Deep ultraviolet light emitting diode and epitaxial growth method thereof

Abstract

The application provides a deep ultraviolet light emitting diode and an epitaxial growth method thereof, which comprises, from bottom to top, a substrate, an intrinsic layer, an electron injection layer, a current spreading layer, a quantum well active layer, an electron blocking layer, a hole injection layer and a composite ohmic contact layer. The composite ohmic contact layer comprises, from bottom to top, a first sub-layer and a second sub-layer. The first sub-layer is a metal-polarity semiconductor layer, and the second sub-layer is a nitrogen-polarity semiconductor layer. When the first sub-layer is P-type doped, the deep ultraviolet light emitting diode can provide a large number of holes. Meanwhile, the first sub-layer also serves as a necessary condition for activating polarity conversion, so that part of the first sub-layer is converted into the second sub-layer after nitrogenization treatment. The second sub-layer has more nitrogen dangling bonds on the surface, so that the doping efficiency of the second sub-layer can be improved, thereby reducing the contact resistance of the deep ultraviolet light emitting diode, and further improving the wall plug efficiency of the deep ultraviolet light emitting diode.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optoelectronics, and more particularly to a deep ultraviolet light-emitting diode and its epitaxial growth method. Background Technology

[0002] In the ultraviolet spectrum, light with wavelengths between 200 and 350 nanometers is called deep ultraviolet light. Deep ultraviolet light-emitting diodes (LEDs) have significant application value in fields such as lighting, sterilization, medical treatment, printing, biochemical detection, high-density information storage, and secure communication due to their advantages of high efficiency, environmental friendliness, energy saving, and reliability—advantages that ordinary ultraviolet LEDs cannot match.

[0003] Currently, deep ultraviolet (DUV) light-emitting diodes (LEDs) typically operate at relatively high voltages. This is partly due to the fact that the ohmic contact layer in existing DUVs is generally made of P-type doped aluminum gallium nitride (AlGaN) with a gallium polarity, and the dopant is magnesium (Mg). This results in a relatively high contact resistance between the ohmic contact layer and the P-type electrode. To reduce this contact resistance, the ohmic contact layer needs to be doped with a high concentration of Mg. However, simply increasing the Mg doping concentration in AlGaN does not necessarily lead to a higher hole concentration in the ohmic contact layer. This is because heavy doping of Mg introduces a large number of defects, creating a self-compensation effect that actually reduces the Mg doping concentration. Consequently, it becomes difficult to reduce the contact resistance between the ohmic contact layer and the P-type electrode in existing DUVs, leading to a higher operating voltage.

[0004] Therefore, there is an urgent need for a deep ultraviolet light-emitting diode and its epitaxial growth method to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide a deep ultraviolet light-emitting diode and its epitaxial growth method, in order to improve the technical problem of low wall-insertion efficiency of existing deep ultraviolet light-emitting diodes.

[0006] To solve the above-mentioned technical problems, the present invention provides a deep ultraviolet light-emitting diode, comprising a substrate, an intrinsic layer, an electron injection layer, a current spreading layer, a quantum well active layer, an electron blocking layer, a hole injection layer, and a composite ohmic contact layer stacked from bottom to top;

[0007] The composite ohmic contact layer includes a first sublayer and a second sublayer stacked from bottom to top. The first sublayer is a metal polar semiconductor layer, and the second sublayer is a nitrogen polar semiconductor layer.

[0008] In the deep ultraviolet light-emitting diode provided in the embodiments of the present invention, the growth temperature of the first sublayer is T1, and the growth temperature of the second sublayer is T2;

[0009] The relationship between T1 and T2 satisfies 400℃≤T1<T2≤900℃, and 20℃≤T2-T1≤100℃.

[0010] In the deep ultraviolet light-emitting diode provided in the embodiments of the present invention, the dopants of the first sublayer and the second sublayer are Si or Mg, and the doping concentration ranges from 1E18cm⁻¹. -3 Up to 1E21cm -3 between.

[0011] In the deep ultraviolet light-emitting diode provided in the embodiments of the present invention, the material of the second sub-layer is any one of uniform silicon-doped nitrogen-polarized aluminum gallium nitride material, uniform magnesium-doped nitrogen-polarized aluminum gallium nitride material, delta-type silicon-doped nitrogen-polarized aluminum gallium nitride material, and delta-type magnesium-doped nitrogen-polarized aluminum gallium nitride material.

[0012] In the deep ultraviolet light-emitting diode provided in the embodiments of the present invention, the mass percentage of aluminum component in the second sublayer ranges from 0.1% to 100%, and the thickness of the second sublayer ranges from 0.1 nm to 10 nm.

[0013] In the deep ultraviolet light-emitting diode provided in the embodiments of the present invention, the material of the first sub-layer is silicon-doped aluminum gallium nitride with a metallic polar surface or magnesium-doped aluminum gallium nitride with a metallic polar surface; the mass percentage of aluminum component in the first sub-layer ranges from 0.1% to 100%, and the thickness of the first sub-layer ranges from 1 nm to 20 nm.

[0014] In the deep ultraviolet light-emitting diode provided in the embodiments of the present invention, the deep ultraviolet light-emitting diode further includes an N-type electrode and a P-type electrode;

[0015] In this structure, a stepped structure is formed between the electron injection layer and the current spreading layer, and the area of ​​the electron injection layer is larger than that of the current spreading layer. The P-type electrode is disposed on the composite ohmic contact layer, and the N-type electrode is disposed at the stepped structure of the electron injection layer.

[0016] Accordingly, embodiments of the present invention also provide an epitaxial growth method for deep ultraviolet light-emitting diodes, the method comprising:

[0017] An intrinsic layer is epitaxially grown on a substrate;

[0018] An electron-injected layer is epitaxially grown on the intrinsic layer;

[0019] Epitaxial growth of a current-spreading layer on the electron injection layer;

[0020] A quantum well active layer is epitaxially grown on the current spreading layer;

[0021] An electron blocking layer is epitaxially grown on the active layer of a quantum well;

[0022] Epitaxial growth of a hole injection layer on an electron blocking layer;

[0023] A composite ohmic contact layer is epitaxially grown on the hole injection layer;

[0024] The composite ohmic contact layer includes a first sublayer and a second sublayer stacked from bottom to top. The first sublayer is a metal polar semiconductor layer, and the second sublayer is a nitrogen polar semiconductor layer.

[0025] In the epitaxial growth method for deep ultraviolet light-emitting diodes provided in this embodiment of the invention, the step of epitaxially growing a composite ohmic contact layer on the hole injection layer further includes:

[0026] After the first sublayer growth is completed, the MO source is stopped, ammonia and hydrogen are retained, and nitrogen is introduced.

[0027] After adjusting the temperature of the reaction chamber to between 800°C and 1100°C, a portion of the first sublayer is nitrided to obtain the second sublayer.

[0028] In the epitaxial growth method of the deep ultraviolet light-emitting diode provided in the embodiments of the present invention, the second sublayer is a nitrogen polar surface aluminum gallium nitride material doped with δ-type silicon or δ-type magnesium.

[0029] The number of doping events for δ-type silicon doping or δ-type magnesium doping ranges from 1 to 10, and the interval between two adjacent δ-type silicon doping events or two adjacent δ-type magnesium doping events ranges from 1 nm to 5 nm.

[0030] The beneficial effects of this invention are as follows: Unlike the prior art, this invention provides a composite ohmic contact layer on the side of the hole injection layer away from the substrate. The composite ohmic contact layer includes a first sublayer and a second sublayer stacked from bottom to top. The first sublayer is a metal polar semiconductor layer, and the second sublayer is a nitrogen polar semiconductor layer. When the first sublayer is P-type doped, it can provide a large number of holes to the deep ultraviolet light-emitting diode (DUV), thereby improving the wall-insertion efficiency of the DUV. At the same time, the first sublayer also serves as a necessary condition for activating polarity conversion, so that part of the first sublayer is converted into the second sublayer after nitriding treatment. Since the surface of the nitrogen polar semiconductor layer has more nitrogen dangling bonds, the second sublayer can improve its own doping efficiency, thereby reducing the contact resistance of the DUV and further improving the wall-insertion efficiency of the DUV. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of the deep ultraviolet light-emitting diode provided in an embodiment of the present invention;

[0032] Figure 2 This is a process flow diagram of the epitaxial growth method for deep ultraviolet light-emitting diodes provided in an embodiment of the present invention. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] Please see Figure 1 The present invention provides a deep ultraviolet light-emitting diode 100, comprising a substrate 11, an intrinsic layer 12, an electron injection layer 13, a current spreading layer 14, a quantum well active layer 15, an electron blocking layer 16, a hole injection layer 17, and a composite ohmic contact layer 18 stacked from bottom to top.

[0035] The composite ohmic contact layer 18 includes a first sub-layer 181 and a second sub-layer 182 stacked from bottom to top. The first sub-layer 181 is a metal polar semiconductor layer, and the second sub-layer 182 is a nitrogen polar semiconductor layer.

[0036] This invention provides a composite ohmic contact layer 18 on the side of the hole injection layer 17 away from the substrate 11. The composite ohmic contact layer 18 includes a first sub-layer 181 and a second sub-layer 182 stacked from bottom to top. The first sub-layer 181 is a metal polarized semiconductor layer, and the second sub-layer 182 is a nitrogen polarized semiconductor layer. When the first sub-layer 181 is P-type doped, it can provide a large number of holes to the deep ultraviolet light-emitting diode 100, thereby improving the wall-insertion efficiency of the deep ultraviolet light-emitting diode 100. At the same time, the first sub-layer 181 also serves as a necessary condition for activating polarity conversion, so that a portion of the first sub-layer 181 is converted into the second sub-layer 182 after nitriding treatment. Since the surface of the nitrogen polarized semiconductor layer has more nitrogen dangling bonds, the second sub-layer 182 can improve its own doping efficiency, thereby reducing the contact resistance of the deep ultraviolet light-emitting diode 100 and further improving the wall-insertion efficiency of the deep ultraviolet light-emitting diode 100.

[0037] The technical solution of this application will now be described in conjunction with specific embodiments.

[0038] Please see Figure 1 , Figure 1 This is a schematic diagram of the structure of a deep ultraviolet light-emitting diode 100 provided in an embodiment of the present invention. The present invention provides a deep ultraviolet light-emitting diode 100, which includes a substrate 11, an intrinsic layer 12, an electron injection layer 13, a current spreading layer 14, a quantum well active layer 15, an electron blocking layer 16, a hole injection layer 17, and a composite ohmic contact layer 18 stacked from bottom to top.

[0039] The composite ohmic contact layer 18 includes a first sub-layer 181 and a second sub-layer 182 stacked from bottom to top. The first sub-layer 181 is a metal polar semiconductor layer, and the second sub-layer 182 is a nitrogen polar semiconductor layer.

[0040] In this embodiment of the invention, substrate 11 is a sapphire substrate. Sapphire substrates have many advantages: firstly, the production technology of sapphire substrates is mature, and the device quality is good; secondly, sapphire has excellent stability and can be used in high-temperature growth processes; finally, sapphire has high mechanical strength and is easy to handle and clean. Therefore, most processes generally use sapphire as a substrate.

[0041] In this embodiment of the invention, the intrinsic layer 12 includes a low-temperature buffer layer disposed on the substrate 11 and an aluminum nitride intrinsic layer disposed on the low-temperature buffer layer; wherein, the material of the low-temperature buffer layer is aluminum nitride, the growth temperature ranges from 400°C to 800°C, and the thickness ranges from 10nm to 50nm; the material of the aluminum nitride intrinsic layer is aluminum nitride, the growth temperature ranges from 1200°C to 1400°C, and the thickness ranges from 500nm to 4000nm.

[0042] Because the lattice mismatch between the substrate material (AL2O3) and the aluminum nitride material is large, a thin low-temperature buffer layer needs to be grown before the intrinsic layer is grown.

[0043] In this embodiment of the invention, the electron injection layer 13 is made of N-type doped aluminum gallium nitride material; wherein the aluminum content ranges from 20% to 90%, the thickness of the electron injection layer 13 ranges from 500 nm to 4000 nm, and the growth temperature of the electron injection layer 13 ranges from 800 °C to 1200 °C.

[0044] In this embodiment of the invention, the current spreading layer 14 is disposed on the electron injection layer 13, and the growth temperature range of the current spreading layer 14 is between 700°C and 1100°C.

[0045] Specifically, the material of the current spreading layer 14 is aluminum gallium nitride, the percentage of aluminum in the current spreading layer 14 is between 20% and 90%, and the thickness of the current spreading layer 14 is between 10 nm and 300 nm.

[0046] Furthermore, a stepped structure is formed between the current spreading layer 14 and the electron injection layer 13, and the area of ​​the electron injection layer 13 is larger than the area of ​​the current spreading layer 14.

[0047] In this embodiment of the invention, the quantum well active layer 15 is disposed on the current spreading layer 14, and the growth temperature of the quantum well active layer 15 is between 700°C and 1100°C; wherein, the quantum barrier and the quantum well in the quantum well active layer 15 are both made of aluminum gallium nitride, and the only difference between the quantum barrier and the quantum well is the content of aluminum component.

[0048] Specifically, the barrier thickness of the quantum well active layer 15 ranges from 1 nm to 30 nm, and the mass percentage of aluminum in the barrier ranges from 40% to 90%; the well thickness of the quantum well active layer 15 ranges from 0.1 to 5 nm, and the mass percentage of aluminum in the well ranges from 30% to 80%.

[0049] In this embodiment of the invention, an electron blocking layer 16 is disposed on the active layer 15 of the quantum well, and the growth temperature range of the electron blocking layer 16 is between 700°C and 1100°C; wherein, the electron blocking layer 16 is a single-layer aluminum gallium nitride structure, or, the electron blocking layer 16 is a superlattice structure formed by alternating third sublayers and fourth sublayers, wherein the third sublayers are made of Al a Ga 1-a Nitrogen (N) was used as the growth material, and Al was used for the fourth sublayer. b Ga 1-b N is used as the growth material, where 0 < a ≤ b < 1.

[0050] Among them, the electron blocking layer 16 is a P-type doped semiconductor material, which uses Mg as a dopant.

[0051] Furthermore, the mass percentage of aluminum component in the electron blocking layer 16 ranges from 50% to 100%, and the thickness of the electron blocking layer 16 ranges from 0.1 nm to 200 nm.

[0052] In this embodiment of the invention, a hole injection layer 17 is disposed on an electron blocking layer 16, and the growth temperature of the hole injection layer 17 is between 600°C and 1100°C. The hole injection layer 17 is made of p-type doped aluminum gallium nitride, the mass percentage of aluminum in the hole injection layer 17 is between 20% and 60%, the thickness of the hole injection layer 17 is between 0.1 nm and 50 nm, and magnesium is used as a dopant in the hole injection layer 17, with a doping concentration ranging from 1E18 cm⁻¹. -3 up to 5E20cm -3 between.

[0053] In this embodiment of the invention, the dopants for the first sublayer 181 and the second sublayer 182 are Si or Mg, with a doping concentration ranging from 1E18cm⁻¹. -3 Up to 1E21cm -3 between.

[0054] Specifically, when the doping concentration of the P-type dopant in the first sublayer 181 and the second sublayer 182 is less than 1E18cm -3 When the hole concentration in the composite ohmic contact layer 18 is relatively low, the ability of the composite ohmic contact layer 18 to attract electrons is relatively weak. When the doping concentration of the p-type dopant in the first sublayer 181 and the second sublayer 182 is greater than 1E21cm -3 When this happens, the composite ohmic contact layer 18 will have a large number of defects due to heavy doping, resulting in a self-compensation effect, which will reduce the doping concentration of P-type dopant in the composite ohmic contact layer 18.

[0055] When the doping concentration of N-type dopant in the first sublayer 181 and the second sublayer 182 is less than 1E18cm -3 When the electron concentration in the composite ohmic contact layer 18 is relatively low, the ability of the composite ohmic contact layer 18 to attract holes is relatively weak. When the doping concentration of the N-type dopant in the first sublayer 181 and the second sublayer 182 is greater than 1E21cm -3 When this happens, the composite ohmic contact layer 18 will have a large number of defects due to heavy doping, resulting in a self-compensation effect, which will reduce the doping concentration of P-type dopant in the composite ohmic contact layer 18.

[0056] In this embodiment of the invention, the material of the first sublayer 181 is silicon-doped aluminum gallium nitride with a metallic polar surface or magnesium-doped aluminum gallium nitride with a metallic polar surface; the mass percentage of aluminum component in the first sublayer 181 ranges from 0.1% to 100%, and the thickness of the first sublayer 181 ranges from 1 nm to 20 nm.

[0057] In this embodiment of the invention, the material of the second sublayer 182 is any one of uniform silicon-doped nitrogen-polarized aluminum gallium nitride, uniform magnesium-doped nitrogen-polarized aluminum gallium nitride, delta-type silicon-doped nitrogen-polarized aluminum gallium nitride, and delta-type magnesium-doped nitrogen-polarized aluminum gallium nitride; wherein the mass percentage of aluminum component in the second sublayer 182 ranges from 0.1% to 100%, and the thickness of the second sublayer 182 ranges from 0.1 nm to 10 nm.

[0058] Specifically, δ doping is a type of doping that differs from uniform doping. δ doping time is very short, and the deposition thickness is only a few nanometers, much smaller than other film layers. The main function of δ doping is to adjust the distribution of impurity concentration. Changes in the impurity distribution will affect the semiconductor energy band.

[0059] In this embodiment of the invention, when preparing a 20nm thick aluminum gallium nitride layer with a metallic polar surface, uniform doping refers to simultaneously introducing the gallium source, ammonia gas, and dopant into the reaction chamber; while δ doping is mainly pulse doping, which means that the dopant is not introduced when the gallium source and ammonia gas are introduced into the reaction chamber, and the doping is carried out by pulse; wherein, the gallium source can be stopped to introduce the dopant, or the gallium source can be stopped to introduce the dopant, and the pulse is required in the whole process.

[0060] Therefore, since δ-doping is easier to adjust the doping concentration distribution than uniform doping, δ-doping is also easier to dop with higher concentrations of dopant than uniform doping.

[0061] In this embodiment of the invention, the growth temperature of the first sublayer is T1, and the growth temperature of the second sublayer is T2; wherein, the relationship between T1 and T2 satisfies 400℃≤T1<T2≤900℃, and 20℃≤T2-T1≤100℃.

[0062] Specifically, the growth temperature of the first sublayer 181 is lower than that of the second sublayer 182 mainly because it is easier to dope with a higher concentration of dopant at a lower temperature to obtain more holes. Therefore, when the first sublayer 181 is P-type doped, it can provide a large number of holes to the deep ultraviolet light-emitting diode 100, thereby improving the wall-mounting efficiency of the deep ultraviolet light-emitting diode 100.

[0063] In this embodiment of the invention, the deep ultraviolet light-emitting diode 100 further includes an N-type electrode 110 and a P-type electrode 111;

[0064] The electron injection layer 13 and the current spreading layer 14 form a stepped structure, and the area of ​​the electron injection layer 13 is larger than the area of ​​the current spreading layer 14. The P-type electrode 111 is disposed on the composite ohmic contact layer 18, and the N-type electrode 110 is disposed at the stepped structure of the electron injection layer 13.

[0065] Unlike existing technologies, this invention provides a composite ohmic contact layer 18 on the side of the hole injection layer 17 away from the substrate 11. The composite ohmic contact layer 18 includes a first sub-layer 181 and a second sub-layer 182 stacked from bottom to top. The first sub-layer 181 is a metal polar semiconductor layer, and the second sub-layer 182 is a nitrogen polar semiconductor layer. When the first sub-layer 181 is P-type doped, it can provide a large number of holes to the deep ultraviolet light-emitting diode 100, thereby improving the wall-insertion efficiency of the deep ultraviolet light-emitting diode 100. At the same time, the first sub-layer 181 also serves as a necessary condition for activating polarity conversion, so that part of the first sub-layer 181 is converted into the second sub-layer 182 after nitriding treatment. Since the surface of the nitrogen polar semiconductor layer has more nitrogen dangling bonds, the second sub-layer 182 can improve its own doping efficiency, thereby reducing the contact resistance of the deep ultraviolet light-emitting diode 100 and further improving the wall-insertion efficiency of the deep ultraviolet light-emitting diode 100.

[0066] Accordingly, embodiments of the present invention also provide an epitaxial growth method for a deep ultraviolet light-emitting diode 100; please refer to [link to relevant documentation]. Figure 1 as well as Figure 2 , Figure 2 This is a process flow diagram of the epitaxial growth method for a deep ultraviolet light-emitting diode 100 provided in an embodiment of the present invention. Specifically, the epitaxial growth method includes:

[0067] S10, an intrinsic layer 12 is epitaxially grown on a substrate 11.

[0068] Specifically, S10 also includes:

[0069] First, a substrate 11 is provided, wherein the substrate 11 is a sapphire substrate 11. Then, a buffer layer is grown on the substrate 11 at a low temperature of 400℃ to 800℃, and the thickness of the buffer layer is between 10nm and 50nm. Finally, the growth temperature is raised to between 1200℃ and 1400℃, and an intrinsic aluminum nitride layer is grown on the buffer layer, the thickness of the intrinsic aluminum nitride layer being between 500nm and 4000nm. The buffer layer and the intrinsic aluminum nitride layer constitute the intrinsic layer 12, and both the buffer layer and the intrinsic aluminum nitride layer are made of aluminum nitride.

[0070] S20, an electron injection layer 13 is epitaxially grown on intrinsic layer 12.

[0071] Specifically, S20 also includes:

[0072] First, the growth temperature is lowered to between 800°C and 1200°C; then, an electron injection layer 13 is epitaxially grown on the intrinsic layer 12. The electron injection layer 13 is made of N-type doped aluminum gallium nitride; the aluminum content ranges from 20% to 90%, and the thickness of the electron injection layer 13 ranges from 500 nm to 4000 nm.

[0073] S30, an epitaxial current-expanding layer 14 is grown on the electron injection layer 13.

[0074] Specifically, S30 also includes:

[0075] First, the growth temperature is lowered to between 700°C and 1100°C, and a current spreading layer 14 is epitaxially grown on the electron injection layer 13. The material of the current spreading layer 14 is unintentionally doped aluminum gallium nitride, the mass percentage of aluminum in the current spreading layer 14 is between 20% and 90%, and the thickness of the current spreading layer 14 is between 10 nm and 300 nm.

[0076] S40, a quantum well active layer 15 is epitaxially grown on the current spreading layer 14.

[0077] Specifically, S40 also includes:

[0078] First, the growth temperature is maintained between 700℃ and 1100℃, and a quantum well active layer 15 is epitaxially grown on the current extension layer 14. The quantum barrier and the quantum well in the quantum well active layer 15 are both made of aluminum gallium nitride. The only difference between the quantum barrier and the quantum well is the content of aluminum.

[0079] Specifically, the barrier thickness of the quantum well active layer 15 ranges from 1 nm to 30 nm, and the mass percentage of aluminum in the barrier ranges from 40% to 90%; the well thickness of the quantum well active layer 15 ranges from 0.1 to 5 nm, and the mass percentage of aluminum in the well ranges from 30% to 80%.

[0080] S50, an electron blocking layer 16 is epitaxially grown on the active layer 15 of the quantum well.

[0081] Specifically, the S50 also includes:

[0082] First, the growth temperature is maintained between 700℃ and 1100℃ to epitaxially grow an electron blocking layer 16 on the quantum well active layer 15. The electron blocking layer 16 is a monolayer AlGaN structure, or it is a superlattice structure formed by alternating third and fourth sublayers, with the fifth sublayer being made of Al. a Ga 1-a Nitrogen (N) was used as the growth material, and Al was used for the sixth sublayer. b Ga 1-b N is used as the growth material, where 0 < a ≤ b < 1.

[0083] Among them, the electron blocking layer 16 is a P-type doped semiconductor material, which uses Mg as a dopant.

[0084] Furthermore, the mass percentage of aluminum component in the electron blocking layer 16 ranges from 50% to 100%, and the thickness of the electron blocking layer 16 ranges from 0.1 nm to 200 nm.

[0085] S60, a hole injection layer 17 is epitaxially grown on the electron blocking layer 16.

[0086] Specifically, the S60 also includes:

[0087] The growth temperature is lowered to between 600℃ and 1100℃, and a hole injection layer 17 is epitaxially grown on the electron blocking layer 16. The hole injection layer 17 is made of p-type doped aluminum gallium nitride, with an aluminum content ranging from 20% to 60%, a thickness ranging from 0.1 nm to 50 nm, and magnesium as a dopant with a doping concentration ranging from 1E18 cm⁻¹. -3 up to 5E20cm -3 between.

[0088] S70, a composite ohmic contact layer 18 is epitaxially grown on the hole injection layer 17.

[0089] Specifically, the S70 also includes:

[0090] First, the growth temperature is lowered to between 400°C and 900°C, and a first sublayer 181 is epitaxially grown on the hole injection layer 17. The thickness of the first sublayer 181 is between 1 nm and 20 nm. The material of the first sublayer 181 is silicon-doped aluminum gallium nitride with a metallic polar surface or magnesium-doped aluminum gallium nitride with a metallic polar surface. The mass percentage of aluminum in the first sublayer 181 is between 0.1% and 100%.

[0091] Afterwards, the MO source was stopped, ammonia and hydrogen were retained, and nitrogen was introduced. Then the temperature of the reaction chamber was raised to 800℃~1100℃, and part of the first sublayer 181 was nitrided. The nitriding reaction time was between 100s and 2000s.

[0092] Then, the growth temperature was raised to between 420°C and 900°C to obtain the second sublayer 182;

[0093] Next, an N-type electrode 110 is provided at the stepped structure of the electron injection layer 13, and the N-type electrode 110 is provided opposite to and spaced apart from the current spreading layer 14.

[0094] Finally, a P-type electrode 111 is formed on the composite ohmic contact layer 18.

[0095] In this embodiment of the invention, the MO source is a class of high-purity organometallic compounds, which mainly include any one of trimethylgallium, triethylgallium, trimethylaluminum, trimethylindium, and magnesium thiocene.

[0096] In this embodiment, the material of the second sublayer 182 is any one of uniform silicon-doped nitrogen-polarized aluminum gallium nitride, uniform magnesium-doped nitrogen-polarized aluminum gallium nitride, delta-type silicon-doped nitrogen-polarized aluminum gallium nitride, and delta-type magnesium-doped nitrogen-polarized aluminum gallium nitride; wherein the mass percentage of aluminum component in the second sublayer 182 ranges from 0.1% to 100%, and the thickness of the second sublayer 182 ranges from 0.1 nm to 10 nm.

[0097] Specifically, delta-type silicon doping is formed by stopping the introduction of aluminum and gallium sources during the growth of an aluminum gallium nitride layer on a nitrogen-polarized surface, retaining ammonia gas, and simultaneously introducing a silicon source. The silicon source introduction time is between 1 s and 500 s, the number of delta-type silicon doping cycles ranges from 1 to 10, and the interval between two adjacent delta-type silicon doping cycles ranges from 1 nm to 5 nm. Similarly, delta-type magnesium doping is formed by stopping the introduction of aluminum and gallium sources during the growth of an aluminum gallium nitride layer on a nitrogen-polarized surface, retaining ammonia gas, and simultaneously introducing a magnesium source. The magnesium source introduction time is between 1 s and 500 s, the number of delta-type magnesium doping cycles ranges from 1 to 10, and the interval between two adjacent delta-type magnesium doping cycles ranges from 1 nm to 5 nm.

[0098] In this embodiment of the invention, six different deep ultraviolet light-emitting diodes 100 were prepared according to the epitaxial growth method of the deep ultraviolet light-emitting diode 100 described above. After the deep ultraviolet light-emitting diode 100 devices were prepared, the operating voltage of each deep ultraviolet light-emitting diode 100 was tested under the action of a driving current of 40mA.

[0099] Furthermore, the film structures of the six different deep ultraviolet light-emitting diodes 100, from bottom to top, from the substrate 11 to the P-type electrode 111, are shown below:

[0100] Example 1:

[0101] The deep ultraviolet light-emitting diode 100 (deep ultraviolet LED 1) provided in the first embodiment of this application includes:

[0102] Substrate 11 is a sapphire substrate;

[0103] Intrinsic layer 12 is aluminum nitride with a thickness of 1000 nm;

[0104] The electron injection layer 13 is an N-type doped aluminum gallium nitride material, wherein the Al component in the electron injection layer 13 accounts for 50% of the mass percentage of the electron injection layer 13 and has a thickness of 1000 nm;

[0105] The current spreading layer 14 is made of unintentionally doped aluminum gallium nitride, wherein the mass percentage of aluminum in the current spreading layer 14 is 70%, and the thickness is 100 nm.

[0106] The active layer 15 of the quantum well has a quantum well thickness of 5 nm and an aluminum mass percentage of 50% in the quantum well, and a quantum barrier thickness of 2 nm and an aluminum mass percentage of 60% in the barrier.

[0107] The electron blocking layer 16 is a single-layer aluminum gallium nitride structure with a thickness of 10 nm and an aluminum composition of 60% by mass.

[0108] The hole injection layer 17 is made of P-type doped aluminum gallium nitride. The mass percentage of aluminum in the hole injection layer 17 is 40%, the thickness is 20 nm, and Mg is used as the dopant.

[0109] In the composite ohmic contact layer 18, the first sublayer 181 is made of silicon-doped aluminum gallium nitride with a metal polar surface and has a thickness of 2 nm, and the second sublayer 182 is made of uniformly silicon-doped nitrogen-doped aluminum gallium nitride with a nitrogen polar surface and has a thickness of 3 nm.

[0110] Example 2:

[0111] The deep ultraviolet light-emitting diode 100 (deep ultraviolet LED2) provided in the second embodiment of this application includes:

[0112] Substrate 11 is a sapphire substrate;

[0113] Intrinsic layer 12 is aluminum nitride with a thickness of 1000 nm;

[0114] The electron injection layer 13 is an N-type doped aluminum gallium nitride material, wherein the Al component in the electron injection layer 13 accounts for 50% of the mass percentage of the electron injection layer 13 and has a thickness of 1000 nm;

[0115] The current spreading layer 14 is made of unintentionally doped aluminum gallium nitride, wherein the mass percentage of aluminum in the current spreading layer 14 is 70%, and the thickness is 100 nm.

[0116] The active layer 15 of the quantum well has a quantum well thickness of 5 nm and an aluminum mass percentage of 50% in the quantum well, and a quantum barrier thickness of 2 nm and an aluminum mass percentage of 60% in the barrier.

[0117] The electron blocking layer 16 is a single-layer aluminum gallium nitride structure with a thickness of 10 nm and an aluminum composition of 60% by mass.

[0118] The hole injection layer 17 is made of P-type doped aluminum gallium nitride. The mass percentage of aluminum in the hole injection layer 17 is 40%, the thickness is 20 nm, and Mg is used as the dopant.

[0119] In the composite ohmic contact layer 18, the first sublayer 181 is made of silicon-doped metal polar surface aluminum gallium nitride material with a thickness of 2nm, and the second sublayer 182 is made of delta-type silicon-doped nitrogen polar surface aluminum gallium nitride material with a thickness of 3nm.

[0120] Example 3:

[0121] The deep ultraviolet light-emitting diode 100 (deep ultraviolet LED 3) provided in the third embodiment of this application includes:

[0122] Substrate 11 is a sapphire substrate;

[0123] Intrinsic layer 12 is aluminum nitride with a thickness of 1000 nm;

[0124] The electron injection layer 13 is an N-type doped aluminum gallium nitride material, wherein the Al component in the electron injection layer 13 accounts for 50% of the mass percentage of the electron injection layer 13 and has a thickness of 1000 nm;

[0125] The current spreading layer 14 is made of unintentionally doped aluminum gallium nitride, wherein the mass percentage of aluminum in the current spreading layer 14 is 70%, and the thickness is 100 nm.

[0126] The active layer 15 of the quantum well has a quantum well thickness of 5 nm and an aluminum mass percentage of 50% in the quantum well, and a quantum barrier thickness of 2 nm and an aluminum mass percentage of 60% in the barrier.

[0127] The electron blocking layer 16 is a single-layer aluminum gallium nitride structure with a thickness of 10 nm and an aluminum composition of 60% by mass.

[0128] The hole injection layer 17 is made of P-type doped aluminum gallium nitride. The mass percentage of aluminum in the hole injection layer 17 is 40%, the thickness is 20 nm, and Mg is used as the dopant.

[0129] In the composite ohmic contact layer 18, the first sublayer 181 is made of magnesium-doped aluminum gallium nitride with a polar surface and has a thickness of 2 nm, and the second sublayer 182 is made of uniformly magnesium-doped nitrogen-doped aluminum gallium nitride with a polar surface and has a thickness of 3 nm.

[0130] Example 4:

[0131] The deep ultraviolet light-emitting diode 100 (deep ultraviolet LED 4) provided in the fourth embodiment of this application includes:

[0132] Substrate 11 is a sapphire substrate;

[0133] Intrinsic layer 12 is aluminum nitride with a thickness of 1000 nm;

[0134] The electron injection layer 13 is an N-type doped aluminum gallium nitride material, wherein the Al component in the electron injection layer 13 accounts for 50% of the mass percentage of the electron injection layer 13 and has a thickness of 1000 nm;

[0135] The current spreading layer 14 is made of unintentionally doped aluminum gallium nitride, wherein the mass percentage of aluminum in the current spreading layer 14 is 70%, and the thickness is 100 nm.

[0136] The active layer 15 of the quantum well has a quantum well thickness of 5 nm and an aluminum mass percentage of 50% in the quantum well, and a quantum barrier thickness of 2 nm and an aluminum mass percentage of 60% in the barrier.

[0137] The electron blocking layer 16 is a single-layer aluminum gallium nitride structure with a thickness of 10 nm and an aluminum composition of 60% by mass.

[0138] The hole injection layer 17 is made of P-type doped aluminum gallium nitride. The mass percentage of aluminum in the hole injection layer 17 is 40%, the thickness is 20 nm, and Mg is used as the dopant.

[0139] In the composite ohmic contact layer 18, the first sublayer 181 is made of magnesium-doped aluminum gallium nitride with a metal polar surface and has a thickness of 2 nm, and the second sublayer 182 is made of delta-type magnesium-doped nitrogen-doped aluminum gallium nitride with a nitrogen polar surface and has a thickness of 3 nm.

[0140] Comparative Example 1:

[0141] This invention also provides a comparative embodiment 1, which compares the experimental results with those of the above embodiments. The structure of the deep ultraviolet light-emitting diode 100 (deep ultraviolet LED 5) provided in comparative embodiment 1 is the same as or similar to the structure of the deep ultraviolet light-emitting diode 100 provided in the embodiments of this invention, except that the material of the composite ohmic contact layer 18 is different. Specifically, the structure of the deep ultraviolet light-emitting diode 100 provided in comparative embodiment 1 includes:

[0142] Substrate 11 is a sapphire substrate;

[0143] Intrinsic layer 12 is aluminum nitride with a thickness of 1000 nm;

[0144] The electron injection layer 13 is an N-type doped aluminum gallium nitride material, wherein the Al component in the electron injection layer 13 accounts for 50% of the mass percentage of the electron injection layer 13 and has a thickness of 1000 nm;

[0145] The current spreading layer 14 is made of unintentionally doped aluminum gallium nitride, wherein the mass percentage of aluminum in the current spreading layer 14 is 70%, and the thickness is 100 nm.

[0146] The active layer 15 of the quantum well has a quantum well thickness of 5 nm and an aluminum mass percentage of 50% in the quantum well, and a quantum barrier thickness of 2 nm and an aluminum mass percentage of 60% in the barrier.

[0147] The electron blocking layer 16 is a single-layer aluminum gallium nitride structure with a thickness of 10 nm and an aluminum composition of 60% by mass.

[0148] The hole injection layer 17 is made of P-type doped aluminum gallium nitride. The mass percentage of aluminum in the hole injection layer 17 is 40%, the thickness is 20 nm, and Mg is used as the dopant.

[0149] The composite ohmic contact layer 18 is made of silicon-doped aluminum gallium nitride with a metal polar surface and a thickness of 5 nm.

[0150] Comparative Example 2:

[0151] The present invention also provides a comparative embodiment 2, which compares the experimental results with those of the above embodiments. The structure of the deep ultraviolet light-emitting diode 100 (deep ultraviolet LED 6) provided in comparative embodiment 2 is the same as or similar to the structure of the deep ultraviolet light-emitting diode 100 provided in the embodiments of the present invention, except that the material of the composite ohmic contact layer 18 is different. Specifically, the structure of the deep ultraviolet light-emitting diode 100 provided in comparative embodiment 2 includes:

[0152] Substrate 11 is a sapphire substrate;

[0153] Intrinsic layer 12 is aluminum nitride with a thickness of 1000 nm;

[0154] The electron injection layer 13 is an N-type doped aluminum gallium nitride material, wherein the Al component in the electron injection layer 13 accounts for 50% of the mass percentage of the electron injection layer 13 and has a thickness of 1000 nm;

[0155] The current spreading layer 14 is made of unintentionally doped aluminum gallium nitride, wherein the mass percentage of aluminum in the current spreading layer 14 is 70%, and the thickness is 100 nm.

[0156] The active layer 15 of the quantum well has a quantum well thickness of 5 nm and an aluminum mass percentage of 50% in the quantum well, and a quantum barrier thickness of 2 nm and an aluminum mass percentage of 60% in the barrier.

[0157] The electron blocking layer 16 is a single-layer aluminum gallium nitride structure with a thickness of 10 nm and an aluminum composition of 60% by mass.

[0158] The hole injection layer 17 is made of P-type doped aluminum gallium nitride. The mass percentage of aluminum in the hole injection layer 17 is 40%, the thickness is 20 nm, and Mg is used as the dopant.

[0159] The composite ohmic contact layer 18 is made of magnesium-doped aluminum gallium nitride with a thickness of 5 nm.

[0160] In the six deep ultraviolet light-emitting diodes 100 mentioned above, N-type electrodes 110 of the same material are all disposed on the electron injection layer 13 using conventional methods, and P-type electrodes 111 of the same material are all disposed on the composite ohmic contact layer 18 to form a complete epitaxial chip structure. Specific processes are not detailed here. Both the N-type electrode 110 and the P-type electrode 111 are multilayer composite metal materials. Finally, the operating voltages of the six deep ultraviolet light-emitting diodes at a driving current of 40mA were tested, and the experimental results are shown in Table 1.

[0161] sample Operating voltage (V) Example 1 5.9 Example 2 5.6 Example 3 5.8 Example 4 5.5 Comparative Example 1 6.2 Comparative Example 2 6.2

[0162] Table 1

[0163] As shown in Table 1 above, comparing Examples 1, 2, 3, and 4 with Comparative Examples 1 and 2, it can be seen that the deep ultraviolet light-emitting diode 100 containing nitrogen-polarized aluminum gallium nitride material in the composite ohmic contact layer 18 has a lower operating voltage than Comparative Examples 1 or 2.

[0164] Comparing Example 1 with Example 2, or Example 3 with Example 4, it can be seen that the deep ultraviolet light-emitting diode 100 containing delta-type doped aluminum gallium nitride material in the composite ohmic contact layer 18 has a lower operating voltage than the deep ultraviolet light-emitting diode 100 containing uniformly doped aluminum gallium nitride material in the composite ohmic contact layer 18. This is mainly because delta-type doping is easier to achieve a higher doping concentration than conventional uniform doping, thereby reducing the contact resistance between the composite ohmic contact layer 18 and the P-type electrode 111, and thus reducing the operating voltage of the deep ultraviolet light-emitting diode 100.

[0165] Comparing Example 1 with Example 3, or comparing Example 2 with Example 4, it can be seen that the deep ultraviolet light-emitting diode 100 prepared with magnesium-doped nitrogen-polarized aluminum gallium nitride material in the composite ohmic contact layer 18 has a lower operating voltage than the deep ultraviolet light-emitting diode 100 prepared with silicon-doped nitrogen-polarized aluminum gallium nitride material in the composite ohmic contact layer 18.

[0166] Therefore, the deep ultraviolet light-emitting diode 100 prepared in Embodiment 4 of the present invention has a lower operating voltage.

[0167] In summary, unlike existing technologies, this invention provides a composite ohmic contact layer 18 on the side of the hole injection layer 17 away from the substrate 11. The composite ohmic contact layer 18 includes a first sub-layer 181 and a second sub-layer 182 stacked from bottom to top. The first sub-layer 181 is a metal polar semiconductor layer, and the second sub-layer 182 is a nitrogen polar semiconductor layer. When the first sub-layer 181 is P-type doped, it can provide a large number of holes to the deep ultraviolet light-emitting diode 100, thereby improving the wall-insertion efficiency of the deep ultraviolet light-emitting diode 100. At the same time, the first sub-layer 181 also serves as a necessary condition for activating polarity conversion, so that a portion of the first sub-layer 181 is converted into the second sub-layer 182 after nitriding treatment. Since the surface of the nitrogen polar semiconductor layer has more nitrogen dangling bonds, the second sub-layer 182 can improve its own doping efficiency, thereby reducing the contact resistance of the deep ultraviolet light-emitting diode 100 and further improving the wall-insertion efficiency of the deep ultraviolet light-emitting diode 100.

[0168] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0169] The above embodiments merely illustrate implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A deep ultraviolet light emitting diode, comprising: The deep ultraviolet light emitting diode comprises a substrate, an intrinsic layer, an electron injection layer, a current spreading layer, a quantum well active layer, an electron blocking layer, a hole injection layer and a composite ohmic contact layer which are stacked from bottom to top. The composite ohmic contact layer comprises a first sub-layer and a second sub-layer which are stacked from bottom to top. The material of the first sub-layer is silicon-doped metal-polar surface aluminum gallium nitride material or magnesium-doped metal-polar surface aluminum gallium nitride material, the mass percentage of aluminum component in the first sub-layer ranges from 0.1% to 100%, and the thickness of the first sub-layer ranges from 1 nm to 20 nm.

2. The deep ultraviolet light emitting diode of claim 1, wherein, The growth temperature of the first sub-layer is T1, and the growth temperature of the second sub-layer is T2. The relationship between T1 and T2 satisfies 400℃≤T1 3. The deep ultraviolet light emitting diode of claim 1, wherein, The dopant of the first sub-layer and the second sub-layer is Si or Mg, and the doping concentration ranges from 1E18 cm -3 to 1E21 cm -3 .

4. The deep ultraviolet light emitting diode of claim 1, wherein, The deep ultraviolet light emitting diode further comprises an N-type electrode and a P-type electrode. The step of epitaxially growing the composite ohmic contact layer on the hole injection layer further comprises:

5. An epitaxial growth method for a deep ultraviolet light-emitting diode, characterized in that, The method comprises: epitaxially growing an intrinsic layer on a substrate; epitaxially growing an electron injection layer on the intrinsic layer; epitaxially growing a current spreading layer on the electron injection layer; epitaxially growing a quantum well active layer on the current spreading layer; epitaxially growing an electron blocking layer on the quantum well active layer; epitaxially growing a hole injection layer on the electron blocking layer; epitaxially growing a composite ohmic contact layer on the hole injection layer; The material of the first sub-layer is silicon-doped metal-polar surface aluminum gallium nitride material or magnesium-doped metal-polar surface aluminum gallium nitride material, the mass percentage of aluminum component in the first sub-layer ranges from 0.1% to 100%, and the thickness of the first sub-layer ranges from 1 nm to 20 nm.

6. The method of claim 5, wherein the DUV LED is grown by metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). The growth temperature of the first sub-layer is T1, and the growth temperature of the second sub-layer is T2. The relationship between T1 and T2 satisfies 400℃≤T1 The deep ultraviolet light emitting diode further comprises an N-type electrode and a P-type electrode. The step of epitaxially growing the composite ohmic contact layer on the hole injection layer further comprises: After the growth of the first sub-layer is completed, the MO source is stopped, ammonia and hydrogen are retained, and nitrogen is introduced; After the temperature of the reaction cavity is adjusted to between 800-1100℃, the first sub-layer is subjected to a nitridation treatment to obtain the second sub-layer.

7. The method of claim 6, wherein the method further comprises: The second sub-layer is a δ-type silicon-doped or δ-type magnesium-doped nitrogen-polar aluminum gallium nitride material; The doping number of the δ-type silicon doping or the δ-type magnesium doping ranges from 1 to 10, and the interval between two adjacent δ-type silicon dopings or two adjacent δ-type magnesium dopings ranges from 1 nm to 5 nm.

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