LED epitaxial structure, preparation method thereof and light emitting diode

Abstract

The application provides an LED epitaxial structure and a preparation method thereof and a light emitting diode, and belongs to the field of semiconductors. The LED epitaxial structure has an active layer comprising a first barrier layer, a second barrier layer, a third barrier layer and a potential well layer; the material of the active layer comprises an aluminum component; the aluminum component in the first barrier layer and the second barrier layer is greater than the aluminum component in the potential well layer; and the potential well layer and one of the first barrier layer, the second barrier layer and the third barrier layer form a quantum well structure. The application can effectively prevent the overflow of electrons in the quantum well structure by introducing the first barrier layer. Meanwhile, the construction of the third barrier layer not only further blocks the path of the leakage of electrons to the second-type semiconductor layer, but also reflects the electrons reaching the interface back to the quantum well structure due to the raised energy band structure, so that the overlapping degree of the electrons and holes is greatly increased, and the radiation recombination efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to an LED epitaxial structure and its fabrication method, and a light-emitting diode. Background Technology

[0002] Artificial light plant illumination research has shown that red light with wavelengths in the 640–680 nm range and far-red light with wavelengths in the 710–740 nm range can effectively regulate plant photoperiod, promoting flowering and increasing yield. Current technologies typically fabricate red LEDs based on epitaxial growth of AlGaInP or AlGaAs materials on GaAs substrates.

[0003] However, for far-red LEDs targeting wavelengths of 710–740 nm, the shallow band structure of their quantum wells allows charge carriers, especially electrons, to easily escape from the active region, leading to reduced luminous efficiency. Therefore, improving the carrier confinement effect and capture efficiency in the active region is a key direction for enhancing the photoelectric efficiency of far-red LEDs. With the market's increasing demands for LED performance, the low photoelectric efficiency of LEDs urgently needs to be addressed to meet these demands. Summary of the Invention

[0004] The purpose of this invention is to provide an LED epitaxial structure and its fabrication method, as well as a light-emitting diode, to improve the radiative recombination efficiency of the active region of the LED epitaxial structure, thereby improving the luminous efficiency of the LED epitaxial structure.

[0005] To solve the above-mentioned technical problems, the present invention provides an LED epitaxial structure, which includes, from bottom to top: a first type semiconductor layer, an active layer, and a second type semiconductor layer formed on a substrate;

[0006] The active layer includes a first barrier layer, a second barrier layer, a third barrier layer, and a potential well layer. The material of the active layer includes an aluminum component. The aluminum components in the first and second barrier layers are both greater than the aluminum components in the potential well layer. The potential well layer forms a quantum well structure with one of the first, second, and third barrier layers.

[0007] Preferably, the first barrier layer is disposed close to the first type of semiconductor layer, and the third barrier layer is disposed close to the second type of semiconductor layer.

[0008] Preferably, the first barrier layer, the second barrier layer, and the third barrier layer are arranged sequentially along the growth direction of the epitaxial structure.

[0009] Preferably, the material of the first barrier layer includes Al. x Ga 1-x As or AlxGa1-xAsP, where 0.3≤x≤0.85, and the value of x gradually decreases along the growth direction of the epitaxial structure.

[0010] Preferably, the thickness of the first barrier layer is in the range of 30–200 nm.

[0011] Preferably, the material of the potential well layer includes Al. y Ga 1-y As, where 0.05≤y≤0.25.

[0012] Preferably, the thickness of the potential well layer is in the range of 2–30 nm.

[0013] Preferably, the material of the second barrier layer includes Al. z Ga 1-z As, where 0.3≤z≤0.8.

[0014] Preferably, the thickness of the second barrier layer is in the range of 10 to 120 nm, and the thickness of the second barrier layer gradually increases along the growth direction of the epitaxial structure.

[0015] Preferably, the ratio of the thickness of the first barrier layer to the thickness of the second barrier layer is in the range of 10:1 to 1:1.

[0016] Preferably, the number of periods in the quantum well structure is 6 to 30.

[0017] Preferably, the third barrier layer includes a first post-barrier layer and a second post-barrier layer stacked sequentially, with the first post-barrier layer stacked on the surface of the second barrier layer.

[0018] Preferably, the material of the first post-barrier layer includes AliGa1-iAs, wherein 0.30≤i≤0.95.

[0019] Preferably, the material of the second post-barrier layer includes one of AlkGa1-kInP or AlInP, wherein 0.45≤k≤0.85, and the value of k gradually increases along the growth direction of the epitaxial structure.

[0020] Preferably, the thickness of the first post-barrier layer is 10–200 nm, and the thickness of the second post-barrier layer is 20–280 nm.

[0021] Preferably, the first type of semiconductor layer includes an n-type ohmic contact layer, an n-type window layer and an n-type confinement layer stacked sequentially along the epitaxial structure growth direction, and the second type of semiconductor layer includes a p-type confinement layer, a p-type window layer and a p-type ohmic contact layer stacked sequentially along the epitaxial structure growth direction.

[0022] Preferably, the system further includes a buffer layer and a stop layer, wherein the buffer layer is disposed on the surface of the substrate, the stop layer is disposed on the surface of the buffer layer, and the first type semiconductor layer is disposed on the surface of the stop layer.

[0023] Based on the same inventive concept, the present invention also provides a method for preparing the above-described LED epitaxial structure, comprising:

[0024] Provide a substrate;

[0025] A first type semiconductor layer is formed on the substrate;

[0026] An active layer is formed on the first type of semiconductor layer. The active layer includes a first barrier layer, a second barrier layer, a third barrier layer, and a potential well layer. The material of the active layer includes an aluminum component. The aluminum components in the first barrier layer and the second barrier layer are both greater than the aluminum components in the potential well layer. The potential well layer forms a quantum well structure with one of the first barrier layer, the second barrier layer, and the third barrier layer.

[0027] A second type semiconductor layer is formed on the active layer.

[0028] Based on the same inventive concept, the present invention also provides a light-emitting diode, comprising:

[0029] The LED epitaxial structure described above.

[0030] Compared with the prior art, the LED epitaxial structure of the present invention has the following advantages:

[0031] The active region of this invention includes a first barrier layer, a second barrier layer, a third barrier layer, and a potential well layer. The active layer is made of aluminum, with the aluminum content in the first and second barrier layers being greater than that in the potential well layer. The potential well layer forms a quantum well structure with one of the first, second, and third barrier layers. The introduction of the first barrier layer creates a higher band barrier for the quantum well structure, effectively preventing electron overflow. Simultaneously, the third barrier layer not only further blocks the path of electron leakage to the second-type semiconductor layer, but its elevated band structure also reflects electrons arriving at the interface back into the potential well layer, thereby greatly increasing the overlap between electrons and holes and improving radiative recombination efficiency.

[0032] In addition, by coordinating the structural design of the first and third barrier layers and optimizing the thickness of the second barrier layer, the transport of charge carriers is modulated by changing the potential energy of charge carriers passing through the potential well layers, thereby promoting a more uniform distribution of electrons and holes in all potential well layers and maximizing the overall radiative recombination rate. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the LED epitaxial structure in one embodiment of the present invention;

[0034] Figure 2This is a schematic diagram of the active layer structure in one embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram of the energy band structure of the active layer in one embodiment of the present invention;

[0036] Figure 4 This is a method for preparing an LED epitaxial structure according to one embodiment of the present invention;

[0037] In the picture,

[0038] 100 - Substrate; 110 - Buffer layer; 120 - Cut-off layer; 200 - Type I semiconductor layer; 210 - n-type ohmic contact layer; 220 - n-type window layer; 230 - n-type confinement layer; 300 - Active layer; 310 - First barrier layer; 320 - Second barrier layer; 330 - Third barrier layer; 331 - First back barrier layer; 332 - Second back barrier layer; 400 - Type II semiconductor layer; 410 - p-type confinement layer; 420 - p-type window layer; 430 - p-type ohmic contact layer. Detailed Implementation

[0039] To make the objectives, advantages, and features of the present invention clearer, the LED epitaxial structure and its fabrication method, as well as the light-emitting diode, proposed in this invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clearly illustrate the embodiments of the present invention. It should be understood that the accompanying drawings do not necessarily show the specific structure of the present invention to scale, and the illustrative features used to illustrate certain principles of the present invention in the accompanying drawings are also drawn in a slightly simplified manner. Specific design features of the present invention disclosed herein, including, for example, specific dimensions, orientations, positions, and shapes, will be determined in part by the specific application and environment in which they are used. Furthermore, in the embodiments described below, the same reference numerals are sometimes used across different drawings to denote the same parts or parts having the same function, and their repeated descriptions are omitted. In this specification, similar reference numerals and letters are used to denote similar items; therefore, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0040] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0041] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0042] Before describing embodiments according to the present invention, the following points will be explained in advance. First, in this specification, when only "AlGaInP" is designated, it refers to an arbitrary compound in which the chemical composition ratio of the sum of Al, Ga, and In to P is 1:1, and the ratio of Al, Ga, and In is not fixed. When only "AlGaAs" is designated, it refers to an arbitrary compound in which the chemical composition ratio of the sum of Al, Ga, and As is 1:1, and the ratio of Al, Ga, and In is not fixed. Furthermore, when only "AlInP" is designated, it refers to an arbitrary compound in which the chemical composition ratio of the sum of Al, In, and P is 1:1, and the ratio of Al and In is not fixed.

[0043] The core idea of ​​this invention is to provide an LED epitaxial structure that can improve the radiative recombination efficiency of the active region of the LED epitaxial structure, thereby improving the luminous efficiency of the LED epitaxial structure.

[0044] To achieve the above-mentioned ideas, this invention provides an LED epitaxial structure, with reference to... Figures 1 to 3 This invention discloses a specific embodiment of an LED epitaxial structure. The LED epitaxial structure includes a first type semiconductor layer 200, an active layer 300, and a second type semiconductor layer 400 located on a substrate. The active layer 300 includes a first barrier layer 310, a second barrier layer 320, a third barrier layer 330, and a potential well layer. The active layer 300 is made of aluminum, and the aluminum content in the first barrier layer 310 and the second barrier layer 320 is greater than the aluminum content in the potential well layer. The potential well layer forms a quantum well structure with one of the first barrier layer 310, the second barrier layer 320, and the third barrier layer 330.

[0045] In this embodiment, the active layer 300 includes a first barrier layer 310, a second barrier layer 320, a third barrier layer 330, and a potential well layer. The active layer 300 is made of aluminum. The aluminum content in the first barrier layer 310 and the second barrier layer 320 is greater than that in the potential well layer. The potential well layer forms a quantum well structure with one of the first barrier layer 310, the second barrier layer 320, and the third barrier layer 330. The introduction of the first barrier layer 310 creates a higher band barrier for the quantum well structure, which can effectively block electron overflow from the quantum well structure. At the same time, the third barrier layer 330 not only further blocks the path of electron leakage to the second type semiconductor layer 400, but its raised band structure also reflects electrons arriving at the interface back into the potential well layer, thereby greatly increasing the overlap between electrons and holes and improving the radiative recombination efficiency.

[0046] refer to Figure 1 As shown, in some embodiments, the substrate 100 is sapphire, silicon, etc., preferably a GaAs (gallium arsenide) substrate, but is not limited thereto, and no specific limitation is made here.

[0047] Continue to refer to Figure 1 As shown, in some embodiments, the epitaxial structure further includes a buffer layer 110 and a stop layer 120. The buffer layer 110 is disposed on the surface of the substrate 100, and the stop layer 120 is disposed on the surface of the buffer layer 110. The first type semiconductor layer 200 is disposed on the surface of the stop layer 120. The buffer layer 110 is grown on the surface of the substrate 100. The buffer layer 110 can minimize the influence of surface defects of the substrate 100 on the LED epitaxial structure, reduce the possibility of defects and dislocations in the LED epitaxial structure, and provide a smooth interface for the next growth step. The material of the buffer layer 110 is preferably GaAs, but not limited to this. In this embodiment, the thickness of the buffer layer 110 is preferably 50-450 nm.

[0048] Continue to refer to Figure 1 As shown, in some embodiments, a stop layer 120 is grown on the surface of the buffer layer 110. The material of the stop layer 120 is preferably GaInP, but is not limited thereto. The dopant of the stop layer 120 is an n-type dopant, preferably Si, but is not limited thereto. In this embodiment, the thickness of the stop layer 120 is preferably 200 nm to 500 nm.

[0049] Continue to refer to Figure 1 As shown, in some embodiments, a first type semiconductor layer 200 is grown on the surface of the cutoff layer 120. The first type semiconductor layer 200 is an electron supply layer responsible for providing electrons. The first type semiconductor layer 200 includes, along the epitaxial growth direction, a sequentially stacked n-type ohmic contact layer 210, an n-type window layer 220, and an n-type confinement layer 230.

[0050] The material of the n-type ohmic contact layer 210 is preferably GaAsP or GaAs, but is not limited thereto. In this embodiment, the thickness of the n-type ohmic contact layer 210 is preferably 150 nm to 230 nm.

[0051] An n-type window layer 220 is grown on the n-type ohmic contact layer 210. The material of the n-type window layer 220 is preferably AlGaInP, AlInP, or a composite layer of AlInP and AlGaInP, but it is not limited to these materials. The main functions of the n-type window layer 220 are current spreading, light emission, and surface roughening. In this embodiment, the thickness of the n-type window layer 220 is preferably 500 nm to 5000 nm.

[0052] An n-type confinement layer 230 is grown on the n-type window layer 220. The material of the n-type confinement layer 230 is preferably AlGaInP, AlInP, or a composite layer of AlInP and AlGaInP, but is not limited thereto. In this embodiment, the thickness of the n-type confinement layer 230 is preferably 100 nm to 3000 nm.

[0053] refer to Figures 1 to 3 As shown, in some embodiments, an active layer 300 is grown on the surface of the n-type confinement layer 230. The active layer 300 includes a first barrier layer 310, a second barrier layer 320, a third barrier layer 330, and a potential well layer. The first barrier layer 310 is disposed close to the first type semiconductor layer 200, and the third barrier layer 330 is disposed close to the second type semiconductor layer 400. The second barrier layer 320 is disposed between the first barrier layer 310 and the second barrier layer 320. The material of the active layer 300 includes an aluminum composition, with the aluminum composition in both the first barrier layer 310 and the second barrier layer 320 being greater than that in the potential well layer. Figure 3 As shown, the energy band of the first barrier layer 310 is significantly higher than that of the potential well layer, which makes the barrier of the first barrier layer 310 higher than that of the potential well layer. This can effectively block the electron overflow of the quantum well structure, increase the overlap between electrons and holes, and improve the radiative recombination efficiency.

[0054] refer to Figure 1 and Figure 2As shown, in some embodiments, the potential well layer forms a quantum well structure with one of the first barrier layer 310, the second barrier layer 320, and the third barrier layer 330. The potential well layer forms a periodically stacked quantum well structure with one of the first barrier layer 310, the second barrier layer 320, and the third barrier layer 330. In one embodiment, the first barrier layer 310 and the potential well layer form a quantum well structure. The number of periods in the quantum well structure formed by the first barrier layer 310 and the potential well layer is 6 to 30. The first barrier layer 310 is disposed close to the first type semiconductor layer, that is, the first barrier layer 310 is disposed close to the n-type confinement layer 230. In another embodiment, the second barrier layer 320 and the potential well layer form a periodically stacked quantum well structure, and the number of periods in the second barrier layer 320 and the potential well layer can also be 6 to 30. In other embodiments, the third barrier layer 330 and the potential well layer form a periodically stacked quantum well structure. The number of periods in the third barrier layer 330 and the potential well layer can also be 6 to 30, as long as the aluminum composition in the first barrier layer 310 and the second barrier layer 320 is greater than that in the potential well layer. The greater aluminum composition in the first barrier layer 310 and the second barrier layer 320 results in a higher barrier than that in the potential well layer, effectively preventing electron overflow from the potential well layer, increasing the overlap between electrons and holes, and improving radiative recombination efficiency. By alternating between high-aluminum barrier layers and low-aluminum potential well layers to form a periodic quantum confinement potential well array, multiple binding barriers are continuously formed for electrons and holes, progressively reducing the probability of carrier tunneling escape, effectively preventing electron overflow from the potential well layer, increasing the overlap between electrons and holes, and improving radiative recombination efficiency.

[0055] refer to Figures 1 to 3 As shown, in this embodiment, preferably, from bottom to top (i.e., the epitaxial growth direction), the first barrier layer 310, the second barrier layer 320, and the third barrier layer 330 are sequentially arranged along the epitaxial growth direction. The active layer 300 includes the first barrier layer 310, the quantum well structure, and the third barrier layer 330. The quantum well structure includes the second barrier layer 320 and the potential well layer. The aluminum composition in both the first barrier layer 310 and the second barrier layer 320 is greater than that in the potential well layer. The barrier of the first barrier layer 310 is higher than that of the potential well layer, which can effectively block electron overflow from the quantum well structure, increase the overlap between electrons and holes, and improve the radiative recombination efficiency. The third barrier layer can not only further block the path of electron leakage to the second type semiconductor layer, but its raised band structure also reflects electrons arriving at the interface back into the potential well layer, thereby greatly increasing the overlap between electrons and holes and improving the radiative recombination efficiency.

[0056] The active layer 300 is made of Al. m Ga 1-mAs. In some embodiments, the material of the first barrier layer 310 includes Al. x Ga 1-x As or Al x Ga 1-x AsP, where 0.3≤x≤0.85, along the growth direction of the epitaxial structure (i.e., Figure 1 (In the Z direction), the x value gradually decreases. The thickness of the first barrier layer 310 ranges from 30 to 200 nm. For example, the thickness of the first barrier layer 310 can be 30 nm, 100 nm, 150 nm, 200 nm, or any value within the range of 30 to 200 nm. By setting the first barrier layer 310, the barrier of the active layer 300 can be increased, preventing electrons provided by the first type semiconductor layer 200 from escaping from below the active layer 300, thereby improving the radiative recombination efficiency of the active layer 300 and thus enhancing the luminous efficiency of the LED epitaxial structure.

[0057] For ease of explanation, the following explanation will take the formation of a periodic quantum well structure between the second potential barrier 320 and the potential well layer as an example.

[0058] refer to Figure 3 As shown, the quantum well structure comprises a composite structure of a second barrier layer 320 and a well layer periodically stacked. The number of periods for the second barrier layer 320 and the well layer is 6 to 30, preferably 15. The material of the well layer includes Al. y Ga 1-y As, where 0.05 ≤ y ≤ 0.25. The thickness of the potential well layer ranges from 2 to 30 nm. For example, the thickness of the potential well layer can be 2 nm, 10 nm, 20 nm, 30 nm, or any value within the range of 2 to 30 nm, preferably 5 to 15 nm. The material of the second barrier layer 320 includes Al. z Ga 1- z As, where 0.3≤z≤0.8. The thickness of the second barrier layer 320 ranges from 10 to 120 nm, and gradually increases along the growth direction of the epitaxial structure. For example, the thickness of the second barrier layer 320 can be 10 nm, 50 nm, 80 nm, 120 nm, or any value within the range of 10 to 120 nm. By increasing the thickness of the second barrier layer 320 along the epitaxial growth direction (i.e., Figure 3 As the Z-direction of the LED gradually increases, the modulation of charge carriers (i.e., electrons and holes) through the potential energy, uniformly disperses electrons and holes, improves the overall radiative recombination rate, and thus improves the luminous efficiency of the LED epitaxial structure.

[0059] Further, refer to Figure 1As shown, in some embodiments, the ratio of the thickness of the first barrier layer 310 to the thickness of the second barrier layer 320 ranges from 10:1 to 1:1. If the first barrier layer 310 is too thick and the second barrier layer 320 is too thin (i.e., the ratio is greater than 10:1), the charge carriers are locked in a single well, the distribution of charge carriers in the multi-well layers is severely uneven, some wells are deficient in charge carriers, and the overall luminous efficiency decreases. If the first barrier layer 310 is too thin and the second barrier layer 320 is too thick (i.e., the ratio is less than 1:1), high-energy electrons can easily escape the active layer 300, the number of charge carriers in the wells decreases, and the radiative recombination rate decreases. By setting the ratio of the thickness of the first barrier layer 310 to the thickness of the second barrier layer 320 to be between 10:1 and 1:1, on the one hand, this thickness ratio ensures that the first barrier layer 310 has sufficient thickness to block the leakage of charge carriers, suppress the backflow and leakage of electrons in the active region to the first type semiconductor layer 200 (i.e., the n-type semiconductor layer), and increase the total number of charge carriers that can participate in radiative recombination inside the quantum well; on the other hand, the second barrier layer 320 maintains a relatively thin thickness, which does not excessively hinder the tunneling migration of charge carriers between adjacent quantum wells, promotes the uniform distribution of electrons and holes in the entire quantum well structure, fully utilizes the light-emitting capability of each potential well layer, and ultimately maximizes the radiative recombination rate of the active layer, thereby improving the luminous efficiency of the LED epitaxial structure.

[0060] Further, refer to Figure 2 As shown, the third barrier layer 330 includes a first post-barrier layer 331 and a second post-barrier layer 332 stacked sequentially, with the first post-barrier layer 331 stacked on the surface of the quantum well structure. The material of the first post-barrier layer 331 includes Al. i Ga 1-i As, where 0.30≤i≤0.95, the material of the second post-barrier layer 332 includes Al. k Ga 1-kThe material is either InP or AlInP, where 0.45 ≤ k ≤ 0.85. The thickness of the first post-barrier layer 331 is 10–200 nm. For example, the thickness of the first post-barrier layer 331 can be 10 nm, 50 nm, 100 nm, 200 nm, or any value within the range of 10–200 nm. The thickness of the second post-barrier layer 332 is 20–280 nm. For example, the thickness of the second post-barrier layer 332 can be 20 nm, 100 nm, 200 nm, 280 nm, or any value within the range of 20–280 nm, preferably 100 nm. By setting a first post-barrier layer 331 and a second post-barrier layer 332, the first post-barrier layer 331 serves as a transition buffer layer, initially blocking electrons; the second post-barrier layer 332 is a wide-bandgap In-based high-barrier layer, which completely blocks electron leakage for the second time without blocking hole injection; the dual-layer structure synergistically takes into account carrier confinement, hole transport, and stress buffering, reduces various non-radiative losses, maximizes the quantum well radiative recombination rate, and further improves the luminous efficiency of the LED epitaxial structure.

[0061] refer to Figure 2 and Figure 3 As shown, along the growth direction of the epitaxial structure (i.e., Figure 2 (in the Z direction), the value of k gradually increases, that is, the aluminum composition in the second post-barrier layer 332 gradually increases. By setting the aluminum composition in the second post-barrier layer 332 to gradually increase, a gradient-enhanced conduction band barrier can be formed, which smoothly blocks the leakage of electrons from the type II semiconductor layer 400 in the active layer 300, while ensuring continuous and uniform hole injection into the active layer 300. This improves the problem of carrier accumulation near the type II semiconductor layer 400, achieves uniform carrier distribution in the active layer, maximizes the radiative recombination rate, and thus improves the luminous efficiency of the LED epitaxial structure.

[0062] refer to Figure 1 As shown, in some embodiments, a second-type semiconductor layer 400 is grown on the surface of the second post-barrier layer 332. The second-type semiconductor layer 400 provides holes to the active layer 300, and electrons and holes are injected into the quantum well structure of the active layer 300 to cause radiative recombination luminescence. The second-type semiconductor layer 400 grows along the epitaxial growth direction (i.e., Figure 1 (in the Z direction) it includes a p-type confinement layer 410, a p-type window layer 420 and a p-type ohmic contact layer 430 stacked in sequence.

[0063] A p-type confinement layer 410 is grown on the surface of the second post-barrier layer 332. The material of the p-type confinement layer 410 is preferably AlGaInP or AlInP, but is not limited thereto. In this embodiment, the thickness of the p-type confinement layer 410 is preferably 100 to 2500 nm.

[0064] A p-type window layer 420 is grown on the surface of the p-type confinement layer 410. The material of the p-type window layer 420 is preferably GaP or GaInP, but is not limited thereto. In this embodiment, the thickness of the p-type window layer 420 is preferably 200-800 nm.

[0065] A p-type ohmic contact layer 430 is grown on the p-type window layer 420. The material of the p-type ohmic contact layer 430 is preferably GaP or GaInP, but is not limited thereto. In this embodiment, the thickness of the p-type ohmic contact layer 430 is preferably 25-200 nm.

[0066] In this embodiment, by increasing the aluminum content in both the first barrier layer 310 and the second barrier layer 320 compared to the aluminum content in the potential well layer, the barriers of both layers are higher than those of the potential well layer. The introduction of the first barrier layer 310 creates a higher band barrier, effectively preventing electron leakage from the quantum well structure. Simultaneously, the construction of the third barrier layer 330 not only further blocks the path of electron leakage into the P-region (i.e., the second-type semiconductor layer 400), but its elevated band structure also reflects electrons arriving at the interface back into the quantum well structure, thereby greatly increasing the overlap between electrons and holes and improving radiative recombination efficiency.

[0067] By increasing the thickness of the second barrier layer 320 along the epitaxial growth direction (i.e., Figure 3 As the Z-direction of the LED gradually increases, the modulation of charge carriers (i.e., electrons and holes) through the potential energy, uniformly disperses electrons and holes, improves the overall radiative recombination rate, and thus improves the luminous efficiency of the LED epitaxial structure.

[0068] By setting the ratio of the thickness of the first barrier layer 310 to the thickness of the second barrier layer 320 to a range of 10:1 to 1:1, this thickness ratio ensures that the first barrier layer 310 has sufficient thickness to block the leakage of charge carriers, suppress the backflow and leakage of electrons in the active region to the first type semiconductor layer 200 (i.e., the n-type semiconductor layer), and increase the total number of charge carriers that can participate in radiative recombination inside the quantum well. On the other hand, the second barrier layer 320 maintains a relatively thin thickness, which does not excessively hinder the tunneling migration of charge carriers between adjacent quantum wells, promotes the uniform distribution of electrons and holes in all quantum wells, fully utilizes the light-emitting capability of each quantum well layer, and ultimately maximizes the radiative recombination rate of the active layer, thereby improving the luminous efficiency of the LED epitaxial structure.

[0069] By setting the third barrier layer 330 as the first post-barrier layer 331 and the second post-barrier layer 332, the first post-barrier layer 331 serves as a transition buffer layer, initially blocking electrons; the second post-barrier layer 332 is a wide-bandgap In-based high barrier layer, which completely blocks electron leakage for the second time without blocking hole injection; the dual-layer structure synergistically takes into account carrier confinement, hole transport, and stress buffering, reduces various non-radiative losses, maximizes the quantum well radiative recombination rate, and further improves the luminous efficiency of the LED epitaxial structure.

[0070] By gradually increasing the aluminum content in the second post-barrier layer 332, a gradient-enhanced conduction band barrier can be formed, which smoothly blocks the leakage of electrons from the type II semiconductor layer 400 within the active layer 300. At the same time, it ensures continuous and uniform hole injection into the active layer 300, improves the problem of carrier accumulation near the type II semiconductor layer 400, achieves uniform carrier distribution in the active layer, maximizes the radiative recombination rate, and thus improves the luminous efficiency of the LED epitaxial structure.

[0071] To achieve the above idea, refer to Figure 1 and Figure 2 As shown, the present invention provides a light-emitting diode, comprising: the epitaxial structure as described above.

[0072] In this embodiment, the introduction of the first barrier layer 310 creates a high band barrier for the quantum well structure, effectively preventing electron overflow. Simultaneously, the construction of the third barrier layer 330 not only further blocks the path of electron leakage to the second-type semiconductor layer 400, but its elevated band structure also reflects electrons arriving at the interface back into the quantum well structure, thereby greatly increasing the overlap between electrons and holes, improving the luminous efficiency of the epitaxial structure, and thus enhancing the luminous efficiency of the light-emitting diode.

[0073] To achieve the above-mentioned goals, this invention provides a method for preparing an LED epitaxial structure, referring to... Figures 1 to 4 One specific embodiment of the disclosed method for preparing an LED epitaxial structure includes the following steps S1 to S5.

[0074] Step S1: Provide a substrate.

[0075] Step S2: Grow a buffer layer and a stop layer sequentially on the substrate.

[0076] refer to Figure 1As shown, a buffer layer 110 with a thickness of 50–450 nm is first grown in the reaction chamber of the MOCVD growth furnace. The material of the buffer layer 110 is preferably GaAs. Next, a stop layer 120 with a thickness of 200 nm–500 nm is grown. The material of the stop layer 120 is preferably GaInP. The dopant of the stop layer 120 is an n-type dopant, preferably Si, but not limited to this.

[0077] Step S3: Grow a first type semiconductor layer on the cutoff layer.

[0078] Continue to refer to Figure 1 The first type semiconductor layer 200 shown includes, along the epitaxial growth direction, a sequentially stacked n-type ohmic contact layer 210, an n-type window layer 220, and an n-type confinement layer 230. First, an n-type ohmic contact layer 210 with a thickness of 150 nm to 230 nm is grown on the stop layer 120. The material of the n-type ohmic contact layer 210 is preferably GaAsP or GaAs, but not limited thereto. Next, an n-type window layer 220 is grown on the n-type ohmic contact layer 210. The material of the n-type window layer 220 is preferably AlGaInP, AlInP, or a composite layer of AlInP and AlGaInP, but not limited thereto. The thickness of the n-type window layer 220 is preferably 500 nm to 5000 nm. Finally, an n-type confinement layer 230 is grown on the n-type window layer 220. The material of the n-type confinement layer 230 is preferably AlGaInP, AlInP, or a composite layer of AlInP and AlGaInP, but not limited thereto. The thickness of the n-type confinement layer 230 is preferably 100 nm to 3000 nm.

[0079] Step S4: An active layer is grown on the first type semiconductor layer. The active layer includes a first barrier layer, a second barrier layer, a third barrier layer, and a potential well layer. The material of the active layer includes an aluminum composition. The aluminum composition in the first barrier layer and the second barrier layer is greater than the aluminum composition in the potential well layer. The potential well layer forms a quantum well structure with one of the first barrier layer, the second barrier layer, and the third barrier layer.

[0080] refer to Figure 1 and Figure 2As shown, an active layer 300 is grown on the surface of the n-type confinement layer 230. The active layer 300 includes a first barrier layer 310, a second barrier layer 320, a third barrier layer 330, and a potential well layer. The potential well layer forms a quantum well structure with one of the first barrier layer 310, the second barrier layer 320, and the third barrier layer 330. For example, the quantum well structure 320 may include a composite structure of the second barrier layer 320 and the potential well layer periodically stacked. The third barrier layer 330 includes a first post-barrier layer 331 and a second post-barrier layer 332 stacked sequentially. First, a first barrier layer 310 with a thickness ranging from 30 to 200 nm is grown on the surface of the n-type confinement layer 230. The material of the first barrier layer 310 includes AlxGa1-xAs or Al x Ga 1-x AsP, where 0.3≤x≤0.85, and the value of x gradually decreases along the growth direction of the epitaxial structure.

[0081] In this embodiment, preferably, from bottom to top (i.e., in the epitaxial growth direction), the active layer 300 includes a first barrier layer 310, a quantum well structure, and a third barrier layer 330. The quantum well structure includes a second barrier layer 320 and a well layer. The aluminum content in both the first barrier layer 310 and the second barrier layer 320 is greater than that in the well layer. The barrier of the first barrier layer 310 is higher than that of the well layer, which can effectively block electron overflow from the quantum well structure, increase the overlap between electrons and holes, and improve radiative recombination efficiency. The third barrier layer not only further blocks the path of electron leakage to the second type semiconductor layer, but its raised band structure also reflects electrons arriving at the interface back into the well layer, thereby greatly increasing the overlap between electrons and holes and improving radiative recombination efficiency.

[0082] Next, a quantum well structure is grown on the surface of the first barrier layer 310. The quantum well structure comprises a composite structure of a second barrier layer 320 and a periodically stacked well layer, wherein the number of periods of the second barrier layer 320 and the well layer is 6 to 30, preferably 15. The material of the well layer includes Al. y Ga 1-y As, where 0.05 ≤ y ≤ 0.25. The thickness of the potential well layer ranges from 2 to 30 nm, preferably from 5 to 15 nm. The material of the second barrier layer 320 includes Al. z Ga 1-z As, where 0.3≤z≤0.8. The thickness of the second barrier layer 320 ranges from 10 to 120 nm, and the thickness of the second barrier layer 320 gradually increases along the growth direction of the epitaxial structure. The ratio of the thickness of the first barrier layer 310 to the thickness of the second barrier layer 320 ranges from 10:1 to 1:1.

[0083] Finally, a third barrier layer 330 is grown on the surface of the second barrier layer 320. The third barrier layer 330 includes a first post-barrier layer 331 and a second post-barrier layer 332 stacked sequentially. First, the first post-barrier layer 331 is grown on the surface of the second barrier layer 320, and then the second post-barrier layer 332 is grown on the surface of the first post-barrier layer 331. The material of the first post-barrier layer 331 includes AliGa1-iAs, where 0.40≤i≤0.95. The thickness of the first post-barrier layer 331 is 10-200 nm. The material of the second post-barrier layer 332 includes AlkGa1-kInP or AlInP, where 0.45≤k≤0.85, and the thickness of the second post-barrier layer 332 ranges from 20 to 280 nm. Preferably, along the growth direction of the epitaxial structure (i.e., Figure 2 (in the Z direction), the k value gradually increases, that is, the aluminum content in the second post-barrier layer 332 gradually increases.

[0084] Step S5: Grow a second type semiconductor layer on the active layer.

[0085] refer to Figure 1 As shown, a second type semiconductor layer 400 is grown on the surface of the second post-barrier layer 332. The second type semiconductor layer 400 is grown along the epitaxial structure growth direction (i.e., Figure 1 The layer (in the Z-direction) includes a p-type confinement layer 410, a p-type window layer 420, and a p-type ohmic contact layer 430 stacked sequentially. First, the p-type confinement layer 410 is grown on the surface of the second post-barrier layer 332. The material of the p-type confinement layer 410 is preferably AlGaInP or AlInP, but is not limited thereto. The thickness of the p-type confinement layer 410 is preferably 100–2500 nm.

[0086] Next, a p-type window layer 420 is grown on the surface of the p-type confinement layer 410. The material of the p-type window layer 420 is preferably GaP or GaInP, but is not limited thereto. The thickness of the p-type window layer 420 is preferably 200 to 800 nm.

[0087] Finally, a p-type ohmic contact layer 430 is grown on the p-type window layer 420. The material of the p-type ohmic contact layer 430 is preferably GaP or GaInP, but is not limited thereto. The thickness of the p-type ohmic contact layer 430 is preferably 25–200 nm.

[0088] It should be noted that the epitaxial structure is prepared using any one of the following processes: MOCVD, molecular beam epitaxy, HVPE, plasma-assisted chemical vapor deposition, and sputtering.

[0089] The LED epitaxial structure fabricated using the method provided in this embodiment achieves this by increasing the aluminum content in both the first barrier layer 310 and the second barrier layer 320 compared to the aluminum content in the potential well layer. Since the barriers of the first and second barrier layers 310 and 320 are higher than the barrier of the potential well layer, electrons and holes can be confined within the quantum well structure, preventing carrier leakage and improving the radiative recombination efficiency of the active layer, thereby enhancing the luminous efficiency of the LED epitaxial structure. Furthermore, the construction of the third barrier layer 330 not only further blocks the path of electron leakage into the P-region, but its elevated band structure also reflects electrons arriving at the interface back into the quantum well structure, significantly increasing the overlap between electrons and holes, improving radiative recombination efficiency, and further enhancing the luminous efficiency of the LED epitaxial structure.

[0090] In summary, the above embodiments have provided a detailed description of different configurations of light-emitting diodes. Of course, the above description is only a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. The present invention includes but is not limited to the configurations listed in the above embodiments. Those skilled in the art can draw inferences from the above embodiments. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. An LED epitaxial structure, characterized in that, From bottom to top, it includes: a first type semiconductor layer, an active layer, and a second type semiconductor layer formed on the substrate; The active layer includes a first barrier layer, a second barrier layer, a third barrier layer, and a potential well layer. The material of the active layer includes an aluminum component. The aluminum components in the first and second barrier layers are both greater than the aluminum components in the potential well layer. The potential well layer forms a quantum well structure with one of the first, second, and third barrier layers.

2. The LED epitaxial structure according to claim 1, characterized in that, The first barrier layer is disposed close to the first type semiconductor layer, and the third barrier layer is disposed close to the second type semiconductor layer.

3. The LED epitaxial structure according to claim 2, characterized in that, The first barrier layer, the second barrier layer, and the third barrier layer are arranged sequentially along the growth direction of the epitaxial structure.

4. The LED epitaxial structure according to claim 2, characterized in that, The material of the first barrier layer includes Al x Ga 1-x As or Al x Ga 1-x AsP, where 0.3≤x≤0.85, and the value of x gradually decreases along the growth direction of the epitaxial structure.

5. The LED epitaxial structure according to claim 3, characterized in that, The thickness of the first barrier layer ranges from 30 to 200 nm.

6. The LED epitaxial structure according to claim 1, characterized in that, The material of the potential well layer includes Al. y Ga 1-y As, where 0.05≤y≤0.

25.

7. The LED epitaxial structure according to claim 6, characterized in that, The thickness of the potential well layer ranges from 2 to 30 nm.

8. The LED epitaxial structure according to claim 1, characterized in that, The material of the second barrier layer includes Al z Ga 1-z As, where 0.3≤z≤0.

8.

9. The LED epitaxial structure according to claim 8, characterized in that, The thickness of the second barrier layer ranges from 10 to 120 nm, and the thickness of the second barrier layer gradually increases along the growth direction of the epitaxial structure.

10. The LED epitaxial structure according to claim 1, characterized in that, The ratio of the thickness of the first barrier layer to the thickness of the second barrier layer is in the range of 10:1 to 1:

1.

11. The LED epitaxial structure according to claim 1, characterized in that, The quantum well structure has a period number of 6 to 30.

12. The LED epitaxial structure according to claim 1, characterized in that, The third barrier layer includes a first post-barrier layer and a second post-barrier layer stacked sequentially, with the first post-barrier layer stacked on the surface of the second barrier layer.

13. The LED epitaxial structure according to claim 12, characterized in that, The material of the first post-barrier layer includes Al i Ga 1-i As, where 0.30≤i≤0.

95.

14. The LED epitaxial structure according to claim 12, characterized in that, The material of the second post-barrier layer includes Al k Ga 1-k One of InP or AlInP, wherein 0.45≤k≤0.85, and the value of k gradually increases along the growth direction of the epitaxial structure.

15. The LED epitaxial structure according to claim 12, characterized in that, The thickness of the first post-barrier layer is 10–200 nm, and the thickness of the second post-barrier layer is 20–280 nm.

16. The LED epitaxial structure according to claim 1, characterized in that, The first type of semiconductor layer includes, along the epitaxial growth direction, an n-type ohmic contact layer, an n-type window layer, and an n-type confinement layer stacked sequentially, and the second type of semiconductor layer includes, along the epitaxial growth direction, a p-type confinement layer, a p-type window layer, and a p-type ohmic contact layer stacked sequentially.

17. The LED epitaxial structure according to claim 1, characterized in that, It also includes a buffer layer and a stop layer, wherein the buffer layer is disposed on the surface of the substrate, the stop layer is disposed on the surface of the buffer layer, and the first type semiconductor layer is disposed on the surface of the stop layer.

18. A method for preparing an LED epitaxial structure as described in any one of claims 1-17, characterized in that, include: Provide a substrate; A first type semiconductor layer is formed on the substrate; An active layer is formed on the first type of semiconductor layer. The active layer includes a first barrier layer, a second barrier layer, a third barrier layer, and a potential well layer. The material of the active layer includes an aluminum component. The aluminum components in the first barrier layer and the second barrier layer are both greater than the aluminum components in the potential well layer. The potential well layer forms a quantum well structure with one of the first barrier layer, the second barrier layer, and the third barrier layer. A second type semiconductor layer is formed on the active layer.

19. A light-emitting diode, characterized in that, include: The LED epitaxial structure as described in any one of claims 1-17.

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