Deep ultraviolet led with modulation doped multiple quantum well structure and method of fabrication

Abstract

This invention discloses a deep ultraviolet LED with a modulation-doped multiple quantum well structure and its fabrication method. The deep ultraviolet LED comprises a sapphire substrate, an intrinsic AlN layer, an N-type AlGaN layer, a current spreading layer, a modulation-doped multiple quantum well layer, an electron blocking layer, a P-type AlGaN injection layer, and a P-type GaN contact layer, which are sequentially stacked. On the one hand, this invention prevents Si diffusion into the quantum well layer by placing undoped material near the quantum well layer in the modulation quantum barrier layer; on the other hand, the doping concentration of the doped quantum barrier layer in the modulation-doped multiple quantum well layer gradually decreases along the direction from the N-type AlGaN layer to the P-type AlGaN injection layer, thereby limiting electron overflow, enhancing hole migration to neighboring quantum wells, improving carrier injection efficiency, and thus improving the luminous efficiency of the deep ultraviolet LED device.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optoelectronics, and in particular to a deep ultraviolet LED with a modulation-doped multi-quantum-well structure and its fabrication method. Background Technology

[0002] Group III nitrides, as outstanding representatives of wide-bandgap semiconductor materials, have enabled the development of highly efficient solid-state light source devices such as blue-green light-emitting diodes (LEDs) and lasers, achieving great success in applications such as flat panel displays and white light illumination. In the past decade, there has been a desire to apply these highly efficient luminescent materials to the ultraviolet (UV) band to meet the growing demand for UV light sources. The UV band is generally classified according to its biological effects into: long-wave UV, medium-wave UV, short-wave UV, and vacuum UV. x Ga 1-x The bandgap of nitrogen-based materials can be continuously tunable from 3.4 eV (GaN) to 6.2 eV (AlN) by changing the Al composition, enabling emission from 365 nm to 200 nm in the spectral range. The band-edge emission wavelength of GaN is approximately 360 nm, commonly used as a demarcation marker for the emission band of nitride ultraviolet (UV) LEDs. UV-LEDs with emission wavelengths greater than 360 nm employ GaN / InGaN quantum well (QWs) structures in their active regions, similar to those used in blue LEDs. Research on this began as early as the 1990s, and the technology has been successfully commercialized, achieving an external quantum efficiency (EQE) exceeding 40%, comparable to blue LEDs. In contrast, UV-LEDs with emission wavelengths less than 360 nm primarily use AlGaN quantum well structures as their active regions, and their quantum efficiency is far less satisfactory.

[0003] Currently, the low quantum efficiency in deep ultraviolet LEDs stems partly from the different migration capabilities of electrons and holes within the device. Electrons have a higher migration capability, while holes have a lower one; therefore, electrons often bypass the electron barrier layer to enter the p-type region, causing electron overflow. On the other hand, the quantum barriers in multi-quantum-well layers require Si doping, while the quantum wells themselves cannot be doped. However, since the quantum barrier and quantum well layers are grown continuously, during the actual growth process, Si doped in the quantum barriers often diffuses into the quantum wells. This diffused Si forms defects in the quantum wells, thus reducing the device's luminous efficiency. Therefore, a new ultraviolet LED solution is needed to address the problems existing in the current technology. Summary of the Invention

[0004] The purpose of this invention is to provide a deep ultraviolet LED with a modulation-doped multi-quantum-well structure and its fabrication method, which solves the problem of low efficiency of deep ultraviolet LEDs caused by Si diffusion into quantum wells in the quantum barrier in the prior art.

[0005] To solve the above-mentioned technical problems, the first solution provided by the present invention is: a deep ultraviolet LED with a modulation-doped multiple quantum well structure, comprising a sapphire substrate, an intrinsic AlN layer, an N-type AlGaN layer, a current spreading layer, a modulation-doped multiple quantum well layer, an electron blocking layer, a P-type AlGaN injection layer, and a P-type GaN contact layer stacked sequentially; the modulation-doped multiple quantum well layer is composed of several modulation quantum barrier layers and quantum well layers arranged in a periodic alternation, each modulation quantum barrier layer comprising a first undoped quantum barrier layer, a doped quantum barrier layer, and a second undoped quantum barrier layer, wherein the first undoped quantum barrier layer and the second undoped quantum barrier layer are disposed adjacent to the quantum well layer, and the quantum barrier doped layer is disposed between the first undoped quantum barrier layer and the second undoped quantum barrier layer.

[0006] Preferably, the first and second quantum barrier undoped layers are undoped Al. x Ga 1-x The N-layer, with a quantum barrier doped layer of Si-doped Al, has a quantum barrier doped layer. x Ga 1-x The N-layer has an Al composition percentage (x) of 40%–100%; the quantum well layer is undoped Al. y Ga 1-y N, in which the percentage of Al component y is 20%–90%.

[0007] Preferably, along the direction from the N-type AlGaN layer to the P-type AlGaN implantation layer, the doping concentration of the (n+1)th quantum barrier doped layer is less than the doping concentration of the nth quantum barrier doped layer, where n is an integer from 2 to 30; the doping concentration of the quantum barrier doped layer is 1 × 10⁻⁶. 16 ~1×10 22 cm -3 .

[0008] Preferably, the thickness of the modulation quantum barrier layer is h, the thickness of the first undoped quantum barrier layer is a0, the thickness of the doped quantum barrier layer is b, and the thickness of the second undoped quantum barrier layer is a1, satisfying the following relationship: 0.1nm ≤ h=a0+b+a1≤50nm and 0.1nm ≤ a0=a1≤5nm. The thickness of the quantum well layer is 0.1nm~5nm.

[0009] Preferably, the dopant used in the P-type AlGaN implantation layer and the P-type GaN contact layer is Mg.

[0010] To solve the above-mentioned technical problems, the second solution provided by the present invention is: a method for preparing a deep ultraviolet LED with a modulation-doped multi-quantum-well structure, characterized in that the method for preparing a deep ultraviolet LED with a modulation-doped multi-quantum-well structure is prepared by metal-organic chemical vapor deposition as described in the first solution.

[0011] The method for fabricating a deep ultraviolet LED with a modulation-doped multi-quantum-well structure includes the following steps: S1, growing a buffer layer of AlN intrinsic layer with a thickness of 10-50 nm on a sapphire substrate at 400-800℃, then heating to 1200-1400℃ to grow an AlN intrinsic layer on the buffer layer of the AlN intrinsic layer, with a total thickness of 500-4000 nm; S2, cooling to 800-1200℃ to grow an n-type AlGaN layer on the AlN intrinsic layer, wherein the Al composition percentage is 20-90% and the thickness is 500-4000 nm; S3, cooling to 700-1100℃ to grow a current spreading layer on one side of the n-type AlGaN layer; S4, at 100℃... At temperatures ranging from 0 to 1200°C, a modulation quantum barrier layer and a quantum well layer are periodically and alternately grown on the current spreading layer to form a modulation-doped multi-quantum-well layer; at temperatures ranging from 700 to 1100°C, an electron blocking layer with a thickness of 1 to 50 nm and an Al composition percentage of 30 to 100% is grown on the modulation-doped multi-quantum-well layer; at temperatures ranging from 700 to 1100°C, a p-type AlGaN implantation layer with an Al composition percentage of 10% to 100% and a thickness of 1 to 50 nm is grown on the electron blocking layer, and Mg is used as the p-type dopant; at temperatures ranging from 400 to 900°C, a p-type GaN contact layer with a thickness of 1 to 20 nm is grown on the p-type AlGaN implantation layer, and Mg is used as the p-type dopant.

[0012] The specific steps of step S4 are as follows: S41, under conditions of 1000-1200℃, a first undoped quantum barrier layer, a doped quantum barrier layer, and a second undoped quantum barrier layer are grown sequentially, with an interval T0 set between the growth of adjacent layers, to form a modulated quantum barrier layer. The Al composition percentage x of the modulated quantum barrier layer is 40%-100%, and the thickness is 0.1nm-50nm; S42, under conditions of 1000-1200℃, a quantum well layer is grown on the modulated quantum barrier layer. The Al composition percentage y of the quantum well layer is 20%-90%, and the thickness is 0.1nm-5nm; S43, steps S41 and S42 are repeated several times to form a modulated doped multi-quantum well layer by periodically alternating several modulated quantum barrier layers and quantum well layers, wherein the doping concentration of several quantum barrier doped layers gradually decreases.

[0013] Preferably, in step S41, during the interval, the organic source is stopped while ammonia is continued to flow, with a duration of 0.1s ≤ t0 ≤ 10s.

[0014] Preferably, the growth temperature of the quantum barrier doped layer is T1, the growth temperature of the first and second undoped quantum barrier layers is T2, and the growth temperature of the quantum well layer is T3, satisfying the following relationship: 1200℃≥T1≥T2=T3≥1000℃; wherein, when T1=T2, the thickness of the first undoped quantum barrier layer is a0, and the thickness of the second undoped quantum barrier layer is a1; when T1>T2, the thickness of the first undoped quantum barrier layer is a0+(T1-T2)*f, the thickness of the second undoped quantum barrier layer is a1+(T1-T2)*f, and 0.1≤f≤10, where f is in nm / ℃.

[0015] The beneficial effects of this invention are as follows: Unlike the prior art, this invention provides a deep ultraviolet LED with a modulation-doped multi-quantum-well structure and its fabrication method. On the one hand, by setting undoped material near the quantum well layer in the modulation quantum barrier layer, Si diffusion into the quantum well layer is prevented. On the other hand, along the direction from the N-type AlGaN layer to the P-type AlGaN injection layer, the doping concentration of the doped quantum barrier layer in the modulation-doped multi-quantum-well layer gradually decreases, thereby limiting electron overflow, enhancing hole migration to the nearest-neighbor quantum well, improving carrier injection efficiency, and thus improving the luminous efficiency of the deep ultraviolet LED device. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of one embodiment of the deep ultraviolet LED with a modulation-doped multiple quantum well structure in this invention;

[0017] Figure 2 This is a schematic diagram of the modulation-doped multiple quantum well structure of the deep ultraviolet LED with modulation-doped multiple quantum well structure in this invention;

[0018] Figure 3 This is a comparison diagram of the light output power of the deep ultraviolet LED in Embodiment 1 of this invention and the comparison documents 1 to 3. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] For the first solution proposed in this invention, please refer to Figure 1 and Figure 2 , Figure 1 This is a schematic diagram of one embodiment of the deep ultraviolet LED with a modulation-doped multiple quantum well structure according to the present invention. Figure 2 This is a schematic diagram of the modulation-doped multiple quantum well structure of the deep ultraviolet LED with modulation-doped multiple quantum well structure according to the present invention. The deep ultraviolet LED with modulation-doped multiple quantum well structure according to the present invention includes a sapphire substrate, an intrinsic AlN layer, an N-type AlGaN layer, a current spreading layer, a modulation-doped multiple quantum well layer, an electron blocking layer, a P-type AlGaN injection layer, and a P-type GaN contact layer stacked sequentially. The modulation-doped multiple quantum well layer is composed of several modulation quantum barrier layers and quantum well layers arranged in a periodic alternation. Each modulation quantum barrier layer includes a first undoped quantum barrier layer, a doped quantum barrier layer, and a second undoped quantum barrier layer in sequence. The first undoped quantum barrier layer and the second undoped quantum barrier layer are adjacent to the quantum well layer, and the quantum barrier doped layer is disposed between the first undoped quantum barrier layer and the second undoped quantum barrier layer.

[0021] In this embodiment, the first and second quantum barrier undoped layers are undoped Al. x Ga 1-x The N-layer, with a quantum barrier doped layer of Si-doped Al, has a quantum barrier doped layer. x Ga 1-x The N-layer has an Al composition percentage (x) of 40%–100%; the quantum well layer is undoped Al. y Ga 1-y N, wherein the Al component percentage y is 20%–90%. Along the direction from the N-type AlGaN layer to the P-type AlGaN implantation layer, the doping concentration of the (n+1)th quantum barrier doped layer is less than that of the nth quantum barrier doped layer, where n is an integer from 2 to 30. That is, during the fabrication process, the doping concentration of the quantum barrier doped layers in several cycles gradually decreases from bottom to top; specifically, the preferred doping concentration of the quantum barrier doped layer is 1 × 10⁻⁶. 16 ~1×10 22 cm -3 .

[0022] Regarding the thickness settings, the thickness of the modulation quantum barrier layer is h, the thickness of the first undoped quantum barrier layer is a0, the thickness of the doped quantum barrier layer is b, and the thickness of the second undoped quantum barrier layer is a1, satisfying the following relationship: 0.1nm≤h=a0+b+a1≤50nm and 0.1nm≤a0=a1≤5nm.

[0023] The second solution proposed in this application is a method for fabricating a deep ultraviolet LED with a modulation-doped multi-quantum-well structure. This method uses metal-organic chemical vapor deposition to fabricate the deep ultraviolet LED with the modulation-doped multi-quantum-well structure described in the first solution above. The specific steps are as follows:

[0024] S1. At 400–800°C, a buffer layer with a thickness of 10–50 nm is grown on a sapphire substrate in the AlN intrinsic layer. Then, the temperature is raised to 1200–1400°C to grow an AlN intrinsic layer on the buffer layer in the AlN intrinsic layer. The total thickness of the AlN intrinsic layer is 500–4000 nm.

[0025] S2, cooling to 800–1200℃, an n-type AlGaN layer is grown on the intrinsic AlN layer, wherein the Al component percentage is 20–90% and the thickness is 500–4000 nm.

[0026] S3, cool down to 700-1100℃, and grow a current-spreading layer on one side of the n-type AlGaN layer.

[0027] S4. At 1000–1200℃, modulation quantum barrier layers and quantum well layers are periodically and alternately grown on the current spreading layer to form a modulation-doped multi-quantum-well layer. The specific steps in this process are as follows:

[0028] S41, under conditions of 1000–1200℃, a first quantum barrier undoped layer, a quantum barrier doped layer, and a second quantum barrier undoped layer are grown sequentially, with an interval t0 set between the growth of adjacent layers, forming a modulated quantum barrier layer. The Al composition percentage x of the modulated quantum barrier layer is 40%–100%, and the thickness is 0.1 nm–50 nm. In this step, during the interval time, the organic source is stopped while ammonia gas is continuously introduced, 0.1 s ≤ t0 ≤ 10 s.

[0029] S42, under conditions of 1000–1200℃, a quantum well layer is further grown on the modulated quantum barrier layer. The Al composition percentage y of the quantum well layer is 20%–90%, and the thickness is 0.1 nm–5 nm. The growth temperature of the quantum barrier doped layer is T1, the growth temperature of the first and second undoped quantum barrier layers is T2, and the growth temperature of the quantum well layer is T3, satisfying the following relationship: 1200℃ ≥ T1 ≥ T2 = T3 ≥ 1000℃; where, when T1 = T2, the thickness of the first undoped quantum barrier layer is a0, and the thickness of the second undoped quantum barrier layer is a1; when T1 ≥ T2, the thickness of the first undoped quantum barrier layer is a0 + (T1 - T2) * f, the thickness of the second undoped quantum barrier layer is a1 + (T1 - T2) * f, and 0.1 ≤ f ≤ 10, where f is in nm / ℃; using the above settings… The reason for this arrangement is that there are two different situations when growing doped and undoped layers: the same temperature and different temperatures. When the two growth temperatures are different, i.e., T1>T2, a temperature change operation is required between the two deposition processes. During the temperature change, except for stopping the supply of organic source gas, other gas sources are still supplied. During this process, hydrogen will continuously corrode the deposited epitaxial layer. The greater the temperature difference and the longer the temperature change time, the greater the degree of corrosion, and the thinner the epitaxial layer will become. Therefore, it is necessary to appropriately increase the thickness of the undoped layer to offset the corrosion loss during the temperature change process, and the thickness increase is proportional to the temperature difference.

[0030] S43, repeat steps S41 and S42 several times to form a modulation-doped multi-quantum-well layer by periodically alternating several modulation quantum barrier layers and quantum well layers, wherein the doping concentration of several quantum barrier doped layers gradually decreases.

[0031] S5, an electron blocking layer with a thickness of 1-50 nm and an Al composition percentage of 30-100% is grown on a modulation-doped multi-quantum-well layer at 700-1100℃.

[0032] S6, a p-type AlGaN implantation layer is grown on the electron blocking layer at 700-1100℃, with an Al composition percentage of 10%-100% and a thickness of 1-50nm, and Mg is used as the p-type dopant.

[0033] S7, under conditions of 400–900℃, grows a p-type GaN contact layer on a p-type AlGaN implantation layer with a thickness of 1–20 nm, and uses Mg as a p-type dopant.

[0034] Since the deep ultraviolet LED fabrication method with modulation-doped multiple quantum well structure in the second solution is used to fabricate the deep ultraviolet LED with modulation-doped multiple quantum well structure in the first solution, the structure and function of the deep ultraviolet LED with modulation-doped multiple quantum well structure in the two solutions should be consistent.

[0035] The effects are illustrated below through specific embodiments and comparative experiments.

[0036] Example 1

[0037] The specific fabrication steps of the deep ultraviolet LED with a modulation-doped multi-quantum-well structure in this embodiment are as follows:

[0038] (1) At 700℃, a buffer layer with a thickness of 20nm was grown on the sapphire substrate in the AlN intrinsic layer. Then the temperature was raised to 1200℃ and an AlN intrinsic layer was grown on the buffer layer in the AlN intrinsic layer. The total thickness of the AlN intrinsic layer was 1000nm.

[0039] (2) Cool down to 1000℃ and grow an n-type AlGaN layer on the intrinsic AlN layer, wherein the Al component percentage is 50% and the thickness is 1500nm.

[0040] (3) Cool down to 900℃ and grow a current-extending layer on one side of the n-type AlGaN layer.

[0041] (4) At 1100℃, a first undoped quantum barrier layer, a doped quantum barrier layer, and a second undoped quantum barrier layer are grown sequentially, with an interval T0 = 5s between adjacent layers, forming a modulated quantum barrier layer. The Al composition percentage x of the modulated quantum barrier layer is 65%, and the thickness of the quantum barrier doped layer is 8nm. The thicknesses of the first and second undoped quantum barrier layers are both 1.5nm. Then, the reaction temperature is adjusted to 1090℃, with a temperature change time of 1.5min, and a quantum well layer is grown on the modulated quantum barrier layer. The Al composition percentage y of the quantum well layer is 55%, and the thickness is 3nm. After repeating the growth for 5 cycles, a modulated doped multi-quantum well layer is formed by the alternating arrangement of the modulated quantum barrier layer and the quantum well layer. The Si doping concentration of the five quantum barrier doped layers gradually decreases according to the order of growth, specifically from 1×10⁻⁶. 21 Gradually reduce to 1×10 17 .

[0042] (5) An electron blocking layer with a thickness of 20 nm and an Al content of 60% was grown on a modulation-doped multi-quantum-well layer at 1000 °C.

[0043] (6) A p-type AlGaN implantation layer was grown on the electron blocking layer at 1000℃, with an Al composition percentage of 55% and a thickness of 35nm, and Mg was used as the p-type dopant.

[0044] (7) A p-type GaN contact layer with a thickness of 10 nm was grown on the p-type AlGaN implantation layer at 800 °C, and Mg was used as the p-type dopant.

[0045] Comparative Example 1

[0046] This comparative example is based on the preparation steps of Example 1, except that step (4) is replaced with: (4) at 1100°C, only a quantum barrier doped layer is grown, with an Al composition percentage x of 65% and a thickness of 8 nm. Then, the reaction temperature is adjusted to 1090°C for a temperature change time of 1.5 min, and a quantum well layer is grown on the quantum barrier doped layer, with an Al composition percentage y of 55% and a thickness of 3 nm. After repeating the growth for 5 cycles, a modulation doped multi-quantum well layer is formed by the periodic alternation of modulation quantum barrier layers and quantum well layers, wherein the Si doping concentration of the 5 quantum barrier doped layers is 1×10⁻⁶. 19 The only difference between this comparative example and Example 1 is that no first and second undoped quantum barrier layers are provided, and the doping concentration of the multiple quantum barrier doped layers is the same. The other steps are the same as in Example 1.

[0047] Comparative Example 2

[0048] This comparative example is based on the preparation steps of Example 1, except that step (4) is replaced with: (4) at 1100°C, only a quantum barrier doped layer is grown, with an Al composition percentage x of 65% and a thickness of 8 nm. Then, the reaction temperature is adjusted to 1090°C for 1.5 min, and a quantum well layer is grown on the quantum barrier doped layer, with an Al composition percentage y of 55% and a thickness of 3 nm. After repeating the growth for 5 cycles, a modulation doped multi-quantum well layer is formed by the alternating arrangement of the modulation quantum barrier layer and the quantum well layer. The Si doping concentration of the 5 quantum barrier doped layers gradually decreases according to the order of growth, specifically from 1×10 21 Gradually reduce to 1×10 17 The only difference between this comparative example and Example 1 is that the first and second undoped quantum barriers are not provided; the other steps are the same as in Example 1.

[0049] Comparative Example 3

[0050] This comparative example is based on the preparation steps of Example 1, except that step (4) is replaced with: (4) at 1100°C, a first undoped quantum barrier layer, a doped quantum barrier layer, and a second undoped quantum barrier layer are grown sequentially, with an interval of T0 = 5s between adjacent layers, to form a modulated quantum barrier layer. The Al composition percentage x of the modulated quantum barrier layer is 65%, wherein the thickness of the quantum barrier doped layer is 8nm, and the thickness of both the first and second undoped quantum barrier layers is 1.5nm. Then, the reaction temperature is adjusted to 1090°C, and the temperature change time is 1.5min, and a quantum well layer is grown on the modulated quantum barrier layer. The Al composition percentage y of the quantum well layer is 55%, and the thickness is 3nm. After repeating the growth for 5 cycles, a modulated doped multi-quantum well layer is formed by the periodic alternation of the modulated quantum barrier layer and the quantum well layer, wherein the Si doping concentration of the 5 quantum barrier doped layers is 1×10 19 The only difference between this comparative example and Example 1 is that the doping concentration of the multiple quantum barrier doped layers is the same, rather than gradually decreasing; the other steps are the same as in Example 1.

[0051] Comparing Example 1 and Comparative Examples 1-3 above, Example 1 is a deep ultraviolet LED with an undoped quantum barrier layer and a modulation doped multi-quantum well layer with successively decreasing doping concentrations, while Comparative Example 1 is a deep ultraviolet LED with a conventional structure, Comparative Example 2 is a deep ultraviolet LED with only a modulation doped multi-quantum well layer with successively decreasing doping concentrations, and Comparative Example 3 is a deep ultraviolet LED with only an undoped quantum barrier layer. Specific test results are as follows: Figure 3 As shown. By Figure 3 It can be seen that the light output power of Example 1 is significantly improved compared with Comparative Example 1, and is also more advantageous than Comparative Examples 2-3. This indicates that the design method of successively decreasing doping concentration of undoped quantum barrier layer and modulation doped multi-quantum well layer can achieve better deep ultraviolet light output effect. The mechanism by which Example 1 achieves better light emission is as follows: On the one hand, by setting undoped first and second quantum barrier layers near the quantum well, Si diffusion into the quantum well layer can be blocked, thereby preventing Si from entering the quantum well and forming defects, avoiding the influence of diffusion defects on the light emission of the device, and thus improving the light emission effect of the device. On the other hand, since the electron migration rate is much higher than the hole migration rate, the doping concentration of several quantum barrier doped layers gradually decreases along the direction from the N-type AlGaN layer to the P-type AlGaN injection layer. The doping concentration of the quantum barrier doped layer near the N-type AlGaN layer is higher, thereby limiting electron overflow. At the same time, the doping concentration of the quantum barrier doped layer near the P-type AlGaN injection layer is lower, promoting the migration of holes to the neighboring quantum well layer, making the migration rates of holes and electrons more closely match, improving the carrier injection efficiency, and ultimately achieving a further improvement in the light emission effect of the device.

[0052] Unlike existing technologies, this invention provides a deep ultraviolet LED with a modulation-doped multi-quantum-well structure and its fabrication method. On the one hand, by placing undoped elements near the quantum well layer in the modulation quantum barrier layer, Si diffusion into the quantum well layer is prevented. On the other hand, along the direction from the N-type AlGaN layer to the P-type AlGaN injection layer, the doping concentration of the doped quantum barrier layer in the modulation-doped multi-quantum-well layer gradually decreases, thereby limiting electron overflow, enhancing hole migration to neighboring quantum wells, improving carrier injection efficiency, and thus improving the luminous efficiency of the deep ultraviolet LED device.

[0053] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are 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 LED with a modulation-doped multi-quantum-well structure, characterized in that, It includes a sapphire substrate, an intrinsic AlN layer, an N-type AlGaN layer, a current spreading layer, a modulation-doped multiple quantum well layer, an electron blocking layer, a P-type AlGaN implantation layer, and a P-type GaN contact layer stacked sequentially. The modulation-doped multiple quantum well layer is composed of several modulation quantum barrier layers and quantum well layers arranged in a periodic alternation. Each modulation quantum barrier layer includes a first undoped quantum barrier layer, a doped quantum barrier layer and a second undoped quantum barrier layer in sequence. The first undoped quantum barrier layer and the second undoped quantum barrier layer are disposed adjacent to the quantum well layer, and the doped quantum barrier layer is disposed between the first undoped quantum barrier layer and the second undoped quantum barrier layer. The first and second quantum barrier undoped layers are undoped Al. x Ga 1-x N-layer, the quantum barrier doped layer is Si-doped Al x Ga 1-x N layers, in which the percentage of Al component x is 40%~100%; The quantum well layer is undoped Al. y Ga 1-y N, in which the percentage of Al component y is 20%~90%; Along the direction from the N-type AlGaN layer to the P-type AlGaN implantation layer, the doping concentration of the (n+1)th quantum barrier doped layer is less than the doping concentration of the nth quantum barrier doped layer, where n is an integer from 2 to 30; The doping concentration of the quantum barrier doped layer is 1×10⁻⁶. 16 ~1×10 22 cm -3 .

2. The deep ultraviolet LED with a modulation-doped multi-quantum-well structure according to claim 1, characterized in that, The thickness of the modulated quantum barrier layer is h, the thickness of the first undoped quantum barrier layer is a0, the thickness of the doped quantum barrier layer is b, and the thickness of the second undoped quantum barrier layer is a1, satisfying the following relationship: 0.1 nm ≤ h = a0 + b + a1 ≤ 50 nm and 0.1 nm ≤ a0 = a1 ≤ 5 nm.

3. The deep ultraviolet LED with a modulation-doped multi-quantum-well structure according to claim 1, characterized in that, The dopant used in the P-type AlGaN implantation layer and the P-type GaN contact layer is Mg.

4. A method for fabricating a deep ultraviolet LED with a modulation-doped multi-quantum-well structure, characterized in that, The method for preparing deep ultraviolet LEDs with modulation-doped multiple quantum well structures described herein employs metal-organic chemical vapor deposition to prepare any one of the deep ultraviolet LEDs with modulation-doped multiple quantum well structures described in claims 1 to 3.

5. The method for fabricating a deep ultraviolet LED with a modulation-doped multi-quantum-well structure according to claim 4, characterized in that step... include: S1, under conditions of 400~800℃, a buffer layer in the AlN intrinsic layer is grown on a sapphire substrate with a thickness of 10~50nm, and then the temperature is raised to 1200~1400℃ to grow an AlN intrinsic layer on the buffer layer in the AlN intrinsic layer, the total thickness of the AlN intrinsic layer being 500~4000nm. S2, cool down to 800~1200℃, and grow an n-type AlGaN layer on the intrinsic AlN layer, wherein the Al component percentage is 20~90% and the thickness is 500~4000nm; S3, cool down to 700~1100℃, and grow a current extension layer on one side of the n-type AlGaN layer; S4. At 1000~1200℃, a modulation quantum barrier layer and a quantum well layer are periodically and alternately grown on the current extension layer to form a modulation-doped multi-quantum-well layer. S5. An electron blocking layer with a thickness of 1-50 nm and an Al composition percentage of 30-100% is grown on the modulation-doped multiple quantum well layer at 700-1100℃. S6. Under conditions of 700~1100℃, a p-type AlGaN implantation layer is grown on the electron blocking layer, with an Al composition percentage of 10%~100% and a thickness of 1~50nm, and Mg is used as a p-type dopant. S7. Under conditions of 400~900℃, a p-type GaN contact layer with a thickness of 1~20nm is grown on the p-type AlGaN implantation layer, and Mg is used as the p-type dopant.

6. The method for fabricating a deep ultraviolet LED with a modulation-doped multi-quantum-well structure according to claim 5, characterized in that, The specific steps of step S4 are as follows: S41, under conditions of 1000~1200℃, a first quantum barrier undoped layer, a quantum barrier doped layer, and a second quantum barrier undoped layer are grown sequentially, with an interval time t0 set between the growth of adjacent film layers to form a modulated quantum barrier layer, wherein the Al composition percentage x of the modulated quantum barrier layer is 40%~100% and the thickness is 0.1 nm~50 nm. S42, under conditions of 1000~1200℃, a quantum well layer is further grown on the modulation quantum barrier layer, wherein the Al composition percentage y of the quantum well layer is 20%~90% and the thickness is 0.1 nm~5 nm; S43, repeat steps S41 and S42 several times, forming the modulation-doped multi-quantum-well layer by periodically alternating several modulation quantum barrier layers and quantum well layers, wherein the doping concentration of several quantum barrier doped layers gradually decreases.

7. The method for fabricating a deep ultraviolet LED with a modulation-doped multi-quantum-well structure according to claim 6, characterized in that, In step S41, during the interval, the organic source is stopped while ammonia is continued to flow, 0.1 s ≤ t0 ≤ 10 s.

8. The method for fabricating a deep ultraviolet LED with a modulation-doped multi-quantum-well structure according to claim 6, characterized in that, The growth temperature of the quantum barrier doped layer is T1, the growth temperature of the first quantum barrier undoped layer and the second quantum barrier undoped layer is T2, and the growth temperature of the quantum well layer is T3, satisfying the following relationship: 1200℃≥T1≥T2=T3≥1000℃. When T1=T2, the thickness of the first undoped quantum barrier layer is a0, and the thickness of the second undoped quantum barrier layer is a1; when T1>T2, the thickness of the first undoped quantum barrier layer is a0+(T1-T2)*t, and the thickness of the second undoped quantum barrier layer is a1+(T1-T2)*f, and 0.1≤f≤10, where f is in nm / ℃.

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