Algan film with reduced dislocation density and method for preparing the same

Abstract

The application discloses an AlGaN film with reduced dislocation density and a preparation method thereof, which comprises a sapphire substrate, an AlN nucleation layer, an AlN film layer, a dislocation filtering layer and an AlGaN film layer which are sequentially stacked, wherein the dislocation filtering layer is an AlGaN layer doped with Mg, and the AlGaN film has reduced dislocation density and improved crystal quality, which is beneficial to improving the light-emitting efficiency of a deep ultraviolet LED device.

Description

TECHNICAL FIELD

[0001] The application relates to the field of semiconductor photoelectric technology, in particular to an AlGaN film with reduced dislocation density and a preparation method thereof. BACKGROUND

[0002] For a deep ultraviolet LED, in addition to reasonable device structure design, the light-emitting efficiency is also affected by the dislocation density in the AlGaN material.

[0003] From the perspective of controlling the threading dislocation in the AlGaN, the best substrate material for growing high-quality AlGaN is AlN. Because there is a large lattice mismatch between the AlN and the sapphire substrate, a large amount of threading dislocation density (10-10 cm) often exists in the AlN template, the density determines the quality of the AlGaN, and the density will further extend to the AlGaN and the active region of the device, greatly limiting the performance of the device.

[0004] At present, most deep ultraviolet LEDs are epitaxially grown on a sapphire substrate, and undoped or Si-doped AlN is used as a buffer layer to reduce the threading dislocation from the sapphire substrate. The effect of reducing the dislocation density is not good, and the crystal quality is not good. SUMMARY

[0005] Therefore, the application provides an AlGaN film with reduced dislocation density and a preparation method thereof, which effectively reduces the dislocation density of the AlGaN film, improves the crystal quality, and is beneficial to improving the light-emitting efficiency of the deep ultraviolet LED device.

[0006] To achieve the above technical purposes, the application adopts the following technical solutions:

[0007] In a first aspect, the application provides an AlGaN film with reduced dislocation density, which comprises a sapphire substrate, an AlN nucleation layer, an AlN film layer, a dislocation filtering layer and an AlGaN film layer which are sequentially stacked, and the dislocation filtering layer is an AlGaN layer doped with Mg.

[0008] Preferably, in the AlGaN layer, the doping concentration of Mg is 1E15-1E19 cm -3 .

[0009] Preferably, the AlGaN layer comprises one of an AlGaN single-layer structure or an Al x Ga 1-x N / Al y Ga 1-y N composite layer structure, wherein 10%≤x≤100%, 0.1%≤y≤90%, and x>y.

[0010] Preferably, the Al x Ga 1-xN / Al y Ga 1-y N complex layer structure, Al x Ga 1-x N layer and / or Al y Ga 1-y N layer is doped with Mg.

[0011] Preferably, Al x Ga 1-x N / Al y Ga 1-y N complex layer structure, Al x Ga 1-x N layer and Al y Ga 1-y N layer is doped with Mg.

[0012] Preferably, in the AlGaN single layer structure, the whole layer or part of the layer is doped with Mg.

[0013] Preferably, the doping method of Mg includes one of uniform doping, intermittent δ-doping.

[0014] Preferably, in the AlGaN single layer structure in which part of the layer is doped with Mg, the doping position of Mg is close to the ALN thin film layer and away from the AlGaN thin film layer.

[0015] Preferably, the number of intermittent δ-doping of Mg is greater than or equal to 1.

[0016] In a second aspect, the application provides a method for preparing an AlGaN thin film with reduced dislocation density, comprising the following steps: using MOCVD process, epitaxially growing AlN nucleation layer, AlN thin film, dislocation filtering layer doped with Mg, and AlGaN thin film layer on a sapphire substrate in sequence.

[0017] The beneficial effects of the application are as follows: the application inserts a dislocation filtering layer between the AlN and the n-type AlGaN thin film layer, and a small amount of Mg is introduced during the growth of the dislocation filtering layer. Since the atomic diameter of Mg is larger than that of Al, and Mg can exist in the interstitial position of AlGaN material, it can effectively block the penetration of dislocations from the AlN layer to the AlGaN thin film layer, reduce the dislocation density of the AlGaN thin film, improve the crystal quality, and ultimately improve the light-emitting efficiency of the deep ultraviolet LED device. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a schematic diagram of the structure of the AlGaN thin film of the application;

[0019] Figure 2 is a schematic diagram of the structure of the AlGaN single layer structure uniformly doped with Mg throughout the layer;

[0020] Figure 3 Structure diagram of AlGaN single layer structure with Mg doped in whole layer intermittently;

[0021] Figure 4 Structure diagram of AlGaN single layer structure with Mg doped in partial layer uniformly;

[0022] Figure 5 Structure diagram of AlGaN single layer structure with Mg doped in partial layer intermittently;

[0023] Figure 6 Structure diagram of AlGaN single layer structure with Mg doped in high component; x Ga 1-x N / Al y Ga 1-y N composite structure dislocation filter layer;

[0024] Figure 7 Structure diagram of AlGaN single layer structure with Mg doped in low component; x Ga 1-x N / Al y Ga 1-y N composite structure dislocation filter layer;

[0025] Figure 8 Structure diagram of AlGaN single layer structure with Mg doped in whole layer uniformly; x Ga 1-x N / Al y Ga 1-y N composite structure dislocation filter layer;

[0026] Figure 9 Structure diagram of dislocation filter layer with interface doping in composite structure. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0028] In a first aspect, the present application provides an AlGaN film with reduced dislocation density, which comprises a buffer layer and a AlGaN layer on the buffer layer, wherein the AlGaN layer is doped with Mg. Figure 1As shown, including the sapphire substrate, AlN nucleation layer, AlN film layer, dislocation filtering layer, AlGaN film layer, the dislocation filtering layer is Mg doped AlGaN layer, wherein the AlGaN film is n-type AlGaN film, the sapphire substrate is C-sapphire substrate, the thickness of the AlN nucleation layer is 2nm-30nm, for example, 2nm, 6nm, 10nm, 20nm, 30m, the thickness of the AlN film layer is 100-4000nm, for example, 100nm, 300nm, 500nm, 1000nm, 2000nm, 3000nm, 4000nm, by inserting a dislocation filtering layer between the AlN and the n-type AlGaN film layer, a small amount of Mg is introduced during the growth of the dislocation filtering layer, to block the dislocation from penetrating from the AlN layer to the AlGaN film layer, to reduce the dislocation density of the AlGaN film, improve the crystal quality, and ultimately improve the light emitting efficiency of the deep ultraviolet LED device.

[0029] Preferably, the doping concentration of Mg in the AlGaN layer is 1E15-1E19cm -3 .

[0030] According to the different structures of the AlGaN layer, the doping mode and direction of Mg are different, in the present scheme, the structure of the AlGaN layer includes two cases: the AlGaN layer is an AlGaN single layer structure, the Al component of the AlGaN single layer structure accounts for 0.1-100%, the thickness of the AlGaN single layer structure is 1nm-1500nm; the AlGaN layer is an Al x Ga 1-x N / Al y Ga 1-y N composite layer, which is a periodic layer structure, wherein 10%≤x≤100%, 0.1%≤y≤90%, and x>y, the thickness of Al x Ga 1-x N is 0.1nm-10nm, the thickness of Al y Ga 1-y N is 0.1nm-15nm, and the period number is 1-50; by adjusting the introduction time of the MO source and the Mg source, the doping mode of Mg includes uniform doping and intermittent δ doping, the intermittent δ doping is a doping process known to those skilled in the art, the thickness of the Mg layer is about 1nm, which is very thin, and the doping direction of Mg includes whole layer doping and partial layer doping, which will be described in detail as follows:

[0031] 1. The AlGaN layer is an AlGaN single layer structure

[0032] Mg-doped AlGaN monolayer structure includes four cases, firstly, Mg-doped is divided into whole layer doping and partial layer doping, secondly, whole layer doping and partial layer doping both include uniform doping and intermittent δ-doping two doping ways.

[0033] It can be understood that whole layer doping is divided into whole layer uniform doping and whole layer intermittent δ-doping two doping ways: as shown in Figure 2 Whole layer uniform doping forms AlGaN+Mg layer structure, as shown in Figure 3 Whole layer intermittent δ-doping forms AlGaN-Mg-AlGaN layer structure, preferably, the number of intermittent δ-doping is greater than or equal to 1 time, that is, the dislocation filtering layer includes a plurality of stacked AlGaN-Mg-AlGaN layer structures, the interval thickness between adjacent intermittent δ-doped Mg is 1 nm-200 nm, more preferably, the AlGaN-Mg-AlGaN layer presents a periodic cyclic structure.

[0034] Partial layer doping refers to that the AlGaN monolayer structure is divided into Mg-doped AlGaN layer and non-Mg-doped AlGaN layer two parts, the Mg-doped AlGaN layer can be located above or below the non-Mg-doped AlGaN layer, the thickness of the Mg-doped AlGaN layer is 1 nm-750 nm, as preferred, the doping position of Mg is close to the ALN thin film layer and far away from the AlGaN thin film layer, that is, the Mg-doped AlGaN layer is located below the non-Mg-doped AlGaN layer, taking the Mg-doped AlGaN layer below the non-Mg-doped AlGaN layer as an example, the doping way of the Mg-doped AlGaN layer therein is also divided into uniform doping and intermittent δ-doping two doping ways: that is, partial layer doping includes partial layer uniform doping forming AlGaN-AlGaN+Mg layer as shown in Figure 4 AlGaN+Mg is Mg uniform doping area, partial layer intermittent δ-doping forming AlGaN-AlGaN-Mg-AlGaN layer as shown in Figure 5 AlGaN-Mg-AlGaN forms Mg δ-doping area, preferably, the number of intermittent δ-doping is greater than or equal to 1 time, that is, the Mg-doped AlGaN layer includes a plurality of stacked AlGaN-Mg-AlGaN layer structures, the interval thickness between adjacent intermittent δ-doped Mg is 1 nm-200 nm, more preferably, the AlGaN-Mg-AlGaN layer presents a periodic cyclic structure.

[0035] 2. AlGaN layer is Al x Ga 1-x N / Al y Ga 1-y N composite layer structure

[0036] According to the numerical limitation of x, y, it is known that in the present scheme, Al x Ga 1-x N represents a high component layer in the composite layer, Al y Ga 1-y N represents a low component layer in the composite layer, Mg-doped Al x Ga 1-x N / Al y Ga 1-y N composite layer structure also includes four cases, because Al x Ga 1-x N / Al y Ga 1-y N composite layer is a cyclic structure, the following examples of the diagram low component layer and high component layer are not limited by the up and down orientation: as shown in Figure 6 , the high component layer is doped with Mg and the low component layer is not doped with Mg; as shown in Figure 7 , the low component layer is doped with Mg and the high component layer is not doped with Mg; as shown in Figure 8 , the high component layer and the low component layer are both doped with Mg; as shown in Figure 9 , the high component layer and the low component layer are both not doped with Mg, but the interface between the high component layer and the low component layer is doped with Mg.

[0037] The present application provides a method for preparing AlGaN film with reduced dislocation density, using MOCVD process, the epitaxial material growth steps are as follows:

[0038] S1. On the sapphire substrate, the growth temperature is reduced to 700-900℃, the V / III ratio is changed to 2000-20000, and the low-temperature AlN nucleation layer with a thickness of 2-30nm is grown;

[0039] S2. The growth temperature is increased to 1100-1400℃, the V / III ratio is reduced to 500-3000, and the AlN film with a thickness of 100-4000nm is grown;

[0040] S3. The growth temperature is reduced to 1000-1300℃, the V / III ratio is increased to 5000-20000, Mg is doped by adjusting the input parameters of MO source and Mg source, and the Mg-doped dislocation filtering layer is grown, the doping concentration of Mg is 1E15-1E19cm -3 ;

[0041] S4. After the growth temperature reaches 1000-1300℃ required for growing AlGaN film, the temperature is maintained unchanged, and the AlGaN film is grown;

[0042] In the scheme, the Mg doping is uniform doping or intermittent δ doping. The steps of intermittent δ doping are as follows: after epitaxially growing the AlN film, the AlGaN of the target thickness is grown under the setting conditions of step S3, the MO source is stopped and the Mg source is connected, the Mg δ doping region is formed, and then the Mg continuous growth is stopped, wherein the Mg connection time is 1s-3000s, and the interval thickness is 1nm-200nm; the steps of uniform doping are as follows: after epitaxially growing the AlN film, the MO source and the Mg source are simultaneously connected under the setting conditions of step S3, and the dislocation filtering layer with uniform Mg doping is formed.

[0043] The scheme is described below through specific examples.

[0044] Example 1

[0045] An AlGaN film with reduced dislocation density, as shown in Figure 1 , comprises a sapphire substrate, an AlN nucleation layer, an AlN film layer, a dislocation filtering layer, and an AlGaN film layer which are sequentially stacked, as shown in Figure 2 , the dislocation filtering layer is an AlGaN single layer structure uniformly doped with Mg.

[0046] The preparation method is as follows:

[0047] S1. On the sapphire substrate, the growth temperature is reduced to 700-900℃, the V / III ratio is changed to 2000-20000, and the low-temperature AlN nucleation layer with a thickness of 2-30nm is grown;

[0048] S2. The growth temperature is increased to 1100-1400℃, the V / III ratio is reduced to 500-3000, and the AlN film with a thickness of 100-4000nm is grown;

[0049] S3. The growth temperature is reduced to 1000-1300℃, the V / III ratio is increased to 5000-20000, and the Mg and MO sources are simultaneously connected to grow the AlGaN single layer dislocation filtering layer uniformly doped with Mg, wherein the thickness of the AlGaN single layer dislocation filtering layer is 500nm, and the doping concentration of Mg is 1E17cm 0.8 . 0.2 0.8 0.2 -3 .

[0050] S4. After the growth temperature reaches 1000-1300℃ required for growing the AlGaN film, the temperature is maintained, and the AlGaN film is grown.

[0051] Example 2

[0052] ​​​An AlGaN film with reduced dislocation density, other structures being the same as in Example 1, except that, as shown in FIG. 2, the dislocation filtering layer is an AlGaN monolayer structure with Mg δ-doped intermittently in the whole layer; Figure 3

[0053] The preparation method is the same as in Example 1, except that, after growing the 250 nm AlGaN layer, the MO source is stopped and the Mg source is introduced, and when the AlGaN film is 250 nm thick, the Mg source is stopped and the AlGaN layer is continuously grown.

[0054] Example 3

[0055] An AlGaN film with reduced dislocation density, other structures being the same as in Example 1, except that, as shown in FIG. 2, the dislocation filtering layer is an AlGaN monolayer structure with Mg δ-doped intermittently in the whole layer; Figure 4

[0056] The preparation method is the same as in Example 1, except that, after step S2, the MO source and the Mg source are introduced at the same time, and when the AlGaN film is 250 nm thick, the Mg source is stopped and the AlGaN layer is continuously grown.

[0057] Example 4

[0058] An AlGaN film with reduced dislocation density, other structures being the same as in Example 1, except that, as shown in FIG. 2, the dislocation filtering layer is an AlGaN monolayer structure with Mg δ-doped intermittently in the whole layer; Figure 5

[0059] The preparation method is the same as in Example 1, except that, after step S2, the MO source is introduced, and after growing the 250 nm AlGaN layer, the MO source is stopped and the Mg source is introduced, and when the AlGaN film is 250 nm thick, the Mg source is stopped and the AlGaN layer is continuously grown.

[0060] Example 5

[0061] An AlGaN film with reduced dislocation density, other structures being the same as in Example 1, except that, as shown in FIG. 2, the dislocation filtering layer is an AlGaN monolayer structure with Mg δ-doped intermittently in the whole layer; Figure 7 0.9 Ga 0.1 N / Al 0.7 Ga 0.3 N composite structure dislocation filtering layer, wherein the thickness of the Al 0.9 Ga 0.1 N is 6 nm, the thickness of the Al 0.7 Ga 0.3 N is 4 nm, and the number of periods of the composite structure is 50. ​​​​

[0062] Example 6

[0063] An AlGaN film with reduced dislocation density, other structures are the same as Example 5, the difference is that, as shown in Figure 6 , the dislocation filtering layer is a high component Mg-doped Al 0.9 Ga 0.1 N / Al 0.7 Ga 0.3 N composite structure dislocation filtering layer.

[0064] Example 7

[0065] An AlGaN film with reduced dislocation density, other structures are the same as Example 5, the difference is that, as shown in Figure 8 , the dislocation filtering layer is a whole layer Mg-doped Al 0.9 Ga 0.1 N / Al 0.7 Ga 0.3 N composite structure dislocation filtering layer.

[0066] Example 8

[0067] An AlGaN film with reduced dislocation density, other structures are the same as Example 5, the difference is that, as shown in Figure 9 , the dislocation filtering layer is a Mg-doped Al 0.9 Ga 0.1 N / Al 0.7 Ga 0.3 N composite structure dislocation filtering layer, wherein Mg is doped in the Al 0.9 Ga 0.1 N and Al 0.7 Ga 0.3 N interface when the growth of the two layers is interrupted;

[0068] Evaluation test

[0069] The AlGaN films in Examples 1-8 were subjected to XRD tests, specifically, the rocking curves of (002) and (102) were tested, and the structure formed by directly growing an ALGaN film on an ALN film was blank group, which did not include a dislocation filtering layer, and the results are shown in Table 1:

[0070] Table 1 XRD rocking curve half-width / arcsec of different materials

[0071]

[0072] From the above results, in examples 1-8, the XRD (002) and XRD (102) half-height width of the material of the dislocation filtering layer doped with Mg is narrower than that of the blank group, which indicates that the crystal quality is better than that of the blank group without dislocation filtering layer structure.

[0073] Similarly, in the single-layer structure, the crystal quality of example 2 is better than that of example 1, and the crystal quality of example 4 is better than that of example 3, which indicates that the intermittent doping of Mg is better than the uniform doping of Mg, and the reason is that the uniform doping will cause a part of Mg impurities to diffuse to the upper AlGaN, thereby reducing the crystal quality of the upper AlGaN to some extent, so that the intermittent doping is better than the uniform doping; the crystal quality of example 3 is better than that of example 1, and the crystal quality of example 4 is better than that of example 2, which indicates that the partial layer doping of Mg is better than the whole layer doping of Mg, and the part close to AlGaN is not doped, which is also to prevent Mg from diffusing to the upper layer.

[0074] Similarly, in the composite structure, the crystal quality of example 8 is better than that of example 6, which indicates that the interface doping of the composite structure is better than the high component layer doping in the composite structure, and the crystal quality of example 6 is better than that of example 8, which indicates that the high component doping in the composite structure is better than the low component layer doping in the composite structure, and the crystal quality of example 8 is better than that of example 7, which indicates that the low component doping in the composite structure is better than the whole layer uniform doping in the composite structure.

[0075] In the present application, a dislocation filtering layer is inserted between the AlN and the n-type AlGaN thin film layer, and a small amount of Mg is introduced during the growth of the dislocation filtering layer. Since the atomic diameter of Mg is larger than that of Al, and Mg can exist in the interstitial position of AlGaN material, it can effectively block the dislocation from penetrating from the AlN layer to the AlGaN thin film layer, reduce the dislocation density of the AlGaN thin film, improve the crystal quality, and finally improve the light-emitting efficiency of the deep ultraviolet LED device.

[0076] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. An AlGaN thin film with reduced dislocation density, characterized in that, The structure comprises a sapphire substrate, an AlN nucleation layer, an AlN thin film layer, a dislocation filtering layer, and an AlGaN thin film layer stacked sequentially. The dislocation filtering layer is an AlGaN layer doped with Mg. The AlGaN layer includes a partially Mg-doped AlGaN monolayer structure, wherein the Mg doping sites are close to the AlN thin film layer and far away from the AlGaN thin film layer.

2. The AlGaN thin film with reduced dislocation density according to claim 1, characterized in that, In the AlGaN layer, the Mg doping concentration is 1E15-1E19 cm⁻¹. -3 .

3. The AlGaN thin film with reduced dislocation density according to claim 1, characterized in that, The doping method of Mg includes one of uniform doping and intermittent delta doping.

4. The AlGaN thin film with reduced dislocation density according to claim 1, characterized in that, The number of times δ-doped Mg is intermittent is greater than or equal to 1.

5. The method for preparing AlGaN thin films with reduced dislocation density according to any one of claims 1-4, characterized in that, The process includes the following steps: using MOCVD technology, an AlN nucleation layer, an AlN thin film, a Mg-doped dislocation filter layer, and an AlGaN thin film layer are epitaxially grown sequentially on a sapphire substrate.

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