AlGaN-based UVB epitaxial wafer structure and preparation method thereof

Abstract

The invention belongs to the technical field of ultraviolet LED chips, and particularly relates to an AlGaN-based UVB epitaxial wafer structure and a preparation method thereof, and the preparation method comprises the following steps: preparing a 5nm-30nm AlN buffer layer on the surface of a sapphire substrate; placing the sapphire substrate prepared with the AlN buffer layer in MOCVD (Metal Organic Chemical Vapor Deposition) to grow a structural layer; growing a 3D AlGaN layer; growing a 2D AlGaN layer; a growth component is an AlGaN layer of 50%-60%; a nAlGaN layer doped with Si is grown; growing a multi-quantum well active layer; growing an EBL layer; growing a hole injection layer; and growing a hole supply layer. According to the invention, through reasonable setting of gradual change of components of the last two pairs of quantum wells, growth of fixed single-component quantum wells is realized, spatial separation of electron and hole wave functions is reduced, carrier radiation coincidence efficiency is improved, and the proportion of effective wave band integral area and total wave spectrum integral area is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of ultraviolet LED chips, and in particular relates to an AlGaN-based UVB epitaxial wafer structure and a preparation method thereof. Background Art

[0002] Traditional AlGaN-based UVB epitaxial structures all grow AlGaN materials on the substrate material of the AlN template. The AlN template is the substrate material for the epitaxial growth of AlGaN-based deep ultraviolet LEDs. The crystal quality of the template directly determines the crystal quality of the upper AlGaN. High-quality AlN templates can effectively reduce the threading dislocation density (TDDs) of AlGaN, improve the radiation recombination efficiency of electrons and holes in the LED structure grown on this material, and improve the reliability and life of the LED.

[0003] The AlGaN-based material is grown on the surface of the AlN template, which is a heterogeneous material epitaxial growth. There is a lattice mismatch between the two. The size of the lattice mismatch is related to the difference between the material components. The greater the difference in components, the greater the lattice mismatch. The lattice constants of AlN are a=0.3112nm, c=0.4982nm, and the lattice constants of GaN are a=0.31896nm, c=0.51855nm. The lattice mismatch between AlN and GaN is 2.5%. According to Vegard's law, Al with Al component x (0≤x≤1) x Ga 1-x N ternary compound, in the fully relaxed state, has a lattice constant of AlxGa1-xN =x*a AlN +(1-x)* GaN Therefore, for a certain composition of Al x Ga 1-x N (x<1), its lattice constant is greater than AlN, and the lattice mismatch between the two depends on the component x. The larger the x, the greater the lattice mismatch of AlN. x Ga 1-x The greater the lattice mismatch between N and AlN, the greater the Al growth on the AlN template surface. x Ga 1-x The morphology and crystal quality of N are also worse.

[0004] In the UVB structure with a light emission wavelength of 294nm~300nm, the quantum well composition is 30%~39%. In order to reduce the quantum well layer and nAl x Ga 1-x Lattice mismatch of N template requires the growth of lower composition nAl x Ga 1-x N layer, but lower composition nAl x Ga 1-xThe N layer will have a larger lattice mismatch with the AlN template. Therefore, in the preparation process of UVB epitaxial structure, nAl x Ga 1-x The preparation of N template is more difficult. x Ga 1-x The large lattice mismatch between the N layer and the AlN template layer will cause a large number of hexagonal protrusions with a height of 100nm~180nm on the surface of the epitaxial layer, thereby affecting the surface roughness, and then affecting the flatness of the interface between the quantum well layer and the barrier layer, widening the half-wave width of the quantum well emission spectrum. At the same time, the large lattice mismatch will lead to the increase of dislocations, increase the dislocation density of the nAlGaN layer, and then extend the dislocation density to the quantum well layer, thereby reducing the internal quantum efficiency.

[0005] Traditional UVB epitaxial structures generally use 3 to 10 pairs of quantum barrier / quantum well structures, all of which are periodic and repetitive structures, and the growth process settings also use periodic and repetitive growth conditions.

[0006] During the epitaxial growth process, the migration rate of Al atoms is low. In order to increase the migration rate, a higher growth temperature is required. The growth temperature of the AlN template is between 1130 and 1250°C, which places high demands on the high-temperature performance of the MOCVD equipment. At the same time, during the growth process of AlN, the AlN thin film layer grown inside the chamber, on the upper cover, and on the surface of the graphite disk will affect the growth temperature of the subsequent epitaxial layer, resulting in instability in the epitaxial process growth, affecting the crystallization quality and morphology stability of the AlN template. Therefore, the output yield of growing AlN templates using high-temperature MOCVD equipment is relatively low, and in order to improve the yield, it is necessary to clean the upper cover every furnace to reduce the impact of the upper cover AlN thin film layer on temperature control. Therefore, the traditional process uses AlN templates as substrate materials, which has the disadvantages of high threshold, low yield and high cost.

[0007] Using AlN template as substrate material to grow 50%~60% nAlGaN will result in a rough nAlGaN morphology and high dislocation density due to lattice mismatch. In order to improve the morphology of nAlGaN and reduce the dislocation density of nAlGaN, a single component Al is generally used. x Ga 1-x N layer for transition or superlattice insertion layer to control strain and block dislocation expansion, but both methods have high requirements for process control. For example, the use of AlN / AlGaN superlattice layer requires increasing the composition difference between AlN and AlGaN layers, which is more demanding on growth conditions and reduces the repeatability of the process. Although there are obvious effects, they only reduce the relaxation caused by lattice mismatch and the proliferation of dislocations during relaxation by means of transition and stress control, and cannot fundamentally eliminate lattice mismatch.

[0008] In the traditional UVB epitaxial structure, the growth parameters of multiple pairs of quantum barriers / quantum wells in the active region are designed to be periodically repetitive and the growth conditions are also periodically repetitive. However, the inventors found in experiments that the thickness of the quantum wells tested by TEM after actual growth of the multiple quantum wells designed according to repetitive conditions is not the same, and the components of the quantum wells tested by SIMS are not fixed, which will cause the actual luminescence spectrum half-peak width to be wide and the ratio of the integral intensity of the effective spectrum to the integral intensity of all spectra to be low.

[0009] The invention patent with publication number CN103165777B provides an LED epitaxial wafer with an N-type insertion layer having a trapezoidal structure and a growth method thereof. Although the scheme mentions that the N-type AlGaN insertion layer has a trapezoidal structure, the trapezoidal structure may cause uneven stress during the growth process, thereby affecting the crystallization quality of the material and the reliability of the device.

[0010] The invention patent application with publication number CN106920866A provides an epitaxial method for regulating the wavelength of ultraviolet light-emitting diode epitaxial wafers. The carrier concentration in the non-doped layer is difficult to accurately control, and uneven carrier distribution is prone to occur, which will lead to uneven electric field and current distribution in the active area, making the device's luminous efficiency inconsistent, affecting the uniformity and stability of luminescence, and causing problems such as uneven display brightness in display applications. Summary of the invention

[0011] In view of the disadvantages of high threshold, low yield and high cost in the above-mentioned traditional process using AlN template as substrate material, and the technical problem that the components of SIMS test quantum wells in the traditional UVB epitaxial structure are not fixed components, the present invention provides an AlGaN-based UVB epitaxial wafer structure and a preparation method thereof.

[0012] In order to solve the above technical problems, the technical solution adopted by the present invention is: A method for preparing an AlGaN-based UVB epitaxial wafer structure comprises the following steps: S1. Prepare a 5nm~30nm AlN buffer layer on the surface of the sapphire substrate; S2. Place the sapphire substrate prepared with AlN buffer layer in MOCVD to grow structural layers; S2.1. Grow a 3D AlGaN layer of 300nm~400nm on the AlN buffer layer; S2.2. Grow a 2D AlGaN layer on the 3D AlGaN layer; S2.3. Grow an AlGaN layer with an Al component of 50%~60% on the 2D AlGaN layer; S2.4. Grow a Si-doped nAlGaN layer on the AlGaN layer; S2.5. Grow a multi-quantum well active layer on the Si-doped nAlGaN layer; S2.6. Grow an EBL layer on the multi-quantum well active layer; S2.7. Grow a hole injection layer on the EBL layer; S2.8. Grow a hole supply layer on the hole injection layer.

[0013] The growth process of preparing a 5nm~30nm AlN buffer layer on the surface of the sapphire substrate in S1 is: temperature of 550℃~700℃, sputtering power of 1000W~4000W, nitrogen flow rate of 80sccm~200sccm, oxygen flow rate of 0.5sccm~5sccm, argon flow rate of 0.1sccm~40sccm, and deposition time of 16s~100s.

[0014] The growth process of growing a 3D AlGaN layer of 300nm~400nm in S2.1 is: the temperature gradually changes from 950℃ to 1000℃, the pressure is 20torr~35torr, the TMAl flow rate is 120umol / min~150umol / min, the TMGa flow rate gradually changes from 480umol / min~600umol / min to 610umol / min~720umol / min, the NH3 flow rate is 2000sccm~6000sccm, the carrier gas is a mixed gas of H2 and N2, the H2 carrier gas flow rate is 15L / min~30L / min, the N2 carrier gas flow rate is 15L / min~30L / min, and the growth thickness is 300nm~400nm.

[0015] The growth process of growing the 2D AlGaN layer in S2.2 is as follows: the temperature gradually changes from 1150°C to 1200°C, the pressure is 20torr~35torr, the TMAl flow rate is 120umol / min~150umol / min, the TMGa flow rate gradually changes from 600umol / min~750umol / min to 760umol / min~900umol / min, the NH3 flow rate is 200sccm~600sccm, pure N2 carrier gas is introduced, the carrier gas flow rate is 30L / min~60L / min, and the growth thickness is 200nm~300nm; The growth process of the AlGaN layer with an Al component of 50% to 60% in S2.3 is as follows: the temperature gradually changes from 1200°C to 1100°C, the pressure is 20torr to 35torr, the TMAl flow rate is 120umol / min to 150umol / min, the TMGa flow rate gradually changes from 720umol / min to 900umol / min to 540umol / min to 675umol / min, the NH3 flow rate is 200sccm to 600sccm, pure N2 carrier gas is introduced, the carrier gas flow rate is 30L / min to 60L / min, and the growth thickness is 450nm to 550nm.

[0016] The growth process of the Si-doped nAlGaN layer in S2.4 is as follows: temperature 1100°C, pressure 20 torr-35 torr, TMAl flow rate 120 umol / min-150 umol / min, TMGa flow rate 540-675 umol / min, NH3 flow rate 200 sccm-600 sccm, pure N2 carrier gas, carrier gas flow rate 30 L / min-60 L / min, growth thickness 3500 nm-4500 nm, SiH4 doping concentration 3E17 cm -3 ~5E18cm -3 .

[0017] The growth process of the multi-quantum well active layer in S2.5 is as follows: the number of cycles is 3 to 5 pairs, the temperature is 1000°C to 1050°C, the pressure is 35 torr to 100 torr, the TMAl flow rate is 80 umol / min to 100 umol / min, and the TMGa flow rate is 53 umol / min to 66 umol / min; the Al component of the barrier layer is 60% to 65%, the thickness is 10 nm to 20 nm, the third to the first quantum wells from the last are prepared as fixed-component quantum wells, the quantum wells are in the forward direction perpendicular to the epitaxial growth direction, the temperature is 1100°C, the pressure is 35 torr to 100 torr, the TMAl flow rate is 40 umol / min to 50 umol / min, and the TMGa flow rate is 160 umol / min ~200umol / min, the Al composition of the well layer was set to 20%~25%, the actual composition was 40%~45%, and the thickness was 1.1nm~2nm; two quantum well layers close to the p-side were prepared at a temperature of 1100℃, a pressure of 35torr~100torr, a TMGa flow rate of 160 umol / min~200umol / min, and a TMAl flow rate gradually changed from 17.8umol / min~22.3umol / min to 8.45umol / min~10.5umol / min. The Al composition of the well layer was set to gradually change from 10% to 5%, the actual composition was 30%~39%, and the thickness was 1.1nm~2nm.

[0018] The growth process of the EBL layer grown in S2.6 is as follows: the EBL layer adopts a multi-quantum well structure or a single-layer EBL, the period number of the multi-quantum well structure is 1 pair to 5 pairs, the Al composition of the barrier layer is 60% to 80%, the thickness is 6nm to 20nm, the Al composition of the well layer is 40% to 50%, and the thickness is 1.5nm to 3.5nm; the composition of the single-layer EBL is 60% to 80%, and the thickness is 30nm to 70nm.

[0019] The growth process of the hole injection layer in S2.7 is as follows: the hole injection layer is pAlGaN with a gradient composition, the Al composition gradient changes from 0.7 to 0.35, the thickness is 15nm~40nm, and the Mg doping concentration is 1E19cm -3 ~2E20cm -3 .

[0020] The growth process of growing the hole supply layer in S2.8 is as follows: the hole supply layer is pGaN with a thickness of 1nm~10nm and a Mg doping concentration of 1E20cm -3 ~2E21cm -3 .

[0021] An AlGaN-based UVB epitaxial wafer structure comprises a sapphire substrate, an AlN buffer layer, a 3D AlGaN layer, a 2D AlGaN layer, an AlGaN layer, a nAlGaN layer, a multi-quantum well active layer, an EBL layer, a hole injection layer and a hole supply layer, wherein the AlN buffer layer is grown on the sapphire substrate, the 3D AlGaN layer is grown on the AlN buffer layer, the 2D AlGaN layer is grown on the 3D AlGaN layer, the AlGaN layer is grown on the 2D AlGaN layer, the nAlGaN layer is grown on the AlGaN layer, the multi-quantum well active layer is grown on the nAlGaN layer, the EBL layer is grown on the multi-quantum well active layer, the hole injection layer is grown on the EBL layer, and the hole supply layer is grown on the hole injection layer.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention uses temperature gradient and the ratio change of TMAl and TMGa flow rates to achieve two-step growth of AlGaN with a certain component as a single alloy material with a fixed component, thereby eliminating the growth of the AlN template, reducing the requirements for the high temperature resistance of the equipment, and avoiding the shortcomings of poor repeatability of the AlN template growth. At the same time, it also avoids the dislocation proliferation caused by the lattice mismatch between the AlN template and the subsequent AlGaN material, and achieves high-quality growth of low-resistance AlGaN.

[0023] 2. The present invention realizes the growth of fixed single-component quantum wells by reasonably setting the component gradient of the last two pairs of quantum wells, thereby reducing the spatial separation of electron and hole wave functions, improving the efficiency of carrier radiation, and increasing the proportion of the effective band integral area and the total spectrum integral area.

[0024] 3. The present invention uses an nAlGaN template process for growth without an AlN template structure and a component-gradient quantum well growth process to prepare a UVB epitaxial structure with a smooth interface, low dislocation density and low QCSE effect, thereby increasing the proportion of the effective spectrum used to supplement the VD3 light source, avoiding the use of filters, and improving the light efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0026] The structures, proportions, sizes, etc. illustrated in this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with the technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantial technical significance. Any structural modification, change in proportion or adjustment of size shall still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0027] Figure 1 It is a structural schematic diagram of the present invention; Figure 2 is a growth process curve diagram of the present invention; Figure 3 This is a schematic diagram of the designed Al component of the present invention; Figure 4 It is a schematic diagram of the actual Al component of the present invention; Figure 5 It is the original process spectrum; Figure 6 It is the process spectrum diagram of the present invention; Figure 7 This is the 168h light maintenance rate diagram of the original process UVB epitaxial wafer; Figure 8 This is a graph showing the 168h light maintenance rate of the UVB epitaxial wafer produced using the process of the present invention.

[0028] Among them: 1 is a sapphire substrate, 2 is an AlN buffer layer, 3 is a 3D AlGaN layer, 4 is a 2D AlGaN layer, 5 is an AlGaN layer, 6 is an nAlGaN layer, 7 is a multi-quantum well active layer, 8 is an EBL layer, 9 is a hole injection layer, and 10 is a hole supply layer. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. These descriptions are only to further illustrate the features and advantages of the present invention, rather than to limit the claims of the present invention. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0030] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0031] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances. Example

[0032] A method for preparing an AlGaN-based UVB epitaxial wafer structure, such as Figure 1-4 As shown, the following steps are included: Step 1. Prepare a 5nm~30nm AlN buffer layer 2 on the surface of a 2-inch sapphire substrate 1. The magnetron sputtering growth process is: temperature is 550℃~700℃, sputtering power is 1000 W~4000W, nitrogen flow rate is 80 sccm~200sccm, oxygen flow rate is 0.5sccm~5sccm, argon flow rate is 0.1sccm~40sccm, and deposition time is 16s~100s.

[0033] Step 2: Place the sapphire substrate 1 prepared with the AlN buffer layer 2 in MOCVD to grow the structural layer: Step 2.1, grow a 300~400nm 3D AlGaN layer 3. The specific growth process at this stage is: the temperature gradually changes from 950℃ to 1000℃, the pressure is 20torr~35torr, the TMAl flow rate is 120umol / min~150umol / min, the TMGa flow rate gradually changes from 480umol / min~600umol / min to 610umol / min~720umol / min, the NH3 flow rate is 2000sccm~6000sccm, H2 and N2 mixed gas carrier gas, the H2 carrier gas flow rate is 15L / min~30L / min, the N2 carrier gas flow rate is 15L / min~30L / min, and the growth thickness is 300nm~400nm.

[0034] Step 2.2, grow a 2D AlGaN layer 4, the temperature gradually changes from 1150℃ to 1200℃, the pressure is 20torr~35torr, the TMAl flow rate is 120umol / min~150umol / min, the TMGa flow rate gradually changes from 600umol / min~750umol / min to 760umol / min~900umol / min, the NH3 flow rate is 200sccm~600sccm, pure N2 carrier gas, the carrier gas flow rate is 30L / min~60L / min, and the growth thickness is 200nm~300nm. This process ensures that the actual composition of the grown AlGaN layer 5 is a constant 50%~60% by combining the use of gradual temperature increase and gradually increasing TMGa molar composition ratio at a higher temperature. After the temperature is increased, the mobility of Al and Ga will increase to achieve a two-dimensional planar growth mode, but the incorporation efficiency of Ga will decrease due to the increase in temperature. By increasing the molar composition ratio of TMGa, the actual Al composition is ensured to be consistent with the 3D AlGaN layer 3.

[0035] Step 2.3, grow AlGaN layer 5 on the 2D AlGaN layer 4 that has completed island merging, the temperature gradually changes from 1200℃ to 1100℃, the pressure is 20torr~35torr, the TMAl flow rate is 120umol / min~150umol / min, the TMGa flow rate gradually changes from 720umol / min~900umol / min to 540umol / min~675umol / min, the NH3 flow rate is 200sccm~600sccm, pure N2 carrier gas, the carrier gas flow rate is 30L / min~60L / min, and the growth thickness is 450nm~550nm. This process ensures that the actual Al component of the grown AlGaN layer 5 is a constant 50%~60% by combining the gradual cooling and the process components with a gradually decreasing TMGa molar component ratio at a higher temperature.

[0036] Step 2.4, on the AlGaN layer 5 with an Al content of 50% to 60% and a flat surface, a Si-doped nAlGaN layer 6 is homogeneously grown using fixed growth conditions: temperature of 1100°C, pressure of 20 torr to 35 torr, TMAl flow rate of 120 umol / min to 150 umol / min, TMGa flow rate of 540 umol / min to 675 umol / min, NH3 flow rate of 200 sccm to 600 sccm, pure N2 carrier gas, carrier gas flow rate of 30 L / min to 60 L / min, growth thickness of 3500 nm to 4500 nm, SiH4 doping concentration of 3E17 cm -3 ~5E18cm -3 .

[0037] Step 2.5, grow a multi-quantum well active layer 7, with 3 to 5 pairs of periods, a temperature of 1100°C, a pressure of 35 torr to 100 torr, a TMAl flow rate of 80 umol / min to 100 umol / min, a TMGa flow rate of 53 umol / min to 66 umol / min, an Al component of the barrier layer of 60% to 65%, a thickness of 10 nm to 20 nm, the third to the first quantum well from the last is a fixed-composition quantum well, a temperature of 1100°C, a pressure of 35 torr to 100 torr, a TMAl flow rate of 40 umol / min to 50 umol / min, and a TMGa flow rate of 160 umol / min n~200umol / min, the Al composition of the well layer is set to 20%~25%, the actual composition is 40%~45%, and the thickness is 1.1nm~2nm; the two quantum well layers close to the p-side have a temperature of 1100℃, a pressure of 35torr~100torr, a TMGa flow rate of 160umol / min~200umol / min, and a TMAl flow rate gradually changing from 17.8umol / min~22.3umol / min to 8.45umol / min~10.5umol / min. The Al composition of the well layer is set to gradually change from 10% to 5%, the actual composition is 30%~39%, and the thickness is 1.1nm~2nm.

[0038] Step 2.6, growing an EBL layer 8. The EBL layer 8 can be a multi-quantum well structure with a period number of 1 to 5 pairs, a barrier layer Al composition of 60% to 80%, a thickness of 6nm to 20nm, a well layer Al composition of 40% to 50%, and a thickness of 1.5nm to 3.5nm; it can also be a single-layer EBL with a composition of 60% to 80% and a thickness of 30nm to 70nm.

[0039] Step 2.7, growing a hole injection layer 9, the hole injection layer 9 is a pAlGaN with a gradient composition, the Al composition of the hole injection layer 9 gradually changes from 0.7 to 0.35, the thickness of the hole injection layer 9 is 15nm~40nm, and the Mg doping concentration is 1E19cm -3 ~2E20cm -3 .

[0040] Step 2.8: grow a hole supply layer 10, the hole supply layer 10 is pGaN, the thickness is 1nm~10nm, and the Mg doping concentration is 1E20cm -3 ~2E21cm -3 . Example

[0041] An AlGaN-based UVB epitaxial wafer structure, such as Figure 1As shown, it includes a sapphire substrate 1, an AlN buffer layer 2, a 3D AlGaN layer 3, a 2D AlGaN layer 4, an AlGaN layer 5, a nAlGaN layer 6, a multi-quantum well active layer 7, an EBL layer 8, a hole injection layer 9 and a hole supply layer 10, the AlN buffer layer 2 is grown on the sapphire substrate 1, the 3D AlGaN layer 3 is grown on the AlN buffer layer 2, the 2D AlGaN layer 4 is grown on the 3D AlGaN layer 3, the AlGaN layer 5 is grown on the 2D AlGaN layer 4, the nAlGaN layer 6 is grown on the AlGaN layer 5, the multi-quantum well active layer 7 is grown on the nAlGaN layer 6, the EBL layer 8 is grown on the multi-quantum well active layer 7, the hole injection layer 9 is grown on the EBL layer 8, and the hole supply layer 10 is grown on the hole injection layer 9.

[0042] The UVBLED prepared by the above process has a peak wavelength of 295nm~299nm. The original process UVB epitaxial wafer is a UVB epitaxial wafer that uses AlN as a template material to grow a component of 55% nAlGaN, and the quantum well setting condition is to repeat 5 pairs of quantum wells. The UVB epitaxial wafer of the process of the present invention is a UVB epitaxial wafer prepared by Example 1 of the present invention with a component of 55% nAlGaN, and the last two quantum wells in the quantum well are quantum wells with gradually decreasing components, and the other structures are consistent with the original process UVB epitaxial wafer. The epitaxial wafers grown by the two processes were respectively made into 20mil×20mil chips, and the spectrum and light maintenance rate of the two chips were tested under 10mA conditions. The results are as follows: 1) Comparison of the integrated area ratio of 281nm-306nm: Figure 5 and Figure 6 It can be seen that after using the process of the present invention, the half-peak width is reduced from 14nm to 11.8nm, and the ratio of the integrated area of ​​the 281nm-306nm band to the total spectrum integrated area is increased from 85.2% to 90.6%.

[0043] 2) Comparison of light maintenance rate: Figure 7 and Figure 8 It can be seen that after using the process of the present invention, the 168h light maintenance rate is increased from 91%~93% of the original process to more than 100%.

[0044] Only the preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention, and various changes should be included in the protection scope of the present invention.

Claims

1. A method for preparing an AlGaN-based UVB epitaxial wafer structure, characterized in that: The following steps are involved: S1. Preparing a 5 nm to 30 nm AlN buffer layer (2) on the surface of a sapphire substrate (1); S2. Placing a sapphire substrate (1) prepared with an AlN buffer layer (2) in an MOCVD process to grow a structural layer; S2.

1. Growing a 3D AlGaN layer (3) of 300 nm to 400 nm on the AlN buffer layer (2); S2.

2. Growing a 2D AlGaN layer (4) on the 3D AlGaN layer (3); S2.

3. Growing an AlGaN layer (5) with an Al component of 50% to 60% on the 2D AlGaN layer (4); S2.

4. Growing a Si-doped nAlGaN layer (6) on the AlGaN layer (5); S2.

5. Growing a multi-quantum well active layer (7) on the Si-doped nAlGaN layer (6); S2.

6. Growing an EBL layer (8) on the multi-quantum well active layer (7); S2.

7. Growing a hole injection layer (9) on the EBL layer (8); S2.

8. Growing a hole supply layer (10) on the hole injection layer (9).

2. The method for preparing an AlGaN-based UVB epitaxial wafer structure according to claim 1, characterized in that: The growth process of preparing a 5nm-30nm AlN buffer layer (2) on the surface of a sapphire substrate (1) in S1 is as follows: temperature of 550°C-700°C, sputtering power of 1000W-4000W, nitrogen flow rate of 80sccm-200sccm, oxygen flow rate of 0.5sccm-5sccm, argon flow rate of 0.1sccm-40sccm, and deposition time of 16s-100s.

3. The method for preparing an AlGaN-based UVB epitaxial wafer structure according to claim 1, characterized in that: The growth process of growing a 300nm-400nm 3D AlGaN layer (3) in S2.1 is as follows: the temperature gradually changes from 950°C to 1000°C, the pressure is 20torr-35torr, the TMAl flow rate is 120umol / min-150umol / min, the TMGa flow rate gradually changes from 480umol / min-600umol / min to 610umol / min-720umol / min, the NH3 flow rate is 2000sccm-6000sccm, the carrier gas is a mixed gas of H2 and N2, the H2 carrier gas flow rate is 15L / min-30L / min, the N2 carrier gas flow rate is 15L / min-30L / min, and the growth thickness is 300nm-400nm.

4. The method for preparing an AlGaN-based UVB epitaxial wafer structure according to claim 1, characterized in that: The growth process of growing the 2D AlGaN layer (4) in S2.2 is as follows: the temperature gradually changes from 1150° C. to 1200° C., the pressure is 20 torr to 35 torr, the TMAl flow rate is 120 umol / min to 150 umol / min, the TMGa flow rate gradually changes from 600 umol / min to 750 umol / min to 760 umol / min to 900 umol / min, the NH3 flow rate is 200 sccm to 600 sccm, pure N2 carrier gas is introduced, the carrier gas flow rate is 30 L / min to 60 L / min, and the growth thickness is 200 nm to 300 nm; The growth process of the AlGaN layer (5) with an Al component of 50% to 60% in S2.3 is as follows: the temperature gradually changes from 1200° C. to 1100° C., the pressure is 20 torr to 35 torr, the TMAl flow rate is 120 umol / min to 150 umol / min, the TMGa flow rate gradually changes from 720 umol / min to 900 umol / min to 540 umol / min to 675 umol / min, the NH3 flow rate is 200 sccm to 600 sccm, pure N2 carrier gas is introduced, the carrier gas flow rate is 30 L / min to 60 L / min, and the growth thickness is 450 nm to 550 nm.

5. The method for preparing an AlGaN-based UVB epitaxial wafer structure according to claim 1, characterized in that: The growth process of the Si-doped nAlGaN layer (6) in S2.4 is as follows: temperature of 1100°C, pressure of 20 torr to 35 torr, TMAl flow rate of 120 umol / min to 150 umol / min, TMGa flow rate of 540 to 675 umol / min, NH3 flow rate of 200 sccm to 600 sccm, pure N2 carrier gas, carrier gas flow rate of 30 L / min to 60 L / min, growth thickness of 3500 nm to 4500 nm, SiH4 doping concentration of 3E17 cm -3 ~5E18cm -3 .

6. The method for preparing an AlGaN-based UVB epitaxial wafer structure according to claim 1, characterized in that: The growth process of growing the multi-quantum well active layer (7) in S2.5 is as follows: the number of cycles is 3 to 5 pairs, the temperature is 1000° C. to 1050° C., the pressure is 35 torr to 100 torr, the TMAl flow rate is 80 umol / min to 100 umol / min, and the TMGa flow rate is 53 umol / min to 66 umol / min; the barrier layer Al component is 60% to 65%, the thickness is 10 nm to 20 nm, the third to the first quantum wells from the last are prepared as fixed-component quantum wells, the quantum wells are in the forward direction perpendicular to the epitaxial growth direction, the temperature is 1100° C., the pressure is 35 torr to 100 torr, the TMAl flow rate is 40 umol / min to 50 umol / min, and the TMGa flow rate is 160 umol / min ~200umol / min, the Al composition of the well layer was set to 20%~25%, the actual composition was 40%~45%, and the thickness was 1.1nm~2nm; two quantum well layers close to the p-side were prepared at a temperature of 1100℃, a pressure of 35torr~100torr, a TMGa flow rate of 160 umol / min~200umol / min, and a TMAl flow rate gradually changed from 17.8umol / min~22.3umol / min to 8.45umol / min~10.5umol / min. The Al composition of the well layer was set to gradually change from 10% to 5%, the actual composition was 30%~39%, and the thickness was 1.1nm~2nm.

7. The method for preparing an AlGaN-based UVB epitaxial wafer structure according to claim 1, characterized in that: The growth process of growing the EBL layer (8) in S2.6 is as follows: the EBL layer (8) adopts a multi-quantum well structure or a single-layer EBL, the period number of the multi-quantum well structure is 1 pair to 5 pairs, the barrier layer Al composition is 60% to 80%, the thickness is 6nm to 20nm, the well layer Al composition is 40% to 50%, and the thickness is 1.5nm to 3.5nm; the single-layer EBL composition is 60% to 80%, and the thickness is 30nm to 70nm.

8. The method for preparing an AlGaN-based UVB epitaxial wafer structure according to claim 1, characterized in that: The growth process of growing the hole injection layer (9) in S2.7 is as follows: the hole injection layer (9) is a pAlGaN with a gradient composition, the Al composition gradient changes from 0.7 to 0.35, the thickness is 15nm~40nm, and the Mg doping concentration is 1E19cm -3 ~2E20cm -3 .

9. The method for preparing an AlGaN-based UVB epitaxial wafer structure according to claim 1, characterized in that: The growth process of growing the hole supply layer (10) in S2.8 is as follows: the hole supply layer (10) is pGaN, has a thickness of 1 nm to 10 nm, and a Mg doping concentration of 1E20 cm -3 ~2E21cm -3 .

10. An AlGaN-based UVB epitaxial wafer structure, characterized in that: The invention comprises a sapphire substrate (1), an AlN buffer layer (2), a 3D AlGaN layer (3), a 2D AlGaN layer (4), an AlGaN layer (5), an nAlGaN layer (6), a multi-quantum well active layer (7), an EBL layer (8), a hole injection layer (9) and a hole supply layer (10), wherein the AlN buffer layer (2) is grown on the sapphire substrate (1), the 3D AlGaN layer (3) is grown on the AlN buffer layer (2), the 2D AlGaN layer (4) is grown on the 3D AlGaN layer (3), and the AlGaN layer (5) is grown on the 2D The invention relates to a nanostructured carbon nanotube layer (10) comprising a nanostructured carbon nanotube layer (20) and a nanostructured carbon nanotube layer (30). The nanostructured carbon nanotube layer (20) is grown on the nanostructured carbon nanotube layer (30), the nanostructured carbon nanotube layer (30) is grown on the nanostructured carbon nanotube layer (30), the nanostructured carbon nanotube layer (30) is grown on the nanostructured carbon nanotube layer (30), the nanostructured carbon nanotube layer (30) is grown on the nanostructured carbon nanotube layer (30), the nanostructured carbon nanotube layer (30) is grown on the nanostructured carbon nanotube layer (30),

Images