A light emitting diode epitaxial structure and a preparation method thereof

Abstract

The application provides a light emitting diode epitaxial structure and a preparation method thereof, the method comprising: growing a buffer layer, a three-dimensional nucleation layer, an undoped GaN layer, an N-type composite AlGaN interlayer, an N-type GaN layer, an InGaN / GaN multi-quantum well layer, a P-type AlGaN electron blocking layer, a P-type GaN layer and a P-type contact layer on a substrate; or growing a buffer layer, a three-dimensional nucleation layer, an undoped GaN layer, an N-type GaN layer, an N-type composite AlGaN interlayer, an InGaN / GaN multi-quantum well layer, a P-type AlGaN electron blocking layer and a P-type GaN layer on a substrate; wherein the N-type composite AlGaN interlayer comprises a plurality of N-type Al x In y Ga 1‑x‑y N layers and N-type Al z Ga 1‑z N layers which are alternately stacked in sequence. By adjusting the content of In and Al in the InGaN / GaN multi-quantum well layer, the condition of lattice mismatching with the GaN layer and the AlGaN layer is avoided, and the splitting phenomenon is reduced. x In y Ga 1‑x‑y N layers which are alternately stacked in sequence. By adjusting the content of In and Al in the InGaN / GaN multi-quantum well layer, the condition of lattice mismatching with the GaN layer and the AlGaN layer is avoided, and the splitting phenomenon is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the chip technical field, in particular to a light emitting diode epitaxial structure and a preparation method thereof. BACKGROUND

[0002] A light emitting diode (LED) is a kind of semiconductor solid light emitting device, which can directly convert electricity into light by using a semiconductor PN junction as a light emitting material. GaN-based light emitting diodes (LEDs) are widely used in daily lighting, mobile phone backlight, automobile lamp and other fields. The preparation of LED epitaxial wafer is an important link in the preparation of light emitting diodes. The GaN-based LED epitaxial wafer includes a substrate, a buffer layer, a three-dimensional nucleation layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well layer, a P-type electron blocking layer and a P-type ohmic contact layer which are sequentially stacked on the substrate. The multi-quantum well layer includes alternately grown InGaN potential well layers and GaN potential barrier layers, and the P-type electron blocking layer is a P-type AlGaN layer.

[0003] In the prior art, the N-type AlGaN insertion layer in the light emitting diode epitaxial structure is generally arranged between the undoped GaN layer and the N-type GaN layer. Because the effective mass of electrons is smaller than that of holes, under the condition of large current operation, the LED will appear electron overflow, and the electrons will run to the P-type GaN layer to appear non-radiative recombination. The N-type AlGaN insertion layer in the epitaxial structure can increase the height of the potential barrier, reduce the electron overflow and improve the recombination efficiency of the carriers in the quantum well active region. In addition, the N-type AlGaN insertion layer can become a carrier accumulation layer, and the accumulated carriers rapidly spread in the two-dimensional plane to enhance the anti-static breakdown capability. Therefore, the basic method for enhancing the electrical characteristics of the traditional N-type AlGaN insertion layer is to increase the Al ratio of the AlGaN layer and to thicken the AlGaN layer. However, the lattice mismatch between the AlGaN layer and the GaN material will cause two serious consequences:

[0004] Firstly, the lattice mismatch between the AlGaN potential material layer and the GaN material causes a large number of dislocations caused by lattice mismatch, which greatly reduces the crystalline quality of the potential barrier layer and the heterojunction interface quality. A higher Al component N-type AlGaN insertion layer or a thicker N-type AlGaN insertion layer will further increase the alloy disorder scattering and interface roughness, thereby reducing the electrical characteristics of the LED.

[0005] Secondly, due to the serious lattice mismatch, the AlGaN layer under strain will introduce compressive stress, which will affect the warping change of the epitaxial wafer, leading to an increase in the warping of the epitaxial wafer when growing to the N-type AlGaN insertion layer. More seriously, the wafer may be cracked due to the severe warping. SUMMARY

[0006] Based on this, the purpose of the present application is to provide a light emitting diode epitaxial structure and a preparation method thereof, which are used to solve the technical problems of low electrical performance of the epitaxial wafer and easy occurrence of increased warping during growth of the epitaxial wafer due to the lattice mismatch between the AlGaN layer and the GaN layer in the prior art.

[0007] In one aspect, the present application provides a light emitting diode epitaxial structure, comprising:

[0008] a substrate;

[0009] a buffer layer, a three-dimensional nucleation layer, an undoped GaN layer, an N-type GaN layer, an InGaN / GaN multi-quantum well layer, a P-type AlGaN electron blocking layer, a P-type GaN layer, and a P-type contact layer, which are sequentially stacked on the substrate;

[0010] The epitaxial structure further comprises an N-type composite AlGaN interlayer, which is arranged between the undoped GaN layer and the N-type GaN layer, or between the N-type GaN layer and the InGaN / GaN multi-quantum well layer;

[0011] The N-type composite AlGaN interlayer comprises a plurality of N-type Al x In y Ga 1-x-y N layers and N-type Al z Ga 1-z N layers which are alternately stacked, wherein 0 < x < 1, 0 < y < 1, x + y ≤ 1, z < x, the N-type GaN layer and the undoped GaN layer are respectively in contact with the N-type Al x In y Ga 1-x-y N layers in the N-type composite AlGaN interlayer, or the N-type GaN layer and the InGaN / GaN multi-quantum well layer are respectively in contact with the N-type Al x In y Ga 1-x-y N layers in the N-type composite AlGaN interlayer.

[0012] In another aspect, the present application provides a light emitting diode epitaxial structure preparation method, which is used to manufacture the above-mentioned light emitting diode epitaxial structure, and the method comprises:

[0013] obtaining a substrate;

[0014] growing a buffer layer, a three-dimensional nucleation layer, an undoped GaN layer, an N-type composite AlGaN interlayer, an N-type GaN layer, an InGaN / GaN multi-quantum well layer, a P-type AlGaN electron blocking layer, a P-type GaN layer, and a P-type contact layer on the substrate in sequence;

[0015] Alternatively, a buffer layer, a three-dimensional nucleation layer, an undoped GaN layer, an N-type GaN layer, an N-type composite AlGaN insertion layer, an InGaN / GaN multiple quantum well layer, a P-type AlGaN electron blocking layer, a P-type GaN layer, and a P-type contact layer may be grown sequentially on the substrate.

[0016] The process of growing the N-type composite AlGaN insertion layer includes:

[0017] Multiple N-type Al layers are stacked alternately in sequence. x In y Ga 1-x-y N-layer and N-type Al z Ga 1-z N layers are used to grow the N-type composite AlGaN insertion layer.

[0018] The above-mentioned epitaxial structure of light-emitting diodes and its fabrication method have the following beneficial effects:

[0019] 1. The light-emitting diode epitaxial structure with a high-Al-content N-type composite AlGaN intercalation layer described in this invention, wherein the N-type composite AlGaN intercalation layer is composed of alternately grown N-type Al... x In y Ga 1-x-y N-layer and N-type Al z Ga 1-z In the N-layer, because Al has a smaller atomic number while In has a larger atomic number, Al... x In y Ga 1-x-y The lattice constant of N has a large adjustable range; by adjusting the content of In and Al components, N-type Al... x In y Ga 1-x-y The N-layer enables it to interact with GaN layers and N-type Al. z Ga 1-z The mismatch in the lattice constant of the three N layers on the c-plane is completely eliminated. In the AlInGaN / AlGaN / AlInGaN / GaN heterojunction epitaxial structure with no lattice mismatch, the introduced compressive stress also disappears, the warpage of the epitaxial wafer is improved, and the cracking phenomenon is reduced.

[0020] 2. The light-emitting diode epitaxial structure with a high-Al-content N-type composite AlGaN intercalation layer described in this invention, wherein the N-type composite AlGaN intercalation layer is composed of alternately grown N-type Al... x In y Ga 1-x-y N-layer and N-type Al z Ga 1-z N layers, with N-type Al x Iny Ga 1-x- y N layer and N-type Al z Ga 1-z N layer is grown alternately, In component is gradually increased, there are a small amount of In atoms without incorporation, In is added, surface N free bond is saturated, thereby reducing surface energy of the surface, improving migration rate of Ga atoms on the surface, promoting two-dimensional growth, and enhancing the ability to fill V-shaped pits. x In y Ga 1-x-y N layer and N-type Al z Ga 1-z N layer surface is more flat, and interface roughness is reduced.

[0021] 3. The light emitting diode epitaxial structure with high Al component N-type composite AlGaN insertion layer according to the present application, wherein the N-type composite AlGaN insertion layer is alternately grown N-type Al x In y Ga 1-x-y N layer and N-type Al z Ga 1-z N layer, thin N-type Al is alternately grown x In y Ga 1-x-y N layer and thin N-type Al z Ga 1-z N layer can grow Al atoms arranged more regular, N-type Al x In y Ga 1-x-y N layer and N-type Al z Ga 1-z N layer interface is more flat, and the surface pits are less, and the total thickness of the N-type Al is unchanged x In y Ga 1-x-y N layer and N-type Al z Ga 1-z N layer.

[0022] In addition, the light emitting diode epitaxial structure and the preparation method thereof according to the present application can have the following additional technical features:

[0023] Further, the N-type GaN layer comprises a first N-type GaN layer and a second N-type GaN layer grown adjacently, the N-type composite AlGaN insertion layer is arranged between the first N-type GaN layer and the second N-type GaN layer, and the first N-type GaN layer and the second N-type GaN layer are respectively in contact with N-type Al in the N-type composite AlGaN insertion layer. x In y Ga 1-x-y N layer is laminated in contact.

[0024] Further, the N-type composite AlGaN interlayer comprises n+1 layers of N-type Al x In y Ga 1-x-y N layers and n layers of N-type Al z Ga 1-z N layers, wherein 3≤n≤20, n∈N + , N + is a positive integer.

[0025] Further,

[0026] The N-type Al x In y Ga 1-x-y N layer has a thickness of 0.5-10 nm;

[0027] The N-type Al z Ga 1-z N layer has a thickness of 1-10 nm.

[0028] Further, the concentration of dopants in the N-type composite AlGaN interlayer is less than the concentration of dopants in the N-type GaN layer.

[0029] Further, the concentration of dopants in the N-type composite AlGaN interlayer ranges from 1×E 17 atoms / cm 3 to 1×E 19 atoms / cm 3 .

[0030] Further, the N-type Al x In y Ga 1-x-y N layer and the N-type Al z Ga 1-z N layer have the same growth temperature, atmosphere, and reaction chamber pressure.

[0031] Further, in the N-type Al x In y Ga 1-x-y N layer, the Al component content gradually decreases with increasing alternating growth cycles, and the In component content gradually increases with increasing alternating growth cycles. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a schematic diagram of an epitaxial structure of a light emitting diode in the first embodiment of the present application;

[0033] Figure 2 is a schematic diagram of an epitaxial structure of a light emitting diode in the second embodiment of the present application;

[0034] Figure 3 Schematic diagram of the light emitting diode epitaxial structure in the third embodiment of the present application;

[0035] Figure 4 Schematic diagram of the light emitting diode epitaxial structure in the comparative example of the present application.

[0036] Explanation of main structure symbols:

[0037]

[0038] The following detailed description will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0039] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The drawings show several embodiments of the present application. However, the present application can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description of the present application herein only for the purpose of describing specific embodiments and is not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more of the associated listed items.

[0041] The present application provides a light emitting diode epitaxial structure preparation method, specifically a LED epitaxial structure preparation method with high Al component N-type composite AlGaN insertion layer, for making LED epitaxial structure with high Al component N-type composite AlGaN insertion layer, the main technical features of the present application scheme are:

[0042] 1. The N-type composite AlGaN insertion layer is an N-type Al x In y Ga 1-x-y N layer and an N-type Al z Ga 1-z N layer, which introduces an Al x In y Ga 1-x-Y N quaternary alloy nitride, and the Al component of the N-type Al x In y Ga 1-x-y N layer is higher than that of the N-type Al z Ga 1- zThe N layer can optimize the lattice mismatch with the GaN layer and the AlGaN layer by adjusting the content of In component and Al component, thereby improving the warping of the epitaxial wafer and reducing the wafer cracking phenomenon.

[0043] 2. The N-type composite AlGaN interlayer introduces In atoms, and as the N-type Al x In y Ga 1-x-y N layer and the N-type Al z Ga 1- z The N layer is alternately grown, and the In component gradually increases, and the small amount of In atoms not incorporated can act as a surface activator, reduce the surface energy, improve the surface migration rate of Ga atoms, promote two-dimensional growth, so that the AlInGaN layer and the AlGaN layer are more flat, and the interface roughness is reduced.

[0044] 3. The N-type composite AlGaN interlayer is alternately grown with a high Al component and a thin N-type Al x In y Ga 1-x-y N layer and the N-type Al z Ga 1-z N layer, so that the N-type Al x In y Ga 1-x-y N layer and the N-type Al z Ga 1-z N layer can be grown with less surface pits, a smoother interface, and an unchanged total thickness.

[0045] The embodiment of the present application aims at the technical problem that the lattice mismatch between the AlGaN layer and the GaN layer leads to low electrical performance of the epitaxial wafer and easy warping increase during growth of the epitaxial wafer in the prior art, and specifically provides a light emitting diode epitaxial structure and a preparation method thereof, wherein the method comprises:

[0046] obtaining a substrate;

[0047] growing a buffer layer, a three-dimensional nucleation layer, an undoped GaN layer, an N-type composite AlGaN interlayer, an N-type GaN layer, an InGaN / GaN multi-quantum well layer, a P-type AlGaN electron blocking layer, a P-type GaN layer, and a P-type contact layer on the substrate in sequence;

[0048] or growing a buffer layer, a three-dimensional nucleation layer, an undoped GaN layer, an N-type GaN layer, an N-type composite AlGaN interlayer, an InGaN / GaN multi-quantum well layer, a P-type AlGaN electron blocking layer, a P-type GaN layer, and a P-type contact layer on the substrate in sequence;

[0049] wherein when the N-type composite AlGaN interlayer is grown, it comprises:

[0050] a plurality of N-type Al x In y Ga 1-x-y N layers and N-type Al z Ga 1-z N layers are alternately stacked to grow the N-type composite AlGaN interlayer.

[0051] In some embodiments of the present application, the concentration of dopants in the N-type composite AlGaN interlayer is less than the concentration of dopants in the N-type GaN layer; the concentration of dopants in the N-type composite AlGaN interlayer ranges from 1 x E 17 atoms / cm 3 ~ 1 x E 19 atoms / cm 3 ; the growth temperature, atmosphere, and reaction chamber pressure of the N-type Al x In y Ga 1-x-y N layer and the N-type Al z Ga 1-z N layer are the same; in the N-type Al x In y Ga 1-x-y N layer, the Al component content gradually decreases with the increase of the alternating growth period, and the In component content gradually increases with the increase of the alternating growth period.

[0052] Specifically, the light emitting diode epitaxial structure comprises:

[0053] a substrate, a buffer layer, a three-dimensional nucleation layer, an undoped GaN layer, an N-type GaN layer, an InGaN / GaN multi-quantum well layer, a P-type AlGaN electron blocking layer, a P-type GaN layer, and a P-type contact layer are sequentially stacked, and further comprising an N-type composite AlGaN interlayer, the N-type composite AlGaN interlayer is arranged between the undoped GaN layer and the N-type GaN layer, or arranged between the N-type GaN layer and the InGaN / GaN multi-quantum well layer;

[0054] The N-type composite AlGaN interlayer comprises a plurality of N-type Al x In y Ga 1-x-y N layers and N-type Al z Ga 1-z N layers, wherein 0 < x < 1, 0 < y < 1, x + y ≤ 1, and z < x, the N-type GaN layer and the undoped GaN layer are respectively arranged between the N-type Al x In y Ga 1-x-y layers in the N-type composite AlGaN interlayer.N-type GaN layer and the InGaN / GaN multi-quantum well layer respectively contact with N-type Al in the N-type composite AlGaN interposed layer x In y Ga 1-x-y N layer.

[0055] In some alternative embodiments, the N-type GaN layer comprises a first N-type GaN layer and a second N-type GaN layer grown adjacently, the N-type composite AlGaN interposed layer is disposed between the first N-type GaN layer and the second N-type GaN layer, the first N-type GaN layer and the second N-type GaN layer respectively contact with N-type Al in the N-type composite AlGaN interposed layer x In y Ga 1-x-y N layer.

[0056] In the present application, the N-type composite AlGaN interposed layer is the N-type Al x In y Ga 1-x-y N layer and the N-type Al z Ga 1- z N layer, the thin N-type Al x In y Ga 1-x-y N layer and the thin N-type Al z Ga 1-z N layer can grow Al atoms more regular, the N-type Al x In y Ga 1-x-y N layer and the N-type Al z Ga 1-z N layer interface is more smooth, the total thickness of the N-type Al x In y Ga 1-x-y N layer and the N-type Al z Ga 1-z N layer, so the Al component can be higher on the premise of more smooth interface and better crystal quality, thereby improving the N-type Al z Ga 1-z N layer band gap and barrier height, really just block the electron overflow in the N-type GaN layer, and will not gather electrons to cause no electron gathering in the multi-quantum well layer.

[0057] Further, the N-type Al x In y Ga 1-x-y N layer and the N-type Al z Ga 1-zN layer, because the atomic coefficient of Al is smaller, and the atomic coefficient of In is larger, Al x In y Ga 1-x-y The lattice constant of N has a large adjustable range, by adjusting the content of In component and Al component, Al x In y Ga 1-x-y N can make it with GaN layer and N type Al z Ga 1-z N layer three produce in the c plane a axis lattice constant mismatching case completely disappears, in the lattice mismatching AlInGaN / AlGaN / AlInGaN / GaN heterojunction epitaxial structure, the compressive stress introduced by it also does not exist, the warping of the epitaxial wafer can be improved in the N type GaN layer with the thickest growth thickness, and then the probability of the cracking phenomenon is also reduced.

[0058] As a specific example, the N type composite AlGaN insertion layer includes n+1 layer N type Al x In y Ga 1-x-y N layer and n layer N type Al z Ga 1-z N layer, wherein 3≤n≤20, n∈N + , N + is a positive integer. Wherein, the thickness of the N type Al x In y Ga 1-x-y N layer is 0.5-10nm; the thickness of the N type Al z Ga 1-z N layer is 1-10nm.

[0059] In order to facilitate understanding of the present application, several embodiments of the present application will be given below. However, the present application can be realized in many different forms, and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0060] Embodiment 1

[0061] Please refer to Figure 1 , which is a schematic diagram of the light emitting diode epitaxial structure in the embodiment one of the present application, including substrate 1, and buffer layer 2, three-dimensional nucleation layer 3, undoped GaN layer 4, N type composite AlGaN insertion layer 5 (wherein, N type Al x In y Ga 1-x-y N layer 51, N type Al z Ga 1-zN-type GaN layer 6, InGaN / GaN multi-quantum well layer 7, P-type AlGaN electron blocking layer 8, P-type GaN layer 9, P-type contact layer 10.

[0062] In the embodiment, the epitaxial wafer is grown by using a MOCVD (Metal-organic Chemical Vapor Deposition) device. High-purity NH3 is used as the N source, TMGa and TEGa are used as the Ga source, TMIn is used as the In source, TMAl is used as the Al source, SiH4 is used as the N-type dopant, and CP2Mg is used as the P-type dopant. High-purity H2, high-purity N2, and a mixed gas of high-purity H2 and high-purity N2 are used as the carrier gas of the MO source.

[0063] Specifically, the method for preparing the epitaxial structure of the light emitting diode comprises the following steps.

[0064] A substrate is obtained. The substrate includes, but is not limited to, sapphire, silicon, and silicon carbide. In the embodiment, sapphire is used as the growth substrate of the epitaxial layer.

[0065] A buffer layer is deposited on the substrate. The buffer layer can be an AlN / GaN / AlGaN buffer layer. In the embodiment, the buffer layer is a GaN layer. Specifically, the temperature of the reaction chamber is controlled at 760-900 ℃, the pressure is controlled at 100-200 torr, the rotation speed of the graphite base is controlled at 800-1000 rpm, and the thickness of the GaN buffer layer is 10 nm.

[0066] A three-dimensional nucleation layer is deposited on the buffer layer. Specifically, the temperature of the reaction chamber is increased to 1060-1090 ℃, the pressure of the reaction chamber is controlled at 150-200 torr, the rotation speed of the graphite base is reduced to 700-900 rpm, and a three-dimensional nucleation layer with a thickness of 500 nm is grown.

[0067] An undoped GaN layer is deposited on the three-dimensional nucleation layer. Specifically, the temperature of the reaction chamber is increased to 1100-1125 ℃, the pressure of the reaction chamber is controlled at 150-200 torr, the rotation speed of the graphite base is controlled at 1000-1200 rpm, and an undoped GaN layer with a thickness of 2 um is grown.

[0068] An N-type composite AlGaN insertion layer was deposited on an undoped GaN layer. Specifically, on the undoped GaN layer, the reaction chamber temperature was reduced to 950-1050℃ under an N2 atmosphere, the reaction chamber pressure was controlled at 70-100 torr, and the graphite substrate rotation speed was controlled at 500-800 rpm. TMGa was used as the Ga source, TMIn as the In source, TMAl as the Al source, and NH3 as the N source. Under this chamber environment, 120-300 sccm of TMAl was introduced, and 30-600 sccm of TMIn was introduced before, simultaneously with, or after the introduction of TMAl to grow an N-type Al layer with a thickness of 0.5-10 nm. x InyGa 1-x-y The N-layer has a Si doping concentration of 1.5 × E. 18 atoms / cm 3 -8×E 18 atoms / cm 3 ;

[0069] Specifically, in the growth of N-type Al x In y Ga 1-x-y N-type Al deposited on N layer z Ga 1-z N-layer, keeping the current chamber environment unchanged (reaction chamber pressure, N2 atmosphere, graphite disk rotation speed all unchanged), introduce 50-116 sccm of TMAl, and turn off TMIn to grow N-type Al with a thickness of 1-10 nm. z Ga 1-z The N-layer has a Si doping concentration of 1.5 × E. 18 atoms / cm 3 -8×E 18 atoms / cm 3 ;

[0070] Specifically, N-type Al x InyGa 1-x-y N-layer and N-type Al z Ga 1-z N-layer alternating growth for 3-20 growth cycles, N-type Al x In y Ga 1-x-y N-layer ratio N-type Al z Ga 1-z The number of N layers is one more, including N-type Al. x In y Ga 1-x-y The TMIn flow rate of layer N increases by 2.5% with each alternating growth cycle.

[0071] The insertion layer of the present application is N-type composite AlGaN insertion layer, which is inclined to two-dimensional growth, because Al x In y Ga 1-x-y N layer, the TMIn flow rate increases by 2.5% with the increase of the alternate growth cycle, there are a small amount of In atoms not incorporated, the addition of In, the saturation of surface N free bond, thus reducing the surface energy of the surface, improving the mobility of Ga atoms on the surface, promoting two-dimensional growth, enhancing the ability to fill V-shaped pits, making the N-type Al x In y Ga 1-x-y N layer and N-type Al z Ga 1-z N layer surface is more flat, the interface roughness is reduced, the crystal quality is improved, and the photoelectricity of the LED is improved.

[0072] Growth of N-type GaN layer on N-type composite AlGaN insertion layer. Specifically, the reaction chamber temperature is reduced to 1095-1100℃, the pressure is controlled at 200-250torr, the graphite base rotation speed is controlled at 1000-1200rpm, the N-type GaN layer with a thickness of 2um is grown, and the Si doping concentration is 1×E 19 atoms / cm 3 -1×E 20 atoms / cm 3 .

[0073] Deposition of M alternately grown multi-quantum well layers on the N-type GaN layer. Specifically, the reaction chamber temperature is reduced to 790-900℃, the pressure is controlled at 200-250torr, the graphite base rotation speed is controlled at 500-1600rpm, the InGaN quantum well layer and the GaN quantum barrier layer are alternately stacked, wherein the growth temperature of the InGaN quantum well layer is 790℃~810℃, the growth temperature of the GaN quantum barrier layer is 860℃~900℃, and the growth thickness is 12nm~16nm, wherein 5≤M≤9, M is a positive integer.

[0074] Deposition of P-type AlGaN electron blocking layer on the multi-quantum well layer. Specifically, the reaction chamber temperature is 950℃, the pressure is 100torr, the graphite disc rotation speed of the substrate is 1000rpm, and the P-type AlGaN electron blocking layer with a thickness of 10nm-60nm is grown.

[0075] Deposition of P-type GaN layer on the P-type AlGaN electron blocking layer. Specifically, the reaction chamber temperature is 980℃, the pressure is 200torr, the graphite disc rotation speed of the substrate is 1000rpm, and the P-type GaN layer with a thickness of 90nm-120nm is grown, wherein the Mg doping concentration is 1.8×E19 atoms / cm2 3 .

[0076] A P-type contact layer is deposited on the P-type GaN layer. Specifically, the reaction chamber temperature is 880°C, the pressure is 200 torr, the graphite disc carrying the substrate rotates at 1200 rpm, and a heavily Mg-doped GaN layer with a thickness of 1-8 nm is grown, wherein the Mg doping concentration is 5×E 20 atoms / cm2 3 .

[0077] Example 2

[0078] Referring to Figure 2 , a schematic diagram of an epitaxial structure of a light emitting diode according to the second embodiment of the present application is shown, which includes a substrate 1, and a buffer layer 2, a three-dimensional nucleation layer 3, an undoped GaN layer 4, a first N-type GaN layer 61, an N-type Al x In y Ga 1-x-y N layer 51, an N-type Al z Ga 1-z N layer 52, a second N-type GaN layer 62, an InGaN / GaN multi-quantum well layer 7, a P-type AlGaN electron blocking layer 8, a P-type GaN layer 9, and a P-type contact layer 10, which are epitaxially grown on the substrate 1 in sequence.

[0079] In this embodiment, a MOCVD (Metal-organic Chemical Vapor Deposition) device of Mica A7 is used to grow the epitaxial wafer. High-purity NH3 is used as the N source, TMGa and TEGa are used as the Ga source, TMIn is used as the In source, TMAl is used as the Al source, SiH4 is used as the N-type dopant, and CP2Mg is used as the P-type dopant. High-purity H2, high-purity N2, and a mixture of high-purity H2 and high-purity N2 are used as the carrier gas of the MO source.

[0080] In this embodiment, a first N-type GaN layer is deposited on the undoped GaN layer. Specifically, the reaction chamber temperature is reduced to 1095-1100°C, the pressure is controlled to be 200-250 torr, the graphite base rotates at 1000-1200 rpm, and a first N-type GaN layer with a thickness of 0.5-1.5 um is grown, wherein the Si doping concentration is 1×E 19 atoms / cm2 3 / cm3-1.5×E 20 atoms / cm2 3 .

[0081] An N-type composite AlGaN insertion layer is deposited on the first N-type GaN layer. Specifically, on the first N-type GaN layer, the reaction chamber temperature is reduced to 950-1050℃ under an N2 atmosphere, the reaction chamber pressure is controlled at 70-100 torr, and the graphite substrate rotation speed is controlled at 500-800 rpm. TMGa is used as the Ga source, TMIn as the In source, TMAl as the Al source, and NH3 as the N source. Under this chamber environment, 120-300 sccm of TMAl is introduced. Before, simultaneously with, or after the introduction of TMAl, 30-600 sccm of TMIn is introduced to grow an N-type Al layer with a thickness of 0.5-10 nm. x In y Ga 1-x-y The N-layer has a Si doping concentration of 1.5 × E. 18 atoms / cm 3 -8×E 18 atoms / cm 3 .

[0082] Specifically, in the growth of N-type Al x InyGa 1-x-y N-type Al deposited on N layer z Ga 1-z With N layers maintained and the current chamber environment unchanged (reaction chamber pressure, N2 atmosphere, and graphite disk rotation speed all unchanged), 50-116 sccm of TMAl is introduced, while the TMIn growth of N-type Al with a thickness of 1-10 nm is turned off. z Ga 1-z The N-layer has a Si doping concentration of 1.5 × E. 18 atoms / cm 3 -8×E 18 atoms / cm 3 ;

[0083] Specifically, N-type Al x In y Ga 1-x-y N-layer and N-type Al z Ga 1-z N-layer alternating growth for 3-20 growth cycles, N-type Al x In y Ga 1-x-y N-layer ratio N-type Al z Ga 1-z The number of N layers is one more; among them, N-type Al x In y Ga 1-x-y The TMIn flow rate of layer N increases by 2.5% with each alternating growth cycle.

[0084] A second N-type GaN layer is deposited on the N-type composite AlGaN interlayer, specifically, the temperature of the reaction chamber is reduced to 1095-1100℃, the pressure is controlled at 200-250torr, the rotation speed of the graphite base is controlled at 1000-1200rpm, and a second N-type GaN layer with a thickness of 0.5-1.5um is grown, the Si doping concentration is 1×E 19 atoms / cm 3 -1.5×E 20 atoms / cm 3 .

[0085] Example 3

[0086] Please refer to Figure 3 , which is a schematic diagram of the epitaxial structure of the light emitting diode in Example 3 of the present application, including a substrate 1, and a buffer layer 2, a three-dimensional nucleation layer 3, an undoped GaN layer 4, an N-type GaN layer 6, an N-type composite AlGaN interlayer 5 (wherein the N-type Al X In y Ga 1-x-y N layer 51, N-type Al z Ga 1-z N layer 52), an InGaN / GaN multi-quantum well layer 7, a P-type AlGaN electron blocking layer 8, a P-type GaN layer 9, and a P-type contact layer 10, which are epitaxially grown on the substrate in sequence.

[0087] In this embodiment, a MOCVD (Metal-organic Chemical Vapor Deposition) device of Micro-A7 is used to grow the epitaxial wafer. High-purity NH3 is used as the N source, TMGa and TEGa are used as the Ga source, TMIn is used as the In source, TMAl is used as the Al source, SiH4 is used as the N-type dopant, and CP2Mg is used as the P-type dopant. High-purity H2, high-purity N2, and a mixture of high-purity H2 and high-purity N2 are used as the carrier gas of the MO source.

[0088] In this embodiment, N-type AlGaN interlayer is deposited on N-type GaN layer. Specifically, on the N-type GaN layer, the temperature of the reaction chamber is reduced to 950-1050°C under N2 atmosphere, the pressure of the reaction chamber is controlled at 70-100 torr, the rotation speed of the graphite base is controlled at 500-800 rpm, TMGa is used as Ga source, TMIn is used as In source, TMAl is used as Al source, and NH3 is used as N source. Under the cavity environment, 120-300 sccm of TMAl is introduced, and 30-600 sccm of TMIn is introduced before, at the same time or after the introduction of TMAl to grow N-type Al x In y Ga 1-x-y N layer, the doping concentration of Si is 1.5×E 18 atoms / cm 3 -8×E 18 atoms / cm 3 ;

[0089] Specifically, N-type Al x In y Ga 1-x-y N layer is deposited on the grown N-type Al z Ga 1-z N layer, the current cavity environment is maintained unchanged (the reaction chamber pressure, N2 atmosphere, and rotation speed of the graphite disc are unchanged), 50-116 sccm of TMAl is introduced, and TMIn is turned off to grow N-type Al z Ga 1-z N layer with a thickness of 1-10 nm, and the doping concentration of Si is 1.5×E 18 atoms / cm 3 -8×E 18 atoms / cm 3 ;

[0090] Specifically, N-type Al x In y Ga 1-x-y N layer and N-type Al z Ga 1-z N layer are alternately grown for 3-20 growth cycles, and the number of N-type Al x In y Ga 1-x-y N layers is one more than that of N-type Al z Ga 1-z N layers; wherein the TMIn flow rate of N-type Al x In y Ga 1-x-y N layer increases by 2.5% with the increase of the alternating growth cycles.

[0091] Depositing M alternately grown multi-quantum well layers on the N-type composite AlGaN interlayer, specifically, reducing the reaction chamber temperature to 790-900℃, controlling the pressure at 200-250 torr, and controlling the graphite base rotation speed at 500-1600 rpm, alternately stacking InGaN quantum well layers and GaN quantum barrier layers, wherein the growth temperature of the InGaN quantum well layer is 790℃-810℃, the growth temperature of the GaN quantum barrier layer is 860℃-900℃, and the growth thickness is 12nm-16nm, wherein 5≤M≤9, and M is a positive integer.

[0092] Comparative Example 1

[0093] Please refer to Figure 4 Comparative Example 1 is a conventional light emitting diode epitaxial structure with an N-type AlGaN interlayer, and the difference from the embodiment of the present application is that the N-type AlGaN is a single-layer interlayer with fixed Al composition, and there is no difference in other structures. Specifically, it includes a substrate 1, and a buffer layer 2, a three-dimensional nucleation layer 3, an undoped GaN layer 4, an N-type AlGaN layer 11, an N-type GaN layer 6, an InGaN / GaN multi-quantum well layer 7, a P-type AlGaN electron blocking layer 8, a P-type GaN layer 9, and a P-type contact layer 10, which are sequentially epitaxially grown on the substrate.

[0094] In this embodiment, a MOCVD (Metal-organic Chemical Vapor Deposition) device is used to grow the epitaxial wafer. High-purity NH3 is used as the N source, trimethylgallium (TMGa) and triethylgallium (TEGa) are used as the Ga source, trimethylindium (TMIn) is used as the In source, trimethylaluminum (TMAl) is used as the Al source, silane (SiH4) is used as the N-type dopant, and bis-cyclopentadienyl magnesium (CP2Mg) is used as the P-type dopant. High-purity H2 (hydrogen), high-purity N2 (nitrogen), and a mixture of high-purity H2 and high-purity N2 are used as the carrier gas for the MO source.

[0095] A substrate is provided, including but not limited to sapphire, silicon, and silicon carbide. In this comparative example, sapphire is used as the epitaxial layer growth substrate.

[0096] A buffer layer is deposited on the substrate. The buffer layer can be an AlN / GaN / AlGaN buffer layer.

[0097] In this comparative example, the buffer layer is a GaN layer, specifically, the temperature of the reaction chamber is controlled at 760-900℃, the pressure is controlled at 100-200 torr, and the graphite base rotation speed is controlled at 800-1000 rpm, and the thickness of the GaN buffer layer is 10nm.

[0098] Depositing a three-dimensional nucleation layer on the buffer layer. Specifically, the temperature of the reaction chamber is raised to 1060-1090℃, the pressure of the reaction chamber is controlled at 150-200 torr, the rotation speed of the graphite base is reduced to 700-900 rpm, and a three-dimensional nucleation layer with a thickness of 500 nm is grown.

[0099] Depositing an undoped GaN layer on the three-dimensional nucleation layer. Specifically, the temperature of the reaction chamber is raised to 1100-1125℃, the pressure of the reaction chamber is controlled at 150-200 torr, the rotation speed of the graphite base is controlled at 1000-1200 rpm, and an undoped GaN layer with a thickness of 2 um is grown.

[0100] Depositing an N-type AlGaN layer on the undoped GaN layer. Specifically, on the undoped GaN layer, the temperature of the reaction chamber is reduced to 950-1050℃ under N2 atmosphere, the pressure of the reaction chamber is controlled at 70-100 torr, the rotation speed of the graphite base is controlled at 500-800 rpm, TMGa is used as the Ga source, TMAl is used as the Al source, NH3 is used as the N source, 50-116 sccm of TMAl is introduced into the cavity environment, and an N-type AlGaN layer with a thickness of 4.5-400 nm is grown, with a Si doping concentration of 1.5×E 18 atoms / cm 3 -8×E 18 atoms / cm 3 .

[0101] Growth of an N-type GaN layer on the N-type AlGaN layer. Specifically, the temperature of the reaction chamber is reduced to 1095-1100℃, the pressure is controlled at 200-250 torr, the rotation speed of the graphite base is controlled at 1000-1200 rpm, an N-type GaN layer with a thickness of 2 um is grown, and the Si doping concentration is 1×E 19 atoms / cm 3 -1×E 20 atoms / cm 3 .

[0102] Depositing M alternatingly grown multi-quantum well layers on the N-type GaN layer. Specifically, the temperature of the reaction chamber is reduced to 790-900℃, the pressure is controlled at 200-250 torr, the rotation speed of the graphite base is controlled at 500-1600 rpm, and alternatingly stacked InGaN quantum well layers and GaN quantum barrier layers are grown, wherein the growth temperature of the InGaN quantum well layer is 790℃-810℃, the growth temperature of the GaN quantum barrier layer is 860℃-900℃, the growth thickness is 12 nm-16 nm, 5≤M≤9, and M is a positive integer.

[0103] A P-type AlGaN electron blocking layer is deposited on the multi-quantum well layer. Specifically, the reaction chamber temperature is 950 DEG C, the pressure is 100 torr, the graphite disc carrying the substrate rotates at 1000 rpm, and a P-type AlGaN electron blocking layer with a thickness of 10 nm-60 nm is grown.

[0104] A P-type GaN layer is deposited on the P-type AlGaN electron blocking layer. Specifically, the reaction chamber temperature is 980 DEG C, the pressure is 200 torr, the graphite disc carrying the substrate rotates at 1000 rpm, and a GaN layer with a thickness of 90 nm-120 nm is grown, wherein the Mg doping concentration is 1.8 x E 19 atoms / cm 3 .

[0105] A P-type contact layer is deposited on the P-type GaN layer. Specifically, the reaction chamber temperature is 880 DEG C, the pressure is 200 torr, the graphite disc carrying the substrate rotates at 1200 rpm, and a heavily Mg-doped GaN layer with a thickness of 1 nm-8 nm is grown, wherein the Mg doping concentration is 5 x E 20 atoms / cm 3 .

[0106] 100 pieces of epitaxial wafers are prepared according to the above-mentioned embodiment 1, embodiment 2, embodiment 3 and comparative example 1 respectively, the wafer warpage is measured by a flatness detection instrument, and the wafer breakage rate and the dislocation density at the center position of each epitaxial wafer are counted, and the results are shown in Table 1:

[0107] Table 1. Wafer warpage, dislocation density and wafer breakage rate data of the epitaxial wafers prepared by the method in the application and the comparative example

[0108]

[0109] From the above table, it can be seen that, compared with the comparative examples, the wafer warpage of the LED epitaxial structure prepared by the method of the application is reduced by 13%, 15% and 12% respectively, the dislocation density is reduced by 23%, 28% and 25% respectively, and the wafer breakage number is reduced by 89%, 83% and 100% respectively. Therefore, by comparing the wafer warpage and the wafer breakage number, it can be seen that the LED epitaxial structure preparation method in the application can improve the wafer warpage, reduce the wafer cracking and wafer breakage phenomenon, and by comparing the dislocation density, it can be seen that the LED epitaxial structure preparation method in the application can reduce the dislocation density of the epitaxial wafer, improve the crystal quality of the epitaxial wafer, and thus improve the electrical properties of the LED.

[0110] Compared with the prior art, the LED epitaxial structure provided by the application, specifically, the LED epitaxial structure with a high-Al-component N-type composite AlGaN insertion layer, has the following beneficial effects:

[0111] 1. The light emitting diode epitaxial structure with high Al component N-type composite AlGaN interlayer, the N-type composite AlGaN interlayer is the N-type Al x In y Ga 1-x-y N layer and the N-type Al z Ga 1-z N layer, since the atomic coefficient of Al is small, and the atomic coefficient of In is large, the lattice constant of Al x In y Ga 1-x-y N has a large adjustable range, by adjusting the content of In component and Al component, the N-type Al x In y Ga 1-x-y N layer can make the mismatch of the a-axis lattice constant in the c-plane of the three disappear, in the lattice mismatched AlInGaN / AlGaN / AlInGaN / GaN heterojunction epitaxial structure, the introduced compressive stress also does not exist, the warping of the epitaxial wafer is improved, and the wafer cracking phenomenon is also reduced. z Ga 1-z N layer.

[0112] 2. The light emitting diode epitaxial structure with high Al component N-type composite AlGaN interlayer, the N-type composite AlGaN interlayer is the N-type Al x In y Ga 1-x-y N layer and the N-type Al z Ga 1-z N layer, with the N-type Al x In y Ga 1-x- y N layer and the N-type Al z Ga 1-z N layer is alternately grown, the In component gradually increases, a small amount of In atoms not incorporated exists, the addition of In, the surface N free bond is saturated, thereby reducing the surface energy, improving the mobility of Ga atoms on the surface, promoting two-dimensional growth, enhancing the ability to fill V-shaped pits, and the N-type Al x In y Ga 1-x-y N layer and the N-type Al z Ga 1-z N layer surface is more flat, and the interface roughness is reduced.

[0113] 3. The light emitting diode epitaxial structure with high Al component N-type composite AlGaN interlayer according to the present application, the N-type composite AlGaN interlayer is the N-type Al x In y Ga 1-x-y N layer and N-type Al z Ga 1-z N layer, thin N-type Al x In y Ga 1-x-y N layer and thin N-type Al z Ga 1-z N layer can grow Al atom arrangement more regular, N-type Al x In y Ga 1-x-y N layer and N-type Al z Ga 1-z N layer interface is more flat, the total thickness of the surface pits less N-type Al x In y Ga 1-x-y N layer and N-type Al z Ga 1-z N layer.

[0114] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0115] The above-described embodiments only express several implementation manners of the present application, which are described in a more specific and detailed manner, but cannot be understood as the limitation of the patent scope of the present application. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, which are all within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A light-emitting diode epitaxial structure, comprising a substrate, a buffer layer, a three-dimensional nucleation layer, an undoped GaN layer, an N-type GaN layer, an InGaN / GaN multiple quantum well layer, a P-type AlGaN electron blocking layer, a P-type GaN layer, and a P-type contact layer stacked sequentially, characterized in that, It also includes an N-type composite AlGaN insertion layer, which is disposed between the undoped GaN layer and the N-type GaN layer, or between the N-type GaN layer and the InGaN / GaN multiple quantum well layer; The N-type composite AlGaN insertion layer comprises multiple N-type Al atoms stacked in an alternating manner. x In y Ga 1-x-y N-layer and N-type Al z Ga 1- z N layers, where 0 < x < 1, 0 < y < 1, x + y ≤ 1, z < x, wherein the N-type GaN layer and the undoped GaN layer are respectively inserted into the N-type Al in the N-type composite AlGaN insertion layer. x In y Ga 1-x-y N-layer stacked contact, or the N-type GaN layer and the InGaN / GaN multiple quantum well layer respectively contact the N-type Al in the N-type composite AlGaN insertion layer. x In y Ga 1-x-y N-layer stacked contact; The N-type GaN layer includes a first N-type GaN layer and a second N-type GaN layer grown adjacently, and the N-type composite AlGaN insertion layer is disposed between the first N-type GaN layer and the second N-type GaN layer. The first N-type GaN layer and the second N-type GaN layer are respectively connected to the N-type Al in the N-type composite AlGaN insertion layer. x In y Ga 1-x-y N-layer stacked contact.

2. The light-emitting diode epitaxial structure according to claim 1, characterized in that, The N-type composite AlGaN insertion layer includes n+1 layers of N-type Al x In y Ga 1-x-y N-layer and n-layer N-type Al z Ga 1-z N layers, where 3≤n≤20, n∈N + N + It is a positive integer.

3. The light-emitting diode epitaxial structure according to claim 1, characterized in that, The N-type Al x In y Ga 1-x-y The thickness of the N layer is 0.5–10 nm; The N-type Al z Ga 1-z The thickness of the N layer is 1–10 nm.

4. A method for fabricating an epitaxial structure of a light-emitting diode, characterized in that, The method for fabricating the light-emitting diode epitaxial structure according to any one of claims 1-3 includes: Obtain a substrate; A buffer layer, a three-dimensional nucleation layer, an undoped GaN layer, an N-type composite AlGaN insertion layer, an N-type GaN layer, an InGaN / GaN multiple quantum well layer, a P-type AlGaN electron blocking layer, a P-type GaN layer, and a P-type contact layer are sequentially grown on the substrate. Alternatively, a buffer layer, a three-dimensional nucleation layer, an undoped GaN layer, an N-type GaN layer, an N-type composite AlGaN insertion layer, an InGaN / GaN multiple quantum well layer, a P-type AlGaN electron blocking layer, a P-type GaN layer, and a P-type contact layer may be grown sequentially on the substrate. The process of growing the N-type composite AlGaN insertion layer includes: Multiple N-type Al layers are stacked alternately in sequence. x In y Ga 1-x-y N-layer and N-type Al z Ga 1-z N layers are used to grow the N-type composite AlGaN insertion layer.

5. The method for fabricating a light-emitting diode epitaxial structure according to claim 4, characterized in that, The concentration of dopant in the N-type composite AlGaN insertion layer is lower than the concentration of dopant in the N-type GaN layer.

6. The method for fabricating a light-emitting diode epitaxial structure according to claim 5, characterized in that, The concentration range of the dopant in the N-type composite AlGaN insertion layer is 1×E. 17 atoms / cm 3 ~1×E 19 atoms / cm 3 .

7. The method for fabricating a light-emitting diode epitaxial structure according to claim 4, characterized in that, The N-type Al x In y Ga 1-x-y N-layer and the N-type Al z Ga 1-z The growth temperature, atmosphere, and reaction chamber pressure of the N-layer are the same.

8. The method for fabricating a light-emitting diode epitaxial structure according to claim 4, characterized in that, In the N-type Al x In y Ga 1-x-y In the N layer, the content of Al components gradually decreases with the increase of alternating growth cycles.

9. The method for fabricating a light-emitting diode epitaxial structure according to claim 8, characterized in that, In the N-type Al x In y Ga 1-x-y In the N layer, the In component content gradually increases with the increase of alternating growth cycles.

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