CN112635628B - Deep ultraviolet semiconductor light emitting diode epitaxial structure - Google Patents

Deep ultraviolet semiconductor light emitting diode epitaxial structure Download PDF

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CN112635628B
CN112635628B CN202011517916.6A CN202011517916A CN112635628B CN 112635628 B CN112635628 B CN 112635628B CN 202011517916 A CN202011517916 A CN 202011517916A CN 112635628 B CN112635628 B CN 112635628B
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CN112635628A (en
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张勇辉
张沐垚
张紫辉
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Hebei University of Technology
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    • H01L33/20—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a particular shape, e.g. curved or truncated substrate
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    • H01L33/0066—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound
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    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
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    • H01L33/04—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction
    • H01L33/06—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction within the light emitting region, e.g. quantum confinement structure or tunnel barrier
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    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/14—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure
    • H01L33/145—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure with a current-blocking structure
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    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/20—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a particular shape, e.g. curved or truncated substrate
    • H01L33/24—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a particular shape, e.g. curved or truncated substrate of the light emitting region, e.g. non-planar junction
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    • H01L33/26—Materials of the light emitting region
    • H01L33/30—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table
    • H01L33/32—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen

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Abstract

The invention relates to a deep ultraviolet semiconductor light emitting diode epitaxial structure. The epitaxial structure sequentially comprises a patterned substrate, a semiconductor buffer layer, an n-type semiconductor material layer, a multi-quantum well layer, a p-type electronic barrier layer and a p-type semiconductor material transmission layer along an epitaxial direction; the pattern substrate is etched with grooves, each groove is vertically upwards provided with a cavity structure, the cavity structure penetrates through the semiconductor buffer layer, the n-type semiconductor material layer and the multi-quantum well layer, and the top positions of the cavity structures are as follows: the first type is polymerized on a p-type electron blocking layer, the polymerization depth of a cavity in the p-type electron blocking layer is 10-100 nm, or the second type is polymerized on a p-type semiconductor material transmission layer by continuously penetrating through the p-type electron blocking layer, the polymerization depth of the cavity in the p-type semiconductor material transmission layer is 10-500 nm, or the third type is polymerized on the p-type electron blocking layer and the p-type semiconductor material transmission layer by continuously penetrating through the cavity, and the cavity is not polymerized and appears as a round hole on the surface of the p-type semiconductor material transmission layer. The invention can improve the internal quantum efficiency of the deep ultraviolet LED; and the quantum well is incorporated into the cavity structure, so that the scattering property of light can be effectively improved, and the light extraction efficiency of the deep ultraviolet light-emitting diode is improved.

Description

Deep ultraviolet semiconductor light emitting diode epitaxial structure
Technical Field
The technical scheme of the invention relates to a semiconductor device, in particular to a deep ultraviolet semiconductor light emitting diode and a preparation method thereof.
Background
Deep ultraviolet light refers to ultraviolet light having a wavelength of less than 300 nm. Due to the short wavelength, the method has great development potential in the fields of sensing, medicine, disinfection, light curing, water purification and the like. A deep ultraviolet light emitting diode (DUV LED) is a light emitting diode capable of emitting deep ultraviolet light, and has a series of advantages of long service life, low operating voltage, smart design, no toxicity, and environmental protection, compared with a conventional mercury lamp, and thus has received wide attention from various fields. AlGaN-based DUV LEDs are DUV LEDs with AlGaN as a p-n junction and are the most popular DUV LEDs at present.
Conventional AlGaN-based DUV LEDs are grown on sapphire substrates due to the high optical transparency of sapphire and the well-established LED technology. However, the growth of n-type AlGaN having a high Al composition on a sapphire substrate causes a severe lattice mismatch and thermal expansion coefficient mismatch, and the surface mobility of Al atoms in sapphire is also low. These drawbacks severely limit the crystalline quality of high aluminum AlGaN on planar sapphire substrates (FSS). The nanopattern substrate is capable of relieving stress in the epitaxial layer and reducing dislocation density of the epitaxial layer by dislocation bending during lateral epitaxial growth.
Therefore, the current patterned sapphire patterned substrate (PSS) has been applied to the growth of the deep ultraviolet AlGaN deep ultraviolet LED. Current epitaxial techniques on PSS are growing naclgan, Multiple Quantum Well (MQWs) and pAlGaN structures on fully merged AlN epitaxial layers. In the AlN epitaxial process, AlN preferentially grows a single crystal epitaxial layer at a position without a pattern on a nano-pattern substrate, then the epitaxial layer which grows in the epitaxial process slowly grows transversely and is finally combined above the pattern on the pattern substrate, the pattern of the substrate has the function and the purpose of effectively releasing the stress of a buffer layer growing on the substrate through the pattern, and dislocation is bent towards the boundary of a cavity through the cavity which is naturally formed because the pattern cannot be directly combined in the early stage, so that the extension of the dislocation can be effectively reduced, and the quality of the epitaxial layer is improved. When the air cones are combined, a large number of dislocations are generated due to different crystal orientations, and the dislocations directly extend into the quantum well, so that the Internal Quantum Efficiency (IQE) of the deep ultraviolet LED is reduced. In addition, in general, AlGaN-based deep ultraviolet LEDs employ pGaN as a hole transport layer and an ohmic contact layer, which have a large amount of absorption for light, and although PSS introduces scattering centers, most of light emitted from the scattering centers is firstly scattered toward pGaN, and most of the light is absorbed by pGaN, which cannot effectively improve the light extraction efficiency of deep ultraviolet LEDs.
Disclosure of Invention
The invention aims to provide a deep ultraviolet semiconductor light emitting diode epitaxial structure and a preparation method thereof, aiming at the defects of the prior art. The structure extends the cavity structure to the p-type electron barrier layer and even the p-type semiconductor material transmission layer, and the quantum well structure is grown before the cavity structure is completely combined, so that the dislocation density in the quantum well is reduced, and the internal quantum efficiency of the deep ultraviolet LED can be improved; and the quantum well is incorporated into the cavity structure, so that the scattering property of light can be effectively improved, and the light extraction efficiency of the deep ultraviolet light-emitting diode is improved.
The technical scheme adopted by the invention for solving the technical problem is as follows:
a deep ultraviolet semiconductor light emitting diode epitaxial structure comprises a pattern substrate, a semiconductor buffer layer, an n-type semiconductor material layer, a multi-quantum well layer, a p-type electronic barrier layer and a p-type semiconductor material transmission layer in sequence along an epitaxial direction;
a groove is etched on the pattern substrate, and the groove is a pit or a strip and has the size of 500 nm-20 um; the distance between every two adjacent grooves is 5-30 mu m;
the grooves are regularly arranged, and a rectangular array or annular radial arrangement pattern is formed on the substrate.
Wherein, on every recess of figure substrate surface, all upwards vertical growth has a cavity structure, and the cavity structure passes semiconductor buffer layer, n type semiconductor material layer, multiple quantum well layer, and the top position is following three kinds:
the first is polymerized in a p-type electron blocking layer, and the polymerization depth of a cavity in the p-type electron blocking layer is 10-100 nm;
or, secondly, the second type semiconductor material is polymerized in the p-type semiconductor material transmission layer after continuously penetrating through the p-type electron blocking layer, and the polymerization depth of the cavity in the p-type semiconductor material transmission layer is 10-500 nm;
or thirdly, the cavity is not polymerized and appears as a round hole on the surface of the p-type semiconductor material transmission layer after continuously passing through the p-type electron blocking layer and the p-type semiconductor material transmission layer.
The cavity structure is a conical knot or a cylinder, and when the cavity structure is conical, the conical degree is 0.75-0.85.
The projection shape of the groove is circular or rectangular, and the depth is 200 nm-20 mu m.
The pattern substrate material is sapphire, SiC, Si, AlN, GaN or quartz glass, and can be divided into a polar plane [0001] substrate, a semipolar plane [11-22] substrate or a nonpolar plane [1-100] substrate along the difference of the epitaxial growth direction.
The semiconductor buffer layer is AlN, the thickness is 0.1-10 mu m, and the semiconductor buffer layer has a cavity structure.
The n-type semiconductor material layer is made of silicon-doped n-type Alx1Ga1-x1N, ensuring that the coefficient of each component is more than or equal to 0 and less than or equal to x1 and less than or equal to 1, more than or equal to 1-x1-y1 and more than or equal to 0, the thickness is 0.1-10 mu m, and the composite material has a cavity structure.
The material of the multi-quantum well layer is Alx2Ga1-x2N/Alx3Ga1-x3N, wherein the component coefficients are more than or equal to 0 and less than or equal to x2 and less than or equal to 1, more than or equal to 1 and more than or equal to 1-x2 and more than or equal to 0, more than or equal to 0 and less than or equal to x3 and less than or equal to 1, more than or equal to 1-x3 and more than or equal to 0, the forbidden bandwidth of the quantum barrier is higher than that of the quantum well, the number of the quantum wells is more than or equal to 1, and the quantum well Al is doped with Alx2Ga1-x2N is 1-20 nm thick, and quantum barrier Alx3Ga1-x3The N is 3-50 nm thick and has a cavity structure.
The p-type electron blocking layer is made of magnesium-doped p-type Alx4Ga1-x4N, ensuring that the coefficient of each component is not less than 0 and not more than x4 and not more than 1,1 is not less than 1-x4 and not less than 0, and the thickness is 10-100 nm.
The p-type semiconductor material transmission layer is p-type Alx5Ga1-x5N, ensuring that the coefficient of each component is more than or equal to 0 and less than or equal to x5 and less than or equal to 1, more than or equal to 1 and more than or equal to 1-x5 and more than or equal to 0, and p-type Alx5Ga1-x5The thickness of N is 10-500 nm.
The preparation method of the deep ultraviolet semiconductor light emitting diode (DUV LED) comprises the following steps:
firstly, etching grooves distributed in a pattern shape on a substrate by a holographic photoetching technology or a nanoimprint technology;
and secondly, baking the patterned substrate obtained in the first step at 1100-1300 ℃ in an MOCVD (metal organic chemical vapor deposition) reaction furnace to remove the foreign matters on the surface of the substrate.
And thirdly, depositing a semiconductor buffer layer with the thickness of 10-50 nm on the pattern substrate processed in the second step in an MOCVD reaction furnace, wherein a cavity structure is reserved in the semiconductor buffer layer.
And fourthly, depositing a Si-doped N-type semiconductor material layer with the thickness of 500-10000 nm on the pattern substrate obtained in the third step in an MOCVD reaction furnace, wherein a cavity structure is reserved on the N-type semiconductor material layer.
Fifthly, growing a multi-quantum well layer on the N-type semiconductor material layer obtained in the fourth step in an MOCVD reaction furnace, wherein the material of the multi-quantum well layer is Alx2Ga1-x2N/Alx3Ga1-x3N, ensuring that the coefficient of each component is more than or equal to 0 and less than or equal to x2 and less than or equal to 1, more than or equal to 1 and x2 and more than or equal to 0, more than or equal to 0 and less than or equal to x3 and less than or equal to 1, and more than or equal to 1 and x3 and more than or equal to 0, wherein the quantum barrier Al isx3Ga1-x3The thickness of N is 3-50 nm, and the quantum well Alx2Ga1-x2The thickness of N is 1-20 nm, the number of quantum wells is larger than 1, and a cavity structure is reserved in the multi-quantum well layer.
And sixthly, sequentially growing a P-type electron barrier layer which is 10-100 nm thick and is doped with Mg and a P-type semiconductor material transmission layer which is 10-500 nm thick and is doped with Mg on the multi-quantum well layer obtained in the fifth step.
The above-mentioned epitaxial structure of the DUV LED with a cavity can be obtained from known sources, and the operation process in the preparation method thereof can be grasped by those skilled in the art.
The invention has the substantive characteristics that:
the existing nano-pattern substrate technology aims at improving the lattice quality and releasing stress, and the principle of the existing nano-pattern substrate technology is that a nano-pattern can change the stress of an upper epitaxial layer during epitaxial growth so as to generate a cavity to release the stress, and after the stress is released through a buffer layer, the threading dislocation density can be reduced compared with external delay such as the direct growth of the buffer layer on a substrate, so that the crystal quality is improved, and the internal quantum efficiency is improved, as shown in figure 1. Meanwhile, in order to extend a thinner buffer layer and reduce cost, the shorter the cavity is, the better the cavity is controlled, so that the thinner buffer layer with better crystal quality can be obtained. However, at the top position after the polymerization of the cavity, a certain linear dislocation (a defect) occurs, since the cavity is polymerized in the buffer layer, the dislocation enters the n-type semiconductor material layer and the quantum well layer, which in turn affects the internal quantum efficiency of the quantum well.
The invention increases the size and depth of the substrate graph by improving the PSS technology to improve the epitaxial thickness required by cavity polymerization, so that the polymerization position of the cavity becomes higher, but different from the prior art, the thickness of the buffer layer is not greatly changed when the thickness required by cavity polymerization is increased, so that the polymerization position of the cavity exceeds the position of the quantum well, and the quantum well layer with the cavity structure is introduced. Therefore, linear dislocation cannot be introduced into the quantum well, the internal quantum efficiency is improved, and meanwhile, the cavity in the quantum well can be used as a scattering structure to prevent light from being scattered to the p-type semiconductor material transmission layer to be absorbed.
The invention has the beneficial effects that:
in the quantum well position in the prior art, a large number of dislocation defects which are diffused upwards and caused by cavity polymerization exist, the internal quantum efficiency of the quantum well layer is greatly influenced by the dislocation defects, and the AlGaN-based deep ultraviolet LED adopts pGaN as a p-type semiconductor material transmission layer and an ohmic contact layer, and most of light emitted from the upper surface is easily absorbed by the pGaN, so that the PSS technology is not ideal for improving the Light Extraction Efficiency (LEE).
According to the invention, the growth height of the cavity is increased by increasing the size and depth of the substrate pattern, and meanwhile, the thickness of the buffer layer is not greatly changed, so that the cavity can enter the quantum well layer, on one hand, the defect density of the active region is reduced, and the IQE is improved; on the other hand, the cavity in the quantum well can be used as a scattering structure, so that light can be prevented from being scattered to pGaN and absorbed by pGaN. The quantum well layer with the cavity structure provided by the invention not only greatly avoids linear dislocation defects caused by cavity combination from influencing the internal quantum efficiency of the quantum well, but also introduces the scattering structure into the quantum well layer, so that light can be effectively prevented from being scattered to pGaN, the scattering efficiency of the PSS is improved, and the light extraction efficiency of the DUV LED on the PSS is further improved. Simulation experiments prove that under the same other conditions, the light extraction efficiency of the device with the cavity structure in the quantum well is improved by about 6% compared with the light extraction efficiency of TM (transverse magnetic field) polarized light of the conventional PSS device.
Drawings
FIG. 1 is a side cross-sectional view of a DUV LED with a patterned substrate structure without a cavity in the conventional quantum well;
FIG. 2 is a side cross-sectional view of a DUV LED with a patterned substrate structure of quantum wells with cavities in example 1;
FIG. 3 is a schematic plan view of a patterned substrate;
FIG. 4 is a graph of light extraction efficiency of FDTD simulated TM polarized light versus cavity incorporation position;
FIG. 5 is a side cross-sectional view of the present invention with 4 sets of quantum well layers:
FIG. 6 is a side cross-sectional view of a DUV LED with a patterned substrate structure of quantum wells with cavities in example 2;
in the figure, 101 is a pattern substrate, 102 is a semiconductor buffer layer, 103 is an n-type semiconductor material layer, 104 is a multi-quantum well layer, 105 is a p-type electron barrier layer, 106 is a p-type semiconductor material transmission layer, 111 is a cavity, 112 is a groove, 501 is a quantum barrier, and 502 is a quantum well.
Detailed Description
The present invention is further described with reference to the following drawings and examples, which should not be construed as limiting the scope of the claims.
Fig. 1 is a side cross-sectional view of a DUV LED of a conventional patterned substrate structure without a cavity in a quantum well, in which a semiconductor buffer layer 102, an n-type semiconductor material layer 103, a multiple quantum well layer 104, a p-type electron blocking layer 105, and a p-type semiconductor material transport layer 106 are epitaxially grown in this order on a patterned substrate 101. The cavity 111 grows from the bottom of the semiconductor buffer layer 102 and the groove 112 on the patterned substrate 101 and merges before the multiple quantum well layer 104.
A large number of dislocations due to the different crystal orientation at the tapered top end of the cavity, which may extend directly into the mqw layer 104, thereby reducing the Internal Quantum Efficiency (IQE) of the deep ultraviolet LED;
the embodiment shown in fig. 2 shows a side cross-sectional view of a DUV LED having a quantum well patterned substrate structure with a cavity according to the present invention, in which a semiconductor buffer layer 102, an n-type semiconductor material layer 103, a multi-quantum well layer 104, a p-type electron blocking layer 105, and a p-type semiconductor material transport layer 106 are epitaxially grown in this order on a patterned substrate 101. The cavity 111 grows from the bottom of the semiconductor buffer layer 102 and the groove 112 on the patterned substrate 101, passes through the n-type semiconductor material layer 103 and the mqw layer 104, thereby forming the unique cavity-type quantum well structure of the present invention.
Example 1
The epitaxial structure of the DUV LED of the present embodiment, as shown in fig. 2, includes a patterned substrate 101, a semiconductor buffer layer 102, an n-type semiconductor material layer 103, a multi-quantum well layer 104, a p-type electron blocking layer 105, and a p-type semiconductor material transmission layer 106 in this order along an epitaxial direction;
as shown in FIG. 3, the pattern substrate 101 is etched with regularly arranged grooves 112, the grooves 112 are pits with a diameter of 500 nm-550 nm and a depth of 250 nm-300 nm, the grooves 112 are arranged in a pattern on the pattern substrate 101, which is a rectangular matrix (as shown in FIG. 3) with a pitch of 20 μm.
A cavity structure grows on each groove 112 on the surface of the pattern substrate 101, the cavity structure penetrates through the semiconductor buffer layer 102, the n-type semiconductor material layer 103 and the multi-quantum well layer 104, the top of the cavity structure is polymerized on the p-type electron barrier layer 105, and the polymerization depth of the cavity 111 in the p-type electron barrier layer 105 is 10-100 nm;
the cavity structure is a conical knot or a cylinder, and when the cavity structure is conical, the conical degree is 0.75-0.85.
The pattern substrate 101 is a sapphire substrate, the semiconductor buffer layer 102 is AlN, the thickness is 20nm, and a cavity 111 structure is reserved; the n-type semiconductor material layer 103 is Si-doped n-Al0.6Ga0.4N, the thickness is 1.05 μm, and a cavity 111 structure is reserved; the multi-quantum well layer is 4 groups of Al with the thickness of 3nm0.45Ga0.55N and 12nm thick Al0.56Ga0.44N, and a cavity 111 structure is reserved; the p-type electron blocking layer 105 is Mg-doped Al0.6Ga0.4N, the thickness is 20 nm; the p-type semiconductor material transmission layer is p-Al0.4Ga0.6N, thickness 150 nm. The formation of the cavity 111 is realized by a substrate pattern 112 on the pattern substrate 101. The cavity 111 starts to appear at the time of epitaxial AlN buffer layer 102 and remains in an unconjugated state at the time of epitaxial n-type semiconductor material layer 103 and quantum well layer 104;
the preparation method of the DUV LED epitaxial structure comprises the following steps:
firstly, a nano pattern 112 arranged according to a rectangular matrix is formed on a sapphire substrate 101 through holographic lithography or nanoimprint lithography, and the size (diameter) is 500-550 nm;
secondly, baking the pattern substrate 101 at 1200 ℃ in an MOCVD (metal organic chemical vapor deposition) reaction furnace to process the foreign matters on the surface of the substrate;
thirdly, depositing a semiconductor buffer layer 102 with the thickness of 20nm on the pattern substrate 101 processed in the second step in an MOCVD reaction furnace, wherein a cavity 111 structure is reserved in the semiconductor buffer layer 102;
fourthly, depositing a Si-doped N-type semiconductor material layer 103 with the thickness of 1.05 mu m on the graph substrate 101 obtained in the third step in an MOCVD reaction furnace, wherein a cavity 111 structure is reserved on the N-type semiconductor material layer 103;
fifth, a multiple quantum well layer 104 is grown on the N-type semiconductor material layer 103 obtained in the fourth step in the MOCVD reactor, as shown in fig. 5. The MQW layer 104 is made of Al0.45Ga0.55N/Al0.56Ga0.44N, wherein the quantum barrier 501 is Al0.56Ga0.44N with a thickness of 12nm and Al in the quantum well 502x2Ga1-x2N, the thickness is 3nm, the number of quantum wells is 4, and a cavity structure is reserved in the multi-quantum well layer;
sixthly, growing a P-type electron barrier layer 105 with the thickness of 20nm and a P-type semiconductor material transmission layer with the thickness of 150nm on the multi-quantum well layer 104 obtained in the fifth step in sequence, wherein the P-type electron barrier layer 105 is Mg-doped Al0.6Ga0.4The N, p-type semiconductor material transport layer 106 is Mg-dopedMiscellaneous Al0.4Ga0.6N。
Thus, a deep ultraviolet semiconductor light emitting diode device with a cavity 111 according to the present invention was obtained.
In the preparation of the invention, the combination height of the cavity 111 is controlled by controlling the shape of the substrate pattern 112, so that the cavity is not combined before the growth of the multiple quantum well layer. The reason is that during the growth of the epitaxial structure, a single crystal epitaxial layer is preferentially grown at the position without a pattern on the patterned substrate, then the epitaxial layer grown in the epitaxial process can slowly and transversely grow and finally be combined above the pattern on the patterned substrate, a large cavity can be generated in the slow combination process, the combination speed of the cavity can be delayed by increasing the area of the pattern, and further the height of the cavity is increased.
Fig. 4 shows comparative data of light extraction efficiency obtained by FDTD simulation using the DUV LED epitaxial structure of the present invention and the conventional DUV LED epitaxial structure, and it can be found from the graph that the light extraction efficiency of transverse magnetic field (TM) polarized light is significantly improved when the cavity merging position is located in the semiconductor buffer layer, the n-type semiconductor material layer, and the multiple quantum well layer, and the light extraction efficiency of the structure in which the cavity initially reaches the quantum well is improved by 6% compared to the light extraction efficiency of the conventional cavity located in the buffer layer.
Fig. 5 shows a multiple quantum well layer 104 structure having 4 sets of quantum wells of example 1, having a cavity 111 structure in a quantum barrier 501 and a quantum well 502 grown in this order. In the pattern substrate structure without a cavity in the quantum well in fig. 1, the cavity 111 is closed below the quantum well layer 104, a large amount of linear dislocation can be generated at the position after the cavity is polymerized, and the linear dislocation is diverged towards the upper quantum well, so that the lattice quality of the quantum well layer 104 is influenced, and the IQE is reduced; as shown in fig. 5, the cavity 111 is grown to a position of the quantum well and is not merged, so that the dislocation defect density in the quantum well with the cavity shown in fig. 5 is greatly reduced compared to the conventional quantum well structure shown in fig. 1. Meanwhile, the part of the cavity 111 in the quantum well also plays a role of a scattering center, and light can be effectively prevented from being scattered to the p-type semiconductor material transmission layer 106, so that the scattering efficiency is improved, and the light extraction efficiency of the DUV LED is further improved.
Example 2.
The other steps are the same as the embodiment 1, except that the size of the substrate pattern etched on the substrate by the nano-imprinting or holographic lithography technology is larger, the diameter is between 2 and 4 mu m, and the depth is between 1 and 2 mu m. This results in the cavity extending completely through the entire epitaxial structure, as shown in fig. 6, i.e. the cavity is left unclosed at the completion of the epitaxial structure growth.
In addition, the substrate patterns can be arranged in a ring-shaped radial mode, and the arrangement distance is 2-200 mu m; the substrate pattern can be rectangular strip or other irregular geometric patterns, and the area is 0.25-400 μm2(ii) a The substrate may be aluminum nitride, gallium nitride, 4H-SiC, R-plane alumina single crystal, gallium oxide, 6H-SiC, or the like, in addition to sapphire.
The DUV LED device epitaxial structure can be obtained from related raw materials through a general approach, and the operation process in the preparation method is possessed by the technical personnel in the technical field.
In combination with the results obtained in the embodiments, it is found that as the cavity approaches the quantum well layer or directly enters the quantum well layer, the defect density of the quantum well layer is significantly reduced during the epitaxial growth process, thereby improving the internal quantum efficiency. The invention can realize the control of the cavity only by controlling the shape and the excrement of the nano-pattern on the substrate, so that the invention has the characteristics of easy operation and low cost.
It can be seen from the above embodiments that the invention obtains a cavity structure penetrating through the buffer layer to the quantum well layer in the epitaxial growth by the PSS technology, and proposes a quantum well structure before the quantum well structure grows on the PSS and the cavity structure is completely merged, i.e. a novel quantum well layer with a cavity structure, so that the dislocation caused by merging the cavities in the epitaxial layer is generated on the quantum well structure, and the influence of the dislocation defect on the internal quantum efficiency of the quantum well is greatly reduced. In combination with the results obtained in the embodiments, it is found that as the cavity approaches the quantum well layer or directly enters the quantum well layer, the defect density of the quantum well layer is significantly reduced during the epitaxial growth process, thereby improving the internal quantum efficiency. The invention can realize the control of the height of the cavity only by a pattern substrate technology, so that the invention has the characteristics of controllable implementation and low cost.
The invention is not the best known technology.

Claims (6)

1. A deep ultraviolet semiconductor light emitting diode epitaxial structure is characterized in that the epitaxial structure sequentially comprises a pattern substrate, a semiconductor buffer layer, an n-type semiconductor material layer, a multi-quantum well layer, a p-type electronic barrier layer and a p-type semiconductor material transmission layer along an epitaxial direction;
the pattern substrate is etched with a groove which is a regular or irregular pit with the size of 500 nm-20 μm; the distance between every two adjacent grooves is 5-30 mu m;
wherein, on every recess of figure substrate surface, all upwards vertical growth has a cavity structure, and the cavity structure passes semiconductor buffer layer, n type semiconductor material layer, multiple quantum well layer, and the top position of cavity structure is following three kinds:
the first is polymerized in a p-type electron blocking layer, and the polymerization depth of a cavity structure in the p-type electron blocking layer is 10-100 nm;
or, secondly, the second type semiconductor material is polymerized in the p-type semiconductor material transmission layer after continuously penetrating through the p-type electron blocking layer, and the polymerization depth of the cavity structure in the p-type semiconductor material transmission layer is 10-500 nm;
or thirdly, the cavity structure continues to penetrate through the p-type electron blocking layer and the p-type semiconductor material transmission layer, the cavity structure is not polymerized, and circular holes are formed on the surface of the p-type semiconductor material transmission layer.
2. The deep ultraviolet semiconductor light emitting diode epitaxial structure of claim 1, wherein the cavity structure is tapered or cylindrical, and when tapered, the taper is between 0.75 and 0.85.
3. The deep ultraviolet semiconductor light emitting diode epitaxial structure of claim 1, wherein the projection shape of the groove is circular or rectangular, and the depth is between 200nm and 20 μm.
4. The deep ultraviolet semiconductor light emitting diode epitaxial structure of claim 1 wherein the grooves are regularly arranged to form a rectangular array or a circular radial pattern on the substrate.
5. The deep ultraviolet semiconductor light emitting diode epitaxial structure according to claim 1, wherein the patterned substrate is a sapphire, SiC, Si, AlN, GaN or quartz glass patterned substrate, and the difference in the epitaxial growth direction can be classified into a polar plane [0001] substrate, a semipolar plane [11-22] substrate or a nonpolar plane [1-100] substrate;
the semiconductor buffer layer is AlN, has the thickness of 0.1-10 mu m and has a cavity structure;
the n-type semiconductor material layer is made of silicon-doped n-type Alx1Ga1-x1N, ensuring that the coefficient of each component is more than or equal to 0 and less than or equal to x1 and less than or equal to 1, more than or equal to 1-x1-y1 and more than or equal to 0, and the thickness is 0.1-10 mu m;
the material of the multi-quantum well layer is Alx2Ga1-x2N/Alx3Ga1-x3N, wherein the component coefficients are more than or equal to 0 and less than or equal to x2 and less than or equal to 1, more than or equal to 1 and more than or equal to 1-x2 and more than or equal to 0, more than or equal to 0 and less than or equal to x3 and less than or equal to 1, more than or equal to 1-x3 and more than or equal to 0, the forbidden bandwidth of the quantum barrier is higher than that of the quantum well, the number of the quantum wells is more than or equal tox2Ga1-x2N is 1-20 nm thick, and quantum barrier Alx3Ga1-x3The N is 3-50 nm in thickness and has a cavity structure;
the p-type electron blocking layer is made of magnesium-doped p-type Alx4Ga1-x4N, ensuring that the coefficient of each component is not less than 0 and not more than x4 and not more than 1,1 is not less than 1-x4 and not less than 0, and the thickness is 10-100 nm;
the p-type semiconductor material transmission layer is p-type Alx5Ga1-x5N, ensuring that the coefficient of each component is more than or equal to 0 and less than or equal to x5 and less than or equal to 1,1 is more than or equal to 1-x5 is more than or equal to 0, p type Alx5Ga1-x5The thickness of N is 1-500 nm.
6. A method of fabricating a deep ultraviolet semiconductor light emitting diode epitaxial structure as claimed in claim 1, the method comprising the steps of:
firstly, etching grooves distributed in a pattern shape on a substrate by a holographic photoetching technology or a nanoimprint technology;
secondly, baking the patterned substrate obtained in the first step at 1100-1300 ℃ in an MOCVD (metal organic chemical vapor deposition) reaction furnace to remove foreign matters on the surface of the substrate;
thirdly, depositing a semiconductor buffer layer with the thickness of 10-50 nm on the pattern substrate processed in the second step in an MOCVD reaction furnace, wherein a cavity structure is reserved in the semiconductor buffer layer;
fourthly, depositing a Si-doped N-type semiconductor material layer with the thickness of 500-10000 nm on the graph substrate obtained in the third step in an MOCVD reaction furnace, wherein a cavity structure is reserved on the N-type semiconductor material layer;
fifthly, growing a multi-quantum well layer on the N-type semiconductor material layer obtained in the fourth step in an MOCVD reaction furnace, wherein the material of the multi-quantum well layer is Alx2Ga1-x2N/Alx3Ga1-x3N, ensuring that the coefficient of each component is more than or equal to 0 and less than or equal to x2 and less than or equal to 1, more than or equal to 1 and x2 and more than or equal to 0, more than or equal to 0 and less than or equal to x3 and less than or equal to 1, and more than or equal to 1 and x3 and more than or equal to 0, wherein the quantum barrier Al isx3Ga1-x3The thickness of N is 3-50 nm, and the quantum well Alx2Ga1-x2The thickness of N is 1-20 nm, the number of quantum wells is more than 1, and a cavity structure is reserved in the multi-quantum well layer;
and sixthly, sequentially growing a P-type electron barrier layer which is 10-100 nm thick and is doped with Mg and a P-type semiconductor material transmission layer which is 10-500 nm thick and is doped with Mg on the multi-quantum well layer obtained in the fifth step.
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