CN115939281A - Light emitting diode and array for improving lateral light emitting and preparation method thereof - Google Patents

Abstract

The disclosure provides a Light Emitting Diode (LED) for improving lateral light extraction, an array and a preparation method thereof, and belongs to the technical field of photoelectron manufacturing. The light emitting diode includes: the light-shielding layer surrounds and covers the passivation layer; the side wall of the epitaxial layer is provided with a plurality of light guide parts, the light shading layer is internally provided with closed cavities which correspond to the light guide parts one by one, the closed cavities are opposite to the corresponding light guide parts, and the inner wall of each closed cavity, which is far away from the epitaxial layer, is used for reflecting light; in the direction from one side of the light shielding layer close to the epitaxial layer to one side of the light shielding layer far away from the epitaxial layer, the width of the closed cavity is integral multiple of the wavelength of light emitted by the epitaxial layer. The LED light source can improve the problem of lateral light emitting of the LED and improve the light emitting effect of the LED.

Description

Light emitting diode and array for improving lateral light extraction and preparation method thereof

Technical Field

The disclosure relates to the technical field of photoelectron manufacturing, and in particular to a Light Emitting Diode (LED) for improving lateral light emission, an array and a preparation method thereof.

Background

The Light Emitting Diode (LED) is a new product with great influence in the photoelectronic industry, has the characteristics of small volume, long service life, rich and colorful colors, low energy consumption and the like, and is widely applied to the fields of illumination, display screens, signal lamps, backlight sources, toys and the like.

In the related art, the light emitting diode generally includes an epitaxial layer and a light shielding layer located outside the epitaxial layer, and the light shielding layer shields and absorbs lateral light emitted from the epitaxial layer to reduce the lateral light emitted from the light emitting diode.

However, the light emitted from the side of the led is not completely blocked and absorbed by the light blocking layer, and there is still some light transmission, thereby affecting the light emitting effect of the led.

Disclosure of Invention

The embodiment of the disclosure provides a light emitting diode, an array and a preparation method thereof, which can improve the lateral light emitting problem of the light emitting diode and improve the light emitting effect of the light emitting diode. The technical scheme is as follows:

the disclosed embodiment provides a light emitting diode, which includes: the light-shielding layer surrounds and covers the passivation layer; the side wall of the epitaxial layer is provided with a plurality of light guide parts, the light shading layer is internally provided with closed cavities which correspond to the light guide parts one by one, the closed cavities are opposite to the corresponding light guide parts, and the inner wall of each closed cavity, which is far away from the epitaxial layer, is used for reflecting light; in a direction from one side of the light shielding layer close to the epitaxial layer to one side of the light shielding layer far away from the epitaxial layer, the width of the closed cavity is an integral multiple of the wavelength of light emitted by the epitaxial layer.

In one implementation of the embodiment of the present disclosure, the light guide portion is a protrusion, and a cross-sectional shape of the protrusion parallel to a top surface of the epitaxial layer is a triangle.

In an implementation manner of the embodiment of the present disclosure, one end of the light guide portion close to the closed cavity has a roughened area.

In another implementation of the disclosed embodiment, one end surface of the light guide portion is coplanar with the top surface of the epitaxial layer, and the other end surface of the light guide portion is coplanar with the bottom surface of the epitaxial layer.

In another implementation manner of the embodiment of the disclosure, the plurality of light guide portions are distributed at intervals along a circumferential direction of the epitaxial layer.

In another implementation manner of the embodiment of the present disclosure, regions on two side surfaces of the light shielding layer, which are opposite to the closed cavity, are roughened surfaces.

In another implementation manner of the embodiment of the present disclosure, the length of the closed cavity is 3 μm to 7 μm, and the length direction of the closed cavity is a direction perpendicular to the width direction of the closed cavity in a plane parallel to the side surface of the epitaxial layer.

In another implementation manner of the embodiment of the present disclosure, the shading layer includes a silica gel layer and an adhesive layer, carbon particles are embedded in the silica gel layer, a groove is formed in a side surface of the silica gel layer, and the adhesive layer is located in the side surface of the silica gel layer and covers the groove to form a closed cavity.

The embodiment of the present disclosure provides a light emitting diode array, which includes a plurality of light emitting diodes as described above, and the plurality of light emitting diode arrays are distributed.

The embodiment of the disclosure provides a preparation method of a light emitting diode, which comprises the following steps: providing a substrate; forming an epitaxial layer on the substrate, wherein the side wall of the epitaxial layer is provided with a plurality of light guide parts; forming a passivation layer on the epitaxial layer, wherein the passivation layer surrounds and covers the side wall of the epitaxial layer; the light guide layer is arranged on the passivation layer, the light shielding layer surrounds and covers the passivation layer, a closed cavity which corresponds to the light guide portion in a one-to-one mode is arranged in the light shielding layer, the closed cavity is opposite to the corresponding light guide portion, the inner wall, far away from the epitaxial layer, of the closed cavity is used for reflecting light, in the direction from one side, close to the epitaxial layer, of the light shielding layer to the side, far away from the epitaxial layer, of the light shielding layer, and the width of the closed cavity is an integral multiple of the wavelength of the light emitted by the epitaxial layer.

The beneficial effects brought by the technical scheme provided by the embodiment of the disclosure at least comprise:

the light emitting diode that this disclosed embodiment provided is through encircleing outside epitaxial layer and having set up the light shield layer, shelters from the absorption through the light shield layer to the light of side direction outgoing to reduce the side direction light-emitting that the lateral wall of epitaxial layer sent. Meanwhile, the light guide part is arranged on the side wall of the epitaxial layer, so that light emitted from the side wall of the epitaxial layer is concentrated at the position of the light guide part. The light shading layer is internally provided with the closed cavity, and the closed cavity and the light guide part are arranged oppositely, so that when photons are emitted from the light guide part and enter the light shading layer, due to half-wave loss, when light enters the closed cavity and is reflected from air (a medium with a relatively small refractive index) in the closed cavity to the inner wall (a medium with a relatively large refractive index) of the closed cavity, the reflected light and the light before reflection have an optical path difference of half-wave length. The width of the closed cavity is an integral multiple of the wavelength of the light emitted by the epitaxial layer, so that when the reflected light is reflected to the inner wall of the light shielding layer close to the epitaxial layer, the reflected light passes through the distance of the integral multiple of the wavelength, and at the moment, the reflected light and the light before reflection still have the optical path difference of half wavelength. Therefore, when the light and the reflected light which are incident to the closed cavity meet at the position, close to the inner wall of the epitaxial layer, of the closed cavity, the incident light and the reflected light have half-wavelength optical path difference, so that the interference of the incident light and the reflected light is cancelled, the light in the closed cavity is absorbed, the escape of photons is effectively reduced, and the problem of lateral light emission of the light emitting diode is further 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 a light emitting diode provided in an embodiment of the present disclosure;

FIG. 2 isbase:Sub>A cross-sectional view A-A provided in FIG. 1;

FIG. 3 is an enlarged view of a portion M of the structure provided in FIG. 2;

fig. 4 is a flowchart of a method for manufacturing a light emitting diode according to an embodiment of the present disclosure.

The various symbols in the figure are illustrated as follows:

10. an epitaxial layer; 101. a light guide part; 102. a top surface; 103. a bottom surface; 11. a first semiconductor layer; 12. a multi-quantum well layer; 13. a second semiconductor layer;

20. a passivation layer;

30. a light-shielding layer; 31. sealing the cavity;

41. a first electrode; 410. an electrode block; 42. a second electrode;

50. a transparent conductive layer.

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.

Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this disclosure belongs. The terms "first," "second," "third," and the like, as used in the description and in the claims of the present disclosure, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Also, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one. The word "comprise" or "comprises", and the like, means that the element or item listed before "comprises" or "comprising" covers the element or item listed after "comprising" or "comprises" and its equivalents, and does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", "top", "bottom", and the like are used merely to indicate relative positional relationships, which may also change accordingly when the absolute position of the object being described changes.

Fig. 1 is a schematic structural diagram of a light emitting diode according to an embodiment of the present disclosure. As shown in fig. 1, the light emitting diode includes: epitaxial layer 10, passivation layer 20 and light shielding layer 30.

As shown in fig. 1, the epitaxial layer 10 has a top surface 102 and a bottom surface 103 opposite to each other, and the bottom surface 103 is a light emergent surface of the epitaxial layer. Wherein passivation layer 20 is located on top surface 102 of epitaxial layer 10, and epitaxial layer 10 extends from top surface 102 to the sidewalls of epitaxial layer 10.

Fig. 2 isbase:Sub>A cross-sectional viewbase:Sub>A-base:Sub>A as provided in fig. 1. As shown in fig. 1 and 2, the passivation layer 20 surrounds and covers the sidewall of the epitaxial layer 10, and the light shielding layer 30 surrounds and covers the passivation layer 20 at the region surrounding and covering the sidewall of the epitaxial layer 10, i.e. the light shielding layer 30 also surrounds and covers the sidewall of the epitaxial layer 10.

Fig. 3 is a partial enlarged view of a point M provided in fig. 2. As shown in fig. 2 and 3, the side wall of the epitaxial layer 10 has a plurality of light guide portions 101, the light shielding layer 30 has closed cavities 31 corresponding to the light guide portions 101 one to one, the closed cavities 31 are opposite to the corresponding light guide portions 101, and an inner wall of the closed cavity 31 far away from the epitaxial layer 10 is used for reflecting light.

As shown in fig. 2, the width d of the closed cavity 31 is an integral multiple of the wavelength of light emitted from the epitaxial layer 10 in a direction from the side of the light-shielding layer 30 close to the epitaxial layer 10 to the side of the light-shielding layer 30 far from the epitaxial layer 10.

The wavelengths of light of different colors are range values, and in determining the wavelength of light, a wavelength most easily perceived by the human eye is generally selected from the range values as the wavelength of the color.

Illustratively, when the light emitted from the epitaxial layer is blue light, the wavelength of the blue light may be selected to be 460nm, and the width of the corresponding closed cavity 31 may be 0.46 μm or 0.92 μm.

Illustratively, when the light emitted from the epitaxial layer is red light, the wavelength of the red light may be selected to be 620nm, and the width of the corresponding closed cavity 31 may be 0.62 μm.

For example, when the light emitted from the epitaxial layer is green light, the wavelength of the green light may be selected to be 525nm, and the width of the corresponding closed cavity 31 may be 0.525 μm.

The light emitting diode provided by the embodiment of the disclosure is provided with the light shielding layer by surrounding the epitaxial layer, and the light emitted from the lateral direction is shielded and absorbed by the light shielding layer, so that the lateral light emitted from the side wall of the epitaxial layer is reduced. Meanwhile, the light guide part is arranged on the side wall of the epitaxial layer, so that light emitted from the side wall of the epitaxial layer is concentrated at the position of the light guide part. The closed cavity is arranged in the light shielding layer, and the closed cavity and the light guide part are arranged oppositely, so that when photons are emitted from the light guide part and enter the light shielding layer, due to half-wave loss, when light enters the closed cavity and is reflected towards the inner wall (medium with relatively large refractive index) of the closed cavity from air (medium with relatively small refractive index) in the closed cavity, the reflected light and the light before reflection have optical path difference of half-wave length. The width of the closed cavity is an integral multiple of the wavelength of the light emitted by the epitaxial layer, so that when the reflected light is reflected to the inner wall of the light shielding layer close to the epitaxial layer, the reflected light passes through the distance of the integral multiple of the wavelength, and at the moment, the reflected light and the light before reflection still have the optical path difference of half wavelength. Therefore, when the light and the reflected light which are incident to the closed cavity meet at the position, close to the inner wall of the epitaxial layer, of the closed cavity, the incident light and the reflected light have half-wavelength optical path difference, so that the interference of the incident light and the reflected light is cancelled, the light in the closed cavity is absorbed, the escape of photons is effectively reduced, and the problem of lateral light emission of the light emitting diode is further improved.

In the embodiment of the disclosure, as shown in fig. 3, the closed cavity is a hole structure in the light shielding layer, and an opening of the hole structure is blocked. Namely, the closed cavity is a closed cavity in the light shielding layer.

Alternatively, as shown in fig. 2, the length L of the closed cavity is 3 μm to 7 μm, and the length direction of the closed cavity 31 is a direction perpendicular to the width direction of the closed cavity 31 in a plane parallel to the side surface of the epitaxial layer 10.

In the embodiment of the present disclosure, the length of the light guide portion in the length direction of the closed cavity may also be 3 μm to 7 μm. Thus, setting the length of the closed cavity within the above range can ensure that the size of the closed cavity 31 is not smaller than that of the light guide portion 101, so that most of light emitted from the light guide portion 101 enters the closed cavity 31.

Exemplarily, the length L of the closed cavity is 5 μm, and the length of the light guide portion in the length direction of the closed cavity is 3 μm.

Alternatively, as shown in fig. 2, the light guide part 101 is a protrusion having a triangular shape in a cross-section parallel to the top surface of the epitaxial layer.

Because the refracting index of epitaxial layer is higher than peripheral passivation layer, light is difficult to be gone out from the lateral wall transmission of epitaxial layer, and will lead the light part setting to be the protruding back of sharp horn shape, although protruding lateral wall position is difficult to transmit light yet, at bellied most advanced position, light is equivalent to vertical direction directive passivation layer, and light is followed bellied most advanced position and is gone out perpendicularly this moment, consequently, light can reflect and assemble at bellied most advanced emergence through bellied lateral wall, realizes improving the emergent volume purpose of light.

In other embodiments, the cross-sectional shape of the light guide portion 101 may be other shapes, and the embodiment of the present disclosure is not limited.

Alternatively, one end surface of light guide 101 is coplanar with top surface 102 of epitaxial layer 10 and the other end surface of light guide 101 is coplanar with bottom surface 103 of epitaxial layer 10.

Wherein the thickness of the light guide portion 101 is the same as the thickness of the epitaxial layer 10 in a direction perpendicular to the top surface 102 of the epitaxial layer 10. This increases the size of the light guide portion 101 to the maximum, and ensures that photons near the light guide portion 101 on the epitaxial layer 10 are concentrated on the light guide portion 101.

Alternatively, as shown in fig. 2, the plurality of light guide portions 101 are spaced apart from each other in the circumferential direction of the epitaxial layer 10.

By arranging the light guide parts 101 and enabling the light guide parts 101 to be distributed along the circumferential direction of the epitaxial layer, the combined structure of the light guide part and the closed cavity which can perform extinction is arranged at each position in the circumferential direction of the epitaxial layer, and therefore most of lateral light outgoing on the epitaxial layer is eliminated.

Optionally, as shown in fig. 3, one end of the light guide part 101 near the closed cavity 31 has a roughened area.

The roughness of the surface of the roughened region is greater than that of the surface of the light guide part 101 that has not been roughened. Therefore, the light emitting rate of the light in the roughened area can be increased, and more light can be emitted from the roughened area of the light guide part 101 to be shielded and absorbed at the shielding layer.

Illustratively, as shown in fig. 3, the roughened region may be a surface having serrations.

Optionally, as shown in fig. 3, regions on two side surfaces of the light shielding layer 30 opposite to the closed cavity 31 are roughened surfaces.

The coarsening processing area is an area on the side face of the light shield layer opposite to the closed cavity, and areas except the coarsening processing area in the light shield layer are areas which are not coarsened. The roughness of the surface of the roughened area on the light-shielding layer is greater than that of the surface of the non-roughened area on the light-shielding layer.

The light shielding layer 30 is provided with a roughened surface on the side surface close to the epitaxial layer 10, so that the light emitting rate of light in the roughened region can be improved, more light can enter the shielding layer and can be extinguished in the closed cavity 31, and the escape of photons can be reduced.

The side face of the light shielding layer 30 far away from the epitaxial layer 10 is provided with the roughened surface, so that mirror reflection can be reduced, when light rays are emitted from the closed cavity 31 and pass through the roughened surface, the roughened surface can hit the emitting direction of the light rays, the light rays are prevented from being emitted to other light emitting diodes in a concentrated manner, and light crosstalk is reduced.

Illustratively, as shown in fig. 3, the roughened region may be a surface having serrations.

In the embodiment of the present disclosure, the light shielding layer 30 includes a silica gel layer and an adhesive layer, the silica gel layer is embedded with carbon particles, the side of the silica gel layer has a groove, and the adhesive layer is located the side of the silica gel layer and covers the groove to enclose into the enclosed cavity 31.

The black carbon particles are embedded into the silica gel layer to make the light shielding layer 30 black, so that the black silica gel layer is used for absorbing photons, and the photons are prevented from further escaping outwards. Set up viscose layer shutoff recess in the side on silica gel layer to let the light shield layer can form inclosed cavity.

The thickness of the silica gel layer may be 7 μm, and for example, when the light emitted from the epitaxial layer is blue light, the width of the closed cavity 31 may be 0.46 μm, and at this time, the thicknesses of the sidewall of the groove close to the epitaxial layer and the sidewall of the groove far from the epitaxial layer may be (7 μm-0.46 μm)/2 =3.27 μm.

Therefore, the thickness of the side wall of the groove is far larger than the width d of the groove, so that when the groove is etched on the side surface of the light shielding layer along the direction perpendicular to the substrate subsequently, a sufficient area can be formed on the side surface of the light shielding layer to form a mask structure, and the side wall of the groove is not easy to etch.

In the embodiment of the disclosure, the light-reflecting rate of the light-shielding layer formed after the black carbon particles are embedded in the silica gel layer is 8% to 11%, and partial light can be reflected at the side wall of the groove to form reflected light for extinction.

Wherein, the thickness of the adhesive layer can be 2 μm, and the adhesive layer can be a silica gel layer.

Alternatively, as shown in fig. 1, the epitaxial layer 10 includes a first semiconductor layer 11, a multiple quantum well layer 12, and a second semiconductor layer 13, which are sequentially stacked.

Illustratively, the first semiconductor layer 11 is a silicon-doped n-type GaN layer. The thickness of the n-type GaN layer may be 0.5 μm to 3 μm.

Illustratively, the multiple quantum well layer 12 includes InGaN quantum well layers and GaN quantum barrier layers that are alternately grown. Wherein the multiple quantum well layer 12 may include InGaN quantum well layers and GaN quantum barrier layers alternately stacked for 3 to 8 periods.

As an example, in the embodiment of the present disclosure, the multiple quantum well layer 12 includes 5 periods of InGaN quantum well layers and GaN quantum barrier layers that are alternately stacked.

Illustratively, the thickness of the multiple quantum well layer 12 may be 150nm to 200nm.

Illustratively, the second semiconductor layer 13 is a magnesium-doped p-type GaN layer. The thickness of the p-type GaN layer may be 0.5 μm to 3 μm.

Optionally, the light emitting diode further includes a first electrode 41, a second electrode 42 and a transparent conductive layer 50, the first electrode 41 is located on a surface of the first semiconductor layer 11 away from the second semiconductor layer 13, the transparent conductive layer 50 is located on the second semiconductor layer 13, the passivation layer 20 is located on the transparent conductive layer 50, a through hole is arranged on the transparent conductive layer 50, and the second electrode 42 is located in the through hole and connected to the transparent conductive layer 50.

The transparent conductive layer 50 is Indium Tin Oxide (ITO film for short). The indium tin oxide film layer has good transmissivity and low resistivity, is convenient for carrier conduction, and improves the injection efficiency.

Illustratively, the transparent conductive layer 50 has a thickness of 800 to 1200 angstroms.

The thickness of the transparent conductive layer 50 affects the light transmission effect and the resistance value of the transparent conductive layer 50, and if the thickness is too low or too high, the light transmission effect of the transparent conductive layer 50 is poor, which is not favorable for injecting carriers. In this thickness range, the transparent conductive layer 50 with high light transmittance and low resistance can be formed, which is beneficial to improving the light emitting effect of the light emitting diode.

As an example, in the disclosed embodiment, the thickness of the transparent conductive layer 50 is 1000 angstroms.

In the embodiment of the present disclosure, the passivation layer 20 may be a polysilicon layer, and the use of the polysilicon layer as the passivation layer 20 can effectively isolate the external environment from the epitaxial layer 10 and the transparent conductive layer 50, thereby preventing the short circuit and the leakage.

Illustratively, the thickness of passivation layer 20 is 300 angstroms to 1000 angstroms. For example, the passivation layer 20 has a thickness of 600 angstroms.

In the embodiment of the present disclosure, the first semiconductor layer 11 is an n-type layer, and the first electrode 41 is an n-type electrode. The second semiconductor layer 13 is a p-type layer and the second electrode 42 is a p-type electrode.

Alternatively, as shown in fig. 1, the first electrode 41 includes a plurality of electrode blocks 410, and the plurality of electrode blocks 410 are distributed on the surface of the first semiconductor layer 11 at intervals.

By designing the first electrode 41 as a plurality of discrete electrode blocks 410, the first electrode 41 can be made conductive by only making a small number of electrode blocks 410. In the embodiment of the present disclosure, the bottom surface of the light emitting diode is a light exit surface, which can also prevent the first electrode 41 from shielding light to the maximum extent, thereby ensuring the light exit effect of the micro light emitting diode chip.

In the disclosed embodiment, the electrode block 410 may have a cylindrical shape.

Alternatively, the first electrode 41 includes a chromium layer, a tin-indium alloy layer, and an indium layer sequentially stacked on the first semiconductor layer 11. The indium-tin alloy layer is arranged between the chromium layer and the indium layer, and the indium-tin alloy layer contains indium metal, so the indium-tin alloy layer and the indium layer can be well connected together to improve the shape-retaining effect of the three laminated metal layers.

Wherein the thickness of the chromium layer in the first electrode 41 may be 100to 300 angstroms, the thickness of the tin-indium alloy layer may be 8000 to 12000 angstroms, and the thickness of the indium layer may be 8000 to 12000 angstroms.

As an example, in the embodiments of the present disclosure, the thickness of the chromium layer is 200 angstroms, the thickness of the tin-indium alloy layer is 10000 angstroms, and the thickness of the indium layer is 10000 angstroms.

Alternatively, the second electrode 42 has a block shape, and the second electrode 42 is opposite to the middle portion of the transparent conductive layer 50. Therefore, the current can flow in the central area of the micro light-emitting diode chip in a more important way, and the luminous intensity of the central area is improved.

Illustratively, the second electrode 42 is rectangular. The rectangular second electrode 42 can fully cover the central region of the micro led chip to ensure the light emitting intensity of the edge region of the micro led chip.

It should be noted that, in other implementations, the second electrode 42 may also be in various shapes such as a circle, a polygon, and the like, and the embodiment of the disclosure is not limited.

Alternatively, the second electrode 42 includes a chromium layer, a titanium layer, a gold layer, and an indium layer sequentially stacked on the surface of the transparent conductive layer 50.

Among them, the thickness of the chrome layer in the second electrode 42 may be 100to 300 angstroms, the thickness of the titanium layer may be 100to 300 angstroms, the thickness of the gold layer may be 2000 to 4000 angstroms, and the thickness of the indium layer may be 4000 to 6000 angstroms.

As an example, in the disclosed embodiment, the thickness of the chromium layer in the second electrode 42 is 200 angstroms, the thickness of the titanium layer is 200 angstroms, the thickness of the gold layer is 3000 angstroms, and the thickness of the indium layer is 5000 angstroms.

The embodiment of the present disclosure provides a light emitting diode array, which includes a plurality of light emitting diodes as described above, and the plurality of light emitting diode arrays are arranged. In the light emitting diode array, the light shielding layer capable of reducing the side light emission is arranged on a single light emitting diode, so that the problem of optical crosstalk caused by the side light emission among the plurality of light emitting diodes can be solved.

Illustratively, the light emitting diode array may be a display panel.

Fig. 4 is a flowchart of a method for manufacturing a light emitting diode according to an embodiment of the present disclosure. As shown in fig. 4, the preparation method includes:

step S11: a substrate is provided.

Step S12: an epitaxial layer is grown on a substrate.

Wherein, the side wall of the epitaxial layer is provided with a plurality of light guide parts.

Step S13: a passivation layer is formed on the epitaxial layer.

Wherein, the passivation layer surrounds and wraps the side wall of the epitaxial layer.

Step S14: and forming a light shielding layer on the passivation layer.

As shown in fig. 1 and 2, the light-shielding layer surrounds and covers the passivation layer, the light-shielding layer is provided with closed cavities corresponding to the light-guiding portions one to one, the closed cavities are opposite to the corresponding light-guiding portions, and in a direction from one side of the light-shielding layer close to the epitaxial layer to one side of the light-shielding layer far away from the epitaxial layer, the width of the closed cavities is an integral multiple of the wavelength of light emitted by the epitaxial layer.

The light emitting diode provided by the embodiment of the disclosure is provided with the light shielding layer by surrounding the epitaxial layer, and the light emitted from the lateral direction is shielded and absorbed by the light shielding layer, so that the lateral light emitted from the side wall of the epitaxial layer is reduced. Meanwhile, the light guide part is arranged on the side wall of the epitaxial layer, so that light emitted from the side wall of the epitaxial layer is concentrated at the position of the light guide part. The closed cavity is arranged in the light shielding layer, and the closed cavity and the light guiding part are arranged oppositely, so that when photons are emitted from the light guiding part and enter the light shielding layer, because the width of the closed cavity is integral multiple of the wavelength of light emitted by the epitaxial layer, and the light is reflected from air (medium with relatively small refractive index) of the closed cavity to the light shielding layer (medium with relatively large refractive index), the optical path of half wavelength can be lost, therefore, the light can have half wavelength loss after being reflected by the inner wall of the closed cavity, and thus, the light incident into the closed cavity and the light reflected by the inner wall of the closed cavity can form an optical path difference of odd times of half wavelength, so that the incident light and the reflected light are cancelled, the light in the closed cavity is absorbed, the escape of the photons is effectively reduced, and the problem of side light emission of the light-emitting diode is further improved.

In step S11, the substrate is a sapphire substrate, a silicon substrate, or a silicon carbide substrate. The substrate can be a flat substrate or a patterned substrate.

As an example, in the embodiments of the present disclosure, the substrate is a sapphire substrate. The sapphire substrate is a common substrate, the technology is mature, and the cost is low. The method can be embodied as a patterned sapphire substrate or a sapphire flat sheet substrate.

The sapphire substrate may be pretreated, placed in an MOCVD (Metal-organic Chemical Vapor Deposition) reaction chamber, and subjected to a baking process for 12 to 18 minutes. As an example, in the embodiment of the present disclosure, the baking process was performed on the sapphire substrate for 15 minutes.

Specifically, the baking temperature may be 1000 ℃ to 1200 ℃, and the pressure in the MOCVD reaction chamber during baking may be 100mbar to 200mbar.

Growing the first semiconductor layer in step S12 may include: a first semiconductor layer was formed on a sapphire substrate by the MOCVD technique.

The first semiconductor layer is an n-type GaN layer. The growth temperature of the n-type GaN layer may be 1000 ℃ to 1100 ℃, and the growth pressure of the n-type GaN layer may be 100torr to 300torr.

Alternatively, the n-type GaN layer has a thickness of 0.5 μm to 3 μm. For example, the thickness of the n-type GaN layer may be 1 μm.

Growing the multiple quantum well layer in step S12 may include: a multiple quantum well layer is formed on the n-type GaN layer.

The multiple quantum well layer comprises InGaN quantum well layers and GaN quantum barrier layers which are alternately grown. Wherein the multiple quantum well layer may include InGaN quantum well layers and GaN quantum barrier layers alternately stacked for 3 to 8 periods.

As an example, in the embodiments of the present disclosure, the multiple quantum well layer includes 5 periods of InGaN quantum well layers and GaN quantum barrier layers that are alternately stacked.

Alternatively, the thickness of the multiquantum well layer may be 150nm to 200nm.

When the multi-quantum well layer is grown, the pressure of the MOCVD reaction chamber is controlled at 200torr. When the InGaN quantum well layer is grown, the temperature of the reaction chamber is 760 ℃ to 780 ℃. When the GaN quantum barrier layer grows, the temperature of the reaction chamber is 860 ℃ to 890 ℃. The quality of the multi-quantum well layer grown under the process condition is good.

Growing the second semiconductor layer in step S12 may include: and forming a p-type GaN layer on the multi-quantum well layer.

Alternatively, the p-type GaN layer has a thickness of 0.5 μm to 3 μm. For example, the thickness of the p-type GaN layer is 1 μm.

When the p-type GaN layer is grown, the growth pressure of the p-type GaN layer may be 200Torr to 600Torr and the growth temperature of the p-type GaN layer may be 800 ℃ to 1000 ℃.

And then, etching through the epitaxial layer in an etching mode, and forming a plurality of sharp horn-shaped bulges on the side wall of the epitaxial layer.

Then, the tip of the projection is roughened. And in the roughening treatment process, etching and roughening are carried out in a mode of protecting other areas by adopting photoresist.

Before step S13, a transparent conductive layer may be formed on the surface of the second semiconductor layer.

Illustratively, the transparent conductive layer has a thickness of 800 to 1200 angstroms.

The thickness of the transparent conductive layer affects the light transmission effect and the resistance value of the transparent conductive layer, and if the thickness is too low or too high, the light transmission effect of the transparent conductive layer is poor, which is not beneficial to the injection of carriers. In this thickness range, a transparent conductive layer with high light transmittance and low resistance can be formed, which is beneficial to improving the light emitting effect of the light emitting diode.

As an example, in embodiments of the present disclosure, the transparent conductive layer has a thickness of 1000 angstroms.

The forming of the passivation layer at step S13 may include: and depositing a polycrystalline silicon layer on the surface of the transparent conducting layer. And oxidizing the polysilicon layer by adopting a pressure oxidation mode to form a passivation layer.

Illustratively, the polysilicon layer has a thickness of 300 angstroms to 1000 angstroms. The polysilicon layer has a thickness of 500 angstroms, for example. By doping oxygen in the polysilicon layer, the density of the polysilicon layer can be improved, and the third polysilicon layer is prevented from being too sparse in crystals.

In the second step, oxygen can be sufficiently diffused into the polycrystalline silicon by pressure oxidation to achieve sufficient oxidation.

Wherein the formed passivation layer has a through hole exposing the transparent conductive layer.

Step S13 may be followed by: and forming a second electrode on the surface of the transparent conductive layer through the through hole.

The second electrode comprises a chromium layer, a titanium layer, a gold layer and an indium layer which are sequentially laminated on the surface of the transparent conducting layer.

Wherein, the thickness of the chromium layer in the second electrode can be 100to 300 angstroms, the thickness of the titanium layer can be 100to 300 angstroms, the thickness of the gold layer can be 2000 to 4000 angstroms, and the thickness of the indium layer can be 4000 to 6000 angstroms.

As an example, in the embodiments of the present disclosure, the thickness of the chromium layer in the second electrode is 200 angstroms, the thickness of the titanium layer is 200 angstroms, the thickness of the gold layer is 3000 angstroms, and the thickness of the indium layer is 5000 angstroms.

The following steps may be included after step S13:

and step one, bonding the prepared epitaxial layer on the double-polished sapphire substrate, and enabling the passivation layer and the second electrode to face the double-polished sapphire substrate.

The bonding material may be photoresist, SOG (Silicon On Glass, silicon-Glass bonding structure), and silica gel.

And secondly, removing the sapphire substrate below the first semiconductor layer by laser lift-off, and forming a first electrode on the surface of the first semiconductor layer far away from the second semiconductor layer.

Wherein, the wavelength of the laser is 266 nm, and Ga metal needs to be rinsed by acid after stripping.

The method specifically comprises the following steps: and evaporating a first electrode on the surface of the first semiconductor layer. The first electrode comprises a chromium layer, a tin-indium alloy layer and an indium layer which are sequentially stacked on the first semiconductor layer.

Wherein the thickness of the chromium layer in the first electrode may be 100to 300 angstroms, the thickness of the tin-indium alloy layer may be 8000 to 12000 angstroms, and the thickness of the indium layer may be 8000 to 12000 angstroms.

As an example, in the embodiments of the present disclosure, the thickness of the chromium layer is 200 angstroms, the thickness of the tin-indium alloy layer is 10000 angstroms, and the thickness of the indium layer is 10000 angstroms.

Step S14 may include: firstly, a silica gel layer is formed on the surface of the passivation layer, and carbon particles are embedded in the silica gel layer.

The silica gel layer with the required thickness can be formed on the surface of the passivation layer in a layer-by-layer coating mode.

And then, setting a mask structure, and etching the position where the closed cavity is required to be formed in a photoetching mode to obtain the silica gel layer with a plurality of grooves.

Wherein, during the photoetching, the etching is carried out along the direction vertical to the paper surface illustrated in figure 3.

And then, manufacturing a side wall which does not need to be roughened in the side wall of the photoresist mask shielding groove, and roughening the side wall close to the epitaxial layer and the side wall far away from the epitaxial layer in the groove in an etching mode to obtain a rough surface.

Wherein, the coarsening process may include: and coarsening the side wall of the groove by adopting argon gas, wherein the power is 300W, and then introducing oxygen gas and argon gas mixed gas to loosen the side wall of the groove. Wherein, the proportion of oxygen and argon gas mixture is 1:3, the power is 300W, and the time duration is 5min.

In other implementations, all the sidewalls of the groove may be directly roughened without providing a photoresist mask in the groove.

And finally, removing the mask structure, and plugging the plurality of grooves by adopting an adhesive layer to obtain a light shielding layer with a closed cavity.

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 (10)

1. A light emitting diode, comprising: the epitaxial layer (10), the passivation layer (20) and the light shielding layer (30), wherein the passivation layer (20) surrounds and covers the side wall of the epitaxial layer (10), and the light shielding layer (30) surrounds and covers the passivation layer (20);

the side wall of the epitaxial layer (10) is provided with a plurality of light guide parts (101), the light shielding layer (30) is internally provided with closed cavities (31) which are in one-to-one correspondence with the light guide parts (101), the closed cavities (31) are opposite to the corresponding light guide parts (101), and the inner wall of each closed cavity (31) far away from the epitaxial layer is used for reflecting light;

in the direction from one side of the light shielding layer (30) close to the epitaxial layer (10) to one side of the light shielding layer (30) far away from the epitaxial layer (10), the width of the closed cavity (31) is integral multiple of the wavelength of light emitted by the epitaxial layer (10).

2. The led of claim 1, wherein the light guide portion (101) is a protrusion having a triangular cross-sectional shape parallel to a top surface of the epitaxial layer (10).

3. The led of claim 1, wherein the light guide part (101) has a roughened area at an end close to the closed cavity (31).

4. The led of claim 1, wherein one end surface of the light guide part (101) is coplanar with the top surface of the epitaxial layer (10), and the other end surface of the light guide part (101) is coplanar with the bottom surface of the epitaxial layer (10).

5. The led of claim 1, wherein the plurality of light guide portions (101) are spaced apart along a circumference of the epitaxial layer (10).

6. The light-emitting diode according to claim 1, wherein regions of the two side surfaces of the light-shielding layer (30) opposite to the closed cavity (31) are roughened surfaces.

7. The led of claim 1, wherein the length of the closed cavity (31) is 3 μm to 7 μm, and the length direction of the closed cavity (31) is a direction perpendicular to the width direction of the closed cavity (31) in a plane parallel to the side of the epitaxial layer (10).

8. The light-emitting diode according to any one of claims 1 to 7, wherein the light-shielding layer (30) comprises a silica gel layer and an adhesive layer, carbon particles are embedded in the silica gel layer, a groove is formed on a side surface of the silica gel layer, and the adhesive layer is located on the side surface of the silica gel layer and covers the groove to form the closed cavity (31).

9. An led array, wherein the led array comprises a plurality of leds as claimed in any one of claims 1 to 8, and the plurality of led arrays are distributed.

10. A method for preparing a light emitting diode, the method comprising:

providing a substrate;

forming an epitaxial layer on the substrate, wherein the side wall of the epitaxial layer is provided with a plurality of light guide parts;

forming a passivation layer on the epitaxial layer, wherein the passivation layer surrounds and covers the side wall of the epitaxial layer;

the light guide layer is arranged on the passivation layer, the light shielding layer surrounds and covers the passivation layer, a closed cavity which corresponds to the light guide portion in a one-to-one mode is arranged in the light shielding layer, the closed cavity is opposite to the corresponding light guide portion, the inner wall, far away from the epitaxial layer, of the closed cavity is used for reflecting light, in the direction from one side, close to the epitaxial layer, of the light shielding layer to the side, far away from the epitaxial layer, of the light shielding layer, and the width of the closed cavity is an integral multiple of the wavelength of the light emitted by the epitaxial layer.

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