CN115863503A - Deep ultraviolet LED epitaxial wafer, preparation method thereof and deep ultraviolet LED - Google Patents
Deep ultraviolet LED epitaxial wafer, preparation method thereof and deep ultraviolet LED Download PDFInfo
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Abstract
The invention discloses a deep ultraviolet LED epitaxial wafer, a preparation method thereof and a deep ultraviolet LED, wherein the deep ultraviolet LED epitaxial wafer comprises a substrate, and a buffer layer, a non-doped AlGaN layer, an N-type AlGaN layer, a multi-quantum well layer, an electron barrier layer, a P-type AlGaN layer and a P-type contact layer which are sequentially stacked on the substrate; the P-type contact layer comprises Mg doped B which is sequentially laminated on the P-type AlGaN layer a Al b Ga 1‑a‑b N layer, B x Al y Ga 1‑x‑y Nanocluster layer/Mg doped B x Al y Ga 1‑x‑y And N superlattice layers. The deep ultraviolet LED epitaxial wafer provided by the invention can improve the light extraction efficiency of the deep ultraviolet LED epitaxial wafer.
Description
Technical Field
The invention relates to the technical field of photoelectricity, in particular to a deep ultraviolet LED epitaxial wafer, a preparation method of the deep ultraviolet LED epitaxial wafer and a deep ultraviolet LED.
Background
The LED light-emitting wavelength is determined by the basic band gap of the active region materials of the device, and the LED made of the III-nitride material covers the whole ultraviolet UV-A, UV-B and UV-C regions which are close to 200nm (corresponding to the band gap width of AlN) to 400 nm (corresponding to the band gap width of InGaN). The deep ultraviolet solid light source is widely applied to the fields of sterilization, water quality purification, biochemistry and medicine, high-density optical storage light sources, white light illumination, fluorescence analysis systems and related information sensing fields, air purification equipment, zero-emission automobiles and the like.
The activation energy of the Mg acceptor of the deep ultraviolet LED epitaxial wafer is linearly increased along with the increase of Al component, so that the activation efficiency of Mg is low, and the low hole concentration makes it difficult to form P-type ohmic contact. In order to improve the P-type ohmic contact, a P-type GaN contact layer can be added, but ultraviolet light can be absorbed by the P-type GaN contact layer, the P-type GaN can generate strong ultraviolet absorption, and the absorption factor of the contact layer is increased along with the reduction of the peak wavelength even if the contact layer is thin.
Therefore, in the prior art, for the deep ultraviolet LED epitaxial wafer, in order to form a good ohmic contact, a commonly used method is heavy doping of Mg, but the Mg doping concentration is too high, so that the crystal quality of the P-type AlGaN layer is poor, and meanwhile, the narrow forbidden band width of Mg increases the absorption of light, and reduces the external quantum efficiency of the deep ultraviolet LED epitaxial wafer. However, a good ohmic contact cannot be formed when the doping concentration is low, so that the working voltage of the deep ultraviolet LED epitaxial wafer is increased, and the aging performance of the deep ultraviolet LED epitaxial wafer is affected.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a deep ultraviolet LED epitaxial wafer, which can increase the activation concentration of Mg, improve the current spreading capability, reduce the contact resistance, increase the light extraction efficiency, and increase the photoelectric conversion efficiency of the deep ultraviolet LED epitaxial wafer.
The technical problem to be solved by the invention is to provide a preparation method of the deep ultraviolet LED epitaxial wafer, which is simple in process and can stably prepare the deep ultraviolet LED epitaxial wafer with good performance.
In order to solve the technical problem, the invention provides a deep ultraviolet LED epitaxial wafer, which comprises a substrate, and a buffer layer, a non-doped AlGaN layer, an N-type AlGaN layer, a multi-quantum well layer, an electron barrier layer, a P-type AlGaN layer and a P-type contact layer which are sequentially stacked on the substrate;
the P-type contact layer comprises Mg doped B which is sequentially laminated on the P-type AlGaN layer a Al b Ga 1-a-b N layer, B x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y N superlattice layers, wherein a is more than 0 and less than 0.45, b is more than 0 and less than 0.45, x is more than 0 and less than 0.45, and y is more than 0 and less than 0.45.
In one embodiment, the Mg is doped with B a Al b Ga 1-a-b In the N layer, the B component gradually rises from the position close to the P-type AlGaN layer to the position far away from the P-type AlGaN layer;
the Al component is gradually reduced from the position close to the P-type AlGaN layer to the position far away from the P-type AlGaN layer.
In one embodiment, B is x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y N superlattice layers consisting of B x Al y Ga 1-x-y Nanocluster layer and Mg doped B x Al y Ga 1-x-y The N layers are sequentially and alternately laminated, and the repetition period is more than or equal to 1.
In one embodiment, the Mg is doped with B a Al b Ga 1-a-b The thickness of the N layer is 1nm-10nm;
b is x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y The thickness of the N superlattice layers is 1nm-10nm;
b is x Al y Ga 1-x-y Nanocluster layer and said Mg doped B x Al y Ga 1-x-y The thickness ratio of the N layer is 1: (1-5).
In one embodiment, the Mg is doped with B a Al b Ga 1-a-b N layer of MgThe doping concentration is 1 x 10 19 atoms/cm 3 -1×10 20 atoms/cm 3 ；
The Mg is doped with B x Al y Ga 1-x-y The Mg doping concentration of the N layer is 1 x 10 20 atoms/cm 3 -1×10 21 atoms/cm 3 。
In order to solve the above problems, the present invention further provides a method for preparing the deep ultraviolet LED epitaxial wafer, including the following steps:
s1, preparing a substrate;
s2, sequentially depositing a buffer layer, a non-doped AlGaN layer, an N-type AlGaN layer, a multi-quantum well layer, an electron barrier layer, a P-type AlGaN layer and a P-type contact layer on the substrate;
the P-type contact layer comprises Mg doped B which is sequentially laminated on the P-type AlGaN layer a Al b Ga 1-a-b N layer, B x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y N superlattice layers, wherein a is more than 0 and less than 0.45, b is more than 0 and less than 0.45, x is more than 0 and less than 0.45, and y is more than 0 and less than 0.45.
In one embodiment, the Mg is doped with B a Al b Ga 1-a-b The N layer is prepared by the following method:
introducing a nitrogen source, a boron source, an aluminum source, a gallium source and a magnesium source into the reaction chamber, taking hydrogen and nitrogen as growth atmosphere, and depositing Mg doped B on the P-type AlGaN layer a Al b Ga 1-a-b And N layers.
In one embodiment, B is x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y The N superlattice layers are prepared by the following steps:
introducing a nitrogen source, a boron source, an aluminum source and a gallium source into the reaction chamber, and taking hydrogen, nitrogen and ammonia as growth atmosphere to finish the step B x Al y Ga 1-x-y Deposition of a layer of nanoclusters;
introducing a nitrogen source, a boron source, an aluminum source, a gallium source and a magnesium source into the reaction chamber, and taking hydrogen, nitrogen and ammonia as a growth atmosphere to finish the Mg doping B x Al y Ga 1-x-y Depositing an N layer;
alternately depositing the B x Al y Ga 1-x-y Nanocluster layer and Mg doped B x Al y Ga 1-x-y N layers of the said B x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y And N superlattice layers.
In one embodiment, B is x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y In the deposition process of the N superlattice layers, the temperature in the reaction chamber is 900-1100 ℃;
the pressure in the reaction chamber is 100-300 torr;
in the growth atmosphere, hydrogen: nitrogen gas: ammonia gas =1: (5-10): (1-5).
Correspondingly, the invention further provides the deep ultraviolet LED, and the deep ultraviolet LED comprises the deep ultraviolet LED epitaxial wafer.
The implementation of the invention has the following beneficial effects:
the P-type contact layer of the deep ultraviolet LED epitaxial wafer comprises Mg doped B which is sequentially laminated on the P-type AlGaN layer a Al b Ga 1-a-b N layer, B x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y And N superlattice layers. The Mg is doped with B a Al b Ga 1-a-b The N layer can reduce the activation energy of Mg and improve the concentration of activated Mg, and the wide forbidden band widths of B and N can reduce the absorption of the P-type contact layer to deep ultraviolet light and reduce the deposition of B on the back x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y The lattice mismatch of the N superlattice layers improves the crystal quality. B is x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y N superlattice layers with B x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y The N-layer superlattice structure is used as a current expansion bridging point to solve the problemThe problems of low hole concentration and current expansion deviation of a P type due to low Mg ionization efficiency are solved, the diffusion length of a P type contact layer hole is increased, the expansion capability of a P type current is improved, the accumulation effect of the current is reduced, the ohmic contact between an epitaxial layer and an electrode is improved, the working voltage of a deep ultraviolet LED epitaxial wafer is reduced, and the luminous efficiency of the deep ultraviolet LED epitaxial wafer is improved.
Drawings
Fig. 1 is a schematic structural diagram of a deep ultraviolet LED epitaxial wafer provided by the present invention.
Wherein: the solar cell comprises a substrate 1, a buffer layer 2, a non-doped AlGaN layer 3, an N-type AlGaN layer 4, a multi-quantum well layer 5, an electron barrier layer 6, a P-type AlGaN layer 7, a P-type contact layer 8 and Mg-doped B a Al b Ga 1-a-b N layer 81 and B x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y N layers of superlattice layer 82.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below.
Unless otherwise stated or contradicted, terms or phrases used herein have the following meanings:
in the present invention, "preferred" is only an embodiment or an example for better description, and it should be understood that the scope of the present invention is not limited thereto.
In the present invention, the technical features described in the open type include a closed technical solution composed of the listed features, and also include an open technical solution including the listed features.
In the present invention, the numerical range is defined to include both end points of the numerical range unless otherwise specified.
In order to solve the above problems, the present invention provides a deep ultraviolet LED epitaxial wafer, as shown in fig. 1, including a substrate 1, and a buffer layer 2, a non-doped AlGaN layer 3, an N-type AlGaN layer 4, a multiple quantum well layer 5, an electron blocking layer 6, a P-type AlGaN layer 7, and a P-type contact layer 8 sequentially stacked on the substrate 1;
the P-type contact layer 8 comprises a layer stacked in sequenceMg doped B on the P-type AlGaN layer 7 a Al b Ga 1-a-b N layer 81, B x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y N superlattice layers 82, wherein a is more than 0 and less than 0.45, b is more than 0 and less than 0.45, x is more than 0 and less than 0.45, and y is more than 0 and less than 0.45.
The P-type contact layer 8 of the deep ultraviolet LED epitaxial wafer comprises Mg doped B which is sequentially laminated on the P-type AlGaN layer 7 a Al b Ga 1-a-b N layer 81, B x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y N layers of superlattice layer 82. The Mg is doped with B a Al b Ga 1-a-b The N layer 81 can reduce the activation energy of Mg and improve the concentration of activated Mg, and the forbidden band widths of B and N are wider, so that the absorption of the P-type contact layer 8 on deep ultraviolet light can be reduced, and the B deposition and the subsequent B deposition can be reduced x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y The lattice mismatch in the case of the N superlattice layers 82 improves the crystal quality. B is described x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y The N-layer superlattice layer 82 serves as a current expansion bridge point, the problems that the hole concentration is low and the current expansion deviation is caused due to low Mg ionization efficiency of a P type are solved, the diffusion length of a hole of a P type contact layer is increased, the expansion capability of a P type current is improved, the current accumulation effect is reduced, ohmic contact between an epitaxial layer and an electrode is improved, the working voltage of a deep ultraviolet LED epitaxial wafer is reduced, and the luminous efficiency of the deep ultraviolet LED epitaxial wafer is improved.
In one embodiment, the Mg is doped with B a Al b Ga 1-a-b In the N layer 81, the B component gradually increases from the position near the P-type AlGaN layer 7 to the position far from the P-type AlGaN layer 7; the Al composition gradually decreases from the position close to the P-type AlGaN layer 7 to the position far away from the P-type AlGaN layer 7. Preferably, said Mg is doped with B a Al b Ga 1-a-b In the N layer 81, the B composition is increased from 0.1 to 0.4 from the position close to the P type AlGaN layer 7 to the position far away from the P type AlGaN layer 7, and the Al composition is increased from the position close to the P type AlGaN layer 7The N layer 7 is reduced from 0.45 to 0.2 in the direction away from the P-type AlGaN layer 7.
It should be noted that the activation energy of Mg gradually decreases with the increase of Al component, so that when the doping of Al component of the deep ultraviolet P-type contact layer is higher, the concentration of activated Mg is lower, and the current spreading is worse. The B component and the Al component are distributed according to the rule, so that the activation energy of Mg can be reduced, the concentration of activated Mg is improved, the forbidden bands of B and N are wide, the absorption of a P-type contact layer to deep ultraviolet light can be reduced, and the deposition of B on the P-type contact layer and the subsequent deposition of B can be reduced x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y The lattice mismatch of the N superlattice layers improves the crystal quality.
In one embodiment, B is x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y N superlattice layers 82 of B x Al y Ga 1-x-y Nanocluster layer and Mg doped B x Al y Ga 1-x-y The N layers are sequentially and alternately laminated, the repetition period is more than or equal to 1, namely the number of superlattice periods is more than or equal to 1. Wherein, B x Al y Ga 1-x-y The nanocluster layer is not doped with Mg, so that the absorption of deep ultraviolet light is reduced, the structure of the nanocluster layer increases light reflection, the light emitting efficiency of the deep ultraviolet light is improved, and the Mg is doped with B x Al y Ga 1-x-y The N layer can provide better ohmic contact due to higher activated Mg concentration, and the contact resistance of the deep ultraviolet LED epitaxial wafer is reduced. Preferably, B is x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y In the N superlattice layer 82, x is more than 0.1 and less than 0.45, and y is more than 0.1 and less than 0.3; more preferably, x is 0.4 and y is 0.2.
Further, mg is doped with B a Al b Ga 1-a-b N layer 81 and B x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y The appropriate thickness of the N-layer superlattice layer 82 and the appropriate number of superlattice periods may reduce the thickness of the P-type contact layer and reduce absorption of deep ultraviolet light. In one embodiment, the Mg is doped with B a Al b Ga 1-a-b The thickness of the N layer 81 is 1nm to 10nm; b is described x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y The thickness of the N superlattice layers 82 is 1nm-10nm; b is x Al y Ga 1-x-y Thickness of the nanocluster layer: the Mg is doped with B x Al y Ga 1-x-y Thickness of N layer =1: (1-5). Preferably, said Mg is doped with B a Al b Ga 1-a-b The thickness of the N layer 81 is 7nm; b is x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y The thickness of the N superlattice layers 82 is 6nm; b is x Al y Ga 1-x-y Thickness of nanocluster layer: the Mg is doped with B x Al y Ga 1-x-y Thickness of N layer =1:2.
in addition, the Mg doping concentration in a proper range is beneficial to current expansion, the current expansion is poor when the Mg doping concentration is too low, the contact resistance is increased rapidly, and the Mg complex is caused by too high doping concentration, so that the activated Mg concentration is reduced. In one embodiment, the Mg is doped with B a Al b Ga 1-a-b The Mg doping concentration of the N layer 81 is 1X 10 19 atoms/cm 3 -1×10 20 atoms/cm 3 (ii) a The Mg is doped with B x Al y Ga 1-x-y The Mg doping concentration of the N layer is 1 x 10 20 atoms/cm 3 -1×10 21 atoms/cm 3 . Preferably, said Mg is doped with B a Al b Ga 1-a-b The Mg doping concentration of the N layer 81 was 7X 10 19 atoms/cm 3 -8×10 19 atoms/cm 3 (ii) a The Mg is doped with B x Al y Ga 1-x-y The Mg doping concentration of the N layer is 3 multiplied by 10 20 atoms/cm 3 -4×10 20 atoms/cm 3 。
In order to solve the above problems, the present invention further provides a method for preparing the deep ultraviolet LED epitaxial wafer, including the following steps:
s1, preparing a substrate 1;
in one embodiment, the substrate can be selected from (0001) plane sapphire substrate, alN substrate, si (111) substrate, siC (0001) substrate, etc. Preferably, the substrate is a sapphire substrate, sapphire is the most common substrate material at present, and the sapphire substrate has the advantages of mature preparation process, low price, easiness in cleaning and treatment and good stability at high temperature.
S2, sequentially depositing a buffer layer 2, a non-doped AlGaN layer 3, an N-type AlGaN layer 4, a multi-quantum well layer 5, an electron barrier layer 6, a P-type AlGaN layer 7 and a P-type contact layer 8 on the substrate 1.
In one embodiment, said S2 comprises the steps of:
s21, depositing an AlN buffer layer 2 on the substrate 1, wherein the thickness is 20nm-200nm.
Preferably, an AlN buffer layer is deposited in PVD to a thickness of 100 nm. The AlN buffer layer is adopted to provide a nucleation center with the same orientation as the substrate, the stress generated by lattice mismatch between AlGaN and the substrate and the thermal stress generated by thermal expansion coefficient mismatch are released, a smooth nucleation surface is provided for further growth, the contact angle of nucleation growth is reduced, island-shaped grown GaN crystal grains can be connected into a plane in a smaller thickness and are converted into two-dimensional epitaxial growth, the crystal quality of a subsequent deposited AlGaN layer is improved, the dislocation density is reduced, and the radiation recombination efficiency of a multi-quantum well layer is improved.
In one embodiment, high purity H is obtained using a MOCVD (Metal-organic chemical vapor deposition, MOCVD) tool 2 (Hydrogen gas), high purity N 2 (Nitrogen), high purity H 2 And high purity N 2 One of the mixed gases of (1) is used as a carrier gas, high-purity NH is added 3 As the N source, trimethyl gallium (TMGa) and triethyl gallium (TEGa) as the gallium source, trimethyl aluminum (TMAl) as the aluminum source, silane (SiH) 4 ) As N-type dopant, magnesium dicocene (CP) 2 Mg) as a P-type dopant.
And S22, depositing an undoped AlGaN layer 3 on the buffer layer 2.
Preferably, an undoped AlGaN layer is deposited on the AlN buffer layer by a Metal Organic Chemical Vapor Deposition (MOCVD) method at a growth temperature of 1000 ℃ to 1300 ℃, a growth pressure of 50torr to 500torr, and a thickness of 1 μm to 5 μm.
More preferably, the undoped AlGaN layer grows at 1200 ℃ under 100torr and has a thickness of 2-3 μm. The growth temperature of the undoped AlGaN layer is higher, the pressure is lower, the quality of the prepared GaN crystal is better, meanwhile, the thickness of the AlGaN crystal increases, the compressive stress can be released through stacking faults along with the increase of the AlGaN thickness, the line defects are reduced, the crystal quality is improved, the reverse leakage is reduced, but the consumption of MO source (metal organic source) materials is larger by improving the AlGaN layer thickness, and the epitaxial cost of the light-emitting diode is greatly improved, so that the conventional light-emitting diode epitaxial wafer usually grows 2 mu m-3 mu m from the undoped AlGaN, the production cost is saved, and the GaN material has higher crystal quality.
And S23, depositing an N-type AlGaN layer 4 on the undoped AlGaN layer 3.
Preferably, an N-type AlGaN layer is deposited on the undoped AlGaN layer, the growth temperature is 1000-1300 ℃, and the doping concentration is 1 multiplied by 10 19 atoms/cm 3 -5×10 20 atoms/cm 3 The thickness is 1-5 μm.
More preferably, the growth temperature of the N-type AlGaN layer is 1200 ℃, the growth pressure is 100torr, the growth thickness is 2-3 μm, and the Si doping concentration is 2.5 × 10 19 atoms/cm 3 . Firstly, an N-type doped AlGaN layer provides sufficient electrons for the light emission of an ultraviolet LED to be compounded with holes; secondly, the resistivity of the N-type doped AlGaN layer is higher than that of the transparent electrode on the P-type GaN layer, so that sufficient Si doping can effectively reduce the resistivity of the N-type GaN layer; finally, the sufficient thickness of the N-type doped AlGaN layer can effectively release stress and improve the luminous efficiency of the light-emitting diode.
And S24, depositing the multiple quantum well layer 5 on the N-type AlGaN layer 4.
Preferably, the MQWs are Al alternately stacked m Ga 1-m N quantum well layer and Al n Ga 1-n And N quantum barrier layers, wherein the stacking period number is 3-15. Wherein Al is m Ga 1-m The growth temperature of the N quantum well layer is 950-1150 ℃, the thickness is 2-5 nm, the growth pressure is 50-300torr, and the Al component is 0.2-0.6; al (aluminum) n Ga 1-n The growth temperature of the N quantum barrier layer is 1000-1300 ℃, and the thickness is 5nm-15nm, growth pressure of 50-300torr, al component of 0.4-0.8.
More preferably, the number of stacking periods of the MQW layer is 9, and the Al m Ga 1-m The growth temperature of the N quantum well layer is 1050 ℃, the thickness is 3.5nm, the pressure is 200torr, and the Al component is 0.55; the Al is n Ga 1-n The growth temperature of the N quantum barrier layer is 1150 ℃, the thickness of the N quantum barrier layer is 11nm, the growth pressure of the N quantum barrier layer is 200torr, and the Al component is 0.7. The multiple quantum wells are areas where electrons and holes are compounded, and the reasonable structural design can obviously increase the overlapping degree of wave functions of the electrons and the holes, so that the luminous efficiency of the LED device is improved.
And S25, depositing an electron barrier layer 6 on the multi-quantum well layer 5.
Preferably, the electron blocking layer is an AlGaN electron blocking layer, the thickness is 10nm-100nm, the growth temperature is 1000 ℃ -1100 ℃, the pressure is 100torr-300torr, and the Al component is 0.4-0.8.
More preferably, the AlGaN electron blocking layer has a thickness of 30nm, wherein the Al component is 0.75, the growth temperature is 1050 ℃, and the growth pressure is 200torr. The AlGaN electron blocking layer can effectively limit electron overflow, can reduce blocking of holes, improves injection efficiency of the holes to a quantum well, reduces carrier auger recombination, and improves luminous efficiency of the light-emitting diode.
And S26, depositing a P-type AlGaN layer 7 on the electron blocking layer 6.
Preferably, the growth temperature of the P-type AlGaN layer is 1000-1100 ℃, the thickness is 20-200 nm, the growth pressure is 100-600torr, the Mg doping concentration is 1 x 10 19 atoms/cm 3 -1×10 20 atoms/cm 3 。
More preferably, the growth temperature of the P-type AlGaN layer is 1050 ℃, the thickness is 100nm, the growth pressure is 200torr, the Mg doping concentration is 5 multiplied by 10 19 atoms/cm 3 . Too high a doping concentration of Mg will deteriorate the crystal quality, while lower doping concentrations will affect the hole concentration. Meanwhile, the P-type doped AlGaN layer can effectively fill and level the epitaxial layer, and the deep ultraviolet LED epitaxial wafer with a smooth surface is obtained.
And S27, depositing a P type contact layer 8 on the P type AlGaN layer 7.
The P-type contact layer 8 is coatedComprises Mg doped B sequentially laminated on the P-type AlGaN layer 7 a Al b Ga 1-a-b N layer 81, B x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y The N superlattice layer 82 is composed of a layer more than 0 and less than 0.45, b more than 0 and less than 0.45, x more than 0 and less than 0.45, and y more than 0 and less than 0.45.
In one embodiment, the Mg is doped with B a Al b Ga 1-a-b The N layer is prepared by the following method:
introducing a nitrogen source, a boron source, an aluminum source, a gallium source and a magnesium source into the reaction chamber, taking hydrogen and nitrogen as growth atmosphere, and depositing Mg doped B on the P-type AlGaN layer a Al b Ga 1-a-b And N layers.
In one embodiment, B is x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y The N superlattice layers are prepared by the following steps:
introducing a nitrogen source, a boron source, an aluminum source and a gallium source into the reaction chamber, and taking hydrogen, nitrogen and ammonia as growth atmosphere to finish the step B x Al y Ga 1-x-y Deposition of a layer of nanoclusters;
introducing a nitrogen source, a boron source, an aluminum source, a gallium source and a magnesium source into the reaction chamber, and taking hydrogen, nitrogen and ammonia as a growth atmosphere to finish the Mg doping B x Al y Ga 1-x-y Depositing an N layer;
alternately depositing the B x Al y Ga 1-x-y Nanocluster layer and Mg doped B x Al y Ga 1-x-y N layers of the said B x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y And N superlattice layers.
In one embodiment, B is x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y In the deposition process of the N superlattice layers, the temperature in the reaction chamber is 900-1100 ℃; the pressure in the reaction chamber is 100-300 torr; in the growth atmosphere, hydrogen: nitrogen gas: ammonia gas =1: (5-10): (1-5). Preferably, theB above x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y In the deposition process of the N superlattice layer, the temperature in the reaction chamber is 1050 ℃; the pressure in the reaction chamber is 200torr; in the growth atmosphere, hydrogen: nitrogen gas: ammonia gas =1:6:3.
in the above production method, mg is doped with B in terms of growth atmosphere a Al b Ga 1-a-b The growth atmosphere of the N layer is free of ammonia gas, so that nitrogen atoms are prevented from being introduced; b is x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y Hydrogen of N-layer superlattice layer: nitrogen gas: ammonia gas =1: (5-10): (1-5), the binding energy for forming Mg-H is low, and Mg can be activated by breaking Mg-H by annealing.
In terms of growth temperature, B x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y The growth temperature of the N-layer superlattice layer is 900-1100 ℃, and the higher temperature ensures the crystal quality of the P-type contact layer. The growth pressure is 100-300 torr, the mobility of Mg atoms is improved at low pressure, and Mg is doped uniformly.
Correspondingly, the invention further provides the deep ultraviolet LED, and the deep ultraviolet LED comprises the deep ultraviolet LED epitaxial wafer. The photoelectric efficiency of the deep ultraviolet LED is effectively improved, and other electric properties are good.
The invention is further illustrated by the following specific examples:
example 1
The embodiment provides a deep ultraviolet LED epitaxial wafer, which comprises a substrate, and a buffer layer, a non-doped AlGaN layer, an N-type AlGaN layer, a multi-quantum well layer, an electron blocking layer, a P-type AlGaN layer and a P-type contact layer which are sequentially stacked on the substrate;
the P-type contact layer comprises Mg doped B which is sequentially laminated on the P-type AlGaN layer a Al b Ga 1-a-b N layer, B x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y N superlattice layers;
the Mg is doped with B a Al b Ga 1-a-b In the N layer: the B component is increased from 0.1 to 0.4 from the position close to the P-type AlGaN layer to the position far away from the P-type AlGaN layer, and the Al component is decreased from 0.45 to 0.2 from the position close to the P-type AlGaN layer to the position far away from the P-type AlGaN layer; the thickness is 7nm; mg doping concentration of 7.5X 10 19 atoms/cm 3 。
B is x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y N superlattice layers: x is 0.4 and y is 0.2; the whole layer thickness is 6nm, B x Al y Ga 1-x-y Thickness of nanocluster layer: the Mg is doped with B x Al y Ga 1-x-y Thickness of N layer =1:3; the number of superlattice periods is 3; the Mg is doped with B x Al y Ga 1-x-y The doping concentration of the N layer is 3.5 multiplied by 10 20 atoms/cm 3 。
Example 2
The present embodiment provides a deep ultraviolet LED epitaxial wafer, which is different from embodiment 1 in that: the Mg is doped with B a Al b Ga 1-a-b The thickness of the N layer is 10nm; b is x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y The thickness of the N-layer superlattice layer is 8nm. The rest is the same as in example 1.
Example 3
The present embodiment provides a deep ultraviolet LED epitaxial wafer, which is different from embodiment 1 in that: the Mg is doped with B a Al b Ga 1-a-b The thickness of the N layer is 5nm; b is described x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y The thickness of the N-layer superlattice layer is 4nm. The rest of the process was the same as in example 1.
Example 4
The present embodiment provides a deep ultraviolet LED epitaxial wafer, which is different from embodiment 1 in that: b is x Al y Ga 1-x-y Thickness of the nanocluster layer: the Mg is doped with B x Al y Ga 1-x-y Thickness of N layer =1:1. the rest of the process was the same as in example 1.
Example 5
The present embodiment provides a deep ultraviolet LED epitaxial wafer, which is different from embodiment 1 in that: b is described x Al y Ga 1-x-y Thickness of nanocluster layer: the Mg is doped with B x Al y Ga 1-x-y Thickness of N layer =1:5. the rest is the same as in example 1.
Example 6
The present embodiment provides a deep ultraviolet LED epitaxial wafer, which is different from embodiment 1 in that: b is described x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y The number of superlattice periods of the N superlattice layers is 5. The rest is the same as in example 1.
Example 7
The present embodiment provides a deep ultraviolet LED epitaxial wafer, which is different from embodiment 1 in that: x is 0.2 and y is 0.4. The rest is the same as in example 1.
Example 8
The present embodiment provides a deep ultraviolet LED epitaxial wafer, which is different from embodiment 1 in that: the Mg is doped with B a Al b Ga 1-a-b The Mg doping concentration of the N layer is 1 multiplied by 10 19 atoms/cm 3 . The rest of the process was the same as in example 1.
Example 9
The present embodiment provides a deep ultraviolet LED epitaxial wafer, which is different from embodiment 1 in that: the Mg is doped with B x Al y Ga 1-x-y The Mg doping concentration of the N layer is 8 multiplied by 10 20 atoms/cm 3 . The rest is the same as in example 1.
Comparative example 1
The embodiment provides a deep ultraviolet LED epitaxial wafer, which comprises a substrate, and a buffer layer, a non-doped AlGaN layer, an N-type AlGaN layer, a multi-quantum well layer, an electron blocking layer, a P-type AlGaN layer and a P-type contact layer which are sequentially stacked on the substrate;
the P-type contact layer is a Mg-doped P-type AlGaN contact layer and has a thickness of 20nm.
The deep ultraviolet LED epitaxial wafers prepared in examples 1 to 9 and comparative example 1 were prepared into 15 mil × 15 mil chips using the same chip process conditions, 300 LED chips were respectively extracted, and the photoelectric efficiency was measured at a current of 120mA/60 mA. The optical efficiency improvement rates of examples 1 to 9 compared to the comparative example were calculated, and the specific test results are shown in table 1.
Table 1 examples 1-9 results of performance testing of deep ultraviolet LEDs
From the above results, it can be seen that the P-type contact layer of the deep ultraviolet LED epitaxial wafer according to the present invention includes Mg-doped B sequentially stacked on the P-type AlGaN layer a Al b Ga 1-a-b N layer, B x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y And N superlattice layers. The Mg is doped with B a Al b Ga 1-a-b The N layer can reduce the activation energy of Mg and improve the concentration of activated Mg, and the wider forbidden band widths of B and N can reduce the absorption of the P-type contact layer on deep ultraviolet light and reduce the deposition of B on the back x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y The lattice mismatch of the N superlattice layers improves the crystal quality. B is described x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y N superlattice layers with B x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y The N-layer superlattice structure is used as a current expansion bridging point, so that the problems of low hole concentration and current expansion deviation caused by low Mg ionization efficiency of a P type are solved, the diffusion length of a hole of a P type contact layer is increased, the expansion capability of P type current is improved, the current accumulation effect is reduced, the ohmic contact between an epitaxial layer and an electrode is improved, the working voltage of a deep ultraviolet LED epitaxial wafer is reduced, and the luminous efficiency of the deep ultraviolet LED epitaxial wafer is improved.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.
Claims (10)
1. The deep ultraviolet LED epitaxial wafer is characterized by comprising a substrate, and a buffer layer, a non-doped AlGaN layer, an N-type AlGaN layer, a multi-quantum well layer, an electron barrier layer, a P-type AlGaN layer and a P-type contact layer which are sequentially stacked on the substrate;
the P-type contact layer comprises Mg doped B which is sequentially laminated on the P-type AlGaN layer a Al b Ga 1-a-b N layer, B x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y The N layer of superlattice layer, wherein a is more than 0 and less than 0.45, b is more than 0 and less than 0.45, x is more than 0 and less than 0.45, and y is more than 0 and less than 0.45.
2. The deep ultraviolet LED epitaxial wafer of claim 1, wherein the Mg is doped with B a Al b Ga 1-a-b In the N layer, the B component gradually rises from the position close to the P-type AlGaN layer to the position far away from the P-type AlGaN layer;
the Al component is gradually reduced from the position close to the P-type AlGaN layer to the position far away from the P-type AlGaN layer.
3. The deep ultraviolet LED epitaxial wafer of claim 1, wherein B is x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y N superlattice layers consisting of B x Al y Ga 1-x-y Nanocluster layer and Mg doped B x Al y Ga 1-x-y The N layers are sequentially and alternately laminated, and the repetition period is more than or equal to 1.
4. The deep ultraviolet LED epitaxial wafer of any one of claims 1 to 3, wherein the Mg doping B is a Al b Ga 1-a- b The thickness of the N layer is 1nm-10nm;
b is x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y The thickness of the N superlattice layers is 1nm-10nm;
b is x Al y Ga 1-x-y Nanocluster layer and said Mg doped B x Al y Ga 1-x-y The thickness ratio of the N layer is 1: (1-5).
5. The deep ultraviolet LED epitaxial wafer of any one of claims 1 to 3, wherein the Mg doping B is a Al b Ga 1-a- b The Mg doping concentration of the N layer is 1 multiplied by 10 19 atoms/cm 3 -1×10 20 atoms/cm 3 ；
The Mg is doped with B x Al y Ga 1-x-y The Mg doping concentration of the N layer is 1 multiplied by 10 20 atoms/cm 3 -1×10 21 atoms/cm 3 。
6. A preparation method of the deep ultraviolet LED epitaxial wafer as claimed in any one of claims 1 to 5, characterized by comprising the following steps:
s1, preparing a substrate;
s2, sequentially depositing a buffer layer, a non-doped AlGaN layer, an N-type AlGaN layer, a multi-quantum well layer, an electron barrier layer, a P-type AlGaN layer and a P-type contact layer on the substrate;
the P-type contact layer comprises Mg doped B which is sequentially laminated on the P-type AlGaN layer a Al b Ga 1-a-b N layer, B x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y N superlattice layers, wherein a is more than 0 and less than 0.45, b is more than 0 and less than 0.45, x is more than 0 and less than 0.45, and y is more than 0 and less than 0.45.
7. The method for preparing the deep ultraviolet LED epitaxial wafer of claim 6, wherein the Mg is doped with B a Al b Ga 1-a-b The N layer is prepared by the following method:
introducing a nitrogen source, a boron source, an aluminum source, a gallium source and a magnesium source into the reaction chamber, taking hydrogen and nitrogen as growth atmosphere, and depositing Mg doped B on the P-type AlGaN layer a Al b Ga 1-a-b And N layers.
8. The method for preparing the deep ultraviolet LED epitaxial wafer of claim 6, wherein B is x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y The N superlattice layers are prepared by the following steps:
introducing a nitrogen source, a boron source, an aluminum source and a gallium source into the reaction chamber, and taking hydrogen, nitrogen and ammonia as growth atmosphere to finish the step B x Al y Ga 1-x-y Deposition of a layer of nanoclusters;
introducing a nitrogen source, a boron source, an aluminum source, a gallium source and a magnesium source into the reaction chamber, and taking hydrogen, nitrogen and ammonia as a growth atmosphere to finish the Mg doping B x Al y Ga 1-x-y Depositing an N layer;
alternately depositing the B x Al y Ga 1-x-y Nanocluster layer and Mg doped B x Al y Ga 1-x-y N layers of the said B x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y And N superlattice layers.
9. The method for preparing the deep ultraviolet LED epitaxial wafer of claim 8, wherein B is x Al y Ga 1-x-y Nanocluster layer/Mg doped B x Al y Ga 1-x-y In the deposition process of the N superlattice layers, the temperature in the reaction chamber is 900-1100 ℃;
the pressure in the reaction chamber is 100-300 torr;
in the growth atmosphere, hydrogen: nitrogen gas: ammonia =1: (5-10): (1-5).
10. A deep ultraviolet LED, characterized in that the deep ultraviolet LED comprises the deep ultraviolet LED epitaxial wafer according to any one of claims 1 to 5.
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