Deep ultraviolet light-emitting diode epitaxial wafer and its preparation method

Abstract

The present invention relates to the field of semiconductor technology, and in particular to a deep ultraviolet light-emitting diode epitaxial wafer and a preparation method thereof, comprising: providing a substrate; sequentially epitaxially growing a buffer layer, an undoped 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 on the substrate; the undoped AlGaN layer comprising a three-dimensional nucleation layer / a two-dimensional lateral growth layer, a three-dimensional-two-dimensional transition layer, and a two-dimensional planarization layer sequentially deposited along the epitaxial growth direction; the three-dimensional nucleation layer / two-dimensional lateral growth layer comprising a three-dimensional nucleation layer and a two-dimensional lateral growth layer that are periodically and sequentially grown alternately, wherein the Al component content and growth temperature of the three-dimensional-two-dimensional transition layer gradually increase from the Al component content and growth temperature of the two-dimensional lateral growth layer to the Al component content and growth temperature of the two-dimensional planarization layer. The present invention can effectively reduce the dislocation density of the epitaxial wafer, form high-quality high-Al component AlGaN material, and thereby effectively improve the photoelectric performance of the deep ultraviolet light-emitting diode.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a deep ultraviolet light emitting diode epitaxial wafer and a preparation method thereof. Background Art

[0002] As the application of InGaN-based light-emitting diode devices matures, AlGaN, a representative wide-bandgap material among III-nitrides, has become the forefront and hotspot of III-nitride semiconductor research. AlGaN ternary alloys have a large bandgap and a high breakdown electric field. The bandgap can be adjusted over a wide range. By adjusting the Al component, the bandgap can be continuously adjusted from 3.4eV to 6.2eV. The corresponding emission wavelength can cover long-wave ultraviolet UV-A (320-400nm), medium-wave ultraviolet UV-B (280-320nm) and even short-wave deep ultraviolet UV-C (200-280nm), making it a key basic material for the preparation of solid-state ultraviolet light source devices.

[0003] Current deep-ultraviolet LEDs typically use GaN layers deposited on heterogeneous substrates such as SiC or sapphire as the device growth template. These materials absorb UV light, resulting in low light extraction efficiency. The large lattice and thermal mismatch between the high-Al content AlGaN material and the sapphire substrate results in poor crystal quality in the AlGaN epitaxial layer. During epitaxial growth, dislocation density is high and extends into the multi-quantum well layers, forming a large number of non-radiative recombination centers. This severely impacts the internal quantum efficiency and reduces the luminous efficiency of deep-ultraviolet LEDs. Summary of the Invention

[0004] The purpose of the present invention is to provide a deep ultraviolet light-emitting diode epitaxial wafer and a preparation method thereof in response to the existing technical status. The present invention can effectively reduce the dislocation density of the epitaxial wafer, form high-quality high-Al content AlGaN material, and thus effectively improve the optoelectronic performance of the deep ultraviolet light-emitting diode.

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

[0006] A method for preparing a deep ultraviolet light-emitting diode epitaxial wafer, comprising:

[0007] providing a substrate;

[0008] Epitaxially growing a buffer layer, an undoped 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 on the substrate in sequence;

[0009] The non-doped AlGaN layer includes a three-dimensional nucleation layer / a two-dimensional lateral growth layer, a three-dimensional-two-dimensional transition layer and a two-dimensional planarization layer sequentially deposited along the epitaxial growth direction;

[0010] The three-dimensional nucleation layer / two-dimensional lateral growth layer includes a three-dimensional nucleation layer and a two-dimensional lateral growth layer that grow alternately in periodic sequence. The Al component content and growth temperature of the two-dimensional lateral growth layer are lower than the Al component content and growth temperature of the two-dimensional flattening layer, and the Al component content and growth temperature of the three-dimensional-two-dimensional transition layer gradually increase from the Al component content and growth temperature of the two-dimensional lateral growth layer to the Al component content and growth temperature of the two-dimensional flattening layer.

[0011] In some embodiments, the Al component content of the three-dimensional nucleation layer / two-dimensional lateral growth layer is 0.05-0.5, the Al component content of the three-dimensional-two-dimensional transition layer is 0.1-0.5, and the Al component content of the two-dimensional planarization layer is 0.1-0.6;

[0012] The growth temperature of the three-dimensional nucleation layer is 900-1100° C., the growth temperature of the two-dimensional lateral growth layer is 1000-1200° C., and the growth temperature of the two-dimensional planarization layer is 1150-1350° C.

[0013] In some embodiments, the growth pressure of the three-dimensional nucleation layer during growth is greater than the growth pressure of the two-dimensional lateral growth layer, the three-dimensional-two-dimensional transition layer, and the two-dimensional planarization layer during growth; the V / III ratio of the three-dimensional nucleation layer during growth is lower than the V / III ratio of the two-dimensional lateral growth layer, the three-dimensional-two-dimensional transition layer, and the two-dimensional planarization layer during growth.

[0014] In some embodiments, the growth pressure of the three-dimensional nucleation layer is 300-500 Torr, the growth pressure of the two-dimensional lateral growth layer is 50-300 Torr, the growth pressure of the three-dimensional-two-dimensional transition layer is 50-200 Torr, and the growth pressure of the two-dimensional planarization layer is 50-200 Torr;

[0015] The V / III ratio of the three-dimensional nucleation layer is 100-1000, the V / III ratio of the two-dimensional lateral growth layer is 500-2000, the V / III ratio of the three-dimensional-two-dimensional transition layer is 1000-5000, and the V / III ratio of the two-dimensional flattening layer is 1000-5000.

[0016] In some embodiments, the stacking period number of the three-dimensional nucleation layer / two-dimensional lateral growth layer is 1-10.

[0017] In some embodiments, the thickness of the three-dimensional nucleation layer is 0.1-1um, the thickness of the two-dimensional lateral growth layer is 0.1-1um, the thickness of the three-dimensional-two-dimensional transition layer is 0.2-2um, and the thickness of the two-dimensional planarization layer is 0.5-5um.

[0018] In some embodiments, the buffer layer is an AlN buffer layer deposited by PVD sputtering, and the thickness of the AlN buffer layer is 20-200 nm.

[0019] In some embodiments, the growth temperature of the N-type AlGaN layer is 1000-1300° C., the thickness is 1-5 μm, and the N-type AlGaN layer is doped with Si, and the doping concentration of Si is 1.0*10 19 ~5.0*10 20 cm -3 .

[0020] In some embodiments, the multi-quantum well layer is a periodically stacked Al x Ga 1-x N quantum well layer and Al y Ga 1-y N quantum barrier layer, the Al x Ga 1-x The growth temperature of the N quantum well layer is 950-1150°C, the growth pressure is 50-300 torr, and the content of Al component is 0.2-0.6; Al y Ga 1-y The growth temperature of the N quantum barrier layer is 1000-1300°C, the growth pressure is 50-300 torr, and the content of the Al component is 0.4-0.8; the stacking period number of the multi-quantum well layer is 3-15, and the Al content in each period is 100-1300°C. x Ga 1-x The thickness of the N quantum well layer is 2 to 5 nm. y Ga 1-y The thickness of the N quantum barrier layer is 5 to 15 nm.

[0021] The present invention also provides a deep ultraviolet light emitting diode epitaxial wafer, which is prepared according to the above-mentioned method for preparing the deep ultraviolet light emitting diode epitaxial wafer.

[0022] The beneficial effects of the present invention are:

[0023] In the present invention, a three-dimensional nucleation layer / two-dimensional lateral growth layer is first used to form AlGaN into island-shaped three-dimensional crystal nuclei, and then the AlGaN is grown two-dimensionally laterally, the three-dimensional crystal nuclei are merged, and the three-dimensional nucleation layer / two-dimensional lateral growth layer is periodically stacked and deposited, thereby effectively reducing the dislocation density and improving the crystal quality. The two-dimensional flattening layer is used to form the non-doped AlGaN layer into a flat and smooth two-dimensional plane, ensuring the growth quality of the subsequent epitaxial layer. A three-dimensional-two-dimensional transition layer is provided between the three-dimensional nucleation layer / two-dimensional lateral growth layer and the two-dimensional flattening layer. By setting the Al component content and growth temperature growth trend of the three-dimensional-two-dimensional transition layer, it is ensured that high-quality high-Al component AlGaN material can be formed, and the lattice mismatch between the two-dimensional lateral growth layer and the two-dimensional flattening layer is reduced, thereby improving the crystal quality of the subsequently deposited two-dimensional flattening layer. The present invention effectively reduces the dislocation density and forms high-quality high-Al component AlGaN material by improving the non-doped AlGaN layer provided between the buffer layer and the N-type AlGaN layer, thereby effectively improving the photoelectric performance of the deep ultraviolet light-emitting diode. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a flow chart of a method for preparing a deep ultraviolet light-emitting diode epitaxial wafer.

[0025] Figure 2 This is a flow chart of step S2 of the method for preparing a deep ultraviolet light-emitting diode epitaxial wafer of the present invention.

[0026] Figure 3 is a schematic structural diagram of a deep ultraviolet light-emitting diode epitaxial wafer of the present invention, DETAILED DESCRIPTION

[0027] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is described in further detail below.

[0028] See also Figure 1 and Figure 2 As shown, the present invention discloses a method for preparing a deep ultraviolet light-emitting diode epitaxial wafer, comprising:

[0029] S10. Providing a substrate 1, wherein the substrate 1 can be any one of a sapphire substrate 1, an AlN substrate 1, a Si substrate 1, and a SiC substrate 1. Preferably, the substrate 1 is a sapphire substrate 1. Sapphire is currently the most commonly used substrate 1 material. The sapphire substrate 1 has a mature preparation process, is relatively low in price, is easy to clean and handle, and has good stability at high temperatures.

[0030] S20. Epitaxially growing a buffer layer 2, an undoped AlGaN layer 3, an N-type AlGaN layer 4, a multi-quantum well layer 5, an electron blocking layer 6, a P-type AlGaN layer 7 and a P-type contact layer 8 on the substrate 1 in sequence;

[0031] The undoped AlGaN layer 3 includes a three-dimensional nucleation layer / two-dimensional lateral growth layer 31, a three-dimensional-two-dimensional transition layer 32 and a two-dimensional planarization layer 33 sequentially deposited along the epitaxial growth direction;

[0032] The three-dimensional nucleation layer / two-dimensional lateral growth layer 31 includes a three-dimensional nucleation layer 311 and a two-dimensional lateral growth layer 312 that grow alternately in periodic sequence. The Al component content and growth temperature of the two-dimensional lateral growth layer 312 are lower than the Al component content and growth temperature of the two-dimensional planarizing layer 33, and the Al component content and growth temperature of the three-dimensional-two-dimensional transition layer 32 gradually increase from the Al component content and growth temperature of the two-dimensional lateral growth layer 312 to the Al component content and growth temperature of the two-dimensional planarizing layer 33.

[0033] In the present invention, the undoped AlGaN layer 3 between the buffer layer 2 and the N-type AlGaN layer 4 is improved. Specifically, a three-dimensional nucleation layer / two-dimensional lateral growth layer 31 is deposited on the buffer layer 2. The three-dimensional nucleation layer 311 forms an island-shaped three-dimensional crystal nucleus. Subsequently, the two-dimensional lateral growth layer 312 is used to cause the AlGaN to grow two-dimensionally laterally, merging the three-dimensional crystal nuclei and reducing the defect density. The three-dimensional nucleation layer / two-dimensional lateral growth layer 31 is periodically stacked and deposited, which can further reduce the dislocation density and improve the crystal quality. The two-dimensional flattening layer 33 forms the undoped AlGaN layer 3 into a flat and smooth two-dimensional plane, ensuring the growth quality of the subsequent epitaxial layer. At the same time, as the thickness increases, the compressive stress is released through stacking faults, reducing line defects, improving crystal quality, reducing reverse leakage, and improving the photoelectric performance of the deep ultraviolet light-emitting diode. The Al component content and growth temperature of the three-dimensional-two-dimensional transition layer 32 gradually increase from the Al component content and growth temperature of the two-dimensional lateral growth layer 312 to the Al component content and growth temperature of the two-dimensional flat layer 33. On the one hand, due to the low mobility of Al atoms, the growth temperature of the three-dimensional-two-dimensional transition layer 32 increases with the increase of Al component content, which is beneficial to improve the mobility of Al atoms and promote the incorporation of Al atoms into the AlGaN lattice, thereby ensuring the formation of high-quality high-Al component AlGaN material. On the other hand, the growth temperature growth trend setting of the three-dimensional-two-dimensional transition layer 32 can enhance the lateral growth of AlGaN, reduce the lattice mismatch between the two-dimensional lateral growth layer 312 and the two-dimensional flat layer 33, and improve the crystal quality of the subsequently deposited two-dimensional flat layer 33. In addition, the two-dimensional flat layer 33 uses a higher temperature, which can further promote the formation of a smooth two-dimensional plane.

[0034] In the present invention, a three-dimensional nucleation layer / two-dimensional lateral growth layer 31 is first used to form an island-shaped three-dimensional crystal nucleus of AlGaN, and then the AlGaN is grown two-dimensionally laterally, the three-dimensional crystal nucleus is merged, and the three-dimensional nucleation layer / two-dimensional lateral growth layer 31 is periodically stacked and deposited, thereby effectively reducing the dislocation density and improving the crystal quality. The two-dimensional flattening layer 33 is used to form the non-doped AlGaN layer 3 into a flat and smooth two-dimensional plane, ensuring the growth quality of the subsequent epitaxial layer. A three-dimensional-two-dimensional transition layer 32 is set between the three-dimensional nucleation layer / two-dimensional lateral growth layer 31 and the two-dimensional flattening layer 33. By setting the Al component content and growth temperature growth trend of the three-dimensional-two-dimensional transition layer 32, it is ensured that high-quality high-Al component AlGaN material can be formed, and the lattice mismatch between the two-dimensional lateral growth layer 312 and the two-dimensional flattening layer 33 is reduced, thereby improving the crystal quality of the subsequently deposited two-dimensional flattening layer 33. The present invention effectively reduces the dislocation density by improving the undoped AlGaN layer 3 arranged between the buffer layer 2 and the N-type AlGaN layer 4, thereby forming high-quality high-Al component AlGaN material, thereby effectively improving the photoelectric performance of the deep ultraviolet light-emitting diode.

[0035] Among them, the Al component content of the three-dimensional nucleation layer / two-dimensional lateral growth layer 31 is 0.05-0.5, and illustratively, the Al component content of the three-dimensional nucleation layer / two-dimensional lateral growth layer 31 is 0.05, 0.10, 0.20, 0.25, 0.30, 0.45 or 0.49, but not limited thereto; the Al component content of the three-dimensional-two-dimensional transition layer 32 is 0.1-0.5, and illustratively, the Al component content of the three-dimensional-two-dimensional transition layer 32 is 0.1, 0.2, 0.25, 0.3 or 0.48, but not limited thereto; the Al component content of the two-dimensional planarization layer 33 is 0.1-0.6, and illustratively, the Al component content of the two-dimensional planarization layer 33 is 0.1, 0.2, 0.25, 0.3, 0.4, 0.5 or 0.58, but not limited thereto;

[0036] Among them, the growth temperature of the three-dimensional nucleation layer 311 is 900-1100°C. Exemplarily, the growth temperature of the three-dimensional nucleation layer 311 is 900°C, 940°C, 980°C, 1080°C or 1100°C, but not limited to this; the growth temperature of the two-dimensional lateral growth layer 312 is 1000-1200°C. Exemplarily, the growth temperature of the two-dimensional lateral growth layer 312 is 1020°C, 1080°C, 1120°C, 1180°C or 1200°C, but not limited to this; the growth temperature of the two-dimensional flattening layer 33 is 1150-1350°C. Exemplarily, the growth temperature of the two-dimensional flattening layer 33 is 1150°C, 1200°C, 1250°C, 1300°C or 1350°C. The two-dimensional flattening layer 33 adopts a higher temperature to prompt AlGaN to form a flat and smooth two-dimensional plane as soon as possible.

[0037] Among them, the growth pressure during the growth of the three-dimensional nucleation layer 311 is greater than the growth pressure during the growth of the two-dimensional lateral growth layer 312, the three-dimensional-two-dimensional transition layer 32 and the two-dimensional planarization layer 33; the V / III ratio during the growth of the three-dimensional nucleation layer 311 is lower than the V / III ratio during the growth of the two-dimensional lateral growth layer 312, the three-dimensional-two-dimensional transition layer 32 and the two-dimensional planarization layer 33.

[0038] In the present invention, the three-dimensional nucleation layer 311 is grown under the growth conditions of high pressure and low V / III ratio, the two-dimensional lateral growth layer 312 is grown under the growth conditions of low pressure and high V / III ratio, the three-dimensional-two-dimensional transition layer 32 is grown under the growth conditions of low pressure and high V / III ratio, and the two-dimensional planarization layer 33 is grown under the growth conditions of low pressure and high V / III ratio.

[0039] The three-dimensional nucleation layer 311 adopts the growth conditions of higher pressure and lower V / III ratio, which can increase the size of AlGaN crystal nuclei, delay the merging of crystal nuclei, and reduce the density of crystal nuclei, thereby reducing the density of line defects formed by crystal nuclei merging, and further improving the crystal quality of AlGaN epitaxy.

[0040] The two-dimensional lateral growth layer 312 adopts the growth conditions of lower pressure and higher V / III ratio, which can effectively improve atomic mobility, promote AlGaN lateral growth, merge the three-dimensional nucleation layer 311, and reduce defect density.

[0041] The three-dimensional-two-dimensional transition layer 32 adopts the growth conditions of lower pressure and higher V / III ratio, which is conducive to further improving the mobility of Al atoms and further enhancing the lateral growth of AlGaN, reducing the lattice mismatch between the two-dimensional lateral growth layer 312 and the two-dimensional flat layer 33, and improving the crystal quality of the subsequently deposited two-dimensional flat layer 33.

[0042] Preferably, the growth pressure of the three-dimensional nucleation layer 311 is 300 torr to 500 torr. For example, the growth pressure of the three-dimensional nucleation layer 311 is 320 torr, 380 torr, 420 torr, 480 torr or 500 torr, but is not limited thereto. When the growth pressure is too low, the size of the crystal nuclei is too small, and the linear defect density after the crystal nuclei merge is too high. When the growth pressure is too high, the size of the crystal nuclei is too large, and it is easy to merge in advance, forming an uneven morphology, which affects the quality of the subsequent epitaxial crystal. The growth pressure of the two-dimensional lateral growth layer 312 is 50 torr to 300 torr. For example, the growth pressure of the two-dimensional lateral growth layer 312 is 50 torr, 120 torr, 480 torr or 500 torr. 200torr, 250torr or 290torr, but not limited thereto; when the growth pressure is too large, it is not conducive to the lateral growth of AlGaN; the growth pressure of the three-dimensional-two-dimensional transition layer 32 is 50-200torr, and exemplarily, the growth pressure of the three-dimensional-two-dimensional transition layer 32 is 55torr, 80torr, 120torr, 170torr or 200torr, but not limited thereto; the growth pressure of the two-dimensional flat layer 33 is 50-200torr, and exemplarily, the growth pressure of the two-dimensional flat layer 33 is 50torr, 90torr, 130torr, 180torr or 200torr, but not limited thereto.

[0043] The V / III ratio of the three-dimensional nucleation layer 311 is 100 to 1000. For example, the V / III ratio of the three-dimensional nucleation layer 311 is 100, 300, 500, 700, 750, 900 or 1000, but not limited thereto. The V / III ratio of the two-dimensional lateral growth layer 312 is 500 to 2000. For example, the V / III ratio of the two-dimensional lateral growth layer 312 is 500, 800, 1200, 1450, 1750 or 2000, but not limited thereto. ; The V / III ratio of the three-dimensional-two-dimensional transition layer 32 is 1000 to 5000. Exemplarily, the V / III ratio of the three-dimensional-two-dimensional transition layer 32 is 1000, 2200, 3500, 4200 or 4900, but not limited thereto. The V / III ratio of the two-dimensional flattening layer 33 is 1000 to 5000. Exemplarily, the V / III ratio of the two-dimensional flattening layer 33 is 1000, 1800, 2500, 3800, 4500 or 5000, but not limited thereto.

[0044] The stacking period of the three-dimensional nucleation layer / two-dimensional lateral growth layer 31 is 1 to 10. Exemplarily, the stacking period is 1, 3, 5, 7, 8, or 10, but is not limited thereto. The periodic stacking of the three-dimensional nucleation layer / two-dimensional lateral growth layer 31 can effectively reduce dislocation density and improve crystal quality. Preferably, the stacking period of the three-dimensional nucleation layer / two-dimensional lateral growth layer 31 is 2 to 9, and more preferably, the stacking period is 5.

[0045] The thickness of the three-dimensional nucleation layer 311 is 0.1 to 1 um, and exemplarily, the thickness is 0.1 um, 0.3 um, 0.65 um, 0.8 um or 1 um, but not limited thereto; when the thickness of the three-dimensional nucleation layer 311 is too large, it is easy to increase the difficulty of obtaining a flat two-dimensional plane in the subsequent two-dimensional flattening layer 33; the thickness of the two-dimensional lateral growth layer 312 is 0.1 to 1 um, and exemplarily, the thickness is 0.1 um, 0.3 um, 0.75 um, 0.9 um or 1 um, but not limited thereto; the thickness of the three-dimensional-two-dimensional transition layer 32 is 0.2 to 2 um, and exemplarily, the thickness is 0. The thickness is 0.2um, 0.6um, 0.9um, 1.3um or 1.8um, but not limited to this; when the thickness of the three-dimensional-two-dimensional transition layer 32 is too small, the transition effect is not obvious, and there is likely to be a large lattice mismatch between the two-dimensional lateral growth layer 312 and the two-dimensional flat layer 33; the thickness of the two-dimensional flat layer 33 is 0.5~5um, and exemplarily, the thickness is 0.5um, 1.5um, 2.5um, 3.8um or 4.8um, but not limited to this. The two-dimensional flat layer 33 adopts a larger thickness to obtain a flat and smooth two-dimensional plane to ensure the growth quality of the subsequent epitaxial layer.

[0046] Among them, the buffer layer 2 is an AlN buffer layer 2 deposited by PVD sputtering, and the thickness of the AlN buffer layer 2 is 20 to 200 nm. Exemplarily, the thickness is 20 nm, 60 nm, 100 nm, 150 nm or 190 nm, but not limited thereto. Through the PVD sputtering deposition technology, a uniform AlN buffer layer 2 can be easily and quickly obtained. The uniform AlN buffer layer 2 provides a nucleation center with the same orientation as the substrate 1, releases the stress generated by the lattice mismatch between the AlGaN and the substrate 1 and the thermal stress generated by the mismatch of the thermal expansion coefficient, provides a flat nucleation surface for the subsequent growth of the three-dimensional nucleation layer 311, reduces the contact angle of its nucleation growth, and enables the island-like grown grains to be connected into a surface within a smaller thickness, transforming into two-dimensional epitaxial growth, thereby improving the crystal quality of the subsequently deposited AlGaN layer, reducing the dislocation density, and improving the radiation recombination efficiency of the multi-quantum well layer 5, thereby effectively improving the photoelectric performance of the deep ultraviolet light-emitting diode.

[0047] The growth temperature of the N-type AlGaN layer 4 is 1000-1300°C, and illustratively, the growth temperature is 1000°C, 1050°C, 1100°C, 1150°C, 1200°C or 1280°C, but not limited thereto; the thickness is 1-5um, and illustratively, the thickness is 1um, 2um, 2.5um, 3um, 4um or 5um, but not limited thereto. Depositing an N-type AlGaN layer 4 of sufficient thickness can effectively release stress and improve the luminous efficiency of the light-emitting diode; and the N-type AlGaN layer 4 is doped with Si, and the doping concentration of Si is 1.0*10 19~5.0*10 20 cm -3， For example, the doping concentration of Si is 1.0*10 19 cm -3 , 5.0*10 19 cm -3 , 9.0*10 19 cm -3 , 1.0*10 20 cm -3 , 3.0*10 20 cm -3 or 5.0*10 20 cm -3 , but not limited to this.

[0048] In the present invention, the Si-doped N-type AlGaN layer 4 provides sufficient electrons and holes for recombination for UV LED light emission. Due to the high resistivity of the N-type AlGaN layer 4, sufficient Si doping can effectively reduce the resistivity.

[0049] The multi-quantum well layer 5 is a periodically stacked Al x Ga 1-x N quantum well layer and Al y Ga 1-y N quantum barrier layer, Al x Ga 1-x The growth temperature of the N quantum well layer is 950-1150° C., exemplarily, the growth temperature is 950° C., 1000° C., 1050° C. or 1100° C., but not limited thereto; the growth pressure is 50-300 torr, exemplarily, the growth pressure is 50 torr, 80 torr, 120 torr, 200 torr, 250 torr or 300 torr, but not limited thereto; the content of the Al component is 0.2-0.6, exemplarily, the content of the Al component is 0.2, 0.3, 0.4, 0.5 or 0.6, but not limited thereto; Al y Ga 1-yThe growth temperature of the N quantum barrier layer is 1000-1300°C, and exemplarily, the growth temperature is 1000°C, 1050°C, 1100°C, 1150°C, 1200°C or 1300°C, but not limited thereto; the growth pressure is 50-300 torr, and exemplarily, the growth pressure is 60 torr, 80 torr, 110 torr, 200 torr, 250 torr or 300 torr, but not limited thereto; the content of the Al component is 0.4-0.8, and exemplarily, the content of the Al component is 0.4, 0.5, 0.65, 0.7 or 0.8, but not limited thereto; the number of stacking periods of the multi-quantum well layer 5 is 3-15, and exemplarily, the number of stacking periods is 3, 5, 8, 12, 14 or 15, but not limited thereto; the Al content in each period is 0.4-0.8, and 0.4, 0.5, 0.65, 0.7 or 0.8, but not limited thereto; the number of stacking periods of the multi-quantum well layer 5 is 3-15, and exemplarily, the number of stacking periods is 3, 5, 8, 12, 14 or 15, but not limited thereto; x Ga 1-x The thickness of the N quantum well layer is 2-5 nm, and for example, the thickness is 2 nm, 3 nm, 3.5 nm, 4 nm or 5 nm, but not limited thereto. y Ga 1-y The thickness of the N quantum barrier layer is 5 to 15 nm, and exemplary thicknesses include 5 nm, 8 nm, 11 nm, 13.5 nm, 14 nm, or 14.8 nm, but is not limited thereto. The multi-quantum well layer 5 is the region where electrons and holes recombine. The present invention significantly increases the overlap of electron and hole wave functions through rational structural design, thereby improving the luminous efficiency of the LED device.

[0050] Among them, the electron blocking layer 6 is an AlGaN electron blocking layer 6, whose Al component content is 0.4-0.8, thickness is 10-100nm, growth temperature is 1000-1100°C, and pressure is 100-300torr. It can not only effectively limit electron overflow, but also reduce the blocking of holes, improve the injection efficiency of holes into the quantum well, reduce carrier Auger recombination, and improve the luminous efficiency of the light-emitting diode.

[0051] The growth temperature of the P-type AlGaN layer 7 is 1000-1100°C, the thickness is 20-200 nm, the growth pressure is 100-600 Torr, and the Mg doping concentration is 1.0*10 19 ~5.0*10 20 cm -3 , the preferred Mg doping concentration is 5.0*10 20 cm -3 Too high a Mg doping concentration can damage the crystal quality, while too low a doping concentration can affect the hole concentration. Meanwhile, the P-type doped AlGaN layer can effectively fill the epitaxial layer, resulting in a smooth surface for deep ultraviolet LED epitaxial wafers.

[0052] The growth temperature of the P-type contact layer 8 is 900-1100°C, the thickness is 5-50nm, the growth pressure is 100-600torr, and the Mg doping concentration is 5.0*10 19 ~5.0*10 20 cm -3 , the preferred Mg doping concentration is 1.0*10 20 cm -3 , the high doping concentration P-type GaN contact layer can reduce the contact resistance.

[0053] The present invention also provides a deep ultraviolet light-emitting diode epitaxial wafer, which is prepared according to the above-mentioned deep ultraviolet light-emitting diode epitaxial wafer preparation method. The non-doped AlGaN layer 3 of the epitaxial wafer prepared by the present invention has high crystal quality and low dislocation density, which can effectively improve the luminous efficiency of the ultraviolet light-emitting diode.

[0054] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0055] Example 1

[0056] See Figure 1 As shown, a method for preparing a deep ultraviolet light-emitting diode epitaxial wafer includes:

[0057] S10 provides a sapphire substrate 1;

[0058] S20. Epitaxially growing a buffer layer 2, an undoped AlGaN layer 3, an N-type AlGaN layer 4, a multi-quantum well layer 5, an electron blocking layer 6, a P-type AlGaN layer 7 and a P-type contact layer 8 on the substrate 1 in sequence;

[0059] The undoped AlGaN layer 3 includes a three-dimensional nucleation layer / two-dimensional lateral growth layer 31, a three-dimensional-two-dimensional transition layer 32 and a two-dimensional planarization layer 33 sequentially deposited along the epitaxial growth direction;

[0060] The three-dimensional nucleation layer / two-dimensional lateral growth layer 31 includes a three-dimensional nucleation layer 311 and a two-dimensional lateral growth layer 312 that grow alternately in periodic sequence. The Al component content and growth temperature of the three-dimensional-two-dimensional transition layer 32 gradually increase from the Al component content and growth temperature of the two-dimensional lateral growth layer 312 to the Al component content and growth temperature of the two-dimensional flattening layer 33.

[0061] Among them, see Figure 2 As shown, the specific steps of S20 are as follows:

[0062] S21. An AlN buffer layer 2 with a thickness of 100 nm was deposited by PVD sputtering, and then transferred to MOCVD for subsequent epitaxial deposition, wherein one of high-purity H2 (hydrogen), high-purity N2 (nitrogen), or a mixture of high-purity H2 and high-purity N2 was used as a carrier gas, high-purity NH3 was used as a N source, trimethylgallium (TMGa) and triethylgallium (TEGa) were used as Ga sources, trimethylaluminum (TMAl) was used as an Al source, silane (SiH4) was used as an N-type dopant, and bis(cyclopentadienyl)magnesium (CP2Mg) was used as a P-type dopant;

[0063] S22. Depositing a non-doped AlGaN layer 3 on the buffer layer 2:

[0064] The Al component content of the three-dimensional nucleation layer / two-dimensional lateral growth layer 31 is 0.3, the Al component content of the two-dimensional planarization layer 33 is 0.4, and the Al component content of the three-dimensional-two-dimensional transition layer 32 gradually increases along the epitaxial direction from the Al component content of the two-dimensional lateral growth layer 312 to the Al component content of the two-dimensional planarization layer 33;

[0065] The thickness of the three-dimensional nucleation layer 311 is 0.5 μm, the thickness of the two-dimensional lateral growth layer 312 is 0.5 μm, the thickness of the three-dimensional-two-dimensional transition layer 32 is 0.8 μm, and the thickness of the two-dimensional planarization layer 33 is 1.5 μm.

[0066] The growth pressure of the 3D nucleation layer 311 is 350 Torr, the growth pressure of the 2D lateral growth layer 312 is 150 Torr, the growth pressure of the 3D-2D transition layer 32 is 100 Torr, and the growth pressure of the 2D planarization layer 33 is 100 Torr.

[0067] The V / III ratio of the three-dimensional nucleation layer 311 is 500, the V / III ratio of the two-dimensional lateral growth layer 312 is 1000, the V / III ratio of the three-dimensional-two-dimensional transition layer 32 is 3000, and the V / III ratio of the two-dimensional planarization layer 33 is 3000;

[0068] The growth temperature of the three-dimensional nucleation layer 311 is 980° C., the growth temperature of the two-dimensional lateral growth layer 312 is 1100° C., and the growth temperature of the three-dimensional-two-dimensional transition layer 32 gradually increases from the growth temperature of the two-dimensional lateral growth layer 312 to the growth temperature of the two-dimensional planarization layer 33. The growth temperature of the two-dimensional planarization layer 33 is 1200° C.

[0069] The number of stacking periods of the three-dimensional nucleation layer / two-dimensional lateral growth layer 31 is 5.

[0070] S23. Depositing an N-type AlGaN layer 4 on the undoped AlGaN layer 3:

[0071] The growth temperature is controlled at 1200℃, the growth pressure is 100torr, the growth thickness is 2um, and the Si doping concentration is 2.5*1019 cm -3 .

[0072] S24. Depositing a multi-quantum well layer 5 on the N-type AlGaN layer 4:

[0073] The multi-quantum well layer 5 is a periodically stacked Al 0.45 Ga 0.55 N quantum well layer and Al 0.55 Ga 0.45 N quantum barrier layer, Al 0.45 Ga 0.55 The growth temperature of the N quantum well layer is 1050℃ and the growth pressure is 200torr; Al 0.55 Ga 0.45 The growth temperature of the N quantum barrier layer is 1150℃ and the growth pressure is 200torr. The stacking period of the multi-quantum well layer 5 is 9, and the Al 0.45 Ga 0.55 The thickness of the N quantum well layer is 3.5nm, and the Al 0.55 Ga 0.45 The thickness of the N quantum barrier layer is 11 nm.

[0074] S25. Depositing an AlGaN electron blocking layer 6 on the multi-quantum well layer 5:

[0075] The AlGaN electron blocking layer 6 has a thickness of 30 nm, an Al composition of 0.65, a growth temperature of 1050° C., and a growth pressure of 200 Torr.

[0076] S26. Depositing a P-type AlGaN layer 7 on the electron blocking layer 6:

[0077] The growth temperature of the P-type AlGaN layer 7 is 1050°C, the thickness is 100 nm, the growth pressure is 200 Torr, and the Mg doping concentration is 5.0*10 20 cm -3 .

[0078] S27. Depositing a P-type contact layer 8 on the P-type AlGaN layer 7:

[0079] The growth temperature of the P-type contact layer 8 is 1050°C, the thickness is 10 nm, the growth pressure is 200 Torr, and the Mg doping concentration is 1.0*10 20 cm -3 .

[0080] Example 2

[0081] The difference between this embodiment and embodiment 1 is that in step S22:

[0082] The thickness of the three-dimensional nucleation layer 311 is 0.1 um, the thickness of the two-dimensional lateral growth layer 312 is 0.1 um, the thickness of the three-dimensional-two-dimensional transition layer 32 is 0.8 um, and the thickness of the two-dimensional planarization layer 33 is 1.5 um.

[0083] Example 3

[0084] The difference between this embodiment and embodiment 1 is that in step S22:

[0085] The thickness of the three-dimensional nucleation layer 311 is 1 um, the thickness of the two-dimensional lateral growth layer 312 is 1 um, the thickness of the three-dimensional-two-dimensional transition layer 32 is 0.8 um, and the thickness of the two-dimensional planarization layer 33 is 1.5 um.

[0086] Example 4

[0087] The difference between this embodiment and embodiment 1 is that in step S22:

[0088] The growth pressure of the three-dimensional nucleation layer 311 is 300 torr, the growth pressure of the two-dimensional lateral growth layer 312 is 50 torr, the growth pressure of the three-dimensional-two-dimensional transition layer 32 is 100 torr, and the growth pressure of the two-dimensional planarization layer 33 is 100 torr.

[0089] Example 5

[0090] The difference between this embodiment and embodiment 1 is that in step S22:

[0091] The growth pressure of the three-dimensional nucleation layer 311 is 500 torr, the growth pressure of the two-dimensional lateral growth layer 312 is 300 torr, the growth pressure of the three-dimensional-two-dimensional transition layer 32 is 100 torr, and the growth pressure of the two-dimensional planarization layer 33 is 100 torr.

[0092] Example 6

[0093] The difference between this embodiment and embodiment 1 is that in step S22:

[0094] The V / III ratio of the three-dimensional nucleation layer 311 is 100, the V / III ratio of the two-dimensional lateral growth layer 312 is 500, the V / III ratio of the three-dimensional-two-dimensional transition layer 32 is 3000, and the V / III ratio of the two-dimensional planarization layer 33 is 3000;

[0095] Example 7

[0096] The difference between this embodiment and embodiment 1 is that in step S22:

[0097] The V / III ratio of the three-dimensional nucleation layer 311 is 1000, the V / III ratio of the two-dimensional lateral growth layer 312 is 2000, the V / III ratio of the three-dimensional-two-dimensional transition layer 32 is 3000, and the V / III ratio of the two-dimensional planarization layer 33 is 3000;

[0098] Example 8

[0099] The difference between this embodiment and embodiment 1 is that in step S22:

[0100] The growth temperature of the three-dimensional nucleation layer 311 is 900° C., the growth temperature of the two-dimensional lateral growth layer 312 is 1000° C., and the growth temperature of the three-dimensional-two-dimensional transition layer 32 gradually increases from the growth temperature of the two-dimensional lateral growth layer 312 to the growth temperature of the two-dimensional planarization layer 33. The growth temperature of the two-dimensional planarization layer 33 is 1200° C.

[0101] Example 9

[0102] The difference between this embodiment and embodiment 9 is that in step S22:

[0103] The stacking period number of the three-dimensional nucleation layer / two-dimensional lateral growth layer 31 is one.

[0104] Comparative Example 1

[0105] The difference between this comparative example and Example 1 is that in step S22:

[0106] The Al component content of the three-dimensional nucleation layer / two-dimensional lateral growth layer 31 is 0.4, the Al component content of the two-dimensional flattening layer 33 is 0.3, and the Al component content of the three-dimensional-two-dimensional transition layer 32 gradually decreases along the epitaxial direction from the Al component content of the two-dimensional lateral growth layer 312 to the Al component content of the two-dimensional flattening layer 33.

[0107] Comparative Example 2

[0108] The difference between this embodiment and embodiment 1 is that in step S22:

[0109] The growth temperature of the three-dimensional nucleation layer 311 is 1100° C., and the growth temperatures of the two-dimensional lateral growth layer 312 , the three-dimensional-two-dimensional transition layer 32 and the two-dimensional planarization layer 33 are all 1200° C.

[0110] Comparative Example 3

[0111] The difference between this comparative example and Example 1 is that in step S22, a conventional undoped AlGaN layer is deposited on the buffer layer, wherein the Al component content is 0.4, the thickness of the undoped AlGaN layer is 6 nm, the growth pressure is 100, the V / III ratio is 3000, and the growth temperature is 1200°C.

[0112] The brightness of the epitaxial wafers prepared in Examples 1 to 9 and Comparative Examples 1 to 3 was tested, and the brightness L1 measured in Examples 1 to 9 and Comparative Examples 1 to 2 was compared with the brightness L2 measured in Comparative Example 3 to obtain the light efficiency improvement rate of Examples 1 to 9 and Comparative Examples 1 to 2.

[0113] The calculation formula of the light efficiency improvement rate W is: W = (L1-L2) / L2

[0114] The measured results are as follows:

[0115]

[0116]

[0117] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with this patent can make slight changes or modifications to equivalent embodiments using the above technical content without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the solution of the present invention.

Claims

1. A method for preparing a deep ultraviolet light-emitting diode epitaxial wafer, characterized in that: include: providing a substrate; Epitaxially growing a buffer layer, an undoped 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 on the substrate in sequence; The non-doped AlGaN layer includes a three-dimensional nucleation layer / a two-dimensional lateral growth layer, a three-dimensional-two-dimensional transition layer and a two-dimensional planarization layer sequentially deposited along the epitaxial growth direction; The three-dimensional nucleation layer / two-dimensional lateral growth layer includes a three-dimensional nucleation layer and a two-dimensional lateral growth layer that grow alternately in periodic sequence. The Al component content and growth temperature of the two-dimensional lateral growth layer are lower than the Al component content and growth temperature of the two-dimensional flattening layer, and the Al component content and growth temperature of the three-dimensional-two-dimensional transition layer gradually increase from the Al component content and growth temperature of the two-dimensional lateral growth layer to the Al component content and growth temperature of the two-dimensional flattening layer.

2. The method for preparing a deep ultraviolet light-emitting diode epitaxial wafer according to claim 1, wherein: The Al component content of the three-dimensional nucleation layer / two-dimensional lateral growth layer is 0.05-0.5, the Al component content of the three-dimensional-two-dimensional transition layer is 0.1-0.5, and the Al component content of the two-dimensional planarization layer is 0.1-0.6; The growth temperature of the three-dimensional nucleation layer is 900-1100° C., the growth temperature of the two-dimensional lateral growth layer is 1000-1200° C., and the growth temperature of the two-dimensional planarization layer is 1150-1350° C.

3. The method for preparing a deep ultraviolet light-emitting diode epitaxial wafer according to claim 1, wherein: The growth pressure of the three-dimensional nucleation layer during growth is greater than the growth pressure of the two-dimensional lateral growth layer, the three-dimensional-two-dimensional transition layer and the two-dimensional planarization layer during growth; the V / III ratio of the three-dimensional nucleation layer during growth is lower than the V / III ratio of the two-dimensional lateral growth layer, the three-dimensional-two-dimensional transition layer and the two-dimensional planarization layer during growth.

4. The method for preparing a deep ultraviolet light-emitting diode epitaxial wafer according to claim 3, wherein: The growth pressure of the three-dimensional nucleation layer is 300-500 Torr, the growth pressure of the two-dimensional lateral growth layer is 50-300 Torr, the growth pressure of the three-dimensional-two-dimensional transition layer is 50-200 Torr, and the growth pressure of the two-dimensional flattening layer is 50-200 Torr; The V / III ratio of the three-dimensional nucleation layer is 100-1000, the V / III ratio of the two-dimensional lateral growth layer is 500-2000, the V / III ratio of the three-dimensional-two-dimensional transition layer is 1000-5000, and the V / III ratio of the two-dimensional flattening layer is 1000-5000.

5. The method for preparing a deep ultraviolet light-emitting diode epitaxial wafer according to claim 1, wherein: The stacking period number of the three-dimensional nucleation layer / two-dimensional lateral growth layer is 1-10.

6. The method for preparing a deep ultraviolet light-emitting diode epitaxial wafer according to claim 1, wherein: The thickness of the three-dimensional nucleation layer is 0.1-1um, the thickness of the two-dimensional lateral growth layer is 0.1-1um, the thickness of the three-dimensional-two-dimensional transition layer is 0.2-2um, and the thickness of the two-dimensional flattening layer is 0.5-5um.

7. The method for preparing a deep ultraviolet light-emitting diode epitaxial wafer according to claim 1, wherein: The buffer layer is an AlN buffer layer deposited by PVD sputtering, and the thickness of the AlN buffer layer is 20-200 nm.

8. The method for preparing a deep ultraviolet light-emitting diode epitaxial wafer according to claim 1, wherein: The growth temperature of the N-type AlGaN layer is 1000-1300°C, the thickness is 1-5 μm, and the N-type AlGaN layer is doped with Si, and the doping concentration of Si is 1.0*10 19 ~5.0*10 20 cm -3 .

9. The method for preparing a deep ultraviolet light-emitting diode epitaxial wafer according to claim 1, wherein: The multi-quantum well layer is an Al x Ga 1-x N quantum well layer and Al y Ga 1-y N quantum barrier layer, the Al x Ga 1-x The growth temperature of the N quantum well layer is 950-1150°C, the growth pressure is 50-300 torr, and the content of Al component is 0.2-0.6; Al y Ga 1-y The growth temperature of the N quantum barrier layer is 1000-1300°C, the growth pressure is 50-300 torr, and the content of the Al component is 0.4-0.8; the stacking period number of the multi-quantum well layer is 3-15, and the Al content in each period is 100-1300°C. x Ga 1-x The thickness of the N quantum well layer is 2 to 5 nm. y Ga 1-y The thickness of the N quantum barrier layer is 5 to 15 nm.

10. A deep ultraviolet light-emitting diode epitaxial wafer, characterized in that: It is prepared according to the method for preparing a deep ultraviolet light-emitting diode epitaxial wafer according to any one of claims 1 to 9.

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