CN115939276A - Light emitting diode for improving luminous efficiency and preparation method thereof - Google Patents

Abstract

The disclosure provides a light-emitting diode with improved light efficiency and a preparation method thereof, belonging to the technical field of optoelectronic manufacturing. The light emitting diode comprises a substrate, a buffer layer and an epitaxial layer stacked in sequence, and the roughness of the surface of the buffer layer away from the substrate is 5 to 6.5. The embodiments of the present disclosure can improve the light absorption problem of the buffer layer and improve the luminous efficiency of the LED.

Description

Light-emitting diode with improved light efficiency and preparation method thereof

technical field

The present disclosure relates to the technical field of optoelectronic manufacturing, in particular to a light-emitting diode with improved light efficiency and a preparation method thereof.

Background technique

Light Emitting Diode (English: Light Emitting Diode, referred to as: LED), as a very influential new product in the optoelectronics industry, has the characteristics of small size, long service life, colorful colors, and low energy consumption. It is widely used in lighting, display screens , signal lights, backlight, toys and other fields.

In the related art, a light emitting diode generally includes a substrate and an epitaxial layer stacked on the substrate. For GaN-based light-emitting diodes, due to the large lattice mismatch and thermal mismatch between the GaN material and the sapphire substrate, it is necessary to grow an AlN buffer layer on the substrate before growing the epitaxial layer on the substrate. , to reduce mismatch defects.

However, since the AlN buffer layer absorbs part of the light, the luminous efficiency of the light emitting diode is reduced.

Contents of the invention

Embodiments of the present disclosure provide a light-emitting diode with improved light efficiency and a preparation method thereof, which can improve the light absorption problem of the buffer layer and improve the light-emitting efficiency of the light-emitting diode. Described technical scheme is as follows:

In one aspect, an embodiment of the present disclosure provides a light emitting diode, the light emitting diode includes a substrate, a buffer layer and an epitaxial layer stacked in sequence, the surface of the buffer layer away from the substrate has a roughness of 5 to 6.5.

Optionally, the buffer layer includes a plurality of AlN composite layers stacked in sequence, the AlN composite layer includes a first AlN layer and a second AlN layer stacked in sequence, and the second AlN layer is far away from the surface of the substrate The roughness is not smaller than the roughness of the surface of the first AlN layer away from the substrate.

Optionally, the thickness of the first AlN layer is smaller than the thickness of the second AlN layer.

Optionally, a ratio of the thickness of the first AlN layer to the thickness of the second AlN layer is 1/6 to 1/2.

Optionally, the number of the AlN composite layers is 2-5.

On the other hand, an embodiment of the present disclosure provides a method for manufacturing a light emitting diode, the method comprising: providing a substrate; growing a buffer layer on the substrate, and the buffer layer is far away from the surface of the substrate The roughness is 5 to 6.5; an epitaxial layer is grown on the buffer layer.

Optionally, the growing the buffer layer on the substrate includes: controlling the power to 3500w to 5000w, feeding nitrogen at a flow rate of 300 sccm to 500 sccm, feeding oxygen at a flow rate of 3 sccm to 6 sccm, and a time of 10 min to 15 min, The temperature is 450°C to 550°C, and the Al target is sputtered to form the first AlN layer; the control power is 2000w to 3000w, the flow rate of nitrogen gas is 300sccm to 500sccm, the flow rate of oxygen gas is 6sccm to 10sccm, and the time is 5min to For 10 minutes, at a temperature of 600° C. to 750° C., the Al target is sputtered to form a second AlN layer, forming an AlN composite layer.

Optionally, the growing the buffer layer on the substrate further includes: after forming an AlN composite layer, controlling the power to 3000w to 4000w, the flow rate of nitrogen gas is 300sccm to 500sccm, and the flow rate of oxygen gas is 3sccm To 6sccm, the time is 6min to 10min, the temperature is 500°C to 600°C, sputter the Al target to form the first AlN layer; the control power is 2500w to 3000w, the flow rate of nitrogen gas is 300sccm to 500sccm, and the flow rate of oxygen gas 4sccm to 8sccm, the time is 4min to 8min, the temperature is 600°C to 750°C, and the Al target is sputtered to form a second AlN layer, forming another AlN composite layer.

Optionally, the buffer layer includes 2 to 5 AlN composite layers stacked in sequence, the AlN composite layer includes a first AlN layer and a second AlN layer stacked in sequence, and the second AlN layer is far away from the substrate The roughness of the surface of the first AlN layer is not smaller than the roughness of the surface of the first AlN layer away from the substrate.

Optionally, before growing the buffer layer on the substrate, it includes: controlling the flow of Ar to 400sccm to 800sccm for 3min to 5min; reducing the flow of Ar to 300sccm to 500sccm for 10min to 15min .

The beneficial effects brought by the technical solutions provided by the embodiments of the present disclosure at least include:

The roughness of the surface of the buffer layer grown on the substrate away from the substrate in the light-emitting diode of the embodiment of the present disclosure is 5 to 6.5, which improves the buffer layer compared with the roughness of the buffer layer in the related art. The roughness of the layer makes the surface of the buffer layer rougher. Because the surface of the buffer layer is rougher, there will be some reflection after the light emitted by the epitaxial layer enters the buffer layer, so that part of the light absorbed by the buffer layer will be reflected again due to reflection, thereby improving the problem of light absorption of the buffer layer , to improve the luminous efficiency of light-emitting diodes.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present disclosure. For those skilled in the art, other drawings can also be obtained based on these drawings without creative effort.

FIG. 1 is a schematic structural diagram of a light emitting diode provided by an embodiment of the present disclosure;

Fig. 2 is a flow chart of a method for manufacturing a light-emitting diode provided by an embodiment of the present disclosure;

Fig. 3 is a schematic diagram of a comparison of luminous efficiency provided by an embodiment of the present disclosure.

The symbols in the figure are explained as follows:

10. Substrate;

20. Buffer layer; 210. AlN composite layer; 211. First AlN layer; 212. Second AlN layer;

30. n-type layer;

40. Light emitting layer; 41. Quantum well layer; 42. Quantum barrier layer;

50. p-type layer; 51. low-temperature p-type GaN layer; 52. p-type AlGaN layer; 53. high-temperature p-type GaN layer; 54. p-type ohmic contact layer;

60. A non-doped GaN layer.

Detailed ways

In order to make the purpose, technical solution and advantages of the present disclosure clearer, the implementation manners of the present disclosure will be further described in detail below in conjunction with the accompanying drawings.

Unless otherwise defined, the technical terms or scientific terms used herein shall have the usual meanings understood by those having ordinary skill in the art to which the present disclosure belongs. "First", "second", "third" and similar words used in the specification and claims of this disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components . Likewise, words like "a" or "one" do not denote a limitation in quantity, but indicate that there is at least one. Words such as "comprises" or "comprising" and similar terms mean that the elements or items listed before "comprising" or "comprising" include the elements or items listed after "comprising" or "comprising" and their equivalents, and do not exclude other component or object. Words such as "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "Down", "Left", "Right", "Top", "Bottom" and so on are only used to indicate the relative positional relationship. When the absolute position of the described object changes, the relative positional relationship may also be Change accordingly.

FIG. 1 is a schematic structural diagram of a light emitting diode provided by an embodiment of the present disclosure. As shown in FIG. 1 , a light emitting diode includes a substrate 10 , a buffer layer 20 and an epitaxial layer stacked in sequence. Wherein, the roughness of the surface of the buffer layer 20 away from the substrate 10 is 5 to 6.5.

The roughness of the surface of the buffer layer 20 grown on the substrate 10 away from the substrate 10 in the light-emitting diode of the embodiment of the present disclosure is 5 to 6.5, which is compared with the roughness of the buffer layer 2.5 to 3.5 in the related art, The roughness of the buffer layer 20 is improved, making the surface of the buffer layer 20 rougher. Since the surface of the buffer layer 20 is rougher, there will be a certain reflection after the light emitted by the epitaxial layer enters the buffer layer 20, so that part of the light absorbed by the buffer layer 20 will be reflected again due to reflection, thereby improving the buffer layer. 20 The problem of light absorption, improve the luminous efficiency of light-emitting diodes.

Exemplarily, the roughness of the surface of the buffer layer 20 away from the substrate 10 may be 6. Larger roughness can make the light emitted by the epitaxial layer reflect to a certain extent after entering the buffer layer 20, so that part of the light absorbed by the buffer layer 20 will be reflected again due to reflection, thereby improving the problem of light absorption by the buffer layer 20 .

Optionally, the buffer layer 20 includes a plurality of sequentially stacked AlN composite layers 210, the AlN composite layer 210 includes a first AlN layer 211 and a second AlN layer 212 stacked in sequence, and the second AlN layer 212 is away from the surface of the substrate 10 The roughness is not smaller than that of the surface of the first AlN layer 211 away from the substrate 10 .

In this way, a smooth AlN layer and a rough AlN layer are grown cyclically, which can effectively increase the roughness of the buffer layer 20, so that the light emitted by the epitaxial layer will reflect to a certain extent after entering the buffer layer 20, so that the light absorbed by the buffer layer 20 Part of the light will be reflected again due to reflection, thereby improving the light absorption problem of the buffer layer 20 .

Optionally, the thickness of the first AlN layer 211 is smaller than the thickness of the second AlN layer 212 .

The roughness of the AlN composite layer formed by the combination of alternately formed AlN layers in this way will be greater, which is beneficial to improve the roughness of the surface of the buffer layer away from the substrate 10 .

Exemplarily, the ratio of the thickness of the first AlN layer 211 to the thickness of the second AlN layer 212 is 1/6 to 1/2.

By controlling the ratio of the thickness of the first AlN layer 211 to the thickness of the second AlN layer 212 within the above-mentioned range, the thickness of the second AlN layer 212 can be avoided from being too small, and the purpose of improving the roughness of the AlN composite layer cannot be achieved. And the roughness of the surface of the buffer layer away from the substrate 10 can be more easily approached to 5 to 7 .

Optionally, the number of AlN composite layers 210 is 2-5.

By setting the number of AlN composite layers 210 within the above-mentioned range, it is possible to avoid setting too many AlN composite layers 210, which increases the difficulty of making the buffer layer 20; to improve the roughness.

Exemplarily, the number of AlN composite layers 210 is two.

In the disclosed embodiment, the substrate 10 is a sapphire substrate 10 . The sapphire substrate 10 is a common substrate 10 with mature technology and low cost. Specifically, it may be a patterned sapphire substrate 10 or a flat sapphire substrate 10 .

Optionally, the epitaxial layer includes an n-type layer 30 , a light-emitting layer 40 and a p-type layer 50 stacked in sequence.

Wherein, the light-emitting layer 40 includes a plurality of quantum well layers 41 and a plurality of quantum barrier layers 42, and the plurality of quantum well layers 41 and the plurality of quantum barrier layers 42 are stacked alternately.

Optionally, n-type layer 30 may be an n-type GaN layer. The thickness of the n-type layer 30 is 1.5 μm to 3.5 μm.

Wherein, the dopant of the n-type layer 30 is silane.

Optionally, the p-type layer 50 may include a low-temperature p-type GaN layer 51 , a p-type AlGaN layer 52 , a high-temperature p-type GaN layer 53 and a p-type ohmic contact layer 54 sequentially stacked on the light emitting layer 40 .

Wherein, the dopant of the p-type layer 50 is magnesiumocene.

Exemplarily, the low-temperature p-type GaN layer 51 may be a GaN layer grown at a temperature of 700°C to 800°C; the high-temperature p-type GaN layer 53 may be a GaN layer grown at a temperature of 900°C to 1050°C. Both the low-temperature p-type GaN layer 51 and the high-temperature p-type GaN layer 53 are Mg-doped.

Wherein, the thickness of the low-temperature p-type GaN layer 51 may be 30 nm to 120 nm, for example, the thickness of the low-temperature p-type GaN layer 51 may be 100 nm.

Wherein, the thickness of the high-temperature p-type GaN layer 53 may be 50 nm to 150 nm, for example, the thickness of the high-temperature p-type GaN layer 53 may be 100 nm.

In the embodiment of the present disclosure, the p-type AlGaN layer 52 acts as an electron blocking layer for blocking electrons from entering the p-type layer 50 . Both the p-type AlGaN layer 52 and the p-type ohmic contact layer 54 are Mg-doped.

Alternatively, the thickness of the p-type AlGaN layer 52 may be 50 nm to 150 nm. As an example, in the embodiment of the present disclosure, the thickness of the p-type AlGaN layer 52 is 80 nm.

If the thickness of the p-type AlGaN layer 52 is too thin, the blocking effect on electrons will be reduced; if the thickness of the p-type AlGaN layer 52 is too thick, the absorption of light by the p-type AlGaN layer 52 will be increased, thereby reducing the luminous efficiency of the LED. .

Optionally, the thickness of the p-type ohmic contact layer 54 may be 3 nm to 10 nm. As an example, in the embodiment of the present disclosure, the thickness of the p-type ohmic contact layer 54 is 8 nm.

If the thickness of the p-type ohmic contact layer 54 is too thin, the current contact between the epitaxial layer and the electrode will be affected; if the thickness of the p-type ohmic contact layer 54 is too thick, the absorption of light by the p-type ohmic contact layer 54 will be increased, thereby The luminous efficiency of the LED is reduced.

In the embodiment of the present disclosure, the thickness of the quantum well layer 41 in the light emitting layer 40 is 2nm to 5nm.

By controlling the thickness of the quantum well layer 41 within the above-mentioned range, the thickness of the quantum well layer 41 can be avoided from being set too thin to meet the purpose of electron-hole recombination; production cost.

Exemplarily, the thickness of the quantum well layer 41 may be 3 nm.

Optionally, the quantum barrier layer 42 may be an n-type GaN quantum barrier layer 42 with a thickness of 5 nm to 15 nm.

By controlling the thickness of the n-type GaN quantum barrier layer 42 within the above-mentioned range, the thickness of the n-type GaN quantum barrier layer 42 can be avoided from being set too thin to meet the purpose of electron-hole recombination; it can also avoid the n-type GaN quantum barrier If the thickness of the layer 42 is set too thick, the manufacturing cost will be increased.

Exemplarily, the thickness of the n-type GaN quantum barrier layer 42 is 10 nm.

Optionally, the light emitting layer 40 includes 8 to 12 quantum well layers 41 and 8 to 12 quantum barrier layers 42 .

By controlling the number of layers of the quantum well layer 41 and the quantum barrier layer 42 within the above-mentioned range, it can be avoided that the number of layers of the quantum well layer 41 and the quantum barrier layer 42 is set too little, and the thickness of the light-emitting layer 40 is too small to achieve the desired effect. The purpose of electron-hole recombination is satisfied; the thickness of the light-emitting layer 40 is set too thick to avoid increasing the production cost.

Exemplarily, the number of quantum well layers 41 may be 10 layers, and the number of quantum barrier layers 42 may be 10 layers.

It should be noted that FIG. 1 only shows part of the structure of the light emitting layer 40 , and is not used to limit the number of periods in which the quantum well layers 41 and the quantum barrier layers 42 are alternately stacked.

Optionally, as shown in FIG. 1 , a non-doped GaN layer 60 is further included between the buffer layer 20 and the p-type layer 50 .

In the disclosed embodiment, a non-doped GaN layer 60 is grown between the buffer layer 20 and the n-type layer 30. Compared with the substrate 10, due to the crystal structure of the non-doped GaN layer 60 and the n-type layer 30 Similarly, by setting the non-doped GaN layer 60 as a transition layer, the crystal quality of subsequent epitaxial layers can be improved.

Wherein, the thickness of the non-doped GaN layer 60 is 1 μm to 2 μm. Exemplarily, the thickness of the undoped GaN layer 60 is 1.5 μm.

By setting the thickness of the non-doped GaN layer 60 within the above-mentioned range, the thickness of the non-doped GaN layer 60 can be avoided from being too thin, so that the effect of transition cannot be achieved, and the crystal quality of the grown epitaxial layer can be reduced; If the thickness of the doped GaN layer 60 is too thick, the absorption of light by the non-doped GaN layer 60 will be increased, thereby reducing the luminous efficiency of the epitaxial wafer.

Fig. 2 is a flow chart of a method for manufacturing a light emitting diode provided by an embodiment of the present disclosure. This method was used to prepare the epitaxial wafer shown in FIG. 1 . As shown in Figure 2, the preparation method comprises:

S11: Provide a substrate.

S12: growing a buffer layer on the substrate.

Wherein, the roughness of the surface of the buffer layer away from the substrate is 5 to 6.5.

S13: growing an epitaxial layer on the buffer layer.

In the light-emitting diode prepared by this preparation method, the roughness of the surface of the buffer layer grown on the substrate away from the substrate 10 has a roughness of 5 to 6.5, which is improved compared with the roughness of the buffer layer in the related art of 2.5 to 3.5. The roughness of the buffer layer is improved, making the surface of the buffer layer rougher. Because the surface of the buffer layer is rougher, there will be some reflection after the light emitted by the epitaxial layer enters the buffer layer, so that part of the light absorbed by the buffer layer will be reflected again due to reflection, thereby improving the problem of light absorption of the buffer layer , to improve the luminous efficiency of light-emitting diodes.

In step S11, the substrate is a sapphire substrate, a silicon substrate or a silicon carbide substrate. The substrate can be a flat substrate or a patterned substrate.

As an example, in the embodiment of the present disclosure, the substrate is a sapphire substrate. Sapphire substrate is a commonly used substrate with mature technology and low cost. Specifically, it can be a patterned sapphire substrate or a sapphire flat substrate.

In step S11, the sapphire substrate may be subjected to high-temperature cleaning treatment for 5 minutes to 20 minutes in a hydrogen atmosphere at 1000° C. to 1200° C., and then nitriding treatment.

In step S11, the sapphire substrate can be pretreated, the sapphire substrate is placed in a MOCVD (Metal-organic Chemical Vapor Deposition, metal-organic chemical vapor deposition) reaction chamber, and the sapphire substrate is baked for 12 minutes to 18 minutes. As an example, in the embodiment of the present disclosure, the sapphire substrate is baked for 15 minutes.

Specifically, the baking temperature may be 1000° C. to 1200° C., and the pressure in the MOCVD reaction chamber may be 100 mbar to 200 mbar during baking.

In the embodiment of the present disclosure, the following steps may be included before growing the buffer layer:

In the first step, the flow rate of Ar is controlled to be 400 sccm to 800 sccm.

Wherein, the time is 3 minutes to 5 minutes. For example, the time is 4min.

Specifically, it may include: putting the substrate to be coated into a PVD device, and then feeding Ar, and controlling the flow of Ar to be 500 sccm.

This can play the role of gas buffer and stable inflow, and prepare for the next step of bombarding the Al target.

In the second step, the flow rate of Ar is reduced from 300 sccm to 500 sccm.

Wherein, the time is 10 minutes to 15 minutes. For example, the time is 12min.

Specifically, it may include: reducing the flow rate of Ar to 400 sccm, and controlling the time of feeding Ar to 12 minutes. In this way, impurities and water vapor on the surface of the Al target can be removed.

The buffer layer grown in step S12 may include 2 to 5 AlN composite layers stacked in sequence, the AlN composite layer includes a first AlN layer and a second AlN layer stacked in sequence, and the roughness of the second AlN layer is not less than that of the first AlN layer roughness.

Exemplarily, the buffer layer may include two sequentially stacked AlN composite layers.

In an embodiment of the present disclosure, growing the first AlN composite layer of the buffer layer on the substrate may include:

The control power is 3500w to 5000w, the flow rate of nitrogen gas is 300sccm to 500sccm, the flow rate of oxygen gas is 3sccm to 6sccm, the time is 10min to 15min, the temperature is 450°C to 550°C, and the Al target is sputtered to form the first AlN layer.

The control power is 2000w to 3000w, the flow rate of nitrogen gas is 300sccm to 500sccm, the flow rate of oxygen gas is 6sccm to 10sccm, the time is 5min to 10min, the temperature is 600°C to 750°C, sputtering the Al target to generate the second AlN layer, forming an AlN composite layer.

Wherein, after growing the first AlN composite layer, the preparation method may include: closing all gases for about 30s to 60s. This can play the role of surface annealing, making the AlN film more compact.

In an embodiment of the present disclosure, growing the second AlN composite layer of the buffer layer on the substrate includes:

The control power is 3000w to 4000w, the flow rate of nitrogen gas is 300sccm to 500sccm, the flow rate of oxygen gas is 3sccm to 6sccm, the time is 6min to 10min, the temperature is 500°C to 600°C, and the Al target is sputtered to form the first AlN layer.

The control power is 2500w to 3000w, the flow rate of nitrogen gas is 300sccm to 500sccm, the flow rate of oxygen gas is 4sccm to 8sccm, the time is 4min to 8min, the temperature is 600°C to 750°C, sputtering the Al target to generate the second AlN layer to form another AlN composite layer.

Wherein, after growing the second AlN composite layer, the preparation method may include: closing all gases for about 30s to 60s. This can play the role of surface annealing, making the AlN film more compact.

In the embodiment of the present disclosure, after the two layers of AlN composite layers are grown, the preparation method may further include: first gradually shutting down Ar, then shutting down O2, and finally turning off N2 to end the coating.

Cyclic growth of a smooth AlN layer and a rough AlN layer through the above method can effectively increase the roughness of the buffer layer, so that there will be a certain reflection after the light emitted by the epitaxial layer enters the buffer layer, so that the part absorbed by the buffer layer The light will be reflected again due to reflection, thereby improving the problem of light absorption of the buffer layer.

Before step S13, the preparation method may include: growing a non-doped GaN layer on the buffer layer.

Compared with the substrate, since the crystal structure of the non-doped GaN layer is similar to that of the n-type layer, setting the non-doped GaN layer as a transition layer can improve the crystal quality of the subsequent epitaxial layer.

Wherein, the thickness of the non-doped GaN layer is 1 μm to 2 μm. Exemplarily, the thickness of the non-doped GaN layer is 1.5 μm.

Specifically, after the growth of the low-temperature GaN buffer layer is completed, the temperature is adjusted to 1000°C to 1200°C, and a non-doped GaN layer with an epitaxial growth thickness of 1 μm to 2 μm is grown, the growth pressure is 100 Torr to 500 Torr, and the V/III ratio is 200 to 3000.

Step S13 may include the following steps:

In the first step, an n-type layer is grown on the undoped GaN layer.

Optionally, the n-type layer may be an n-type GaN layer. The n-type layer has a thickness of 1.5 μm to 3.5 μm. Wherein, the dopant of the n-type layer is silane.

Specifically, after the growth of the non-doped GaN layer is completed, a layer of n-type GaN layer with a stable Si doping concentration is grown, the thickness is 1.5 μm to 3.5 μm, the growth temperature is 950° C. to 1150° C., and the growth pressure is 300 Torr to 500 Torr. V/III ratio is 400 to 3000.

In the second step, a light-emitting layer is grown on the n-type layer.

Specifically, after the growth of the n-type layer is completed, alternately stacked quantum well layers and quantum barrier layers are grown.

Wherein, the quantum well layer is an In _y Ga _1-y N (0.1<y<0.3) layer, and the quantum well layer may include a first InGaN layer, a second InGaN layer and a third InGaN layer stacked in sequence.

When growing the quantum well layer, feed ammonia gas, ethyl gallium and trimethyl indium into the reaction chamber for 30s to 60s, and control the growth temperature in the reaction chamber to 700°C to 850°C, and the growth pressure 100Torr to 500Torr, V/III ratio is 2000 to 20000, thickness is 2nm to 5nm.

Exemplarily, the thickness of the quantum well layer may be 3 nm.

In the embodiment of the present disclosure, the quantum barrier layer may be an n-type GaN quantum barrier layer.

When growing the quantum barrier layer, the growth temperature in the reaction chamber is controlled to be 850° C. to 950° C., the growth pressure is 100 Torr to 500 Torr, the V/III ratio is 2000 to 20000, and the thickness is 5 nm to 15 nm.

Exemplarily, the thickness of the n-type GaN quantum barrier layer is 10 nm.

Optionally, both the number of quantum well layers and the number of quantum barrier layers are 8 to 12 layers. Exemplarily, the number of quantum well layers and the number of quantum barrier layers are both 10.

In the third step, a p-type layer is grown on the light-emitting layer.

Optionally, the p-type layer has a thickness of 30nm to 120nm. Wherein, the dopant of the p-type layer is magnesiumocene.

Wherein, the p-type layer may include a low-temperature p-type GaN layer, a p-type AlGaN layer, a high-temperature p-type GaN layer and a p-type ohmic contact layer sequentially stacked on the light emitting layer. Both the low-temperature p-type GaN layer and the high-temperature p-type GaN layer are Mg-doped.

Wherein, the thickness of the low-temperature p-type GaN layer may be 30 nm to 120 nm, for example, the thickness of the low-temperature p-type GaN layer may be 100 nm.

Wherein, the thickness of the high-temperature p-type GaN layer may be 50nm to 150nm, for example, the thickness of the low-temperature p-type GaN layer may be 100nm.

In the embodiments of the present disclosure, the p-type AlGaN layer is used as an electron blocking layer for blocking electrons from entering the p-type layer. Both the p-type AlGaN layer and the p-type ohmic contact layer are Mg-doped.

Optionally, the thickness of the p-type AlGaN layer may be 50nm to 150nm. As an example, in the embodiment of the present disclosure, the thickness of the p-type AlGaN layer is 80 nm.

Optionally, the p-type ohmic contact layer may have a thickness of 3 nm to 10 nm. As an example, in the embodiment of the present disclosure, the thickness of the p-type ohmic contact layer is 8 nm.

Specifically, after the growth of the light-emitting layer is completed, a low-temperature p-type GaN layer with a thickness of 30nm to 120nm is grown, the growth temperature is 700°C to 800°C, the growth time is 3min to 15min, the pressure is 100Torr to 600Torr, and the V/III ratio is 1000 to 4000.

After the growth of the low-temperature p-type GaN layer is completed, a p-type AlGaN layer with a thickness of 50nm to 150nm is grown, the growth temperature is 900°C to 1000°C, the growth time is 4min to 15min, the growth pressure is 50Torr to 300Torr, and the V/III ratio is 1000 to 10000.

After the growth of the p-type AlGaN layer is completed, a high-temperature p-type GaN layer with a thickness of 50nm to 150nm is grown, the growth temperature is between 900°C and 1050°C, the growth time is 10min to 20min, the growth pressure is 100Torr to 500Torr, and the V/III ratio 500 to 4000.

After the growth of the high-temperature p-type GaN layer is completed, a p-type ohmic contact layer with a thickness of 3nm to 10nm is grown, the growth temperature is 700°C to 850°C, the growth time is 0.5min to 5min, the growth pressure is 100Torr to 500Torr, and the V/III ratio 10000 to 20000.

After step S13, the preparation method may further include: annealing the epitaxial wafer.

After epitaxial growth, reduce the temperature of the reaction chamber to 600°C to 900°C, perform annealing treatment in PN ₂ atmosphere for 10min to 30min, then gradually lower to room temperature, and then, after cleaning, deposition, photolithography and etching subsequent processing processes Made into a single 22×35mil chip.

In specific implementation, the embodiments of the present disclosure can use high-purity _H2 or/and _N2 as the carrier gas, TEGa or TMGa as the Ga source, TMIn as the In source, _SiH4 as the n-type dopant, and TMAl as the aluminum source , ammonia as the N source, and Cp ₂ Mg as the p-type dopant.

Fig. 3 is a schematic diagram of a comparison of luminous efficiency provided by an embodiment of the present disclosure. As shown in FIG. 3 , the roughness of the buffer layer prepared by the preparation method provided by the embodiment of the present disclosure is higher than that of the buffer layer prepared by the related technology.

As shown in FIG. 3 , the external quantum efficiency (External QuantumEfficiency, EQE) of the buffer layer prepared in the embodiment of the present disclosure is higher than the EQE of the buffer layer prepared by the related technology. It can be seen that the luminous efficiency of the light-emitting diode can be effectively improved.

The above descriptions are only optional embodiments of the present disclosure, and are not intended to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure shall be included in the protection of the present disclosure. within range.

Claims (10)

1. A light-emitting diode is characterized by comprising a substrate (10), a buffer layer (20) and an epitaxial layer which are sequentially laminated, wherein the roughness of the surface, far away from the substrate (10), of the buffer layer (20) is 5-6.5.

2. The light-emitting diode according to claim 1, wherein the buffer layer (20) comprises a plurality of sequentially laminated AlN composite layers (210), the AlN composite layers (210) comprising a first AlN layer (211) and a second AlN layer (212) sequentially laminated, a roughness of a surface of the second AlN layer (212) remote from the substrate (10) being not less than a roughness of a surface of the first AlN layer (211) remote from the substrate (10).

3. The led of claim 2, wherein the first AlN layer (211) has a thickness less than a thickness of the second AlN layer (212).

4. The led of claim 3, wherein the ratio of the thickness of said first AlN layer (211) to the thickness of said second AlN layer (212) is 1/6 to 1/2.

5. The light-emitting diode according to any one of claims 2 to 4, wherein the number of the AlN composite layers (210) is 2 to 5.

6. A preparation method of a light-emitting diode is characterized by comprising the following steps:

providing a substrate;

growing a buffer layer on the substrate, wherein the roughness of the surface of the buffer layer far away from the substrate is 5-6.5;

and growing an epitaxial layer on the buffer layer.

7. The method of claim 6, wherein growing a buffer layer on the substrate comprises:

controlling the power to be 3500 w-5000 w, introducing nitrogen gas with the flow rate of 300 sccm-500 sccm, introducing oxygen gas with the flow rate of 3 sccm-6 sccm, sputtering an Al target at the temperature of 450 ℃ to 550 ℃ for 10min to 15min to generate a first AlN layer;

controlling the power to be 2000 w-3000 w, the flow rate of the introduced nitrogen to be 300 sccm-500 sccm, the flow rate of the introduced oxygen to be 6 sccm-10 sccm, the time to be 5 min-10 min, the temperature to be 600 ℃ to 750 ℃, and sputtering the Al target to generate a second AlN layer to form an AlN composite layer.

8. The method of claim 7, wherein growing a buffer layer on the substrate further comprises:

after an AlN composite layer is formed, controlling the power to be 3000 w-4000 w, introducing nitrogen gas with the flow rate of 300 sccm-500 sccm, introducing oxygen gas with the flow rate of 3 sccm-6 sccm for 6 min-10 min, sputtering an Al target at the temperature of 500 ℃ to 600 ℃ to generate a first AlN layer;

controlling the power to be 2500w to 3000w, the flow rate of the introduced nitrogen to be 300sccm to 500sccm, the flow rate of the introduced oxygen to be 4sccm to 8sccm, the time to be 4min to 8min, the temperature to be 600 ℃ to 750 ℃, sputtering the Al target material to generate a second AlN layer, and forming another AlN composite layer.

9. The production method according to claim 6, wherein the buffer layer comprises 2 to 5 AlN composite layers stacked in this order, the AlN composite layers comprising a first AlN layer and a second AlN layer stacked in this order, and a surface of the second AlN layer remote from the substrate has a roughness not less than a roughness of a surface of the first AlN layer remote from the substrate.

10. The method according to any one of claims 6 to 9, wherein before growing the buffer layer on the substrate, the method comprises:

controlling the flow of Ar to be 400sccm to 800sccm for 3min to 5min;

the flow rate of Ar is reduced to 300sccm to 500sccm for 10min to 15min.

Images