CN115763654A

CN115763654A - Epitaxial structure of light emitting diode and preparation method thereof

Info

Publication number: CN115763654A
Application number: CN202211403249.8A
Authority: CN
Inventors: 赖玉财; 李森林; 毕京锋; 王亚宏; 廖寅生; 薛龙; 谢岚驰
Original assignee: Xiamen Silan Advanced Compound Semiconductor Co Ltd
Current assignee: Xiamen Silan Advanced Compound Semiconductor Co Ltd
Priority date: 2022-11-10
Filing date: 2022-11-10
Publication date: 2023-03-07

Abstract

Disclosed are an epitaxial structure of a light emitting diode and a method for manufacturing the same, the epitaxial structure of the light emitting diode includes: a substrate; the first semiconductor layer is positioned on the substrate and is of a first doping type; an active layer on the first semiconductor layer; a second semiconductor layer on the active layer, the second semiconductor layer being of a second doping type opposite to the first doping type; the active layer comprises a first quantum well layer, a barrier layer and a second quantum well layer which are sequentially stacked from bottom to top, and the first quantum well layer is located on the first semiconductor layer. According to the epitaxial structure of the light emitting diode and the preparation method thereof, the barrier layer is arranged in the active layer to block holes and the movement of electrons, and the electrons and the holes are mainly limited in the active layer, so that the electrons and the holes are combined to emit light in the active layer, and the brightness of the light emitting diode is ensured.

Description

Epitaxial structure of light emitting diode and preparation method thereof

Technical Field

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

Background

Light Emitting Diodes (LEDs) made of compound semiconductors were introduced in the early 60's of the last year, and their power consumption was significantly reduced compared to incandescent lamps, e.g. one LED indicator lamp used only 2% of the power used by an incandescent light bulb. Because of the significant reduction of the power consumption of the light emitting diode, the light emitting diode has replaced incandescent lamps, is applied to electronic instruments and electrical equipment in various industries of national economy, and enters various household appliances used by people in families.

The AlGalnP ultra-high brightness LED has monochromaticity, and does not need an additional optical filter unlike an incandescent lamp. The yellow light emitting diode is generally applied to the fields of traffic lights, marker lights, automobile warning lights and the like, and has more strict requirements on reliability.

Since the band gap of the yellow light emitting diode is close to the indirect band gap, a higher Al element needs to be introduced into the epitaxial structure, and the Al element is easily oxidized, so that the limiting capability of electron-hole pairs is reduced, and the yellow light emitting diode fails, so that the development of a highly reliable yellow light emitting diode has a great challenge.

Disclosure of Invention

In view of the above problems, an object of the present invention is to provide an epitaxial structure of a light emitting diode and a method for fabricating the same, so as to improve the brightness and reliability of the light emitting diode.

A first aspect of the present invention provides an epitaxial structure of a light emitting diode, including:

a substrate;

the first semiconductor layer is positioned on the substrate and is of a first doping type;

an active layer on the first semiconductor layer;

a second semiconductor layer on the active layer, the second semiconductor layer being of a second doping type opposite to the first doping type;

the active layer comprises a first quantum well layer, a barrier layer and a second quantum well layer which are sequentially stacked from bottom to top, and the first quantum well layer is located on the first semiconductor layer.

Preferably, the active layer is an AlGaInP material layer.

Preferably, the first quantum well layer includes a plurality of periods of first barrier layers and first well layers, the first barrier layers and the first well layers being alternately arranged; the second quantum well layer comprises a plurality of periods of second barrier layers and second well layers, and the second barrier layers and the second well layers are alternately arranged.

Preferably, when the first semiconductor layer is an N-type semiconductor layer, the composition of Al in the plurality of first barrier layers decreases in sequence from the first semiconductor layer to the second semiconductor layer; when the first semiconductor layer is a P-type semiconductor layer, from the second semiconductor layer to the first semiconductor layer, the Al components in the multiple first barrier layers are sequentially reduced, or the Al components in the multiple first barrier layers are reduced and then increased.

Preferably, the material of the first barrier layer is (Al) _x1 Ga _1-x1 ) _0.25 In _0.25 P _0.5 X1 is more than or equal to 0.5 and less than or equal to 0.9; the material of the first well layer is (Al) _y1 Ga _1-y1 ) _0.25 In _0.25 P _0.5 ，0.1≤y1≤0.4。

Preferably, when the first semiconductor layer is an N-type semiconductor layer, in a direction from the first semiconductor layer to the second semiconductor layer, the Al components in the multiple second barrier layers sequentially decrease, or the Al components in the multiple second barrier layers decrease and then increase; when the first semiconductor layer is a P-type semiconductor layer, the Al components in the plurality of second barrier layers are sequentially reduced from the second semiconductor layer to the first semiconductor layer.

Preferably, the material of the second barrier layer is (Al) _x2 Ga _1-x2 ) _0.25 In _0.25 P _0.5 X2 is more than or equal to 0.5 and less than or equal to 0.9; the material of the second well layer is (Al) _y2 Ga _1-y2 ) _0.25 In _0.25 P _0.5 ，0.1≤y2≤0.4。

Preferably, the number of cycles of the first quantum well layer and the second quantum well layer is the same or different; the number of cycles of the first quantum well layer is 10-30; the number of cycles of the second quantum well layer is 10 to 30.

Preferably, the material of the barrier layer is (Al) _xp Ga _1-xp ) _0.25 In _0.25 P _0.5 。

Preferably, the composition of Al in the barrier layer is greater than or equal to the composition of Al in any first barrier layer in the first quantum well layer; and the composition of Al in the barrier layer is more than or equal to that of Al in any second barrier layer in the second quantum well layer.

Preferably, the first semiconductor layer includes a first ohmic contact layer, a first window layer, a first confinement layer and a first barrier layer, which are stacked in sequence, wherein the first ohmic contact layer is located on the substrate;

the second semiconductor layer comprises a second barrier layer, a second limiting layer, a second current spreading layer and a second ohmic contact layer which are sequentially stacked, wherein the second barrier layer is located on the active layer.

Preferably, the first barrier layer and the second barrier layer are made of the same material and are both (Al) _z Ga _1-z ) _0.25 In _0.25 P _0.5 。

Preferably, the composition of Al in each of the first barrier layer and the second barrier layer is greater than or equal to the composition of Al in any one of the first barrier layers in the first quantum well layer, and the composition of Al in each of the first barrier layer and the second barrier layer is greater than or equal to the composition of Al in any one of the second barrier layers in the second quantum well layer.

Preferably, the thickness of the barrier layer is greater than that of any first barrier layer in the first quantum well layer; the thickness of the barrier layer is larger than that of any second barrier layer in the second quantum well layer.

Preferably, the thickness of the active layer is 380nm to 1040nm, the thickness of the first quantum well layer is 140nm to 420nm, the thickness of the barrier layer is 100nm to 200nm, and the thickness of the second quantum well layer is 140nm to 420nm.

The second aspect of the present invention provides a method for preparing an epitaxial structure of a light emitting diode, including:

providing a substrate;

forming a first semiconductor layer on the substrate, wherein the first semiconductor layer is of a first doping type;

forming an active layer on the first semiconductor layer;

forming a second semiconductor layer on the active layer, the second semiconductor layer being of a second doping type opposite to the first doping type;

the active layer is formed by sequentially forming a first quantum well layer, a barrier layer and a second quantum well layer from bottom to top, and the first quantum well layer is located on the first semiconductor layer.

Preferably, the active layer is an AlGaInP material layer.

Preferably, the first quantum well layer includes a plurality of periods of first barrier layers and first well layers, the first barrier layers and the first well layers being alternately arranged; the second quantum well layer includes a plurality of periods of second barrier layers and second well layers, and the second barrier layers and the second well layers are alternately arranged.

Preferably, when the first semiconductor layer is an N-type semiconductor layer, the composition of Al in the plurality of first barrier layers decreases in sequence from the first semiconductor layer to the second semiconductor layer; when the first semiconductor layer is a P-type semiconductor layer, the Al components in the multiple layers of the first barrier layer are sequentially reduced in the direction from the second semiconductor layer to the first semiconductor layer, or the Al components in the multiple layers of the first barrier layer are reduced and then increased.

Preferably, the composition of Al in the barrier layer is greater than or equal to that of Al in any first barrier layer in the first quantum well layer; and the composition of Al in the barrier layer is more than or equal to that of Al in any second barrier layer in the second quantum well layer.

Preferably, the forming of the first semiconductor layer includes forming a first ohmic contact layer, a first window layer, a first confinement layer and a first barrier layer, which are sequentially stacked, wherein the first ohmic contact layer is located on the substrate;

forming the second semiconductor layer includes forming a second blocking layer, a second confinement layer, a second current spreading layer, and a second ohmic contact layer, which are sequentially stacked, wherein the second blocking layer is on the active layer.

According to the epitaxial structure of the light emitting diode and the preparation method thereof, provided by the invention, the barrier layer is arranged in the active layer to block the movement of the holes and the electrons, and the electrons and the holes are mainly limited in the active layer, so that the electrons and the holes are compounded in the active layer to emit light, and the brightness of the light emitting diode is ensured.

In a preferred embodiment, the first barrier layer in the first quantum well layer and the second barrier layer in the second quantum well layer both adopt a graded structure, and overall, the potential barriers in the first quantum well layer and the second quantum well layer gradually increase from the P-type semiconductor layer to the N-type semiconductor layer, so that the holes are more difficult to pass closer to the N-type semiconductor layer, the phenomenon that the holes are easy to accumulate towards one side of the N-type semiconductor layer and then leak due to the bending of the energy band is weakened, and the effect of lifting the energy band at one side of the N-type semiconductor layer to a certain extent is also achieved to weaken the bending of the energy band, reduce the leakage of electrons and holes towards the outside of the active layer, and improve the reliability of the light emitting diode.

In a preferred embodiment, the thickness of the barrier layer is greater than the thickness of any one of the first barrier layers in the first quantum well layer and the thickness of any one of the second barrier layers in the second quantum well layer, so that the reliability of the barrier effect of the barrier layer is improved.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

FIG. 1 shows a band diagram of an intrinsic semiconductor energy band;

fig. 2 shows an equivalent structural schematic diagram of an epitaxial structure of a light emitting diode;

figure 3a shows an energy band diagram of a homojunction epitaxial structure;

figure 3b shows an energy band diagram of a heterojunction epitaxial structure;

fig. 4 shows a schematic view of an epitaxial structure of a light emitting diode of an embodiment of the invention;

FIG. 5 shows a band diagram of an epitaxial structure of a light emitting diode according to a specific embodiment of the present invention;

fig. 6a to 6d are sectional views showing stages in the process of manufacturing an epitaxial structure of a light emitting diode according to an embodiment of the present invention.

Detailed Description

The invention will be described in more detail below with reference to the accompanying drawings. Like elements are denoted by like reference numerals throughout the various figures. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale. Moreover, certain well-known elements may not be shown.

The present invention may be embodied in various forms, some examples of which are described below.

Fig. 1 shows an intrinsic semiconductor energy band diagram, and as shown in fig. 1, extra-nuclear electrons of a substance have different energies according to the solid band theory. The energy level of each electron in an atom is split into energy bands in a solid, and the energy bands are divided into three energy bands according to the difference of the energy levels of the electrons outside a nucleus: conduction band, forbidden band, and valence band. Where the conduction and valence bands are allowed to be occupied by electrons, called the allowed bands. The range between the allowed bands does not allow electrons to occupy, and this range is called a forbidden band.

Fig. 2 is a schematic view showing an equivalent structure of an epitaxial structure of a light emitting diode including an N-type semiconductor layer, an active layer, and a P-type semiconductor layer, wherein the N-type semiconductor layer provides electrons to the active layer, and the P-type semiconductor layer provides holes to the active layer; electrons provided by the N-type semiconductor layer and holes provided by the P-type semiconductor layer are radiated and recombined in the active layer, so that light is emitted.

Figure 3a shows a band diagram of a homojunction epitaxial structure; figure 3b shows an energy band diagram of a heterojunction epitaxial structure; as shown in fig. 3a and 3b, in the homojunction epitaxial structure, the N-type semiconductor layer and the P-type semiconductor layer on both sides of the active layer are made of the same material, the energy bands of the N-type semiconductor layer and the P-type semiconductor layer on both sides of the active layer are balanced, and electrons provided by the N-type semiconductor layer and holes provided by the P-type semiconductor layer are radiatively recombined in the active layer.

In the heterojunction epitaxial structure, the materials of the N-type semiconductor layer and the P-type semiconductor layer on two sides of the active layer are different, and the energy band is bent due to the difference of the materials on two sides of the active layer. Because the conduction band on one side of the N-type semiconductor layer is lower, a large number of holes are easy to leak after being accumulated on the N-type semiconductor layer, and the photoelectric performance of the light-emitting diode is greatly reduced.

Fig. 4 shows a schematic diagram of an epitaxial structure of a light emitting diode according to an embodiment of the present invention, where the epitaxial structure of the light emitting diode includes a substrate 110 and an epitaxial layer located on the substrate 110, and the epitaxial layer includes, from bottom to top, a buffer layer 121, an etch stop layer 122, a first semiconductor layer 123, an active layer 124, and a second semiconductor layer 125.

In this embodiment, the substrate 110 is, for example, a gallium arsenide (GaAs) substrate. In other embodiments, the substrate 110 may be any one of semiconductor substrates such as a silicon (Si) substrate, which is not limited in this embodiment.

The epitaxial layer sequentially includes a buffer layer 121, an etch stop layer 122, a first semiconductor layer 123, an active layer 124, and a second semiconductor layer 125 from bottom to top. The buffer layer 121 and the etch stop layer 122 may be removed by wet etching or dry etching in the subsequent manufacturing process of the led. The first semiconductor layer 123 has a first doping type, and the second semiconductor layer 125 has a second doping type. Wherein the first doping type is one of an N-type and a P-type, and the second doping type is the other of the N-type and the P-type. In this embodiment, the first doping type is, for example, N-type doping, and the second doping type is, for example, P-type doping.

The buffer layer 121 is disposed on the substrate 110, and in the embodiment, the buffer layer 121 has a first doping type, such as a silicon (Si) -doped gallium arsenide (GaAs) material layer, but is not limited thereto. The buffer layer 121 has a thickness of 200nm to 500nm, for example, 300nm. The buffer layer 121 is grown on the substrate 110, so that the influence of surface defects of the substrate 110 on the epitaxial layer can be eliminated to the maximum extent, defects and dislocation of the epitaxial layer are prevented, and a flat interface is provided for the next growth.

The etch stop layer 122 is disposed on the buffer layer 121, and in the present embodiment, the etch stop layer 122 has a first doping type, such as a silicon (Si) -doped GaInP material layer, but is not limited thereto. In other embodiments, the etch stop layer 122 may be doped with other N-type dopants, such as tellurium (Te), and the like, which is not limited in the embodiments of the invention. The thickness of the etch stop layer 122 is 100nm to 300nm, for example, 150nm.

The first semiconductor layer 123 sequentially includes a first ohmic contact layer 1231, a first window layer 1232, a first confinement layer 1233, and a first barrier layer 1234 from bottom to top, wherein the first ohmic contact layer 1231 is located on the etch stop layer 122.

In this embodiment, the first ohmic contact layer 1231 is, for example, a silicon (Si) -doped GaAs material layer or an AlGaInP material layer, and has a thickness of, for example, 50nm to 200nm; the first window layer 1232 is, for example, a silicon (Si) -doped AlGaInP material layer, and has a thickness of, for example, 2um to 6um; the first confinement layer 1233 is, for example, a layer of silicon (Si) -doped AlInP material, and has a thickness of, for example, 200nm to 600nm; the first barrier layer 1234 may be, for example, an AlGaInP material layer, and has a thickness of, for example, 50nm to 200nm. In other embodiments, the first semiconductor layer 123 may be doped with other N-type dopants, such as tellurium (Te), and the like, which is not limited in the embodiments of the invention.

The active layer 124 includes a first quantum well layer 1241, a barrier layer 1242, and a second quantum well layer 1243, which are sequentially stacked. The first quantum well layer 1241 is located on the first semiconductor layer 123 (specifically, on the first barrier layer 1234). The first quantum well layer 1241 includes a plurality of periods of first barrier layers and first well layers, where the first barrier layers and the first well layers are alternately arranged. The second quantum well layer 1243 includes a plurality of periods of second barrier layers and second well layers, where the second barrier layers and the second well layers are alternately arranged. The number of periods of the first quantum well layer 1241 and the second quantum well layer 1242 may be the same or different. In this embodiment, the number of cycles of the first quantum well layer 1241 is, for example, 10 to 30, and preferably 20. The number of periods of the second quantum well layer 1242 is, for example, 10 to 30, and preferably 20.

When the first semiconductor layer is an N-type semiconductor layer and the second semiconductor layer is a P-type semiconductor layer, the material of the first quantum well layer 1241 is, for example, alGaInP. The material of the first barrier layer is, for example, (Al) _x1 Ga _1-x1 ) _0.25 In _0.25 P _0.5 Wherein x1 is more than or equal to 0.5 and less than or equal to 0.9. The composition of Al in the first barrier layer decreases from layer to layer in the direction from the first semiconductor layer 123 to the second semiconductor layer 125. Specifically, in the direction from the first semiconductor layer 123 to the second semiconductor layer 125, the composition of Al in each first barrier layer is x11, x12 … … x1n in sequence, and decreases from x11 to x1n in sequence, wherein 10 ≦ 1n ≦ 30, x11 is 0.8 for example, and x1n is 0.5 for example. Further, the difference in Al composition between each adjacent two layers may be the same or different, preferably the same, from x11 to x1 n. The material of the first well layer is (Al) _y1 Ga _1-y1 ) _0.25 In _0.25 P _0.5 0.1. Ltoreq. Y1. Ltoreq.0.4, preferably, y1=0.2. The thickness of the first barrier layer of each layer can be the same or different, for example, can be monotonically increased or monotonically decreased, and is preferably the same; the thicknesses of the first well layers may be the same or different, and may be, for example, monotonically increasing or monotonically decreasing, and are preferably the same.

The material of the barrier layer 1242 is, for example, (Al) _xp Ga _1-xp ) _0.25 In _0.25 P _0.5 Preferably, xp =0.8. The thickness of the barrier layer 1242 is, for example, 100nm to 200nm, preferably 150nm.

The material of the second quantum well layer 1243 is, for example, alGaInP, and the material of the second barrier layer is, for example, (Al) _x2 Ga _1-x2 ) _0.25 In _0.25 P _0.5 Wherein x2 is more than or equal to 0.5 and less than or equal to 0.9. The composition of Al in the second barrier layer decreases from layer to layer in the direction from the first semiconductor layer 123 to the second semiconductor layer 125. Specifically, in the direction from the first semiconductor layer 123 to the second semiconductor layer 125, the composition of Al in each second barrier layer is x21, x22 … … x2n in sequence, and decreases in sequence from x21 to x2 n. Wherein 10. Ltoreq.2n. Ltoreq.30, x21 is, for example, 0.8, and x2n is, for example, 0.5. Further, the difference in Al composition between each adjacent two layers may be the same or different, preferably the same, from x21 to x2 n. The material of the second well layer is (Al) _y2 Ga _1-y2 ) _0.25 In _0.25 P _0.5 0.1. Ltoreq. Y2. Ltoreq.0.4, preferably, y2=0.2. In other embodiments, the composition of Al in the second barrier layer may also decrease from layer to layer and then increase from layer to layer. The thickness of each second barrier layer can be the same or different, for example, can be monotonically increased or monotonically decreased, and is preferably the same; the thicknesses of the second well layers may be the same or different, and may be, for example, monotonically increasing or monotonically decreasing, and are preferably the same.

In this embodiment, the materials of the first quantum well layer 1241 and the second quantum well layer 1243 are the same, that is, x1 is decreased from 0.8 to 0.5 layer by layer, and x2 is also decreased from 0.8 to 0.5 layer by layer, in other embodiments, the materials of the first quantum well layer 1241 and the second quantum well layer 1243 may also be different, that is, x1 may be decreased from 0.9 to 0.7 layer by layer, for example, x2 may be decreased from 0.7 to 0.5 layer by layer, for example, and the present embodiment does not limit this.

By setting the composition of Al in different first barrier layers, the first quantum well layer 1241 has a higher potential barrier on the side close to the first semiconductor layer 123 and has a lower potential barrier on the side far from the first semiconductor layer 123. Similarly, by setting the composition of Al in different second barrier layers, the second quantum well layer 1243 has a higher potential barrier on the side close to the first semiconductor layer 123 and has a lower potential barrier on the side far from the first semiconductor layer 123.

It is to be noted that, when the first semiconductor layer is a P-type semiconductor layer and the second semiconductor layer is an N-type semiconductor layer, the Al composition in the first barrier layer increases or decreases first and then increases in the direction from the first semiconductor layer 123 to the second semiconductor layer 125, and the Al composition in the second barrier layer increases in the direction from the first semiconductor layer 123 to the second semiconductor layer 125.

The composition of Al in the barrier layer 1242 is greater than or equal to that of Al in any one of the first quantum well layers 1241, and meanwhile, the composition of Al in the barrier layer 1242 is greater than or equal to that of Al in any one of the second barrier layers in the second quantum well layer 1243, namely xp is greater than or equal to x1 and xp is greater than or equal to x2. The number of cycles of the first quantum well layer 1241 and the number of cycles of the second quantum well layer 1243 may be the same or different, and preferably are the same.

Further, the thickness of the blocking barrier layer 1242 is greater than the thickness of any first barrier layer in the first quantum well layer 1241 and the thickness of any second barrier layer in the second quantum well layer 1243, so that the reliability of the blocking effect of the blocking barrier layer 1242 is improved. In this embodiment, the total thickness of the active layer 124 is, for example, 380nm to 1040nm, the thickness of the first quantum well layer 1241 is, for example, 140nm to 420nm, the thickness of the barrier layer 1242 is, for example, 100nm to 200nm, and the thickness of the second quantum well layer 1243 is, for example, 140nm to 420nm.

The second semiconductor layer 125 sequentially includes, from bottom to top, a second barrier layer 1251, a second confinement layer 1252, a second current spreading layer 1253, and a second ohmic contact layer 1254, where the second barrier layer 1251 is located on the active layer 124 (specifically, on the second quantum well layer 1243). In this embodiment, the second blocking layer 1251 is, for example, an AlGaInP material layer, and the thickness is, for example, 100nm to 400nm; the second confinement layer 1252 is, for example, a layer of magnesium (Mg) -doped AlInP material, for example, 200nm to 600nm thick; the second current spreading layer 1253 is, for example, a magnesium (Mg) doped GaP material layer, and has a thickness of, for example, 500nm to 1500nm; the second ohmic contact layer 1254 is, for example, a carbon (C) -doped GaP material layer with a thickness of, for example, 100nm to 300nm.

Preferably, the first barrier layer 1234 and the second barrier layer 1251 are the same material, e.g., (Al) _z Ga _1-z ) _0.25 In _0.25 P _0.5 Wherein x1 is less than or equal to z<1, and x2 is less than or equal to z<1. The thicknesses of the first barrier layer 1234 and the second barrier layer 1251 may be the same or different.

In this embodiment, the first semiconductor layer 123 and the second semiconductor layer 125 on both sides of the active layer 124 form a heterojunction, and the energy bands on both sides of the active layer are bent, specifically, the first barrier layer and the second barrier layer in the active layer both adopt a gradient structure, and the potential barrier on one side of the N-type semiconductor layer is higher than the potential barrier on one side of the P-type semiconductor layer as a whole, so that it is more difficult for holes to pass through the side closer to the N-type semiconductor layer, which reduces the phenomenon that the holes are easy to accumulate on one side of the N-type semiconductor layer due to the bending of the energy bands and then leak out, and also plays a certain role of raising the energy band on one side of the N-type semiconductor layer to reduce the bending of the energy bands, reduce the leakage of electrons and holes out of the active layer, and improve the reliability of the light emitting diode.

However, if the barrier layer in the entire active layer adopts a continuously graded structure, the barrier on one side of the P-type semiconductor layer is low, which may cause the result that electrons are easily leaked to one side of the P-type semiconductor layer, therefore, in this embodiment, the blocking barrier layer 1242 is disposed in the active layer 124, the blocking barrier layer 1242 blocks the movement of the holes and the electrons, the electrons and the holes are mainly limited in the quantum well layer between the N-type semiconductor layer and the blocking barrier layer 1242, and light is compositely emitted in the quantum well layer to ensure the brightness of the light emitting diode.

Fig. 5 shows an energy band diagram of an epitaxial structure of a light emitting diode of a specific embodiment of the present invention, in which x11=0.8 and x1n =0.5; y1=0.2; x21=0.8, x2n =0.5; y2=0.2; xp is more than or equal to x11 and xp is more than or equal to x21,xp =0.8. That is, the first barrier layer on the side close to the first semiconductor layer 123 is (Al) _0.8 Ga _0.2 ) _0.25 In _0.25 P _0.5 (ii) a The first barrier layer adjacent to the barrier layer 1242 is (Al) _0.5 Ga _0.5 ) _0.25 In _0.25 P _0.5 . Barrier layer 1242 is (Al) _0.8 Ga _0.2 ) _0.25 In _0.25 P _0.5 . The second barrier layer adjacent to the barrier layer 1242 is (Al) _0.8 Ga _0.2 ) _0.25 In _0.25 P _0.5 (ii) a The second barrier layer adjacent to the second semiconductor layer 125 is (Al) _0.5 Ga _0.5 ) _0.25 In _0.25 P _0.5 。

As shown in fig. 5, the Al composition in the first barrier layer in the first quantum well layer 1241 adopts a graded structure, and as a whole, the potential barrier in the first quantum well layer 1241 gradually increases in the direction from the second semiconductor layer 125 (P-type semiconductor layer) to the first semiconductor layer 123 (N-type semiconductor layer), and it is more difficult for holes to pass as they approach the first semiconductor layer 123 (N-type semiconductor layer), so that the phenomenon that the holes are likely to accumulate on the first semiconductor layer 123 (N-type semiconductor layer) side and then leak due to band bending is reduced, and the effect of raising the energy band on the first semiconductor layer 123 (N-type semiconductor layer) side to reduce band bending is also achieved, thereby reducing leakage of electrons and holes to the outside of the active layer 124, and improving the reliability of the light emitting diode.

Similarly, the Al component in the second barrier layer in the second quantum well layer 1243 adopts a graded structure, and as a whole, the potential barrier in the second quantum well layer 1241 gradually increases in the direction from the second semiconductor layer 125 (P-type semiconductor layer) to the first semiconductor layer 123 (N-type semiconductor layer), and the holes are more difficult to pass as they approach the first semiconductor layer 123 (N-type semiconductor layer), so that the phenomenon that the holes are easy to accumulate on the first semiconductor layer 123 (N-type semiconductor layer) side and then leak due to band bending is reduced, and a certain effect of raising the energy band on the first semiconductor layer 123 (N-type semiconductor layer) side is also achieved to reduce the band bending, reduce the leakage of electrons and holes to the outside of the active layer 124, and improve the reliability of the light emitting diode.

As shown in fig. 6a, a substrate 110 is provided.

In this embodiment, the substrate 110 is, for example, a gallium arsenide (GaAs) substrate. In other embodiments, the substrate 110 may be any semiconductor substrate such as a silicon (Si) substrate, which is not limited in this embodiment.

As shown in fig. 6b, a buffer layer 121, an etch stop layer 122, and a first semiconductor layer 123 are sequentially grown on the substrate 110.

In this step, for example, the buffer layer 121, the etch stop layer 122, and the first semiconductor layer 123 are sequentially grown on the surface of the substrate 110 by using any one or more of a Metal Organic Chemical Vapor Deposition (MOCVD) process, a Molecular Beam Epitaxy (MBE) process, and an ultra-high vacuum chemical vapor deposition (UHVCVD) process.

In this embodiment, the buffer layer 121 is a silicon (Si) -doped gallium arsenide (GaAs) material layer with a thickness of 200nm to 500nm, for example, 300nm. The etch stop layer 122 is a layer of silicon (Si) -doped GaInP material with a thickness of 100nm to 300nm, for example 150nm. In other embodiments, the buffer layer 121 and the etch stop layer 122 may be doped with other N-type dopants, such as tellurium (Te), and the like, which is not limited in the embodiments of the invention.

The buffer layer 121 is grown on the substrate 110 in this embodiment, so that the influence of the surface defects of the substrate 110 on the epitaxial layer can be eliminated to the maximum extent, the epitaxial layer is prevented from generating defects and dislocations, and a flat interface is provided for the next growth.

The first semiconductor layer 123 sequentially includes, from bottom to top, a first ohmic contact layer 1231, a first window layer 1232, a first confinement layer 1233, and a first blocking layer 1234.

In this embodiment, the first semiconductor layer 123 is, for example, an N-type semiconductor layer. Specifically, the first ohmic contact layer 1231 is, for example, a silicon (Si) -doped GaAs material layer or an AlGaInP material layer having a thickness of 50nm to 200nm (for example, 120 nm); the first window layer 1232 is, for example, a silicon (Si) -doped AlGaInP material layer with a thickness of 2um to 6um (e.g., 2.5 μm); the first confinement layer 1233 is, for example, a layer of silicon (Si) -doped AlInP material with a thickness of 200nm to 600nm (e.g., 400 nm); the first barrier layer 1234 may be, for example, an AlGaInP material layer with a thickness of 50nm to 200nm (e.g., 100 nm).

As shown in fig. 6c, an active layer 124 is grown on the first semiconductor layer 123.

The active layer 124 includes a first quantum well layer 1241, a barrier layer 1242, and a second quantum well layer 1243 stacked.

In this step, the active layer 124 is grown on the first semiconductor layer 123 (specifically, the first barrier layer 1234) using, for example, any one or more of a Metal Organic Chemical Vapor Deposition (MOCVD) process, a Molecular Beam Epitaxy (MBE) process, and an ultra-high vacuum chemical vapor deposition (UHVCVD) process.

The first quantum well layer 1241 includes first barrier layers and first well layers which are alternately arranged, and the cycle number of the first quantum well layer 1241 is 10 to 30. In a specific embodiment, the number of periods of the first quantum well layer 1241 is, for example, 20.

The material of the first quantum well layer 1241 is, for example, alGaInP, and the thickness is, for example, 140nm to 420nm. Wherein the material of the first barrier layer is (Al), for example _x1 Ga _1-x1 ) _0.25 In _0.25 P _0.5 X1 is more than or equal to 0.5 and less than or equal to 0.9. From growth to completion, the Al component in the first barrier layer decreases layer by layer. Specifically, from growth to completion, the Al components in each first barrier layer are x11 and x12 … … x1n in sequence, wherein n is more than or equal to 10 and less than or equal to 1 and less than or equal to 30, and x1 to xn are reduced in sequence. The material of the first well layer is (Al) _y1 Ga _1-y1 ) _0.25 In _0.25 P _0.5 Y1 is more than or equal to 0.1 and less than or equal to 0.4. The thickness of the first barrier layer of each layer can be the same or different, for example, can be monotonically increased or monotonically decreased, and is preferably the same; the thicknesses of the first well layers may be the same or different, and may be, for example, monotonically increasing or monotonically decreasing, and are preferably the same.

Next, a barrier layer 1242 is grown on the first quantum well layer 1241. The material of the barrier layer 1242 is, for example, (Al) _xp Ga _1-xp ) _0.25 In _0.25 P _0.5 (ii) a The thickness is from 100nm to 200nm, for example 150nm.

Next, a second quantum well layer 1243 is grown on the barrier layer 1242. The second quantum well layer 1243 includes second barrier layers and second well layers alternately arranged, the number of cycles of the second quantum well layer 1243 is, for example, 10 to 30, and the number of cycles of the first quantum well layer 1241 and the second quantum well layer 1242 may be the same or different. In a specific embodiment, the number of periods of the first quantum well layer 1241 is the same as the number of periods of the first quantum well layer 1243, for example 20.

The material of the second quantum well layer 1243 is, for example, alGaInP, and the thickness is, for example, 140nm to 420nm. Wherein the material of the second barrier layer is (Al), for example _x2 Ga _1-x2 ) _0.25 In _0.25 P _0.5 Wherein x2 is more than or equal to 0.5 and less than or equal to 0.9. The composition of Al in the second barrier layer decreases from layer to layer in the direction from the first semiconductor layer 123 to the second semiconductor layer 125. Specifically, from the growth to the end, the Al components in each second barrier layer are x21 and x22 … … x2n in sequence, wherein the number of the Al components is more than or equal to 10 and less than or equal to 2n and less than or equal to 30, and the number of the Al components is from x21 to x2n and is reduced in sequence. The material of the second well layer is (Al) _y2 Ga _1-y2 ) _0.25 In _0.25 P _0.5 Y2 is more than or equal to 0.1 and less than or equal to 0.4. In other embodiments, the composition of Al in the second barrier layer may also decrease from layer to layer and then increase from layer to layer. The thickness of each second barrier layer can be the same or different, for example, can be monotonically increased or monotonically decreased, and is preferably the same; the thicknesses of the second well layers may be the same or different, and may be, for example, monotonically increasing or monotonically decreasing, and are preferably the same.

As shown in fig. 6d, a second semiconductor layer 125 is grown on the active layer 124.

In this step, the second semiconductor layer 125 is grown on the active layer 124 using, for example, any one or more of a Metal Organic Chemical Vapor Deposition (MOCVD) process, a Molecular Beam Epitaxy (MBE) process, and an ultra-high vacuum chemical vapor deposition (UHVCVD) process. The second semiconductor layer 125 includes, in order from bottom to top, a second barrier layer 1251, a second confinement layer 1252, a second current spreading layer 1253, and a second ohmic contact layer 1254.

In this embodiment, the second semiconductor layer 125 is, for example, a P-type semiconductor layer. Specifically, the second blocking layer 1251 is, for example, an AlGaInP material layer with a thickness of 100nm to 400nm (for example, 200 nm); the second confinement layer 1252 is, for example, a layer of Mg-doped AlInP material with a thickness of 200nm to 600nm (e.g., 400 nm); the second current spreading layer 1253 is, for example, a Mg-doped GaP material layer with a thickness of 500nm to 1500nm (for example, 1000 nm); the second ohmic contact layer 1254 is, for example, a layer of C-doped GaP material with a thickness of 100nm to 300nm (e.g., 150 nm).

According to the epitaxial structure of the light emitting diode and the preparation method thereof, the barrier layer is arranged in the active layer to block holes and the movement of electrons, and the electrons and the holes are mainly limited in the active layer, so that the electrons and the holes are combined to emit light in the active layer, and the brightness of the light emitting diode is ensured.

Furthermore, the first barrier layer in the first quantum well layer and the second barrier layer in the second quantum well layer both adopt a gradient structure, and in the whole, the potential barriers in the first quantum well layer and the second quantum well layer gradually rise from the direction from the P-type semiconductor layer to the N-type semiconductor layer, so that the hole is more difficult to pass closer to the N-type semiconductor layer, the phenomenon that the hole is easy to accumulate towards one side of the N-type semiconductor layer and then leak due to energy band bending is weakened, the effect of lifting the energy band at one side of the N-type semiconductor layer to a certain degree is also played to weaken the energy band bending, the leakage of electrons and holes towards the outside of the active layer is reduced, and the reliability of the light-emitting diode is improved.

Furthermore, the thickness of the barrier layer is larger than that of any first barrier layer in the first quantum well layer and that of any second barrier layer in the second quantum well layer, so that the reliability of the barrier effect of the barrier layer is improved.

While embodiments in accordance with the invention have been described above, these embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. An epitaxial structure for a light emitting diode comprising:

a substrate;

an active layer on the first semiconductor layer;

2. The epitaxial structure of claim 1, wherein the active layer is a layer of AlGaInP material.

3. The epitaxial structure of claim 2, wherein the first quantum well layer comprises multiple periods of first barrier layers and first well layers, the first barrier layers and the first well layers being arranged alternately; the second quantum well layer comprises a plurality of periods of second barrier layers and second well layers, and the second barrier layers and the second well layers are alternately arranged.

4. The epitaxial structure of claim 3, wherein when the first semiconductor layer is an N-type semiconductor layer, the composition of Al in the plurality of first barrier layers decreases in order from the first semiconductor layer to the second semiconductor layer; when the first semiconductor layer is a P-type semiconductor layer, from the second semiconductor layer to the first semiconductor layer, the Al components in the multiple first barrier layers are sequentially reduced, or the Al components in the multiple first barrier layers are reduced and then increased.

5. The epitaxial structure of claim 4, wherein the material of the first barrier layer is (Al) _x1 Ga _1-x1 ) _0.25 In _0.25 P _0.5 X1 is more than or equal to 0.5 and less than or equal to 0.9; the material of the first well layer is (Al) _y1 Ga _1-y1 ) _0.25 In _0.25 P _0.5 ，0.1≤y1≤0.4。

6. The epitaxial structure of claim 3, wherein when the first semiconductor layer is an N-type semiconductor layer, the composition of Al in the multiple second barrier layers decreases sequentially or decreases first and then increases in the direction from the first semiconductor layer to the second semiconductor layer; when the first semiconductor layer is a P-type semiconductor layer, the Al components in the plurality of second barrier layers are sequentially reduced from the second semiconductor layer to the first semiconductor layer.

7. Epitaxial structure according to claim 6, wherein the material of the second barrier layer is (Al) _x2 Ga _1-x2 ) _0.25 In _0.25 P _0.5 X2 is more than or equal to 0.5 and less than or equal to 0.9; the material of the second well layer is (Al) _y2 Ga _1-y2 ) _0.25 In _0.25 P _0.5 ，0.1≤y2≤0.4。

8. The epitaxial structure of claim 3, wherein the number of periods of the first and second quantum well layers is the same or different; the number of cycles of the first quantum well layer is 10-30; the number of cycles of the second quantum well layer is 10 to 30.

9. Epitaxial structure according to claim 3, wherein the material of the barrier layer is (Al) _xp Ga _1-xp ) _0.25 In _0.25 P _0.5 。

10. The epitaxial structure of claim 9, wherein the composition of Al in the barrier layer is equal to or greater than the composition of Al in any one of the first quantum well layers, and the composition of Al in the barrier layer is equal to or greater than the composition of Al in any one of the second quantum well layers.

11. The epitaxial structure of claim 3, wherein the first semiconductor layer comprises a first ohmic contact layer, a first window layer, a first confinement layer, and a first barrier layer stacked in this order, wherein the first ohmic contact layer is on the substrate;

12. Epitaxial structure according to claim 11, wherein the first and second barrier layers are of the same material and are both (Al) _z Ga _1-z ) _0.25 In _0.25 P _0.5 。

13. The epitaxial structure of claim 12, wherein the composition of Al in the first and second barrier layers is equal to or greater than the composition of Al in any one of the first quantum well layers, and the composition of Al in the first and second barrier layers is equal to or greater than the composition of Al in any one of the second quantum well layers.

14. The epitaxial structure of claim 3, wherein the barrier layer has a thickness greater than the thickness of any one of the first barrier layers in the first quantum well layer; the thickness of the barrier layer is larger than that of any second barrier layer in the second quantum well layer.

15. The epitaxial structure of claim 14, wherein the active layer has a thickness of 380nm to 1040nm, the first quantum well layer has a thickness of 140nm to 420nm, the barrier layer has a thickness of 100nm to 200nm, and the second quantum well layer has a thickness of 140nm to 420nm.

16. A preparation method of an epitaxial structure of a light emitting diode comprises the following steps:

providing a substrate;

forming an active layer on the first semiconductor layer;

the active layer is formed by sequentially forming a first quantum well layer, a barrier layer and a second quantum well layer from bottom to top, wherein the first quantum well layer is located on the first semiconductor layer.

17. The method of claim 16, wherein the active layer is a layer of AlGaInP material.

18. The manufacturing method according to claim 17, wherein the first quantum well layer comprises a plurality of periods of first barrier layers and first well layers, and the first barrier layers and the first well layers are alternately arranged; the second quantum well layer includes a plurality of periods of second barrier layers and second well layers, and the second barrier layers and the second well layers are alternately arranged.

19. The manufacturing method according to claim 18, wherein when the first semiconductor layer is an N-type semiconductor layer, the composition of Al in the plurality of first barrier layers decreases in order from the first semiconductor layer to the second semiconductor layer; when the first semiconductor layer is a P-type semiconductor layer, from the second semiconductor layer to the first semiconductor layer, the Al components in the multiple first barrier layers are sequentially reduced, or the Al components in the multiple first barrier layers are reduced and then increased.

20. The method as claimed in claim 19, wherein the material of the first barrier layer is (Al) _x1 Ga _1-x1 ) _0.25 In _0.25 P _0.5 X1 is more than or equal to 0.5 and less than or equal to 0.9; the material of the first well layer is (Al) _y1 Ga _1-y1 ) _0.25 In _0.25 P _0.5 ，0.1≤y1≤0.4。

21. The manufacturing method according to claim 18, wherein when the first semiconductor layer is an N-type semiconductor layer, the Al composition in the plurality of second barrier layers decreases sequentially from the first semiconductor layer to the second semiconductor layer, or the Al composition in the plurality of second barrier layers decreases first and then increases; when the first semiconductor layer is a P-type semiconductor layer, the Al components in the plurality of second barrier layers are sequentially reduced from the second semiconductor layer to the first semiconductor layer.

22. The method as recited in claim 21, wherein the second barrier layer is formed from (Al) _x2 Ga _1-x2 ) _0.25 In _0.25 P _0.5 X2 is more than or equal to 0.5 and less than or equal to 0.9; the material of the second well layer is (Al) _y2 Ga _1-y2 ) _0.25 In _0.25 P _0.5 ，0.1≤y2≤0.4。

23. The production method according to claim 18, wherein the number of periods of the first quantum well layer and the second quantum well layer is the same or different; the periodicity of the first quantum well layer is 10-30; the number of cycles of the second quantum well layer is 10 to 30.

24. The production method according to claim 18, wherein the material of the barrier layer is (Al) _xp Ga _1-xp ) _0.25 In _0.25 P _0.5 。

25. The preparation method of claim 24, wherein the composition of Al in the barrier layer is greater than or equal to that of Al in any one of the first quantum well layers; and the composition of Al in the barrier layer is more than or equal to that of Al in any second barrier layer in the second quantum well layer.

26. The manufacturing method according to claim 18, wherein forming the first semiconductor layer includes forming a first ohmic contact layer, a first window layer, a first confinement layer, and a first barrier layer, which are stacked in this order, wherein the first ohmic contact layer is located on the substrate;

27. The production method according to claim 26, wherein the first barrier layer and the second barrier layer are made of the same material and are both (Al) _z Ga _1-z ) _0.25 In _0.25 P _0.5 。

28. The method of claim 27, wherein the composition of Al in the first and second barrier layers is greater than or equal to the composition of Al in any one of the first barrier layers in the first quantum well layer, and the composition of Al in the first and second barrier layers is greater than or equal to the composition of Al in any one of the second barrier layers in the second quantum well layer.

29. The manufacturing method according to claim 18, wherein the thickness of the barrier layer is larger than that of any one of the first quantum well layers; the thickness of the barrier layer is larger than that of any second barrier layer in the second quantum well layer.

30. The manufacturing method according to claim 29, wherein the thickness of the active layer is 380nm to 1040nm, the thickness of the first quantum well layer is 140nm to 420nm, the thickness of the barrier layer is 100nm to 200nm, and the thickness of the second quantum well layer is 140nm to 420nm.