CN114597296A

CN114597296A - Inverted ultraviolet light-emitting diode chip and preparation method thereof

Info

Publication number: CN114597296A
Application number: CN202210097954.3A
Authority: CN
Inventors: 尹涌; 易丁丁; 张琰琰; 陆香花
Original assignee: HC Semitek Zhejiang Co Ltd
Current assignee: HC Semitek Zhejiang Co Ltd
Priority date: 2022-01-27
Filing date: 2022-01-27
Publication date: 2022-06-07

Abstract

The disclosure provides a flip ultraviolet light emitting diode chip and a preparation method thereof, and belongs to the technical field of light emitting diodes. The n-AlGaN layer is set to comprise a transition n-AlGaN layer, a graphene layer and a contact n-AlGaN layer which are sequentially stacked. The graphene layer can protect the surface contacting the n-AlGaN layer, the graphene layer is realized by adopting laser stripping in the etching process, ohmic contact between the n-AlGaN layer and electrode metal is easier to form, the electrode of the finally obtained ultraviolet light-emitting diode chip can be reduced, the working voltage required by the ultraviolet light-emitting diode can be reduced, and the service life of the ultraviolet light-emitting diode can be prolonged. The graphene layer can also improve the quality of epitaxial materials, transmit electrons and expand current, and can also improve the light-emitting uniformity of the ultraviolet light-emitting diode.

Description

Inverted ultraviolet light-emitting diode chip and preparation method thereof

Technical Field

The disclosure relates to the technical field of light emitting diodes, in particular to a flip ultraviolet light emitting diode chip and a preparation method thereof.

Background

With the development of the application of the light emitting diode, the market demand of the ultraviolet light emitting diode is larger and larger, and the ultraviolet light emitting diode with the light emitting wavelength covering 210 and 400nm has incomparable advantages compared with the traditional ultraviolet light source. Ultraviolet light emitting diodes are commonly used in lighting, biomedical, anti-counterfeit, air, water purification, biochemical detection, high-density information storage, etc.

The flip-chip uv led chip is a common structure of a flip-chip uv led, and generally includes a substrate, a p electrode, an n electrode and an epitaxial layer, where the p electrode and the n electrode are spaced apart from each other and distributed on the substrate, and the epitaxial layer is stacked on the p electrode and the n electrode. The epitaxial layer comprises a p-GaN layer, a p-AlGaN layer, a multi-quantum well layer and an n-AlGaN layer which are sequentially stacked on a p electrode and an n electrode, wherein the p electrode is connected with the p-GaN layer, and the n electrode is connected with the n-AlGaN layer.

When the flip ultraviolet light emitting diode chip is manufactured, the n-AlGaN layer needs to be connected with the surface of an n electrode, a groove extending to the surface of the n-AlGaN layer needs to be etched from the p-GaN layer, and the surface of the n-AlGaN layer is affected by etching. Because the component of Al in the N-AlGaN layer is usually very high, the N vacancy generated by the N-AlGaN layer due to the influence of etching is used as a deep energy level compensation center rather than a shallow donor, the ohmic contact of the N-AlGaN layer is more difficult to form due to the high contact barrier, and the contact resistance between an electrode and an epitaxial layer is higher due to the difficult formation of the ohmic contact, so that the finally obtained ultraviolet light-emitting diode chip has extremely high required working voltage, the heat productivity of the ultraviolet light-emitting diode chip is large, and the service life of the ultraviolet light-emitting diode is influenced.

Disclosure of Invention

The embodiment of the disclosure provides a flip ultraviolet light-emitting diode chip and a preparation method thereof, which can reduce ohmic connection between an n electrode and an n-AlGaN layer so as to reduce the working voltage of the obtained ultraviolet light-emitting diode chip and prolong the service life of the ultraviolet light-emitting diode. The technical scheme is as follows:

the flip ultraviolet light emitting diode chip comprises a substrate, a p electrode, an n electrode and an epitaxial layer, wherein the p electrode and the n electrode are distributed on the substrate at intervals, the epitaxial layer is laminated on the p electrode and the n electrode, the epitaxial layer comprises a p-GaN layer, a p-AlGaN layer, a multi-quantum well layer, a transition n-AlGaN layer, a graphene layer, a contact n-AlGaN layer and a light emitting substrate which are sequentially laminated on the p electrode and the n electrode, the p electrode is connected with the p-GaN layer, the n electrode is connected with the contact n-AlGaN layer, and the graphene layer is etched by laser treatment.

Optionally, the graphene layer has a thickness of 20-60 nm.

Optionally, the doping concentration of Al and the doping concentration of Si in the contact n-AlGaN layer are respectively equal to the doping concentration of Al and the doping concentration of Si in the transition n-AlGaN layer.

Optionally, the thickness of the transition n-AlGaN layer ranges from 10 nm to 1000nm, and the thickness of the contact n-AlGaN layer ranges from 100nm to 2000 nm.

Optionally, the thickness of the contact n-AlGaN layer is larger than the thickness of the contact n-AlGaN layer.

Optionally, the epitaxial layer further includes an n-type ohmic contact metal layer stacked between the n-electrode and the contact n-AlGaN layer, where the n-type ohmic contact metal layer includes one or a combination of several of titanium, aluminum, nickel, gold, vanadium, and chromium, or an alloy thereof.

The present disclosure provides a method for manufacturing a flip ultraviolet light emitting diode chip, the method for manufacturing the flip ultraviolet light emitting diode chip includes:

providing a substrate and a light-emitting substrate;

sequentially growing a contact n-AlGaN layer, a graphene layer, a transition n-AlGaN layer, a multi-quantum well layer, a p-AlGaN layer and a p-GaN layer on the light-emitting substrate;

forming a groove extending to the surface of the graphene layer on the p-GaN layer;

laser removing the surface of the graphene layer exposed by the groove to expose the surface of the contact n-AlGaN layer;

forming an n electrode and a p electrode on the contact n-AlGaN layer and the p-GaN layer respectively;

bonding the n-electrode and the p-electrode to the substrate.

Optionally, the graphene layer is grown by using a physical vapor deposition device, and the growth temperature and the growth pressure of the graphene layer are 1000-1200 ℃ and 0.1-1atm respectively.

Optionally, the method for manufacturing a flip-chip ultraviolet light emitting diode chip further includes:

after the surface of the graphene layer exposed by the groove is removed by laser to expose the surface of the contact n-AlGaN layer, before an n electrode and a p electrode are respectively formed on the contact n-AlGaN layer and the p-GaN layer,

forming an n-type ohmic contact metal layer on the surface of the contact n-AlGaN layer;

annealing the n-type ohmic contact metal layer for 10-100s at the temperature of 600-1000 ℃.

The beneficial effects brought by the technical scheme provided by the embodiment of the disclosure include:

the flip ultraviolet light emitting diode chip comprises a substrate, p electrodes and n electrodes, wherein the epitaxial layer of the flip ultraviolet light emitting diode chip comprises a p-GaN layer, a p-AlGaN layer, a multi-quantum well layer, a transition n-AlGaN layer, a graphene layer, a contact n-AlGaN layer and a light emitting substrate which are sequentially stacked on the p electrodes and the n electrodes, the p electrodes are connected with the p-GaN layer, and the n electrodes are connected with the contact n-AlGaN layer. The conventional n-AlGaN layer is arranged to include a transition n-AlGaN layer, a graphene layer, and a contact n-AlGaN layer, which are stacked in this order. The graphene layer can protect the surface contacting the n-AlGaN layer, and the influence of etching on the n-AlGaN layer is reduced. The graphene layer is realized by adopting laser stripping in the etching process, the integrity of the surface contacting the n-AlGaN layer can be further ensured, ohmic contact between the contacting n-AlGaN layer and electrode metal is easier to form, the electrode of the finally obtained ultraviolet light-emitting diode chip can be reduced, the working voltage required by the ultraviolet light-emitting diode can be reduced, and the service life of the ultraviolet light-emitting diode can be prolonged. The graphene layer can also isolate the defects between two adjacent n-type layers so as to improve the quality of an epitaxial material grown on the graphene layer, and the crystal quality of the finally obtained ultraviolet light emitting diode chip can also be improved. The graphene layer can play a role in transmitting electrons and expanding current, and the light emitting uniformity of the ultraviolet light emitting diode can be improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present disclosure, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of an epitaxial wafer of a flip-chip ultraviolet light emitting diode according to an embodiment of the present disclosure;

fig. 2 is a schematic structural diagram of another flip-chip ultraviolet light emitting diode epitaxial wafer provided in the embodiment of the present disclosure;

fig. 3 is a flowchart of a flip-chip ultraviolet light emitting diode chip and a method for manufacturing the same according to an embodiment of the present disclosure;

fig. 4 and fig. 5 are schematic diagrams illustrating a manufacturing process of an ultraviolet light emitting diode chip according to an embodiment of the present disclosure;

fig. 6 is a flowchart of another flip-chip uv led chip and a method for manufacturing the same according to an embodiment of the present disclosure;

fig. 7 is an I-V characteristic curve corresponding to the flip-chip uv led provided in the embodiment of the present disclosure.

Detailed Description

To make the objects, technical solutions and advantages of the present disclosure more apparent, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

Fig. 1 is a schematic structural diagram of an epitaxial wafer of a flip-chip ultraviolet light emitting diode according to an embodiment of the present disclosure, and as can be seen from fig. 1, the embodiment of the present disclosure provides a flip-chip ultraviolet light emitting diode chip and a method for manufacturing the same, the flip-chip ultraviolet light emitting diode chip includes a substrate 1, a p-electrode 2, an n-electrode 3, and an epitaxial layer 4, the p-electrode 2 and the n-electrode 3 are distributed on the substrate 1at intervals, the epitaxial layer 4 is stacked on the p-electrode 2 and the n-electrode 3, the epitaxial layer 4 includes a p-GaN layer 401 and a p-AlGaN layer 402 sequentially stacked on the p-electrode 2 and the n-electrode 3, the LED structure comprises a multi-quantum well layer 403, a transition n-AlGaN layer 404, a graphene layer 405, a contact n-AlGaN layer 406 and a light-emitting substrate 407, wherein a p electrode 2 is connected with the p-GaN layer 401, an n electrode 3 is connected with the contact n-AlGaN layer 406, and the graphene layer 405 is etched by adopting laser treatment.

The flip-chip ultraviolet light emitting diode chip comprises a substrate 1, a p-AlGaN layer 402, a multi-quantum well layer 403, a transition n-AlGaN layer 404, a graphene layer 405, a contact n-AlGaN layer 406 and a light emitting substrate 407 which are sequentially laminated on the p electrode 2 and the n electrode 3, besides the substrate 1, the p electrode 3 and the n electrode 3, wherein the p electrode 2 is connected with the p-GaN layer 401, and the n electrode 3 is connected with the contact n-AlGaN layer 406. A conventional n-AlGaN layer is provided including a transition n-AlGaN layer 404, a graphene layer 405, and a contact n-AlGaN layer 406, which are sequentially stacked. The graphene layer 405 may protect the surface contacting the n-AlGaN layer 406, reducing the influence from etching that the contacting n-AlGaN layer 406 may be affected. The graphene layer 405 is formed by laser lift-off in the etching process, so that the integrity of the surface contacting the n-AlGaN layer 406 can be further ensured, ohmic contact between the n-AlGaN layer 406 and electrode metal can be formed more easily, the electrode of the finally obtained ultraviolet light emitting diode chip can be reduced, the working voltage required by the ultraviolet light emitting diode can be reduced, and the service life of the ultraviolet light emitting diode can be prolonged. The graphene layer 405 may also isolate defects between two adjacent n-type layers to improve the quality of an epitaxial material grown on the graphene layer 405, and the quality of a transistor of a finally obtained ultraviolet light emitting diode chip may also be improved. The graphene layer 405 itself can transmit electrons and expand current, and can also improve the light-emitting uniformity of the ultraviolet light-emitting diode.

It should be noted that, when the epitaxial layer 4 of the flip-chip ultraviolet light emitting diode chip is grown, in order to achieve good contact between the two electrodes and the epitaxial layer 4, a groove S extending to one side of the n-type semiconductor needs to be etched on one side of the p-type semiconductor, and both the chemical etching and the physical etching may have a certain influence on the roughness of the surface of the n-type semiconductor. In implementations provided by the present disclosure, the p-GaN layer 401 is a p-type semiconductor, and the graphene layer 405 and two adjacent layers of graphene layer 405 are n-type semiconductors.

Optionally, the graphene layer 405 is 20-60nm thick.

The thickness of the graphene layer 405 is within the above range, so that the obtained graphene layer 405 can be guaranteed to have good quality, the surface contacting the n-AlGaN layer 406 can be well protected, and the influence of etching or corrosion on the surface contacting the n-AlGaN layer 406 can be effectively reduced.

In other implementations provided by the present disclosure, the thickness of the graphene layer 405 may also be selected within the range of 1-100nm, which is not limited by the present disclosure.

Optionally, the Al composition in the contact n-AlGaN layer 406 is 40% -60%, and the doping concentration of Si in the contact n-AlGaN layer 406 is 1 × 10¹⁸-1*10²⁰cm^-3。

The doping concentration of the Al component and the Si in the contact n-AlGaN layer 406 is in the above range, so that the crystal quality of the contact n-AlGaN layer 406 is better, and stable supply and transmission of electrons can be ensured. The contact n-AlGaN layer 406 has fewer defects, so that ohmic contact resistance between the contact n-AlGaN layer 406 and an electrode is lower, the working voltage of the finally obtained ultraviolet light-emitting diode chip can be effectively reduced, and the service life of the ultraviolet light-emitting diode can be prolonged.

Illustratively, the doping concentration of Al and the doping concentration of Si in the contact n-AlGaN layer 406 are equal to the doping concentration of Al and the doping concentration of Si in the transition n-AlGaN layer 404, respectively.

The doping concentration of Al and the doping concentration of Si in the contact n-AlGaN layer 406 are respectively equal to the doping concentration of Al and the doping concentration of Si in the transition n-AlGaN layer 404, so that the obtained crystal quality of the contact n-AlGaN layer 406 and the crystal quality of the transition n-AlGaN layer 404 are both better, and the preparation efficiency of the ultraviolet light-emitting diode chip can be improved because parameters are not required to be adjusted basically when two n-AlGaN layers are actually grown.

Alternatively, the thickness of the transitional n-AlGaN layer 404 is in the range of 10-1000nm and the thickness of the contact n-AlGaN layer 406 is in the range of 100-2000 nm.

The thicknesses of the transition n-AlGaN layer 404 and the contact n-AlGaN layer 406 are respectively in the above ranges, so that the obtained transition n-AlGaN layer 404 and the obtained contact n-AlGaN layer 406 can be ensured to have better quality, and the crystal quality of epitaxial materials grown on the transition n-AlGaN layer 404 can be ensured to be better. It can also ensure that both the transition n-AlGaN layer 404 and the contact n-AlGaN layer 406 can provide enough electrons, ensure that the number of electrons finally emitting in the multiple quantum well layer 403 is sufficient, and also ensure the light emitting efficiency of the ultraviolet light emitting diode.

Optionally, the thickness of the contact n-AlGaN layer 406 is greater than the thickness of the contact n-AlGaN layer 406.

The thickness of the contact n-AlGaN layer 406 is larger than that of the contact n-AlGaN layer 406, so that the contact n-AlGaN layer 406 growing on the graphene layer 405 can have good crystal quality, and the stable growth of other epitaxial materials on the contact n-AlGaN layer 406 can be ensured. The thicker contact n-AlGaN layer 406 may also provide more electrons for recombination and light emission in the mqw layer 403.

Fig. 2 is a schematic structural diagram of another flip-chip uv led epitaxial wafer according to an embodiment of the present disclosure, and as can be seen from fig. 2, the flip-chip uv led chip may include a substrate 1, a p-electrode 2, an n-electrode 3, and an epitaxial layer 4, the p-electrode 2 and the n-electrode 3 are spaced apart from each other and distributed on the substrate 1, the epitaxial layer 4 is stacked on the p-electrode 2 and the n-electrode 3, the epitaxial layer 4 includes a p-GaN layer 401, a p-AlGaN layer 402, a multi-quantum well layer 403, a transition n-AlGaN layer 404, a graphene layer 405, a contact n-AlGaN layer 406, a buffer layer 408 and an light-emitting substrate 407 stacked on the p-electrode 2 and the n-GaN layer 401, the n-electrode 3 and the contact n-AlGaN layer 406 are connected, a surface of the p-GaN layer 401 has a groove S extending between the contact n-AlGaN layer 406, the n-electrode 3 is located on a surface of the contact n-AlGaN layer 406 exposed by the groove S, the graphene layer 405 is etched using a laser.

The epitaxial layer 4 may further include a p-type ohmic contact metal layer 409 disposed between the p-electrode 2 and the p-GaN layer 401, an n-type ohmic contact metal layer 410 disposed between the n-electrode 3 and the contact n-AlGaN layer 406, and an insulating layer 411, an orthographic area of the n-type ohmic contact metal layer 410 on the surface of the substrate 1 is larger than an orthographic area of the n-electrode 3 on the substrate 1, and an orthographic area of the p-type ohmic contact metal layer 409 on the surface of the substrate 1 is larger than an orthographic area of the p-electrode 2 on the surface of the substrate 1. The insulating layer 411 covers the side wall of the epitaxial layer 4, the surface of the p-type ohmic contact metal layer 409 close to the base, and the surface of the n-type ohmic contact metal layer 410 close to the substrate 1, two through holes corresponding to the n-electrode 3 and the p-electrode 2 are respectively arranged on the insulating layer 411, the n-electrode 3 and the p-electrode 2 are respectively located in the two through holes, and the n-electrode 3 and the p-electrode 2 are respectively connected with the n-type ohmic contact metal layer 410 and the p-type ohmic contact metal layer 409.

Exemplarily, the substrate 1 may be a circuit substrate 1 or a gallium nitride material base. Good contact with the n-electrode 3 and the p-electrode 2 can be achieved, and the preparation is easy.

Alternatively, the n-electrode 3 includes a chromium sublayer, a platinum sublayer, and a titanium sublayer laminated in this order on the substrate 1.

Alternatively, the p-electrode 2 includes a titanium sublayer, a gold sublayer, and an aluminum sublayer laminated in this order on the substrate 1. The n-electrode 3 and the p-electrode 2 with good quality can be obtained.

Illustratively, the insulating layer 411 may be a 2-3 micron thick silicon oxide layer. Good protection of structures such as ohmic contact metal layers can be achieved.

Illustratively, the n-type ohmic contact metal layer 410 includes one or a combination of titanium, aluminum, nickel, gold, vanadium, chromium, or an alloy thereof.

In the present disclosure, the n-type ohmic contact metal layer 410 and the p-type ohmic contact metal layer 409 are added to play a role of expanding current to a certain extent, so as to promote the light emitting uniformity of the ultraviolet light emitting diode chip. The n-type ohmic contact metal layer 410 comprising one or a combination of titanium, aluminum, nickel, gold, vanadium, chromium, or an alloy thereof may also ensure good contact between the n-type ohmic contact metal layer 410 and the contact n-AlGaN layer 406.

Illustratively, the n-type ohmic contact metal layer 410 may include a titanium sublayer, an aluminum sublayer, and a nickel sublayer sequentially stacked on the n-electrode 3. The resulting n-type ohmic contact metal layer 410 is of good quality.

In one implementation provided by the present disclosure, the structure of the n-type ohmic contact metal layer 410 and the p-type ohmic contact metal layer 409 may be the same, which facilitates the preparation of the n-type ohmic contact metal layer 410 and the p-type ohmic contact metal layer 409.

Alternatively the thickness of the p-GaN layer 401 may be 100-300 nm.

Alternatively, the P-type dopant in the P-AlGaN layer 402 may be Mg with a doping concentration of 10¹⁷cm^-3-10¹⁸cm^-3。

Illustratively, the p-AlGaN layer 402 is 1-1.5 microns thick. The crystal quality of the obtained ultraviolet light emitting diode chip can be ensured.

Alternatively, the multiple quantum well layer 403 includes several quantum barrier layers and quantum well layers that are alternately grown. The quantum well layer may be a GaN layer, and the quantum barrier layer may be an AlxGa1-xN (0< x <0.3) layer.

It should be noted that the structures of the transition n-AlGaN layer 404, the graphene layer 405, and the contact n-AlGaN layer 406 in fig. 2 are the same as the structures of the transition n-AlGaN layer 404, the graphene layer 405, and the contact n-AlGaN layer 406 in fig. 1, and therefore, the description thereof is omitted.

Illustratively, the buffer layer 408 includes an undoped AlGaN sublayer, an AlN/AlGaN multicycle stress modulation sublayer, and an AlN sublayer, which are sequentially stacked on the contact n-AlGaN layer 406.

The buffer layer 408 is configured to include an AlN sublayer, an AlN/AlGaN multi-period stress modulation sublayer, and a non-doped AlGaN sublayer, which are sequentially stacked, so that a good transition from the substrate to the contact n-AlGaN layer 406 can be achieved, the AlN/AlGaN multi-period stress modulation sublayer can also effectively release a certain stress, the crystal quality of the epitaxial material above the contact n-AlGaN layer 406 is improved, and the light emitting efficiency of the finally obtained ultraviolet light emitting diode epitaxial wafer is improved.

It should be noted that the AlN/AlGaN multicycle stress modulation sublayer is a superlattice structure.

Alternatively, the light-emitting substrate 407 may be a sapphire substrate. The light transmittance is good, and the requirement of stable light emission of the light emitting diode can be met.

The flip-chip uv led chip shown in fig. 2 is more specifically described with respect to the flip-chip uv led chip shown in fig. 1, and a buffer layer 408 is added between the light-emitting substrate 407 and the contact n-AlGaN layer 406, and an ohmic contact metal layer is added between the electrode and the epitaxial material that the electrode needs to contact, so that the quality of the obtained flip-chip uv led chip can be further improved as a whole, and the light-emitting uniformity of the flip-chip uv led can be improved.

Fig. 3 is a flowchart of a method for manufacturing a flip-chip ultraviolet light emitting diode chip according to an embodiment of the present disclosure, and as can be seen from fig. 3, the present disclosure provides a method for manufacturing a flip-chip ultraviolet light emitting diode chip, where the method for manufacturing a flip-chip ultraviolet light emitting diode chip includes:

s101: a substrate and a light-emitting substrate are provided.

S102: a buffer layer, a contact n-AlGaN layer, a graphene layer, a transition n-AlGaN layer, a multi-quantum well layer, a p-AlGaN layer and a p-GaN layer are sequentially grown on a light-emitting substrate.

S103: grooves extending to the surface of the graphene layer are formed on the p-GaN layer.

S104: the laser removes the surface of the graphene layer exposed by the recess to expose the surface contacting the n-AlGaN layer.

S105: and forming an n electrode and a p electrode on the contact n-AlGaN layer and the p-GaN layer respectively.

S106: and bonding the n electrode and the p electrode to the substrate.

The structure of the flip ultraviolet led chip obtained after the step S106 is performed can refer to fig. 1, and the technical effect corresponding to the manufacturing method shown in fig. 3 can refer to the technical effect corresponding to the flip ultraviolet led chip described in fig. 1.

Optionally, laser removing the surface of the graphene layer exposed by the recess to expose the surface contacting the n-AlGaN layer, includes: laser separation is carried out on the part of the graphene layer exposed by the groove and the contact n-AlGaN layer; and laser splitting the part of the graphene layer exposed by the groove and the part of the graphene layer covered by the transition n-AlGaN layer.

The obtained contact n-AlGaN layer can be ensured to have better surface quality, the quality of the side wall of the graphene layer is smoother, and the growth and the coverage of the insulating layer are facilitated. The graphene layer does not affect the contact n-AlGaN layer in the process of being cut.

For convenience of understanding, fig. 4 and fig. 5 are provided herein, fig. 4 and fig. 5 are schematic views illustrating a manufacturing process of an ultraviolet light emitting diode chip according to an embodiment of the present disclosure, and fig. 4 shows an epitaxial layer state of a flip-chip ultraviolet light emitting diode after step S103 is performed and before step S104 is performed, where a graphene layer is not etched or corroded; in fig. 5, after step S104 is performed, and before step S105 is performed, the epitaxial layer state of the flip-chip uv led is shown, where the graphene layer is subjected to laser processing, and the surface contacting the n-AlGaN layer is exposed, which can be used for n-electrode or different epitaxial material preparation.

Fig. 6 is a flowchart of another flip-chip ultraviolet light emitting diode chip and a method for manufacturing the same according to an embodiment of the disclosure, and referring to fig. 6, a method for manufacturing the flip-chip ultraviolet light emitting diode chip may include:

s201: a substrate and a light-emitting substrate are provided.

The substrate may be a gallium nitride substrate or a circuit substrate or a gallium arsenide substrate, which is not limited by this disclosure.

Alternatively, the light extraction substrate may be a sapphire substrate, and the thickness of the light extraction substrate may be 3-5 microns. The light emitting efficiency of the obtained flip ultraviolet light emitting diode can be ensured.

S202: a buffer layer, a contact n-AlGaN layer, a graphene layer, a transition n-AlGaN layer, a multi-quantum well layer, a p-AlGaN layer and a p-GaN layer are sequentially grown on a light-emitting substrate.

In step S202, the growth conditions of each epitaxial material may be as follows:

optionally, an AlN sublayer is grown on the substrate at the growth temperature of 1000-1400 ℃ and under the pressure of 50-100 mbar. The AlN sublayer has a thickness of 15 to 40 nm; before growing the undoped AlGaN layer, carrying out in-situ annealing treatment on the buffer layer (with the substrate) in an MOCVD (Metal Organic Chemical Vapor Deposition) equipment, wherein the temperature is 1000-1200 ℃, the pressure range is 150-500 Torr, and the time is 5-10 minutes; after the annealing is finished, the temperature of the MOCVD equipment is adjusted to 1000-1200 ℃, an undoped AlGaN layer with the thickness of 0.1-3.0 microns is grown, and the growth pressure is 50-200 Torr. The crystal quality of the obtained buffer layer can be ensured to be better.

Illustratively, the growth temperature of the contact n-AlGaN layer and the transition n-AlGaN layer is 1000-1100 ℃, and the growth pressure of the contact n-AlGaN layer and the transition n-AlGaN layer is 75-100 Torr. The quality of the obtained contact n-AlGaN layer and the transition n-AlGaN layer can be improved, impurities are promoted to be doped into the aluminum gallium nitrogen material under a low-pressure environment, and the concentration of electrons entering the luminescent layer is improved.

Optionally, the graphene layer is grown by using physical vapor deposition equipment, the deposition temperature of the graphene layer is 300-.

The deposition temperature and deposition pressure of the graphene layer are within the above range, so that the quality of the obtained graphene layer can be improved, and the crystal quality of the finally obtained electron transport layer can be improved. The graphene layer grows by adopting physical vapor deposition equipment, and the density of the graphene layer can be improved so as to effectively separate defects.

Optionally, the multiple quantum well layer comprises several quantum barrier layers and quantum well layers grown alternately. The quantum well layer may be a GaN layer, and the quantum barrier layer may be an AlxGa1-xN (0< x <0.3) layer. For example, the MQW layer is composed of 4 to 12 periods of GaN and AlxGa1-xN (0< x < 0.3). The thickness of the quantum well layer is about 3nm, the growth temperature range is 850-950 ℃, and the pressure range is between 100Torr and 300 Torr; the thickness of the quantum barrier layer is between 8nm and 20nm, the growth temperature is between 900 ℃ and 1000 ℃, and the growth pressure is between 50Torr and 200 Torr.

Optionally, a p-AlGaN layer is grown on the electron blocking layer with a growth temperature of 950-.

Optionally, the growth temperature of the p-GaN layer is 800-900 ℃. The crystal quality of the obtained p-GaN layer can be improved.

S203: grooves extending to the surface of the graphene layer are formed on the p-GaN layer.

It should be noted that the grooves extending from the p-GaN layer to the surface of the graphene layer may be formed by a photolithography process. The surface of the graphene layer is a surface of the graphene layer which is parallel to the substrate and farthest from the substrate.

S204: the laser removes the surface of the graphene layer exposed by the recess to expose the surface contacting the n-AlGaN layer.

Step S204 can refer to step S104 shown in fig. 3, and is not described herein again.

S205: and forming an n-type ohmic contact metal layer and a p-type ohmic contact metal layer on the contact n-AlGaN layer and the p-GaN layer respectively.

The n-type ohmic contact metal layer and the p-type ohmic contact metal layer can be prepared by matching a sputtering or deposition mode with a photoetching process.

S206: annealing the n-type ohmic contact metal layer and the p-type ohmic contact metal layer for 10-100s at the temperature of 600-1000 ℃.

The ohmic contact metal layer and the epitaxial material with lower contact resistance can be obtained by annealing under the conditions.

S207: and the surface of the n-type ohmic contact metal layer, the surface of the p-type ohmic contact metal layer and the side wall of the epitaxial layer are covered with an insulating layer, and the insulating layer is provided with two through holes respectively communicated with the surface of the n-type ohmic contact metal layer and the surface of the p-type ohmic contact metal layer.

Alternatively, the insulating layer is a silicon oxide material, and the through hole can be prepared by a photolithography process. An insulating layer with stable quality can be obtained.

S208: and forming an n electrode and a p electrode on the contact n-AlGaN layer and the p-GaN layer respectively, wherein the n electrode and the p electrode are positioned in the two through holes of the insulating layer respectively.

The preparation of the n electrode and the p electrode can be realized by sputtering or deposition in combination with a photoetching process. Illustratively, a photoresist layer is coated on the surface of the insulating layer, and electrode holes communicated to the two through holes on the insulating layer are formed on the photoresist layer after exposure, development and etching operations. And preparing an n electrode and a p electrode in the electrode hole.

S209: and bonding the n electrode and the p electrode to the substrate.

Alternatively, the bonding between the n-electrode, the p-electrode and the substrate can be obtained by applying pressure bonding through a press under the condition that the temperature is 100-300 ℃. The bonding quality can be ensured.

It should be noted that, the structure of the flip-chip uv led epitaxial wafer obtained after the step S209 is executed may refer to the structure of the flip-chip uv led epitaxial wafer shown in fig. 2.

It should be noted that, in the embodiments of the present disclosure, the epitaxial material may be mainly prepared by the MOCVD equipment. Wherein, high-purity H is adopted₂(Hydrogen) or high purity N₂(Nitrogen) or high purity H₂And high purity N₂The mixed gas of (2) is used as a carrier gas, high-purity NH₃As the N source, trimethylgallium (TMGa) and triethylgallium (TEGa) as gallium sources, silane (SiH4) as an N-type dopant, trimethylaluminum (TMAl) as an aluminum source, and magnesium diclomelate (CP)₂Mg) as a P-type dopant.

Fig. 7 may also be provided, where fig. 7 is an I-V characteristic curve corresponding to the flip-chip ultraviolet light emitting diode provided in the embodiment of the present disclosure, and fig. 7 is an I-V characteristic curve corresponding to the flip-chip ultraviolet light emitting diode shown in fig. 2, where I is a current and V is a voltage. The operating voltage of this chip at 20mA in fig. 7 is only 7V. In contrast to the chip of fig. 2 having only the n-type AlGaN layer, the chip manufactured by the prior art has an operating voltage of 8V when the current is 20 mA. The working voltage of the ultraviolet light emitting diode is effectively reduced in the present disclosure.

Although the present disclosure has been described with reference to specific embodiments, it will be understood by those skilled in the art that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the disclosure.

Claims

1. The flip ultraviolet light emitting diode chip is characterized by comprising a substrate, a p electrode, an n electrode and an epitaxial layer, wherein the p electrode and the n electrode are distributed on the substrate at intervals, the epitaxial layer is laminated on the p electrode and the n electrode, the epitaxial layer comprises a p-GaN layer, a p-AlGaN layer, a multi-quantum well layer, a transition n-AlGaN layer, a graphene layer, a contact n-AlGaN layer and a light emitting substrate which are sequentially laminated on the p electrode and the n electrode, the p electrode is connected with the p-GaN layer, the n electrode is connected with the contact n-AlGaN layer, and the graphene layer is etched by laser.

2. The flip chip uv led chip of claim 1, wherein the thickness of the graphene layer is 20-60 nm.

3. The flip-chip uv led chip of claim 1, wherein the contact n-AlGaN layer contains 40% to 60% Al, and the doping concentration of Si in the contact n-AlGaN layer is 1 x 10¹⁸-1*10²⁰cm^-3。

4. The flip-chip uv led chip according to any one of claims 1 to 3, wherein the doping concentration of Al and the doping concentration of Si in the contact n-AlGaN layer are respectively equal to the doping concentration of Al and the doping concentration of Si in the transition n-AlGaN layer.

5. The flip-chip uv led chip according to any one of claims 1-3, wherein the thickness of the transition n-AlGaN layer is in the range of 10-1000nm, and the thickness of the contact n-AlGaN layer is in the range of 100-2000 nm.

6. The flip chip uv led chip of any one of claims 1-3, wherein the contact n-AlGaN layer has a thickness greater than a thickness of the transition n-AlGaN layer.

7. The flip-chip uv led chip according to any one of claims 1 to 3, wherein the epitaxial layer further comprises an n-type ohmic contact metal layer stacked between the n-electrode and the contact n-AlGaN layer, the n-type ohmic contact metal layer comprising one or a combination of ti, al, ni, au, v, cr or an alloy thereof.

8. A preparation method of a flip ultraviolet light emitting diode chip is characterized by comprising the following steps:

providing a substrate and a light-emitting substrate;

bonding the n-electrode and the p-electrode to the substrate.

9. The method for manufacturing a flip chip UV LED chip according to claim 8, wherein the graphene layer is grown by physical vapor deposition equipment, and the growth temperature and the growth pressure of the graphene layer are 1000-1200 ℃ and 0.1-1atm, respectively.

10. The method for manufacturing a flip chip uv led chip as claimed in claim 8, wherein the method for manufacturing a flip chip uv led chip further comprises: