Epitaxial structure of light emitting diode and manufacturing method thereof

Abstract

The present invention provides an epitaxial structure of a light-emitting diode and a method for manufacturing the same. The epitaxial structure of the light-emitting diode comprises, from bottom to top, a substrate, a first semiconductor layer, an active layer, and a second semiconductor layer. The first semiconductor layer and the second semiconductor layer have opposite doping types. The second semiconductor layer comprises a superlattice layer, which is located closest to the active layer in the second semiconductor layer. The superlattice layer comprises periodically alternating well layers and barrier layers. The Al composition of the barrier layers is greater than that of the well layers, the Al composition of each well layer is the same, and the Al composition of each barrier layer increases from bottom to top. The doping concentration of the barrier layers is higher than that of the well layers, the doping concentration of each well layer is the same, and the doping concentration of each barrier layer increases from bottom to top. The technical solution of the present invention enables improved luminous efficiency and brightness of light-emitting diodes.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to an epitaxial structure of a light emitting diode and a manufacturing method thereof. Background Art

[0002] Light-emitting diodes (LEDs) are electronic components that convert electrical energy directly into light energy by generating photons through the radiative recombination of conduction-band electrons and valence-band holes in semiconductor materials. Compared to traditional incandescent and fluorescent lamps, LEDs offer advantages such as high efficiency, energy conservation, environmental friendliness, and a long lifespan. They play a vital role in energy conservation, emission reduction, and green development, and are widely recognized as the next generation of green lighting sources for the 21st century.

[0003] The quantum efficiency of a light-emitting diode (LED) is determined by both its external quantum efficiency and its internal quantum efficiency. The internal quantum efficiency refers to the efficiency with which carriers injected from the electrode recombine within the active layer to generate photons. The number of carriers in the active layer and the probability of electron-hole pair recombination determine the internal quantum efficiency of the LED. Although the effective mass of electrons is much smaller than that of holes, their mobility is much greater. Therefore, some electrons not confined within the active layer will recombine and emit light outside the active layer, generating stray light. This reduces the number of carriers within the active layer and the radiative recombination rate of electrons and holes within the active layer, thus affecting the internal quantum efficiency of the LED and, consequently, reducing its luminous efficiency and brightness.

[0004] Therefore, an epitaxial structure of a light emitting diode and a manufacturing method thereof are provided to improve the luminous efficiency and brightness of the light emitting diode. Summary of the Invention

[0005] An object of the present invention is to provide an epitaxial structure of a light emitting diode and a manufacturing method thereof, so as to improve the luminous efficiency and brightness of the light emitting diode.

[0006] To achieve the above-mentioned objectives, the present invention provides an epitaxial structure of a light-emitting diode, comprising, from bottom to top, a substrate, a first semiconductor layer, an active layer, and a second semiconductor layer, wherein the first semiconductor layer and the second semiconductor layer have opposite doping types, the second semiconductor layer comprises a superlattice layer, the superlattice layer is located at a position closest to the active layer in the second semiconductor layer, the superlattice layer comprises periodically alternating well layers and barrier layers, the Al composition of the barrier layer is greater than the Al composition of the well layer, the Al composition of each well layer is the same, and the Al composition of each barrier layer increases layer by layer from bottom to top; the doping concentration of the barrier layer is higher than the doping concentration of the well layer, the doping concentration of each well layer is the same, and the doping concentration of each barrier layer increases layer by layer from bottom to top.

[0007] Optionally, the material of the well layer is (Alx Ga 1-x ) 0.5 In 0.5 P, the material of the barrier layer is (Al y Ga 1-y ) 0.5 In 0.5 P, 0 <x<y<1。

[0008] Optionally, the Al composition of each barrier layer increases layer by layer from bottom to top, △y=(y max -y min ) / (k-1), where y max is the Al component of the topmost barrier layer, y min is the Al composition of the bottommost barrier layer, and k is the number of periods of the periodic alternating stacking.

[0009] Optionally, the doping concentration of each barrier layer increases layer by layer from bottom to top by a value △n=(n max -n min ) / (k-1), where n max is the doping concentration of the topmost barrier layer, n min is the doping concentration of the bottom barrier layer, and k is the number of periods of the periodic alternating stacking.

[0010] Alternatively, 1E18cm -3 <m<n<5E18cm -3 , where m is the doping concentration of the well layer, and n is the doping concentration of the barrier layer.

[0011] Optionally, the number of periods of the periodic alternating stacking is 2 to 20.

[0012] Optionally, the thickness of the superlattice layer is 14 nm to 300 nm, the thickness of the well layer is 2 nm to 5 nm, and the thickness of the barrier layer is 5 nm to 10 nm.

[0013] Optionally, the thickness of the barrier layer is greater than the thickness of the well layer.

[0014] Optionally, the first semiconductor layer includes a first ohmic contact layer, a first buffer layer, a first window layer and a first confinement layer from bottom to top; the second semiconductor layer also includes a second confinement layer, a transition layer, a second window layer and a second ohmic contact layer from bottom to top, and the superlattice layer is located between the active layer and the second confinement layer.

[0015] The present invention also provides a method for manufacturing an epitaxial structure of a light emitting diode, comprising:

[0016] providing a substrate;

[0017] A first semiconductor layer, an active layer, and a second semiconductor layer are sequentially stacked on the substrate, wherein the first semiconductor layer and the second semiconductor layer have opposite doping types, the second semiconductor layer includes a superlattice layer, the superlattice layer is located at a position closest to the active layer in the second semiconductor layer, the superlattice layer includes periodically alternating well layers and barrier layers, the Al composition of the barrier layer is greater than the Al composition of the well layer, the Al composition of each well layer is the same, and the Al composition of each barrier layer increases layer by layer from bottom to top; the doping concentration of the barrier layer is higher than the doping concentration of the well layer, the doping concentration of each well layer is the same, and the doping concentration of each barrier layer increases layer by layer from bottom to top.

[0018] Optionally, the material of the well layer is (Al x Ga 1-x ) 0.5 In 0.5 P, the material of the barrier layer is (Al y Ga 1-y ) 0.5 In 0.5 P, 0 <x<y<1。

[0019] Optionally, the Al composition of each barrier layer increases layer by layer from bottom to top, △y=(y max -y min ) / (k-1), where y max is the Al component of the topmost barrier layer, y min is the Al composition of the bottommost barrier layer, and k is the number of periods of the periodic alternating stacking.

[0020] Optionally, the doping concentration of each barrier layer increases layer by layer from bottom to top by a value △n=(n max -n min ) / (k-1), where n max is the doping concentration of the topmost barrier layer, n min is the doping concentration of the bottom barrier layer, and k is the number of periods of the periodic alternating stacking.

[0021] Alternatively, 1E18cm -3 <m<n<5E18cm -3 , where m is the doping concentration of the well layer, and n is the doping concentration of the barrier layer.

[0022] Optionally, the number of periods of the periodic alternating stacking is 2 to 20.

[0023] Optionally, the thickness of the superlattice layer is 14 nm to 300 nm, the thickness of the well layer is 2 nm to 5 nm, and the thickness of the barrier layer is 5 nm to 10 nm.

[0024] Optionally, the thickness of the barrier layer is greater than the thickness of the well layer.

[0025] Optionally, the first semiconductor layer includes a first ohmic contact layer, a first buffer layer, a first window layer and a first confinement layer from bottom to top; the second semiconductor layer also includes a second confinement layer, a transition layer, a second window layer and a second ohmic contact layer from bottom to top, and the superlattice layer is located between the active layer and the second confinement layer.

[0026] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0027] The epitaxial structure of a light-emitting diode and a manufacturing method thereof of the present invention are as follows: since the second semiconductor layer includes a superlattice layer, the superlattice layer is located at a position in the second semiconductor layer closest to the active layer, the superlattice layer includes periodically alternating well layers and barrier layers, the Al composition of the barrier layer is greater than the Al composition of the well layer, the Al composition of each well layer is the same, and the Al composition of each barrier layer increases layer by layer from bottom to top; the doping concentration of the barrier layer is higher than the doping concentration of the well layer, the doping concentration of each well layer is the same, and the doping concentration of each barrier layer increases layer by layer from bottom to top, thereby improving the luminous efficiency and brightness of the light-emitting diode. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic structural diagram of an epitaxial structure of a light emitting diode according to an embodiment of the present invention;

[0029] Figure 2 is a schematic structural diagram of a superlattice layer according to an embodiment of the present invention;

[0030] Figure 3 The flowchart is a method for manufacturing an epitaxial structure of a light emitting diode according to an embodiment of the present invention.

[0031] Among them, Figures 1 to 3 The reference numerals are described as follows:

[0032] 11-substrate; 121-bottom buffer layer; 122-etching stop layer; 123-first ohmic contact layer; 124-first buffer layer; 125-first window layer; 126-first confinement layer; 131-first waveguide layer; 132-light-emitting layer; 133-second waveguide layer; 141-superlattice layer; 1411-well layer; 1412-barrier layer; 142-second confinement layer; 143-transition layer; 144-second window layer; 145-second ohmic contact layer. DETAILED DESCRIPTION

[0033] To further clarify the objectives, advantages, and features of the present invention, the epitaxial structure of the light-emitting diode and its manufacturing method proposed in the present invention are further described below. It should be noted that the accompanying drawings are highly simplified and not to exact scale, and are only used to facilitate and clearly illustrate the purpose of the embodiments of the present invention.

[0034] An embodiment of the present invention provides an epitaxial structure of a light-emitting diode, comprising, from bottom to top, a substrate, a first semiconductor layer, an active layer, and a second semiconductor layer, wherein the first semiconductor layer and the second semiconductor layer have opposite doping types, the second semiconductor layer comprises a superlattice layer, the superlattice layer is located at a position closest to the active layer in the second semiconductor layer, the superlattice layer comprises periodically alternating well layers and barrier layers, the Al composition of the barrier layer is greater than the Al composition of the well layer, the Al composition of each well layer is the same, and the Al composition of each barrier layer increases layer by layer from bottom to top; the doping concentration of the barrier layer is higher than the doping concentration of the well layer, the doping concentration of each well layer is the same, and the doping concentration of each barrier layer increases layer by layer from bottom to top.

[0035] See below Figures 1 and 2 The epitaxial structure of the light emitting diode provided in this embodiment is described in more detail. Figures 1 and 2 It is also a longitudinal cross-sectional diagram.

[0036] The epitaxial structure of the light-emitting diode includes, from bottom to top, a substrate 11, a first semiconductor layer, an active layer, and a second semiconductor layer. The doping types of the first semiconductor layer and the second semiconductor layer are opposite. The second semiconductor layer includes a superlattice layer 141. The superlattice layer 141 is located at a position closest to the active layer in the second semiconductor layer. The superlattice layer 141 includes periodically alternating well layers 1411 and barrier layers 1412. The Al composition of the barrier layers 1412 is greater than the Al composition of the well layers 1411. The Al composition of each well layer 1411 is the same. The Al composition of each barrier layer 1412 increases layer by layer from bottom to top. The doping concentration of the barrier layer 1412 is higher than the doping concentration of the well layer 1411. The doping concentration of each well layer 1411 is the same. The doping concentration of each barrier layer 1412 increases layer by layer from bottom to top.

[0037] The substrate 11 is made of gallium arsenide, but is not limited thereto.

[0038] The first semiconductor layer, the active layer, and the second semiconductor layer constitute epitaxial layers of the light emitting diode.

[0039] Preferably, the doping type of the first semiconductor layer is N-type, and the doping type of the second semiconductor layer is P-type. The N-type dopant can be at least one of silicon, germanium, tin, tellurium, etc., but not limited thereto; the P-type dopant can be at least one of carbon, magnesium, zinc, cadmium, beryllium, and manganese, etc., but not limited thereto.

[0040] Since the second semiconductor layer includes the superlattice layer 141, and the superlattice layer 141 is located at the position closest to the active layer in the second semiconductor layer, it is possible to reduce the stress generated by the active layer, improve the crystal quality, thereby improving the stability of the light-emitting diode and making it more durable and reliable.

[0041] Compared with the well layer 1411 with a low Al component, the doping efficiency of the barrier layer 1412 with a high Al component is lower. Therefore, the doping concentration of the barrier layer 1412 is set higher than that of the well layer 1411, so that the barrier layer 1412 with a high doping concentration can provide a large number of holes; and, the well layer 1411 with a low doping concentration is combined with the barrier layer 1412 with a high doping concentration, so that the superlattice layer 141 can block the holes from overflowing from the active layer to the second semiconductor layer while providing a large number of holes.

[0042] Among them, in the periodically alternating stacked well layer 1411 and barrier layer 1412, the well layer 1411 or the barrier layer 1412 can be located at the bottommost layer.

[0043] In the single-layer well layer 1411 and single-layer barrier layer 1412, the Al component is uniformly distributed; in the single-layer well layer 1411 and single-layer barrier layer 1412, the doping concentration is uniformly distributed.

[0044] Preferably, the material of the well layer 1411 is (Al x Ga 1-x ) 0.5 In 0.5 P, and the material of the barrier layer 1412 is (Al y Ga 1-y ) 0.5 In 0.5 P. Among them, 0 < x < y < 1, that is, the Al component of the barrier layer 1412 is greater than that of the well layer 1411, and the Al components of the barrier layer 1412 and the well layer 1411 are both greater than 0 and less than 1.

[0045] Preferably, the value △y of the Al component of each layer of the barrier layer 1412 increasing layer by layer from bottom to top is △y = (y max -y min ) / (k - 1), where y maxis the Al component of the topmost barrier layer 1412, y min is the Al composition of the bottommost barrier layer 1412, and k is the number of periods of the periodic alternating stacking. That is, the Al composition of each barrier layer 1412 increases uniformly from bottom to top, and the Al composition of two adjacent barrier layers 1412 increases by the same value, so that the following effects can be achieved: (1) reducing the obstruction encountered by carriers when transmitting in the barrier layer 1412 material, thereby improving the carrier transmission efficiency; (2) optimizing the energy band structure of the barrier layer 1412 material, that is, as the Al composition of each barrier layer 1412 increases uniformly from bottom to top, the energy band of each barrier layer 1412 increases layer by layer from bottom to top, resulting in a higher effective barrier height for electrons, which is more conducive to electron confinement and increases the probability of electron and hole recombination in the active layer, thereby improving its photoelectric performance. In other embodiments, the Al composition of each barrier layer 1412 can be non-uniformly increased from bottom to top.

[0046] Preferably, the doping concentration of each barrier layer 1412 increases layer by layer from bottom to top. △n=(n max -n min ) / (k-1), where n max is the doping concentration of the topmost barrier layer 1412, n min is the doping concentration of the bottommost barrier layer 1412, and k is the number of periods of the periodic alternating stacking. Specifically, the doping concentration of each barrier layer 1412 increases uniformly from bottom to top, with the doping concentration increase of two adjacent barrier layers 1412 being the same, thereby matching the uniform increase in the Al composition of the barrier layer 1412 from bottom to top. Furthermore, this increase in doping concentration can increase hole mobility, thereby improving the conductivity of the light-emitting diode and reducing resistance. In other embodiments, the doping concentration of each barrier layer 1412 can also increase non-uniformly from bottom to top.

[0047] Preferably, 1E18cm -3 <m<n<5E18cm -3 , where m is the doping concentration of the well layer 1411, and n is the doping concentration of the barrier layer 1412. If the doping concentrations of the well layer 1411 and the barrier layer 1412 are too high, defects in the epitaxial structure may increase, thereby reducing the brightness of the light-emitting diode. If the doping concentrations are too low, a large number of holes may not be effectively provided.

[0048] Preferably, the number of periods of the periodic alternating stacking is 2 to 20.

[0049] Preferably, the thickness of the superlattice layer 141 is 14 nm to 300 nm.

[0050] Preferably, the thickness of the barrier layer 1412 is greater than the thickness of the well layer 1411. Further preferably, the thickness of the well layer 1411 is 2 nm to 5 nm, and the thickness of the barrier layer 1412 is 5 nm to 10 nm.

[0051] Since the thickness of the barrier layer 1412 can affect the movement and energy level structure of electrons in the barrier layer 1412 material, when the thickness of the barrier layer 1412 is greater than the thickness of the well layer 1411, it can better prevent electrons in the carriers from leaking from the active layer to the second confinement layer 142 in the second semiconductor layer.

[0052] The first semiconductor layer includes, from bottom to top, a first ohmic contact layer 123 , a first buffer layer 124 , a first window layer 125 and a first confinement layer 126 , but is not limited thereto. The structure of the first semiconductor layer can be configured according to actual needs.

[0053] A bottom buffer layer 121 and an etching stop layer 122 may be formed between the substrate 11 and the first semiconductor layer. The bottom buffer layer 121 is closer to the substrate 11 than the etching stop layer 122 .

[0054] The bottom buffer layer 121 is used to eliminate the influence of the surface defects of the substrate 11 on the epitaxial layer of the light-emitting diode to the greatest extent, reduce the probability of defects and dislocations in the epitaxial layer of the light-emitting diode, and provide a flat surface for the next growth step.

[0055] The bottom buffer layer 121 can be made of, but is not limited to, GaAs. The bottom buffer layer 121 can be doped with a first-type dopant, such as an N-type dopant. Preferably, the bottom buffer layer 121 has a thickness of 200 nm to 300 nm; more preferably, the bottom buffer layer 121 has a thickness of 200 nm.

[0056] The material of the etch-stop layer 122 can be, but is not limited to, GaInP. The etch-stop layer 122 can be doped with a first-type dopant, such as an N-type dopant. Preferably, the thickness of the etch-stop layer 122 is 10 nm to 20 nm; more preferably, the thickness of the etch-stop layer 122 is 20 nm.

[0057] The material of the first ohmic contact layer 123 can be AlGaInP or GaAs, but is not limited thereto. Preferably, the thickness of the first ohmic contact layer 123 is 5 nm to 10 nm; more preferably, the thickness of the first ohmic contact layer 123 is 10 nm.

[0058] The material of the first buffer layer 124 can be GaInP, but is not limited thereto. Preferably, the thickness of the first buffer layer 124 is 15 nm to 25 nm; more preferably, the thickness of the first buffer layer 124 is 15 nm.

[0059] The functions of the first window layer 125 include current spreading, light extraction, and surface roughening.

[0060] The material of the first window layer 125 can be AlGaInP, but is not limited thereto. Preferably, the thickness of the first window layer 125 is 1500 nm to 3000 nm; more preferably, the thickness of the first window layer 125 is 2000 nm.

[0061] The first confinement layer 126 is used to provide electrons and confine the light field distribution.

[0062] The material of the first confinement layer 126 can be AlInP, but is not limited thereto. Preferably, the thickness of the first confinement layer 126 is 1200 nm to 1500 nm; more preferably, the thickness of the first confinement layer 126 is 1500 nm.

[0063] The active layer includes a first waveguide layer 131, a light-emitting layer 132, and a second waveguide layer 133 from bottom to top.

[0064] The material of the first waveguide layer​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Preferably, the thickness of the light-emitting layer 132 is 150 nm to 480 nm, the thickness of the potential well layer is 5 nm to 10 nm, and the thickness of the potential barrier layer is 20 nm to 30 nm.

[0068] The material of the second waveguide layer 133 can be (Al w Ga 1-w ) 0.5 In 0.5 P, 0.5≤w≤1, but not limited thereto. Preferably, the thickness of the second waveguide layer 133 is 60nm-80nm; more preferably, the thickness of the second waveguide layer 133 is 80nm.

[0069] The first waveguide layer 131 and the second waveguide layer 133 are both undoped, and the first waveguide layer 131 and the second waveguide layer 133 are respectively used to block dopant ions in the first semiconductor layer and the second semiconductor layer from entering the light emitting layer 132 .

[0070] The second semiconductor layer includes, from bottom to top, a second confinement layer 142 , a transition layer 143 , a second window layer 144 and a second ohmic contact layer 145 . The superlattice layer 141 is located between the active layer and the second confinement layer 142 .

[0071] Since the superlattice layer 141 is located between the active layer and the second confinement layer 142, the superlattice layer 141 can prevent the holes in the active layer from escaping to the second confinement layer 142, thereby improving the lateral expansion of the holes. At the same time, it can block the leakage of electrons in the active layer, increase the hole injection efficiency, and improve the probability of electron and hole recombination.

[0072] The second confinement layer 142 is used to provide holes.

[0073] The material of the second confinement layer 142 may be AlInP, but is not limited thereto. Preferably, the thickness of the second confinement layer 142 is 1200 nm to 1500 nm; more preferably, the thickness of the second confinement layer 142 is 1500 nm.

[0074] The material of the transition layer 143 may be AlGaInP, but is not limited thereto. Preferably, the thickness of the transition layer 143 is 5 nm to 10 nm; more preferably, the thickness of the transition layer 143 is 10 nm.

[0075] The material of the second window layer 144 can be GaP, but is not limited thereto. Preferably, the thickness of the second window layer 144 is 3000 nm to 5000 nm; more preferably, the thickness of the second window layer 144 is 4000 nm.

[0076] The second ohmic contact layer 145 is used to form an ohmic contact with an electrode.

[0077] The material of the second ohmic contact layer 145 can be GaP, but is not limited thereto. Preferably, the thickness of the second ohmic contact layer 145 is 100 nm to 200 nm; more preferably, the thickness of the second ohmic contact layer 145 is 150 nm.

[0078] From the above content, it can be seen that in the epitaxial structure of the light-emitting diode provided by the present invention, since the doping concentration of the barrier layer 1412 is higher than the doping concentration of the well layer 1411, the well layer 1411 with a low doping concentration can prevent P-type doping ions from diffusing into the active layer, and the barrier layer 1412 with a high doping concentration can provide a large number of holes; and, the well layer 1411 with a low doping concentration is combined with the barrier layer 1412 with a high doping concentration, so that the superlattice layer 141 can block the holes from overflowing from the active layer to the second semiconductor layer while providing a large number of holes. At the same time, the well layer 1411 in the superlattice layer 141 can bind a large number of holes to form a two-dimensional hole high-density state; the barrier layer 1412 in the superlattice layer 141 can prevent the holes in the active layer from escaping to the second confinement layer 142, thereby improving the lateral expansion of the holes, effectively blocking electron leakage, increasing the hole injection efficiency, and improving the probability of electron and hole recombination, thereby improving the luminous efficiency and brightness of the light-emitting diode.

[0079] Among them, since the higher the effective barrier height, the fewer electrons can cross the barrier, and the more conducive to electron restriction, the superlattice layer 141 can reduce the effective barrier height for holes in the valence band, and at the same time, electron leakage is suppressed, so that the probability of holes and leaked electrons in the second semiconductor layer undergoing non-radiative recombination is reduced, thereby further improving the hole injection efficiency in the active layer; and the superlattice layer 141 has a higher effective barrier height for electrons, which is more conducive to electron leakage restriction, and the superlattice layer 141 has a lower effective barrier height for holes, which is more conducive to hole injection; at the same time, the superlattice layer 141 increases the hole injection efficiency, and there are enough holes and electrons in the active layer for radiative recombination, which increases the radiative recombination probability of holes and electrons in the active area, thereby improving the luminous efficiency and brightness of the light-emitting diode.

[0080] In summary, the epitaxial structure of a light-emitting diode provided by the present invention includes, from bottom to top, a substrate, a first semiconductor layer, an active layer, and a second semiconductor layer. The first semiconductor layer and the second semiconductor layer have opposite doping types. The second semiconductor layer includes a superlattice layer, which is located closest to the active layer in the second semiconductor layer. The superlattice layer includes periodically alternating well layers and barrier layers. The Al composition of the barrier layers is greater than that of the well layers, the Al composition of each well layer is the same, and the Al composition of each barrier layer increases from bottom to top. The doping concentration of the barrier layer is higher than that of the well layer, the doping concentration of each well layer is the same, and the doping concentration of each barrier layer increases from bottom to top. The present invention enables improved luminous efficiency and brightness of light-emitting diodes.

[0081] An embodiment of the present invention provides a method for manufacturing an epitaxial structure of a light emitting diode. Figure 3 , Figure 3 1 is a flow chart of a method for manufacturing an epitaxial structure of a light-emitting diode according to an embodiment of the present invention. The method for manufacturing an epitaxial structure of a light-emitting diode includes:

[0082] Step S1, providing a substrate;

[0083] Step S2, sequentially forming a first semiconductor layer, an active layer, and a second semiconductor layer stacked on the substrate, wherein the first semiconductor layer and the second semiconductor layer have opposite doping types, the second semiconductor layer includes a superlattice layer, the superlattice layer is located at a position closest to the active layer in the second semiconductor layer, the superlattice layer includes periodically alternating well layers and barrier layers, the Al composition of the barrier layer is greater than the Al composition of the well layer, the Al composition of each well layer is the same, and the Al composition of each barrier layer increases layer by layer from bottom to top; the doping concentration of the barrier layer is higher than the doping concentration of the well layer, the doping concentration of each well layer is the same, and the doping concentration of each barrier layer increases layer by layer from bottom to top.

[0084] See below Figures 1 and 2 The method for manufacturing the epitaxial structure of the light emitting diode provided in this embodiment is described in more detail.

[0085] According to step S1 , a substrate 11 is provided.

[0086] The substrate 11 is made of gallium arsenide, but is not limited thereto.

[0087] According to step S2, a first semiconductor layer, an active layer, and a second semiconductor layer are sequentially formed and stacked on the substrate, wherein the doping types of the first semiconductor layer and the second semiconductor layer are opposite, and the second semiconductor layer includes a superlattice layer 141, which is located at a position closest to the active layer in the second semiconductor layer, and the superlattice layer 141 includes periodically alternating well layers 1411 and barrier layers 1412, wherein the Al composition of the barrier layers 1412 is greater than the Al composition of the well layers 1411, the Al composition of each layer of the well layers 1411 is the same, and the Al composition of each layer of the barrier layers 1412 increases layer by layer from bottom to top; the doping concentration of the barrier layers 1412 is higher than the doping concentration of the well layers 1411, the doping concentration of each layer of the well layers 1411 is the same, and the doping concentration of each layer of the barrier layers 1412 increases layer by layer from bottom to top.

[0088] The first semiconductor layer, the active layer and the second semiconductor layer can be grown in sequence on the substrate 11 by using any one of a metal organic compound chemical vapor deposition (MOCVD) process, a molecular beam epitaxy (MBE) process, an ultra-high vacuum chemical vapor deposition (UHVCVD) process, a hydride vapor phase epitaxy (HVPE) process, a plasma-assisted chemical vapor deposition process and a sputtering method, and a metal organic compound chemical vapor deposition process is preferably used.

[0089] The first semiconductor layer, the active layer, and the second semiconductor layer constitute epitaxial layers of the light emitting diode.

[0090] Preferably, the doping type of the first semiconductor layer is N-type, and the doping type of the second semiconductor layer is P-type. The N-type dopant may be at least one of silicon, germanium, tin, and tellurium, but is not limited thereto; the P-type dopant may be at least one of carbon, magnesium, zinc, cadmium, beryllium, and manganese, but is not limited thereto.

[0091] Since the second semiconductor layer includes the superlattice layer 141 and the superlattice layer 141 is located closest to the active layer in the second semiconductor layer, the stress generated in the active layer can be reduced, the crystal quality can be improved, and the stability of the light-emitting diode can be improved, making it more durable and reliable.

[0092] Compared with the well layer 1411 having a low Al component, the doping efficiency of the barrier layer 1412 having a high Al component is lower. Therefore, the doping concentration of the barrier layer 1412 is set higher than that of the well layer 1411, so that the barrier layer 1412 with a high doping concentration can provide a large number of holes; and, the well layer 1411 with a low doping concentration is combined with the barrier layer 1412 with a high doping concentration, so that the superlattice layer 141 can block holes from overflowing from the active layer to the second semiconductor layer while providing a large number of holes.

[0093] Among the periodically alternately stacked well layer 1411 and barrier layer 1412, the bottommost layer can be the well layer 1411 or the barrier layer 1412.

[0094] In the single-layer well layer 1411 and the single-layer barrier layer 1412, the Al component is uniformly distributed; in the single-layer well layer 1411 and the single-layer barrier layer 1412, the doping concentration is uniformly distributed.

[0095] Preferably, the material of the well layer 1411 is (Al x Ga 1-x ) 0.5 In 0.5 P, and the material of the barrier layer 1412 is (Al y Ga 1-y ) 0.5 In 0.5 P. Among them, 0 < x < y < 1, that is, the Al component of the barrier layer 1412 is greater than that of the well layer 1411, and the Al components of the barrier layer 1412 and the well layer 1411 are both greater than 0 and less than 1.

[0096] Preferably, the value △y of the Al component of each barrier layer 1412 increasing layer by layer from bottom to top is △y=(y max -y min ) / (k - 1), where y max is the Al component of the topmost barrier layer 1412, y minis the Al composition of the bottommost barrier layer 1412, and k is the number of periods of the periodic alternating stacking. That is, the Al composition of each barrier layer 1412 increases uniformly from bottom to top, and the Al composition of two adjacent barrier layers 1412 increases by the same value, so that the following effects can be achieved: (1) reducing the obstruction encountered by carriers when transmitting in the barrier layer 1412 material, thereby improving the carrier transmission efficiency; (2) optimizing the energy band structure of the barrier layer 1412 material, that is, as the Al composition of each barrier layer 1412 increases uniformly from bottom to top, the energy band of each barrier layer 1412 increases layer by layer from bottom to top, resulting in a higher effective barrier height for electrons, which is more conducive to electron confinement and increases the probability of electron and hole recombination in the active layer, thereby improving its photoelectric performance. In other embodiments, the Al composition of each barrier layer 1412 can be non-uniformly increased from bottom to top.

[0097] Preferably, the doping concentration of each barrier layer 1412 increases layer by layer from bottom to top. △n=(n max -n min ) / (k-1), where n max is the doping concentration of the topmost barrier layer 1412, n min is the doping concentration of the bottommost barrier layer 1412, and k is the number of periods of the periodic alternating stacking. Specifically, the doping concentration of each barrier layer 1412 increases uniformly from bottom to top, with the doping concentration increase of two adjacent barrier layers 1412 being the same, thereby matching the uniform increase in the Al composition of the barrier layer 1412 from bottom to top. Furthermore, this increase in doping concentration can increase hole mobility, thereby improving the conductivity of the light-emitting diode and reducing resistance. In other embodiments, the doping concentration of each barrier layer 1412 can also increase non-uniformly from bottom to top.

[0098] Preferably, 1E18cm -3 <m<n<5E18cm -3 , where m is the doping concentration of the well layer 1411, and n is the doping concentration of the barrier layer 1412. If the doping concentrations of the well layer 1411 and the barrier layer 1412 are too high, defects in the epitaxial structure may increase, thereby reducing the brightness of the light-emitting diode. If the doping concentrations are too low, a large number of holes may not be effectively provided.

[0099] Preferably, the number of periods of the periodic alternating stacking is 2 to 20.

[0100] Preferably, the thickness of the superlattice layer 141 is 14 nm to 300 nm.

[0101] Preferably, the thickness of the barrier layer 1412 is greater than the thickness of the well layer 1411. Further preferably, the thickness of the well layer 1411 is 2 nm to 5 nm, and the thickness of the barrier layer 1412 is 5 nm to 10 nm.

[0102] Since the thickness of the barrier layer 1412 can affect the movement and energy level structure of electrons in the barrier layer 1412 material, when the thickness of the barrier layer 1412 is greater than the thickness of the well layer 1411, it can better prevent electrons in the carriers from leaking from the active layer to the second confinement layer 142 in the second semiconductor layer.

[0103] The step of forming the first semiconductor layer includes: sequentially forming a first ohmic contact layer 123 , a first buffer layer 124 , a first window layer 125 and a first confinement layer 126 stacked on the substrate 11 .

[0104] Before forming the first semiconductor layer, a bottom buffer layer 121 and an etching stop layer 122 may be formed in sequence on the substrate 11 .

[0105] When the metal organic compound chemical vapor deposition process is used to form the bottom buffer layer 121, the corrosion stop layer 122 and the first semiconductor layer, the temperature used to form the bottom buffer layer 121, the corrosion stop layer 122, the first ohmic contact layer 123, the first buffer layer 124 and the first window layer 125 is preferably 700℃~750℃, and the temperature used to form the first restriction layer 126 is preferably 750℃~800℃.

[0106] The bottom buffer layer 121 is used to eliminate the influence of the surface defects of the substrate 11 on the epitaxial layer of the light-emitting diode to the greatest extent, reduce the probability of defects and dislocations in the epitaxial layer of the light-emitting diode, and provide a flat surface for the next growth step.

[0107] The bottom buffer layer 121 can be made of, but is not limited to, GaAs. The bottom buffer layer 121 can be doped with a first-type dopant, such as an N-type dopant. Preferably, the bottom buffer layer 121 has a thickness of 200 nm to 300 nm; more preferably, the bottom buffer layer 121 has a thickness of 200 nm.

[0108] The material of the etch-stop layer 122 can be, but is not limited to, GaInP. The etch-stop layer 122 can be doped with a first-type dopant, such as an N-type dopant. Preferably, the thickness of the etch-stop layer 122 is 10 nm to 20 nm; more preferably, the thickness of the etch-stop layer 122 is 20 nm.

[0109] The material of the first ohmic contact layer 123 may be AlGaInP or GaAs, but is not limited thereto. Preferably, the thickness of the first ohmic contact layer 123 is 5 nm to 10 nm; more preferably, the thickness of the first ohmic contact layer 123 is 10 nm.

[0110] The material of the first buffer layer 124 may be GaInP, but is not limited thereto. Preferably, the thickness of the first buffer layer 124 is 15 nm to 25 nm; more preferably, the thickness of the first buffer layer 124 is 15 nm.

[0111] The functions of the first window layer 125 include current spreading, light extraction, and surface roughening.

[0112] The material of the first window layer 125 may be AlGaInP, but is not limited thereto. Preferably, the thickness of the first window layer 125 is 1500 nm to 3000 nm; more preferably, the thickness of the first window layer 125 is 2000 nm.

[0113] The first confinement layer 126 is used to provide electrons and confine the light field distribution.

[0114] The material of the first confinement layer 126 may be AlInP, but is not limited thereto. Preferably, the thickness of the first confinement layer 126 is 1200 nm to 1500 nm; more preferably, the thickness of the first confinement layer 126 is 1500 nm.

[0115] The steps of forming the active layer include: sequentially forming a first waveguide layer 131, a light-emitting layer 132, and a second waveguide layer 133 stacked on the first semiconductor layer.

[0116] When the active layer is formed by metalorganic chemical vapor deposition, the temperature preferably used for forming the first waveguide layer 131 and the second waveguide layer 133 is 750 °C to 800 °C, and the temperature preferably used for forming the light-emitting layer 132 is 700 °C to 750 °C.

[0117] The material of the first waveguide layer 131 may be (Al b Ga 1-b ) 0.5 In 0.5 P, 0 < b < 1, but is not limited thereto. Preferably, the thickness of the first waveguide layer 131 is 60 nm to 80 nm; more preferably, the thickness of the first waveguide layer 131 is 80 nm.

[0118] The light-emitting layer 132 is a multi-quantum well structure, and the light-emitting layer 132 includes periodically and alternately stacked well layers and barrier layers, and the number of alternately stacked periods is preferably 6 to 12.

[0119] The material of the potential well layer is preferably (Al p Ga 1-p ) 0.5 In 0.5 P, where 0 < p ≤ 0.5; the material of the potential barrier layer is preferably (Al q Ga 1-q ) 0.5 In 0.5 P, where 0.5 ≤ q < 1.

[0120] Preferably, the thickness of the light-emitting layer 132 is 150 nm to 480 nm, the thickness of the potential well layer is 5 nm to 10 nm, and the thickness of the potential barrier layer is 20 nm to 30 nm.

[0121] The material of the second waveguide layer 133 can be (Al w Ga 1-w ) 0.5 In 0.5 P, where 0.5 ≤ w ≤ 1, but is not limited thereto. Preferably, the thickness of the second waveguide layer 133 is 60 nm to 80 nm; more preferably, the thickness of the second waveguide layer 133 is 80 nm.

[0122] Both the first waveguide layer 131 and the second waveguide layer 133 are not doped, and the first waveguide layer 131 and the second waveguide layer 133 are respectively used to prevent the doping ions in the first semiconductor layer and the second semiconductor layer from entering the light-emitting layer 132.

[0123] The steps of forming the second semiconductor layer include: sequentially forming the superlattice layer 141, the second confinement layer 142, the transition layer 143, the second window layer 144, and the second ohmic contact layer 145 stacked on the active layer.

[0124] When the second semiconductor layer is formed by metalorganic chemical vapor deposition process, the temperature used for forming the superlattice layer 141 is preferably 700 °C to 800 °C, the temperature used for forming the second confinement layer 142 and the transition layer 143 is preferably 750 °C to 800 °C, the temperature used for forming the second window layer 144 is preferably 800 °C to 900 °C, and the temperature used for forming the second ohmic contact layer 145 is preferably 700 °C to 750 °C.

[0125] Since the superlattice layer 141 is located between the active layer and the second confinement layer 142, the superlattice layer 141 can prevent the holes in the active layer from escaping to the second confinement layer 142, thereby improving the lateral expansion of the holes. At the same time, it can block the leakage of electrons in the active layer, increase the hole injection efficiency, and improve the probability of electron and hole recombination.

[0126] The second confinement layer 142 is used to provide holes.

[0127] The material of the second confinement layer 142 may be AlInP, but is not limited thereto. Preferably, the thickness of the second confinement layer 142 is 1200 nm to 1500 nm; more preferably, the thickness of the second confinement layer 142 is 1500 nm.

[0128] The material of the transition layer 143 may be AlGaInP, but is not limited thereto. Preferably, the thickness of the transition layer 143 is 5 nm to 10 nm; more preferably, the thickness of the transition layer 143 is 10 nm.

[0129] The material of the second window layer 144 can be GaP, but is not limited thereto. Preferably, the thickness of the second window layer 144 is 3000 nm to 5000 nm; more preferably, the thickness of the second window layer 144 is 4000 nm.

[0130] The second ohmic contact layer 145 is used to form an ohmic contact with an electrode.

[0131] The material of the second ohmic contact layer 145 can be GaP, but is not limited thereto. Preferably, the thickness of the second ohmic contact layer 145 is 100 nm to 200 nm; more preferably, the thickness of the second ohmic contact layer 145 is 150 nm.

[0132] From the above content, it can be seen that in the manufacturing method of the epitaxial structure of the light-emitting diode provided by the present invention, since the doping concentration of the barrier layer 1412 is higher than the doping concentration of the well layer 1411, the well layer 1411 with a low doping concentration can prevent P-type doping ions from diffusing into the active layer, and the barrier layer 1412 with a high doping concentration can provide a large number of holes; and, the well layer 1411 with a low doping concentration is combined with the barrier layer 1412 with a high doping concentration, so that the superlattice layer 141 can block the holes from overflowing from the active layer to the second semiconductor layer while providing a large number of holes. At the same time, the well layer 1411 in the superlattice layer 141 can bind a large number of holes to form a two-dimensional hole high-density state; the barrier layer 1412 in the superlattice layer 141 can prevent the holes in the active layer from escaping to the second confinement layer 142, thereby improving the lateral expansion of the holes, effectively blocking electron leakage, increasing the hole injection efficiency, and improving the probability of electron and hole recombination, thereby improving the luminous efficiency and brightness of the light-emitting diode.

[0133] Among them, since the higher the effective barrier height, the fewer electrons can cross the barrier, and the more conducive to electron restriction, the superlattice layer 141 can reduce the effective barrier height for holes in the valence band, and at the same time, electron leakage is suppressed, so that the probability of holes and leaked electrons in the second semiconductor layer undergoing non-radiative recombination is reduced, thereby further improving the hole injection efficiency in the active layer; and the superlattice layer 141 has a higher effective barrier height for electrons, which is more conducive to electron leakage restriction, and the superlattice layer 141 has a lower effective barrier height for holes, which is more conducive to hole injection; at the same time, the superlattice layer 141 increases the hole injection efficiency, and there are enough holes and electrons in the active layer for radiative recombination, which increases the radiative recombination probability of holes and electrons in the active area, thereby improving the luminous efficiency and brightness of the light-emitting diode.

[0134] In summary, the present invention provides a method for manufacturing an epitaxial structure of a light-emitting diode, comprising: providing a substrate; sequentially forming a first semiconductor layer, an active layer, and a second semiconductor layer stacked on the substrate, wherein the first semiconductor layer and the second semiconductor layer have opposite doping types, the second semiconductor layer includes a superlattice layer, the superlattice layer is located closest to the active layer in the second semiconductor layer, the superlattice layer includes periodically alternating well layers and barrier layers, the Al composition of the barrier layers is greater than the Al composition of the well layers, the Al composition of each well layer is the same, and the Al composition of each barrier layer increases from bottom to top; the doping concentration of the barrier layer is higher than the doping concentration of the well layer, the doping concentration of each well layer is the same, and the doping concentration of each barrier layer increases from bottom to top. The present invention enables improving the luminous efficiency and brightness of light-emitting diodes.

[0135] The above description is only a description of the preferred embodiments of the present invention and does not limit the scope of the present invention. Any changes and modifications made by ordinary technicians in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. An epitaxial structure of a light emitting diode, characterized in that: The present invention comprises a substrate, a first semiconductor layer, an active layer and a second semiconductor layer from bottom to top, wherein the doping types of the first semiconductor layer and the second semiconductor layer are opposite, the second semiconductor layer comprises a superlattice layer, the superlattice layer is located at a position closest to the active layer in the second semiconductor layer, the superlattice layer comprises well layers and barrier layers that are periodically and alternately stacked, the Al composition of the barrier layer is greater than the Al composition of the well layer, the Al composition of each well layer is the same, and the Al composition of each barrier layer increases layer by layer from bottom to top; the doping concentration of the barrier layer is higher than the doping concentration of the well layer, the doping concentration of each well layer is the same, and the doping concentration of each barrier layer increases layer by layer from bottom to top.

2. The epitaxial structure of a light emitting diode according to claim 1, wherein: The material of the well layer is (Al x Ga 1-x ) 0.5 In 0.5 P, the material of the barrier layer is (Al y Ga 1-y ) 0.5 In 0.5 P, 0 <x<y<1。 3. The epitaxial structure of a light emitting diode according to claim 1, wherein: The Al composition of each layer of the barrier layer increases from bottom to top layer by layer △y=(y max -y min ) / (k-1), where y max is the Al component of the topmost barrier layer, y min is the Al composition of the bottommost barrier layer, and k is the number of periods of the periodic alternating stacking.

4. The epitaxial structure of a light emitting diode according to claim 1, wherein: The doping concentration of each barrier layer increases from bottom to top layer by layer △n=(n max -n min ) / (k-1), where n max is the doping concentration of the topmost barrier layer, n min is the doping concentration of the bottom barrier layer, and k is the number of periods of the periodic alternating stacking.

5. The epitaxial structure of a light emitting diode according to claim 1, wherein: 1E18cm -3 <m<n<5E18cm -3 , where m is the doping concentration of the well layer, and n is the doping concentration of the barrier layer.

6. The epitaxial structure of a light emitting diode according to claim 1, wherein: The number of periods of the periodic alternating stacking is 2 to 20.

7. The epitaxial structure of a light emitting diode according to claim 1, wherein: The thickness of the superlattice layer is 14 nm to 300 nm, the thickness of the well layer is 2 nm to 5 nm, and the thickness of the barrier layer is 5 nm to 10 nm.

8. The epitaxial structure of a light emitting diode according to claim 1, wherein: The thickness of the barrier layer is greater than the thickness of the well layer.

9. The epitaxial structure of a light emitting diode according to claim 1, wherein: The first semiconductor layer includes, from bottom to top, a first ohmic contact layer, a first buffer layer, a first window layer, and a first confinement layer; the second semiconductor layer also includes, from bottom to top, a second confinement layer, a transition layer, a second window layer, and a second ohmic contact layer, and the superlattice layer is located between the active layer and the second confinement layer.

10. A method for manufacturing an epitaxial structure of a light emitting diode, characterized in that: include: providing a substrate; A first semiconductor layer, an active layer, and a second semiconductor layer are sequentially stacked on the substrate, wherein the first semiconductor layer and the second semiconductor layer have opposite doping types, the second semiconductor layer includes a superlattice layer, the superlattice layer is located at a position closest to the active layer in the second semiconductor layer, the superlattice layer includes periodically alternating well layers and barrier layers, the Al composition of the barrier layer is greater than the Al composition of the well layer, the Al composition of each well layer is the same, and the Al composition of each barrier layer increases layer by layer from bottom to top; the doping concentration of the barrier layer is higher than the doping concentration of the well layer, the doping concentration of each well layer is the same, and the doping concentration of each barrier layer increases layer by layer from bottom to top.

11. The method for manufacturing an epitaxial structure of a light emitting diode according to claim 10, wherein: The material of the well layer is (Al x Ga 1-x ) 0.5 In 0.5 P, the material of the barrier layer is (Al y Ga 1-y ) 0.5 In 0.5 P, 0 <x<y<1。 12. The method for manufacturing an epitaxial structure of a light emitting diode according to claim 10, wherein: The Al composition of each layer of the barrier layer increases from bottom to top layer by layer △y=(y max -y min ) / (k-1), where y max is the Al component of the topmost barrier layer, y min is the Al composition of the bottommost barrier layer, and k is the number of periods of the periodic alternating stacking.

13. The method for manufacturing an epitaxial structure of a light emitting diode according to claim 10, wherein: The doping concentration of each barrier layer increases from bottom to top layer by layer △n=(n max -n min ) / (k-1), where n max is the doping concentration of the topmost barrier layer, n min is the doping concentration of the bottom barrier layer, and k is the number of periods of the periodic alternating stacking.

14. The method for manufacturing an epitaxial structure of a light emitting diode according to claim 10, wherein: 1E18cm -3 <m<n<5E18cm -3 , where m is the doping concentration of the well layer, and n is the doping concentration of the barrier layer.

15. The method for manufacturing an epitaxial structure of a light emitting diode according to claim 10, wherein: The number of periods of the periodic alternating stacking is 2 to 20.

16. The method for manufacturing an epitaxial structure of a light emitting diode according to claim 10, wherein: The thickness of the superlattice layer is 14 nm to 300 nm, the thickness of the well layer is 2 nm to 5 nm, and the thickness of the barrier layer is 5 nm to 10 nm.

17. The method for manufacturing an epitaxial structure of a light emitting diode according to claim 10, wherein: The thickness of the barrier layer is greater than the thickness of the well layer.

18. The method for manufacturing an epitaxial structure of a light emitting diode according to claim 10, wherein: The first semiconductor layer includes, from bottom to top, a first ohmic contact layer, a first buffer layer, a first window layer, and a first confinement layer; the second semiconductor layer also includes, from bottom to top, a second confinement layer, a transition layer, a second window layer, and a second ohmic contact layer, and the superlattice layer is located between the active layer and the second confinement layer.

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