A deep ultraviolet LED epitaxial structure and a preparation method thereof

Abstract

The present invention relates to the technical field of semiconductor structures, and particularly relates to a deep ultraviolet LED epitaxial structure and a preparation method thereof. The present invention provides a deep ultraviolet LED epitaxial structure, which includes a substrate, a buffer layer, an AlN intrinsic layer, a stress regulation layer, an electron injection layer, a current diffusion layer, a multi-quantum well active layer, a composite electron blocking layer, a hole injection layer, and a P-type contact layer that are sequentially stacked from bottom to top; the composite electron blocking layer includes a first AlGaN main structure layer, an absorption layer, and a second AlGaN main structure layer that are sequentially stacked from bottom to top. The deep ultraviolet LED epitaxial structure of the present invention has a high photoelectric conversion efficiency and an aging life.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor structures, and particularly to a deep ultraviolet LED epitaxial structure and a preparation method thereof. Background Art

[0002] At present, as an outstanding representative of wide-bandgap semiconductor materials, group III nitrides have realized high-efficiency solid-state light source devices such as blue and green light-emitting diodes (LEDs) and lasers, and have achieved great success in applications such as flat panel displays and white lighting. In the past decade, people have expected to apply this high-efficiency light-emitting material to the ultraviolet band to meet the growing demand for ultraviolet light sources. According to its biological effects, the ultraviolet band is usually divided into: long-wave ultraviolet (UVA, 320-400 nm), medium-wave ultraviolet (UVB, 280-320 nm), short-wave ultraviolet (UVC, 200-280 nm), and vacuum ultraviolet (VUV, 10-200 nm). Although ultraviolet light cannot be perceived by the human eye, its applications are very extensive. Long-wave ultraviolet light sources have great application prospects in fields such as medical treatment, ultraviolet curing, ultraviolet lithography, information storage, and plant lighting; while medium-wave ultraviolet and short-wave ultraviolet (collectively referred to as deep ultraviolet) play an irreplaceable role in sterilization and disinfection, water purification, biochemical detection, and non-line-of-sight communication. At present, traditional ultraviolet light sources are mainly mercury lamps, which have the disadvantages of large volume, high power consumption, high voltage, and environmental pollution, and are not conducive to their application in daily life and special environments. Therefore, people are urgently hoping to develop an efficient semiconductor ultraviolet light source device to replace the traditional mercury lamp. Existing research shows that AlGaN in group III nitrides is the best candidate material for preparing semiconductor ultraviolet light source devices. AlGaN-based deep ultraviolet LEDs have many advantages such as non-toxic environmental protection, small and portable, low power consumption, low voltage, easy integration, long life, and wavelength tunability, and are expected to make breakthrough progress and wide applications in the next few years, and gradually replace traditional ultraviolet mercury lamps.

[0003] At present, the biggest problems restricting the application of deep ultraviolet LEDs are their low photoelectric conversion efficiency (only below 5%) and high device heat generation. A main reason for the low efficiency of high-Al-component AlGaN-based deep ultraviolet LEDs is the obvious electron overflow effect. Electrons from the electron injection layer cross the electron blocking layer to the hole injection layer, causing non-radiative recombination light in the hole injection layer, thereby reducing the internal quantum efficiency. At the same time, short-wave photons have high energy and are prone to total reflection and cannot escape from the structure, and finally annihilate and convert into heat within the structure. Low photoelectric conversion efficiency and high heat generation further affect the photoelectric conversion efficiency and aging life of the device. Summary of the Invention

[0004] The object of the present invention is to provide a deep ultraviolet LED epitaxial structure and a preparation method thereof, and the deep ultraviolet LED epitaxial structure has a high photoelectric conversion efficiency and an aging life.

[0005] In order to achieve the above object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a deep ultraviolet LED epitaxial structure, which includes a substrate, a buffer layer, an AlN intrinsic layer, a stress regulation layer, an electron injection layer, a current diffusion layer, a multi-quantum well active layer, a composite electron blocking layer, a hole injection layer, and a P-type contact layer that are sequentially stacked from bottom to top;

[0007] The composite electron blocking layer includes a first AlGaN main structure layer, an absorption layer, and a second AlGaN main structure layer that are sequentially stacked from bottom to top.

[0008] Preferably, the atomic percentage content of Al in the first AlGaN main structure layer and the second AlGaN main structure layer is independently 45% to 75%.

[0009] Preferably, the first AlGaN main structure layer and the second AlGaN main structure layer are independently a single-layer AlGaN layer or a superlattice layer alternately stacked.

[0010] Preferably, the thickness of the first AlGaN main structure layer and the second AlGaN main structure layer is ≥5 nm.

[0011] Preferably, the absorption layer includes an InGaN absorption layer and an AlGaN absorption layer that are alternately stacked from bottom to top in sequence.

[0012] Preferably, the number of periods of the alternate stacking is 1 to 3.

[0013] Preferably, the thickness of the InGaN absorption layer is 1 to 5 nm;

[0014] The atomic percentage content of In in the InGaN absorption layer is 1% to 10%.

[0015] Preferably, the thickness of the AlGaN absorption layer is 4 to 15 nm;

[0016] The atomic percentage content of Al in the AlGaN absorption layer is 45% to 75%.

[0017] Preferably, the atomic percentage content of Al in the first AlGaN main structure layer and the second AlGaN main structure layer is greater than the atomic percentage content of Al in the AlGaN absorption layer.

[0018] The present invention also provides a method for preparing the deep ultraviolet LED epitaxial structure described in the above technical solution, including the following steps:

[0019] After successively growing a buffer layer, an AlN intrinsic layer, a stress regulation layer, an electron injection layer, a current diffusion layer, a multi-quantum well active layer, a composite electron blocking layer, a hole injection layer, and a P-type contact layer on the surface of the substrate, annealing treatment is performed to obtain the deep ultraviolet LED epitaxial structure.

[0020] The present invention provides a deep ultraviolet LED epitaxial structure, including a substrate, a buffer layer, an AlN intrinsic layer, a stress regulation layer, an electron injection layer, a current diffusion layer, a multi-quantum well active layer, a composite electron blocking layer, a hole injection layer, and a P-type contact layer that are sequentially stacked from bottom to top; the composite electron blocking layer includes a first AlGaN main structure layer, an absorption layer, and a second AlGaN main structure layer that are sequentially stacked from bottom to top. In the traditional structure, there is a large energy band offset between the conduction bands of the last barrier layer and the electron blocking layer in the active region, which usually helps to block the electron overflow from the quantum well region. However, at the same time, there is also a large polarization electric field in the electron blocking layer, which will reduce the effective barrier height for blocking electrons. The polarization electric field existing between the last barrier layer and the electron blocking layer will also cause the valence band energy level to bend downward significantly, thus forming an effective barrier for holes, which directly leads to a low hole injection efficiency. In order to effectively block the electron overflow and improve the hole injection efficiency at the same time, the present invention introduces an absorption layer in the composite electron blocking layer. First, it can reduce the polarization electric field between the last barrier layer and the electron blocking layer, while achieving efficient electron blocking, reducing the influence on hole injection; at the same time, the absorption layer has a good confinement effect on the overflow electrons, enabling the overflow electrons to recombine with holes in the absorption layer, emitting UVA photons, and avoiding the overflow electrons flowing to the P-type injection layer to consume holes or being captured by defects for non-radiative recombination; effectively reducing the problem of the decrease in hole injection efficiency caused by electron overflow and effectively improving the photoelectric conversion efficiency under high current density. At the same time, the introduction of the absorption layer can also achieve the light conversion effect of UVC, converting the UVC photons that cannot escape due to reflection in the structure into UVA photons and escaping from the structure, reducing the UVC photons that cannot escape in the structure, and thus reducing the overall heat generation of the structure. Finally, it provides higher optical power and less heat generation for the subsequent fabricated high-power light-emitting devices. Therefore, the deep ultraviolet LED epitaxial structure described in the present invention has a high photoelectric conversion efficiency and aging life. Description of the Drawings

[0021] Figure 1Schematic structural diagram of the deep ultraviolet LED epitaxial structure according to the present invention; wherein, 10 - substrate, 11 - buffer layer, 12 - AlN intrinsic layer, 13 - stress regulation layer, 14 - electron injection layer, 15 - current diffusion layer, 16 - multi - quantum well active layer, 17 - composite electron blocking layer, 18 - hole injection layer, 19 - P - type contact layer, 17a1 - first AlGaN main structure layer, 17b - absorption layer, 17b1 - InGaN absorption layer, 17b2 - AlGaN absorption layer, 17a2 - second AlGaN main structure layer;

[0022] Figure 2 Schematic diagram of the preparation process of the deep ultraviolet LED epitaxial structure according to the present invention;

[0023] Figure 3 For Example 1 and Comparative Example 1 (corresponding to Figure 3 the reference example in ), the brightness - current relationship diagram of the flip - chip structure chip prepared from the deep ultraviolet LED epitaxial structure;

[0024] Figure 4 For Example 1 and Comparative Example 1 (corresponding to Figure 4 the reference example in ), the spectrogram of the flip - chip structure chip prepared from the deep ultraviolet LED epitaxial structure. Detailed implementation manners

[0025] The present invention provides a deep ultraviolet LED epitaxial structure, including a substrate, a buffer layer, an AlN intrinsic layer, a stress regulation layer, an electron injection layer, a current diffusion layer, a multi - quantum well active layer, a composite electron blocking layer, a hole injection layer, and a P - type contact layer which are sequentially stacked from bottom to top;

[0026] The composite electron blocking layer includes a first AlGaN main structure layer, an absorption layer, and a second AlGaN main structure layer which are sequentially stacked from bottom to top.

[0027] In the present invention, the material of the substrate is preferably one or more of sapphire, SiC, GaN, and Si, and more preferably sapphire.

[0028] The present invention has no special limitation on the materials of the buffer layer, the AlN intrinsic layer, the stress regulation layer, the electron injection layer, the current diffusion layer, the multi - quantum well active layer, the hole injection layer, and the P - type contact layer. III - V nitride semiconductor materials well - known to those skilled in the art (such as GaN, InN, AlN, InGaN, AlGaN, or AlInGaN) can be used.

[0029] The present invention does not impose any special limitations on the thicknesses of the buffer layer, the AlN intrinsic layer, the stress regulation layer, the electron injection layer, the current diffusion layer, the multi-quantum well active layer, the hole injection layer, and the P-type contact layer, and the thicknesses well-known to those skilled in the art can be adopted.

[0030] In an embodiment of the present invention, the material of the buffer layer is preferably Al x1 Ga 1-x1 N, where x1 is preferably 0.2 to 0.5, specifically 0.5; the thickness is specifically 20 nm.

[0031] In an embodiment of the present invention, the material of the AlN intrinsic layer is specifically AlN, and the thickness is specifically 1500 nm.

[0032] In an embodiment of the present invention, the stress regulation layer is specifically a superlattice layer formed by alternately stacking an AlN layer and an AlGaN layer in sequence (denoted as the stress regulation layer of the AlN / AlGaN superlattice). The material of the AlN layer is AlN, and the thickness of the AlN layer is 5 nm; the material of the AlGaN layer is Al x2 Ga 1-x2 N, where x2 is preferably 0.45 to 0.75, specifically 0.55, the thickness of the AlGaN layer is 5 nm; the number of cycles of the alternate stacking is 20. The total thickness of the stress regulation layer is 200 nm.

[0033] In an embodiment of the present invention, the material of the electron injection layer is Al x3 Ga 1-x3 N, where x3 is preferably 0.45 to 0.75, specifically 0.55. The concentration of Si doping in the Al x3 Ga 1-x3 N is 5×10 17 ~2×10 19 cm -3 ,specifically 1×10 19 cm -3 ,and the thickness of the electron injection layer is 2000 nm.

[0034] In an embodiment of the present invention, the material of the current diffusion layer is Al x4 Ga 1-x4 N, where x4 is preferably 0.45 to 0.75, specifically 0.55. The concentration of Si doping in the Al x4 Ga 1-x4 N is 5×10 17 ~5×10 18 cm -3 ,specifically 1×10 18 cm -3, the thickness of the electron injection layer is 200 nm.

[0035] In an embodiment of the present invention, the multi-quantum well active layer includes alternately stacked AlGaN quantum barriers and AlInGaN quantum wells; the number of periods of the alternate stacking is preferably 3 to 12, specifically 5; the material of the AlGaN quantum barrier is Al x5 Ga 1-x5 N, wherein x5 is preferably 0.45 to 0.65, specifically 0.58, and the thickness is 10 nm; the material of the AlInGaN quantum well is Al x6 In y6 Ga 1-x6-y6 N, wherein x6 is preferably 0.4 to 0.5, specifically 0.45, y is preferably 0.005 to 0.02, specifically 0.005, and the thickness is 2 nm.

[0036] In an embodiment of the present invention, the material of the hole injection layer is preferably Al x7 Ga 1-x7 N, wherein x7 is preferably 0.55 to 0.75, specifically 0.65; the Mg doping concentration in the Al x7 Ga 1-x7 N is preferably 2×10 19 ~2×10 20 cm -3 , specifically 1×10 20 cm -3 ; the thickness is 20 nm.

[0037] In an embodiment of the present invention, the material of the P-type contact layer is GaN, and the Mg doping concentration in the GaN > 5×10 20 cm -3 , specifically 8×10 20 cm -3 ; the thickness is 10 nm.

[0038] In the present invention, the atomic percentage content of Al in the first AlGaN main structure layer and the second AlGaN main structure layer is independently preferably 45% to 75%, more preferably 50% to 70%, and most preferably 60% to 70%.

[0039] In the present invention, the thickness of the first AlGaN main structure layer and the second AlGaN main structure layer is preferably ≥5 nm. In the present invention, the first AlGaN main structure layer and the second AlGaN main structure layer are independently preferably a single AlGaN layer or a superlattice layer arranged in an alternating stack; when the first AlGaN main structure layer or the second AlGaN main structure layer is preferably a superlattice layer arranged in an alternating stack, the superlattice layer preferably includes Al x8 Ga 1-x8 N layers and Al x9 Ga 1-x9 N layers; wherein the value range of x8 is preferably 0.45 to 0.6, and the value range of x9 is preferably 0.6 to 0.70; the thickness of the Al x8 Ga 1-x8 N layer is preferably 1 to 5 nm, more preferably 2 to 4 nm, and most preferably 3 nm; the thickness of the Al x9 Ga 1-x9 N layer is preferably 1 to 5 nm, more preferably 2 to 4 nm, and most preferably 3 nm. In the present invention, the number of alternating stacks is preferably 10. When the first AlGaN main structure layer or the second AlGaN main structure layer is preferably a single AlGaN layer, the material of the single AlGaN layer is preferably Al x10 Ga 1-x10 N, wherein the value range of x10 is preferably 0.45 to 0.75, more preferably 0.50 to 0.70, and most preferably 0.7. The thickness of the single AlGaN layer is preferably 5 to 50 nm, more preferably 5 to 30 nm, and most preferably 20 nm. In a specific embodiment of the present invention, the first AlGaN main structure layer and the second AlGaN main structure layer are Al 0.70 Ga 0.30 N with a thickness of 20 nm.

[0040] In the present invention, the absorption layer preferably includes an InGaN absorption layer and an AlGaN absorption layer arranged in an alternating stack from bottom to top. In the present invention, the number of alternating stacks is preferably 1 to 3, more preferably 2. In the present invention, the thickness of the InGaN absorption layer is preferably 1 to 5 nm, more preferably 2 to 4 nm, and most preferably 3 nm; the thickness of the AlGaN absorption layer is preferably 4 to 15 nm, more preferably 6 to 12 nm, and most preferably 8 to 10 nm; the atomic percentage content of Al in the AlGaN absorption layer is preferably 45% to 75%, more preferably 50% to 70%, and most preferably 55% to 60%.

[0041] In the present invention, the atomic percentage content of Al in both the first AlGaN main structure layer and the second AlGaN main structure layer is preferably greater than the atomic percentage content of Al in the AlGaN absorption layer.

[0042] The present invention also provides a method for preparing the deep ultraviolet LED epitaxial structure described in the above technical solution, comprising the following steps:

[0043] After successively growing a buffer layer, an AlN intrinsic layer, a stress regulation layer, an electron injection layer, a current diffusion layer, a multi-quantum well active layer, a composite electron blocking layer, a hole injection layer, and a P-type contact layer on the surface of the substrate, annealing treatment is carried out to obtain the deep ultraviolet LED epitaxial structure.

[0044] In the present invention, the preparation method is preferably carried out in MOCVD.

[0045] In the present invention, the growth of the buffer layer is preferably carried out under the conditions of 75 - 200 torr and 500 - 900 °C.

[0046] In the present invention, the growth of the AlN intrinsic layer is preferably carried out under the conditions of 75 - 200 torr and 1000 - 1400 °C.

[0047] In the present invention, the growth of the stress regulation layer is preferably carried out under the conditions of 75 - 200 torr and 1000 - 1400 °C.

[0048] In the present invention, the growth of the electron injection layer is preferably carried out under the conditions of 75 - 200 torr and 1000 - 1350 °C, and at the same time, Si source doping is introduced to provide N-type electrons.

[0049] In the present invention, the growth of the current diffusion layer is preferably carried out under the conditions of 75 - 200 torr and 900 - 1250 °C.

[0050] In the present invention, the growth of the multi-quantum well active layer is preferably carried out under the conditions of 75 - 200 torr and 900 - 1250 °C.

[0051] In the present invention, the growth of both the first AlGaN main structure layer and the second AlGaN main structure layer in the composite electron blocking layer is preferably carried out under the conditions of 75 - 200 torr and 1000 - 1400 °C.

[0052] In the present invention, the growth of the absorption layer is preferably carried out under the conditions of 75 - 200 torr and 750 - 1100 °C.

[0053] In the present invention, the growth of the hole injection layer is preferably carried out under the conditions of 75 - 200 torr and 900 - 1250 °C, while introducing an Mg source.

[0054] In the present invention, the growth of the P-type contact layer is preferably carried out under the conditions of 75 - 200 torr and 700 - 1000 °C, while introducing an Mg source.

[0055] In the present invention, the annealing treatment is preferably carried out under the conditions of a nitrogen atmosphere, 75 - 200 torr and 600 - 1000 °C; the time of the annealing treatment is preferably 5 - 30 min.

[0056] The deep ultraviolet LED epitaxial structure and its preparation method provided by the present invention will be described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0057] Example 1

[0058] Place the sapphire substrate in MOCVD. Under the conditions of 75 torr and 900 °C, grow a buffer layer with a thickness of 20 nm on the C surface of the sapphire substrate (the material of the buffer layer is Al 0.5 Ga 0.5 N);

[0059] Under the conditions of 100 torr and 1300 °C, grow an AlN intrinsic layer with a thickness of 1500 nm on the surface of the buffer layer;

[0060] Under the conditions of 100 torr and 1300 °C, grow a stress control layer of AlN / AlGaN superlattice with a total thickness of 120 nm on the surface of the AlN intrinsic layer (the stress control layer includes alternately stacked AlN layers and AlGaN layers. The thickness of the AlN layer is 5 nm, and the material is AlN; the thickness of the AlGaN layer is 5 nm, and the material is Al 0.55 Ga 0.45 N, and the number of alternately stacked periods is 20);

[0061] Under the conditions of 100 torr and 1300 °C, grow a Si-doped AlGaN electron injection layer with a thickness of 2000 nm on the surface of the stress control layer of the AlN / AlGaN superlattice (the material of the AlGaN electron injection layer is Al 0.55 Ga 0.45 N, the doping concentration of Si is 1×10 19 cm -3 );

[0062] Under the conditions of 100 torr and 1200 °C, an AlGaN current diffusion layer with a thickness of 200 nm is grown on the surface of the Si-doped AlGaN electron injection layer (the material of the AlGaN current diffusion layer is Al 0.55 Ga 0.45 N, and the doping concentration of Si is 1×10 18 cm -3 );

[0063] Under the conditions of 100 torr and 980 °C, a multi-quantum well active layer of AlGaN quantum barrier / AlInGaN quantum well is sequentially and alternately grown on the surface of the AlGaN current diffusion layer (the number of alternately stacked periods is 5; the atomic percentage of Al in the AlGaN quantum barrier is 58%, and the thickness is 10 nm; the atomic percentage of Al in the AlInGaN quantum well is 45%, and the thickness is 2 nm);

[0064] Under the conditions of 100 torr and 1300 °C, a first AlGaN main structure layer with a thickness of 20 nm and an Al content of 70% is grown on the surface of the multi-quantum well active layer (the material of the first AlGaN main structure layer is Al 0.7 Ga 0.3 N);

[0065] Under the conditions of 100 torr and 980 °C, an InGaN layer with a thickness of 2 nm and an In content of 5% and an AlGaN layer with a thickness of 8 nm and an Al content of 55% are sequentially grown on the surface of the first AlGaN main structure layer to obtain an absorption layer;

[0066] Under the conditions of 100 torr and 1300 °C, a second AlGaN main structure layer with a thickness of 20 nm and an Al content of 70% is grown on the surface of the absorption layer (the material of the second AlGaN main structure layer is Al 0.7 Ga 0.3 N), to obtain a composite electron blocking layer;

[0067] Under the conditions of 100 torr and 1200 °C, a Mg source is introduced, and an AlGaN hole injection layer with a thickness of 20 nm is grown on the surface of the composite electron blocking layer (the material of the AlGaN hole injection layer is Al 0.65 Ga 0.35 N, and the atomic percentage of Mg is 1×10 20 cm -3 );

[0068] Under the conditions of 100 torr and 880 °C, a Mg source is introduced, and a P-type GaN contact layer with a thickness of 10 nm (atomic percentage of Mg is 8×10 20 cm -3 ) is grown on the surface of the AlGaN hole injection layer;

[0069] Under the conditions of 200 torr, 700 °C and N2 atmosphere, annealing is carried out for 20 min to obtain the deep ultraviolet LED epitaxial structure.

[0070] Comparative Example 1

[0071] Referring to Example 1, the difference is that under the conditions of 100 torr and 1300 °C, an AlGaN structure layer with a thickness of 40 nm and an Al doping amount of 70% is grown on the surface of the multi-quantum well active layer (the material of the AlGaN main structure layer is Al 0.7 Ga 0.3 N), to obtain an electron blocking layer.

[0072] Test Example 1

[0073] The deep ultraviolet LED epitaxial structures described in Example 1 and Comparative Example 1 are made into flip-chip structure chips with a size of 20 mil * 20 mil, and the optical power is compared under a driving current of 1 - 400 mA;

[0074] Figure 3 is the brightness-current relationship diagram of the flip-chip structure chips prepared from the deep ultraviolet LED epitaxial structures described in Example 1 and Comparative Example 1 (corresponding to the reference example in Figure 3 ). It can be seen that under high-current driving, the optical power of the deep ultraviolet LED epitaxial structure described in Example 1 is significantly higher than that of Comparative Example 1, and the current density at the brightness inflection point is also larger. This shows that in the composite electron blocking layer of the deep ultraviolet LED epitaxial structure described in Example 1, with the pouring of the absorption layer, the problem of the decrease in hole injection efficiency caused by electron overflow can be effectively reduced, and the photoelectric conversion efficiency under high current density is effectively improved; Figure 3 is the spectral diagram of the flip-chip structure chips prepared from the deep ultraviolet LED epitaxial structures described in Example 1 and Comparative Example 1 (corresponding to the reference example in

[0075] Figure 4 is the spectral diagram of the flip-chip structure chips prepared from the deep ultraviolet LED epitaxial structures described in Example 1 and Comparative Example 1 (corresponding to the reference example in Figure 4 ). It can be seen from Figure 4It can be seen that in Example 1, the pouring of the absorption layer can improve the light conversion efficiency of UVC, convert the UVC photons that cannot escape due to reflection inside the structure into UVA photons and escape from the structure, reduce the heat generated by the annihilation of the UVC photons that cannot escape inside the structure and then reduce the overall heat generation of the structure. The reduction of heat generation effectively improves the performance of the device. Finally, not only the light output power in the UVA band is increased, but also the light power in the UVC band increases instead of decreasing.

[0076] Example 2

[0077] Referring to Example 1, the difference lies in the preparation process of the composite electron blocking layer:

[0078] Under the conditions of 100 torr and 1300 °C, a first AlGaN main structure layer with a thickness of 20 nm and an Al doping content of 70% is grown on the surface of the multiple quantum well active layer (the material of the first AlGaN main structure layer is Al 0.7 Ga 0.3 N);

[0079] Under the conditions of 100 torr and 980 °C, two cycles of InGaN layers with a thickness of 2 nm and an In doping content of 5% and AlGaN layers with a thickness of 8 nm and an Al doping content of 55% are sequentially grown on the surface of the first AlGaN main structure layer to obtain an absorption layer;

[0080] Under the conditions of 100 torr and 1300 °C, a second AlGaN main structure layer with a thickness of 20 nm and an Al doping content of 70% is grown on the surface of the absorption layer (the material of the second AlGaN main structure layer is Al 0.7 Ga 0.3 N), to obtain a composite electron blocking layer.

[0081] Example 3

[0082] Referring to Example 1, the difference lies in the preparation process of the composite electron blocking layer:

[0083] Under the conditions of 100 torr and 1300 °C, a first AlGaN main structure layer with a thickness of 20 nm and an Al doping content of 70% is grown on the surface of the multiple quantum well active layer (the material of the first AlGaN main structure layer is Al 0.7 Ga 0.3 N);

[0084] Under the conditions of 100 torr and 980 °C, an InGaN layer with a thickness of 2 nm and an In doping content of 2% and an AlGaN layer with a thickness of 8 nm and an Al doping content of 55% are sequentially grown on the surface of the first AlGaN main structure layer to obtain an absorption layer;

[0085] Under the conditions of 100 torr and 1300 °C, a second AlGaN main structure layer with a thickness of 20 nm and an Al doping content of 70% (the material of the second AlGaN main structure layer is Al 0.7 Ga 0.3 N) is grown on the surface of the absorption layer to obtain a composite electron blocking layer.

[0086] Example 4

[0087] Referring to Example 1, the difference lies in the preparation process of the composite electron blocking layer:

[0088] Under the conditions of 100 torr and 1300 °C, a first AlGaN main structure layer with a thickness of 30 nm and an Al doping content of 70% (the material of the first AlGaN main structure layer is Al 0.7 Ga 0.3 N) is grown on the surface of the multi-quantum well active layer;

[0089] Under the conditions of 100 torr and 980 °C, an InGaN layer with a thickness of 2 nm and an In doping content of 5% and an AlGaN layer with a thickness of 8 nm and an Al doping content of 55% are successively grown on the surface of the first AlGaN main structure layer to obtain an absorption layer;

[0090] Under the conditions of 100 torr and 1300 °C, a second AlGaN main structure layer with a thickness of 10 nm and an Al doping content of 70% (the material of the second AlGaN main structure layer is Al 0.7 Ga 0.3 N) is grown on the surface of the absorption layer to obtain a composite electron blocking layer.

[0091] Example 5

[0092] Referring to Example 1, the difference lies in the preparation process of the composite electron blocking layer:

[0093] Under the conditions of 100 torr and 1300 °C, a first AlGaN main structure layer with a thickness of 20 nm and an Al doping content of 70% (the material of the first AlGaN main structure layer is Al 0.7 Ga 0.3 N) is grown on the surface of the multi-quantum well active layer;

[0094] Under the conditions of 100 torr and 980 °C, an InGaN layer with a thickness of 3 nm and an In doping content of 5% and an AlGaN layer with a thickness of 8 nm and an Al doping content of 55% are successively grown on the surface of the first AlGaN main structure layer to obtain an absorption layer;

[0095] Under the conditions of 100 torr and 1300 °C, a second AlGaN main structure layer with a thickness of 20 nm and an Al doping content of 70% (the material of the second AlGaN main structure layer is Al 0.7 Ga 0.3 N) is grown on the surface of the absorption layer to obtain a composite electron blocking layer.

[0096] Example 6

[0097] Referring to Example 1, the difference lies in the preparation process of the composite electron blocking layer:

[0098] Under the conditions of 100 torr and 1300 °C, a first AlGaN main structure layer with a thickness of 20 nm and an Al doping content of 70% (the material of the first AlGaN main structure layer is Al 0.7 Ga 0.3 N) is grown on the surface of the multiple quantum well active layer;

[0099] Under the conditions of 100 torr and 980 °C, an InGaN layer with a thickness of 2 nm and an In doping content of 5% and an AlGaN layer with a thickness of 12 nm and an Al doping content of 55% are successively grown on the surface of the first AlGaN main structure layer to obtain an absorption layer;

[0100] Under the conditions of 100 torr and 1300 °C, a second AlGaN main structure layer with a thickness of 20 nm and an Al doping content of 70% (the material of the second AlGaN main structure layer is Al 0.7 Ga 0.3 N) is grown on the surface of the absorption layer to obtain a composite electron blocking layer.

[0101] Test Example 2

[0102] The deep ultraviolet LED epitaxial structures described in Examples 1 to 6 and Comparative Example 1 are fabricated into flip-chip structure chips of 20 mil * 20 mil and tested under a driving current of 100 mA;

[0103] The test results are shown in Table 1:

[0104] Table 1 Performance parameters of the flip-chip structure chips fabricated from the deep ultraviolet LED epitaxial structures described in Examples 1 to 6 and Comparative Example 1

[0105]

[0106]

[0107] As can be seen from Table 1, the parameter changes in the composite electron blocking layer can effectively optimize and reduce the key parameters of electron overflow and the wavelength of UVC converted to UVA.

[0108] Test Example 3

[0109] The flip-chip structure chips with the deep ultraviolet LED epitaxial structures described in Examples 1 to 2 and Comparative Example 1 were fabricated into 20 mil * 20 mil chips and aged for 168 hours at a current of 120 mA; the aging performance test was carried out at a driving current of 100 mA;

[0110] The test results are shown in Table 2:

[0111] Table 2 Aging parameters of the flip-chip structure chips prepared from the deep ultraviolet LED epitaxial structures described in Examples 1 to 2 and Comparative Example 1

[0112]

[0113]

[0114] Note: In Table 2, U(V) is the forward voltage measured at a forward current of 100 mA; IR(μA) is the reverse leakage current measured at a reverse voltage of 8 V, Φe(mW) is the luminous intensity measured at a forward current of 100 mA, and WP(nm) is the peak wavelength measured at a forward current of 100 mA;

[0115] It can be seen from Table 2 that the light decay of Examples 1 and 2 after aging at 120 mA for 168 h is smaller than that of Comparative Example 1, which proves that while the present invention improves the luminous efficiency, it can also reduce the aging light decay and improve the aging life.

[0116] Thus, by adjusting the number of periods, In composition, Al composition of the InGaN absorption layer and the AlGaN absorption layer in the composite electron blocking layer, and the thickness of the InGaN absorption layer and the AlGaN absorption layer; constructing a suitable overflow electron consumption layer, the problem of the decrease in hole injection efficiency caused by electron overflow is effectively reduced, and the photoelectric conversion efficiency at a high current density is effectively improved. At the same time, the introduction of the absorption layer can also achieve the light conversion effect of UVC, and the UVC photons that cannot escape due to reflection in the structure are annihilated in the structure and converted into heat, thereby reducing the overall heat generation of the structure, and finally providing higher optical power, less heat generation and higher aging life for the high-power light-emitting devices fabricated subsequently.

[0117] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A deep ultraviolet LED epitaxial structure, characterized in that, It includes a substrate, a buffer layer, an AlN intrinsic layer, a stress regulation layer, an electron injection layer, a current diffusion layer, a multi-quantum well active layer, a composite electron blocking layer, a hole injection layer, and a P-type contact layer which are stacked in sequence from bottom to top; The composite electron blocking layer includes a first AlGaN main structure layer, an absorption layer, and a second AlGaN main structure layer which are stacked in sequence from bottom to top; The first AlGaN main structure layer and the second AlGaN main structure layer are independently a single-layer AlGaN layer or a superlattice layer formed by alternately stacking; The absorption layer includes an InGaN absorption layer and an AlGaN absorption layer which are alternately stacked in sequence from bottom to top; the number of periods of the alternate stacking is 1 to 3; the atomic percentage content of In in the InGaN absorption layer is 1% to 10%; the atomic percentage content of Al in the AlGaN absorption layer is 45% to 75%.

2. The deep ultraviolet LED epitaxial structure according to claim 1, wherein, The atomic percentage content of Al in the first AlGaN main structure layer and the second AlGaN main structure layer is independently 45% to 75%.

3. The deep ultraviolet LED epitaxial structure according to claim 1, wherein The thickness of the first AlGaN main structure layer and the second AlGaN main structure layer is ≥5 nm.

4. The deep ultraviolet LED epitaxial structure according to claim 1, wherein The thickness of the InGaN absorption layer is 1 to 5 nm.

5. The deep ultraviolet LED epitaxial structure according to claim 1, characterized in that The thickness of the AlGaN absorption layer is 4 to 15 nm.

6. The deep ultraviolet LED epitaxial structure according to claim 5, wherein, The atomic percentage content of Al in the first AlGaN main structure layer and the second AlGaN main structure layer is greater than that of Al in the AlGaN absorption layer.

7. The method for preparing the deep ultraviolet LED epitaxial structure according to any one of claims 1 to 6, characterized in that, It includes the following steps: After growing a buffer layer, an AlN intrinsic layer, a stress regulation layer, an electron injection layer, a current diffusion layer, a multi-quantum well active layer, a composite electron blocking layer, a hole injection layer, and a P-type contact layer on the surface of the substrate in sequence, annealing treatment is carried out to obtain the deep ultraviolet LED epitaxial structure.

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