CN117059716A

CN117059716A - Infrared LED epitaxial structure and preparation method thereof

Info

Publication number: CN117059716A
Application number: CN202311218183.XA
Authority: CN
Inventors: 李森林; 毕京锋; 廖寅生; 薛龙; 赖玉财
Original assignee: Xiamen Silan Advanced Compound Semiconductor Co Ltd
Current assignee: Xiamen Silan Advanced Compound Semiconductor Co Ltd
Priority date: 2023-09-20
Filing date: 2023-09-20
Publication date: 2023-11-14

Abstract

The invention provides an infrared LED epitaxial structure and a preparation method thereof, wherein the infrared LED epitaxial structure sequentially comprises the following components from bottom to top: the semiconductor device comprises a substrate, a first type semiconductor layer, an active layer and a second type semiconductor layer, wherein the active layer sequentially comprises a front quantum well structure and a main quantum well structure from bottom to top, the front quantum well structure is a periodic structure formed by alternately growing a front well layer and a front barrier layer, the In component of the front well layer In the front period is larger than the In component of the front well layer In the rear period, and/or the thickness of the front well layer In the front period is larger than the thickness of the front well layer In the rear period. According to the invention, through the arrangement of the front quantum well structure, the luminous intensity and the temperature characteristic of the infrared LED can be improved.

Description

Infrared LED epitaxial structure and preparation method thereof

Technical Field

The invention relates to the technical field of semiconductors, in particular to an infrared LED epitaxial structure and a preparation method thereof.

Background

A light emitting diode (LED, light Emitting Diode) is a semiconductor solid state light emitting device that can directly convert electricity into light using a semiconductor PN junction as a light emitting material. In recent years, LEDs have been widely used because of their advantages of low power consumption, long lifetime, small volume, energy saving, environmental protection, etc., and particularly, as Metal Organic Chemical Vapor Deposition (MOCVD) epitaxial growth techniques are mature, infrared LEDs represented by gallium arsenide (GaAs) are rapidly developed, and large-scale commercialization is started.

In a light emitting diode, the carrier concentration in the active layer affects the radiative recombination probability of the carriers. When the carrier concentration is low, the probability of radiative recombination of electrons and holes becomes low, resulting in a decrease in the light emission intensity of the LED. Meanwhile, the temperature characteristic of the LED is also a key parameter of the performance of the LED. At high temperature, the internal thermal motion of the LED is aggravated, so that the carrier escape is increased, and the radiation recombination probability of the carrier is affected.

Disclosure of Invention

The invention aims to provide an infrared LED epitaxial structure and a preparation method thereof, which are used for improving the carrier concentration of an active layer and enhancing the quantum confinement effect, so as to improve the luminous intensity and the temperature characteristic of an infrared LED.

To achieve the above and other related objects, the present invention provides an infrared LED epitaxial structure comprising, in order from bottom to top: the semiconductor device comprises a substrate, a first type semiconductor layer, an active layer and a second type semiconductor layer, wherein the active layer sequentially comprises a front quantum well structure and a main quantum well structure from bottom to top, the front quantum well structure is a periodic structure formed by alternately growing a front well layer and a front barrier layer, the In component of the front well layer In the front period is greater than the In component of the front well layer In the rear period, and/or the thickness of the front well layer In the front period is greater than the thickness of the front well layer In the rear period.

Optionally, in the infrared LED epitaxial structure, the number of cycles of the front quantum well structure is 1-10.

Optionally, in the infrared LED epitaxial structure, the material of the pre-well layer includes In _xi Ga _1-xi As, and xi is more than or equal to 0 and less than or equal to 0.3; the saidThe material of the front barrier layer comprises Al _m Ga _1-m As _n P _1-n And m is more than or equal to 0 and less than or equal to 0.45,0.9, n is more than or equal to 1.

Optionally, in the infrared LED epitaxial structure, the total thickness of the pre-quantum well structure is 3 nm-120 nm, the single-period thickness of the pre-quantum well structure is 3 nm-12 nm, and the single-period thicknesses of the pre-well layer and the pre-barrier layer are 1.5 nm-10.5 nm.

Optionally, in the infrared LED epitaxial structure, in each period of the pre-quantum well structure, the In composition of the pre-well layer is a fixed composition or a graded composition, and when the In composition of the pre-well layer is a graded composition, the In composition of the pre-well layer gradually decreases along the direction of the first type semiconductor layer toward the second type semiconductor layer.

Optionally, in the infrared LED epitaxial structure, an energy band of a pre-well layer closest to the main quantum well structure in the pre-quantum well structure is lower than or equal to an energy band of the main quantum well structure.

Optionally, in the infrared LED epitaxial structure, the active layer further includes a post quantum well structure located on the main quantum well structure, and the post quantum well structure is a periodic structure formed by alternately growing a post well layer and a post barrier layer.

Optionally, in the infrared LED epitaxial structure, the number of cycles of the post quantum well structure is 1-10.

Optionally, in the infrared LED epitaxial structure, the material of the post-well layer includes In _z Ga _1-z As, and z is more than or equal to 0 and less than or equal to 0.30; the material of the back barrier layer comprises Al _jk Ga _1-jk As _dk P _1-dk And jk is more than or equal to 0 and less than or equal to 0.45,0.9, dk is more than or equal to 1.

Optionally, in the infrared LED epitaxial structure, in the post quantum well structure, an Al composition of the post barrier layer in a previous period is less than or equal to an Al composition of the post barrier layer in a subsequent period.

Optionally, in the infrared LED epitaxial structure, in the post quantum well structure, a P component of the post barrier layer in a previous period is less than or equal to a P component of the post barrier layer in a subsequent period.

Optionally, in the infrared LED epitaxial structure, in the post quantum well structure, a thickness of the post barrier layer in a previous period is less than or equal to a thickness of the post barrier layer in a subsequent period.

Optionally, in the infrared LED epitaxial structure, the total thickness of the post quantum well structure is 3 nm-120 nm, the single period thickness of the post quantum well structure is 3 nm-12 nm, and the single period thicknesses of the post well layer and the post barrier layer are 1.5 nm-10.5 nm.

Optionally, in the infrared LED epitaxial structure, in each period of the post quantum well structure, the Al composition of the post barrier layer is a fixed composition or a graded composition, and when the Al composition of the post barrier layer is a graded composition, the Al composition of the post barrier layer gradually increases along the direction of the first type semiconductor layer toward the second type semiconductor layer.

Optionally, in the infrared LED epitaxial structure, in each period of the post quantum well structure, a P-component of the post barrier layer is a fixed component or a graded component, and when the P-component of the post barrier layer is a graded component, the P-component of the post barrier layer gradually increases along a direction in which the first type semiconductor layer points to the second type semiconductor layer.

Optionally, in the infrared LED epitaxial structure, the main quantum well structure is a periodic structure formed by alternately growing a main well layer and a main barrier layer, materials, thicknesses and components of the front barrier layer are the same as those of the main barrier layer, and materials, thicknesses and components of the rear well layer are the same as those of the main well layer.

Optionally, in the infrared LED epitaxial structure, the number of cycles of the main quantum well structure is 2-10, the total thickness of the main quantum well structure is 6 nm-120 nm, the single cycle thickness of the main quantum well structure is 3 nm-12 nm, and the single cycle thicknesses of the main well layer and the main barrier layer are 1.5 nm-10.5 nm.

Optionally, in the infrared LED epitaxial structure, the infrared LED epitaxial structure further includes a bottom buffer layer and a corrosion stop layer stacked in sequence, the bottom buffer layer is located on the substrate, and the corrosion stop layer is located between the bottom buffer layer and the first type semiconductor layer.

Optionally, in the infrared LED epitaxial structure, the first type semiconductor layer includes a first type ohmic contact layer, a first type window layer, a first type limiting layer and a first barrier layer sequentially from bottom to top.

Optionally, in the infrared LED epitaxial structure, the second type semiconductor layer includes, in order from bottom to top: the second barrier layer, the second type limiting layer, the second type current expansion layer and the second type ohmic contact layer.

To achieve the above object and other related objects, the present invention also provides a method for manufacturing an infrared LED epitaxial structure, comprising the steps of:

Providing a substrate;

sequentially growing a first semiconductor layer and an active layer on the substrate, wherein the active layer sequentially comprises a pre-quantum well structure and a main quantum well structure from bottom to top, the pre-quantum well structure is a periodic structure formed by alternately growing a pre-well layer and a pre-barrier layer, the In component of the pre-well layer In the previous period is greater than the In component of the pre-well layer In the later period, and/or the thickness of the pre-well layer In the previous period is greater than the thickness of the pre-well layer In the later period;

and growing a second type semiconductor layer on the active layer.

Optionally, in the method for manufacturing an infrared LED epitaxial structure, the number of cycles of the front quantum well structure is 1-10.

Optionally, in the method for manufacturing an infrared LED epitaxial structure, the material of the pre-well layer includes In _xi Ga _1-xi As, and xi is more than or equal to 0 and less than or equal to 0.3; the material of the front barrier layer comprises Al _m Ga _1-m As _n P _1-n And m is more than or equal to 0 and less than or equal to 0.45,0.9, n is more than or equal to 1.

Optionally, in the method for preparing an infrared LED epitaxial structure, the total thickness of the pre-quantum well structure is 3 nm-120 nm, the single period thickness of the pre-quantum well structure is 3 nm-12 nm, and the single period thicknesses of the pre-well layer and the pre-barrier layer are 1.5 nm-10.5 nm.

Optionally, in the method for manufacturing an infrared LED epitaxial structure, in each cycle of the pre-quantum well structure, an In component of the pre-well layer is a fixed component or a graded component, and when the In component of the pre-well layer is a graded component, the In component of the pre-well layer gradually decreases along a direction of the first semiconductor layer pointing to the second semiconductor layer.

Optionally, in the method for manufacturing an infrared LED epitaxial structure, in the pre-quantum well structure, an energy band of a pre-well layer closest to the main quantum well structure is lower than or equal to an energy band of the main quantum well structure.

Optionally, in the method for manufacturing an infrared LED epitaxial structure, the active layer further includes a post quantum well structure located on the main quantum well structure, and the post quantum well structure is a periodic structure formed by alternately growing a post well layer and a post barrier layer.

Optionally, in the method for manufacturing an infrared LED epitaxial structure, the number of cycles of the post quantum well structure is 1-10.

Optionally, in the method for manufacturing an infrared LED epitaxial structure, the material of the post-well layer includes In _z Ga _1-z As, and z is more than or equal to 0 and less than or equal to 0.30; the material of the back barrier layer comprises Al _jk Ga _1-jk As _dk P _1-dk And jk is more than or equal to 0 and less than or equal to 0.45,0.9, dk is more than or equal to 1.

Optionally, in the method for manufacturing an infrared LED epitaxial structure, in the post quantum well structure, an Al composition of the post barrier layer in a previous period is less than or equal to an Al composition of the post barrier layer in a subsequent period.

Optionally, in the method for manufacturing an infrared LED epitaxial structure, in the post quantum well structure, a P component of the post barrier layer in a previous period is less than or equal to a P component of the post barrier layer in a subsequent period.

Optionally, in the method for manufacturing an infrared LED epitaxial structure, in the post quantum well structure, a thickness of the post barrier layer in a previous period is less than or equal to a thickness of the post barrier layer in a subsequent period.

Optionally, in the method for preparing the infrared LED epitaxial structure, the total thickness of the post quantum well structure is 3 nm-120 nm, the single period thickness of the post quantum well structure is 3 nm-12 nm, and the single period thicknesses of the post well layer and the post barrier layer are 1.5 nm-10.5 nm.

Optionally, in the method for manufacturing an infrared LED epitaxial structure, in each period of the post quantum well structure, the Al composition of the post barrier layer is a fixed composition or a graded composition, and when the Al composition of the post barrier layer is a graded composition, the Al composition of the post barrier layer gradually increases along the direction of the first semiconductor layer toward the second semiconductor layer.

Optionally, in the method for manufacturing an infrared LED epitaxial structure, in each period of the post quantum well structure, a P-component of the post barrier layer is a fixed component or a graded component, and when the P-component of the post barrier layer is a graded component, the P-component of the post barrier layer gradually increases along a direction in which the first type semiconductor layer points to the second type semiconductor layer.

Optionally, in the method for manufacturing an infrared LED epitaxial structure, the main quantum well structure is a periodic structure formed by alternately growing a main well layer and a main barrier layer, materials, thicknesses and components of the pre-barrier layer are the same as those of the main barrier layer, and materials, thicknesses and components of the post-well layer are the same as those of the main well layer.

Optionally, in the method for preparing an infrared LED epitaxial structure, the number of cycles of the main quantum well structure is 2-10, the total thickness of the main quantum well structure is 6-120 nm, the single cycle thickness of the main quantum well structure is 3-12 nm, and the single cycle thicknesses of the main well layer and the main barrier layer are 1.5-10.5 nm.

Optionally, in the method for preparing an infrared LED epitaxial structure, the method further includes: a bottom buffer layer and a corrosion-cut layer are grown between the substrate and the first type semiconductor layer, the bottom buffer layer being located on the substrate, the corrosion-cut layer being located between the bottom buffer layer and the first type semiconductor layer.

Optionally, in the method for manufacturing an infrared LED epitaxial structure, the first type semiconductor layer includes a first type ohmic contact layer, a first type window layer, a first type limiting layer and a first barrier layer sequentially from bottom to top.

Optionally, in the method for manufacturing an infrared LED epitaxial structure, the second type semiconductor layer includes, in order from bottom to top: the second barrier layer, the second type limiting layer, the second type current expansion layer and the second type ohmic contact layer.

Compared with the prior art, the technical scheme of the invention has the following beneficial effects:

in the infrared LED epitaxial structure provided by the present invention, the active layer includes a pre-quantum well structure and a main quantum well structure, and In the pre-quantum well structure, the In component of the pre-well layer In the previous period is greater than the In component of the pre-well layer In the next period, and/or the thickness of the pre-well layer In the previous period is equal to the thickness of the pre-well layer In the next period. The In component of the front trap layer In the previous period is larger than that of the front trap layer In the next period, and the thickness of the front trap layer In the previous period is larger than that of the front trap layer In the next period, so that the carrier concentration can be increased, the radiation recombination probability of the carrier is improved, the luminous intensity is improved, the carrier escape can be limited, the quantum confinement effect is enhanced, and the temperature characteristic of the infrared LED is improved; meanwhile, the luminescence wavelength of the front quantum well structure is ensured to be gradually close to that of the main quantum well structure, and the luminescence wavelength is prevented from deviating from the design range.

In addition, the active layer of the invention can also comprise a post quantum well structure, the post quantum well structure is a high potential barrier quantum well structure, in the post quantum well structure, the Al component of the post barrier layer of the previous period is less than or equal to the Al component of the post barrier layer of the next period, and/or the P component of the post barrier layer of the previous period is less than or equal to the P component of the post barrier layer of the next period, and/or the thickness of the post barrier layer of the previous period is less than or equal to the thickness of the post barrier layer of the next period. According to the invention, a high potential barrier can be formed by the Al component of the rear barrier layer of the previous period being smaller than or equal to the Al component of the rear barrier layer of the next period, the P component of the rear barrier layer of the previous period being smaller than or equal to the P component of the rear barrier layer of the next period or the thickness of the rear barrier layer of the previous period being smaller than or equal to the thickness of the rear barrier layer of the next period, and electrons can be blocked from migrating to the second type semiconductor layer, so that the carrier concentration in the active layer is improved, the radiation recombination probability is increased, the carrier overflow condition is reduced, and the temperature characteristic of the infrared LED is improved.

Drawings

FIG. 1 is a schematic diagram of an infrared LED epitaxial structure according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of an active layer according to an embodiment of the present invention;

FIG. 3 is a band diagram of an active layer according to an embodiment of the invention;

FIG. 4 is a flow chart of a method of fabricating an infrared LED epitaxial structure according to an embodiment of the present invention;

in the figures 1 to 4 of the drawings,

10-substrate, 11-bottom buffer layer, 12-corrosion stop layer, 13-first type ohmic contact layer, 14-first type window layer, 15-first type confinement layer, 16-first barrier layer, 17-active layer, 171-pre quantum well structure, 172-main quantum well structure, 173-post quantum well structure, 18-second barrier layer, 19-second type confinement layer, 20-second type current spreading layer, 21-second type ohmic contact layer.

Detailed Description

The infrared LED epitaxial structure and the preparation method thereof provided by the invention are further described in detail below with reference to the accompanying drawings and specific examples. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the drawings are in a very simplified form and are all to a non-precise scale, merely for convenience and clarity in aiding in the description of embodiments of the invention.

The inventor researches and discovers that increasing the carrier concentration in the quantum well has a great influence on the luminous intensity of the LED, and the quantum confinement effect of the LED is improved, so that the temperature characteristic of the LED is improved, the reduction amplitude of the luminous intensity of the LED at high temperature is reduced, and the performance of the LED is improved. Based on the structure, the invention provides the infrared LED epitaxial structure which can improve the luminous intensity and the temperature characteristic of the infrared LED.

Referring to fig. 1 and fig. 2, the infrared LED epitaxial structure provided by the present invention may sequentially include, from bottom to top: a substrate 10, a first type semiconductor layer, an active layer 17, and a second type semiconductor layer.

In this embodiment, the infrared LED epitaxial structure may further include a bottom buffer layer 11 and a corrosion-cut layer 12 stacked in order, the bottom buffer layer 11 being located on the substrate 10, and the corrosion-cut layer 12 being located between the bottom buffer layer 11 and the first type semiconductor layer.

The first type semiconductor layer is preferably an n type semiconductor layer, and may include a first type ohmic contact layer 13, a first type window layer 14, a first type confinement layer 15, and a first barrier layer 16 in this order from bottom to top.

The active layer 17 may include a pre-quantum well structure 171 and a main quantum well structure 172 in order from bottom to top. In addition, the active layer 17 may further include a post quantum well structure 173, and the post quantum well structure 173 is located on the main quantum well structure 172.

In this embodiment, the front quantum well structure 171 may emit light. The pre-quantum well structure 171 is a periodic structure formed by alternately growing a pre-well layer and a pre-barrier layer. One of the pre-well layers and one of the pre-barrier layers constitute one pre-quantum well. In this embodiment, the In composition of the pre-well layer In the previous period is greater than the In composition of the pre-well layer In the subsequent period, and/or the thickness of the pre-well layer In the previous period is greater than the thickness of the pre-well layer In the subsequent period. Wherein the former period refers to a period closer to the first semiconductor layer side in the adjacent period, and the latter period refers to a period closer to the second semiconductor layer side in the adjacent period. The In component of the front-end well layer In the previous period is greater than the In component of the front-end well layer In the subsequent period, so that the energy band of the front-end quantum well In the previous period is lower than the energy band of the front-end quantum well In the subsequent period (refer to fig. 3), the energy band of the front-end well layer closest to the main quantum well structure 172 is lower than or equal to the energy band of the main quantum well structure 172, the thickness of the front-end well layer In the previous period is greater than the thickness of the front-end well layer In the subsequent period, and the energy band of the front-end quantum well In the previous period can be greater than the energy band of the front-end quantum well In the subsequent period, therefore, the In component and the thickness change of the front-end well layer can increase the concentration of carriers, improve the radiation recombination probability of the carriers, improve the luminous intensity, limit the carrier escape, enhance the quantum limiting effect and improve the temperature characteristics of the infrared LED; while ensuring that the emission wavelength of the front quantum well structure 171 gradually approaches the emission wavelength of the main quantum well structure 172, preventing the emission wavelength from shifting out of the design range.

The main quantum well structure 172 is a periodic structure formed by alternately growing main well layers and main barrier layers. In this embodiment, the primary quantum well structure 172 serves as the primary light emitting layer.

In this embodiment, the post quantum well structure 173 may also emit light. The post quantum well structure 173 is a periodic structure formed by alternately growing a post well layer and a post barrier layer, and one post well layer and one post barrier layer form one post quantum well. In the post quantum well structure 173, an Al composition of the post barrier layer of a previous cycle is equal to or less than an Al composition of the post barrier layer of a subsequent cycle, and/or a P (phosphorus) composition of the post barrier layer of a previous cycle is equal to or less than a P composition of the post barrier layer of a subsequent cycle, and/or a thickness of the post barrier layer of a previous cycle is equal to or less than a thickness of the post barrier layer of a subsequent cycle. Wherein the former period refers to a period closer to the first semiconductor layer side in the adjacent period, and the latter period refers to a period closer to the second semiconductor layer side in the adjacent period. The Al component, the P component and the thickness of the rear barrier layer in the previous period are less than or equal to those of the rear barrier layer in the next period, so that electrons can be prevented from migrating to the second semiconductor layer, the carrier concentration in the active layer 17 is improved, the radiation recombination probability is increased, meanwhile, the carrier overflow condition is reduced, and the temperature characteristic of the infrared LED is improved.

The second type semiconductor layer may sequentially include, from bottom to top: a second barrier layer 18, a second type confinement layer 19, a second type current spreading layer 20, and a second type ohmic contact layer 21. In this embodiment, the polarities of the first type semiconductor layer and the second type semiconductor layer are opposite, for example, the first type semiconductor layer is an n type semiconductor layer, and the corresponding second type semiconductor layer is a p type semiconductor layer.

Referring to fig. 3, the method for preparing the infrared LED epitaxial structure may include the following steps:

step S1: providing a substrate 10;

step S2: a first semiconductor layer and an active layer 17 are sequentially grown on the substrate 10, the active layer 17 sequentially comprises a pre-quantum well structure 171 and a main quantum well structure 172 from bottom to top, the pre-quantum well structure 171 is a periodic structure formed by alternately growing a pre-well layer and a pre-barrier layer, the In component of the pre-well layer In the previous period is greater than the In component of the pre-well layer In the subsequent period, and/or the thickness of the pre-well layer In the previous period is greater than the thickness of the pre-well layer In the subsequent period;

step S3: a second type semiconductor layer is grown on the active layer 17.

In this embodiment, the preparation process of the infrared LED epitaxial structure may be any one of a Metal Organic Chemical Vapor Deposition (MOCVD) process, a Molecular Beam Epitaxy (MBE) process, a Hydrogenated Vapor Phase Epitaxy (HVPE) process, a plasma-assisted chemical vapor deposition (PECVD) process, a sputtering process, and an ultra-high vacuum chemical vapor deposition (UHVCVD) process, but is not limited thereto. Further, the preparation process of the infrared LED epitaxial structure is preferably MOCVD process. The following specific examples will be described by taking the MOCVD process as an example.

Step S1 is performed to provide a substrate 10. The substrate 10 is preferably a GaAs (gallium arsenide) substrate, but is not limited thereto. The substrate 10 may also be a Si (silicon) substrate, for example.

The infrared LED epitaxial structure of the present embodiment may further include a bottom buffer layer 11 and a corrosion-stopping layer 12 stacked in sequence, the bottom buffer layer 11 being located on the substrate 10, and the first semiconductor layer being located on the corrosion-stopping layer 12. Therefore, before executing step S2, the method for preparing the infrared LED epitaxial structure further includes: a bottom buffer layer 11 and a corrosion-cut layer 12 are grown in sequence on the substrate 10.

The bottom buffer layer 11 can eliminate the influence of the surface defect of the substrate 10 on the infrared LED epitaxial structure to the greatest extent, reduce the occurrence of defects and dislocation of the infrared LED epitaxial structure, and provide a flat interface for the next growth. The material of the bottom buffer layer 11 is preferably GaAs, but is not limited thereto. The bottom buffer layer 11 may be doped with a first type dopant, for example, an n-type dopant, and may be at least one of silicon (Si) and tellurium (Te), but is not limited thereto. Further, the first type dopant is preferably Si. In the present embodiment, the thickness of the bottom buffer layer 11 is preferably 100nm to 400nm _， For example 200nm.

After the step of growing the bottom buffer layer 11, a corrosion-stop layer 12 is grown on said bottom buffer layer 11. The material of the corrosion-cut layer 12 is preferably GaInP, but is not limited thereto. The corrosion-cut layer 12 may be doped with a first type dopant, for example, an n-type dopant, and may be at least one of silicon and tellurium, but is not limited thereto. Further, the first type dopant is preferably Si. In this embodiment, the thickness of the corrosion-cut layer 12 is preferably 150nm to 300nm, for example 200nm.

Step S2 is performed to grow a first type semiconductor layer on the substrate 10. When the infrared LED epitaxial structure further includes a bottom buffer layer 11 and a corrosion cut-off layer 12 stacked in this order, the first semiconductor layer is grown on the corrosion cut-off layer 12. In this embodiment, the first type semiconductor layer is preferably an n type semiconductor layer, and the first type semiconductor layer may include a first type ohmic contact layer 13, a first type window layer 14, a first type confinement layer 15, and a first barrier layer 16 in this order from bottom to top. Therefore, after the step of growing the etch stop layer 12, the first type ohmic contact layer 13, the first type window layer 14, the first type restriction layer 15, and the first barrier layer 16 are sequentially grown on the etch stop layer 12.

A first type ohmic contact layer 13 is grown on the corrosion cut-off layer 12. In this embodiment, the first type ohmic contact layer 13 is preferably an n type ohmic contact layer. The material of the first type ohmic contact layer 13 may be AlGaAs or GaAs, but is not limited thereto. Further, the material of the first type ohmic contact layer 13 is preferably GaAs. The first type ohmic contact layer 13 may be doped with a first type dopant, for example, an n type dopant, which may be one of silicon and tellurium, but is not limited thereto. Further, the first type dopant is preferably Si. In this embodiment, the thickness of the first type ohmic contact layer 13 is preferably 20nm to 150nm, for example, 50nm.

After the step of growing the first type ohmic contact layer 13, the first type window layer 14 is grown on the first type ohmic contact layer 13. The primary function of the first type window layer 14 is first type current spreading, light extraction and surface roughening. The first type window layer 14 is preferably an n-type window layer. The material of the first type window layer 14 is preferably AlGaAs, but is not limited thereto. The first type window layer 14 may be doped with a first type dopant, for example, an n type dopant, which may be at least one of silicon and tellurium, but is not limited thereto. Further, the first type dopant is preferably Si. In this embodiment, the thickness of the first type window layer 14 is preferably 3 μm to 8 μm, for example, 7 μm.

After the step of growing the first type window layer 14, the first type confinement layer 15 is grown on the first type window layer 14. The first type confinement layer 15 is preferably an n-type confinement layer. The material of the first type confinement layer 15 is preferably AlGaAs, but is not limited thereto. Further, the Al component content in the first type confinement layer 15 may be a conventionally employed Al component content, for example, 0.4. The Al composition in the first type confinement layer 15 of the present embodiment is preferably greater than the Al composition in the first type window layer 14. The first type confinement layer 15 may be doped with a first type dopant, for example, an n type dopant, and may be at least one of silicon and tellurium, but is not limited thereto. Further, the first type dopant is preferably Si. In this embodiment, the thickness of the first type confinement layer 15 is preferably 100nm to 500nm, for example 300nm.

After the step of growing the first type confinement layer 15, the first barrier layer 16 is grown on the first type confinement layer 15. The material of the first barrier layer 16 is preferably AlGaAs, but is not limited thereto. The first barrier layer 16 is preferably undoped, i.e. the first barrier layer 16 is preferably an undoped structural layer to block the first type dopants from entering the active layer 17. The Al composition in the first type confinement layer 15 of the present embodiment is preferably greater than the Al composition in the first barrier layer 16, and the high Al composition of the first type confinement layer 15 may provide better current conduction and lower optical refractive index. In this embodiment, the thickness of the first blocking layer 16 is preferably 100nm to 1000nm, for example 300nm.

After the step of growing the first barrier layer 16, an active layer 17 is grown on the first barrier layer 16. The active layer 17 includes a pre-quantum well structure 171 and a main quantum well structure 172, and may further include a post-quantum well structure 173. Thus, after the step of growing the first barrier layer 16, a pre-quantum well structure 171 is grown on the first barrier layer 16.

The pre-quantum well structure 171 is a periodic structure formed by alternately growing a pre-well layer and a pre-barrier layer, and the number of periods is preferably 1 to 10, for example 5. The total thickness of the front quantum well structure 171 for all periods is preferably 3nm to 120nm; the single period thickness of the pre-quantum well structure 171 is preferably 3nm to 12nm. In this embodiment, one of the pre-well layers and one of the pre-barrier layers constitute one pre-quantum well.

The material of the pre-well layer is preferably In _xi Ga _1-xi As, 0.ltoreq.xi.ltoreq.0.3, where i represents the weekThe period order, i, may range from 1 to 10. In this embodiment, the In component of the front-end well layer In the previous period is preferably greater than the In component of the front-end well layer In the next period, so that the energy band of the front-end quantum well In the previous period is lower than that of the front-end quantum well In the next period, the concentration of carriers can be increased, the radiation recombination probability of the carriers can be improved, carrier escape can be limited, the quantum confinement effect can be enhanced, and the temperature characteristic of the infrared LED can be improved; meanwhile, the energy band of the front-end well layer closest to the main quantum well structure is lower than or equal to that of the main quantum well structure, so that the light-emitting wavelength of the front-end quantum well structure 171 is ensured to be gradually close to the light-emitting wavelength of the main quantum well structure 172, and the light-emitting wavelength is prevented from deviating from the design range. Wherein the former period refers to a period closer to the first semiconductor layer side in the adjacent periods, and the latter period refers to a period closer to the second semiconductor layer side in the adjacent periods, and the smaller the period i is, the closer to the first semiconductor layer and the larger the period i is, the closer to the second semiconductor layer is. For example, the number of cycles of the pre-quantum well structure 171 is 2, and the material of the pre-well layer In the first cycle is In _x1 Ga _1-x1 As, x1=0.05; the material of the pre-well layer In the second period is In _x2 Ga _1-x2 As, x2=0.04. Further, in composition of the pre-well layer is a fixed composition or a graded composition In each period of the pre-quantum well structure 171, and In composition of the pre-well layer is preferably gradually decreased In a direction of the first type semiconductor layer toward the second type semiconductor layer when In composition of the pre-well layer is a graded composition. When the In component of the pre-well layer In each period is a graded component, lattice mismatch between the pre-well layer and other materials (such as the material of the post-barrier layer) can be reduced by graded In component, and the crystallization quality and growth performance of the active layer 17 can be improved; secondly, the limiting effect of the excitons can be improved through gradual change of In components, the service life of the excitons In the front trap layer is prolonged, and the luminous efficiency of the infrared LED is enhanced; finally, the light-emitting wavelength range of the infrared LED can be expanded through gradual change of In components, so that the infrared LED can emit wider spectrum and meet different application requirements. The In composition of the pre-well layer In each period isWhen the components are fixed, the growth process can be simplified by fixing the In component, and the complexity and error In the material growth process can be reduced; secondly, the component consistency of the front trap layer can be improved through the fixation of the In component, so that the performance of the infrared LED is more consistent, and the difference between batches is reduced; finally, the structural stability of the front trap layer can be improved through the fixation of the In component, the high temperature resistance of the material is enhanced, and the stability and the reliability of the infrared LED are improved.

In this embodiment, the thickness of the front-end well layer in a single period is preferably 1.5nm to 10.5nm, and the thickness of the front-end well layer in the previous period is preferably greater than that of the front-end well layer in the next period, so that the energy band of the front-end quantum well in the previous period is wider than that of the front-end quantum well in the next period, and further the front-end well layer in the previous period can accommodate more electrons, so that the concentration of carriers in the active layer 17 is increased, the radiation recombination probability is improved, and the luminous intensity and the temperature characteristic are improved; meanwhile, when the thickness of the front-end well layer is gradually reduced, the energy difference between the bound energy levels is increased, the light-emitting wavelength of the front-end quantum well structure 171 is also shortened, the light-emitting wavelength of the front-end quantum well structure 171 is gradually close to the light-emitting wavelength of the main quantum structure 172, and the light-emitting wavelength is prevented from deviating from the design range. For example, the number of cycles of the pre-quantum well structure 171 is 2, the thickness of the pre-well layer in the first cycle is 8nm, and the thickness of the pre-well layer in the second cycle is 6nm.

The pre-quantum well structure 171 of this embodiment also emits light, and the wavelength of the emitted light changes the forbidden bandwidth, thereby affecting the probability of recombination of radiation in the active layer 17. The present embodiment can control the light emission wavelength of the pre-quantum well structure 171 by either directly changing the In composition of the pre-well layer (i.e., the In composition of the pre-well layer In the previous period is greater than the In composition of the pre-well layer In the subsequent period) to adjust the light emission wavelength or by changing the thickness of the pre-well layer (i.e., the thickness of the pre-well layer In the previous period is greater than the thickness of the pre-well layer In the subsequent period). The two methods may be mixed, and preferably a single method is used to control the emission wavelength of the front quantum well structure 171. In this embodiment, the In composition and thickness of the pre-well layer are changed, and the depth and width of the pre-well layer are changed, so that the radiation recombination probability of the pre-quantum well structure 171 is affected, and the quantum confinement effect is also affected.

In this embodiment, the material of the front barrier layer is preferably Al _m Ga _1-m As _n P _1-n And 0.ltoreq.m.ltoreq. 0.45,0.9.ltoreq.n.ltoreq.1, e.g. Al _0.2 Ga _0.8 As _0.97 P _0.03 . The single period thickness of the pre-barrier layer is preferably 1.5nm to 10.5nm.

After the step of growing the pre-quantum well structure 171, a main quantum well structure 172 is grown on the pre-quantum well structure 171. The main quantum well structure 172 is a periodic structure formed by alternately growing main well layers and main barrier layers, and the number of periods is preferably 2 to 10, for example 4. The total thickness of the main quantum well structure 172 for all periods is preferably 6nm to 120nm, and the single period thickness of the main quantum well structure 172 is preferably 3nm to 12nm. In this embodiment, one main well layer and one main barrier layer constitute one main quantum well.

The main quantum well structure 172 serves as a main light emitting layer, and the material of the main well layer is preferably In _w Ga _1- _w As, wherein w is preferably In the range of 0.ltoreq.w.ltoreq.0.3, for example, the material of the main well layer is In _0.03 Ga _0.97 As. The thickness of the main well layer in a single period is preferably 1.5nm to 10.5nm.

The material of the main barrier layer is preferably Al _u Ga _1-u As _v P _1-v Where u is preferably in the range 0.ltoreq.u.ltoreq.0.45, v is preferably in the range 0.9.ltoreq.v.ltoreq.1, e.g. the material of the main barrier layer is Al _0.2 Ga _0.8 As _0.97 P _0.03 . The single period thickness of the main barrier layer is preferably 1.5nm to 10.5nm. In this embodiment, the material, thickness and composition of the main barrier layer are preferably the same as the material, thickness and composition of the pre-barrier layer. The front barrier layer and the main barrier layer have the same material, thickness and composition, can realize better lattice matching, and help to reduce lattice mismatchAnd stress problems, improving the crystallization quality and growth performance of the active layer 17; the carrier transport capability can be improved, electrons and holes can be more smoothly transported between the front quantum well structure 171 and the main quantum well structure 172, the recombination and loss of carriers can be reduced, and the diffusion and transport efficiency of the carriers can be improved; and the front barrier layer and the main barrier layer have the same materials, thicknesses and components, so that the growth process of the infrared LED can be simplified, the complexity and errors in the material growth process are reduced, the stability and the repeatability of the preparation process are improved, and the manufacturing cost is reduced.

After the step of growing the main quantum well structure 172, a post quantum well structure 173 is grown on the main quantum well structure 172. The post quantum well structure 173 is a periodic structure formed by alternately growing a post well layer and a post barrier layer, and the number of periods is preferably 1-10. The total thickness of the post quantum well structure 173 of all periods is preferably 3nm to 120nm, and the single period thickness of the post quantum well structure 173 is preferably 3nm to 12nm. In this embodiment, one post-well layer and one post-barrier layer constitute one post-quantum well.

The material of the post-well layer is preferably In _z Ga _1-z As, and 0.ltoreq.z.ltoreq.0.30, e.g. the material of the post-well layer is In _0.03 Ga _0.97 As. The single period thickness of the post-well layer is preferably 1.5nm to 10.5nm. In this embodiment, the material, thickness and composition of the post-well layer are preferably the same as those of the main well layer. The rear well layer and the main well layer have the same materials, thicknesses and components, so that better lattice matching can be realized, lattice mismatch and stress problems can be reduced, and the crystallization quality and the growth performance of the materials are improved; the carrier transporting capability can be improved, electrons and holes can be more smoothly transported between the rear quantum well structure 173 and the main quantum well structure 172, the recombination and loss of carriers can be reduced, and the diffusion and transport efficiency of the carriers can be improved; the rear well layer and the main well layer have the same material, thickness and composition, can simplify the growth process of the infrared LED, reduce the complexity and error in the material growth process, and is beneficial to improving the manufacturing processStability and repeatability of the preparation process, and reduced manufacturing cost.

The material of the back barrier layer is preferably Al _jk Ga _1-jk As _dk P _1-dk And jk is more than or equal to 0 and less than or equal to 0.45,0.9, dk is more than or equal to 1, wherein k represents a periodic sequence, and the range of k is 1-10. In this embodiment, the Al composition of the back barrier layer in the previous period is preferably equal to or less than the Al composition of the back barrier layer in the subsequent period. Wherein the former period refers to a period closer to the first semiconductor layer side in the adjacent periods, and the latter period refers to a period closer to the second semiconductor layer side in the adjacent periods, and the smaller the k is, the closer to the first semiconductor layer, and the larger the k is. For example, the number of cycles of the post quantum well structure 173 is 2, and the material of the post barrier layer in the first cycle is Al _0.25 Ga _0.75 As _0.97 P _0.03 The method comprises the steps of carrying out a first treatment on the surface of the The material of the rear barrier layer in the second period is Al _0.3 Ga _0.7 As _0.97 P _0.03 . The Al composition of the post-barrier layer in this embodiment represents the barrier height of the post-barrier layer, the gradual increase of the Al composition can make the barrier height of the post-barrier layer gradually increase, and the high barrier can limit the energy level of electrons or holes in the active layer 17, when the energy of the barrier is higher, only electrons or holes with energy lower than the barrier can exist in the active layer 17, and this energy level limitation makes the electrons or holes in the active layer 17 form discrete energy levels, similar to a two-dimensional energy level structure, so that the carrier radiation recombination probability in the active layer 17 can be improved; the high potential barrier has a limiting effect on the movement of electrons or holes, in the potential barrier, the electrons or holes can only move in the potential barrier and cannot freely diffuse to other areas, and the limitation ensures that the movement of the electrons or holes is limited in the size range of the potential barrier, so that one-dimensional, two-dimensional or three-dimensional limiting movement is formed, and the carrier overflow is reduced; the high potential barrier may form localized resonance states, i.e. electrons or holes within a certain energy range bounce back and forth in the active layer 17 and form standing wave-like situations, which have a certain energy and wave function distribution in the active layer 17.

In this embodiment, the P component of the back barrier layer in the previous period is preferably less than or equal to the P component of the back barrier layer in the next period. The P component in this embodiment functions similarly to the Al component to form a high potential barrier, thereby improving the probability of carrier radiation recombination in the active layer 17, reducing the carrier overflow condition, and improving the temperature characteristics of the infrared LED. For example, the number of cycles of the post quantum well structure 173 is 2, and the material of the post barrier layer in the first cycle is Al _0.25 Ga _0.75 As _0.97 P _0.03 The method comprises the steps of carrying out a first treatment on the surface of the The material of the rear barrier layer in the second period is Al _0.3 Ga _0.7 As _0.98 P _0.02 。

In the present embodiment, in each period of the post quantum well structure 173, the Al composition of the post barrier layer is a fixed composition or a graded composition, and when the Al composition of the post barrier layer is a graded composition, the Al composition of the post barrier layer is preferably gradually increased along the direction in which the first type semiconductor layer points to the second type semiconductor layer. In this embodiment, in each period of the post quantum well structure 173, the P-component of the post-barrier layer is a fixed component or a graded component, and when the P-component of the post-barrier layer is a graded component, the P-component of the post-barrier layer is preferably gradually increased along the direction in which the first-type semiconductor layer points to the second-type semiconductor layer. When the Al component (or P component) of the back barrier layer in each period is a graded component, the Al component (or P component) of the back barrier layer graded can reduce lattice mismatch and stress problems, and improve the crystallization quality and growth performance of the active layer 17; the gradual change of the Al component (or the P component) of the back barrier layer can also promote the transmission of carriers (electrons and holes) in the back barrier layer, reduce the recombination and loss of the carriers and improve the recombination efficiency and the luminous efficiency of the electrons and the holes. When the Al component (or P component) of the rear barrier layer in each period is a fixed component, the fixation of the Al component (or P component) can improve the structural stability of the rear barrier layer, so that the rear barrier layer is more resistant to high temperature, pressure and corrosion, and the stability and reliability of the infrared LED are improved; the fixation of the Al component (or the P component) can simplify the growth process of the infrared LED, and reduce the complexity and error in the material growth process, thereby reducing the preparation cost; the fixation of the Al component (or P component) can improve the component consistency of the back barrier layer, make the performance of the infrared LED more consistent, and reduce the lot-to-lot variation.

In this embodiment, the thickness of the back barrier layer in a single period is preferably 1.5nm to 10.5nm, and the thickness of the back barrier layer in the previous period is preferably less than or equal to the thickness of the back barrier layer in the next period, so as to form a high potential barrier, thereby improving the probability of carrier radiation recombination in the active layer 17, reducing the carrier overflow condition, and improving the temperature characteristics of the infrared LED. For example, the number of cycles of the post quantum well structure 173 is 2, the thickness of the post barrier layer in the first cycle is 8nm, and the thickness of the post barrier layer in the second cycle is 10nm.

The present embodiment can form a high potential barrier by three methods, one of which is to change the Al composition of the back-up barrier layer (i.e., the Al composition of the back-up barrier layer of the previous period is less than or equal to the Al composition of the back-up barrier layer of the next period) to raise the potential barrier so that more carriers remain in the active layer 17; another method is to change the P-component of the back-up barrier layer (i.e., the P-component of the back-up barrier layer of the previous cycle is less than or equal to the P-component of the back-up barrier layer of the next cycle) to raise the potential barrier to leave more carriers in the active layer 17; a third method is to leave more carriers in the active layer 17 by controlling the thickness of the back barrier layer (i.e., the thickness of the back barrier layer of the previous cycle is equal to or less than the thickness of the back barrier layer of the next cycle). The three methods may be mixed, preferably using a single method to form a high barrier.

Step S3 is executed: a second type semiconductor layer is grown on the active layer 17. The second type semiconductor layer may sequentially include, from bottom to top: a second barrier layer 18, a second type confinement layer 19, a second type window layer 20, and a second type ohmic contact layer 21. Thus, after the step of growing the active layer 17, a second barrier layer 18 is grown on the active layer 17.

The material of the second barrier layer 18 is preferably AlGaAs, but is not limited thereto. Further, the Al component content in the second barrier layer 18 may be a conventionally employed Al component content, for example, 0.3. The second barrier layer 18 is preferably undoped, i.e. the second barrier layer 18 is preferably an undoped structural layer to block the entry of dopants of the second type into the active layer 17. The thickness of the second barrier layer 18 is preferably 100 to 1000nm, for example 400nm.

After the step of growing the second barrier layer 18, a second type confinement layer 19 is grown on the second barrier layer 18. The second type confinement layer 19 is preferably a p-type confinement layer, and the second type confinement layer 19 is used to provide holes. In this embodiment, the first type confinement layer 15 and the second type confinement layer 19 mainly have two roles as confinement layers, on the one hand, minority carriers are limited not to overflow the active layer 17, and the composite light emitting efficiency is improved; on the other hand, as an important window, photons emitted from the active layer 17 are made to pass through the confinement layer very easily, so that the luminous efficiency of the infrared LED is improved.

The material of the second type confinement layer 19 is preferably AlGaAs, but is not limited thereto. Further, the Al component content in the second type confinement layer 19 may be a conventionally employed Al component content, for example, 0.4. The second type dopant, for example, a p-type dopant, may be at least one of magnesium (Mg) and carbon (C) doped in the second type confinement layer 19, but is not limited thereto. Further, the second type dopant is preferably C. The thickness of the second type confinement layer 19 is preferably 100nm to 500nm, for example 300nm.

After the step of growing the second type confinement layer 19, a second type current spreading layer 20 is grown on the second type confinement layer 19. The second type current spreading layer 20 is preferably a p type current spreading layer, and the second type current spreading layer 20 is used for current spreading to prevent current from being unevenly distributed over the infrared LED. The material of the second type current spreading layer 20 is preferably AlGaAs, but not limited thereto. The doping source of the second current spreading layer 20 is preferably C or Mg, but is not limited thereto. The thickness of the second type current spreading layer 20 is preferably 300nm to 3000nm, for example 800nm.

After the step of growing the second type current spreading layer 20, the second type ohmic contact layer 21 is grown on the second type current spreading layer 20. The second type ohmic contact layer 21 is for forming ohmic contact with a metal electrode. The material of the second type ohmic contact layer 21 is preferably GaP or AlGaAs, but is not limited thereto. The second type ohmic contact layer 21 may be doped with C. The thickness of the second type ohmic contact layer 21 is preferably 30nm to 150nm, for example, 50nm.

In summary, the active layer of the invention adopts the front quantum well structure, the main quantum well structure and the rear quantum well structure, which can effectively improve the carrier concentration in the active layer and enhance the quantum confinement effect.

The prepositive quantum well structure can store electrons, increase carrier concentration, improve the radiation recombination probability of carriers, further improve luminous intensity, limit carrier escape, enhance quantum limiting effect and improve the temperature characteristic of an infrared LED.

The rear quantum well structure is a high potential barrier quantum well structure, can block electrons from migrating to the second semiconductor layer, improves the carrier concentration in the active layer, increases the radiation recombination probability, and further improves the luminous intensity; meanwhile, carrier escape can be reduced, and the temperature characteristic of the infrared LED is improved.

In addition, it will be understood that while the invention has been described in terms of preferred embodiments, the above embodiments are not intended to limit the invention. Many possible variations and modifications of the disclosed technology can be made by anyone skilled in the art without departing from the scope of the technology, or the technology can be modified to be equivalent. Therefore, any simple modification, equivalent variation and modification of the above embodiments according to the technical substance of the present invention still fall within the scope of the technical solution of the present invention.

It is also to be understood that this invention is not limited to the particular methodology, compounds, materials, manufacturing techniques, uses, and applications described herein, as such may vary. It should also be understood that the terminology described herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present 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 otherwise. Thus, for example, reference to "a step" means a reference to one or more steps, and may include sub-steps. All conjunctions used should be understood in the broadest sense. Thus, the word "or" should be understood as having the definition of a logical "or" rather than a logical exclusive or "unless the context clearly indicates the contrary. Structures described herein will be understood to also refer to the functional equivalents of such structures. Language that may be construed as approximate should be construed unless the context clearly indicates the contrary.

Claims

1. An infrared LED epitaxial structure, comprising, in order from bottom to top: the semiconductor device comprises a substrate, a first type semiconductor layer, an active layer and a second type semiconductor layer, wherein the active layer sequentially comprises a front quantum well structure and a main quantum well structure from bottom to top, the front quantum well structure is a periodic structure formed by alternately growing a front well layer and a front barrier layer, the In component of the front well layer In the front period is greater than the In component of the front well layer In the rear period, and/or the thickness of the front well layer In the front period is greater than the thickness of the front well layer In the rear period.

2. The infrared LED epitaxial structure of claim 1, wherein the number of cycles of the front quantum well structure is from 1 to 10.

3. The infrared LED epitaxial structure of claim 1, wherein the material of the pre-well layer comprises In _xi Ga _1-xi As, and xi is more than or equal to 0 and less than or equal to 0.3; the material of the front barrier layer comprises Al _m Ga _1-m As _n P _1-n And m is more than or equal to 0 and less than or equal to 0.45,0.9, n is more than or equal to 1.

4. The infrared LED epitaxial structure of claim 1, wherein the total thickness of the pre-quantum well structure is from 3nm to 120nm, the single period thickness of the pre-quantum well structure is from 3nm to 12nm, and the single period thicknesses of the pre-well layer and the pre-barrier layer are both from 1.5nm to 10.5nm.

5. The infrared LED epitaxial structure of claim 1, wherein In composition of the pre-well layer is a fixed composition or a graded composition In each period of the pre-quantum well structure, and the In composition of the pre-well layer gradually decreases In a direction In which the first-type semiconductor layer points to the second-type semiconductor layer when the In composition of the pre-well layer is a graded composition.

6. The infrared LED epitaxial structure of claim 1, wherein in the pre-quantum well structure, the energy band of the pre-well layer closest to the main quantum well structure is lower than or equal to the energy band of the main quantum well structure.

7. The infrared LED epitaxial structure of claim 1, wherein the active layer further comprises a post quantum well structure on the main quantum well structure, and wherein the post quantum well structure is a periodic structure formed by alternately growing post well layers and post barrier layers.

8. The infrared LED epitaxial structure of claim 7, wherein the number of cycles of the post quantum well structure is from 1 to 10.

9. The infrared LED epitaxial structure of claim 7, wherein the material of the post-well layer comprises In _z Ga _1-z As, and z is more than or equal to 0 and less than or equal to 0.30; the material of the back barrier layer comprises Al _jk Ga _1-jk As _dk P _1-dk And jk is more than or equal to 0 and less than or equal to 0.45,0.9, dk is more than or equal to 1.

10. The infrared LED epitaxial structure of claim 7, wherein in the post quantum well structure, the Al composition of the post barrier layer of a previous cycle is less than or equal to the Al composition of the post barrier layer of a subsequent cycle.

11. The infrared LED epitaxial structure of claim 7, wherein in said post quantum well structure, the P-component of said post barrier layer of a previous cycle is less than or equal to the P-component of said post barrier layer of a subsequent cycle.

12. The infrared LED epitaxial structure of claim 7, wherein in the post quantum well structure, the thickness of the post barrier layer of a previous cycle is equal to or less than the thickness of the post barrier layer of a subsequent cycle.

13. The infrared LED epitaxial structure of claim 7, wherein the total thickness of the post quantum well structure is from 3nm to 120nm, the single period thickness of the post quantum well structure is from 3nm to 12nm, and the single period thicknesses of the post well layer and the post barrier layer are each from 1.5nm to 10.5nm.

14. The infrared LED epitaxial structure of claim 7, wherein in each cycle of the post quantum well structure, the Al composition of the post barrier layer is a fixed composition or a graded composition, and wherein when the Al composition of the post barrier layer is a graded composition, the Al composition of the post barrier layer gradually increases along the direction of the first type semiconductor layer toward the second type semiconductor layer.

15. The infrared LED epitaxial structure of claim 7, wherein in each cycle of the post quantum well structure, the P-component of the post barrier layer is a fixed or graded composition, and wherein when the P-component of the post barrier layer is a graded composition, the P-component of the post barrier layer gradually increases along the direction of the first type semiconductor layer toward the second type semiconductor layer.

16. The infrared LED epitaxial structure of claim 7, wherein the main quantum well structure is a periodic structure formed by alternately growing main well layers and main barrier layers, wherein the material, thickness and composition of the pre-barrier layer are the same as those of the main barrier layer, and wherein the material, thickness and composition of the post-well layer are the same as those of the main well layer.

17. The infrared LED epitaxial structure of claim 16, wherein the number of cycles of the primary quantum well structure is from 2 to 10, the total thickness of the primary quantum well structure is from 6nm to 120nm, the single cycle thickness of the primary quantum well structure is from 3nm to 12nm, and the single cycle thicknesses of the primary well layer and the primary barrier layer are each from 1.5nm to 10.5nm.

18. The infrared LED epitaxial structure of claim 1, further comprising a bottom buffer layer and a corrosion-cut layer stacked in sequence, the bottom buffer layer being located on the substrate, the corrosion-cut layer being located between the bottom buffer layer and the first type semiconductor layer.

19. The infrared LED epitaxial structure of claim 1, wherein the first type semiconductor layer comprises, in order from bottom to top, a first type ohmic contact layer, a first type window layer, a first type confinement layer, and a first barrier layer.

20. The infrared LED epitaxial structure of claim 1, wherein the second semiconductor layer comprises, in order from bottom to top: the second barrier layer, the second type limiting layer, the second type current expansion layer and the second type ohmic contact layer.

21. The preparation method of the infrared LED epitaxial structure is characterized by comprising the following steps of:

providing a substrate;

and growing a second type semiconductor layer on the active layer.

22. The method of claim 21, wherein the number of cycles of the pre-quantum well structure is 1-10.

23. The method of claim 21, wherein the material of the pre-well layer comprises In _xi Ga _1-xi As, and xi is more than or equal to 0 and less than or equal to 0.3; the material of the front barrier layer comprises Al _m Ga _1-m As _n P _1-n And m is more than or equal to 0 and less than or equal to 0.45,0.9, n is more than or equal to 1.

24. The method of claim 21, wherein the total thickness of the pre-quantum well structure is 3nm to 120nm, the single period thickness of the pre-quantum well structure is 3nm to 12nm, and the single period thicknesses of the pre-well layer and the pre-barrier layer are 1.5nm to 10.5nm.

25. The method of manufacturing an infrared LED epitaxial structure according to claim 21, wherein In composition of the pre-well layer is a fixed composition or a graded composition In each cycle of the pre-quantum well structure, and the In composition of the pre-well layer gradually decreases In a direction In which the first type semiconductor layer points to the second type semiconductor layer when the In composition of the pre-well layer is a graded composition.

26. The method of claim 21, wherein the energy band of the pre-well layer closest to the main quantum well structure in the pre-quantum well structure is lower than or equal to the energy band of the main quantum well structure.

27. The method of claim 21, wherein the active layer further comprises a post quantum well structure on the main quantum well structure, and the post quantum well structure is a periodic structure formed by alternately growing a post well layer and a post barrier layer.

28. The method of claim 27, wherein the number of cycles of the post quantum well structure is 1-10.

29. The method of claim 27, wherein the material of the post-well layer comprises In _z Ga _1-z As, and z is more than or equal to 0 and less than or equal to 0.30; the material of the back barrier layer comprises Al _jk Ga _1-jk As _dk P _1-dk And jk is more than or equal to 0 and less than or equal to 0.45,0.9, dk is more than or equal to 1.

30. The method of claim 27, wherein in the post quantum well structure, the Al composition of the post barrier layer of a previous cycle is less than or equal to the Al composition of the post barrier layer of a subsequent cycle.

31. The method of claim 27, wherein in the post quantum well structure, the P-component of the post barrier layer of a previous cycle is less than or equal to the P-component of the post barrier layer of a subsequent cycle.

32. The method of claim 27, wherein the thickness of the back barrier layer in the previous cycle is less than or equal to the thickness of the back barrier layer in the next cycle in the back quantum well structure.

33. The method of claim 27, wherein the total thickness of the post quantum well structure is 3nm to 120nm, the single period thickness of the post quantum well structure is 3nm to 12nm, and the single period thicknesses of the post well layer and the post barrier layer are 1.5nm to 10.5nm.

34. The method of manufacturing an infrared LED epitaxial structure of claim 27, wherein in each period of the post quantum well structure, the Al composition of the post barrier layer is a fixed composition or a graded composition, and wherein when the Al composition of the post barrier layer is a graded composition, the Al composition of the post barrier layer gradually increases in a direction in which the first type semiconductor layer points to the second type semiconductor layer.

35. The method of claim 27, wherein the P-component of the back barrier layer is a fixed or graded component in each cycle of the back quantum well structure, and wherein the P-component of the back barrier layer gradually increases in a direction of the first type semiconductor layer toward the second type semiconductor layer as the P-component of the back barrier layer is a graded component.

36. The method of claim 27, wherein the main quantum well structure is a periodic structure formed by alternately growing main well layers and main barrier layers, and the material, thickness and composition of the pre-barrier layer are the same as those of the main barrier layer, and the material, thickness and composition of the post-well layer are the same as those of the main well layer.

37. The method of claim 36, wherein the number of cycles of the main quantum well structure is 2-10, the total thickness of the main quantum well structure is 6-120 nm, the single cycle thickness of the main quantum well structure is 3-12 nm, and the single cycle thicknesses of the main well layer and the main barrier layer are 1.5-10.5 nm.

38. The method of fabricating an infrared LED epitaxial structure of claim 21, further comprising: a bottom buffer layer and a corrosion-cut layer are grown between the substrate and the first type semiconductor layer, the bottom buffer layer being located on the substrate, the corrosion-cut layer being located between the bottom buffer layer and the first type semiconductor layer.

39. The method for manufacturing an infrared LED epitaxial structure of claim 21, wherein the first type semiconductor layer comprises a first type ohmic contact layer, a first type window layer, a first type confinement layer and a first barrier layer in this order from bottom to top.

40. The method for manufacturing an infrared LED epitaxial structure of claim 21, wherein the second type semiconductor layer comprises, in order from bottom to top: the second barrier layer, the second type limiting layer, the second type current expansion layer and the second type ohmic contact layer.