure according to any one of claims 6 to 9, characterized in that, The process prior to forming the first AlGaN / AlN / GaN heterostructure also includes: Provide substrate; A nucleation layer is formed on the surface of the substrate; A buffer layer is formed on the surface of the nucleation layer away from the substrate; the first AlGaN / AlN / GaN heterostructure is formed on the surface of the buffer layer away from the nucleation layer.

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