Red light LED epitaxial structure and manufacturing method thereof, and LED chip

Abstract

The application discloses a red light LED epitaxial structure and a manufacturing method thereof, and an LED chip. The epitaxial structure comprises a substrate, an N-type layer, an active layer and a P-type layer which are arranged in layers, wherein the P-type layer comprises a P-type limiting layer which is an AlGaInP layer and comprises at least two sub-P-type limiting layers. The difference in band gap of each sub-P-type limiting layer relative to the active layer increases in the direction away from the active layer, and the difference between the band gaps of adjacent sub-P-type limiting layers is within the range of 0.115 eV to 0.228 eV, inclusive. The P-type limiting layer is configured in a stepped band gap increasing structure to construct a steep band mutation, effectively reflect hot carriers and inhibit the thermal leakage of carriers from the active region to the P-type layer, thereby improving the light emitting efficiency of the LED in a high temperature (such as 85 DEG C and above) environment.

Description

Technical Field

[0001] This application relates to the field of LED technology, and in particular to a red LED epitaxial structure and its fabrication method, as well as an LED chip. Background Technology

[0002] AlGaInP-based red LEDs, as core optoelectronic devices in solid-state lighting and display backlighting, have been widely used in full-color displays, traffic lights, automotive taillights, and plant lighting due to the direct bandgap emission characteristics of their material system in the visible red light band. However, as downstream applications increasingly demand higher display quality, lighting performance, and system reliability, AlGaInP-based red LEDs need to maintain stable optoelectronic performance over a wider temperature range. In practical applications, the optoelectronic performance of existing AlGaInP-based red LEDs significantly degrades when exposed to temperatures of 85°C or higher. Summary of the Invention

[0003] In view of the above problems, this application provides a red LED epitaxial structure and its fabrication method, as well as an LED chip, to improve the photoelectric performance of red LEDs in high-temperature environments of 85°C and above. The specific solution is as follows:

[0004] An epitaxial structure for a red LED includes: a substrate, an N-type layer, an active layer, and a P-type layer stacked together. The P-type layer includes a P-type confinement layer, which is an AlGaInP layer. The P-type confinement layer includes at least two sub-P-type confinement layers. The bandgap difference between each sub-P-type confinement layer and the active layer increases in a direction away from the active layer, and the bandgap difference between adjacent sub-P-type confinement layers is in the range of 0.115 eV to 0.228 eV, including the endpoint values.

[0005] Optionally, the thickness of the P-type confinement layer ranges from 780 nm to 1050 nm, including the endpoint values;

[0006] The difference in bandgap width between the sub-P-type confinement layer and the active layer ranges from 1.28 eV to 2.22 eV, including the endpoint values;

[0007] The number of sub-P-type confinement layers included in the P-type confinement layer is 2 or 3.

[0008] Optionally, the thickness of each of the at least two sub-P-type confinement layers increases in the direction away from the active layer;

[0009] And / or,

[0010] The energy difference between the Fermi level and the valence band top of each of the at least two sub-P-type confinement layers increases in the direction away from the active layer.

[0011] Optionally, the at least two sub-P-type confinement layers include a first sub-P-type confinement layer, a second sub-P-type confinement layer, and a third sub-P-type confinement layer stacked sequentially along the direction away from the active layer; the bandgap difference between the first sub-P-type confinement layer and the active layer ranges from 1.52 eV to 1.75 eV, including the endpoint values; the bandgap difference between the second sub-P-type confinement layer and the active layer ranges from 1.75 eV to 1.98 eV, including the endpoint values; and the bandgap difference between the third sub-P-type confinement layer and the active layer ranges from 1.98 eV to 2.22 eV, including the endpoint values.

[0012] And / or,

[0013] The energy difference between the Fermi level and the valence band top of the first sub-P-type confinement layer ranges from 0.031 eV to 0.060 eV, including the endpoints; the energy difference between the Fermi level and the valence band top of the second sub-P-type confinement layer ranges from 0.042 eV to 0.078 eV, including the endpoints; and the energy difference between the Fermi level and the valence band top of the third sub-P-type confinement layer ranges from 0.060 eV to 0.120 eV, including the endpoints.

[0014] Optionally, the at least two sub-P-type confinement layers include a first sub-P-type confinement layer, a second sub-P-type confinement layer, and a third sub-P-type confinement layer stacked sequentially along the direction away from the active layer; the thickness of the first sub-P-type confinement layer ranges from 80 nm to 120 nm, including the endpoint values; the thickness of the second sub-P-type confinement layer ranges from 250 nm to 350 nm, including the endpoint values; and the thickness of the third sub-P-type confinement layer ranges from 450 nm to 550 nm, including the endpoint values.

[0015] Optionally, the P-type confinement layer further includes: at least one intrinsic spacer layer, wherein the intrinsic spacer layer is located between two adjacent sub-P-type confinement layers or between the at least two sub-P-type confinement layers and the active layer.

[0016] Optionally, when the P-type confinement layer includes at least two intrinsic spacer layers, the different intrinsic spacer layers are located at different positions in the P-type confinement layer in the direction away from the active layer.

[0017] Optionally, the film layer located on the side of the intrinsic spacer layer facing the active layer and adjacent to the intrinsic spacer layer is the first film layer; the film layer located on the side of the intrinsic spacer layer away from the active layer and adjacent to the intrinsic spacer layer is the second film layer.

[0018] The conduction barrier height of the intrinsic spacer layer is located between the conduction barrier height of the first film layer and the conduction barrier height of the second film layer, or is the same as the conduction barrier height of the first film layer, or is the same as the conduction barrier height of the second film layer.

[0019] Optionally, the thickness of the intrinsic spacer layer ranges from 5 nm to 15 nm, including the endpoint values.

[0020] An LED chip comprising the red LED epitaxial structure described in any of the preceding claims.

[0021] A method for fabricating a red LED epitaxial structure, used to fabricate the red LED epitaxial structure described in any of the above claims, the method comprising:

[0022] Provide substrate;

[0023] An N-type layer, an active layer, and a P-type layer are sequentially fabricated on the first side of the substrate. The P-type layer includes a P-type confinement layer, which is an AlGaInP layer. The P-type confinement layer includes at least two sub-P-type confinement layers. The bandgap difference between each sub-P-type confinement layer and the active layer increases in the direction away from the active layer, and the difference between the bandgap widths of adjacent sub-P-type confinement layers is in the range of 0.115 eV to 0.228 eV, including the endpoint values.

[0024] In the technical solution provided in this application embodiment, the P-type confinement layer includes at least two sub-P-type confinement layers. The bandgap difference between each sub-P-type confinement layer and the active layer increases in the direction away from the active layer, and the difference between the bandgap widths of adjacent sub-P-type confinement layers is in the range of 0.115eV to 0.228eV, including the endpoint value. This ensures the growth quality of the P-type confinement layer while forming a gradually increasing discrete step-like bandgap distribution in the P-type confinement layer. As a result, the valence band barrier of the P-type confinement layer relative to the active layer increases step by step, and abrupt heterojunctions are formed between adjacent sub-P-type confinement layers, producing steep bandgap changes. This effectively reflects hot carriers and suppresses heat leakage of carriers from the active region to the P-type layer, thereby improving the luminous efficiency of LEDs in high-temperature environments (such as 85°C and above). Attached Figure Description

[0025] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. Throughout the drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic, and the originals and elements are not necessarily drawn to scale.

[0026] Figure 1A schematic diagram of a red LED epitaxial structure provided in this application;

[0027] Figure 2 A structural diagram of another red LED epitaxial structure provided in this application;

[0028] Figure 3 A structural diagram of another red LED epitaxial structure provided in this application;

[0029] Figure 4 A schematic diagram of the band structure when the aluminum composition is uniform or continuously gradually varied for a P-type confinement layer.

[0030] Figure 5 In the embodiments of this application, the P-type confinement layer typically adopts a discrete stepwise increase in aluminum composition, synchronous increase in thickness, and synchronous decrease in doping concentration for each sub-P-type confinement layer, and an intrinsic spacer layer is provided between adjacent sub-P-type confinement layers.

[0031] Figure 6 A flowchart illustrating a method for fabricating a red LED epitaxial structure provided in this application. Detailed Implementation

[0032] The embodiments of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0033] The terminology used in the embodiments section of this application is only for explaining specific embodiments of this application and is not intended to limit this application. Various modifications and variations can be made to this application without departing from its spirit or scope. Moreover, with the development of technology and the emergence of new scenarios, the technical solutions provided by the embodiments of this application are equally applicable to similar technical problems, which is obvious to those skilled in the art. Therefore, this application is intended to cover modifications and variations of this application that fall within the scope of the corresponding claims (the claimed technical solutions) and their equivalents. It should be noted that the embodiments provided in this application can be combined with each other without contradiction.

[0034] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] As described in the background section, the photoelectric performance of existing AlGaInP-based red LEDs will significantly degrade when exposed to high-temperature environments of 85°C and above.

[0036] The inventors discovered that this is because the valence band barrier between the P-type confinement layer and the multi-quantum well active region in current AlGaInP-based red LEDs is limited in height. At high temperatures, the thermal motion of charge carriers intensifies, and after gaining sufficient kinetic energy, they have a high probability of crossing the valence band barrier, causing thermal leakage from the multi-quantum well active region to the P-type region. This results in a decrease in the concentration of charge carriers participating in radiative recombination within the multi-quantum well active region, a significant decrease in carrier recombination efficiency, severe efficiency roll-off, and accelerated device aging and failure, leading to a significant degradation of the high-temperature optoelectronic performance of AlGaInP-based red LEDs.

[0037] To suppress the aforementioned reverse thermal leakage of charge carriers, the following solutions were attempted:

[0038] One technical solution is to use a uniformly doped P-type AlGaInP layer with a single Al composition as the P-type confinement layer. For example, a uniformly doped P-type AlGaInP layer with an Al composition of approximately 0.7 can be used as the P-type confinement layer. However, this P-type confinement layer can only provide a valence band barrier of approximately 0.16 eV (ΔEv). According to the Boltzmann distribution law, at 85°C, the probability of holes gaining enough energy to overcome this valence band barrier exceeds 40%, resulting in a large number of holes being unable to participate in effective luminescent recombination, which still causes a sharp drop in the efficiency of AlGaInP-based red LEDs at high temperatures.

[0039] Another technical solution is to adopt a continuously gradient structure, in which the Al composition increases linearly along the growth direction within the P-type confinement layer, and the doping concentration also increases accordingly, aiming to achieve a balance between injection efficiency and carrier confinement. However, the continuously gradient energy band in this scheme cannot form a steep barrier gradient, and the highly doped region is prone to inducing Zener tunneling, resulting in limited suppression of hot-emission carrier leakage. The high-temperature leakage rate of AlGaInP-based red LEDs is still higher than 15%.

[0040] In view of this, embodiments of this application provide a red LED epitaxial structure, such as... Figure 1As shown, the structure includes a substrate 100, an N-type layer 200, an active layer 300, and a P-type layer 400 stacked together. The P-type layer 400 includes a P-type confinement layer 402, which comprises at least two sub-P-type confinement layers. The bandgap difference between each of the at least two sub-P-type confinement layers and the active layer 300 increases in a direction away from the active layer 300, and the bandgap difference between adjacent sub-P-type confinement layers is between 0.115 eV and 0.228 eV. Within the range, including endpoint values, a gradually increasing discrete step-like bandgap distribution is formed in the P-type confinement layer while ensuring the growth quality of the P-type confinement layer. This results in a gradual increase in the valence band barrier of the P-type confinement layer relative to the active layer, and the formation of abrupt heterojunctions between adjacent sub-P-type confinement layers, producing steep bandgap changes. This effectively reflects hot carriers and suppresses heat leakage of carriers from the active region to the P-type layer, thereby improving the luminous efficiency of LEDs in high-temperature environments (such as 85°C and above).

[0041] Optionally, in some embodiments of this application, the substrate 100 may be a GaAs substrate as the base material for epitaxial growth; the N-type layer 200 may include an n-GaAs buffer layer 201, an N-type window layer 202, an N-type confinement layer 203, and an N-type waveguide layer 204 sequentially stacked on the substrate 100; the active layer 300 may be a multiple quantum well (MQW) active region; the P-type layer 400 includes a P-type waveguide layer 401, a P-type confinement layer 402, a P-type window layer 403, and a P-type contact layer 404 stacked along a direction away from the active layer 300. However, this application does not limit this, and the specific choice depends on the circumstances.

[0042] Specifically, in some embodiments of this application, an n-GaAs buffer layer is grown on the substrate to reduce the lattice defect density on the substrate surface, providing a smooth growth surface for subsequent epitaxial layers; an N-type window layer is a high-conductivity material layer to provide a lateral expansion channel for electrons, ensuring uniform distribution of the injected current, while its wider bandgap facilitates the emission of light generated by the active layer from the front of the device, improving light extraction efficiency; an N-type confinement layer provides electron injection and spatially confines carriers, trapping electrons and holes within the active layer; an N-type waveguide layer confines the light field near the active layer while preventing doped ions in the N-type layer from diffusing into the active layer; the active layer is a complex electron-hole layer... The region of light recombination is the core region that determines the emission wavelength and luminous efficiency of the device. The P-type waveguide layer is used to protect the active region of the multi-quantum well and prevent doped ions in the P-type layer from diffusing into the active region of the multi-quantum well to form non-radiative recombination centers. The P-type confinement layer is used to provide hole injection and plays a spatial confinement role for charge carriers, confining holes within the active region of the multi-quantum well. The P-type window layer is a high-conductivity material layer used to provide a lateral expansion channel for holes, so that the injected current is evenly distributed. At the same time, its wide bandgap is conducive to the light generated in the active region being emitted from the front of the device, improving the light extraction efficiency. The P-type contact layer is a highly doped layer used to form an ohmic contact with the subsequently formed P-type electrode and reduce the contact resistance.

[0043] Optionally, in some embodiments of this application, the n-GaAs buffer layer, N-type window layer, and N-type confinement layer are N-type doped layers, with Si ions as dopants; the N-type waveguide layer is an unintentionally doped layer; and the N-type window layer, N-type confinement layer, and N-type waveguide layer are AlGaInP layers. The active layer includes periodically arranged quantum barrier layers and quantum well layers, wherein the quantum barrier layer can be an AlGaInP layer, and the quantum well layer can be a GaInP layer. The P-type waveguide layer is an unintentionally doped layer, the P-type confinement layer and P-type window layer are P-type doped layers, with Mg ions as dopants; the P-type contact layer is a P-type doped layer, with C ions as dopants; the P-type waveguide layer and P-type confinement layer are AlGaInP layers; and the P-type window layer and P-type contact layer are GaP layers. However, this application does not limit this, and the specific implementation depends on the circumstances.

[0044] It should be noted that, in the embodiments of this application, both the P-type waveguide layer and the P-type confinement layer are AlGaInP layers, specifically, they can be represented as (Al x Ga 1-x ) 0.5 In 0.5 P, where x represents the value of the aluminum composition in the layer. Optionally, in some embodiments of this application, the aluminum composition in the P-type waveguide layer ranges from 0.4 to 0.5, including the endpoint value, and the thickness of the P-type waveguide layer ranges from 150 nm to 250 nm, including the endpoint value, but this application does not limit this and it depends on the specific circumstances.

[0045] Optionally, in some embodiments of this application, the aluminum composition of each of the at least two sub-P-type confinement layers increases in the direction away from the active layer 300, and the difference in aluminum composition between adjacent sub-P-type confinement layers is in the range of 0.05 to 0.1, including the endpoint value, so that the difference in bandgap width between each of the at least two sub-P-type confinement layers and the active layer increases in the direction away from the active layer, and the difference in bandgap width between adjacent sub-P-type confinement layers is in the range of 0.115 eV to 0.228 eV, including the endpoint value.

[0046] Specifically, in this embodiment, the P-type confinement layer includes at least two sub-P-type confinement layers. The aluminum composition of each sub-P-type confinement layer increases in the direction away from the active layer, and the difference in aluminum composition between adjacent sub-P-type confinement layers is in the range of 0.05 to 0.1, including endpoint values. This allows for a discrete, stepped aluminum composition distribution within the P-type confinement layer while ensuring the growth quality of the P-type confinement layer. This results in abrupt heterojunctions between adjacent sub-P-type confinement layers, thereby gradually increasing the valence band barrier of the P-type confinement layer. Compared to traditional confinement layer structures with a single aluminum composition or continuously varying aluminum composition, the stepped aluminum composition structure of the P-type confinement layer in this embodiment can create a steep band gap, effectively reflecting hot carriers and suppressing heat leakage of carriers from the active region to the P-type layer, thereby improving the luminous efficiency of the LED in high-temperature environments (such as 85°C and above).

[0047] Optionally, in some embodiments of this application, the bandgap difference between each sub-P-type confinement layer and the active layer ranges from 1.28 eV to 2.22 eV, including the endpoint values, to ensure that each sub-P-type confinement layer can form an effective valence band barrier, while avoiding the problem of increased lattice mismatch caused by excessively high bandgap differences relative to the active layer. However, this application does not limit this, and it depends on the specific circumstances.

[0048] Based on the above embodiments, in some embodiments of this application, the aluminum composition in each sub-P-type confinement layer ranges from 0.55 to 0.95, including the endpoint values, so that the difference in bandgap width between each sub-P-type confinement layer and the active layer ranges from 1.28 eV to 2.22 eV, including the endpoint values. This ensures that each sub-P-type confinement layer can form an effective valence band barrier, while avoiding the problem of increased lattice mismatch caused by excessively high aluminum composition. However, this application does not limit this, and it depends on the specific circumstances.

[0049] Optionally, in some embodiments of this application, the aluminum composition difference between adjacent sub-P-type confinement layers is the same. For example, when the P-type confinement layer includes two sub-P-type confinement layers, the aluminum composition of the first sub-P-type confinement layer may be 0.65, and the aluminum composition of the second sub-P-type confinement layer may be 0.75; or, the aluminum composition of the first sub-P-type confinement layer may be 0.70, and the aluminum composition of the second sub-P-type confinement layer may be 0.80; or, the aluminum composition of the first sub-P-type confinement layer may be 0.75, and the aluminum composition of the second sub-P-type confinement layer may be 0.85. When the P-type confinement layer includes three sub-P-type confinement layers, the aluminum composition of the three sub-P-type confinement layers may be 0.65, 0.75, and 0.85, or 0.70, 0.80, and 0.90, with an adjacent difference of 0.1. However, this application does not impose any limitations on this, and it depends on the specific circumstances. As long as the aluminum composition in each sub-P-type confinement layer is in the range of 0.55 to 0.95, including the endpoint values, and the difference in aluminum composition between adjacent sub-P-type confinement layers is maintained at 0.05 to 0.1, including the endpoint values, it is acceptable.

[0050] In some other embodiments of this application, the aluminum composition difference between adjacent P-type confinement layers can also be different. Since the distribution of hot carriers shows that higher energy hot carriers are fewer in number, and the number of hot carriers drops significantly with each energy increase, with over 90% of hot carriers concentrated in the medium energy range, in some optional embodiments of this application, when the aluminum composition difference between adjacent P-type confinement layers is different, the aluminum composition difference decreases along the direction away from the active layer. That is, the aluminum composition difference between adjacent P-type confinement layers closer to the active layer is greater than the aluminum composition difference between adjacent P-type confinement layers farther from the active layer, thus forming a barrier change that is steep at the beginning and gentle at the end. For example, the P-type confinement layer includes a first sub-P-type confinement layer, a second sub-P-type confinement layer, and a third sub-P-type confinement layer arranged in a direction away from the active layer. The aluminum composition difference between the first sub-P-type confinement layer and the second sub-P-type confinement layer (e.g., 0.1) is greater than the aluminum composition difference between the second sub-P-type confinement layer and the third sub-P-type confinement layer (e.g., 0.05), so that the barrier of the P-type confinement layer rapidly jumps from a lower aluminum composition to a higher aluminum composition, thereby blocking more than 99% of medium and high energy hot carriers at once.

[0051] Furthermore, the use of a lower aluminum composition (e.g., 0.75) in the first sub-P-type confinement layer can reduce the barrier height that needs to be overcome for cold hole injection into the active region. For every point the barrier is lowered, the number of holes that can overcome the barrier increases exponentially. Therefore, compared to the small difference in aluminum composition between adjacent sub-P-type confinement layers far from the active layer, the large difference in aluminum composition between adjacent sub-P-type confinement layers close to the active layer can ensure a higher aluminum composition in the second sub-P-type confinement layer while keeping the aluminum composition in the first sub-P-type confinement layer lower. This results in an injection efficiency of more than twice as high for the active layer, significantly improving the luminous efficiency under low current.

[0052] Furthermore, since the third sub-P-type confinement layer targets the very few high-energy hot carriers (accounting for less than 1%) that have already been filtered out by the second sub-P-type confinement layer (99%), a small transition can be formed by using a sub-P-type confinement layer with a small difference in aluminum composition between adjacent sub-P-type confinement layers (e.g., 0.05) to block the remaining hot carriers. This also avoids the difficulties in P-type doping and the risk of interface oxidation caused by an excessively high aluminum composition in the third sub-P-type confinement layer.

[0053] Therefore, it can be seen that the red LED epitaxial structure provided in this application can achieve synergistic optimization of carrier thermal leakage suppression and high hole injection efficiency in the cold state (i.e., at low temperature) by forming a band profile with a "steep front and gentle back" shape in the P-type confinement layer.

[0054] Optionally, in some embodiments of this application, the thickness of the P-type confinement layer ranges from 780 nm to 1050 nm, including the endpoints, so that the P-type confinement layer can achieve a sufficient barrier height while avoiding increased series resistance and crystal quality degradation due to excessive thickness. For example, the total thickness of the P-type confinement layer can be 785 nm, 910 nm, 1035 nm, etc., and this application does not limit this; in specific applications, an appropriate thickness value can be selected within this range according to the specific device requirements.

[0055] Optionally, in some embodiments of this application, the number of sub-P-type confinement layers included in the P-type confinement layer is 2 or 3, so that within the range of aluminum composition values ​​in each sub-P-type confinement layer, the aluminum composition of adjacent sub-P-type confinement layers can increase in a stepwise manner, thereby forming an effective valence band barrier between adjacent sub-P-type confinement layers. However, this application does not limit this, and it depends on the specific circumstances.

[0056] Specifically, when the P-type confinement layer includes two sub-P-type confinement layers, a two-stage stepped potential barrier can be formed in the P-type confinement layer to achieve step-by-step reflection and blocking of hot carriers; when the P-type confinement layer includes three sub-P-type confinement layers, a three-stage stepped potential barrier can be formed in the P-type confinement layer to achieve step-by-step reflection and blocking of hot carriers. The following description uses the example of a P-type confinement layer including three sub-P-type confinement layers to illustrate the red LED epitaxial structure provided in this application embodiment.

[0057] Based on any of the above embodiments, in some embodiments of this application, the at least two sub-P-type confinement layers include a first sub-P-type confinement layer, a second sub-P-type confinement layer, and a third sub-P-type confinement layer stacked sequentially along the direction away from the active layer; the bandgap difference between the first sub-P-type confinement layer and the active layer ranges from 1.52 eV to 1.75 eV, including the endpoint value; the bandgap difference between the second sub-P-type confinement layer and the active layer ranges from 1.75 eV to 1.98 eV, including the endpoint value; and the bandgap difference between the third sub-P-type confinement layer and the active layer ranges from 1.98 eV to 2.22 eV, including the endpoint value, so as to reduce the thermal leakage rate of carriers at 85°C to less than 30% while ensuring that the hole injection efficiency is greater than 90%, thereby suppressing the thermal emission mechanism from a physical level.

[0058] Optionally, in some embodiments of this application, the aluminum composition of the first sub-P-type confinement layer ranges from 0.65 to 0.75, including the endpoint values, so that the bandgap difference between the first sub-P-type confinement layer and the active layer ranges from 1.52 eV to 1.75 eV, including the endpoint values, thereby ensuring a hole injection efficiency greater than 90%; the aluminum composition of the second sub-P-type confinement layer ranges from 0.75 to 0.85, including the endpoint values, so that the bandgap difference between the second sub-P-type confinement layer and the active layer ranges from 1.52 eV to 1.75 eV, including the endpoint values, thereby ensuring a hole injection efficiency greater than 90%; The bandgap difference ranges from 1.75 eV to 1.98 eV, including the endpoints, thus providing core barrier support. The aluminum composition of the third sub-P-type confinement layer ranges from 0.85 to 0.95, including the endpoints, so that the bandgap difference between the third sub-P-type confinement layer and the active layer ranges from 1.98 eV to 2.22 eV, including the endpoints, thereby providing strong carrier reflection and reducing the heat leakage rate of carriers at 85°C to less than 30%, suppressing the thermal emission mechanism from a physical perspective. Therefore, in this embodiment, the aluminum composition of the three sub-P-type confinement layers increases progressively away from the active layer, and the difference in aluminum composition between adjacent sub-P-type confinement layers is in the range of 0.05 to 0.1, causing the valence band barrier in each sub-P-type confinement layer to gradually increase away from the active layer, thus forming a steep barrier in the P-type confinement layer, effectively suppressing reverse heat leakage and improving the carrier recombination efficiency of the red LED epitaxial structure in a high-temperature environment.

[0059] It should be noted that LEDs inevitably undergo a continuous process from room temperature startup to high temperature steady state during actual operation, and the physical behavior of charge carriers in these two states is completely different: in the cold state, the thermal kinetic energy of charge carriers is low, and if the potential barrier in the P-type confinement layer is too high, it will hinder injection and make it difficult for the LED to turn on; while in the hot state, the charge carriers gain significant thermal kinetic energy, and if the potential barrier in the P-type confinement layer is too low, it cannot block reverse leakage, leading to high-temperature failure. In the embodiments of this application, the first sub-P-type confinement layer is close to the active layer and uses a lower aluminum composition to form a lower potential barrier, which is conducive to hole injection into the active region in the cold state. The second and third sub-P-type confinement layers are far from the active layer and use a higher aluminum composition to form a higher potential barrier to block charge carrier leakage and reduce the charge carrier thermal leakage rate. Thus, through the combination of the first, second, and third sub-P-type confinement layers, a full-temperature adaptive function of "low-temperature opening and high-temperature blocking" is achieved.

[0060] For example, in one embodiment of this application, the aluminum composition of the first sub-P-type confinement layer is 0.7, the aluminum composition of the second sub-P-type confinement layer is 0.8, and the aluminum composition of the third sub-P-type confinement layer is 0.9. This raises the valence band barrier between the P-type confinement layer and the active region from 0.16 eV to 0.34 eV, constructing a progressively increasing barrier and forming a three-stage heat leakage interception mechanism of "throttling-confinement-blocking," enhancing the ability to block hot carriers. Specifically, in the cold state, the first sub-P-type confinement layer with low aluminum composition acts as a "throttling window," ensuring efficient hole injection into the active region while establishing a preliminary barrier, guaranteeing a hole injection efficiency >90%. In the hot state, the second sub-P-type confinement layer with medium aluminum composition acts as the "main confinement layer," providing the main barrier height and serving as the core layer for blocking hole leakage. The third sub-P-type confinement layer with high aluminum composition acts as a "heat-blocking layer," establishing the highest barrier and strongly blocking heat leakage of carriers into the P-type layer. It should be noted that in this embodiment, the high barrier progressive reflection of hot carriers constructed by the second sub-P-type confinement layer of the medium aluminum component and the third sub-P-type confinement layer of the high aluminum component can achieve the escape of only <15% of hot carriers and reduce the hole heat leakage rate in the LED at 85°C from the traditional >40% to <7%.

[0061] Based on any of the above embodiments, in some embodiments of this application, the thickness of each sub-P-type confinement layer in the at least two sub-P-type confinement layers increases in the direction away from the active layer. That is, in the P-type confinement layers, the sub-P-type confinement layers closer to the active layer are thinner, and the sub-P-type confinement layers farther from the active layer are thicker. The thickness is set differentially according to the functional positioning of each sub-P-type confinement layer, so that the sub-P-type confinement layers with low bandgap widths have smaller thicknesses to ensure the hole injection efficiency in the active layer in the cold state; the sub-P-type confinement layers with medium bandgap widths have medium thicknesses and serve as the core support region of the barrier to balance crystal quality and confinement effectiveness; and the sub-P-type confinement layers with high bandgap widths have the largest thicknesses to increase the high barrier formed by the high bandgap sub-P-type confinement layers to block hot carriers, extend the penetration path of hot carriers, and intercept hot-emitted carriers with the thickest physical barrier, thereby enhancing the heat leakage suppression capability in the hot state.

[0062] Thus, in this embodiment, the P-type confinement layer constructs a multi-level, progressive valence band barrier system by simultaneously increasing the band gap width and thickness. Each level of barrier not only reflects hot carriers with a height jump, but also extends the penetration path of hot carriers with increasing thickness. This causes the carriers to experience kinetic energy attenuation and directional deflection when passing through each layer, and finally they are completely blocked at the third sub-P-type confinement layer, which significantly improves the carrier confinement efficiency.

[0063] Optionally, in some embodiments of this application, the thickness of the first sub-P-type confinement layer ranges from 80 to 120 nm, including the endpoint value; the thickness of the second sub-P-type confinement layer ranges from 250 to 350 nm, including the endpoint value; and the thickness of the third sub-P-type confinement layer ranges from 450 to 550 nm, including the endpoint value; however, this application does not limit this, and it depends on the specific circumstances.

[0064] Based on any of the above embodiments, in some embodiments of this application, the energy difference between the Fermi level and the valence band top of each of the at least two sub-P-type confinement layers increases along the direction away from the active layer, so that the sub-P-type confinement layer near the active layer has a higher hole injection efficiency and the sub-P-type confinement layer away from the active layer has a lower free carrier absorption loss.

[0065] Optionally, in some embodiments of this application, the energy difference between the Fermi level and the valence band top of the first sub-P-type confinement layer ranges from 0.031 eV to 0.060 eV, including the endpoint; the energy difference between the Fermi level and the valence band top of the second sub-P-type confinement layer ranges from 0.042 eV to 0.078 eV, including the endpoint; and the energy difference between the Fermi level and the valence band top of the third sub-P-type confinement layer ranges from 0.060 eV to 0.120 eV, including the endpoint. However, this application does not limit this range and the specific range depends on the circumstances.

[0066] The inventors discovered that each sub-P-type confinement layer uses the same doping concentration, such as 1×10⁻⁶. 18 ~2×10 18 If the concentration is 1 cm⁻³, it cannot take into account the different requirements of different Al composition regions for doping activation rate and carrier transport characteristics. If a continuous gradual doping mode is adopted, and the hole transport capability is enhanced by gradually increasing the doping concentration along the growth direction, the following problems will occur: low doping concentration in low aluminum composition regions will lead to insufficient doping concentration in the region, increasing the series resistance and hindering hole injection; while high doping concentration in high aluminum composition will produce severe impurity scattering, degrade the barrier quality, significantly enhance the Zener tunneling probability, and form a tunneling leakage channel from the P-type region to the active region, which will weaken the carrier blocking function of the P-type confinement layer.

[0067] Therefore, in some embodiments of this application, the doping concentration of each sub-P-type confinement layer in the at least two sub-P-type confinement layers decreases along the direction away from the active layer. That is, in the P-type confinement layer, the low-aluminum molecular P-type confinement layer near the active layer adopts a higher doping concentration to compensate for the high mobility brought by the low aluminum composition, which is conducive to reducing the series resistance of the P-type confinement layer and ensuring efficient hole injection into the active region; the high-aluminum molecular P-type confinement layer away from the active layer adopts a lower doping concentration to compensate for the decrease in doping activation rate caused by the increase in aluminum composition, reduce the damage of impurity scattering to the high barrier quality, and enhance the carrier blocking capability of the P-type confinement layer.

[0068] It should be noted that, in the embodiments of this application, the aluminum composition of each sub-P-type confinement layer in the at least two sub-P-type confinement layers increases along the direction away from the active layer, the doping concentration decreases along the direction away from the active layer, and the difference in aluminum composition between adjacent sub-P-type confinement layers is in the range of 0.05 to 0.1, including the endpoint value, which can improve the carrier thermal leakage suppression rate of the P-type confinement layer to more than 70%.

[0069] Optionally, in some embodiments of this application, the P-type doping concentration of the first sub-P-type confinement layer is 1×10⁻⁶. 18 ~3×10 18atoms / cm³, including endpoint values; the P-type doping concentration of the second sub-P-type confinement layer is 5 × 10⁻⁶. 17 ~2×10 18 atoms / cm³, including endpoint values; the P-type doping concentration of the third sub-P-type confinement layer is 1×10⁻⁶. 17 ~1×10 18 atoms / cm³, including endpoint values. However, this application does not impose a limitation on this; it depends on the specific circumstances.

[0070] Based on any of the above embodiments, in some embodiments of this application, the aluminum composition of each sub-P-type confinement layer in the at least two sub-P-type confinement layers increases in the direction away from the active layer, the thickness of each sub-P-type confinement layer in the at least two sub-P-type confinement layers increases in the direction away from the active layer, and the doping concentration of each sub-P-type confinement layer in the at least two sub-P-type confinement layers decreases in the direction away from the active layer. A three-level ladder structure of "low Al thin layer with high doping - medium Al medium layer with medium doping - high Al thick layer with low doping" can be constructed in the direction away from the active layer, achieving multi-dimensional synergistic optimization in balancing barrier strength and buffering capacity, suppressing leakage current, and improving reliability. For example, the P-type confinement layer includes a first sub-P-type confinement layer, a second sub-P-type confinement layer, and a third sub-P-type confinement layer. The first sub-P-type confinement layer uses a lower aluminum composition, a thinner thickness, and the highest doping concentration. The lower aluminum composition helps reduce stress caused by lattice mismatch, the thinner thickness facilitates the rapid passage of holes, and the higher doping concentration compensates for the conductivity of the low aluminum composition region, ensuring efficient hole injection into the active region and establishing an initial barrier. The second sub-P-type confinement layer uses a medium aluminum composition, a medium thickness, and a medium doping concentration to provide the main valence band barrier height by moderately increasing the aluminum content and thickness, and uses a medium doping concentration to balance the barrier blocking ability with the introduction of crystal defects. The third sub-P-type confinement layer uses the highest aluminum composition and the largest thickness to construct the strongest barrier, thereby improving the ability to block carrier thermal leakage, while using a low doping concentration to reduce impurity-induced lattice distortion.

[0071] In the red LED epitaxial structure provided in this application embodiment, the P-type confinement layer is a discrete stepped composite structure composed of at least two P-type AlGaInP sublayers with different aluminum compositions and doping concentrations. Through the synergistic optimization of synchronously increasing Al composition and thickness and decreasing doping concentration, the P-type confinement layer can achieve temperature adaptive control of "cold-state efficient injection" and "hot-state stepped sealing", thereby improving the cold-to-hot ratio of the red LED epitaxial structure from 0.63 to 0.74, an improvement of up to 17%.

[0072] Moreover, the progressively increasing aluminum composition in the P-type confinement layer can prevent strain accumulation caused by excessive abrupt changes from penetrating into the multi-quantum-well region, thereby improving the long-term reliability of the device while reducing the hole thermal leakage rate to below 7% at 85°C.

[0073] Based on any of the above embodiments, in some embodiments of this application, the P-type confinement layer further includes at least one intrinsic spacer layer. It should be noted that, strictly defined in semiconductor physics, an intrinsic layer is a layer that is "unintentionally doped," not a layer with "absolutely zero doping concentration." Optionally, in embodiments of this application, the doping concentration of the intrinsic spacer layer is no greater than 1 × 10⁻⁶. 16 The limit is atoms / cm³, but this application does not impose any limit on this; it depends on the specific circumstances.

[0074] In this embodiment, the intrinsic spacer layer can not only serve as an electrical isolation layer between adjacent doped layers, blocking the direct tunneling channel formed between adjacent doped layers due to band tilt, thus reducing the Zener tunneling probability by about an order of magnitude, but also serve as a lattice transition layer, relieving the lattice mismatch stress between low-aluminum composition layers and high-aluminum composition layers, suppressing the generation of interface dislocations and defects, and ensuring the crystal quality of the high barrier region.

[0075] It should be noted that, in the embodiments of this application, the P-type confinement layer includes multiple sub-P-type confinement layers in which the aluminum composition and thickness increase synchronously and the doping concentration decreases synchronously along the direction away from the active layer. Combined with the intrinsic spacer layer disposed between adjacent sub-layers to block the Zener tunneling channel, the leakage current suppression rate of the LED can reach 75%~85%, the external quantum efficiency can reach 28%, and the ESD (HBM) resistance can be improved from 1kV to 2kV without increasing the series resistance, which significantly improves the high-temperature performance and reliability of red LEDs.

[0076] Optionally, in some embodiments of this application, the intrinsic spacer layer is located between two adjacent sub-P-type confinement layers, serving as an electrical isolation layer to block direct tunneling channels formed between adjacent sub-P-type confinement layers due to band tilt, thereby reducing the Zener tunneling probability by an order of magnitude and ensuring the integrity of the barrier structure. Furthermore, this intrinsic spacer layer, located between two adjacent sub-P-type confinement layers, can also serve as a band buffer layer, forming a smooth band transition between abrupt heterojunctions of adjacent sub-P-type confinement layers, avoiding interface state recombination that may be triggered by overly steep band abrupt changes.

[0077] In some other embodiments of this application, the intrinsic spacer layer is located between the at least two sub-P-type confinement layers and the active layer, serving as an electrical isolation layer to block doped ions in the P-type confinement layer from entering the active layer.

[0078] Optionally, in some embodiments of this application, the P-type confinement layer includes only one intrinsic spacer layer, which is located between the at least two sub-P-type confinement layers and the active layer, so that the intrinsic spacer layer can block doped ions in each sub-P-type confinement layer from entering the active layer. However, this application does not limit this, and it depends on the specific circumstances.

[0079] In other embodiments of this application, the P-type confinement layer includes at least two intrinsic spacer layers, with different intrinsic spacer layers located at different positions within the P-type confinement layer in a direction away from the active layer. Exemplarily, the P-type confinement layer includes a first sub-P-type confinement layer, a second sub-P-type confinement layer, and a third sub-P-type confinement layer. In this embodiment, the P-type confinement layer includes at least two of the first, second, and third intrinsic spacer layers, wherein the first intrinsic spacer layer is located between the first sub-P-type confinement layer and the active layer, the second intrinsic spacer layer is located between the first and second sub-P-type confinement layers, and the third intrinsic spacer layer is located between the second and third sub-P-type confinement layers.

[0080] Based on any of the above embodiments, in some embodiments of this application, the film layer located on the side of the intrinsic spacer layer facing the active layer and adjacent to the intrinsic spacer layer is the first film layer; the film layer located on the side of the intrinsic spacer layer away from the active layer and adjacent to the intrinsic spacer layer is the second film layer; the conduction band barrier height of the intrinsic spacer layer is located between the conduction band barrier height of the first film layer and the conduction band barrier height of the second film layer, so as to avoid abrupt changes in the conduction band barrier and suppress the increase in interface state density. However, this application does not limit this. In other embodiments of this application, the conduction band barrier height of the intrinsic spacer layer may also be the same as the conduction band barrier height of the first film layer or the same as the conduction band barrier height of the second film layer, depending on the specific situation.

[0081] Optionally, in some embodiments of this application, the aluminum component of the intrinsic spacer layer is located between the aluminum components of the first film layer and the aluminum components of the second film layer. For example, if the intrinsic spacer layer is a first intrinsic spacer layer, then the first film layer is an active layer and the second film layer is a first sub-P-type confinement layer; if the intrinsic spacer layer is a second intrinsic spacer layer, then the first film layer is a first sub-P-type confinement layer and the second film layer is a second sub-P-type confinement layer; if the intrinsic spacer layer is a third intrinsic spacer layer, then the first film layer is a second sub-P-type confinement layer and the second film layer is a third sub-P-type confinement layer.

[0082] It should be noted that when there are other films between the active layer and the first sub-P-type confinement layer, the first film is the film located between the active layer and the first sub-P-type confinement layer and adjacent to the first sub-P-type confinement layer.

[0083] In some other embodiments of this application, the aluminum composition of the intrinsic spacer layer may be the same as that of the first film layer to reduce process complexity. However, this application does not limit this. In other embodiments of this application, the aluminum composition of the intrinsic spacer layer may also be the same as that of the second film layer, depending on the specific circumstances.

[0084] Based on any of the above embodiments, in some embodiments of this application, the thickness of the intrinsic spacer layer ranges from 5 nm to 15 nm, including the endpoints. For example, the thickness of the intrinsic AlGaInP spacer layer can be 5 nm, 8 nm, 10 nm, 12 nm, or 15 nm, so that the intrinsic spacer layer is sufficiently formed to create an effective electrical isolation layer, blocking Zener tunneling channels between adjacent doped layers, while avoiding excessive thickness of the intrinsic spacer layer, which would increase the total thickness of the P-type confinement layer and the series resistance. However, this application does not limit this, and the specific thickness depends on the circumstances.

[0085] It should be noted that in the embodiments of this application, when the P-type confinement layer includes two intrinsic spacer layers, the thicknesses of the two spacer layers may be the same or different. This application does not limit this, and it depends on the specific circumstances.

[0086] The red LED epitaxial structure provided in this application embodiment is described below with reference to specific embodiments.

[0087] Example 1

[0088] In this embodiment, the red LED epitaxial structure includes a GaAs substrate and, sequentially, an n-GaAs buffer layer, an N-type window layer, an N-type confinement layer, an N-type waveguide layer, an active layer, a P-type waveguide layer, a P-type confinement layer, a P-type window layer, and a P-type contact layer fabricated on the surface of the GaAs substrate. Continuing as... Figure 1 As shown, the P-type confinement layer 402 includes a first sub-P-type confinement layer 4021, a second sub-P-type confinement layer 4022, and a third sub-P-type confinement layer 4023 arranged along the direction away from the active layer 300. The first sub-P-type confinement layer 4021 has an Al composition of 0.70 and a Mg doping concentration of 2 × 10⁻⁶. 18 atoms / cm 3 The thickness of the first sub-P-type confinement layer 4021 is 100 nm; the Al composition of the second sub-P-type confinement layer 4022 is 0.80, and the Mg doping concentration is 1 × 10⁻⁶. 18 The second P-type confinement layer 4022 has a thickness of 300 nm; the third P-type confinement layer 4023 has an Al composition of 0.90, a thickness of 500 nm, and a Mg doping concentration of 5 × 10⁻⁶. 17atoms / cm³. The Al composition in the P-type waveguide layer 401 is 0.45, and the thickness is 200nm, undoped. It should be noted that in this embodiment, the total thickness of the P-type confinement layer 402 is approximately 900nm (within the design range of 780nm~1050nm), plus the 200nm thickness of the P-type waveguide layer 401, and the negligible thicknesses of the P-type window layer 403 and the P-type contact layer 404, totaling approximately 1000nm.

[0089] In the red LED epitaxial structure provided in this application embodiment, the Al composition of the P-type confinement layer abruptly changes from 0.70 in the first sub-P-type confinement layer to 0.80 in the second sub-P-type confinement layer and then to 0.90 in the third sub-P-type confinement layer, forming a clear three-level gradient. Correspondingly, its doping concentration changes from 2E18 in the first sub-P-type confinement layer to 1E18 in the second sub-P-type confinement layer and then to 5E17 in the third sub-P-type confinement layer. This structure employs a dual gradient setting of increasing Al composition and decreasing doping concentration, which, according to calculations, can achieve an expected electron leakage suppression rate of approximately 70%~80%, significantly improve the Droop effect, and increase the EQE peak by approximately 10-15% compared to the traditional P-type confinement layer. It should be noted that the Droop effect, also known as the efficiency droop effect, refers to the phenomenon that the external quantum efficiency (EQE) of an LED decreases significantly with increasing current density as the operating current density increases.

[0090] Example 2:

[0091] In this embodiment, the red LED epitaxial structure includes a GaAs substrate and, sequentially fabricated on the surface of the GaAs substrate, an n-GaAs buffer layer, an N-type window layer, an N-type confinement layer, an N-type waveguide layer, an active layer, a P-type waveguide layer, a P-type confinement layer, a P-type window layer, and a P-type contact layer. Figure 2 As shown, the P-type confinement layer 402 includes a first sub-P-type confinement layer 4021, a second sub-P-type confinement layer 4022, a third intrinsic spacer layer 4024, and a third sub-P-type confinement layer 4023 arranged along the direction away from the active layer 300. The first sub-P-type confinement layer has an Al composition of 0.70 and a Mg doping concentration of 2 × 10⁻⁶. 18 The first sub-P-type confinement layer 4021 has a thickness of 100 nm; the second sub-P-type confinement layer 4022 has an Al composition of 0.80 and a Mg doping concentration of 1 × 10⁻⁶. 18 The second sub-P-type confinement layer 4022 has a thickness of 300 nm; the third intrinsic spacer layer 4024 has an Al composition of 0.80, a thickness of 10 nm, and intrinsic doping ≤ 1 × 10⁻⁶. 16atoms / cm³; the Al composition in the third-generation P-type confinement layer 4023 is 0.90, the thickness is 500 nm, and the Mg doping concentration is 5 × 10⁻⁶. 17 atoms / cm³. The Al composition in the P-type waveguide layer 401 is 0.45, and the thickness is 200nm, with no doping. It should be noted that in this embodiment, the total thickness of the P-type confinement layer 402 is approximately 910nm (within the design range of 780nm~1050nm), plus the 200nm thickness of the P-type waveguide layer 401, and the negligible thicknesses of the P-type window layer 403 and the P-type contact layer 404, totaling approximately 1110nm.

[0092] The difference from Embodiment 1 lies in the different configuration of the P-type confinement layer. In Embodiment 1, no intrinsic spacer layer is provided in the P-type confinement layer. In this embodiment, an intrinsic spacer layer is introduced between the second sub-P-type confinement layer and the third sub-P-type confinement layer.

[0093] In the red LED epitaxial structure provided in this application embodiment, the Al composition of the P-type confinement layer abruptly changes from 0.70 in the first sub-P-type confinement layer to 0.80 in the second sub-P-type confinement layer and then to 0.90 in the third sub-P-type confinement layer, forming a clear three-level gradient. Correspondingly, its doping concentration changes from 2E18 in the first sub-P-type confinement layer to 1E18 in the second sub-P-type confinement layer and then to 5E17 in the third sub-P-type confinement layer. The intrinsic spacer layer is disposed between the second and third sub-P-type confinement layers. This P-type confinement layer, employing a dual gradient (increasing Al composition + decreasing doping concentration) in synergy with the intrinsic spacer layer, is calculated to achieve an electron leakage suppression rate expected to reach over 85%, an improvement of 5%-15% compared to Embodiment 1. The drop effect is further improved, with an improvement of 5%-10% compared to Embodiment 1.

[0094] Example 3

[0095] In this embodiment, the red LED epitaxial structure includes a GaAs substrate and, sequentially fabricated on the surface of the GaAs substrate, an n-GaAs buffer layer, an N-type window layer, an N-type confinement layer, an N-type waveguide layer, an active layer, a P-type waveguide layer, a P-type confinement layer, a P-type window layer, and a P-type contact layer. Figure 3 As shown, the P-type confinement layer 402 includes a first sub-P-type confinement layer 4021, a second intrinsic spacer layer 4025, a second sub-P-type confinement layer 4022, a third intrinsic spacer layer 4024, and a third sub-P-type confinement layer 4023 arranged along the direction away from the active layer 300. The first sub-P-type confinement layer 4021 has an Al composition of 0.70 and a Mg doping concentration of 2 × 10⁻⁶. 18 atoms / cm 3The first sub-P-type confinement layer 4021 has a thickness of 100 nm; the second intrinsic spacer layer 4025 has an Al composition of 0.7, a thickness of 8 nm, and intrinsic doping ≤ 1 × 10⁻⁶. 16 atoms / cm³; the Al composition in the second P-type confinement layer 4022 is 0.80, and the Mg doping concentration is 1×10⁻⁶. 18 The second sub-P-type confinement layer 4022 has a thickness of 300 nm; the third intrinsic spacer layer 4024 has an Al composition of 0.80, a thickness of 8 nm, and intrinsic doping ≤ 1 × 10⁻⁶. 16 atoms / cm³; the Al composition in the third-generation P-type confinement layer 4023 is 0.90, the thickness is 500 nm, and the Mg doping concentration is 5 × 10⁻⁶. 17 atoms / cm³. The Al composition in the P-type waveguide layer 401 is 0.45, and the thickness is 200nm, with no doping. It should be noted that in this embodiment, the total thickness of the P-type confinement layer 402 is approximately 916nm (within the design range of 780nm~1050nm), plus the 200nm thickness of the P-type waveguide layer 401, and the negligible thicknesses of the P-type window layer 403 and the P-type contact layer 404, totaling approximately 1116nm.

[0096] The difference from Embodiment 2 lies in the different configuration of the P-type confinement layer. In Embodiment 2, an intrinsic spacer layer is introduced only between the second sub-P-type confinement layer and the third sub-P-type confinement layer. In this embodiment, an intrinsic spacer layer is introduced not only between the second sub-P-type confinement layer and the third sub-P-type confinement layer, but also between the first sub-P-type confinement layer and the second sub-P-type confinement layer.

[0097] In the red LED epitaxial structure provided in this application embodiment, the P-type confinement layer ensures that the Al composition increases (0.70 < 0.80 < 0.90) and the doping concentration decreases continuously (2 × 10⁻⁶) along the direction away from the active layer. 18 >1×10 18 >5×10 17 By introducing a dual intrinsic spacer layer based on the existing structure, the interface state density between the second sub-P-type confinement layer and the adjacent sub-P-type confinement layer can be reduced to 10. 9 cm -2The following measures are taken to alleviate the lattice mismatch stress between the second and first sub-P-type confinement layers, as well as between the second and third sub-P-type confinement layers, thereby improving the crystal quality of the epitaxial structure. Simultaneously, the dual intrinsic spacer layers reduce the recombination loss of holes at the interfaces of the second and first sub-P-type confinement layers, and between the second and third sub-P-type confinement layers, respectively, thus improving the overall implantation efficiency. Compared to the scheme in Example 1, the scheme in this application can increase the electron leakage suppression rate from 85% to 88-90% while maintaining a constant operating voltage, an improvement of 8%-20% compared to Example 1. The external quantum efficiency (EQE) is further improved by 3-5% compared to Example 2, reaching 28%.

[0098] like Figure 4 and Figure 5 As shown, Figure 4 This diagram illustrates the band structure when the P-type confinement layer is designed with a uniform or continuously gradually varying aluminum composition. Figure 5 This illustration shows an energy band diagram in an embodiment of this application where the P-type confinement layer typically employs a discrete, stepwise increase in aluminum composition, a synchronous increase in thickness, and a synchronous decrease in doping concentration for each sub-P-type confinement layer, and an intrinsic spacer layer is provided between adjacent sub-P-type confinement layers. Figure 5 In the structure shown, the aluminum composition of the first sub-P-type confinement layer in the P-type confinement layer is 0.7, the aluminum composition of the second sub-P-type confinement layer is 0.8, and the aluminum composition of the third sub-P-type confinement layer is 0.9. An intrinsic spacer layer is provided between adjacent P-type confinement layers to form an abrupt heterojunction.

[0099] from Figure 4 and Figure 5 It can be seen that when the P-type confinement layer is designed with uniform or continuously gradually changing aluminum composition, the conduction band bottom Ec and valence band top Ev have a smooth transition, and the valence band barrier height ΔEv is usually only 0.16 eV, which is relatively low. However, in the embodiments of this application, the P-type confinement layer typically adopts a discrete stepwise increase in aluminum composition, a synchronous increase in thickness, and a synchronous decrease in doping concentration for each sub-P-type confinement layer, and an intrinsic spacer layer is set between adjacent sub-P-type confinement layers, which can cause abrupt changes in the energy band, thereby forming a multi-level barrier at the valence band and raising the valence band barrier height ΔEv to above 0.34 eV, which is significantly higher than the previous design. Figure 4 The improvement reaches 113%, which can effectively reduce carrier heat leakage and improve the luminous efficiency, anti-static ability and high-temperature operation reliability of LEDs.

[0100] Accordingly, this application also provides an LED chip, which includes the red LED epitaxial structure described in any of the above embodiments, that is, the LED chip is fabricated from the red LED epitaxial structure in any of the above embodiments through a chip manufacturing process.

[0101] Optionally, in some embodiments of this application, after the growth of the red LED epitaxial structure is completed, a mesa structure is formed by photolithography and etching processes to expose the N-type layer; an N-type electrode is fabricated on the surface of the exposed N-type layer, and a P-type electrode is fabricated on the surface of the P-type contact layer; the epitaxial wafer is divided into individual LED chips by processes such as dicing and cleaving.

[0102] Since the LED chip adopts the red LED epitaxial structure in any of the aforementioned embodiments, its P-type confinement layer has structural features such as discrete step-like increasing bandgap width, increasing thickness, increasing energy difference between the Fermi level and the valence band top, and optional intrinsic spacer layer. Therefore, the LED chip has a significantly reduced carrier thermal leakage rate under high-temperature operating conditions, and its external quantum efficiency and ESD resistance at high temperatures of 85°C and above are superior to LED chips with a single Al composition or a continuously gradient aluminum composition in the P-type confinement layer.

[0103] In summary, the LED chip and red LED epitaxial structure provided in this application embodiment adopt a triple collaborative design of "discrete stepped bandgap increasing + energy difference increasing between Fermi level and valence band top + intrinsic spacer layer". Among them, the discrete stepped bandgap increasing is used to construct a three-level high-steepness valence band barrier, so as to utilize the abrupt heterojunction at the interface of each sub-P-type confinement layer to generate stepwise reflection of hot-emission carriers, thereby significantly reducing the hot-emission leakage rate; the energy difference increasing between Fermi level and valence band top is used to maintain low conductivity in the high bandgap region, weakening the electric field strength in this region and reducing the driving force of Zener tunneling from the source; the intrinsic spacer layer, as a physical blocking layer, directly cuts off the tunneling channel between adjacent sub-P-type confinement layers. The triple design, with its mutual coupling, enables the P-type confinement layer to comprehensively suppress both thermal emission and tunneling leakage mechanisms of charge carriers. This can reduce the hole thermal leakage rate of LEDs to below 7% at 85°C, achieve an external quantum efficiency of 28%, and improve ESD resistance to 2kV.

[0104] Accordingly, this application also provides a method for fabricating a red LED epitaxial structure, used to fabricate the red LED epitaxial structure provided in any of the above embodiments, specifically, as follows: Figure 6 As shown, the manufacturing method includes:

[0105] S1: Provides a substrate;

[0106] S2: An N-type layer, an active layer, and a P-type layer are sequentially fabricated on the first side of the substrate. The P-type layer includes a P-type confinement layer, which includes at least two sub-P-type confinement layers. The bandgap difference between each sub-P-type confinement layer and the active layer 300 increases in the direction away from the active layer 300, and the difference between the bandgap widths of adjacent sub-P-type confinement layers is in the range of 0.115eV to 0.228eV, including the endpoint value.

[0107] Optionally, in some embodiments of this application, the aluminum composition of each of the at least two sub-P-type confinement layers increases in the direction away from the active layer, and the difference in aluminum composition between adjacent sub-P-type confinement layers is in the range of 0.05 to 0.1, including the endpoint value, so that the difference in bandgap width between each of the at least two sub-P-type confinement layers and the active layer 300 increases in the direction away from the active layer 300, and the difference in bandgap width between adjacent sub-P-type confinement layers is in the range of 0.115 eV to 0.228 eV, including the endpoint value.

[0108] Optionally, in some embodiments of this application, the fabrication method uses a GaAs substrate as the substrate, and employs metal-organic chemical vapor deposition (MOCVD) to sequentially fabricate an N-type layer, an active layer, and a P-type layer on the GaAs substrate. However, this application does not limit this, and the specific method depends on the circumstances.

[0109] Optionally, in some embodiments of this application, the N-type layer may include an n-GaAs buffer layer, an N-type window layer, an N-type confinement layer, and an N-type waveguide layer sequentially stacked on the substrate; the active layer may be a multiple quantum well (MQW) active region; the P-type layer includes a P-type waveguide layer, a P-type confinement layer, a P-type window layer, and a P-type contact layer stacked along a direction away from the active layer. However, this application does not limit this, and the specific implementation depends on the circumstances.

[0110] Based on the above embodiments, in some embodiments of this application, the P-type confinement layer is an AlGaInP layer, and the growth process of the P-type confinement layer includes:

[0111] First, TMAl, TMGa, TMIn, PH3, and Cp2Mg are introduced into the process chamber. Within a temperature range of 680℃ to 720℃, a first sub-P-type confinement layer with a thickness ranging from 80nm to 120nm is grown on the surface of the P-type waveguide layer at a growth rate of 0.3μm / h to 1μm / h. Specifically, during the growth process, the TMAl flow rate needs to be controlled to stabilize the Al composition within the range of 0.65 to 0.75, and the Cp2Mg flow rate needs to be controlled to achieve a P-type Mg doping concentration of 1×10⁻⁶. 18 ~3×10 18 Within the range of atoms / cm³;

[0112] Then, stop the Cp2Mg flow, keep the flow rates of TMAl, TMGa, TMIn, and PH3 constant, and maintain for 1 to 3 minutes to grow an intrinsic spacer layer with a thickness in the range of 5 to 15 nm on the surface of the first sub-P-type confinement layer.

[0113] Next, the TMAl flow rate was adjusted until the Al composition stabilized within the range of 0.75~0.85, while keeping the flow rates of TMGa, TMIn, and PH3 constant. Cp2Mg was then reintroduced with a reduced flow rate to achieve a p-type Mg doping concentration of 5 × 10⁻⁶. 17 ~2×10 18 Within the range of atoms / cm³, at a temperature range of 680℃ to 720℃, a second sub-P-type confinement layer with a thickness in the range of 250nm to 350nm is grown on the surface of the intrinsic spacer layer at a growth rate of 0.3μm / h to 1μm / h.

[0114] Finally, the TMAl flow rate was adjusted until the Al composition stabilized in the range of 0.85–0.95, while keeping the flow rates of TMGa, TMIn, and PH3 constant. The Cp2Mg flow rate was then reduced to achieve a p-type Mg doping concentration of 1 × 10⁻⁶. 17 ~1×10 18 Within the range of atoms / cm³, at a temperature range of 680℃ to 720℃, a third sub-P-type confinement layer with a thickness in the range of 450nm to 550nm is grown on the surface of the second sub-P-type confinement layer at a growth rate of 0.3μm / h to 1μm / h, thus completing the fabrication of the P-type confinement layer.

[0115] Optionally, in this embodiment, the total thickness of the P-type confinement layer needs to be controlled within the range of 780nm~1050nm to balance the electron blocking capability and hole injection efficiency of the P-type confinement layer.

[0116] Using the above method, the P-type confinement layer can have a discrete, stepped aluminum composition distribution, and abrupt heterojunctions and progressively increasing valence band barriers can be formed between each sub-P-type confinement layer.

[0117] It should be noted that the method for fabricating the red LED epitaxial structure provided in this application embodiment allows for flexible design of the band structure of the P-type confinement layer according to specific device requirements by adjusting the aluminum composition, thickness, and doping concentration of each sub-P-type confinement layer, thereby effectively suppressing carrier thermal leakage. Furthermore, the fabrication method for the red LED epitaxial structure provided in this application embodiment is process-controllable, compatible with existing MOCVD processes, and requires no additional equipment or special source materials.

[0118] The various embodiments in this specification are described in a progressive, parallel, or combined manner. Each embodiment focuses on its differences from other embodiments, and similar or identical parts between embodiments can be referred to interchangeably. Regarding the methods disclosed in the embodiments, since they correspond to the apparatus disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the apparatus section description.

[0119] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms are interchangeable where appropriate; this is merely a way of distinguishing objects with the same attributes in the embodiments of this application. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, so that a process, method, system, product, or apparatus that comprises a series of elements is not necessarily limited to those elements, but may include other elements not explicitly listed or inherent to those processes, methods, products, or apparatuses.

Claims

1. A red LED epitaxial structure, characterized in that, include: The substrate, N-type layer, active layer, and P-type layer are stacked together. The P-type layer includes a P-type confinement layer, which is an AlGaInP layer. The P-type confinement layer includes at least two sub-P-type confinement layers. The bandgap difference between each sub-P-type confinement layer and the active layer increases in the direction away from the active layer, and the difference between the bandgap widths of adjacent sub-P-type confinement layers is in the range of 0.115 eV to 0.228 eV, including the endpoint values.

2. The red LED epitaxial structure according to claim 1, characterized in that, The thickness of the P-type confinement layer ranges from 780 nm to 1050 nm, including the endpoint values. The difference in bandgap width between the sub-P-type confinement layer and the active layer ranges from 1.28 eV to 2.22 eV, including the endpoint values; The number of sub-P-type confinement layers included in the P-type confinement layer is 2 or 3.

3. The red LED epitaxial structure according to claim 1, characterized in that, The thickness of each of the at least two sub-P-type confinement layers increases in the direction away from the active layer; And / or, The energy difference between the Fermi level and the valence band top of each of the at least two sub-P-type confinement layers increases in the direction away from the active layer.

4. The red LED epitaxial structure according to claim 1, characterized in that, The at least two sub-P-type confinement layers include a first sub-P-type confinement layer, a second sub-P-type confinement layer, and a third sub-P-type confinement layer stacked sequentially along the direction away from the active layer; the bandgap difference between the first sub-P-type confinement layer and the active layer ranges from 1.52 eV to 1.75 eV, including the endpoint values; the bandgap difference between the second sub-P-type confinement layer and the active layer ranges from 1.75 eV to 1.98 eV, including the endpoint values; the bandgap difference between the third sub-P-type confinement layer and the active layer ranges from 1.98 eV to 2.22 eV, including the endpoint values. And / or, The energy difference between the Fermi level and the valence band top of the first sub-P-type confinement layer ranges from 0.031 eV to 0.060 eV, including the endpoints; the energy difference between the Fermi level and the valence band top of the second sub-P-type confinement layer ranges from 0.042 eV to 0.078 eV, including the endpoints; and the energy difference between the Fermi level and the valence band top of the third sub-P-type confinement layer ranges from 0.060 eV to 0.120 eV, including the endpoints.

5. The red LED epitaxial structure according to claim 1, characterized in that, The at least two sub-P-type confinement layers include a first sub-P-type confinement layer, a second sub-P-type confinement layer, and a third sub-P-type confinement layer stacked sequentially along the direction away from the active layer; the thickness of the first sub-P-type confinement layer ranges from 80 nm to 120 nm, including the endpoint values; the thickness of the second sub-P-type confinement layer ranges from 250 nm to 350 nm, including the endpoint values; and the thickness of the third sub-P-type confinement layer ranges from 450 nm to 550 nm, including the endpoint values.

6. The red LED epitaxial structure according to any one of claims 1-5, characterized in that, The P-type confinement layer further includes: at least one intrinsic spacer layer, wherein the intrinsic spacer layer is located between two adjacent sub-P-type confinement layers or between the at least two sub-P-type confinement layers and the active layer.

7. The red LED epitaxial structure according to claim 6, characterized in that, When the P-type confinement layer includes at least two intrinsic spacer layers, the different intrinsic spacer layers are located at different positions in the P-type confinement layer in the direction away from the active layer.

8. The red LED epitaxial structure according to claim 6, characterized in that, The film layer located on the side of the intrinsic spacer layer facing the active layer and adjacent to the intrinsic spacer layer is the first film layer; the film layer located on the side of the intrinsic spacer layer away from the active layer and adjacent to the intrinsic spacer layer is the second film layer. The conduction barrier height of the intrinsic spacer layer is located between the conduction barrier height of the first film layer and the conduction barrier height of the second film layer, or is the same as the conduction barrier height of the first film layer, or is the same as the conduction barrier height of the second film layer.

9. The red LED epitaxial structure according to claim 6, characterized in that, The thickness of the intrinsic spacer layer ranges from 5 nm to 15 nm, including the endpoint values.

10. An LED chip, characterized in that, Includes the red LED epitaxial structure as described in any one of claims 1-9.

11. A method for fabricating a red LED epitaxial structure, characterized in that, The method for fabricating the red LED epitaxial structure according to any one of claims 1-9 includes: Provide substrate; An N-type layer, an active layer, and a P-type layer are sequentially fabricated on the first side of the substrate. The P-type layer includes a P-type confinement layer, which is an AlGaInP layer. The P-type confinement layer includes at least two sub-P-type confinement layers. The bandgap difference between each sub-P-type confinement layer and the active layer increases in the direction away from the active layer, and the difference between the bandgap widths of adjacent sub-P-type confinement layers is in the range of 0.115 eV to 0.228 eV, including the endpoint values.

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