CN115148872A - Deep ultraviolet LED epitaxial structure and preparation method thereof - Google Patents
Deep ultraviolet LED epitaxial structure and preparation method thereof Download PDFInfo
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Abstract
The invention relates to the technical field of semiconductor structures, in particular to a deep ultraviolet LED epitaxial structure and a preparation method thereof. The invention provides a deep ultraviolet LED epitaxial structure which comprises 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, wherein the substrate, 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 composite electron blocking layer, the hole injection layer and the P-type contact layer are sequentially stacked from bottom to top; the composite electron blocking layer comprises a first AlGaN main body structure layer, an absorption layer and a second AlGaN main body structure layer which are sequentially stacked from bottom to top. The deep ultraviolet LED epitaxial structure has high photoelectric conversion efficiency and long aging life.
Description
Technical Field
The invention relates to the technical field of semiconductor structures, in particular to a deep ultraviolet LED epitaxial structure and a preparation method thereof.
Background
At present, group iii nitrides have been used as an outstanding representative of wide bandgap semiconductor materials, and have achieved high-efficiency solid-state light source devices such as blue-green Light Emitting Diodes (LEDs) and lasers, which have achieved great success in applications such as flat panel displays and white light illumination. In the last decade, it has been desired to apply such efficient luminescent materials in the ultraviolet band to meet the increasing demand of ultraviolet light sources. The ultraviolet band can be generally classified 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). Ultraviolet light, while not perceived by the human eye, is used in a wide variety of applications. The long-wave ultraviolet light source has great application prospect in the fields of medical treatment, ultraviolet curing, ultraviolet photoetching, information storage, plant illumination and the like; medium-wave ultraviolet and short-wave ultraviolet (collectively called deep ultraviolet) have irreplaceable effects in the aspects of sterilization, disinfection, water purification, biochemical detection, non-line-of-sight communication and the like. At present, the traditional ultraviolet light source is mainly a mercury lamp, has the defects of large volume, high power consumption, high voltage, environmental pollution and the like, and is not beneficial to the application of the traditional ultraviolet light source in daily life and special environments. Therefore, it is highly desirable to develop a highly efficient semiconductor ultraviolet light source device to replace the conventional mercury lamp. Research has shown that AlGaN, which is a group iii nitride, is the best candidate material for fabricating semiconductor uv light source devices. The AlGaN-based deep ultraviolet LED has the advantages of no toxicity, environmental protection, small size, portability, low power consumption, low voltage, easy integration, long service life, adjustable wavelength and the like, is expected to make breakthrough progress and wide application in the coming years, and gradually replaces the traditional ultraviolet mercury lamp.
At present, the biggest problems restricting the application of deep ultraviolet LEDs are that the photoelectric conversion efficiency is low (only 5% or less), and the device generates high heat. One of the main reasons for the low efficiency of the high Al component AlGaN-based deep ultraviolet LED is the existence of an obvious electron overflow effect, and electrons from an electron injection layer cross an electron blocking layer to a hole injection layer to cause non-radiative compound light of the hole injection layer, so that the internal quantum efficiency is reduced, and meanwhile, short-wave photon energy is high, and is easy to generate total reflection and cannot escape from the structure, and finally annihilate and convert into heat in the structure. The photoelectric conversion efficiency is low, the heat generation amount is high, and the photoelectric conversion efficiency and the aging life of the device are further influenced.
Disclosure of Invention
The invention aims to provide a deep ultraviolet LED epitaxial structure and a preparation method thereof.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a deep ultraviolet LED epitaxial structure, which comprises 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;
the composite electron blocking layer comprises a first AlGaN main body structure layer, an absorption layer and a second AlGaN main body structure layer which are sequentially stacked from bottom to top.
Preferably, the atomic percentage content of Al in the first AlGaN body structure layer and the second AlGaN body structure layer is 45% to 75% independently.
Preferably, the first AlGaN main structure layer and the second AlGaN main structure layer are independent single-layer AlGaN layers or superlattice layers stacked alternately.
Preferably, the thickness of the first AlGaN main structure layer and the thickness of the second AlGaN main structure layer are more than or equal to 5nm.
Preferably, the absorbing layer comprises InGaN absorbing layers and AlGaN absorbing layers which are alternately stacked from bottom to top in sequence.
Preferably, the number of cycles of the alternate stacking arrangement is 1 to 3.
Preferably, the thickness of the InGaN absorption layer is 1-5 nm;
the atomic percentage of In the InGaN absorption layer is 1% -10%.
Preferably, the thickness of the AlGaN absorption layer is 4 to 15nm;
the atomic percentage of Al in the AlGaN absorption layer is 45-75%.
Preferably, the atomic percentage content of Al in each of the first AlGaN body structure layer and the second AlGaN body structure layer is greater than the atomic percentage content of Al in the AlGaN absorption layer.
The invention also provides a preparation method of the deep ultraviolet LED epitaxial structure, which comprises the following steps:
and sequentially 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, and then annealing to obtain the deep ultraviolet LED epitaxial structure.
The invention provides a deep ultraviolet LED epitaxial structure, which comprises 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; the composite electron blocking layer comprises a first AlGaN main body structure layer, an absorption layer and a second AlGaN main body structure layer which are sequentially stacked from bottom to top. In the conventional structure, a larger energy band offset exists between the last potential barrier of the active region and the electron blocking layer, which is generally helpful to block electrons from overflowing the quantum well region, but at the same time, a larger polarization electric field also exists in the electron blocking layer, which lowers the effective barrier height for blocking electrons. The presence of a polarizing electric field between the last barrier and the electron blocking layer also causes the valence band energy level to bend significantly downward to form an effective barrier to holes, which directly results in lower hole injection efficiency. In order to effectively block overflow of electrons and improve injection efficiency of holes, the absorption layer is introduced into the composite electron blocking layer, so that a polarized electric field between the last barrier layer and the electron blocking layer can be reduced, and the influence on hole injection is reduced while the high-efficiency blocking of electrons is realized; meanwhile, the absorption layer has a good limiting effect on overflow electrons, so that the overflow electrons are combined with holes in the absorption layer to emit UVA photons, and the overflow electrons are prevented from flowing to the P-type injection layer to consume the holes or being captured by defects to form non-radiative recombination; the problem of hole injection efficiency reduction caused by electron overflow is effectively solved, and the photoelectric conversion efficiency under high current density is effectively improved. Meanwhile, the introduction of the absorption layer can play a role in UVC light conversion, UVC photons which cannot escape due to reflection in the structure are subjected to light conversion into UVA photons and escape out of the structure, the UVC photons which cannot escape in the structure are reduced, and the integral heat productivity of the structure is further reduced. And finally, higher optical power and less heat generation are provided for the high-power light-emitting device manufactured subsequently. Therefore, the deep ultraviolet LED epitaxial structure has high photoelectric conversion efficiency and long aging life.
Drawings
FIG. 1 is a schematic structural diagram of a deep ultraviolet LED epitaxial structure according to the present invention; the solar cell comprises a substrate 10, a buffer layer 11, an AlN intrinsic layer 12, a stress control layer 13, an electron injection layer 14, a current diffusion layer 15, a multiple quantum well active layer 16, a composite electron blocking layer 17, a hole injection layer 18, a P-type contact layer 19, an AlGaN main body structure layer 17a1, an absorption layer 17b, an InGaN absorption layer 17b1, an AlGaN absorption layer 17b2 and an AlGaN main body structure layer 17a 2;
FIG. 2 is a schematic view of a process for fabricating a deep ultraviolet LED epitaxial structure according to the present invention;
fig. 3 is a graph of luminance-current relationship of flip-chip chips prepared from the deep ultraviolet LED epitaxial structures described in example 1 and comparative example 1 (corresponding to the reference example in fig. 3);
fig. 4 is a spectrum diagram of a flip chip prepared by the deep ultraviolet LED epitaxial structure according to example 1 and comparative example 1 (corresponding to the reference example in fig. 4).
Detailed Description
The invention provides a deep ultraviolet LED epitaxial structure, which comprises 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;
the composite electron blocking layer comprises a first AlGaN main body structure layer, an absorption layer and a second AlGaN main body structure layer which are sequentially stacked from bottom to top.
In the invention, the material of the substrate is preferably one or more of sapphire, siC, gaN and Si, and more preferably sapphire.
The materials of the buffer layer, the AlN intrinsic layer, the stress control layer, the electron injection layer, the current diffusion layer, the multiple quantum well active layer, the hole injection layer and the P-type contact layer are not limited in any way, and nitride-based III-V group semiconductor materials (such as GaN, inN, alN, inGaN, alGaN or AlInGaN) well known to those skilled in the art can be adopted.
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 are not limited by any means and can be realized by adopting the thicknesses well known by the technical personnel in the field.
In the embodiment of the present invention, the material of the buffer layer is preferably Al x1 Ga 1-x1 N, wherein x1 is preferably 0.2 to 0.5, in particular 0.5; the thickness is specifically 20nm.
In an embodiment of the present invention, the AlN intrinsic layer is specifically AlN and has a thickness of 1500nm.
In the embodiment of the present invention, the stress control layer is specifically a superlattice layer (denoted as an AlN/AlGaN superlattice stress control layer) formed by alternately stacking AlN layers and AlGaN layers in sequence, the AlN layer is made of AlN, and the AlN layer has a thickness of 5nm; the AlGaN layer is made of Al x2 Ga 1-x2 N, wherein x2 is preferably 0.45-0.75, specifically 0.55, and the thickness of the AlGaN layer is 5nm; the number of cycles of the alternating stacking arrangement was 20. The total thickness of the stress control layer is 200nm.
In an embodiment of the present invention, the material of the electron injection layer is Al x3 Ga 1-x3 N, wherein x3 is preferably 0.45 to 0.75, in particular 0.55, the Al x3 Ga 1-x3 The concentration of Si doped in N is 5X 10 17 ～2×10 19 cm -3 Specifically 1X 10 19 cm -3 And the thickness of the electron injection layer is 2000nm.
In an embodiment of the present invention, the material of the current diffusion layer is Al x4 Ga 1-x4 N, wherein x4 is preferably 0.45 to 0.75, particularly 0.55, the above-mentioned Al x4 Ga 1-x4 The concentration of Si doped in N is 5X 10 17 ～5×10 18 cm -3 Specifically, 1X 10 18 cm -3 And the thickness of the electron injection layer is 200nm.
In an embodiment of the present invention, the multi-quantum well active layer includes AlGaN quantum barriers and AlInGaN quantum wells alternately grown in a stack; the number of the periods of the alternate stacking arrangement is preferably 3-12, specifically 5; the AlGaN quantum barrier is made of Al x5 Ga 1-x5 N, wherein x5 is preferably 0.45-0.65, specifically 0.58, and the thickness is 10nm; the AlInGaN quantum well is made of Al x6 In y6 Ga 1-x6-y6 N, where x6 is preferably from 0.4 to 0.5, in particular 0.45, y is preferably from 0.005 to 0.02, in particular 0.005, and the thickness is 2nm.
In the 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, in particular 0.65; the Al is x7 Ga 1-x7 The doping concentration of Mg in N is preferably 2X 10 19 ～2×10 20 cm -3 Specifically 1X 10 20 cm -3 (ii) a The thickness was 20nm.
In the embodiment of the invention, the material of the P-type contact layer is GaN, and the doping concentration of Mg in the GaN>5×10 20 cm -3 Specifically 8X 10 20 cm -3 (ii) a The thickness was 10nm.
In the present invention, the atomic percentage content of Al in the first AlGaN body structure layer and the second AlGaN body structure layer is preferably 45% to 75%, more preferably 50% to 70%, and most preferably 60% to 70%, independently.
In the invention, the thickness of the first AlGaN main structure layer and the thickness of the second AlGaN main structure layer are preferably more than or equal to 5nm. In the invention, the first AlGaN body structure layer and the second AlGaN body structure layer are independent and preferably single-layer AlGaN layers or superlattice layers which are alternatively stacked; when the first AlGaN main structure layer or the second AlGaN main structure layer is preferably a superlattice layer alternately stacked, the superlattice layer preferably includes Al sequentially alternately stacked x8 Ga 1-x8 N layer and Al x9 Ga 1-x9 N layers; wherein xThe value range of 8 is preferably 0.45-0.6, and the value range of x9 is preferably 0.6-0.70; the Al is x8 Ga 1-x8 The thickness of the N layer is preferably 1 to 5nm, more preferably 2 to 4nm, and most preferably 3nm; the Al is x9 Ga 1-x9 The thickness of the N layer is preferably 1 to 5nm, more preferably 2 to 4nm, and most preferably 3nm. In the present invention, the number of cycles of the alternate stacking arrangement is preferably 10. When the first AlGaN body structure layer or the second AlGaN body structure layer is preferably a single-layer AlGaN layer, the material of the single-layer AlGaN layer is preferably Al x10 Ga 1-x10 And N, wherein the value range of x10 is preferably 0.45-0.75, more preferably 0.50-0.70, and most preferably 0.7. The thickness of the single AlGaN layer is preferably 5to 50nm, more preferably 5to 30nm, and most preferably 20nm. In a specific embodiment of the present invention, the first AlGaN body structure layer and the second AlGaN body structure layer are Al with a thickness of 20nm 0.70 Ga 0.30 N。
In the present invention, the absorption layer preferably includes an InGaN absorption layer and an AlGaN absorption layer alternately stacked in sequence from bottom to top. In the present invention, the number of cycles of the alternate stacking is preferably 1 to 3, and more preferably 2. In the present invention, the thickness of the InGaN absorption layer is preferably 1 to 5nm, more preferably 2 to 4nm, and most preferably 3nm; the thickness of the AlGaN absorption layer is preferably 4 to 15nm, more preferably 6 to 12nm, and most preferably 8 to 10nm; the atomic percentage of Al in the AlGaN absorption layer is preferably 45% to 75%, more preferably 50% to 70%, and most preferably 55% to 60%.
In the present invention, the atomic percentage content of Al in each of the first AlGaN body structure layer and the second AlGaN body structure layer is preferably greater than the atomic percentage content of Al in the AlGaN absorption layer.
The invention also provides a preparation method of the deep ultraviolet LED epitaxial structure, which comprises the following steps:
and sequentially 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, and then annealing to obtain the deep ultraviolet LED epitaxial structure.
In the present invention, the preparation method is preferably performed in MOCVD.
In the present invention, the growth of the buffer layer is preferably performed under the conditions of 75to 200torr and 500 to 900 ℃.
In the present invention, the growth of the AlN intrinsic layer is preferably performed under the conditions of 75to 200torr and 1000 to 1400 ℃.
In the present invention, the growth of the stress control layer is preferably performed under the conditions of 75to 200torr and 1000 to 1400 ℃.
In the present invention, the growth of the electron injection layer is preferably performed under the conditions of 75to 200torr and 1000 to 1350 ℃, while doping with a Si source provides N-type electrons.
In the present invention, the growth of the current diffusion layer is preferably performed under the conditions of 75to 200torr and 900 to 1250 ℃.
In the present invention, the growth of the multiple quantum well active layer is preferably performed under the conditions of 75to 200torr and 900 to 1250 ℃.
In the invention, the growth of the first AlGaN main structure layer and the growth of the second AlGaN main structure layer in the composite electron blocking layer are both preferably carried out under the conditions of 75-200 torr and 1000-1400 ℃.
In the present invention, the growth of the absorption layer is preferably performed under the conditions of 75to 200torr and 750 to 1100 ℃.
In the present invention, the growth of the hole injection layer is preferably performed under the conditions of 75to 200torr and 900 to 1250 ℃ while introducing a Mg source.
In the present invention, the growth of the P-type contact layer is preferably performed under the conditions of 75to 200torr and 700 to 1000 ℃ while introducing a Mg source.
In the present invention, the annealing treatment is preferably performed under a nitrogen atmosphere at 75to 200torr and 600 to 1000 ℃; the time of the annealing treatment is preferably 5to 30min.
The deep ultraviolet LED epitaxial structure and the preparation method thereof provided by the present invention are described in detail below with reference to the following examples, but they should not be construed as limiting the scope of the present invention.
Example 1
Placing a sapphire substrate in MOCVD, and growing a buffer layer (the material of the buffer layer is Al) with the thickness of 20nm on the C surface of the sapphire substrate under the conditions of 75torr and 900 DEG C 0.5 Ga 0.5 N)；
Growing an AlN intrinsic layer with the thickness of 1500nm on the surface of the buffer layer under the conditions of 100torr and 1300 ℃;
growing an AlN/AlGaN superlattice stress control layer with the total thickness of 120nm on the surface of the AlN intrinsic layer under the conditions of 100torr and 1300 ℃ (the stress control layer comprises AlN layers and AlGaN layers which are alternately laminated in sequence, the AlN layers are 5nm thick and are made of AlN, the AlGaN layers are 5nm thick and are made of Al 0.55 Ga 0.45 N, the number of the periods of the alternate stacking arrangement is 20);
growing a Si-doped AlGaN electron injection layer with the thickness of 2000nm on the surface of the stress control layer of the AlN/AlGaN superlattice under the conditions of 100torr and 1300 ℃ (the material of the AlGaN electron injection layer is Al 0.55 Ga 0.45 The doping concentration of N and Si is 1X 10 19 cm -3 )；
Growing an AlGaN current diffusion layer with the thickness of 200nm on the surface of the Si-doped AlGaN electron injection layer under the conditions of 100torr and 1200 ℃ (the material of the AlGaN current diffusion layer is Al) 0.55 Ga 0.45 The doping concentration of N and Si is 1X 10 18 cm -3 )；
Under the condition of 100torr and 980 ℃, sequentially and alternately laminating and growing a multi-quantum well active layer of an AlGaN quantum barrier/AlInGaN quantum well on the surface of the AlGaN current diffusion layer (the number of alternately laminated cycles is 5, the atomic percentage content of Al in the AlGaN quantum barrier is 58%, the atomic percentage content of Al in the AlInGaN quantum well is 45%, and the thickness is 2 nm);
growing a first AlGaN main body structure layer (the material of the first AlGaN main body structure layer) with the thickness of 20nm and the Al content of 70% on the surface of the multiple quantum well active layer under the conditions of 100torr and 1300 DEG CThe material is Al 0.7 Ga 0.3 N)；
Under the conditions of 100torr and 980 ℃, growing an InGaN layer with the thickness of 2nm and the In doping amount of 5% and an AlGaN layer with the thickness of 8nm and the Al doping amount of 55% on the surface of the first AlGaN main structure layer In sequence to obtain an absorption layer;
growing a second AlGaN main body structure layer with the thickness of 20nm and the Al content of 70% on the surface of the absorption layer under the conditions of 100torr and 1300 ℃ (the material of the second AlGaN main body structure layer is Al 0.7 Ga 0.3 N), obtaining a composite electron blocking layer;
introducing Mg source at 1200 ℃ at 100torr, and growing an AlGaN hole injection layer with the thickness of 20nm on the surface of the composite electron blocking layer (the AlGaN hole injection layer is made of Al 0.65 Ga 0.35 N, mg atom percentage of 1X 10 20 cm -3 )；
Introducing Mg source at 880 deg.C at 100torr, and growing a 10nm thick P-type GaN contact layer (Mg atom percentage of 8 × 10) 20 cm -3 )；
At 200torr, 700 ℃ and N 2 And annealing for 20min under the atmosphere condition to obtain the deep ultraviolet LED epitaxial structure.
Comparative example 1
Referring to example 1, there is a difference that an AlGaN structure layer (the material of the AlGaN main structure layer is Al) having a thickness of 40nm and an Al doping amount of 70% is grown on the surface of the multiple quantum well active layer at 100torr and 1300 ℃ 0.7 Ga 0.3 N), obtaining the electron blocking layer.
Test example 1
Manufacturing the deep ultraviolet LED epitaxial structures described in the embodiment 1 and the comparative example 1 into a 20mil-20mil flip chip, and comparing the optical power conditions under the driving current of 1-400 mA;
fig. 3 is a luminance-current relationship diagram of flip chip chips prepared by the deep ultraviolet LED epitaxial structures described in example 1 and comparative example 1 (corresponding to the reference example in fig. 3), and it can be seen from fig. 3 that the deep ultraviolet LED epitaxial structure described in example 1 has significantly higher optical power than comparative example 1 under the driving of a large current, and the current density at the luminance inflection point is also larger. The problem that the hole injection efficiency is reduced due to electron overflow can be effectively solved along with pouring of the absorption layer in the composite electron blocking layer in the deep ultraviolet LED epitaxial structure in the embodiment 1, and the photoelectric conversion efficiency under high current density is effectively improved;
fig. 4 is a spectrum diagram of a flip chip prepared by the deep ultraviolet LED epitaxial structure according to example 1 and comparative example 1 (corresponding to the reference example in fig. 4); as can be seen from fig. 4, in embodiment 1, the light conversion efficiency of the UVC can be achieved due to the pouring of the absorption layer, the UVC photons which cannot escape due to reflection in the structure are subjected to light conversion into UVA photons and escape out of the structure, and the phenomenon that the UVC photons which cannot escape are annihilated in the structure and then converted into heat is reduced, so that the overall heat productivity of the structure is reduced, the reduction of the heat productivity effectively improves the performance of the device, and finally, not only is the light output power of the UVA section increased, but also the light power of the UVC band is not reduced and increased.
Example 2
Referring to example 1, except for the preparation process of the composite electron blocking layer:
growing a first AlGaN body structure layer with the thickness of 20nm and the Al doping amount of 70% on the surface of the multiple quantum well active layer under the conditions of 100torr and 1300 ℃ 0.7 Ga 0.3 N)；
Under the conditions of 100torr and 980 ℃, sequentially growing 2 periods of InGaN layers with the thickness of 2nm and the doping amount of In of 5% and AlGaN layers with the thickness of 8nm and the doping amount of Al of 55% on the surface of the first AlGaN main body structure layer to obtain an absorption layer;
growing a second AlGaN main body structure layer with the thickness of 20nm and the Al content of 70% on the surface of the absorption layer under the conditions of 100torr and 1300 ℃ (the material of the second AlGaN main body structure layer is Al 0.7 Ga 0.3 N) to obtain the composite electron blocking layer.
Example 3
Referring to example 1, except for the preparation process of the composite electron blocking layer:
growing a first AlGaN main body structure layer with the thickness of 20nm and the Al content of 70% on the surface of the multiple quantum well active layer under the conditions of 100torr and 1300 ℃ (the material of the first AlGaN main body structure layer is Al 0.7 Ga 0.3 N)；
Under the condition of 100torr and 980 ℃, growing an InGaN layer with the thickness of 2nm and the In doping amount of 2% and an AlGaN layer with the thickness of 8nm and the Al doping amount of 55% on the surface of the first AlGaN main body structure layer In sequence to obtain an absorption layer;
growing a second AlGaN main body structure layer with the thickness of 20nm and the Al content of 70% on the surface of the absorption layer under the conditions of 100torr and 1300 ℃ (the material of the second AlGaN main body structure layer is Al 0.7 Ga 0.3 N) to obtain the composite electron blocking layer.
Example 4
Referring to example 1, except for the preparation process of the composite electron blocking layer:
under the conditions of 100torr and 1300 ℃, a first AlGaN main body structure layer with the thickness of 30nm and the Al content of 70% is grown on the surface of the multiple quantum well active layer (the material of the first AlGaN main body structure layer is Al) 0.7 Ga 0.3 N)；
Under the condition of 100torr and 980 ℃, growing an InGaN layer with the thickness of 2nm and the In doping amount of 5% and an AlGaN layer with the thickness of 8nm and the Al doping amount of 55% on the surface of the first AlGaN main body structure layer In sequence to obtain an absorption layer;
under the conditions of 100torr and 1300 ℃, a second AlGaN main body structure layer with the thickness of 10nm and the Al content of 70% is grown on the surface of the absorption layer (the material of the second AlGaN main body structure layer is Al 0.7 Ga 0.3 N) to obtain the composite electron blocking layer.
Example 5
Referring to example 1, except for the preparation process of the composite electron blocking layer:
under the conditions of 100torr and 1300 ℃, a first AlGaN main body structure layer (the first AlGaN main body junction) with the thickness of 20nm and the Al content of 70% is grown on the surface of the multiple quantum well active layerThe material of the layer is Al 0.7 Ga 0.3 N)；
Under the condition of 100torr and 980 ℃, growing an InGaN layer with the thickness of 3nm and the In doping amount of 5% and an AlGaN layer with the thickness of 8nm and the Al doping amount of 55% on the surface of the first AlGaN main body structure layer In sequence to obtain an absorption layer;
growing a second AlGaN main body structure layer with the thickness of 20nm and the Al content of 70% on the surface of the absorption layer under the conditions of 100torr and 1300 ℃ (the material of the second AlGaN main body structure layer is Al 0.7 Ga 0.3 N) to obtain the composite electron blocking layer.
Example 6
Referring to example 1, except for the preparation process of the composite electron blocking layer:
growing a first AlGaN main body structure layer with the thickness of 20nm and the Al content of 70% on the surface of the multiple quantum well active layer under the conditions of 100torr and 1300 ℃ (the material of the first AlGaN main body structure layer is Al 0.7 Ga 0.3 N)；
Under the conditions of 100torr and 980 ℃, growing an InGaN layer with the thickness of 2nm and the In doping amount of 5% and an AlGaN layer with the thickness of 12nm and the Al doping amount of 55% on the surface of the first AlGaN main structure layer In sequence to obtain an absorption layer;
growing a second AlGaN main body structure layer with the thickness of 20nm and the Al content of 70% on the surface of the absorption layer under the conditions of 100torr and 1300 ℃ (the material of the second AlGaN main body structure layer is Al 0.7 Ga 0.3 N) to obtain the composite electron blocking layer.
Test example 2
The deep ultraviolet LED epitaxial structures described in examples 1 to 6 and comparative example 1 were fabricated into a 20mil-20mil flip chip, and tested at a driving current of 100 mA;
the test results are shown in table 1:
table 1 performance parameters of flip chip having a deep ultraviolet LED epitaxial structure according to examples 1 to 6 and comparative example 1
As can be seen from table 1, the variation of parameters in the composite electron blocking layer can effectively optimize the key parameters for reducing electron overflow and converting UVC into UVA wavelength.
Test example 3
The deep ultraviolet LED epitaxial structures described in examples 1-2 and comparative example 1 were fabricated into 20mil-20mil flip-chip structures and aged for 168 hours at 120mA current; carrying out aging performance test under the drive current of 100 mA;
the test results are shown in table 2:
table 2 aging parameters of flip chip having a deep ultraviolet LED epitaxial structure according to examples 1 to 2 and comparative example 1
Note: in Table 2, U (V) is the forward voltage measured at a forward current of 100 mA; IR (muA) is reverse leakage current tested under 8V reverse voltage, phi e (mW) is light intensity tested under 100mA forward current, and WP (nm) is peak wavelength tested under 100mA forward current;
as can be seen from Table 2, the light attenuation of the embodiment 1 and the embodiment 2 after aging for 168 hours at 120mA is smaller than that of the comparative example 1, which proves that the invention can reduce the aging light attenuation and prolong the aging life while improving the luminous efficiency.
Therefore, the cycle number, the In component and the Al component of the InGaN absorption layer and the AlGaN absorption layer of the absorption layer In the composite electron barrier layer and the thicknesses of the InGaN absorption layer and the AlGaN absorption layer are adjusted; and a proper overflow electron consumption layer is constructed, so that the problem of hole injection efficiency reduction caused by electron overflow is effectively solved, and the photoelectric conversion efficiency under high current density is effectively improved. Meanwhile, the absorption layer can play a role in light conversion of UVC, and UVC photons which cannot escape due to reflection in the structure are annihilated in the structure and then converted into heat, so that the overall heat productivity of the structure is reduced, and higher optical power, less heat productivity and higher aging life are finally provided for a subsequently manufactured high-power light-emitting device.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A deep ultraviolet LED epitaxial structure is characterized by comprising 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;
the composite electron blocking layer comprises a first AlGaN main body structure layer, an absorption layer and a second AlGaN main body structure layer which are sequentially stacked from bottom to top.
2. The deep ultraviolet LED epitaxial structure of claim 1, wherein the atomic percent of Al in the first AlGaN bulk structure layer and the second AlGaN bulk structure layer are independently 45% to 75%.
3. The deep ultraviolet LED epitaxial structure of claim 1 or 2, wherein the first AlGaN main structure layer and the second AlGaN main structure layer are independently a single AlGaN layer or a super lattice layer alternately stacked.
4. The deep ultraviolet LED epitaxial structure of claim 3, wherein the thickness of the first AlGaN body structure layer and the second AlGaN body structure layer is not less than 5nm.
5. The deep ultraviolet LED epitaxial structure of claim 1, wherein the absorber layer comprises InGaN absorber layers and AlGaN absorber layers stacked alternately in sequence from bottom to top.
6. The deep ultraviolet LED epitaxial structure of claim 5, wherein the alternating stack arrangement has a number of cycles in the range of 1 to 3.
7. The deep ultraviolet LED epitaxial structure of claim 6, wherein the InGaN absorbing layer has a thickness of 1 to 5nm;
the atomic percentage of In the InGaN absorption layer is 1% -10%.
8. The deep ultraviolet LED epitaxial structure of claim 6, wherein the AlGaN absorption layer has a thickness of 4 to 15nm;
the atomic percentage of Al in the AlGaN absorption layer is 45-75%.
9. The deep ultraviolet LED epitaxial structure of claim 8, wherein the atomic percentage of Al in each of the first and second AlGaN bulk structure layers is greater than the atomic percentage of Al in the AlGaN absorption layer.
10. A method of fabricating a deep ultraviolet LED epitaxial structure according to any one of claims 1 to 9, comprising the steps of:
and sequentially 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, and then annealing to obtain the deep ultraviolet LED epitaxial structure.
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