Deep ultraviolet light emitting diode

Abstract

According to the deep ultraviolet light-emitting diode provided by the invention, the first sub-layer in the electron blocking layer is made of AlN or AlGaN material with relatively high Al content, has a relatively large band gap, can form a relatively high potential barrier, has a very strong blocking effect on electrons, and reduces electron leakage, so that more electrons can be remained in an active region to participate in compounding with holes, and thus the light-emitting efficiency of the deep ultraviolet light-emitting diode is improved. Therefore, the number of generated photons is increased, and the output power is improved. Meanwhile, by reasonably setting the Al component content difference of the first sub-layer and the second sub-layer, the electric field distribution situation in the electron blocking layer can be adjusted, the injection speed, injection direction and the like of electrons can be optimized through the internal electric field, the electrons can be more evenly and appropriately injected into the quantum well active layer, and the quantum well performance is improved. And better matched injection with holes is formed, so that the recombination probability of electrons and holes is improved, and finally, the output efficiency of the deep ultraviolet light-emitting diode is improved.

Description

Technical Field

[0001] The invention relates to the field of semiconductor optoelectronics, and in particular to a deep ultraviolet light emitting diode. Background Art

[0002] Among ultraviolet rays, light with a wavelength of 200 nanometers to 350 nanometers is called deep ultraviolet. Deep ultraviolet light-emitting diodes have great application value in lighting, sterilization, medical treatment, printing, biochemical testing, high-density information storage and confidential communication due to their advantages such as high efficiency, environmental protection, energy saving and reliability. These advantages are unmatched by ordinary ultraviolet light-emitting diodes.

[0003] At present, in AlGaN-based deep ultraviolet light-emitting diodes, the quantum well gain region requires uniform carrier injection to achieve population inversion to form optical gain. Due to problems such as doping difficulties, AlGaN-based quantum wells have serious uneven carrier injection problems. Quantum wells with less hole injection become light absorption loss areas because it is difficult to achieve population inversion, resulting in a decrease in the output power of deep ultraviolet light-emitting diodes.

[0004] Therefore, it is necessary to propose a new deep ultraviolet light emitting diode design solution to solve the above problems existing in the prior art. Summary of the invention

[0005] The object of the present invention is to provide a deep ultraviolet light emitting diode, which is used to solve the technical problem of low light output power of the deep ultraviolet light emitting diode in the prior art.

[0006] In order to solve the above technical problems, the present invention provides a deep ultraviolet light-emitting diode, comprising a substrate, a buffer layer, a capping layer, a lower confinement layer, a lower waveguide layer, a quantum well active layer, an upper waveguide layer, an electron blocking layer, an upper confinement layer and a contact layer which are sequentially stacked along a growth direction, wherein the electron blocking layer comprises at least one periodic structure, and each periodic structure comprises a first sublayer and a second sublayer which are stacked along the growth direction; The material of the first sub-layer is AlN or AlGaN material, and the material of the second sub-layer is AlGaN material; the Al component content of the first sub-layer is greater than the Al component content of the second sub-layer.

[0007] Preferably, the first sublayer is Al x Ga 1-x N, the second sublayer is Al y Ga 1-y The relationship between N, x and y satisfies: 100%>x>y≥40%.

[0008] Preferably, the thickness of the first sublayer is 0.1-10 nm, and the thickness of the second sublayer is 1-50 nm.

[0009] Preferably, the first sublayer is an unintentionally doped layer or a P-type doped layer; the doping concentration of the P-type doped first sublayer is 1E17~1E19cm -3 .

[0010] Preferably, the first sublayer includes an unintentionally doped layer and a P-type doped layer stacked along the growth direction, and the thickness ratio of the unintentionally doped layer to the P-type doped layer is 10% to 60%.

[0011] Preferably, the second sublayer is a P-type doped AlGaN material with a doping concentration of 1E17~1E19cm -3 .

[0012] Preferably, the quantum well active layer comprises at least one potential well layer and at least two potential barrier layers which are alternately arranged, each potential well layer is inserted between two adjacent potential barrier layers, and the period number of the quantum well active layer is 1 to 4; Among them, the material of the potential well layer is Al a Ga 1-a N, thickness is 0.5~5nm, 1>a>0; the material of the barrier layer is Al b Ga 1-b N, thickness is 1~10nm, 1>b>0.

[0013] Preferably, the material of the lower waveguide layer is N-type doped Al m Ga 1-m N, 1>m>0.

[0014] Preferably, the material of the upper waveguide layer is P-type doped AlGaN; the Al component content of the upper waveguide layer decreases linearly along the growth direction.

[0015] Preferably, the initial Al composition of the interface of the upper waveguide layer close to the quantum well active layer is n, the final Al composition of the interface of the upper waveguide layer close to the electron blocking layer is p, and m, n and p satisfy the following relationship: m=(n+p) / 2.

[0016] The beneficial effects of the present invention are as follows: Different from the prior art, the present invention provides a deep ultraviolet light-emitting diode, in which the first sublayer of the electron blocking layer adopts AlN or AlGaN material with relatively high Al content, which has a large band gap, can form a high potential barrier, and has a strong blocking effect on electrons, reducing electron leakage, so that more electrons can remain in the active area to participate in the recombination with holes, thereby increasing the number of generated photons and helping to improve the output power. At the same time, the present invention can adjust the electric field distribution inside the electron blocking layer by reasonably setting the difference in the Al component content of the first sublayer and the second sublayer. This internal electric field can optimize the injection speed and injection direction of electrons, so that electrons can be more evenly and appropriately injected into the quantum well active layer, forming a better matching injection with holes, thereby increasing the recombination probability of electrons and holes, and ultimately improving the output efficiency of the deep ultraviolet light-emitting diode. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of the cross-sectional structure of a deep ultraviolet light-emitting diode provided by an embodiment of the present invention; In the figure: 100 - deep ultraviolet light emitting diode; 11 - substrate; 12 - buffer layer; 13 - cover layer; 14 - lower confinement layer; 15 - lower waveguide layer; 16 - quantum well active layer; 17 - upper waveguide layer; 18 - electron blocking layer; 19 - upper confinement layer; 110 - contact layer. DETAILED DESCRIPTION

[0018] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] In view of the shortcomings of the prior art, the present invention provides a deep ultraviolet light emitting diode 100 having an electron blocking structure with Al component modulation, so as to enhance its electron confinement capability, thereby improving the output power of the deep ultraviolet light emitting diode 100 .

[0020] See also Figure 1 , Figure 1A schematic diagram of the cross-sectional structure of a deep ultraviolet light-emitting diode 100 provided in an embodiment of the present invention; the present invention first provides a deep ultraviolet light-emitting diode 100, comprising a substrate 11, a buffer layer 12, a capping layer 13, a lower confinement layer 14, a lower waveguide layer 15, a quantum well active layer 16, an upper waveguide layer 17, an electron blocking layer 18, an upper confinement layer 19 and a contact layer 110 sequentially stacked along a growth direction, the electron blocking layer 18 comprising at least one periodic structure, each periodic structure comprising a first sublayer and a second sublayer stacked along the growth direction; The material of the first sub-layer is AlN or AlGaN material, and the material of the second sub-layer is AlGaN material; the Al component content of the first sub-layer is greater than the Al component content of the second sub-layer.

[0021] In the embodiment of the present invention, the substrate 11 is an AlN single crystal substrate 11 .

[0022] In an embodiment of the present invention, the material of the buffer layer 12 is AlN, the growth temperature thereof is 1200~1400°C, and the thickness is 500~4000nm; wherein, the buffer layer 12 can play a role of transition and connection, so that the crystal growth quality of subsequent layers is higher, and the dislocations, defects and other problems caused by lattice mismatch are reduced, thereby facilitating improving the performance of the entire deep ultraviolet light-emitting diode 100.

[0023] In an embodiment of the present invention, the material of the covering layer 13 is N-type doped AlGaN material, the Al component content of which is 20% to 90%, the growth temperature is 800 to 1200°C, and the thickness is 500 to 4000nm; wherein, the N-type doping of the covering layer 13 introduces a large number of electron donor impurities, which can significantly increase the electron concentration inside the material, so that electrons can be more smoothly and quickly transmitted from external contact areas such as electrodes to the subsequent quantum well active layer 16, ensuring that a sufficient number of electrons participate in the composite luminescence process with holes, thereby improving the luminescence efficiency and output power of the entire deep ultraviolet light-emitting diode 100.

[0024] In the embodiment of the present invention, the material of the lower limiting layer 14 is N-type doped AlGaN material, the Al component content of which is 20% to 80%, the growth temperature is 700~1100℃, and the thickness is 50~300nm; wherein, the lower limiting layer 14 adopts N-type doped AlGaN material, and the band gap width cooperates with the band structure of the adjacent layer to form an effective limiting barrier for electrons, prevent excessive diffusion of electrons in the horizontal direction (lateral direction), confine electrons in the area close to the active layer, ensure that electrons can be efficiently injected into the quantum well active layer 16, thereby improving the luminous efficiency.

[0025] In the embodiment of the present invention, the material of the lower waveguide layer 15 is N-type doped Al m Ga1-m N, and the Al component is constant; wherein, 0.7>m>0.3, the growth temperature is 700~1100℃, and the thickness is 50~200nm; wherein, the lower waveguide layer 15 can effectively confine photons in a specific area through its own suitable refractive index and the refractive index difference formed with the surrounding layer, and reduce the leakage of photons in undesired directions (such as lateral or toward the substrate 11, etc.).

[0026] In the embodiment of the present invention, the growth temperature of the quantum well active layer 16 is 700-1100° C., the quantum well active layer 16 includes at least one potential well layer and at least two potential barrier layers arranged alternately, each potential well layer is inserted between two adjacent potential barrier layers, and the period number of the quantum well active layer 16 is 1-4; Among them, the material of the potential well layer is Al a Ga 1-a N, thickness is 0.5~5nm, 1>a>0; the material of the barrier layer is Al b Ga 1-b N, thickness is 1~10nm, 1>b>0.

[0027] In the embodiment of the present invention, the material of the upper waveguide layer 17 is P-type doped AlGaN, and its growth temperature is 700-1100°C. The thickness of the upper waveguide layer 17 is the same as that of the lower waveguide layer 15, and the average Al component content of the upper waveguide layer 17 needs to be the same as that of the lower waveguide layer 15. The above design helps to construct a relatively symmetrical optical waveguide structure, which can guide the propagation direction of photons more evenly and symmetrically, so that photons are more evenly restricted and guided in the vertical direction, reduce the asymmetry of the photon propagation path and the photon scattering and refraction direction disorder caused by the thickness difference, thereby improving the photon emission efficiency, which helps to enhance the luminous intensity and luminous uniformity of the entire light-emitting diode.

[0028] Preferably, the Al content of the upper waveguide layer 17 decreases linearly along the growth direction. There are two ways to achieve the linear change of the Al content of the upper waveguide layer 17: the first is to achieve it by linear temperature change; the second is to achieve it by linear Al source flow rate change.

[0029] Preferably, the initial Al composition of the interface of the upper waveguide layer 17 close to the quantum well active layer 16 is n, the final Al composition of the interface of the upper waveguide layer 17 close to the electron blocking layer 18 is p, and m, n and p satisfy the following relationship: m=(n+p) / 2.

[0030] In an embodiment of the present invention, the growth temperature of the electron blocking layer 18 is 700~1100℃; the electron blocking layer 18 includes at least one periodic structure, each periodic structure includes a first sublayer and a second sublayer stacked along the growth direction; the material of the first sublayer is AlN or AlGaN material, and the material of the second sublayer is AlGaN material; the Al component content of the first sublayer is greater than the Al component content of the second sublayer.

[0031] Specifically, the first sublayer is Al x Ga 1-x N, the second sublayer is Al y Ga 1-y The relationship between N, x and y satisfies: 100%>x>y≥40%; preferably, x>y+10%.

[0032] Specifically, the thickness of the first sublayer is 0.1-10 nm, and the thickness of the second sublayer is 1-50 nm.

[0033] When the first sublayer acts as an unintentionally doped layer, the unintentionally doped first sublayer can maintain a relatively stable energy band structure, relying on its own original material properties (such as a suitable band gap, etc.) to form a blocking effect on electrons, thereby avoiding the uncertainty factors introduced by doping affecting its effective restriction on electrons, and helping to ensure that the electron blocking layer 18 plays a stable and reliable role in blocking electron leakage, assisting in regulating electron transport, etc.

[0034] When the first sublayer is used as a P-type doping layer, the doping concentration of the first sublayer for P-type doping is 1E17~1E19cm -3 The holes generated by P-type doping can interact with electrons. This interaction will form a specific electric field distribution inside and near the first sublayer, which can help block the further diffusion of electrons and strengthen the confinement effect on electrons.

[0035] Specifically, the first sublayer includes an unintentionally doped layer and a P-type doped layer stacked along the growth direction, and the thickness ratio of the unintentionally doped layer to the P-type doped layer is 10% to 60%; the second sublayer is a P-type doped AlGaN material with a doping concentration of 1E17~1E19cm -3 .

[0036] In the embodiment of the present invention, the growth temperature of the upper confinement layer 19 is 700-1100° C., and the material thereof is P-type doped AlGaN, the Al component content is 20%-70%, and the thickness is 1-50 nm.

[0037] In the embodiment of the present invention, the growth temperature of the contact layer 110 is 400-900° C., the material thereof is P-type doped GaN, and the thickness thereof is 1-20 nm.

[0038] Specifically, the method for preparing the epitaxial structure of the deep ultraviolet light-emitting diode 100 provided in the embodiment of the present invention is carried out in a MOCVD (metal organic chemical vapor deposition) device. The detailed steps of the above preparation method include: Step 1: heating the AlN single crystal substrate 11 and annealing it in a hydrogen atmosphere for 5 minutes to 20 minutes; annealing can improve the crystal quality of the AlN single crystal substrate 11 and remove impurities; Step 2: raising the temperature to 1200° C. to 1400° C. to grow a buffer layer 12 made of AlN material with a thickness of 500 nm to 4000 nm; Step 3, cooling to 800°C-1200°C, growing a cap layer 13 of n-type AlGaN material, wherein the Al component is 20%-90% and the thickness is 500nm-4000nm; Step 4, cooling to 700°C-1100°C, growing a lower confinement layer 14, the thickness of which is 50nm-300nm, and the Al component is 20%-80%; Step 5, cooling to 700°C-1100°C, growing a lower waveguide layer 15, with a thickness of 50nm-200nm and an Al component of 30%-70%; Step 6: Cool down to 700℃~1100℃ and grow Al a Ga 1-a N / A b Ga 1-b The quantum well active layer 16 of N; the material of the potential well layer is Al a Ga 1-a N, thickness is 0.5nm~5nm; the material of the barrier layer is Al b Ga 1-b N, thickness is 1nm~10nm; the period number of the quantum well active layer 16 is 1~4; Step 7, raising the temperature to 700° C. to 1100° C., growing an upper waveguide layer 17, wherein the thickness of the upper waveguide layer 17 is the same as that of the lower waveguide layer 15, and the average Al composition thereof is the same as that of the lower waveguide layer 15; Step eight, raising the temperature to 700° C. to 1100° C. to grow an electron blocking layer 18 with a modulated Al component, and the growth gas atmosphere is a nitrogen atmosphere to create a stable growth environment; Step nine, keeping the temperature constant, growing an upper confinement layer 19 of a P-type AlGaN material, wherein the Al component content is 20% to 70%, the thickness is 1 to 50 nm, and Mg is used as a P-type dopant; Step 10: Cool down to 400° C.-900° C., grow a contact layer 110 made of P-type GaN material with a thickness of 1-20 nm, and use Mg as a P-type dopant.

[0039] The technical solution of the present application is now described in conjunction with specific embodiments.

[0040] Embodiment 1: The epitaxial structure of the deep ultraviolet light-emitting diode 100100 provided in Example 1 of the present invention is shown below in sequence along the growth direction: Substrate 11, made of AlN single crystal substrate 11; Buffer layer 12, made of AlN, with a thickness of 500 nm; The cover layer 13 is made of Si-doped AlGaN, with an Al content of 50% and a thickness of 2000 nm; The lower confinement layer 14 is made of Si-doped AlGaN, with an Al content of 60% and a thickness of 200 nm; The lower waveguide layer 15 is made of Si-doped AlGaN, with an Al content of 55% and a thickness of 100 nm; The quantum well active layer 16 includes at least one potential well layer and at least two potential barrier layers which are alternately arranged, and each potential well layer is inserted between two adjacent potential barrier layers; wherein the material of the potential barrier layer is AlGaN, the Al component content is 55%, and the thickness of the potential barrier layer is 5nm; the material of the potential well layer is AlGaN, the Al component content is 45%, and the thickness of the potential well layer is 1nm; The upper waveguide layer 17 is made of Si-doped AlGaN, has an average Al content of 55%, and a thickness of 100 nm; The electron blocking layer 18 includes a periodic structure, which includes a first sublayer and a second sublayer stacked in sequence along the growth direction; the first sublayer is an unintentionally doped AlN material with a thickness of 1 nm; the second sublayer is an MgN material with a thickness of 1 nm; the second sublayer is an Mg-doped AlGaN material with an Al component content of 70% and a thickness of 10 nm; The upper confinement layer 19 is made of Mg-doped AlGaN, with an Al content of 60% and a thickness of 20 nm; The contact layer 110 is made of Mg-doped GaN and has a thickness of 10 nm.

[0041] Comparative Example 1: The deep ultraviolet light-emitting diode 100 prepared by conventional process, the epitaxial structure and material of the deep ultraviolet light-emitting diode 100 provided in comparative example 1 are substantially the same as those of embodiment 1, and the only difference is that the structure of the electron blocking layer 18 is different: The electron blocking layer 18 is made of Mg-doped AlGaN material, with an Al component content of 70% and a thickness of 11 nm.

[0042] Furthermore, the epitaxial structure of the deep ultraviolet light-emitting diode 100 prepared in Example 1 and the epitaxial structure of the deep ultraviolet light-emitting diode 100 prepared in the comparative example were respectively assembled with the same electrode material to obtain two deep ultraviolet light-emitting diodes 100 with different film structures. The test results of the above two deep ultraviolet light-emitting diodes 100 are shown in the following Table 1: Table 1 Test results of this embodiment and comparative example

[0043] Among them, through comparison, it can be seen that the deep ultraviolet light emitting diode 100 prepared in Example 1 of the present invention has higher optical power at 100mA than the deep ultraviolet light emitting diode 100 prepared in the comparative example, which shows that Example 1 can improve the carrier confinement capability, thereby improving the luminous efficiency of the deep ultraviolet light emitting diode 100.

[0044] Specifically, the deep ultraviolet light-emitting diode 100 prepared in Example 1 of the present invention has a lower turn-on voltage at 1uA than the deep ultraviolet light-emitting diode 100 prepared in the comparative example, which shows that the preparation process of Example 1 achieves more accurate and more effective doping, so that the carrier concentration of the P-type and N-type semiconductor regions reaches a more ideal state. When a smaller forward bias (such as a bias corresponding to 1μA) is applied, there are enough carriers injected into the active area to participate in the composite light emission. In contrast, the doping situation of the comparative example 1 may not be so ideal, so the turn-on voltage is relatively high.

[0045] In summary, different from the prior art, the present invention provides a deep ultraviolet light-emitting diode 100, in which the first sublayer of the electron blocking layer 18 is made of AlN or AlGaN material with a relatively high Al content, which has a large band gap and can form a high potential barrier, which has a strong blocking effect on electrons, reduces electron leakage, and allows more electrons to remain in the active area to participate in the recombination with holes, thereby increasing the number of photons generated, which helps to improve the output power. At the same time, the present invention can adjust the electric field distribution inside the electron blocking layer 18 by reasonably setting the difference in the Al component content of the first sublayer and the second sublayer. This internal electric field can optimize the injection speed and injection direction of electrons, so that electrons can be more uniformly and appropriately injected into the quantum well active layer 16, forming a better matching injection with holes, thereby increasing the recombination probability of electrons and holes, and ultimately improving the output efficiency of the deep ultraviolet light-emitting diode 100.

[0046] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For matters that are not described in detail in some embodiments, reference may be made to the description in other embodiments.

[0047] The above embodiments only express the implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A deep ultraviolet light emitting diode, characterized in that: The invention comprises a substrate, a buffer layer, a capping layer, a lower limiting layer, a lower waveguide layer, a quantum well active layer, an upper waveguide layer, an electron blocking layer, an upper limiting layer and a contact layer which are sequentially stacked in a growth direction, wherein the electron blocking layer comprises at least one periodic structure, and each of the periodic structures comprises a first sublayer and a second sublayer which are stacked in a layered manner in the growth direction; The material of the first sub-layer is AlN or AlGaN material, and the material of the second sub-layer is AlGaN material; the Al component content of the first sub-layer is greater than the Al component content of the second sub-layer.

2. The deep ultraviolet light emitting diode according to claim 1, characterized in that: The first sublayer is Al x Ga 1-x N, the second sublayer is Al y Ga 1-y The relationship between N, x and y satisfies: 100%>x>y≥40%.

3. The deep ultraviolet light emitting diode according to claim 1, characterized in that: The thickness of the first sublayer is 0.1-10 nm, and the thickness of the second sublayer is 1-50 nm.

4. The deep ultraviolet light emitting diode according to claim 1, characterized in that: The first sublayer is an unintentionally doped layer or a P-type doped layer; the doping concentration of the P-type doped layer in the first sublayer is 1E17~1E19cm -3 .

5. The deep ultraviolet light emitting diode according to claim 1, characterized in that: The first sublayer includes an unintentional doping layer and a P-type doping layer stacked along the growth direction, and the thickness ratio of the unintentional doping layer to the P-type doping layer is 10% to 60%.

6. The deep ultraviolet light emitting diode according to claim 1, characterized in that: The second sublayer is a P-type doped AlGaN material with a doping concentration of 1E17~1E19cm -3 .

7. The deep ultraviolet light emitting diode according to claim 1, characterized in that: The quantum well active layer includes at least one potential well layer and at least two potential barrier layers which are alternately arranged, each potential well layer is inserted between two adjacent potential barrier layers, and the period number of the quantum well active layer is 1 to 4; Wherein, the material of the potential well layer is Al a Ga 1-a N, thickness is 0.5~5nm, 1>a>0; the material of the barrier layer is Al b Ga 1-b N, thickness is 1~10nm, 1>b>0.

8. The deep ultraviolet light emitting diode according to claim 1, characterized in that: The material of the lower waveguide layer is N-type doped Al m Ga 1-m N, 1>m>0.

9. The deep ultraviolet light emitting diode according to claim 8, characterized in that: The material of the upper waveguide layer is P-type doped AlGaN; the Al component content of the upper waveguide layer decreases linearly along the growth direction.

10. The deep ultraviolet light emitting diode according to claim 9, characterized in that: The initial Al composition of the interface of the upper waveguide layer close to the quantum well active layer is n, and the final Al composition of the interface of the upper waveguide layer close to the electron blocking layer is p, and m, n and p satisfy the following relationship: m=(n+p) / 2.

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