CN109192827B - A kind of gallium nitride-based light-emitting diode epitaxial wafer and its growth method - Google Patents

Abstract

The invention discloses a gallium nitride-based light-emitting diode epitaxial wafer and a growth method thereof, belonging to the technical field of semiconductors. The gallium nitride-based light-emitting diode epitaxial wafer includes a substrate, a buffer layer, an N-type semiconductor layer, an active layer and a P-type semiconductor layer, the buffer layer, the N-type semiconductor layer, the active layer and the The P-type semiconductor layers are sequentially stacked on the substrate, the material of the buffer layer is aluminum nitride doped with oxygen, and the doping concentration of oxygen in the part of the buffer layer close to the substrate is greater than that of the buffer layer Doping concentration of oxygen in a portion of the layer close to the N-type semiconductor layer. In the present invention, oxygen is doped into aluminum nitride, the material of the buffer layer, and the doping concentration of oxygen in the part of the buffer layer close to the substrate is greater than the doping concentration of oxygen in the part of the buffer layer close to the N-type semiconductor layer, so as to realize The gradual transition of two different lattices from sapphire to GaN-based materials effectively alleviates the lattice mismatch between sapphire and GaN-based materials.

Description

A kind of gallium nitride-based light-emitting diode epitaxial wafer and its growth method

technical field

The invention relates to the technical field of semiconductors, in particular to a gallium nitride-based light-emitting diode epitaxial wafer and a growth method thereof.

Background technique

Light Emitting Diode (English: Light Emitting Diode, LED for short) is a semiconductor electronic component that can emit light. As an important third-generation semiconductor material, gallium nitride (GaN)-based materials have broad application prospects in the fields of semiconductor lighting, power electronics, and high-frequency communications. Since the 1990s, GaN-based light-emitting diodes have been gradually commercialized, filling the gap of traditional light-emitting diodes in the blue light band.

The epitaxial wafer is the primary product in the light-emitting diode manufacturing process. The existing gallium nitride-based LED epitaxial wafer includes a substrate, an N-type semiconductor layer, an active layer and a P-type semiconductor layer, and the N-type semiconductor layer, the active layer and the P-type semiconductor layer are sequentially stacked on the substrate. The P-type semiconductor layer is used to provide holes for recombination emission, the N-type semiconductor layer is used to provide electrons for recombination emission, the active layer is used for radiative recombination emission of electrons and holes, and the substrate is used to provide epitaxial materials growth surface.

The material of the substrate is usually sapphire, the N-type semiconductor layer, the active layer and the P-type semiconductor layer are made of gallium nitride-based materials, and the lattice difference between sapphire and gallium nitride-based materials is large. In order to obtain better material quality and higher production efficiency, in the current mainstream GaN-based light-emitting diode epitaxial wafer fabrication process, it is usually necessary to pre-grow nitrogen on a sapphire substrate (the main component is Al ₂ O ₃ ). Aluminum nitride buffer layer, the introduction of aluminum nitride buffer layer can bring stress relief for gallium nitride-based materials, provide nucleation centers, etc., to achieve the transition of the lattice structure. However, the aluminum nitride buffer layer currently used in the mainstream technology is a single-layer structure in which each component is evenly distributed, and the potential of the aluminum nitride buffer layer to improve the performance of the gallium nitride-based light-emitting diode cannot be fully utilized.

SUMMARY OF THE INVENTION

The embodiments of the present invention provide a gallium nitride-based light-emitting diode epitaxial wafer and a growth method thereof, which can solve the problem that the prior art cannot fully utilize the performance improvement potential brought by the aluminum nitride buffer layer to the gallium-nitride-based light-emitting diode. question. The technical solution is as follows:

In one aspect, an embodiment of the present invention provides a gallium nitride-based light-emitting diode epitaxial wafer, the gallium nitride-based light-emitting diode epitaxial wafer includes a substrate, a buffer layer, an N-type semiconductor layer, an active layer, and a P-type semiconductor layer , the buffer layer, the N-type semiconductor layer, the active layer and the P-type semiconductor layer are sequentially stacked on the substrate, and the material of the buffer layer is aluminum nitride doped with oxygen, so The doping concentration of oxygen in the portion of the buffer layer close to the substrate is greater than the doping concentration of oxygen in the portion of the buffer layer close to the N-type semiconductor layer.

Optionally, the buffer layer has a single-layer structure, and the doping concentration of oxygen in the single-layer structure gradually decreases along the stacking direction of the gallium nitride-based light-emitting diode epitaxial wafers.

Optionally, the buffer layer is a stacked structure, and the doping concentration of oxygen in the stacked structure decreases layer by layer along the stacking direction of the gallium nitride-based light emitting diode epitaxial wafer.

Preferably, the maximum value of the molar concentration of oxygen in the buffer layer is 3%-20%, and the minimum value of the molar concentration of oxygen in the buffer layer is 0%-8%.

Optionally, the thickness of the buffer layer is 5 nm˜100 nm.

On the other hand, an embodiment of the present invention provides a method for growing a gallium nitride-based light-emitting diode epitaxial wafer, the growth method comprising:

providing a substrate;

growing a buffer layer on the substrate;

growing an N-type semiconductor layer, an active layer and a P-type semiconductor layer in sequence on the buffer layer;

Wherein, the material of the buffer layer is aluminum nitride doped with oxygen, and the doping concentration of oxygen in the part of the buffer layer close to the substrate is greater than that in the part of the buffer layer close to the N-type semiconductor layer doping concentration.

Optionally, the growing of the buffer layer on the substrate includes:

placing the substrate in a reaction chamber of a growth apparatus;

Pour nitrogen and oxygen into the reaction chamber, and grow a buffer layer on the substrate, the buffer layer is a single-layer structure, the volume of the nitrogen gas introduced during the growth of the single-layer structure is unchanged, and the The volume of oxygen gradually decreases.

Optionally, the growing of the buffer layer on the substrate includes:

placing the substrate in a reaction chamber of a growth apparatus;

Pour nitrogen and oxygen into the reaction chamber, and grow a buffer layer on the substrate. The buffer layer is a laminated structure. The volume of nitrogen gas introduced during the growth of the laminated structure is unchanged, and the buffer layer is passed through. The volume of oxygen decreases layer by layer.

Preferably, the maximum value of the flow rate of oxygen during the growth of the buffer layer is 2.5% to 10% of the flow rate of nitrogen during the growth of the buffer layer, and the minimum value of the flow rate of oxygen during the growth of the buffer layer is 2.5% to 10% of the flow rate of the nitrogen gas during the growth of the buffer layer. 0% to 5% of the nitrogen flow rate.

Preferably, the power of the growth apparatus for growing the portion of the buffer layer close to the substrate is less than the power of the growth apparatus for growing the portion of the buffer layer close to the N-type semiconductor layer.

The beneficial effects brought by the technical solutions provided in the embodiments of the present invention are:

Oxygen is doped into aluminum nitride through the material of the buffer layer, and the doping concentration of oxygen in the part of the buffer layer close to the substrate is greater than the doping concentration of oxygen in the part of the buffer layer close to the N-type semiconductor layer; the buffer layer is close to the substrate The doping concentration of oxygen in the part of the buffer layer is relatively high, which is relatively matched with the lattice of sapphire whose main component is Al ₂ O ₃ ; at the same time, the doping concentration of oxygen in the part of the buffer layer close to the N-type semiconductor layer is small, which is similar to that of nitrogen. Lattice comparison between gallium-based materials. The buffer layer is arranged between the substrate using sapphire and the N-type semiconductor layer using GaN-based materials, which can realize the gradual transition from sapphire to GaN-based materials with two different lattices, and effectively alleviate sapphire and GaN-based materials. The lattice mismatch between the base materials can fully release the stress caused by the lattice mismatch between the sapphire and the GaN-based material, improve the defects caused by the lattice mismatch between the sapphire and the GaN-based material, and gradually reduce the position Dislocation density and crystallinity become better, greatly improve the crystal quality of epitaxial wafers, reduce the polarization of the active layer, improve the internal quantum efficiency, brightness and luminous efficiency of LEDs, at the same time reduce the reverse leakage of LEDs, and enhance the antistatic ability of LEDs .

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative effort.

1 is a schematic structural diagram of a gallium nitride-based light-emitting diode epitaxial wafer provided by an embodiment of the present invention;

2 is a schematic structural diagram of a buffer layer provided by an embodiment of the present invention;

3 is a schematic structural diagram of another buffer layer provided by an embodiment of the present invention;

4 is a flowchart of a method for growing a GaN-based light-emitting diode epitaxial wafer according to an embodiment of the present invention;

5 is a schematic diagram of a variation of the volume of oxygen supplied during the growth of the buffer layer provided by an embodiment of the present invention;

FIG. 6 is a schematic diagram of another variation of the volume of oxygen gas supplied when the buffer layer is grown according to an embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

An embodiment of the present invention provides a gallium nitride-based light-emitting diode epitaxial wafer. FIG. 1 is a schematic structural diagram of a gallium nitride-based light-emitting diode epitaxial wafer provided by an embodiment of the present invention. Referring to FIG. 1, the gallium nitride-based light-emitting diode The diode epitaxial wafer includes a substrate 10, a buffer layer 20, an N-type semiconductor layer 30, an active layer 40 and a P-type semiconductor layer 50. The buffer layer 20, the N-type semiconductor layer 30, the active layer 40 and the P-type semiconductor layer 50 are in sequence Laminated on the substrate 10 .

In this embodiment, the material of the buffer layer 20 is aluminum nitride doped with oxygen, and the doping concentration of oxygen in the part of the buffer layer 20 close to the substrate 10 is higher than that of the part of the buffer layer 20 close to the N-type semiconductor layer 30 doping concentration.

Since the doping concentration of oxygen in the portion of the buffer layer 20 close to the substrate 10 is greater than the doping concentration of oxygen in the portion of the buffer layer 20 close to the N-type semiconductor layer 30 , the lattice constant of the portion of the buffer layer 20 close to the substrate 10 is less than The lattice constant of the portion of the buffer layer 20 close to the N-type semiconductor layer 30 while the dislocation density of the portion of the buffer layer 20 close to the substrate 10 is higher than the dislocation density of the portion of the buffer layer 20 close to the N-type semiconductor layer 30 .

In the embodiment of the present invention, oxygen is doped into aluminum nitride, the material of the buffer layer, and the doping concentration of oxygen in the part of the buffer layer close to the substrate is greater than the doping concentration of oxygen in the part of the buffer layer close to the N-type semiconductor layer; The doping concentration of oxygen in the part of the layer close to the substrate is relatively high, which is relatively matched with the lattice of sapphire whose main component is Al ₂ O ₃ ; meanwhile, the doping concentration of oxygen in the part of the buffer layer close to the N-type semiconductor layer is relatively high. It is small, and the lattice is relatively matched with GaN-based materials. The buffer layer is arranged between the substrate using sapphire and the N-type semiconductor layer using GaN-based materials, which can realize the gradual transition from sapphire to GaN-based materials with two different lattices, and effectively alleviate sapphire and GaN-based materials. The lattice mismatch between the base materials can fully release the stress caused by the lattice mismatch between the sapphire and the GaN-based material, improve the defects caused by the lattice mismatch between the sapphire and the GaN-based material, and gradually reduce the position Dislocation density and crystallinity become better, greatly improve the crystal quality of epitaxial wafers, reduce the polarization of the active layer, improve the internal quantum efficiency, brightness and luminous efficiency of LEDs, at the same time reduce the reverse leakage of LEDs, and enhance the antistatic ability of LEDs .

In specific implementation, the oxygen doping concentration in the portion of the buffer layer 20 close to the substrate 10 is greater than 0, and the oxygen doping concentration in the portion of the buffer layer 20 close to the N-type semiconductor layer 30 may be greater than or equal to 0.

Optionally, the thickness of the buffer layer 20 may be 5 nm˜100 nm, preferably 50 nm.

If the thickness of the buffer layer is less than 5nm, the lattice mismatch between the sapphire and GaN-based materials may not be effectively alleviated because the thickness of the buffer layer is too small; if the thickness of the buffer layer is greater than 100nm, the The thickness is too large to cause waste and increase the production cost.

Optionally, the molar concentration of oxygen in each part of the buffer layer 20 may be 0%˜25%.

If the molar concentration of oxygen in each part of the buffer layer is greater than 25%, the lattice matching between the buffer layer and the GaN-based material may be poor due to the excessively high molar concentration of oxygen in the buffer layer, which affects the performance of the epitaxial wafer. The quality of the crystal makes it impossible to effectively improve the internal quantum efficiency, brightness and light efficiency of LEDs.

FIG. 2 is a schematic structural diagram of a buffer layer provided by an embodiment of the present invention. In FIG. 2, circles are used to schematically represent oxygen doped in the buffer layer. The more circles in a certain area, the higher the oxygen doping concentration in this area. high. Referring to FIG. 2 , in an implementation manner of this embodiment, the buffer layer 20 may be a single-layer structure, and the oxygen doping concentration in the single-layer structure gradually decreases along the stacking direction of the GaN-based light-emitting diode epitaxial wafer.

In the above implementation manner, there is no sub-layer boundary in the buffer layer 20, and the sub-layers cannot be divided; the oxygen doping concentration in the entire structure is constantly changing, and gradually decreases along the stacking direction of the GaN-based LED epitaxial wafer.

With the above implementation, the doping concentration of oxygen changes gradually, and the lattice constant of the buffer layer changes accordingly, and the transition is smooth, which can improve the crystal quality of the epitaxial wafer to the greatest extent, and improve the internal quantum efficiency, brightness and light efficiency of the LED.

Preferably, the doping concentration of oxygen in the single-layer structure can be linearly decreased along the stacking direction of the gallium nitride-based light-emitting diode epitaxial wafer. In practical applications, the doping concentration of oxygen in the single-layer structure can also be nonlinearly decreased along the stacking direction of the gallium nitride-based light-emitting diode epitaxial wafer.

Optionally, the maximum molar concentration of oxygen in the buffer layer 20 may be 3%˜20%, preferably 12%.

If the maximum value of the molar concentration of oxygen in the buffer layer is less than 3%, the molar concentration of oxygen in the buffer layer may be too low due to the fact that the maximum value of the molar concentration of oxygen in the buffer layer is too small to effectively relieve sapphire and gallium nitride. Lattice mismatch between base materials; if the maximum value of the molar concentration of oxygen in the buffer layer is greater than 20%, the molar concentration of oxygen in the buffer layer may be too high due to the fact that the maximum value of the molar concentration of oxygen in the buffer layer is too large High, the lattice matching between the buffer layer and the GaN-based material is poor, which affects the crystal quality of the epitaxial wafer, resulting in the inability to effectively improve the internal quantum efficiency, brightness and light efficiency of the LED.

Optionally, the minimum value of the molar concentration of oxygen in the buffer layer 20 may be 0%˜8%, preferably 4%.

If the minimum value of the molar concentration of oxygen in the buffer layer is greater than 8%, the molar concentration of oxygen in the buffer layer may be too high due to the fact that the minimum value of the molar concentration of oxygen in the buffer layer is too high, and the buffer layer and the gallium nitride-based material The lattice matching between them is poor, which affects the crystal quality of the epitaxial wafer, resulting in the inability to effectively improve the internal quantum efficiency, brightness and light efficiency of the LED.

For example, the molar concentration of oxygen in the buffer layer 20 is gradually decreased from 20% to 0%.

FIG. 3 is a schematic structural diagram of another buffer layer provided by an embodiment of the present invention. In FIG. 3 , circles are also used to schematically represent oxygen doped in the buffer layer. The larger the number of circles in a certain area, the more oxygen doped in this area the higher the concentration. Referring to FIG. 3 , in another implementation manner of this embodiment, the buffer layer 20 may be a stacked structure, and the doping concentration of oxygen in the stacked structure decreases layer by layer along the stacking direction of the GaN-based light-emitting diode epitaxial wafer Small.

In the above-mentioned implementation manner, the buffer layer 20 includes a plurality of sub-layers that can be divided into successive layers; the doping concentration of oxygen in a single sub-layer remains unchanged, and the doping concentration of oxygen in all sub-layers is along the lines of the GaN-based light emitting diode. The stacking direction of the epitaxial wafer decreases layer by layer.

By adopting the above-mentioned implementation manner, the implementation process is relatively simple, and the stability of the product is good.

Optionally, the doping concentration of oxygen in each sublayer in the stacked structure may be in an arithmetic progression. In practical applications, the doping concentration of oxygen in each sublayer in the stacked structure can also be non-uniformly reduced.

Specifically, the tolerance of the arithmetic sequence may be 1% to 5%, such as 3%.

Optionally, the maximum value of the molar concentration of oxygen in the buffer layer 20 may be 3%˜20%.

If the maximum value of the molar concentration of oxygen in the buffer layer is less than 3%, the molar concentration of oxygen in the buffer layer may be too low due to the fact that the maximum value of the molar concentration of oxygen in the buffer layer is too small to effectively relieve sapphire and gallium nitride. Lattice mismatch between base materials; if the maximum value of the molar concentration of oxygen in the buffer layer is greater than 20%, the molar concentration of oxygen in the buffer layer may be too high due to the fact that the maximum value of the molar concentration of oxygen in the buffer layer is too large High, the lattice matching between the buffer layer and the GaN-based material is poor, which affects the crystal quality of the epitaxial wafer, resulting in the inability to effectively improve the internal quantum efficiency, brightness and light efficiency of the LED.

Optionally, the minimum value of the molar concentration of oxygen in the buffer layer 20 may be 0%˜8%.

If the minimum value of the molar concentration of oxygen in the buffer layer is greater than 8%, the molar concentration of oxygen in the buffer layer may be too high due to the fact that the minimum value of the molar concentration of oxygen in the buffer layer is too high, and the buffer layer and the gallium nitride-based material The lattice matching between them is poor, which affects the crystal quality of the epitaxial wafer, resulting in the inability to effectively improve the internal quantum efficiency, brightness and light efficiency of the LED.

Optionally, the number of sublayers in the stacked structure may be 2 to 10, such as 6.

If the number of sublayers in the stacked structure is greater than 10, it may be difficult to precisely control the growth effect of each sublayer and its interface due to the large number of sublayers in the stacked structure, and the production cost will also increase.

Optionally, the thickness of each sub-layer in the stacked structure may be 3 nm˜10 nm, such as 6 nm.

If the thickness of each sublayer in the stacked structure is less than 3 nm, the lattice mismatch between the sapphire and GaN-based materials may not be effectively alleviated due to the too small thickness of each sublayer in the stacked structure; if the stacked structure If the thickness of each sub-layer is greater than 10 nm, it may cause material waste and increase production cost because the thickness of each sub-layer in the stacked structure is too large.

For example, the buffer layer 20 includes a sub-layer 21, a sub-layer 22 and a sub-layer 23 that are stacked in sequence, the molar concentration of oxygen in the sub-layer 21 is 20%, the molar concentration of oxygen in the sub-layer 22 is 10%, and the molar concentration of oxygen in the sub-layer 23 is 20%. The molarity is 0%.

Specifically, the material of the substrate 10 can be sapphire. In practical applications, the material of the substrate 10 can also be any one of silicon carbide, silicon, gallium nitride, zinc oxide, gallium arsenide, gallium phosphide, magnesium oxide and copper. The surface of the substrate 10 may be a flat surface, or may be a curved surface having a certain pattern formed by a process, such as a patterned sapphire substrate (English: Patterned Sapphire Substrate, PSS for short). For example, the substrate 10 adopts PSS, the pattern on the PSS is a number of cones arranged in an array, the diameter of the cones is 2.8 μm, the height of the cones is 1.8 μm, and the spacing between the cones is 3 μm.

The material of the N-type semiconductor layer 30 can be N-type doped gallium nitride. The active layer 40 may include multiple quantum wells and multiple quantum barriers, and multiple quantum wells and multiple quantum barriers are alternately stacked; the material of the quantum wells may be indium gallium nitride (InGaN), and the material of the quantum barriers may be nitrogen gallium. The material of the P-type semiconductor layer 50 may be P-type doped gallium nitride.

Further, the thickness of the N-type semiconductor layer 30 may be 1 μm˜3 μm, preferably 1.5 μm; the doping concentration of the N-type dopant in the N-type semiconductor layer 30 may be 10 ¹⁸ cm ^{−3 ˜3} *10 ¹⁹ cm ^{− 3} , preferably 6*10 ¹⁸ cm ^-3 . The thickness of the quantum wells can be 3nm to 4nm, preferably 3.5nm; the thickness of the quantum barriers can be 9nm to 15nm, preferably 12nm; the number of quantum wells is the same as the number of quantum barriers, and the number of quantum barriers can be 5 to 11 , preferably 8. The thickness of the P-type semiconductor layer 50 may be 100 nm˜300 nm, preferably 200 nm; the doping concentration of the P-type dopant in the P-type semiconductor layer 50 may be 10 ¹⁸ /cm ³ ˜10 ²⁰ /cm ³ , preferably 10 ¹⁹ /cm ³ .

Optionally, as shown in FIG. 1 , the GaN-based light-emitting diode epitaxial wafer may further include a high-temperature buffer layer 71, and the high-temperature buffer layer 71 is disposed between the buffer layer 20 and the N-type semiconductor layer 30, so as to relieve the substrate and the Lattice mismatch between N-type semiconductor layers.

In a specific implementation, the buffer layer is a thin layer of gallium nitride that is first grown on the substrate at a low temperature, so it is also called a low temperature buffer layer. Then, the longitudinal growth of gallium nitride in the low temperature buffer layer will form multiple independent three-dimensional island structures, which are called three-dimensional nucleation layers; then nitrogen is carried out on and between all three-dimensional island structures. The lateral growth of gallium nitride forms a two-dimensional planar structure, which is called a two-dimensional recovery layer; finally, a thicker layer of gallium nitride is grown on the two-dimensional growth layer at high temperature, which is called an intrinsic gallium nitride layer. In this embodiment, the three-dimensional nucleation layer, the two-dimensional recovery layer and the intrinsic gallium nitride layer are collectively referred to as a high temperature buffer layer.

Further, the thickness of the three-dimensional nucleation layer may be 400 nm to 600 nm, preferably 500 nm. The thickness of the two-dimensional recovery layer may be 500 nm to 800 nm, preferably 650 nm. The thickness of the intrinsic gallium nitride layer may be 1 μm˜2 μm, such as 1.5 μm.

Optionally, as shown in FIG. 1 , the gallium nitride-based light-emitting diode epitaxial wafer may further include a stress release layer 72, and the stress release layer 72 is disposed between the N-type semiconductor layer 30 and the active layer 40, so that the sapphire and The stress generated by the lattice mismatch between gallium nitrides is released to improve the crystal quality of the active layer, which is conducive to the radiative recombination of electrons and holes in the active layer, and improves the internal quantum efficiency of the LED, thereby improving the luminescence of the LED. efficiency.

Specifically, the stress release layer 72 may include a plurality of indium gallium nitride layers and a plurality of gallium nitride layers, and the plurality of indium gallium nitride layers and the plurality of gallium nitride layers are alternately stacked.

Further, the thickness of the indium gallium nitride layer in the stress release layer 72 may be 1 nm˜3 nm, preferably 2 nm; the thickness of the gallium nitride layer may be 20 nm˜40 nm, preferably 30 nm; the number of the indium gallium nitride layers is related to the nitrogen The number of gallium nitride layers is the same, and the number of gallium nitride layers may be 3 to 9, preferably 6.

Optionally, as shown in FIG. 1 , the GaN-based light-emitting diode epitaxial wafer may further include an electron blocking layer 73 , and the electron blocking layer 73 is disposed between the active layer 40 and the P-type semiconductor layer 50 to avoid electron transitions In the P-type semiconductor layer, non-radiative recombination with holes is carried out, which reduces the luminous efficiency of the LED.

Specifically, the material of the electron blocking layer 73 can be P-type doped aluminum gallium nitride (AlGaN), such as _{AlyGa1 -yN} , 0.1<y<0.5.

Further, the thickness of the electron blocking layer 73 may be 50 nm to 100 nm, preferably 75 nm.

Preferably, as shown in FIG. 1 , the GaN-based light-emitting diode epitaxial wafer may further include a low-temperature P-type layer 74, and the low-temperature P-type layer 74 is disposed between the active layer 40 and the electron blocking layer 73 to avoid electron blocking The higher growth temperature of the layer causes the precipitation of indium atoms in the active layer, which affects the luminous efficiency of the light-emitting diode.

In one implementation of this embodiment, the low-temperature P-type layer 74 may be substantially the same as the P-type semiconductor layer 50 , the only difference being that the growth temperature of the low-temperature P-type layer 74 is lower than the growth temperature of the P-type semiconductor layer 50 .

In another implementation manner of this embodiment, the material of the low temperature P-type layer 74 may be P-type doped gallium nitride.

Further, the thickness of the low-temperature P-type layer 74 may be 30 nm˜50 nm, preferably 40 nm; the doping concentration of the P-type dopant in the low-temperature P-type layer 74 may be 10 ²⁰ /cm ³ ˜10 ²¹ /cm ³ , preferably is 5*10 ²⁰ /cm ³ .

Optionally, as shown in FIG. 1 , the light-emitting diode epitaxial wafer may further include a P-type contact layer 75 , and the P-type contact layer 75 is laid on the P-type semiconductor layer 50 to connect with electrodes or transparent conductive electrodes formed in the chip fabrication process. Ohmic contacts are formed between the films.

Specifically, the material of the P-type contact layer 75 may be P-type doped indium gallium nitride.

Further, the thickness of the P-type contact layer 75 may be 5 nm˜100 nm, preferably 50 nm; the doping concentration of the P-type dopant in the P-type contact layer 75 may be 10 ²¹ /cm ³ ˜10 ²² /cm ³ , preferably is 6*10 ²¹ /cm ³ .

The embodiment of the present invention provides a method for growing a gallium nitride-based light-emitting diode epitaxial wafer, which is suitable for growing the gallium-nitride-based light-emitting diode epitaxial wafer shown in FIG. 1 . FIG. 4 is a flowchart of a method for growing a gallium nitride-based light-emitting diode epitaxial wafer provided by the implementation of the present invention. Referring to FIG. 4 , the growth method includes:

Step 201: Provide a substrate.

Optionally, the growth method can also include:

The substrate is pretreated.

Specifically, the pretreatment method may include chemical cleaning, high temperature baking, etc., so as to remove impurities on the surface of the substrate and improve the state of the surface of the substrate. For example, the substrates are pretreated with nitrogen purge and high temperature bake. Wherein, the temperature of the high temperature baking may be 550°C.

Preferably, the substrate is pretreated, which may include

Step 202: Grow a buffer layer on the substrate.

In this embodiment, the material of the buffer layer is aluminum nitride doped with oxygen, and the oxygen doping concentration in the portion of the buffer layer close to the substrate is greater than the oxygen doping concentration in the portion of the buffer layer close to the N-type semiconductor layer.

In an implementation manner of this embodiment, the step 202 may include:

placing the substrate into the reaction chamber of the growth apparatus;

Nitrogen and oxygen are introduced into the reaction chamber, and a buffer layer is grown on the substrate. The buffer layer is a single-layer structure. The volume of the nitrogen introduced during the growth of the single-layer structure is constant, and the volume of the oxygen introduced gradually decreases.

FIG. 5 is a schematic diagram of a variation of the volume of oxygen gas introduced during the growth of the buffer layer according to the embodiment of the present invention. Referring to FIG. 5 , in the above implementation mode, during the growth process of the buffer layer, the amount of nitrogen gas introduced is maintained. The volume of oxygen remains unchanged, and the volume of oxygen introduced is gradually reduced, and the doping concentration of oxygen in the grown buffer layer is correspondingly reduced, that is, the doping concentration of oxygen in the single-layer structure is along the stacking of the GaN-based light-emitting diode epitaxial wafer. direction gradually decreases.

Optionally, the maximum value of the flow rate of oxygen during the growth of the buffer layer may be 2.5%˜10% of the flow rate of nitrogen during the growth of the buffer layer, so as to match the maximum value of the molar concentration of oxygen in the buffer layer.

Optionally, the minimum value of the flow rate of oxygen during the growth of the buffer layer may be 0%˜5% of the flow rate of nitrogen during the growth of the buffer layer to match the minimum value of the molar concentration of oxygen in the buffer layer.

Alternatively, the power of the growth apparatus when the portion of the growth buffer layer is close to the substrate may be less than the power of the growth apparatus when the portion of the buffer layer is grown close to the N-type semiconductor layer. When the buffer layer is grown in the region close to the substrate, the power of the growth equipment is low, which can reduce arc discharge, reduce the generation of particles, and avoid contamination of the substrate; at the same time, when the buffer layer is grown in the region far from the substrate, the power of the growth equipment is low. The higher power can improve the crystal quality, provide a good starting point for the growth of gallium nitride, and at the same time increase the growth rate of the buffer layer and increase the productivity.

In another implementation manner of this embodiment, the step 202 may include:

placing the substrate into the reaction chamber of the growth apparatus;

Nitrogen and oxygen are fed into the reaction chamber, and a buffer layer is grown on the substrate. The buffer layer is of a stacked structure. The volume of nitrogen fed into the growth stack is unchanged, and the volume of oxygen fed into it decreases layer by layer. .

FIG. 6 is a schematic diagram of another variation of the volume of oxygen gas introduced during the growth of the buffer layer according to the embodiment of the present invention. Referring to FIG. 6 , in the above implementation manner, during the growth process of the buffer layer, the introduced nitrogen gas is kept At the same time, after the growth of each sublayer, the volume of oxygen introduced is reduced, and the doping concentration of oxygen in each sublayer is correspondingly reduced, that is, the doping concentration of oxygen in the stacked structure is along the gallium nitride base. The stacking direction of the light-emitting diode epitaxial wafers decreases layer by layer.

In the specific implementation, the volume of nitrogen gas introduced during the growth of the stacked structure remains unchanged, and the volume of oxygen gas introduced decreases layer by layer, so that a buffer layer can be grown in one reaction chamber, and the volume of oxygen gas introduced can be adjusted at the same time. , the buffer layer can also be grown in multiple reaction chambers in sequence, and the volume of oxygen introduced into each reaction chamber is different. When the buffer layers are sequentially grown in multiple reaction chambers with different volumes of oxygen introduced, the volume of oxygen introduced into each reaction chamber can remain unchanged, the state of the obtained sublayers is relatively stable, and the buffer layers of different furnaces The resulting epitaxial wafer grown on the layer has less fluctuation in the performance of the LED.

Optionally, the maximum value of the flow rate of oxygen during the growth of the buffer layer may be 2.5%˜10% of the flow rate of nitrogen during the growth of the buffer layer, so as to match the maximum value of the molar concentration of oxygen in the buffer layer.

Optionally, the minimum value of the flow rate of oxygen during the growth of the buffer layer may be 0%˜5% of the flow rate of nitrogen during the growth of the buffer layer to match the minimum value of the molar concentration of oxygen in the buffer layer.

Alternatively, the power of the growth apparatus when the portion of the growth buffer layer is close to the substrate may be less than the power of the growth apparatus when the portion of the buffer layer is grown close to the N-type semiconductor layer.

In practical applications, physical vapor deposition (English: Physical Vapor Deposition, PVD for short) technology (such as magnetron sputtering) can be used to grow the buffer layer, or metal-organic chemical vapor deposition (English: Metal-organic compound) can be used to grow the buffer layer. Chemical Vapor Deposition, referred to as: MOCVD) technology to grow the buffer layer.

Specifically, when using PVD technology to grow the buffer layer, the diameter of the reaction chamber can be 50cm-60cm, the height of the reaction chamber can be 70cm-80cm, the sputtering voltage can be 10V-10kV, and the pressure in the reaction chamber can be 3× 10 ^-5 Torr to 1 Torr; the reaction gases are argon and nitrogen, and the flow rate of argon introduced into the reaction chamber per unit volume is 1×10 ⁰ sccm/m ³ to 5×10 ³ sccm/m ³ . The flow rate of the nitrogen gas is 5×100 sccm/m ³ to 2×10 ⁴ sccm/m ³ , and the flow rate of the introduced oxygen is 0 sccm/m ³ to 2×10 ³ sccm/m ³ .

For example, when the buffer layer is a single-layer structure, the substrate is first put into the reaction chamber; then argon gas is passed into the reaction chamber, and a DC power P1 is applied. Then control the temperature in the reaction chamber to be T (eg 500°C), and the pressure in the reaction chamber to be Q (eg 3mTorr～7mTorr); pass argon gas with a flow rate a (eg 30sccm～60sccm) into the reaction chamber, and the flow rate is b (eg 100sccm～200sccm) nitrogen gas. Then, oxygen with a flow rate of c1 (such as 2sccm to 6sccm) is introduced into the reaction chamber, and a DC power P2 (such as 3000W to 5000W) is applied to grow nitridation with a higher oxygen doping concentration in the region of the buffer layer close to the substrate. aluminum. After a certain time (eg, 5s to 8s), the oxygen flow rate and the applied DC power in the reaction chamber are gradually changed. Finally, oxygen with a flow rate of c2 (such as 0 sccm) is introduced into the reaction chamber, and a DC power P3 (such as 4500W ~ 6500W) is applied to grow nitridation with a lower doping concentration of oxygen in the region of the buffer layer close to the N-type semiconductor layer. aluminum. Among them, P3>P2≥(5×P1), (c2/b)<(c1/b). The duration of the whole process may be 20s˜30s, and the thickness of the formed gallium nitride layer may be 10nm˜30nm.

For another example, when the buffer layer is a stacked structure, the substrate is firstly placed in the reaction chamber; then, argon gas is passed into the reaction chamber, and a DC power P1 is applied. Then control the temperature in the reaction chamber to be T1 (such as 450°C), and the pressure in the reaction chamber to be Q1 (such as 3mTorr ~ 7mTorr); pass argon gas with a flow rate of a1 (such as 30sccm ~ 60sccm) into the reaction chamber, and the flow rate is Nitrogen gas with b1 (eg 100sccm～200sccm) and oxygen with flow rate c1 (eg 2sccm～6sccm), and DC power P2 (eg 3000W～5000W) are applied, the doping concentration of oxygen is higher in the region of the buffer layer close to the substrate of aluminum nitride (for example, the thickness is 5nm ~ 15nm). Then, the gas flow rate and the applied DC power in the reaction chamber are gradually changed. Finally, the temperature in the reaction chamber is controlled to be T2 (such as 500°C), and the pressure in the reaction chamber is Q2 (such as 3mTorr ~ 7mTorr); argon gas with a flow rate of a2 (such as a2=a1) is introduced into the reaction chamber, and the flow rate is Nitrogen with b2 (eg b2=b1) and oxygen with flow rate c2 (eg c2=c1/2), and DC power P3 (eg 4500W～6500W) is applied to grow oxygen doping in the region of the buffer layer close to the N-type semiconductor layer Aluminum nitride with lower impurity concentration (for example, the thickness is 5nm to 10nm). Among them, P3>P2≥(5×P1), (c2/b2)<(c1/b1).

Step 203 : sequentially growing an N-type semiconductor layer, an active layer and a P-type semiconductor layer on the buffer layer.

In practical applications, the MOCVD technique can be used to grow the N-type semiconductor layer, the active layer and the P-type semiconductor layer.

Specifically, this step 203 may include:

The first step is to control the temperature to be 1000°C to 1100°C (preferably 1050°C), and the pressure to be 100torr to 500torr (preferably 300torr), and grow an N-type semiconductor layer on the buffer layer;

The second step is to grow the active layer on the N-type semiconductor layer; wherein, the growth temperature of the quantum well is 720°C to 800°C (preferably 760°C), and the pressure is 100torr to 500torr (preferably 300torr); the growth of the quantum barrier The temperature is 900°C～950°C (preferably 925°C), and the pressure is 100torr～500torr (preferably 300torr);

The third step is to control the temperature to be 850°C to 950°C (preferably 900°C) and the pressure to be 100torr to 300torr (preferably 200torr) to grow a P-type semiconductor layer on the active layer.

Optionally, before the first step, the manufacturing method may further include:

A high temperature buffer layer is grown on the buffer layer.

Accordingly, the N-type semiconductor layer is grown on the high temperature buffer layer.

Specifically, growing a high temperature buffer layer on the buffer layer may include:

Controlling the temperature to be 1000°C to 1040°C (preferably 1020°C), and the pressure to be 400torr to 600torr (preferably 500torr), grow a three-dimensional nucleation layer on the buffer layer;

Controlling the temperature to be 1040°C to 1080°C (preferably 1060°C), and the pressure to be 400torr to 600torr (preferably 500torr), grow a two-dimensional recovery layer on the three-dimensional nucleation;

The temperature is controlled to be 1050°C to 1100°C (preferably 1050°C), and the pressure is controlled to be 100torr to 500torr (preferably 300torr), and an intrinsic gallium nitride layer is grown on the two-dimensional recovery layer.

Optionally, before the second step, the manufacturing method may further include:

A stress relief layer is grown on the N-type semiconductor layer.

Accordingly, the active layer is grown on the stress release layer.

Specifically, growing the stress release layer on the N-type semiconductor layer may include:

The temperature is controlled to be 800°C to 1100°C (preferably 950°C), and the pressure is controlled to be 100torr to 500torr (preferably 300torr), and a stress release layer is grown on the N-type semiconductor layer.

Optionally, before the third step, the manufacturing method may further include:

An electron blocking layer is grown on the active layer.

Accordingly, the P-type semiconductor layer is grown on the electron blocking layer.

Specifically, growing an electron blocking layer on the active layer may include:

The electron blocking layer is grown on the active layer by controlling the temperature to be 900°C to 1000°C (preferably 950°C) and the pressure to be 200torr to 500torr (preferably 350torr).

Preferably, before growing the electron blocking layer on the active layer, the fabrication method may further include:

A low temperature P-type layer is grown on the active layer.

Accordingly, the electron blocking layer is grown on the low temperature P-type layer.

Specifically, growing a low-temperature P-type layer on the active layer may include:

The temperature is controlled to be 750°C to 850°C (preferably 800°C), and the pressure is controlled to be 100torr to 500torr (preferably 300torr), and a low temperature P-type layer is grown on the active layer.

Optionally, after the third step, the manufacturing method may further include:

A P-type contact layer is grown on the P-type semiconductor layer.

Specifically, growing a P-type contact layer on the P-type semiconductor layer may include:

The temperature is controlled to be 850°C to 1000°C (preferably 925°C), and the pressure is controlled to be 100torr to 300torr (preferably 200torr), and a P-type contact layer is grown on the P-type semiconductor layer.

It should be noted that, after the above epitaxial growth is completed, the temperature is first lowered to 650°C to 850°C (preferably 750°C), and the epitaxial wafer is subjected to 5 minutes to 15 minutes (preferably 10 minutes) in a nitrogen atmosphere. Annealing treatment, and then the temperature of the epitaxial wafer is reduced to room temperature.

Controlling the temperature and pressure both refers to controlling the temperature and pressure in the reaction chamber for growing the epitaxial wafer, specifically the reaction chamber of the metal-organic chemical vapor deposition (English: Metal-organic Chemical Vapor Deposition, MOCVD for short) equipment. Trimethylgallium or triethylgallium is used as the gallium source, high-purity ammonia is used as the nitrogen source, trimethylindium is used as the indium source, trimethylaluminum is used as the aluminum source, the N-type dopant is silane, and the P-type dopant is used. The dopant is magnesium dimethylocene.

The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection of the present invention. within the range.

Claims (5)

1. A gallium nitride-based light-emitting diode epitaxial wafer, the gallium nitride-based light-emitting diode epitaxial wafer comprising a substrate, a buffer layer, an N-type semiconductor layer, an active layer and a P-type semiconductor layer, the buffer layer, all the The N-type semiconductor layer, the active layer and the P-type semiconductor layer are sequentially stacked on the substrate, wherein the buffer layer is made of aluminum nitride doped with oxygen, and the buffer layer is made of aluminum nitride. It is a stacked structure, and the doping concentration of oxygen in the stacked structure decreases layer by layer along the stacking direction of the gallium nitride-based light-emitting diode epitaxial wafer; when growing the part of the buffer layer close to the substrate, the device is grown The power of growing the buffer layer is less than the power of the growth equipment when the part of the buffer layer close to the N-type semiconductor layer is grown; the buffer layer is grown in a plurality of reaction cavities in turn, and the volume of oxygen introduced into the plurality of reaction cavities is different. When the buffer layer grows, argon gas is first introduced into the reaction chamber and DC power is applied, and then the temperature and pressure in the reaction chamber are controlled, and argon and nitrogen gas are introduced into the reaction chamber. and oxygen and apply direct current power, wherein, the direct current power applied when feeding argon, nitrogen and oxygen into the reaction chamber is greater than or equal to 5 times the direct current power applied when feeding argon into the reaction chamber . 2 . The gallium nitride-based light-emitting diode epitaxial wafer according to claim 1 , wherein the maximum molar concentration of oxygen in the buffer layer is 3% to 20%, and the molar concentration of oxygen in the buffer layer is 3% to 20%. 3 . The minimum value is 0% to 8%. 3 . The gallium nitride based light emitting diode epitaxial wafer according to claim 1 or 2 , wherein the buffer layer has a thickness of 5 nm˜100 nm. 4 . 4. A method for growing a gallium nitride-based light-emitting diode epitaxial wafer, wherein the growing method comprises: providing a substrate; growing a buffer layer on the substrate; growing an N-type semiconductor layer, an active layer and a P-type semiconductor layer in sequence on the buffer layer; Wherein, the material of the buffer layer is aluminum nitride doped with oxygen, the buffer layer has a stacked structure, and the doping concentration of oxygen in the stacked structure is along the stacking of the GaN-based light-emitting diode epitaxial wafers. The direction decreases layer by layer; when the part of the buffer layer close to the substrate is grown, the power of the growth device is less than that of the growth device when the part of the buffer layer close to the N-type semiconductor layer is grown; Growth in a plurality of reaction chambers, the volume of oxygen introduced into the plurality of reaction chambers is different; when the buffer layer grows, argon gas is first introduced into the reaction chambers and DC power is applied, and then controlled The temperature and pressure in the reaction chamber, argon, nitrogen and oxygen are introduced into the reaction chamber and DC power is applied, wherein, the DC power applied when argon, nitrogen and oxygen are introduced into the reaction chamber, It is greater than or equal to 5 times of the DC power applied when argon gas is passed into the reaction chamber. 5 . The growth method according to claim 4 , wherein the maximum value of the flow rate of oxygen gas during the growth of the buffer layer is 2.5% to 10% of the flow rate of nitrogen gas during the growth of the buffer layer, and the buffer layer is grown. 6 . The minimum value of the flow rate of oxygen is 0% to 5% of the flow rate of nitrogen when the buffer layer is grown.

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