CN111682093A - A kind of gallium nitride epitaxial chip and preparation method thereof - Google Patents

Abstract

The invention relates to a gallium nitride epitaxial chip and a preparation method thereof, wherein the gallium nitride epitaxial chip comprises a substrate, a seed layer, a buffer layer and a gallium nitride epitaxial layer, wherein the seed layer is arranged on the substrate, and the buffer layer is arranged on the substrate. between the seed layer and the gallium nitride epitaxial layer. In the present invention, a seed layer and a buffer layer are added between the substrate and the gallium nitride epitaxial layer, so as to improve the matching of characteristics such as lattice coefficient and thermal expansion coefficient between the gallium nitride and the substrate, so as to ensure the nitrided nitride. In the case of gallium lattice dislocation density, the growth thickness of gallium nitride can be increased.

Description

A kind of gallium nitride epitaxial chip and preparation method thereof

technical field

The invention relates to the field of semiconductor materials, in particular to a gallium nitride epitaxial chip and a preparation method thereof.

Background technique

At present, III/V nitride semiconductor materials mainly include GaN (gallium nitride), InGaN (indium gallium nitride) and AlGaN (aluminum gallium nitride). Such materials are used in optoelectronic devices, semiconductor laser devices, light-emitting diodes, high electron mobility transistors, and the like. The energy gap characteristics of nitride semiconductor materials can be continuously modulated (non-staged) between 1.9 and 6.2ev. It has good physical and chemical stability and high saturation electron mobility, and is an ideal material for high-power, high-frequency, light-emitting devices.

Gallium nitride single crystals do not exist in nature and cannot be obtained from nature, so they must be manufactured artificially. The current manufacturing method is to find a single crystal material as the basis, called the substrate substrate, and then grow a gallium nitride film on the substrate substrate. Because of the different substrate materials, there is no way to perfectly match. Cracks are prone to occur during thermal expansion, and dislocations in the substrate material are brought into the GaN layer and amplified. Therefore, some studies have proposed to use other materials to grow an aluminum nitride AlN buffer layer in the middle to solve the problem.

It is difficult to grow GaN GaN with a thickness of 1 micron or more in the existing buffer layer, and at the same time, the dislocation densities of atoms in the GaN GaN lattice layer can be obtained with a mass below 5× ^{10 8} /cm ² .

SUMMARY OF THE INVENTION

In view of the problems existing in the prior art, the purpose of the present invention is to provide a gallium nitride crystal epitaxial wafer and a preparation method thereof, which can improve the growth of gallium nitride while ensuring the dislocation density of the gallium nitride crystal lattice. thickness.

For achieving the above object, the technical scheme adopted in the present invention is:

A gallium nitride epitaxial chip, comprising a substrate, a seed layer, a buffer layer and a gallium nitride epitaxial layer, the seed layer is arranged on the substrate, and the buffer layer is arranged between the seed layer and the gallium nitride epitaxial layer between;

The buffer layer includes more than one set of composite layers, the composite layers include an AlxGa1 _{- xN} layer and a superlattice layer, and the superlattice layer and the AlxGa1 _{- xN} layer are directed from the seed layer to the layer. The gallium nitride epitaxial layers are stacked in sequence;

The super lattice layer is formed by a composite of an aluminum nitride layer and a gallium nitride layer, and the aluminum nitride layer and the gallium nitride layer are alternately stacked from the seed layer to the gallium nitride epitaxial layer; in the super lattice layer The thickness ratio of the aluminum nitride layer and the gallium nitride layer is y.

In the super lattice layer, the aluminum nitride layer and its adjacent gallium nitride layer form an aluminum gallium pair, each group of super lattice layers includes a plurality of aluminum gallium pairs, and the aluminum nitride layer of each aluminum gallium pair and the The gallium nitride layer thickness ratio is the same and is y.

The number of stacked layers of the aluminum nitride layer and the gallium nitride layer in the super lattice layer is more than 20 layers.

The thickness ratio of the aluminum nitride layer and the gallium nitride layer of the super lattice layer is 0.2-1.9.

The value of _x of the AlxGa1 _- xN layer is 0.2-0.85.

The buffer layer includes more than two groups of composite layers, the x value of the Al _x Ga _1-x N layer in each group of composite layers decreases sequentially from the seed layer to the gallium nitride epitaxial layer, and the super lattice layer in each group of composite layers The thickness of AlN and GaN is gradually less than y from the seed layer towards GaN.

The value of _x of the AlxGa1 _-xN layer of each composite layer in the buffer layer is equal to twice the thickness ratio y of aluminum nitride and gallium nitride of the superlattice layer of the composite layer, that is, y=2x.

The thickness of the superlattice layer of each composite layer in the buffer layer gradually decreases from the seed layer to the gallium nitride epitaxial layer, and the thickness of the Al _x Ga _1-x N layer of each composite layer is from the seed layer to the gallium nitride epitaxial layer. direction gradually decreases.

In each composite layer of the buffer layer, the thickness of the AlxGa1 _{- xN} layer is smaller than the thickness of the superlattice layer.

Each composite layer of the buffer layer has a thickness of 100-800 nm.

The seed layer is an aluminum nitride layer with a thickness of 100-200 nm.

A method for preparing a gallium nitride epitaxial chip, comprising: growing a seed layer, a buffer layer and a gallium nitride epitaxial layer on a substrate in sequence, the buffer layer comprising N groups of composite layers, and the composite layer comprising Al _x The specific growth process of the Ga _1-x N layer and the superlattice layer is as follows:

growing an aluminum nitride seed layer on the substrate;

Alternately stack more than 20 aluminum nitride layers and gallium nitride layers on the seed layer to form a superlattice layer of the first group of composite layers; continue to grow Al _x1 Ga _1-x2 N layers on the superlattice layer;

On the Al _x1 Ga _1-x1 N layer of the first group of composite layers, more than 20 layers of aluminum nitride layers and gallium nitride layers are alternately stacked to form the superlattice layer of the second group of composite layers; on the superlattice layer Continue to grow the Al _x2 Ga _1-x2 N layer on it;

Continue to grow the superlattice layer and the AlxGa1 _{- xN} layer until the superlattice layer and the _{AlxNGa1 -xN} N layer of the Nth group are formed;

A gallium nitride epitaxial layer is grown on the AlxNGa1 _{-xN N} layer.

The seed layer, the buffer layer and the gallium nitride epitaxial layer are grown by a hydride vapor phase epitaxy method, a molecular beam epitaxy method or an organic metal chemical vapor deposition method.

After adopting the above scheme, the present invention adds a seed layer and a buffer layer between the substrate and the gallium nitride epitaxial layer to improve the matching of characteristics such as lattice coefficient and thermal expansion coefficient between the gallium nitride and the substrate. Specifically, the buffer layer is composed of more than one group of composite layers, and each group of composite layers is composed of an AlxGa1-xN layer and a superlattice layer. By changing the aluminum ratio of the AlxGa1-xN layer and the superlattice layer, the aluminum ratio is Gradually decrease, the proportion of gallium gradually increases, thereby improving the matching degree of lattice coefficient between the substrate and gallium nitride, so as to ensure the dislocation density of gallium nitride lattice arrangement, the growth thickness of gallium nitride can be increased.

Description of drawings

1 is a schematic structural diagram of a gallium nitride epitaxial chip of the present invention;

FIG. 2 is a schematic diagram of the combination of the superlattice SL and the _{AlxNGa1 -xNNN} composite layer in the buffer layer of the present invention.

Label description:

Substrate _{1 ;} seed layer 2 ; gallium nitride epitaxial layer 3 ; buffer layer 4 ; composite layer 41 ; superlattice layer 411 ;

Detailed ways

As shown in FIG. 1 and FIG. 2 , the present invention discloses a gallium nitride epitaxial chip, which can be high-insulation gallium nitride, P-type gallium nitride or N-type gallium nitride. The gallium nitride epitaxial chip includes a substrate 1, a seed layer 2, a buffer layer 4 and a gallium nitride epitaxial layer 3, wherein the seed layer 2 is provided on the substrate 1, and the buffer layer 4 is provided on the seed layer 2 and the gallium nitride. between the epitaxial layers 3 . In the present invention, a seed layer 2 and a buffer layer 4 are added between the substrate 1 and the gallium nitride epitaxial layer 3 to improve the matching of characteristics such as lattice coefficient and thermal expansion coefficient between the gallium nitride and the substrate 1 .

As shown in FIGS. 1 and 2 , the buffer layer 4 includes more than one set of composite layers 41 , the composite layers 41 include an AlxGa1 _{- xN} layer 412 and a superlattice layer 411, the superlattice The layer 411 and the AlxGa1 _{- xN} layer 412 are sequentially stacked from the seed layer 2 to the gallium nitride epitaxial layer 3; the superlattice layer 411 is formed by a composite of an aluminum nitride layer and a gallium nitride layer, and the nitride The aluminum layer and the gallium nitride layer are alternately stacked from the seed layer 2 to the gallium nitride epitaxial layer 3; the thickness ratio of the aluminum nitride layer and the gallium nitride layer in the super lattice layer 411 is y.

In each superlattice layer 411 , the number of stacked layers of the aluminum nitride layer and the gallium nitride layer is more than 20 layers. The aluminum nitride layer and its adjacent gallium nitride layer form an aluminum gallium pair, each group of super lattice layers 411 includes a plurality of aluminum gallium pairs, and the thickness ratio of the aluminum nitride layer and the gallium nitride layer of each aluminum gallium pair is The same, and is y, and its value is 0.2-1.9. And the value of _x of the AlxGa1 _- xN layer 412 in the conforming layer is 0.2-0.85.

When the buffer layer 4 includes more than two sets of composite layers 41, the x value of the AlxGa1 _{- xN} layer 412 in each set of composite layers 41 decreases sequentially from the seed layer 2 to the gallium nitride epitaxial layer 3, and each set of composite layers The thickness ratio y of the superlattice layer 411 of the aluminum nitride and the gallium nitride in the layer 41 is gradually smaller from the seed layer 2 to the gallium nitride. The value of _x of the AlxGa1 _- xN layer 412 of each composite layer 41 in the buffer layer 4 is equal to twice the thickness ratio y of aluminum nitride and gallium nitride of the superlattice layer 411 of the composite layer 41, that is, y =2x.

Further, the thickness of the super lattice layer 411 of each composite layer 41 in the buffer layer 4 gradually decreases from the seed layer 2 to the GaN epitaxial layer 3, and the thickness of the AlxGa1 _{- xN} layer 412 of each composite layer 41 is determined by The seed layer 2 gradually decreases in the direction of the gallium nitride epitaxial layer 3 . And in each composite layer 41 of the buffer layer 4 , the thickness of the AlxGa1 _{- xN} layer 412 is smaller than the thickness of the superlattice layer 411 .

The thickness of each composite layer 41 of the buffer layer 4 is 100-800 nm. The seed layer 2 is an aluminum nitride layer with a thickness of 100-200 nm.

The preparation method of the above-mentioned gallium nitride epitaxial chip is as follows: growing a seed layer 2, a buffer layer 4 and a gallium nitride epitaxial layer 3 on the substrate 1 in sequence, the buffer layer 4 includes N groups of composite layers 41, and the composite layer 41 includes an AlxGa1 _{- xN} layer 412 and a superlattice layer 411, and the specific growth process is as follows:

An aluminum nitride seed layer 2 is grown on a substrate 1; the substrate 1 may use an Al2O3 substrate 1, a SiC substrate 1 or a Si substrate 1.

Alternately stack more than 20 layers of aluminum nitride layers and gallium nitride layers on the seed layer 2 to form the superlattice layer 411 of the first group of composite layers 41; continue to grow Al _x1 Ga _1-x2 N on the superlattice layer Floor;

On the Al _x1 Ga _1-x1 N layer of the first group of composite layers 41, more than 20 layers of aluminum nitride layers and gallium nitride layers are alternately stacked to form super lattice layers 411 of the second group of composite layers 41; The Al _x2 Ga _1-x2 N layer continues to grow on the lattice layer;

Growth of the superlattice layer 411 and the AlxGa1 _{- xN} layer 412 is continued until the superlattice layer 411 and the _{AlxNGa1 -xN} N layer of the Nth group are formed.

A gallium nitride epitaxial layer 3 is grown on the _{AlxNGa1 -xNN} layer.

The above-mentioned growth methods of the seed layer 2 , the buffer layer 4 and the gallium nitride epitaxial layer 3 are hydride vapor phase epitaxy, molecular beam epitaxy or organic metal chemical vapor deposition method.

In order to clarify the content of the present invention, several embodiments will be listed below for detailed description. In these embodiments, the growth of the seed layer 2 , the buffer layer 4 and the gallium nitride epitaxial layer 3 adopts the metal organic chemical vapor deposition method MOCVD.

Example 1

In this embodiment, the gallium nitride epitaxial chip includes a substrate 1, a seed layer 2, a buffer layer 4 and a gallium nitride epitaxial layer 3. The buffer layer 4 includes a set of composite layers 41, and the composite layer 41 includes a super lattice layer 411 and the AlxGa1 _{- xN} layer 412, the super lattice layer 411 is connected to the seed layer 2, and the AlxGa1 _{- xN} layer 412 is connected to the gallium nitride epitaxial layer 3. The number of layers of gallium nitride and aluminum nitride stacked in the superlattice layer 411 is 25 layers, the thickness ratio y of gallium nitride and aluminum nitride is 1.8, and the _x of the AlxGa1 _- xN layer 412 is 0.9 . In this embodiment, the thickness of the superlattice layer 411 is 90 nm, and the thickness of the AlxGa1 _{- xN} layer 412 is 70 nm.

In this embodiment, the growth thickness of the gallium nitride epitaxial layer 3 is 1.2 μm, the dislocation defect density is 1×10 ⁸ cm ² , and there are no other phenomena such as cracks.

Embodiment 2

The difference from the first embodiment is that the buffer layer 4 in this embodiment includes two sets of composite layers 41 , namely a first composite layer and a second composite layer, the first composite layer is connected to the seed layer 2 , and the second composite layer is connected to the gallium nitride. Epitaxial layer 3. The number of stacked aluminum nitride and gallium nitride layers 411 of the first composite layer and the second composite layer is 20, and the _{AlxGa1 - xN} layer 412 of the first composite layer is _{Alx1Ga1- x1} N layer, the AlxGa1 _{- xN} layer 412 of the second composite layer is an _{Alx2Ga1 -x2N} layer. The thickness ratio y1 of the gallium nitride and aluminum nitride of the superlattice layer 411 of the first composite layer was 1.8, and the x1 of the Al _x1 Ga _1-x1 N layer was 0.9. The thickness ratio y1 of gallium nitride and aluminum nitride of the superlattice of the first composite layer was 1.4, and _x1 of the Alx1Ga1 _-x1N layer was 0.7. The thickness of the superlattice layer 411 of the first composite layer is 90 nm, the thickness of the Alx1Ga1 _-x1N layer is 80 nm, the thickness of the superlattice layer 411 of the second composite layer is 70 nm, and the thickness of the _{Alx2Ga1 -x2N layer} is 60 nm.

In this embodiment, the growth thickness of the gallium nitride epitaxial layer 3 is 1.35 μm, the dislocation defect density is 5× ^{10 7} cm ² , and there are no other phenomena such as cracks.

Embodiment 3

Different from the second embodiment, the composite layer 41 of this embodiment further includes a third composite layer, and the number of stacked aluminum nitride and gallium nitride layers in the super lattice layer 411 of the third composite layer is 20 layers. The thickness ratio y3 of gallium nitride and aluminum nitride in the superlattice layer 411 of the third composite layer is 1.2, and _x3 of the Alx3Ga1 _-x3N layer is 0.6. The thickness of the superlattice layer 411 of the first composite layer is 90 nm, and the thickness of the Alx1 Ga1 _{-x1 N} layer is 80 nm; the thickness of the superlattice layer 411 of the second composite layer is 70 nm, and the thickness of the Alx2 Ga1 _{-x2 layer} is 60 nm. ; The thickness of the super lattice layer 411 of the third composite layer is 60 nm, and the thickness of the Al _x3 Ga _1-x3 N layer is 30 nm.

In this embodiment, the growth thickness of the gallium nitride epitaxial layer 3 is 1.5 μm, the dislocation defect density is 5× ^{10 7} cm ² , and there are no other phenomena such as cracks.

Embodiment 4

Different from the third embodiment, the composite layer 41 of this embodiment further includes a fourth composite layer and a fifth composite layer, and the super lattice layers 411 of the fourth composite layer and the fifth composite layer are stacked aluminum nitride and gallium nitride. The number of layers is 20. The thickness ratio y4 of gallium nitride and aluminum nitride of the superlattice layer 411 of the fourth composite layer is 0.8, and _x4 of the Alx4Ga1 _-x4N layer is 0.4. The thickness ratio y5 of gallium nitride and aluminum nitride of the superlattice layer 411 of the fifth composite layer is 0.6, and _x5 of the Alx5Ga1 _-x5N layer is 0.3. The thickness of the super lattice layer 411 of the first composite layer is 90 nm, the thickness of the Al _x1 Ga _1-x1 N layer is 80 nm, and the thickness of the super lattice layer 411 of the second composite layer is 80 nm, and the thickness of the Al _x2 Ga _1-x2 N layer is 80 nm. The thickness of the superlattice layer 411 of the third composite layer is 60nm, the thickness of the _{Alx3Ga1 -x3N layer} is 40nm, the thickness of the superlattice layer 411 of the fourth composite layer is 50nm, the thickness of the _Alx3Ga1- The thickness of the _x3 N layer is 30 nm, the thickness of the superlattice layer 411 of the fifth composite layer is 40 nm, and the thickness of the Al _x3 Ga1 _-x3 N layer is 20 nm.

In this embodiment, the growth thickness of the gallium nitride epitaxial layer 3 is 2 μm, the dislocation defect density is 5× ^{10 7} cm ² , and there are no other phenomena such as cracks.

The above embodiment is compared with the prior art (Comparative Example 1 and Comparative Example 2), and the comparison results are shown in Table 1.

Table 1

Comparative Examples 1 and 2 in Table 1 are the existing gallium nitride epitaxial chips, in which only the seed layer 2 is provided between the substrate 1 and the gallium nitride epitaxial layer 3. It can be seen from the comparative examples 1 and 2 that when the nitrogen When the growth thickness of the gallium nitride epitaxial layer 3 is 0.05 μm, its dislocation defect density is 5× ^{10 10} /cm ² ; when the growth thickness of the gallium nitride epitaxial layer 3 increases to 0.15 μm, the gallium nitride epitaxial layer 3 is mixed with cracks .

The growth thickness of the gallium nitride epitaxial layer 3 of the gallium nitride epitaxial chips according to the embodiments of the present invention is all above 1 μm, and the dislocation defect density is guaranteed to be kept below 5× ^{10 8} /cm ² , and cracks will not occur. Compared with the prior art, the growth thickness of the gallium nitride epitaxial layer 3 and the quality of its lattice dislocation density are effectively improved.

The above are only the embodiments of the present invention and do not limit the technical scope of the present invention. Therefore, any minor modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention still belong to the present invention. within the scope of the technical solution.

Claims (13)

1. A gallium nitride epitaxial chip is characterized in that: the gallium nitride epitaxial layer buffer layer is arranged between the seed layer and the gallium nitride epitaxial layer;

the buffer layer comprises more than one group of composite layers, and the composite layers comprise Al_xGa_1-xN layer and super lattice layer, the super lattice layer and Al_xGa_1-xThe N layers are sequentially overlapped from the seed layer to the gallium nitride epitaxial layer;

the super lattice layer is formed by compounding an aluminum nitride layer and a gallium nitride layer, and the aluminum nitride layer and the gallium nitride layer are alternately stacked from the seed layer to the gallium nitride epitaxial layer; and the thickness ratio of the aluminum nitride layer to the gallium nitride layer in the super crystal lattice layer is y.

2. A gallium nitride epitaxial chip according to claim 1, wherein: in the super lattice layer, the aluminum nitride layer and an adjacent gallium nitride layer form an aluminum-gallium pair, each super lattice layer comprises a plurality of aluminum-gallium pairs, and the thickness ratio of the aluminum nitride layer to the gallium nitride layer of each aluminum-gallium pair is the same and is y.

3. A gallium nitride epitaxial chip according to claim 1, wherein: the stacking number of the aluminum nitride layer and the gallium nitride layer in the super crystal lattice layer is more than 20.

4. A gallium nitride epitaxial chip according to claim 1, wherein: the thickness ratio of the aluminum nitride layer to the gallium nitride layer of the superlattice layer is 0.2-1.9.

5. A gallium nitride epitaxial chip according to claim 1, wherein: the Al is_xGa_1-xThe value of x of the N layer is 0.2-0.85.

6. A gallium nitride epitaxial chip according to claim 1, wherein: the buffer layer comprises more than two groups of composite layers, and Al in each group of composite layers_xGa_1-xThe x value of the N layer is reduced from the seed layer to the gallium nitride epitaxial layer in sequence, and the thickness of the aluminum nitride and the gallium nitride of the super-lattice layer in each group of composite layers is gradually smaller than that of the gallium nitride from the seed layer to the gallium nitride direction.

7. A gallium nitride epitaxial chip according to claim 1 or 6, wherein: al of each composite layer in the buffer layer_xGa_1-xThe value of x for the N layer is equal to twice the ratio of the aluminum nitride and gallium nitride thicknesses of the superlattice layers of the composite layer to y, i.e., y =2 x.

8. A gallium nitride epitaxial chip according to claim 6, wherein: the thickness of the superlattice layer of each composite layer in the buffer layer is gradually reduced from the seed layer to the gallium nitride epitaxial layer, and the Al of each composite layer_xGa_1-xThe thickness of the N layer is gradually reduced from the seed layer to the direction of the gallium nitride epitaxial layer.

9. A gallium nitride epitaxial chip according to claim 8, wherein: in each composite layer of the buffer layer, Al_xGa_1-xThe thickness of the N layer is less than the thickness of the superlattice layer.

10. A gallium nitride epitaxial chip according to claim 1, wherein: the thickness of each composite layer of the buffer layer is 100-800 nm.

11. A gallium nitride epitaxial chip according to claim 1, wherein: the seed layer is an aluminum nitride layer with a thickness of 100-200 nm.

12. A preparation method of a gallium nitride epitaxial chip is characterized by comprising the following steps: a seed layer, a buffer layer and a gallium nitride epitaxial layer are sequentially grown on a substrate, wherein the buffer layer comprises N groups of composite layers, and the composite layers comprise Al_xGa_1-xThe specific growth process of the N layer and the super lattice layer is as follows:

growing an aluminum nitride seed layer on the substrate;

alternately stacking more than 20 aluminum nitride layers and gallium nitride layers on the seed layer to form a super-lattice layer of a first group of composite layers; continued growth of Al on the superlattice layer_x1Ga_1-x2N layers;

al in the first set of composite layers_x1Ga_1-x1Continuously and alternately stacking more than 20 aluminum nitride layers and gallium nitride layers on the N layer to form a super-lattice layer of a second group of composite layers; continued growth of Al on the superlattice layer_x2Ga_1-x2N layers;

continuously growing the super-lattice layer and Al_xGa_1-xN layers until forming a super lattice layer of the Nth group and Al_xNGa_1-xNN layers;

in Al_xNGa_1-xNAnd growing a gallium nitride epitaxial layer on the N layer.

13. A method for preparing a gallium nitride epitaxial chip according to claim 12, characterized in that: the growth method of the seed layer, the buffer layer and the gallium nitride epitaxial layer is a hydride vapor phase epitaxy method, a molecular beam epitaxy method or an organic metal chemical vapor deposition method.

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