CN114122212B - LED epitaxial structure and preparation method thereof - Google Patents

Abstract

The invention provides an LED epitaxial structure and a preparation method thereof. The LED epitaxial structure includes from bottom to top: a bottom buffer layer located on a substrate, a corrosion cutoff layer, a first type semiconductor layer, an active layer and a second type semiconductor layer, wherein the first type semiconductor layer includes a first type window layer, a first type roughened confinement layer, a first type confinement layer and a first type waveguide layer from bottom to top, and the first type The roughened confinement layer is a structural layer with a gradual change in Al composition. The present invention can improve the light extraction efficiency of the LED chip, reduce the operating voltage of the LED chip, and improve process stability by forming a first-type roughened confinement layer with a gradient Al composition.

Description

LED epitaxial structure and preparation method thereof

Technical field

The present invention relates to the field of semiconductor technology, and in particular to an LED epitaxial structure and a preparation method thereof.

Background technique

Light Emitting Diode (LED, Light Emitting Diode) is a semiconductor solid light-emitting device with the advantages of simple structure, light weight, and no pollution. It has been widely used in many fields such as digital, display, lighting, and plant engineering. It is known as environmentally friendly , energy-saving green lighting sources contain huge business opportunities. Among them, III-V compound semiconductors represented by gallium arsenide (GaAs) have huge applications in optoelectronic fields such as high-brightness light-emitting diodes and lasers due to their high luminous efficiency, high electron saturation drift speed, and stable chemical properties. potential has attracted widespread attention.

In order to obtain a light-emitting diode with high luminous efficiency, a reverse polarity structure is generally adopted, that is, a structure with the N electrode on top and the P electrode on the bottom. The front surface (N electrode surface) adopts a roughening process to improve the light extraction efficiency. At present, the commonly used surface roughening process in the industry is generally wet chemical etching, and how to control the roughening effect has become the focus of people in this field.

Contents of the invention

The object of the present invention is to provide an LED epitaxial structure and a preparation method thereof to control the roughening effect, improve the light extraction efficiency of the LED chip, reduce the operating voltage of the LED chip, and improve process stability.

In order to achieve the above objects and other related objects, the present invention provides an LED epitaxial structure, which includes from bottom to top: a bottom buffer layer located on the substrate, a corrosion cutoff layer, a first-type semiconductor layer, and a a source layer and a second-type semiconductor layer, wherein the first-type semiconductor layer includes, from bottom to top, a first-type window layer, a first-type roughened confinement layer, a first-type confinement layer, and a first-type waveguide layer, and The first type roughening restriction layer is a structural layer with a gradient Al composition.

Optionally, the first type roughening restriction layer includes a single-layer structure or a multi-periodic structure composed of the first structural layer, and the period number k ranges from 2 to 30.

Optionally, the first structural layer is (Al _x Ga _1-x ) _y In _1-y P, and x ranges from 0.05 to 0.65, and y ranges from 0.45 to 0.55.

Optionally, the thickness of the first type roughening limiting layer is 100 nm to 1500 nm.

Optionally, the first type roughening restriction layer includes a two-layer structure composed of a first structural layer and a second structural layer or a multi-period structure composed of an alternate stack of first structural layers and second structural layers, with a period number k. Range is 2 to 30.

Optionally, the first structural layer is (Al _m Ga _1-m ) _n In _1-n P, the second structural layer is (A _a Ga _1-a ) _b In _{1- b} P, and 0.05 ≤m≤0.65, 0.05≤a≤0.65, 0.45≤n≤0.55, 0.45≤b≤0.55.

Optionally, the gradient mode of the Al component in the first type roughening restriction layer includes one or any combination of linear gradient, nonlinear gradient, stepwise change.

Optionally, the gradient mode of the Al component in the linear gradient is a linear gradient from large to small or from small to large in a direction from the first type window layer to the first type confinement layer.

Optionally, in the same period, the difference between the maximum value and the minimum value of the Al component a and the Al component m in the first structural layer and the second structural layer is greater than 0.25.

Optionally, in the same cycle, the difference between the In component n and the In component b in the first structural layer and the second structural layer is less than 5%.

Optionally, the thickness of the first structural layer is 10 nm ~ 750 nm, the thickness of the second structural layer is 10 nm ~ 750 nm, and the thickness of the first type roughening limiting layer is 100 nm ~ 1500 nm.

Optionally, the first type roughening confinement layer is doped with Si or Te.

Optionally, the first type semiconductor layer further includes a first type ohmic contact layer, and the first type ohmic contact layer is located between the corrosion stop layer and the first type window layer.

Optionally, the second type semiconductor layer includes, from bottom to top, a second type waveguide layer, a second type confinement layer, a transition layer, a second type window layer, and a second type ohmic contact layer.

Optionally, the first-type semiconductor layer is an N-type semiconductor layer, and the second-type semiconductor layer is a P-type semiconductor layer.

Optionally, the substrate includes a GaAs substrate or a Si substrate.

In order to achieve the above objects and other related objects, the present invention also provides a method for preparing an LED epitaxial structure, which includes the following steps:

provide a substrate;

A bottom buffer layer, a corrosion stop layer, and a first-type semiconductor layer are sequentially grown on the substrate, wherein the first-type semiconductor layer includes, from bottom to top, a first-type window layer, a first-type roughening restriction layer, A first-type confinement layer and a first-type waveguide layer, and the first-type roughened confinement layer is a structural layer with a gradient Al composition;

An active layer and a second type semiconductor layer are grown sequentially on the first type semiconductor layer.

Optionally, the first type roughening restriction layer includes a single-layer structure or a multi-periodic structure composed of the first structural layer, and the period number k ranges from 2 to 30.

Optionally, the first structural layer is (Al _x Ga _1-x ) _y In _1-y P, and x ranges from 0.05 to 0.65, and y ranges from 0.45 to 0.55.

Optionally, the thickness of the first type roughening limiting layer is 100 nm to 1500 nm.

Optionally, the first type roughening restriction layer includes a two-layer structure composed of a first structural layer and a second structural layer or a multi-period structure composed of an alternate stack of first structural layers and second structural layers, with a period number k. Range is 2 to 30.

Optionally, the first structural layer is (Al _m Ga _1-m ) _n In _1-n P, the second structural layer is (A _a Ga _1-a ) _b In _{1- b} P, and 0.05 ≤m≤0.65, 0.05≤a≤0.65, 0.45≤n≤0.55, 0.45≤b≤0.55.

Optionally, the gradient mode of the Al component in the first type roughening restriction layer is one of linear gradient, nonlinear gradient, stepwise change, or any combination.

Optionally, the gradient mode of the Al component in the linear gradient is a linear gradient from large to small or from small to large in a direction from the first type window layer to the first type confinement layer.

Optionally, in the same period, the difference between the maximum value and the minimum value of the Al component a and the Al component m in the first structural layer and the second structural layer is greater than 0.25.

Optionally, in the same cycle, the difference between the In component n and the In component b in the first structural layer and the second structural layer is less than 5%.

Optionally, the thickness of the first structural layer is 10 nm ~ 750 nm, the thickness of the second structural layer is 10 nm ~ 750 nm, and the thickness of the first type roughening limiting layer is 100 nm ~ 1500 nm.

Optionally, the first type roughening confinement layer is doped with Si or Te.

Optionally, the first type semiconductor layer further includes a first type ohmic contact layer, and the first type ohmic contact layer is located between the corrosion stop layer and the first type window layer.

Optionally, the second type semiconductor layer includes, from bottom to top, a second type waveguide layer, a second type confinement layer, a transition layer, a second type window layer, and a second type ohmic contact layer.

Optionally, the first-type semiconductor layer is an N-type semiconductor layer, and the second-type semiconductor layer is a P-type semiconductor layer.

Optionally, the substrate includes a GaAs substrate or a Si substrate.

Optionally, the preparation process of the epitaxial structure is any one of MOCVD process, molecular beam epitaxy process, HVPE process, plasma-assisted chemical vapor deposition and sputtering method.

Compared with the existing technology, the technical solution of the present invention has the following beneficial effects:

The present invention ensures that the first type roughening restriction layer has better corrosion restriction for the roughening solution by arranging a first type roughening restriction layer with a gradient Al composition between the first type window layer and the first type restriction layer. Effect, the overall depth of roughening can be effectively controlled to control the roughening effect, thereby improving the current expansion effect, reducing the operating voltage, and improving process stability; at the same time, due to the gradual change of the Al component to form a structure with a gradual refractive index, it can effectively reduce the LED The internal reflection loss of the epitaxial structure increases the exit angle of the light emitted from the LED epitaxial structure, allowing more light to be coupled out, improving the light extraction efficiency of the LED chip, and thereby improving the luminous efficiency of the LED chip.

Description of the drawings

Figure 1 is a schematic structural diagram of an LED epitaxial structure according to Embodiment 1 of the present invention;

Figure 2 is a schematic structural diagram of the first type of roughening restriction layer in Embodiment 2 of the present invention;

Figure 3 is a flow chart of a method for manufacturing an LED epitaxial structure according to an embodiment of the present invention;

In Figures 1 to 2,

101-Substrate, 102-Bottom buffer layer, 103-Corrosion stop layer, 201-First type ohmic contact layer, 202-First type window layer, 203-First type roughening restriction layer, 204-First type restriction Layer, 205-first type waveguide layer, 206-active layer, 207-second type waveguide layer, 208-second type confinement layer, 209-transition layer, 210-second type window layer, 211-second type Ohmic contact layer, 2031-first structural layer, 2032-second structural layer.

Detailed ways

The LED epitaxial structure and its preparation method proposed by the present invention will be further described in detail below with reference to the accompanying drawings and specific examples. The advantages and features of the present invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use imprecise proportions, and are only used to conveniently and clearly assist in explaining the embodiments of the present invention.

Before describing the embodiment according to the present invention, the following content will be described in advance. First, in this specification, when simply labeled "GaInP", it means that the chemical composition ratio of the sum of Ga and In to P is 1:1, and that the ratio of Ga and In is not fixed. When simply labeled "AlGaInP", it means that the chemical composition ratio of the sum of Al, Ga, and In to P is 1:1, and that the ratio of Al, Ga, and In is not fixed. In addition, when simply labeled as "AlInP", it means that the chemical composition ratio of the sum of Al and In to P is 1:1, and the ratio of Al to In is not fixed.

Embodiment 1

Figure 1 is a schematic structural diagram of the LED epitaxial structure of this embodiment. Referring to Figure 1, the LED epitaxial structure includes from bottom to top: a bottom buffer layer 102 located on the substrate 101, an etching stop layer 103, a first-type semiconductor layer, an active layer 206 and a second-type semiconductor layer, wherein, The first type semiconductor layer includes a first type window layer 202, a first type roughening confinement layer 203, a first type confinement layer 204 and a first type waveguide layer 205 from bottom to top, and the first type roughening The confinement layer 203 is a structural layer with a gradient Al composition.

The first type semiconductor layer further includes a first type ohmic contact layer 201 , and the first type ohmic contact layer 201 is located between the corrosion stop layer 103 and the first type window layer 202 .

The second type semiconductor layer includes, from bottom to top, a second type waveguide layer 207, a second type confinement layer 208, a transition layer 209, a second type window layer 210, and a second type ohmic contact layer 211.

The first-type semiconductor layer and the second-type semiconductor layer have opposite polarities. For example, if the first-type semiconductor layer is an N-type semiconductor layer, the corresponding second-type semiconductor layer is a P-type semiconductor layer. . Correspondingly, the N-type semiconductor layer includes an N-type ohmic contact layer, an N-type window layer, an N-type roughened confinement layer, an N-type confinement layer and an N-type waveguide layer stacked in sequence. The P-type semiconductor layer includes a P-type waveguide layer, a P-type confinement layer, a transition layer, a P-type window layer and a P-type ohmic contact layer stacked in sequence.

Referring to Figure 3, the preparation method of the LED epitaxial structure specifically includes the following steps:

Step S1: Provide a substrate 101;

Step S2: Sequentially grow the bottom buffer layer 102, the corrosion stop layer 103 and the first-type semiconductor layer on the substrate 101, where the first-type semiconductor layer includes the first-type window layer 202, the first-type window layer 202 and the first-type semiconductor layer 202 from bottom to top. A type of roughened confinement layer 203, a first type of confinement layer 204 and a first type of waveguide layer 205, and the first type of roughened confinement layer 203 is a structural layer with a gradient Al composition;

Step S3: sequentially grow the active layer 206 and the second-type semiconductor layer on the first-type semiconductor layer.

The preparation process of the LED epitaxial structure is any one of metal organic compound chemical vapor deposition (MOCVD) process, molecular beam epitaxy (MBE) process or ultra-high vacuum chemical vapor deposition (UHVCVD) process, preferably MOCVD process. In the following specific embodiments, the MOCVD process is taken as an example for description.

In step S1, the substrate 101 is preferably a GaAs (gallium arsenide) substrate, and may also be a Si (silicon) substrate, but is not limited thereto.

In step S2, a bottom buffer layer 102 is grown on the substrate 101. The bottom buffer layer 102 minimizes the impact of surface defects of the substrate 101 on the LED epitaxial structure, reduces defects and dislocations in the LED epitaxial structure, and provides a fresh interface for the next step of growth. The material of the bottom buffer layer 102 is preferably GaAs, but is not limited thereto. The bottom buffer layer 102 is doped with a first-type dopant, such as an N-type dopant, which may be at least one of silicon (Si) and tellurium (Te), but is not limited thereto. Further, the first type dopant is preferably Si.

The growth of the bottom buffer layer 102 preferably involves growing the bottom buffer layer 102 with a thickness of 100 nm to 300 nm in a reaction chamber of a MOCVD growth furnace. For example, the bottom buffer layer 102 is grown to a thickness of 200 nm.

After growing the bottom buffer layer 102 , an corrosion stop layer 103 is grown on the bottom buffer layer 102 . The material of the corrosion stop layer 103 is preferably GaInP, but is not limited thereto. The corrosion stop layer 103 is doped with a first-type dopant, such as an N-type dopant, which may be at least one of silicon (Si) and tellurium (Te), but is not limited thereto. Further, the first type dopant is preferably Si.

The corrosion stop layer 103 is preferably grown in a reaction chamber of a MOCVD growth furnace with a thickness of 100 nm to 200 nm. For example, the corrosion stop layer 103 is grown to a thickness of 150 nm.

After the corrosion stop layer 103 is grown, a first type semiconductor layer is grown on the corrosion stop layer 103 . The first type semiconductor layer includes a first type window layer 202, a first type roughening confinement layer 203, a first type confinement layer 204 and a first type waveguide layer 205 from bottom to top, and the first type roughening The confinement layer 203 is a structural layer with a gradient Al composition. The first type semiconductor layer may further include a first type ohmic contact layer 201 , and the first type ohmic contact layer 201 is located between the corrosion stop layer 103 and the first type window layer 202 .

Therefore, after growing the corrosion stop layer 103 , the first type ohmic contact layer 201 is grown on the corrosion stop layer 103 . The first type ohmic contact layer 201 may be made of InGaAs or GaAs, preferably GaAs, but is not limited thereto. The first type ohmic contact layer 201 is doped with a first type dopant, such as an N-type dopant, which can be one of silicon (Si) and tellurium (Te), but is not limited thereto. Further, the first type dopant is preferably Si.

The first type ohmic contact layer 201 is preferably grown in a reaction chamber of a MOCVD growth furnace with a thickness of 20 nm to 100 nm. For example, the first type ohmic contact layer 201 is grown to a thickness of 50 nm.

After growing the first type ohmic contact layer 201, the first type window layer 202 is grown on the first type ohmic contact layer 201. The main functions of the first type window layer 202 are first type current expansion and light extraction. The first type window layer 202 may be made of AlGaInP, but is not limited thereto. The first type window layer 202 is doped with a first type dopant, such as an N-type dopant, which may be at least one of silicon (Si) and tellurium (Te), but is not limited thereto. Further, the first type dopant is preferably Si.

The growth of the first type window layer 202 preferably involves growing the first type window layer 202 with a thickness of 500 nm to 2500 nm in a reaction chamber of a MOCVD growth furnace. For example, the first type window layer 202 is grown to a thickness of 1000 nm.

After growing the first type window layer 202, the first type roughening limiting layer 203 is grown on the first type window layer 202. For reverse polarity products, a wet roughening process is currently used to roughen the first type window layer 202. For the same material such as AlGaInP, the selection ratio of wet roughening has a greater correlation with the Al component. When When the Al composition difference is large, the wet roughening speed can be effectively limited. This application uses a structural layer with a gradient Al composition as the first type of roughening limiting layer 203, which can effectively limit the wet roughening speed in the longitudinal direction (along the thickness direction of the LED epitaxial structure). Controlling the roughening depth during wet roughening ensures the optimization of structural design and improves process stability; by controlling the remaining thickness of each core particle to be consistent, the brightness and voltage consistency of each core particle are good; and , controlling the roughening effect, the lateral direction can promote the current expansion, thereby reducing the operating voltage; in addition, the refractive index of the Al component gradient structure is also gradient, which can effectively reduce the internal reflection of the LED epitaxial structure and improve the light extraction efficiency.

The first type roughening restriction layer 203 includes a single-layer structure or a multi-period structure composed of a first structural layer 2031, and the period number k ranges from 2 to 30. Referring to FIG. 1 , the first type roughening restriction layer 203 includes a first structural layer 2031 with a single-layer structure. The material of the first structural layer 2031 is (Al _x Ga _1-x ) _y In _1-y P, And the range of x is 0.05-0.65, and the range of y is 0.45-0.55, and y is preferably 0.5. In other embodiments, the first type roughening restriction layer 203 may also include a multi-periodic structure composed of multiple first structural layers 2031. For example, when the period number k is equal to 5, it is a multi-periodic structure composed of five first structural layers 2031. periodic structure. The Al component gradient in the first type roughening restriction layer 203 includes one or any combination of linear gradient, nonlinear gradient, stepwise change. Specifically, the linear gradient includes a linear gradient from a low Al component to a high Al component or from a low Al component to a high Al component in the direction from the first type window layer 202 to the first type confinement layer 204; Nonlinear gradients, for example, first gradually change and then become stable, or first gradually change, then become stable and then gradually change again, or parabolic gradients, etc.; stepped changes are step-like sudden changes, such as jumping directly from 0.1 to 0.2, and then jumping to 0.4 etc. In a preferred embodiment, the Al component x decreases linearly from 0.45 to 0.15 from bottom to top (from the first type window layer 202 to the first type confinement layer 204), thereby playing a role in coarsening and restriction. .

The first type roughening restriction layer 203 is doped with a first type dopant, such as an N-type dopant, which may be at least one of silicon (Si) and tellurium (Te), but is not limited thereto. Further, the first type dopant is preferably Si. The growth of the first type roughening restriction layer 203 is preferably performed by growing the first type roughening restriction layer 203 with a thickness of 100 nm to 1500 nm in a reaction chamber of a MOCVD growth furnace. For example, the first type roughening restriction layer 203 is grown to a thickness of 1000 nm.

After growing the first type roughening restriction layer 203, the first type restriction layer 204 is grown on the first type roughening restriction layer 203. The material of the first type confinement layer 204 is preferably AlInP, but is not limited thereto. The first type confinement layer 204 is doped with a first type dopant, such as an N-type dopant, which may be at least one of silicon (Si) and tellurium (Te), but is not limited thereto. Further, the first type dopant is preferably Si.

The first type confinement layer 204 is preferably grown in a reaction chamber of a MOCVD growth furnace with a thickness of 200 nm to 1000 nm. For example, the first type confinement layer 204 is grown to a thickness of 500 nm.

After growing the first type confinement layer 204, the first type waveguide layer 205 is grown on the first type confinement layer 204. The material of the first type waveguide layer 205 is preferably ( _Aly Ga _1-y ) _0.5 In _0.5 P, and 0.45≤y≤0.85. The first type waveguide layer 205 is an undoped layer, that is, the first type waveguide layer 205 is not doped with any element.

The growth of the first type waveguide layer 205 preferably involves growing the first type waveguide layer 205 with a thickness of 40 nm to 200 nm in a reaction chamber of a MOCVD growth furnace. For example, the first type waveguide layer 205 is grown to a thickness of 100 nm.

In step S3, after growing the first type waveguide layer 205, the active layer 206 is grown on the first type waveguide layer 205. The active layer 206 is mainly used as a light-emitting layer. The active layer 206 is preferably a multi-quantum well structure, that is, the active layer 206 is preferably a periodic structure composed of quantum wells and quantum barriers, and the number of periods of the active layer 206 is preferably 6 to 60 pairs. The active layer 206 may be made of AlGaInP/AlGaInP, where the quantum barrier has a higher Al component and the quantum well has a lower Al component. The thickness of the active layer 206 is preferably 50 nm to 500 nm.

The growth of the active layer 206 is preferably performed in a reaction chamber of a MOCVD growth furnace for 6 to 60 cycles. For example, active layer 206 is grown for 12 cycles.

After growing the active layer 206, a second-type semiconductor layer is grown on the active layer 206. The second type semiconductor layer includes, from bottom to top, a second type waveguide layer 207, a second type confinement layer 208, a transition layer 209, a second type window layer 210, and a second type ohmic contact layer 211.

Therefore, after growing the active layer 206, the second type waveguide layer 207 is grown on the active layer 206. The first type waveguide layer 205 and the second type waveguide layer 207 are grown as waveguide layers between the active layer 206 and the confinement layer, mainly to block impurity diffusion from affecting the internal quantum efficiency of the active layer 206, and at the same time The recombination probability of electron holes is increased, the electron holes are effectively prevented from overflowing the active layer 206, and the luminous efficiency is improved.

The material of the second type waveguide layer 207 is preferably the same as the material of the first type waveguide layer 205, that is, the material of the second type waveguide layer 207 is also preferably ( _Aly Ga _1-y ) _0.5 In _0.5 P , and 0.45≤y≤0.85. For example, the material of the second type waveguide layer 207 is (Al _0.65 Ga _0.35 ) _0.5 In _0.5 P. The second type waveguide layer 207 is an undoped layer, that is, the second type waveguide layer 207 is not doped with any element.

The growth of the second-type waveguide layer 207 is preferably performed by growing the second-type waveguide layer 207 with a thickness of 40 nm to 300 nm in a reaction chamber of a MOCVD growth furnace. For example, the second type waveguide layer 207 is grown to a thickness of 80 nm.

After growing the second type waveguide layer 207, the second type confinement layer 208 is grown on the second type waveguide layer 207. The second type confinement layer 208 is used to provide holes. Moreover, the first type confinement layer 204 and the second type confinement layer 208 mainly serve two functions as confinement layers. On the one hand, they restrict minority carriers from overflowing the active layer 206 and improve the recombination luminous efficiency; on the other hand, As an important window, the photons emitted by the active layer 206 can easily pass through the confinement layer, thereby improving the luminous efficiency of the LED chip.

The material of the second type restriction layer 208 is preferably AlInP, but is not limited thereto. The second type confinement layer 208 is doped with a second type dopant, such as a p-type dopant, which may be at least one of magnesium (Mg) and zinc (Zn), but is not limited thereto. Further, the second type dopant is preferably Mg.

The growth of the second type confinement layer 208 preferably involves growing the second type confinement layer 208 with a thickness of 200 nm to 1500 nm in a reaction chamber of a MOCVD growth furnace. For example, the second type confinement layer 208 is grown to a thickness of 500 nm.

After growing the second type confinement layer 208, the transition layer 209 is grown on the second type confinement layer 208. The transition layer 209 is preferably made of AlGaInP, but is not limited thereto. The second type transition layer 209 is doped with a second type dopant, such as a p-type dopant, which may be at least one of magnesium (Mg) and zinc (Zn), but is not limited thereto. Further, the second type dopant is preferably Mg.

The transition layer 209 is preferably grown in a reaction chamber of a MOCVD growth furnace with a thickness of 10 nm to 80 nm. For example, a transition layer 209 is grown to a thickness of 50 nm.

After growing the transition layer 209, the second type window layer 210 is grown on the transition layer 209. The material of the second type window layer 210 is preferably GaP, but is not limited thereto. The second type window layer 210 is doped with a second type dopant, such as a p-type dopant, which can be at least one of magnesium (Mg), zinc (Zn), and carbon (C), but is not limited to this. Further, the second type dopant is preferably Mg.

The growth of the second type window layer 210 preferably involves growing the second type window layer 210 with a thickness of 200 nm to 3000 nm in a reaction chamber of a MOCVD growth furnace. For example, the second type window layer 210 is grown to a thickness of 2000 nm.

After the second type window layer 210 is grown, the second type ohmic contact layer 211 is grown on the second type window layer 210 . The second type ohmic contact layer 211 is used to form ohmic contact with the metal electrode. The material of the second type ohmic contact layer 211 is preferably GaP, but is not limited thereto. The second type ohmic contact layer 211 may be doped with carbon (C).

The growth of the second-type ohmic contact layer 211 preferably involves growing the second-type ohmic contact layer 211 with a thickness of 20 nm to 100 nm in a reaction chamber of a MOCVD growth furnace. For example, the second type ohmic contact layer 211 is grown to a thickness of 50 nm.

Embodiment 2

Figure 2 is a schematic structural diagram of the first type roughening restriction layer in this embodiment. The difference between this embodiment and Embodiment 1 is only that the structure of the first type roughening restriction layer 203 is different, and the parts with the same structure will not be described again here. Compared with Embodiment 1, Embodiment 2 has better coarsening limiting effect and promotion of lateral current expansion.

Specifically, the first type roughening restriction layer 203 in the LED epitaxial structure includes a two-layer structure composed of a first structural layer 2031 and a second structural layer 2032 or the first structural layer 2031 and the second structural layer 2032 are alternately stacked In the multi-periodic structure formed, the period number k ranges from 2 to 30, preferably from 20 to 30. Referring to FIG. 2 , the first type roughening restriction layer 203 includes a two-layer structure composed of a first structural layer 2031 and a second structural layer 2032 . The material of the first structural layer 2031 is (Al _m Ga _1-m ) _n In _1-n P, and the material of the second structural layer 2032 is (A _a Ga _1-a ) _b In _1-b P. That is, the material of the first type roughening restriction layer 203 is (Al _m Ga _1-m ) _n In _1-n P/(A _a Ga _1-a ) _b In _1-b P. Wherein, the ranges of n and b are both 0.45 to 0.55, preferably b=0.5, n=0.5; 0.05≤m≤0.65, 0.05≤a≤0.65. In other embodiments, the first type roughening restriction layer 203 may also include a multi-period structure composed of multiple first structural layers 2031 and second structural layers 2032. For example, when the period number k is equal to 10, there are 10 groups of first structures. The structural layer 2031 and the second structural layer 2032 are alternately stacked to form a multi-periodic structure, that is, the material of the first type roughening restriction layer 203 is ((Al _m Ga _1-m ) _n In _1-n P/(Al _a Ga _1-a ) _b In _1-b P) ₁₀ . Moreover, in the same cycle, the difference between the maximum value and the minimum value of Al component a and Al component m is greater than 0.25 to ensure that the first type roughening restriction layer 203 has better corrosion restriction for the roughening solution. Effect: In the same cycle, the difference between In component n and In component b is less than 5% to ensure that the lattice mismatch between the first type roughening restriction layer 203 and the substrate 101 is small.

After growing the first type window layer 202, first grow the first structural layer 2031 on the first type window layer 202, and then grow the second structural layer 2032, that is, completing the first step of a cycle. The growth of the first type roughening restriction layer 203; continuing to alternately grow the first structural layer 2031 and the second structural layer 2032 is to complete the growth of the first type roughening restriction layer 203 with a multi-periodic structure. The Al component gradient in the first type roughening restriction layer 203 includes one or any combination of linear gradient, nonlinear gradient, stepwise change. Specifically, the linear gradient includes a linear gradient from a low Al component to a high Al component or from a low Al component to a high Al component in the direction from the first type window layer 202 to the first type confinement layer 204; Nonlinear gradients, for example, first gradually change and then become stable, or first gradually change, then become stable and then gradually change again, or parabolic gradients, etc.; stepped changes are step-like sudden changes, such as jumping directly from 0.1 to 0.2, and then jumping to 0.4 etc. In a preferred embodiment, the Al component m in the first structural layer 2031 linearly gradients from 0.15 to 0.45 from bottom to top (from the first type window layer 202 to the first type confinement layer 204). Increasingly, the Al component a in the second structural layer 2032 decreases linearly from 0.45 to 0.15 from bottom to top (from the first type window layer 202 to the first type confinement layer 204).

The thickness of the first structural layer 2031 is 10 nm to 750 nm, the thickness of the second structural layer 2032 is 10 nm to 750 nm, and the total thickness of the first type roughening restriction layer 203 is 100 to 1500 nm.

The present invention ensures that the first type roughening restriction layer has better corrosion restriction for the roughening solution by arranging a first type roughening restriction layer with a gradient Al composition between the first type window layer and the first type restriction layer. Effect, the overall depth of roughening can be effectively controlled to control the roughening effect, thereby improving the current expansion effect, reducing the operating voltage, and improving process stability; at the same time, due to the gradual change of the Al component to form a structure with a gradual refractive index, it can effectively reduce the LED The internal reflection loss of the epitaxial structure increases the exit angle of the light emitted from the LED epitaxial structure, allowing more light to be coupled out, improving the light extraction efficiency of the LED chip, and thereby improving the luminous efficiency of the LED chip.

In addition, it can be understood that although the present invention has been disclosed above in preferred embodiments, the above embodiments are not intended to limit the present invention. For any person familiar with the art, without departing from the scope of the technical solution of the present invention, they can use the technical content disclosed above to make many possible changes and modifications to the technical solution of the present invention, or modify it into equivalent changes. Example. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the protection scope of the technical solution of the present invention.

Furthermore, it is to be understood that this invention is not limited to the particular methods, compounds, materials, manufacturing techniques, uses and applications described herein, as they may vary. It should also be understood that the terminology described herein is used only to describe particular embodiments and is not intended to limit the scope of the invention. It must be noted that, as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates a contrary meaning. Thus, for example, a reference to "a step" means a reference to one or more steps, and may include secondary steps. All conjunctions used should be understood in their broadest sense. Accordingly, the word "or" should be understood to have the definition of a logical "or" and not a logical "exclusive-or" unless the context clearly indicates the contrary. Structures described herein will be understood to also recite functional equivalents of that structure. Language that may be construed as approximate should be construed as such unless the context clearly indicates a contrary meaning.

Claims (25)

1. An LED epitaxial structure, characterized in that the LED epitaxial structure includes from bottom to top: a bottom buffer layer located on the substrate, a corrosion cutoff layer, a first type semiconductor layer, an active layer and a second type semiconductor layer, wherein the first-type semiconductor layer includes a first-type window layer, a first-type roughened confinement layer, a first-type confinement layer and a first-type waveguide layer from bottom to top, and the first-type roughened layer The confinement layer is a structural layer with a gradient Al component. The gradient mode of the Al component in the first type roughened confinement layer is a linear gradient or a nonlinear gradient. The first type roughened confinement layer includes four structures: Any one: a single-layer structure composed of the first structural layer, a multi-periodic structure composed of the first structural layer, a two-layer structure composed of the first structural layer and the second structural layer, and the first structural layer and the second structural layer alternately stacked A multi-periodic structure composed of, wherein the first type roughening confinement layer is a single-layer structure or a multi-periodic structure composed of a first structural layer, the first structural layer is (Al _x Ga _1-x ) _y In _{1 -y} P, and the range of x is 0.05~0.65, and the range of y is 0.45~0.55; when the first type coarsening restriction layer is a two-layer structure or a multi-periodic structure composed of a first structural layer and a second structural layer , the first structural layer is (Al _m Ga _1-m ) _n In _1-n P, the second structural layer is (A _a Ga _1-a ) _b In _1-b P, 0.05≤m≤0.65 , 0.05≤a≤0.65, 0.45≤n≤0.55, 0.45≤b≤0.55, and in the same period, the difference between In component n and In component b in the first structural layer and the second structural layer Less than 5%. 2. The LED epitaxial structure according to claim 1, wherein the period number k of the multi-periodic structure composed of the first structural layer ranges from 2 to 30. 3. The LED epitaxial structure according to claim 1, wherein the thickness of the first type roughening confinement layer is 100nm~1500nm. 4. The LED epitaxial structure of claim 1, wherein the period number k of the multi-periodic structure composed of the first structural layer and the second structural layer being alternately stacked ranges from 2 to 30. 5. The LED epitaxial structure of claim 1, wherein the first type roughening limiting layer is a single-layer structure composed of a first structural layer or a two-layer structure composed of a first structural layer and a second structural layer. During the structure, the gradient mode of the Al component in the linear gradient is a linear gradient from large to small or a linear gradient from small to large in a direction from the first type window layer to the first type confinement layer. 6. The LED epitaxial structure of claim 1, wherein in the same period, the maximum and minimum values of Al component a and Al component m in the first structural layer and the second structural layer are The difference in values is greater than 0.25. 7. The LED epitaxial structure of claim 1, wherein when the first type roughening limiting layer is a two-layer structure composed of a first structural layer and a second structural layer or a multi-periodic structure, the third The thickness of the first structural layer is 10nm~750nm, and the thickness of the second structural layer is 10nm~750nm. 8. The LED epitaxial structure of claim 1, wherein the first type roughened confinement layer is doped with Si or Te. 9. The LED epitaxial structure of claim 1, wherein the first type semiconductor layer further includes a first type ohmic contact layer, and the first type ohmic contact layer is located between the corrosion stop layer and the between the first type window layers. 10. The LED epitaxial structure of claim 1, wherein the second type semiconductor layer includes, from bottom to top, a second type waveguide layer, a second type confinement layer, a transition layer, and a second type window layer. and a type 2 ohmic contact layer. 11. The LED epitaxial structure of claim 1, wherein the first-type semiconductor layer is an N-type semiconductor layer, and the second-type semiconductor layer is a P-type semiconductor layer. 12. The LED epitaxial structure of claim 1, wherein the substrate includes a GaAs substrate or a Si substrate. 13. A method for preparing an LED epitaxial structure, characterized by comprising the following steps: provide a substrate; A bottom buffer layer, a corrosion stop layer, and a first-type semiconductor layer are sequentially grown on the substrate, wherein the first-type semiconductor layer includes, from bottom to top, a first-type window layer, a first-type roughening restriction layer, The first-type confinement layer and the first-type waveguide layer, and the first-type roughened confinement layer is a structural layer with a gradient Al component, and the gradient mode of the Al component in the first-type roughened confinement layer is a linear gradient. Or nonlinear gradient, the first type of coarsening restriction layer includes any one of four structures: a single-layer structure composed of the first structural layer, a multi-periodic structure composed of the first structural layer, the first structural layer and the third structural layer. A two-layer structure composed of two structural layers and a multi-periodic structure composed of the first structural layer and the second structural layer alternately stacked, wherein the first type roughening confinement layer is a single-layer structure composed of the first structural layer or a multi-periodic structure When , the first structural layer is (Al _x Ga _1-x ) _y In _1-y P, and x ranges from 0.05 to 0.65, and y ranges from 0.45 to 0.55; the first type roughening restriction layer When it is a two-layer structure or a multi-periodic structure composed of a first structural layer and a second structural layer, the first structural layer is (Al _m Ga _1-m ) _n In _1-n P, and the second structural layer is (Al _a Ga _1-a ) _b In _1-b P, 0.05≤m≤0.65, 0.05≤a≤0.65, 0.45≤n≤0.55, 0.45≤b≤0.55, and in the same period, the first structural layer The difference between the In component n and the In component b in the second structural layer is less than 5%; An active layer and a second type semiconductor layer are grown sequentially on the first type semiconductor layer. 14. The method for preparing an LED epitaxial structure according to claim 13, wherein the period number k of the multi-periodic structure composed of the first structural layer ranges from 2 to 30. 15. The method for preparing an LED epitaxial structure according to claim 13, wherein the thickness of the first type roughening confinement layer is 100nm~1500nm. 16. The method for preparing an LED epitaxial structure according to claim 13, wherein the period number k of the multi-periodic structure composed of the first structural layer and the second structural layer being alternately stacked ranges from 2 to 30. 17. The method for preparing an LED epitaxial structure according to claim 13, wherein the first type roughening restriction layer is a single-layer structure composed of a first structural layer or a first structural layer and a second structural layer. In the case of a two-layer structure, the gradient pattern of the Al component in the linear gradient is a linear gradient from large to small or from small to large in the direction from the first type window layer to the first type confinement layer. 18. The method for preparing an LED epitaxial structure according to claim 13, wherein in the same period, the maximum value of the Al component a and the Al component m in the first structural layer and the second structural layer is The difference between the value and the minimum value is greater than 0.25. 19. The method for preparing an LED epitaxial structure according to claim 13, wherein when the first type roughening restriction layer is a two-layer structure or a multi-periodic structure composed of a first structural layer and a second structural layer, The thickness of the first structural layer is 10nm~750nm, and the thickness of the second structural layer is 10nm~750nm. 20. The method for preparing an LED epitaxial structure according to claim 13, wherein the first type roughened confinement layer is doped with Si or Te. 21. The method for preparing an LED epitaxial structure according to claim 13, wherein the first type semiconductor layer further includes a first type ohmic contact layer, and the first type ohmic contact layer is located on the corrosion stop layer. and between the first type window layer. 22. The method for preparing an LED epitaxial structure according to claim 13, wherein the second type semiconductor layer includes, from bottom to top: a second type waveguide layer, a second type confinement layer, a transition layer, a second type Type window layer and second type ohmic contact layer. 23. The method for preparing an LED epitaxial structure according to claim 13, wherein the first-type semiconductor layer is an N-type semiconductor layer, and the second-type semiconductor layer is a P-type semiconductor layer. 24. The method for preparing an LED epitaxial structure according to claim 13, wherein the substrate includes a GaAs substrate or a Si substrate. 25. The method for preparing an LED epitaxial structure according to claim 13, wherein the preparation process of the epitaxial structure is a MOCVD process, a molecular beam epitaxy process, an HVPE process, a plasma-assisted chemical vapor deposition, and a sputtering method. any kind.