CN112786747A

CN112786747A - InGaN-based red light LED chip structure

Info

Publication number: CN112786747A
Application number: CN202110164568.7A
Authority: CN
Inventors: 庄文荣; 卢敬权; 钟宇宏; 孙明
Original assignee: Dongguan Sino Crystal Semiconductor Co ltd
Current assignee: Dongguan Sino Crystal Semiconductor Co ltd
Priority date: 2021-02-05
Filing date: 2021-02-05
Publication date: 2021-05-11

Abstract

The invention provides an InGaN-based red light LED chip structure, which comprises: an n-type GaN layer; the light emitting layer is positioned on the n-type GaN layer; the red light quantum dot layer is positioned on the light-emitting layer and is used for converting light emitted by the light-emitting layer into red light in a photoluminescence mode; the p-type GaN layer is positioned on the red light quantum dot layer; the first distributed Bragg reflector is positioned below the n-type GaN layer; the second distributed Bragg reflector is positioned above the p-type GaN layer; the first distributed Bragg reflector is used for reflecting blue light or simultaneously reflecting one of the blue light and the red light, and the second distributed Bragg reflector is used for reflecting the blue light or simultaneously reflecting the other of the blue light and the red light. The invention obtains the InGaN-based red light LED chip by a photoluminescence method, and solves the problem that the InGaN-based red light LED chip is difficult to obtain by the traditional electroluminescence method.

Description

InGaN-based red light LED chip structure

Technical Field

The invention belongs to the field of design and manufacture of semiconductor light-emitting devices, and particularly relates to an InGaN-based red light LED chip structure.

Background

With the continuous development of society and the vigorous advocation of the nation, the LED industry becomes one of the most active industries at present, and LED display screen products gradually enter into various fields of social life. Meanwhile, with the innovation and development of the LED display screen technology, the small-pitch seamless connection LED display screen with high resolution ratio in unit area becomes a mainstream product of the LED display screen, can display images and videos with higher definition, can display more videos and image pictures, and can realize seamless and arbitrary large-area splicing particularly in the aspect of image splicing.

In the current display screen industry, a fully flip-chip on board (cob) LED display screen has an excellent display effect, and the pixel pitch can be minimized to reach a micro pitch (P0.4). In the full flip COB products, it is necessary to use flip red leds (algainp), flip green leds (ingan), flip blue leds (ingan).

In the red, green and blue inverted LED, the inverted green LED and the inverted blue LED are mature products, and the manufacture and the use are simple. But the red LED is a quad LED with opaque GaAs substrate. To obtain the flip red LED, the GaAs substrate needs to be removed after the red wafer is bonded on the sapphire substrate, and the process is complex, the yield is low, and the cost is very high. In addition, flip-chip quad red LEDs often suffer device failure during use due to epitaxial film peeling. Therefore, a red InGaN LED of high In composition is receiving attention.

In order to make the light emitting color of the LED chip reach red, the indium content in the InGaN quantum well needs to be increased to 25-35% at least. In the current technology, InGaN quantum wells are grown on the c-plane of a GaN thin film. Because InGaN and GaN have larger lattice mismatch, the higher the In content In the InGaN material is, the larger the lattice mismatch ratio is. With increasing In composition, the compressive strain In the InGaN quantum wells gradually increases. On the one hand, stronger compressive strain leads to a decrease in crystal quality, reducing the internal quantum efficiency of the chip. On the other hand, the piezoelectric polarization is caused by the compressive strain, a built-in electric field is generated, the energy band of the semiconductor is inclined by the built-in polarization electric field, the electron-hole pair space separation and the wave function overlapping amount are reduced, the luminous efficiency is reduced, and the red shift of the luminous peak (absorption edge) is caused, and the phenomenon is called as the quantum confinement stark effect. Therefore, In the InGaN material grown In the c-plane, the higher the In component content, the greater the compressive stress, and the more difficult the InGaN material is grown. Generally, the highest In content of InGaN components grown on a GaN layer is about 15%, and the requirement of the In content In an InGaN quantum well of a red LED cannot be met. Therefore, the prior art is difficult to realize the InGaN-based red LED chip.

Disclosure of Invention

In view of the above-mentioned shortcomings of the prior art, the present invention is directed to provide an InGaN-based red LED chip structure, which is used to solve the problem that it is difficult to implement an InGaN-based red LED chip in the prior art.

In order to achieve the above and other related objects, the present invention provides an InGaN-based red LED chip structure, including: an n-type GaN layer; the light emitting layer is positioned on the n-type GaN layer; the red light quantum dot layer is positioned on the light-emitting layer and used for converting light emitted by the light-emitting layer into red light in a photoluminescence mode; the p-type GaN layer is positioned on the red light quantum dot layer; a first distributed Bragg reflector located below the n-type GaN layer; a second distributed Bragg reflector located above the p-type GaN layer; the first distributed Bragg reflector is used for reflecting blue light or simultaneously reflecting one of the blue light and the red light, and the second distributed Bragg reflector is used for reflecting the blue light or simultaneously reflecting the other of the blue light and the red light.

Optionally, the InGaN-based red LED chip structure further includes a substrate, the substrate is located below the n-type GaN layer, and the first distributed bragg reflector is located below the substrate.

Optionally, the InGaN-based red LED chip structure further includes a buffer layer and an intrinsic GaN layer stacked in sequence between the substrate and the n-type GaN layer, where the buffer layer includes one of a low-temperature GaN layer and an AlN layer.

Optionally, the InGaN-based red LED chip structure further includes a superlattice layer located between the n-type GaN layer and the light emitting layer, the superlattice layer includes one or more periodic superlattice structures including stacked InGaN/GaN or AlN/GaN, and the superlattice structures are used to improve stress conditions of subsequent epitaxial layers and/or form specific features, such as forming V-pits.

Optionally, the light emitting layer includes one or more periodic superlattice structures, and the superlattice structures include stacked InGaN/GaN, where InGaN is a well layer and has a thickness of 2-15 nm, GaN is an epitaxial layer and has a thickness of 8-30 nm, and the thickness of the epitaxial layer is greater than the thickness of the well layer, and light emitted by the light emitting layer is blue light by controlling the In content In the InGaN.

Optionally, the quantum dot layer is an InGaN quantum dot, a band gap of the InGaN quantum dot is between 1.6 and 2 electron volts, the quantum dot emits red light in a photoluminescence manner under excitation of blue light emitted by the light emitting layer, and a diameter of the quantum dot is 5 to 15 angstroms.

Optionally, the quantum dot layer and the p-type GaN layer repeat a plurality of cycles.

Optionally, the InGaN-based red LED chip structure further includes an electron blocking layer, the electron blocking layer is located between the light emitting layer and the quantum dot layer or between the quantum dot layer and the p-type GaN layer, and the electron blocking layer includes a p-type AlGaN layer.

Optionally, the second distributed bragg reflector further covers a side wall of the InGaN-based red LED chip structure.

Optionally, the InGaN-based red LED chip is a forward-mounted structure, and the first distributed bragg reflector is located below the n-type GaN layer and configured to reflect blue light and red light simultaneously, reflect the blue light back into the LED, increase the probability that the blue light is absorbed and converted into red light, and reflect the red light back into the LED, increase the probability that the red light exits from the second distributed bragg reflector; the second distributed Bragg reflector is located above the p-type GaN layer and used for reflecting blue light and reflecting the blue light back to the interior of the LED, so that the probability that the blue light is absorbed and converted into red light is increased, and the emergence of the red light is provided.

Optionally, the InGaN-based red LED chip is in a flip-chip structure, and the first distributed bragg reflector is located below the n-type GaN layer and configured to reflect blue light and reflect the blue light back into the LED, so as to increase the probability that the blue light is absorbed and converted into red light, and provide the emission of red light; the second distributed Bragg reflector is located above the p-type GaN layer and used for reflecting blue light and red light at the same time, reflecting the blue light back to the interior of the LED, increasing the probability that the blue light is absorbed and converted into the red light, reflecting the red light back to the interior of the LED, and increasing the probability that the red light exits from the first distributed Bragg reflector.

As mentioned above, the InGaN-based red LED chip structure of the present invention has the following beneficial effects:

the invention provides an InGaN-based red LED chip structure, which realizes a red LED chip by exciting a quantum dot layer to emit red light by blue light emitted by a light emitting layer. Meanwhile, the quantum dot layer is covered by the p-type GaN layer, so that the quantum dot layer is well protected. Furthermore, the quantum dot layer and the upper and lower distributed Bragg reflectors are arranged, the first distributed Bragg reflector is used for reflecting blue light or simultaneously reflecting one of the blue light and the red light, the second distributed Bragg reflector is used for reflecting the blue light or simultaneously reflecting the other of the blue light and the red light, and the absorption of the quantum dot layer on the blue light and the intensity of emitting the red light are enhanced through the back-and-forth reflection of the light, so that the light leakage of the blue light is reduced, and the emitting effect of the red light is improved. The invention obtains the InGaN-based red light LED chip by a photoluminescence method, and solves the problem that the InGaN-based red light LED chip is difficult to obtain by the traditional electroluminescence method.

Drawings

Fig. 1 is a schematic structural diagram of an InGaN-based red LED chip structure according to embodiment 1 of the present invention.

Fig. 2 is a schematic structural diagram of an InGaN-based red LED chip structure according to embodiment 2 of the present invention.

Fig. 3 is a schematic structural diagram of an InGaN-based red LED chip structure according to embodiment 3 of the present invention.

Description of the element reference numerals

100 substrate

200 buffer layer

300 intrinsic GaN layer

400 n type GaN layer

500 superlattice layer

600 light emitting layer

700 red quantum dot layer

800 electron blocking layer

900 p type GaN layer

1000. 2000 second distributed Bragg reflector

1100. 2100 first distributed bragg reflector

1200 current spreading layer

1300 p electrode

1400 n electrode

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

As in the detailed description of the embodiments of the present invention, the cross-sectional views illustrating the device structures are not partially enlarged in general scale for convenience of illustration, and the schematic views are only examples, which should not limit the scope of the present invention. In addition, the three-dimensional dimensions of length, width and depth should be included in the actual fabrication.

For convenience in description, spatial relational terms such as "below," "beneath," "below," "under," "over," "upper," and the like may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that these terms of spatial relationship are intended to encompass other orientations of the device in use or operation in addition to the orientation depicted in the figures. Further, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.

In the context of this application, a structure described as having a first feature "on" a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed in between the first and second features, such that the first and second features may not be in direct contact.

It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the drawings only show the components related to the present invention rather than being drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of each component in actual implementation may be changed arbitrarily, and the layout of the components may be more complicated.

Example 1

As shown in fig. 1, the present embodiment provides an InGaN-based red LED chip structure, which includes: an n-type GaN layer 400; a light emitting layer 600 on the n-type GaN layer 400; a red quantum dot layer 700 on the light emitting layer 600 for converting light emitted from the light emitting layer 600 into red light by photoluminescence; a p-type GaN layer 900 on the red quantum dot layer 700; a first distributed bragg reflector 1100 located below the n-type GaN layer 400; a second distributed bragg reflector 1000 located above the p-type GaN layer 900; the first distributed bragg reflector 1100 is configured to reflect blue light or reflect one of blue light and red light at the same time, and the second distributed bragg reflector 1000 is configured to reflect blue light or reflect the other of blue light and red light at the same time.

As shown in fig. 1, the InGaN-based red LED chip structure further includes a substrate 100, the substrate 100 is located under the n-type GaN layer 400, and the first distributed bragg reflector 1100 is located under the substrate 100, the substrate 100 may be, for example, a sapphire substrate, a silicon carbide substrate, or a silicon substrate. The InGaN-based red LED chip structure further comprises a buffer layer 200 and an intrinsic GaN layer 300 which are sequentially stacked, the buffer layer 200 is located between the substrate 100 and the n-type GaN layer 400, and the buffer layer 200 comprises one of a low-temperature GaN layer and an AlN layer. The low-temperature GaN layer may be grown by MOCVD, the AlN layer may be sputtered, and the buffer layer 200 may have a thickness of 15 to 30nm, for example, 20 nm. The thickness of the intrinsic GaN layer 300 may be 0.5 to 3 μm.

The thickness of the n-type GaN layer 400 is 0.5-3 μm.

As shown in fig. 1, the InGaN-based red LED chip structure further includes a superlattice layer 500, the superlattice layer 500 is located between the n-type GaN layer 400 and the light emitting layer 600, the superlattice layer 500 includes one or more periodic superlattice structures including stacked InGaN/GaN or AlN/GaN, and the superlattice structures are used to improve the stress condition of subsequent epitaxial layers and/or form specific features, such as forming V-pits.

The light emitting layer 600 comprises one or more periodic superlattice structures, the superlattice structures comprise stacked InGaN/GaN, wherein the InGaN is a well layer and has a thickness of 2-15 nm, the GaN is an epitaxial layer and has a thickness of 8-30 nm, the thickness of the epitaxial layer is larger than that of the well layer, and light emitted by the light emitting layer 600 is blue light by controlling the content of In the InGaN.

In this embodiment, the quantum dot layer is an InGaN quantum dot, the band gap of the InGaN quantum dot is between 1.6 to 2 ev, the quantum dot with the band gap between 1.6 to 2 ev can effectively emit red light by photoluminescence under the excitation of blue light emitted by the light emitting layer 600, and the diameter of the quantum dot is 5 to 15 angstroms. The quantum dot layer is well protected because the quantum dot layer is covered by the p-type GaN layer.

In this embodiment, the quantum dot layer and the p-type GaN layer 900 may be repeated for a plurality of cycles to improve the probability and efficiency of converting blue light into red light by the quantum dot layer.

As shown in fig. 1, the InGaN-based red LED chip structure further includes an electron blocking layer 800, the electron blocking layer 800 is located between the light emitting layer 600 and the quantum dot layer or between the quantum dot layer and the p-type GaN layer 900, and the electron blocking layer 800 includes a p-type AlGaN layer.

As shown in fig. 1, the second distributed bragg reflector 1000 also covers the sidewall of the InGaN-based red LED chip structure to prevent the sidewall of the LED chip from leaking blue light.

As shown in fig. 1, the InGaN-based red LED chip structure further includes a current spreading layer 1200 on the p-type GaN layer 900 and a p electrode 1300 on the current spreading layer 1200, the current spreading layer 1200 may be an ITO transparent conductive layer, etc., the InGaN-based red LED chip structure further includes an n electrode 1400 connected to the n-type GaN layer 400, and preferably, the p electrode 1300 is flush with a top surface of the n electrode 1400, so as to reduce a connection difficulty between the InGaN-based red LED chip structure and other circuits or devices, thereby improving a connection yield and reducing a cost.

As shown in fig. 1, specifically, the InGaN-based red LED chip structure is a forward-mounted structure, and includes a substrate 100, a buffer layer 200, an intrinsic GaN layer 300, an n-type GaN layer 400, a superlattice layer 500, a light emitting layer 600, a red quantum dot layer 700, an electron blocking layer 800, a p-type GaN layer 900, and a current spreading layer 1200, which are sequentially stacked, and further includes a p electrode 1300, an n electrode 1400, a first distributed bragg reflector 1100, and a second distributed bragg reflector 1000. The first distributed bragg reflector 1100 is located below the substrate 100, and is configured to reflect blue light and red light simultaneously, reflect the blue light back into the LED, increase the probability that the blue light is absorbed and converted into red light, reflect the red light back into the LED, and increase the probability that the red light exits from the second distributed bragg reflector 1000; the second distributed bragg reflector 1000 is located above the p-type GaN layer 900 and on a sidewall of the LED chip, and is configured to reflect blue light, reflect the blue light back into the LED, increase the probability that the blue light is absorbed and converted into red light, and provide red light for emission.

Example 2

As shown in fig. 2, the present embodiment provides an InGaN-based red LED chip structure, whose basic structure is as in embodiment 1, wherein the difference from embodiment 1 is that: the InGaN-based red LED chip is in a flip-chip structure, and the first distributed bragg reflector 2100 is located below the substrate 100 and configured to reflect blue light and reflect the blue light back to the LED, so as to increase the probability that the blue light is absorbed and converted into red light, and provide the emission of red light; the second distributed bragg reflector 2000 is located above the p-type GaN layer 900, and is configured to reflect blue light and red light simultaneously, reflect the blue light back into the LED, increase the probability that the blue light is absorbed and converted into red light, reflect the red light back into the LED, and increase the probability that the red light exits from the first distributed bragg reflector 2100. The InGaN-based red light LED chip structure of the embodiment adopts a flip structure, and the light emitting surface is the surface without being blocked by the electrode, so that the blocking of the electrode on emergent light can be avoided, and the luminous intensity of the LED chip is greatly improved.

Example 3

As shown in fig. 3, the present embodiment provides an InGaN-based red LED chip structure, the basic structure of which is as in embodiment 2, wherein the difference from embodiment 2 is that: the substrate 100 of the InGaN-based red LED chip structure is removed to expose the n-type GaN layer 400, as shown in fig. 3, the first distributed bragg reflector 2100 is located below the n-type GaN layer 400, and is configured to reflect blue light, reflect the blue light back to the inside of the LED, increase the probability that the blue light is absorbed and converted into red light, and provide the emission of red light; the second distributed bragg reflector 2000 is located above the p-type GaN layer 900, and is configured to reflect blue light and red light simultaneously, reflect the blue light back into the LED, increase the probability that the blue light is absorbed and converted into red light, reflect the red light back into the LED, and increase the probability that the red light exits from the first distributed bragg reflector 2100. The substrate 100 is removed in the embodiment, and the method can be applied to the Micro LED display field.

Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims

1. The InGaN-based red LED chip structure is characterized by comprising:

an n-type GaN layer;

the light emitting layer is positioned on the n-type GaN layer;

the red light quantum dot layer is positioned on the light-emitting layer and used for converting light emitted by the light-emitting layer into red light in a photoluminescence mode;

the p-type GaN layer is positioned on the red light quantum dot layer;

a first distributed Bragg reflector located below the n-type GaN layer;

a second distributed Bragg reflector located above the p-type GaN layer;

the first distributed Bragg reflector is used for reflecting blue light or simultaneously reflecting one of the blue light and the red light, and the second distributed Bragg reflector is used for reflecting the blue light or simultaneously reflecting the other of the blue light and the red light.

2. The InGaN-based red LED chip structure of claim 1, wherein: the InGaN-based red LED chip structure further comprises a substrate, wherein the substrate is located below the n-type GaN layer, and the first distributed Bragg reflector is located below the substrate.

3. The InGaN-based red LED chip structure of claim 2, wherein: the InGaN-based red light LED chip structure further comprises a buffer layer and an intrinsic GaN layer which are sequentially stacked, the buffer layer and the intrinsic GaN layer are located between the substrate and the n-type GaN layer, and the buffer layer comprises one of a low-temperature GaN layer and an AlN layer.

4. The InGaN-based red LED chip structure of claim 1, wherein: the InGaN-based red light LED chip structure further comprises a superlattice layer located between the n-type GaN layer and the light emitting layer, the superlattice layer comprises one or more periodic superlattice structures, the superlattice structures comprise stacked InGaN/GaN or AlN/GaN, and the superlattice structures are used for improving the stress condition of a subsequent epitaxial layer and/or forming a specific shape.

5. The InGaN-based red LED chip structure of claim 1, wherein: the light emitting layer comprises one or more periodic superlattice structures, the superlattice structures comprise stacked InGaN/GaN, wherein the InGaN is a well layer and has a thickness of 2-15 nm, the GaN is an epitaxial layer and has a thickness of 8-30 nm, the thickness of the epitaxial layer is larger than that of the well layer, and light emitted by the light emitting layer is blue light by controlling the content of In the InGaN.

6. The InGaN-based red LED chip structure of claim 1, wherein: the quantum dot layer is an InGaN quantum dot, the band gap of the InGaN quantum dot is between 1.6 and 2 electron volts, the quantum dot emits red light in a photoluminescence mode under the excitation of blue light emitted by the light emitting layer, and the diameter of the quantum dot is 5-15 angstroms.

7. The InGaN-based red LED chip structure of claim 1, wherein: the quantum dot layer and the p-type GaN layer repeat a plurality of cycles.

8. The InGaN-based red LED chip structure of claim 1, wherein: the InGaN-based red LED chip structure further comprises an electron blocking layer, the electron blocking layer is located between the light emitting layer and the quantum dot layer or between the quantum dot layer and the p-type GaN layer, and the electron blocking layer comprises a p-type AlGaN layer.

9. The InGaN-based red LED chip structure of claim 1, wherein: the second distributed Bragg reflector also covers the side wall of the InGaN-based red light LED chip structure.

10. The InGaN-based red LED chip structure of claim 1, wherein: the InGaN-based red LED chip structure is a forward mounting structure, the first distributed Bragg reflector is located below the n-type GaN layer and used for reflecting blue light and red light at the same time, the blue light is reflected back to the inside of the LED, the probability that the blue light is absorbed and converted into the red light is increased, the red light is reflected back to the inside of the LED, and the probability that the red light is emitted from the second distributed Bragg reflector is increased; the second distributed Bragg reflector is located above the p-type GaN layer and used for reflecting blue light and reflecting the blue light back to the interior of the LED, so that the probability that the blue light is absorbed and converted into red light is increased, and the emergence of the red light is provided.

11. The InGaN-based red LED chip structure of claim 1, wherein: the InGaN-based red LED chip structure is of a flip structure, the first distributed Bragg reflector is located below the n-type GaN layer and used for reflecting blue light and reflecting the blue light back to the inside of the LED, so that the probability that the blue light is absorbed and converted into red light is increased, and the emergence of the red light is provided; the second distributed Bragg reflector is located above the p-type GaN layer and used for reflecting blue light and red light at the same time, reflecting the blue light back to the interior of the LED, increasing the probability that the blue light is absorbed and converted into the red light, reflecting the red light back to the interior of the LED, and increasing the probability that the red light exits from the first distributed Bragg reflector.