A vertical structure deep ultraviolet light emitting diode and preparation method thereof
By removing the P-GaN layer and deposition of reflective layers, vertical structure deep UV light emitting diodes are formed, which solves the problems of low light extraction efficiency and poor current expansion, significantly improves the performance of the equipment, and achieves higher light output and current Expand.
Patent Information
- Application Number
- CN202011216444.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2020-11-04
- Publication Date
- 2024-12-31
- Estimated Expiration
- 2040-11-04
AI Technical Summary
The low light extraction efficiency and poor current spread of existing AlGaN-based deep ultraviolet light emitting diodes have made it difficult to replace mercury lamps in high-power applications, especially the P-GaN layer's strong absorption of deep ultraviolet light and current congestion problems are difficult to solve.
By removing part of the P-GaN layer, depositing a reflective layer and an adhesive metal layer, and making an electrode metal layer on the N-AlGaN layer, combining the conductive substrate layer to form a vertical structure to reduce the absorption of light by the P-GaN layer and Improve current expansion.
The light extraction efficiency and current horizontal expansion of the deep ultraviolet light emitting diode are improved, the light absorption by the P-GaN layer is reduced, current congestion is avoided, and the performance of the equipment is significantly improved.
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Figure CN112310255B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of semiconductor devices and relates to a deep ultraviolet light emitting diode and a preparation method thereof, and more specifically, to a vertical structure deep ultraviolet light emitting diode and a preparation method thereof. Background Art
[0002] AlGaN-based deep ultraviolet light-emitting diodes are a new type of solid-state ultraviolet light source. Compared with traditional mercury lamp power ultraviolet light sources, they have many advantages such as continuously adjustable emission wavelength, long life, and small size. Therefore, AlGaN-based deep ultraviolet light-emitting diodes have replaced mercury lamps in some application scenarios with low optical power requirements, but they cannot replace mercury lamps in applications with high power requirements such as water disinfection.
[0003] At present, the external quantum efficiency of product-level deep ultraviolet light-emitting diodes is only about 5%, which also limits their promotion and application in the market. One of the main factors leading to the low external quantum efficiency of deep ultraviolet light-emitting diodes is the very low light extraction efficiency. In order to increase the injection efficiency of holes in AlGaN-based deep ultraviolet light-emitting diodes, the existing mainstream technology is to use P-type GaN as the hole injection layer, but P-type GaN has extremely low light transmittance in the deep ultraviolet band, which also leads to the current very low light extraction efficiency.
[0004] In view of the above reasons, most of the current AlGaN-based deep ultraviolet light-emitting diodes are flip-chip structures, emitting light at the bottom of sapphire, which also solves the problem of poor heat dissipation of sapphire.
[0005] However, the flip-chip structure of the light-emitting diode is still a lateral structure with the electrodes on the same side, which causes the current to flow unequally in the lateral direction of the N-type layer, resulting in local current congestion. In order to solve this problem, some people have begun to study vertical structure deep ultraviolet light-emitting diodes.
[0006] Vertical structure deep ultraviolet light-emitting diodes emit light from the N-type surface, and combined with surface roughening and other technologies, the light extraction efficiency can be significantly improved, but it still cannot solve the problem of P-GaN's strong absorption of deep ultraviolet light. Therefore, how to reduce or alleviate P-GaN's strong absorption of deep ultraviolet light without affecting the lateral expansion of current is a technical problem that needs to be solved urgently.
[0007] In view of the above technical defects of the prior art, it is urgent to develop a new type of vertical structure deep ultraviolet light emitting diode. Summary of the invention
[0008] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a vertical structure deep ultraviolet light emitting diode and a preparation method thereof, which can solve the problems of low light extraction efficiency and poor lateral current expansion in the prior art.
[0009] In order to achieve the above object, the present invention provides the following technical solutions:
[0010] A method for preparing a vertical structure deep ultraviolet light-emitting diode, characterized in that it comprises the following steps:
[0011] (1) removing all or part of a portion of a P-GaN layer of an epitaxial structure of a deep ultraviolet light-emitting diode;
[0012] (2) depositing a reflective layer on the surface of the P-GaN layer;
[0013] (3) depositing an adhesive metal layer on the surface of the reflective layer;
[0014] (4) bonding a conductive substrate layer on the adhesive metal layer;
[0015] (5) removing all layers below the N-AlGaN layer of the epitaxial structure of the deep ultraviolet light-emitting diode, so that the N-AlGaN layer is exposed at the outermost layer;
[0016] (6) An electrode metal layer is fabricated on a portion of the surface of the N-AlGaN layer, and a position of the electrode metal layer is made to correspond to the portion of the P-GaN layer.
[0017] Preferably, in the step (1), a certain pattern is first prepared on the surface of a partial area of the P-GaN layer by using a photolithography technique, and then an etching technique is used to etch away the portion of the P-GaN layer where the pattern is prepared.
[0018] Preferably, in the step (4), the adhesive metal layer and the conductive substrate layer are bonded together by bonding or electroplating.
[0019] Preferably, in step (5), all layers below the N-AlGaN layer of the epitaxial structure of the deep ultraviolet light emitting diode are removed by laser stripping, chemical etching or dry etching, so that the N-AlGaN layer is exposed at the outermost layer.
[0020] Preferably, the method for preparing the vertical structure deep ultraviolet light-emitting diode further comprises step (7): roughening the surface of the N-AlGaN layer on which the electrode metal layer is not formed.
[0021] Preferably, the roughening treatment is performed by chemical corrosion or physical etching.
[0022] In addition, the present invention also provides a vertical structure deep ultraviolet light-emitting diode, which includes N-AlGaN, a multi-quantum well layer, a P-AlGaN layer and a P-GaN layer arranged from bottom to top, characterized in that all or part of a partial area of the P-GaN layer is removed and a reflective layer is deposited on the upper surface of the P-GaN layer, an adhesive metal layer is deposited on the upper surface of the reflective layer, a conductive substrate layer is combined on the upper surface of the adhesive metal layer, an electrode metal layer is made on a partial lower surface of the N-AlGaN layer and the position of the electrode metal layer corresponds to the partial area of the P-GaN layer.
[0023] Preferably, the reflective layer is made of one or more combinations of Ni, Au, Al, Pt, AuSn, ITO, Ti, Cr, DBR, and ODR.
[0024] Preferably, the adhesive metal layer is made of any combination of Ni, Au, Al, Pt, AuSn, Ti, and Cr.
[0025] Preferably, the conductive substrate layer is made of metal or silicon.
[0026] Compared with the prior art, the vertical structure deep ultraviolet light-emitting diode and the preparation method thereof of the present invention have the following beneficial technical effects:
[0027] 1. It etches out all or part of the P-GaN layer, thereby reducing the absorption of deep ultraviolet light by the P-GaN layer, thereby improving the light extraction efficiency of the deep ultraviolet light-emitting diode.
[0028] 2. The electrode metal layer is placed at a position corresponding to the etched portion of the P-GaN layer, thereby increasing the lateral expansion of the current and reducing current congestion.
[0029] 3. By roughening the surface of the N-AlGaN layer, the output of deep ultraviolet light can be further improved. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 The present invention is a flowchart of a method for preparing a vertical structure deep ultraviolet light-emitting diode.
[0031] Figure 2 It is a schematic diagram of the epitaxial structure used for preparing the vertical structure deep ultraviolet light emitting diode of the present invention.
[0032] Figure 3 It is a schematic diagram after removing all or part of a partial area of a P-GaN layer of an epitaxial structure of a deep ultraviolet light emitting diode.
[0033] Figure 4 This is a schematic diagram after a reflective layer is deposited on the surface of the P-GaN layer.
[0034] Figure 5 It is a schematic diagram after a bonding metal layer is deposited on the surface of the reflective layer.
[0035] Figure 6 It is a schematic diagram after a conductive substrate layer is combined on the bonding metal layer.
[0036] Figure 7 It is a schematic diagram after all layers below the N-AlGaN layer of the epitaxial structure of a deep ultraviolet light emitting diode are removed to expose the N-AlGaN layer at the outermost layer.
[0037] Figure 8 It is a schematic structural diagram of a vertical structure deep ultraviolet light emitting diode of the present invention. DETAILED DESCRIPTION
[0038] The present invention is further described below in conjunction with the accompanying drawings and embodiments, and the contents of the embodiments are not intended to limit the protection scope of the present invention.
[0039] The invention relates to a vertical structure deep ultraviolet light emitting diode and a preparation method thereof, which are used to solve the problems of low light extraction efficiency and poor current lateral expansion in the prior art.
[0040] Figure 1 FIG. 2 is a flow chart showing a method for preparing a vertical structure deep ultraviolet light emitting diode according to the present invention. Figure 1 As shown, the method for preparing a vertical structure deep ultraviolet light-emitting diode of the present invention comprises the following steps:
[0041] 1. Remove all or part of a portion of the P-GaN layer 107 of the epitaxial structure of the deep ultraviolet light emitting diode.
[0042] Of course, before this, it is necessary to select the epitaxial structure of the deep ultraviolet light emitting diode. In the present invention, as long as the epitaxial structure of the deep ultraviolet light emitting diode has a P-GaN layer, a P-AlGaN layer, a multi-quantum well (MQWS) layer and an N-AlGaN layer arranged in sequence, the specific structure of the epitaxial structure of the deep ultraviolet light emitting diode is not limited.
[0043] Figure 2 FIG. 2 shows a schematic diagram of an exemplary epitaxial structure used in preparing a vertical structure deep ultraviolet light-emitting diode of the present invention. Figure 2As shown, the epitaxial structure of the deep ultraviolet light-emitting diode includes, from bottom to top, a substrate 101, an AlN layer (i.e., a buffer layer) 102, an AlGaN layer 103, an N-AlGaN layer 104, an MQWS layer (i.e., a multi-quantum well layer) 105, a P-AlGaN layer 106, and a P-GaN layer 107. Of course, the specific epitaxial structure used is not limited to the above structure.
[0044] The substrate 101 may be made of a variety of materials, including but not limited to sapphire, gallium nitride, silicon, aluminum nitride, and the like.
[0045] In the present invention, a certain pattern can be prepared on the surface of a part of the P-GaN layer 107 by photolithography. Then, the part of the P-GaN layer 107 where the pattern is prepared is etched away by etching technology, that is, the P-GaN layer where the pattern is prepared is etched away. Of course, when etching, the P-GaN layer where the pattern is prepared can be etched away completely, or only a part can be etched away, so that the P-GaN layer where the pattern is prepared becomes thinner.
[0046] in, Figure 3 The schematic diagram shows a deep ultraviolet light emitting diode after all or part of the P-GaN layer of the epitaxial structure is removed. Figure 3 It can be seen that only a part of the partial area of the P-GaN layer is etched away, that is, only a part of the P-GaN layer is thinned, but not all of it is etched away. Of course, the partial area of the P-GaN layer can also be etched away completely, in which case a part of the P-AlGaN layer 106 will be exposed.
[0047] Since the P-GaN layer has a strong absorption of light in the deep ultraviolet (260nm-320nm) band and has a very low transmittance, but the current mainstream epitaxial structure level cannot eliminate this layer, the light extraction efficiency of the deep ultraviolet light-emitting diode is often low. In the present invention, by etching away part of the P-GaN layer in whole or in part, the absorption of the deep ultraviolet light by the P-GaN layer can be reduced, thereby greatly improving the light extraction efficiency of the deep ultraviolet light-emitting diode.
[0048] 2. Depositing a reflective layer 201 on the surface of the P-GaN layer 107 .
[0049] In the present invention, after removing all or part of the partial area of the P-GaN layer 107 of the epitaxial structure of the deep ultraviolet light emitting diode, a reflective layer 201 is deposited on the surface of the P-GaN layer 107, such as Figure 4 shown.
[0050] The reflective layer 201 is a layer with high reflectivity to deep ultraviolet light, and may be a metal layer or other thin film layer.
[0051] In the present invention, the material of the reflective layer 201 is not specifically limited, as long as it has high reflectivity to deep ultraviolet light. Preferably, the reflective layer 201 can be made of one or more combinations of Ni, Au, Al, Pt, AuSn, ITO, Ti, Cr, DBR, and ODR.
[0052] More preferably, the thickness of the reflective layer 201 is uniform. Thus, in the area where the P-GaN layer is removed, after the reflective layer 201 is deposited, the area is still concave.
[0053] 3. Depositing an adhesive metal layer 202 on the surface of the reflective layer 201 .
[0054] In the present invention, after a reflective layer 201 is deposited on the surface of the P-GaN layer 107, an adhesive metal layer 202 needs to be deposited on the surface of the reflective layer 201. Figure 5 shown.
[0055] The bonding metal layer 202 mainly plays a bonding role and can be a metal film.
[0056] In the present invention, the material of the bonding metal layer 202 is not specifically limited, as long as it has a bonding effect. Preferably, the bonding metal layer 202 can be made of any combination of Ni, Au, Al, Pt, AuSn, Ti, and Cr.
[0057] More preferably, the thickness of the adhesive metal layer 202 is also uniform. Thus, in the area where the P-GaN layer is removed, after the adhesive metal layer 202 is deposited, the area is still recessed.
[0058] Fourth, a conductive substrate layer 301 is bonded onto the bonding metal layer 202 .
[0059] In the present invention, after a bonding metal layer 202 is deposited on the surface of the reflective layer 201, a conductive substrate layer 301 needs to be bonded to the bonding metal layer 202. Figure 6 shown.
[0060] The conductive substrate layer 301 is used as a conductive substrate.
[0061] In the present invention, there is no specific limitation on the material of the conductive substrate layer 301, as long as it can be used as a conductive substrate. Preferably, the conductive substrate layer 301 can be made of metal, silicon or other materials.
[0062] Meanwhile, in the present invention, preferably, the adhesive metal layer 202 and the conductive substrate layer 301 can be combined together by bonding, electroplating or other methods.
[0063] More preferably, the thickness of the conductive substrate layer 301 is greater than the thickness of other layers. In addition, the surface of the conductive substrate layer 301 is flat without any concave or convex shapes.
[0064] 5. All layers below the N-AlGaN layer 104 of the epitaxial structure of the deep ultraviolet light emitting diode are removed, so that the N-AlGaN layer 104 is exposed at the outermost layer.
[0065] In the present invention, after bonding a conductive substrate layer 301 to the bonding metal layer 202, all layers below the N-AlGaN layer 104 of the epitaxial structure of the deep ultraviolet light emitting diode need to be removed, so that the N-AlGaN layer 104 is exposed at the outermost layer, such as Figure 7 shown.
[0066] As mentioned above, the epitaxial structure of the deep ultraviolet light-emitting diode used in the present invention includes, from bottom to top, a substrate 101, an AlN layer 102, an AlGaN layer 103, an N-AlGaN layer 104, an MQWS layer (i.e., a multi-quantum well layer) 105, a P-AlGaN layer 106, and a P-GaN layer 107. Therefore, in this step, the native substrate 101, the AlN layer (i.e., a buffer layer) 102, and the AlGaN layer 103 need to be removed so that the N-AlGaN layer 104 is exposed at the outermost layer.
[0067] Meanwhile, in the present invention, the specific removal method is not limited. Preferably, the N-AlGaN layer 104 of the epitaxial structure of the deep ultraviolet light emitting diode can be removed by laser lift-off, chemical etching, dry etching or other methods.
[0068] 6. An electrode metal layer 401 is formed on a portion of the surface of the N-AlGaN layer 104 , and the position of the electrode metal layer 401 corresponds to the portion of the P-GaN layer 107 .
[0069] In the present invention, finally, the electrode metal layer 401 is formed on a part of the surface of the N-AlGaN layer 104. In addition, when forming the electrode metal layer 401, the position of the electrode metal layer 401 should correspond to the part of the P-GaN layer 107. In this way, the vertical structure deep ultraviolet light-emitting diode of the present invention is prepared. Figure 8 shown.
[0070] In a vertical structure deep ultraviolet light-emitting diode, the P-GaN layer 107 mainly provides holes, while the N-AlGaN layer 104 provides electrons. When current passes through, the movement of electrons and holes is mainly in the longitudinal direction, which easily causes current congestion. In the present invention, the removed part of the P-GaN layer 107 cannot or rarely provides holes, and the electrode metal layer 401 is made at the corresponding position of the part, so that the electron holes have to expand horizontally, thus avoiding current congestion.
[0071] Furthermore, in the present invention, preferably, after the electrode metal layer 401 is formed on a portion of the surface of the N-AlGaN layer 104, the surface of the N-AlGaN layer 104 where the electrode metal layer 401 is not formed can be roughened. By roughening the surface of the N-AlGaN layer, the output of deep ultraviolet light can be further improved.
[0072] In the present invention, no specific roughening treatment technology is limited. Preferably, the roughening treatment can be performed by chemical corrosion, physical etching or other methods.
[0073] Therefore, if Figure 8 As shown, the vertical structure deep ultraviolet light emitting diode of the present invention includes an N-AlGaN layer 104, a multi-quantum well layer 105, a P-AlGaN layer 106 and a P-GaN layer 107 arranged from bottom to top.
[0074] Wherein, all or part of a partial area of the P-GaN layer 107 is removed and a reflective layer 201 is deposited on the upper surface of the P-GaN layer 107 .
[0075] An adhesive metal layer 202 is deposited on the upper surface of the reflective layer 201 .
[0076] A conductive substrate layer 301 is bonded to the upper surface of the adhesive metal layer 202 .
[0077] An electrode metal layer 401 is formed on a portion of the lower surface of the N-AlGaN layer 104 , and a position of the electrode metal layer 401 corresponds to the portion of the P-GaN layer 107 .
[0078] Preferably, the reflective layer 201 is made of one or more combinations of Ni, Au, Al, Pt, AuSn, ITO, Ti, Cr, DBR, and ODR.
[0079] More preferably, the adhesive metal layer 202 is made of any combination of Ni, Au, Al, Pt, AuSn, Ti, and Cr.
[0080] More preferably, the conductive substrate layer 301 is made of metal or silicon.
[0081] The vertical structure deep ultraviolet light emitting diode of the present invention can reduce the absorption of deep ultraviolet light by removing a part of the P-GaN layer; at the same time, by making the electrode metal layer at the corresponding position of the removed part of the P-GaN layer, the electron holes have to expand laterally, thus avoiding current congestion.
[0082] The above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the embodiments here. Any obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.
Claims
1. A method for preparing a vertical structure deep ultraviolet light-emitting diode, characterized in that: The vertical structure deep ultraviolet light-emitting diode comprises an N-AlGaN layer, a multi-quantum well layer, a P-AlGaN layer and a P-GaN layer arranged from bottom to top, and a reflective layer is deposited on the upper surface of the P-GaN layer, an adhesive metal layer is deposited on the upper surface of the reflective layer, and a conductive substrate layer is bonded to the upper surface of the adhesive metal layer, an electrode metal layer is formed on a part of the lower surface of the N-AlGaN layer, and the position of the electrode metal layer corresponds to a part of the P-GaN layer. The method for preparing the vertical structure deep ultraviolet light-emitting diode comprises the following steps: (1) removing all or part of a partial region of a P-GaN layer (107) of an epitaxial structure of a deep ultraviolet light-emitting diode, so that the partial region of the P-AlGaN layer (106) is exposed, or the partial region of the P-GaN layer (107) is thinned, without removing it completely; in the step (1), a certain pattern is first prepared on the surface of the partial region of the P-GaN layer (107) by photolithography technology, and then the part of the surface of the P-GaN layer (107) where the pattern is prepared is etched away by etching technology, (2) depositing a reflective layer (201) on the surface of the P-GaN layer (107); (3) depositing an adhesive metal layer (202) on the surface of the reflective layer (201); (4) bonding a conductive substrate layer (301) on the adhesive metal layer (202); (5) removing all layers below the N-AlGaN layer (104) of the epitaxial structure of the deep ultraviolet light-emitting diode, so that the N-AlGaN layer (104) is exposed at the outermost layer; (6) forming an electrode metal layer (401) on a portion of the surface of the N-AlGaN layer (104), and making the position of the electrode metal layer (401) correspond to the portion of the P-GaN layer (107); The P-GaN layer (107) provides holes, and the N-AlGaN layer (104) provides electrons, so that the electrons and holes are expanded laterally, thereby avoiding current congestion; The thickness of the conductive substrate layer (301) is greater than the thickness of other layers, and the surface of the conductive substrate layer (301) is flat.
2. The method for preparing a vertical structure deep ultraviolet light-emitting diode according to claim 1, characterized in that: In the step (4), the adhesive metal layer (202) and the conductive substrate layer (301) are bonded together by bonding or electroplating.
3. The method for preparing a vertical structure deep ultraviolet light-emitting diode according to claim 2, characterized in that: In the step (5), all layers below the N-AlGaN layer (104) of the epitaxial structure of the deep ultraviolet light-emitting diode are removed by laser stripping, chemical etching or dry etching, so that the N-AlGaN layer (104) is exposed at the outermost layer.
4. The method for preparing a vertical structure deep ultraviolet light-emitting diode according to any one of claims 1 to 3, characterized in that , further comprising step (7): roughening the surface of the N-AlGaN layer (104) on which the electrode metal layer (401) is not formed.
5. The method for preparing a vertical structure deep ultraviolet light-emitting diode according to claim 4, characterized in that: The roughening treatment is performed by chemical corrosion or physical etching.
6. A vertical structure deep ultraviolet light-emitting diode, comprising an N-AlGaN layer (104), a multi-quantum well layer (105), a P-AlGaN layer (106) and a P-GaN layer (107) arranged from bottom to top, characterized in that: All or part of a partial area of the P-GaN layer (107) is removed, so that the partial area of the P-AlGaN layer (106) is exposed, or the partial area of the P-GaN layer (107) is thinned without removing it entirely, A reflective layer (201) is deposited on the upper surface of the P-GaN layer (107), an adhesive metal layer (202) is deposited on the upper surface of the reflective layer (201), a conductive substrate layer (301) is bonded to the upper surface of the adhesive metal layer (202), and an electrode metal layer (401) is formed on a portion of the lower surface of the N-AlGaN layer (104), and the position of the electrode metal layer (401) corresponds to the portion of the P-GaN layer (107).
7. The vertical structure deep ultraviolet light emitting diode according to claim 6, characterized in that: The reflective layer (201) is made of one or a combination of Ni, Au, Al, Pt, AuSn, Ti, Cr, DBR, and ODR.
8. The vertical structure deep ultraviolet light emitting diode according to claim 7, characterized in that: The adhesive metal layer (202) is made of any combination of Ni, Au, Al, Pt, AuSn, Ti, and Cr.
9. The vertical structure deep ultraviolet light emitting diode according to claim 8, characterized in that The conductive substrate layer (301) is made of metal or silicon.