CN118352450A - Red light LED structure and preparation method thereof - Google Patents

Abstract

The application discloses a red light LED structure and a preparation method thereof, wherein the red light LED structure comprises: the epitaxial wafer comprises an n-conducting layer, an n-limiting layer, a multi-quantum well, a p-limiting layer, a current expansion layer and a p conducting layer which are stacked along the growth direction; an ODR structure and/or an antireflection film of the omnibearing reflecting mirror, wherein the ODR structure is arranged on the p conducting layer, the ODR structure sequentially comprises an Al ₂O₃ dielectric layer and a metal layer, the antireflection film is arranged on the side, away from the epitaxial growth direction, of the n-conducting layer, and the antireflection film is Al ₂O₃; the electrode, n-electrode is set up on n-conducting layer, p-electrode is set up on p-conducting layer. The red light LED structure and the preparation method thereof can effectively improve the light extraction efficiency of the light emitting diode and ensure the quality of devices.

Description

Red light LED structure and preparation method thereof

Technical Field

The application belongs to the technical field of semiconductor devices, and particularly relates to a red light LED structure and a preparation method thereof.

Background

Currently, high-brightness Light Emitting Diodes (LEDs) play an increasingly important role in various fields such as display systems, illumination systems, automobile tail lights, and the like. The red light emitting diode has relatively high internal quantum efficiency by taking AlGaInP material as an active region. However, many factors limit the external quantum efficiency, such as total internal reflection, blocking of emergent light by metal electrodes, and absorption of light by semiconductor materials such as GaAs, which affect the light extraction efficiency, making the external quantum efficiency low. In order to improve the light extraction efficiency of the light emitting diode, methods such as thickening a window layer, a reflecting structure, roughening a light emitting surface, roughening a side wall, a transparent substrate, an inverted pyramid structure, an antireflection film and the like are currently adopted.

In the above approach, the omni-directional mirror (omnidirectional reflector, ODR) structure, which is composed of a semiconductor, a low refractive index dielectric, and a metal having a low refractive index, attracts more attention due to its unique characteristics. Compared with a transparent substrate light-emitting diode (TRANSPARENT SUBSTRATE LED, TS-LED) which has the characteristics of complex manufacturing process, difficult mass production, high cost and the like, the ODR manufacturing process is relatively simple; in addition, for the distributed Bragg reflector (distributed Bragg reflector, DBR), the reflectivity of the DBR is influenced by the incidence angle of light, the ODR can efficiently reflect the incident light with full angle, the ODR has high reflectivity in the range of 0-85 degrees, and the ODR has relatively more types of optional dielectrics and metal layers and relatively lower cost.

In addition, the multilayer antireflection film can be deposited on the light emitting surface of the light emitting diode, the energy of reflected light is reduced, the energy of transmitted light is increased, and the light generated in the light emitting diode can furthest penetrate through the packaging material by designing the thickness and the refractive index of the multilayer antireflection film, so that the light extraction efficiency and the device performance of the light emitting diode are effectively improved.

Aiming at AlGaInP red light emitting diodes, the dielectric film materials required for preparing the ODR and the antireflection film at present are mainly deposited on an epitaxial material by PECVD (plasma enhanced chemical vapor deposition), and the manufacturing process is complex and has higher cost; in addition, as the epitaxial wafer is usually prepared in MOCVD (metal organic chemical vapor deposition) equipment, in the process of changing PECVD equipment, the transfer process of the epitaxial wafer cannot be ensured to be in an absolute clean environment, so that the surface of the epitaxial wafer is polluted, a defect center is formed, and the PECVD equipment is continuously used for growing a dielectric film, so that the defect is increased, larger particles are formed, the adhesive force between an epitaxial material and the dielectric film is influenced, and the dielectric film is easy to fall off; in addition, the epitaxial wafer is made of a semiconductor material, and the commonly adopted anti-reflection film or ODR low refractive index dielectric layer is made of an oxide material, the crystal structures of the anti-reflection film and the ODR low refractive index dielectric layer are not matched, and non-ideal crystal boundaries can be formed by direct deposition, so that the quality and the integrity of the dielectric film are affected.

Disclosure of Invention

The application aims to overcome at least one defect in the prior art, and provides a red light LED structure and a preparation method thereof so as to improve the light extraction efficiency of a light emitting diode.

The first aspect of the present application proposes a red LED structure.

In some embodiments, the red LED structure comprises:

The epitaxial wafer comprises an n-conducting layer, an n-limiting layer, a multiple quantum well layer, a p-limiting layer and a p-conducting layer which are stacked along the growth direction; and

The all-around reflector ODR structure is arranged on the p-conducting layer and sequentially comprises an Al ₂O₃ dielectric layer and a metal layer serving as a p electrode;

And the Al ₂O₃ dielectric layer is provided with a through hole, and the metal layer is electrically connected with the p-conducting layer through a part extending into the through hole.

According to some embodiments, the red LED structure further comprises: and a patterned n-electrode disposed on the n-conductive layer.

According to some embodiments, the red LED structure further comprises:

the Al ₂O₃ dielectric layer is arranged on the n-conducting layer and used as an antireflection film, wherein a patterned electrode channel is formed in the Al ₂O₃ dielectric layer, an n electrode is arranged in the patterned electrode channel, and the n electrode is electrically connected with the n-conducting layer.

In some embodiments, the red LED structure comprises:

The epitaxial wafer comprises an n-conducting layer, an n-limiting layer, a multiple quantum well layer, a p-limiting layer and a p-conducting layer which are stacked along the growth direction;

A metal layer as a p-electrode disposed on the p-conductive layer; and

The Al ₂O₃ dielectric layer is arranged on the n-conducting layer and used as an antireflection film, wherein a patterned electrode channel is formed in the Al ₂O₃ dielectric layer, an n electrode is arranged in the patterned electrode channel, and the n electrode is electrically connected with the n-conducting layer.

According to some embodiments, the Al ₂O₃ dielectric layer is obtained by in situ oxidation of an epitaxially grown AlAs layer on a p-or n-conducting layer.

According to some embodiments, the thicknesses of the Al ₂O₃ dielectric layers are each set to λ (2k+1)/4 n, where λ is the central emission wavelength of the LED; k is a natural number, and n is the refractive index of Al ₂O₃ at that wavelength.

According to some embodiments, λ=650 nm, n=1.7, k=0, and the thickness d=95.6 nm of the al ₂O₃ dielectric layer.

According to some embodiments, the p-conducting layer is an AlGaAs layer.

According to some embodiments, the n-conducting layer is a GaAs layer.

The second aspect of the application provides a method for manufacturing a red LED structure.

In some embodiments, the method for manufacturing the red LED structure includes:

Epitaxially growing an epitaxial wafer on a GaAs substrate, wherein the epitaxial wafer sequentially comprises a corrosion stop layer or a sacrificial layer, an n-conducting layer, an n-limiting layer, a multiple quantum well, a p-limiting layer, a p-conducting layer and a p-AlAs layer along the growth direction;

Oxidizing the p-AlAs layer into a p-Al ₂O₃ layer through in-situ oxidation;

Preparing a plurality of through holes on the p-Al ₂O₃ layer;

Depositing a metal layer on the p-Al ₂O₃ layer with the through hole as a p electrode, wherein the metal layer is electrically connected with the p-conductive layer through a part extending into the through hole, and the p-conductive layer, the p-Al ₂O₃ layer and the metal layer form an ODR structure;

Stripping the epitaxial wafer part of the corrosion-removing stop layer or the sacrificial layer from the GaAs substrate to expose the n-conducting layer;

A patterned n-electrode is prepared on the n-conductive layer.

In some embodiments, the method for manufacturing the red LED structure includes:

Epitaxially growing an epitaxial wafer on a GaAs substrate, wherein the epitaxial wafer sequentially comprises a corrosion stop layer or a sacrificial layer, an n-AlAs layer, an n-conducting layer, an n-limiting layer, a multiple quantum well layer, a p-limiting layer and a p-conducting layer along the growth direction;

Depositing a metal layer on the p-conductive layer to serve as a p electrode;

Stripping the epitaxial wafer part of the corrosion-removing stop layer or the sacrificial layer from the GaAs substrate to expose the n-AlAs layer;

Oxidizing the n-AlAs layer into an n-Al ₂O₃ layer by in-situ oxidation to serve as an antireflection film;

Preparing a patterned electrode channel on the n-Al ₂O₃ layer according to an n-electrode pattern;

And depositing metal in the patterned electrode channel on the n-Al ₂O₃ layer to form a patterned n-electrode, wherein the n-electrode is electrically connected with the n-conductive layer.

In some embodiments, the method for manufacturing the red LED structure includes:

Epitaxially growing an epitaxial wafer on a GaAs substrate, wherein the epitaxial wafer sequentially comprises a corrosion stop layer or a sacrificial layer, an n-AlAs layer, an n-conducting layer, an n-limiting layer, a multiple quantum well layer, a P-limiting layer, a P-conducting layer and a P-AlAs layer along the growth direction;

Oxidizing the p-AlAs layer into a p-Al ₂O₃ layer through in-situ oxidation;

Preparing a plurality of through holes on the p-Al ₂O₃ layer;

Depositing a metal layer on the p-Al ₂O₃ layer with the through hole as a p electrode, wherein the metal layer is electrically connected with the p-conductive layer through a part extending into the through hole, and the p-conductive layer, the p-Al ₂O₃ layer and the metal layer form an ODR structure;

Stripping the epitaxial wafer part of the corrosion-removing stop layer or the sacrificial layer from the GaAs substrate to expose the n-AlAs layer;

Oxidizing the n-AlAs layer into an n-Al ₂O₃ layer by in-situ oxidation to serve as an antireflection film;

Preparing a patterned electrode channel on the n-Al ₂O₃ layer according to an n-electrode pattern;

And depositing metal in the patterned electrode channel on the n-Al ₂O₃ layer to form a patterned n-electrode, wherein the n-electrode is electrically connected with the n-conductive layer.

According to the red light LED structure and the preparation method thereof, the AlGaInP red light LED with the ODR and/or antireflection film functions can be prepared without adopting PECVD equipment, so that the light extraction efficiency of the light-emitting diode can be effectively improved, the quality of a device is ensured, and the manufacturing cost is reduced; and the binding force between the Al ₂O₃ material and the semiconductor in the ODR and/or antireflection film structure is strong, so that the reliability of the LED is improved.

Drawings

Fig. 1 is a flowchart of a method of manufacturing a red LED structure according to one embodiment of the present application.

Fig. 2 is a flowchart of a method of fabricating a red LED structure according to another embodiment of the present application.

Fig. 3 is a flowchart of a method of fabricating a red LED structure according to another embodiment of the present application.

Fig. 4 is a schematic cross-sectional view of a process for fabricating a red LED structure according to one embodiment of the present application.

Fig. 5 is a schematic cross-sectional view of the red LED structure of fig. 4 after fabrication.

Fig. 6 is a schematic cross-sectional view of a process for fabricating a red LED structure according to another embodiment of the present application.

Fig. 7 is a schematic cross-sectional view of the red LED structure of fig. 6 after fabrication.

Fig. 8 is a schematic cross-sectional view of a process for fabricating a red LED structure according to another embodiment of the present application.

Fig. 9 is a schematic cross-sectional view of the red LED structure of fig. 8 after fabrication.

List of reference numerals

100GaAs substrate 201 etch stop layer or sacrificial layer 202n-AlAs layer

203 N-conductive layer 204 n-confinement layer 205 multiple quantum well layer

206 P-confinement and current spreading layer 207 p-conductive layer 208p-AlAs layer

308P-Al ₂O₃ layer 311 via 312 metal layer (P electrode)

402N-Al ₂O₃ layer 411 patterned electrode channel 412n electrode

Detailed Description

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the embodiments will be described and illustrated in detail below with reference to the accompanying drawings, and it is noted that the descriptions of the drawings and the specific embodiments are only for better understanding of the present application, and the present application is not limited to the described embodiments.

Technical or scientific terms used herein should be given the ordinary meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The use of the terms "comprising" or "includes" and the like in this specification is intended to be open-ended terms that do not exclude other elements, components, parts, or items than those explicitly listed. The terms "connected" or "connected," and the like, are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", etc. are used merely to indicate relative positional relationships, which may also be changed when the absolute position of the object to be described is changed. "first," "second," etc. are used for the purpose of distinguishing between different elements and not necessarily for a specific order.

The general conception of the invention is to provide a red light LED structure, wherein an in-situ growth mode is utilized to prepare an antireflection film and/or an ODR dielectric insulation layer, so that a novel red light LED structure is obtained, the light extraction efficiency of an LED is improved, and the problems that the antireflection film and/or the ODR dielectric insulation layer are easy to cause defects, easy to fall off, incomplete and the like when PECVD equipment is adopted to prepare the antireflection film and/or the ODR dielectric insulation layer are avoided.

In general, the red LED structure of the present invention includes an LED epitaxial wafer, an omnidirectional reflector ODR (omnidirectional reflector) structure fabricated on the p-side of the epitaxial wafer, and/or an anti-reflection film fabricated on the n-side of the epitaxial wafer. The epitaxial wafer comprises an n-conducting layer, an n-limiting layer, a multiple quantum well layer, a p-limiting layer, a current expansion layer and a p-conducting layer which are stacked along the growth direction; the ODR is arranged on the p-conducting layer and sequentially comprises an Al ₂O₃ dielectric layer and a metal layer; the anti-reflection film is arranged on one side of the n-conducting layer, which is away from the epitaxial growth direction, and the anti-reflection film is an Al ₂O₃ film layer. The metal layer of the ODR may serve as a p-electrode, with an n-electrode disposed over the n-conductive layer. The Al ₂O₃ dielectric layer of the ODR structure and the Al ₂O₃ film layer serving as the antireflection film are both obtained by adopting an AlAs layer in-situ oxidation growth mode. Specifically, before the n-conductive layer is epitaxially grown and/or after the p-conductive layer is epitaxially grown, the AlAs layer is completely oxidized into Al ₂O₃ through in-situ oxidation, so that an Al ₂O₃ dielectric layer of an ODR structure and/or an Al ₂O₃ film layer serving as an antireflection film are obtained.

Specifically, in some embodiments, the LED epitaxial wafer may be epitaxially grown on a GaAs substrate, the n-conductive layer may be a GaAs conductive layer, the n-confinement layer may be an AlInP confinement layer, a material of the multiple quantum well layer is AlGaInP/GaInP, alGaInP is a material of a barrier, and GaInP is a material of a well; the p-confinement layer may be an AlInP confinement layer, and the current spreading layer may be formed as one layer with the AlInP confinement layer, that is, the AlInP confinement layer simultaneously serves as the current spreading layer; or may be devoid of a current spreading layer; the p-conductive layer may be an AlGaAs conductive layer.

The red LED structure in some embodiments comprises: the epitaxial wafer comprises an n-conducting layer, an n-limiting layer, a multiple quantum well layer, a p-limiting layer, a current expansion layer and a p-conducting layer which are stacked along the growth direction; the ODR structure of the omnibearing reflecting mirror comprises an Al ₂O₃ dielectric layer and a metal layer, wherein the metal layer is used as a reflecting layer and a p electrode layer; the Al ₂O₃ dielectric layer is provided with a through hole, the metal layer is electrically connected with the P-conducting layer through a part extending into the through hole, and the metal filled through hole and the semiconductor layer form an ohmic contact structure so as to ensure the injection and conduction of current. Further, the red LED structure further comprises a patterned n electrode arranged on the n-conducting layer.

In the embodiment, by arranging the ODR structure on the p-conducting layer, the light incident at all angles can be reflected efficiently, and the light extraction efficiency and the device performance of the light emitting diode are improved effectively.

The red LED structure in other embodiments includes: the epitaxial wafer comprises an n-conducting layer, an n-limiting layer, a multiple quantum well layer, a p-limiting layer, a current expansion layer and a p-conducting layer which are stacked along the growth direction; a metal layer as a p-electrode disposed on the p-conductive layer; and an Al ₂O₃ dielectric layer which is arranged on the n-conducting layer and used as an antireflection film, wherein a patterned electrode channel is formed in the Al ₂O₃ dielectric layer, an n electrode is arranged in the patterned electrode channel, and the n electrode is electrically connected with the n-conducting layer.

In the above embodiment, by disposing the antireflection film on the n-conductive layer of the light emitting surface, the energy of the reflected light is reduced, the energy of the transmitted light is increased, and the light generated in the light emitting diode can be transmitted through the packaging material to the maximum extent, so that the light extraction efficiency and the device performance of the light emitting diode can be effectively improved.

The red LED structure in other embodiments includes: the epitaxial wafer comprises an n-conducting layer, an n-limiting layer, a multiple quantum well layer, a p-limiting layer, a current expansion layer and a p-conducting layer which are stacked along the growth direction; the all-around reflector ODR structure is arranged on the p-conducting layer and sequentially comprises an Al ₂O₃ dielectric layer and a metal layer serving as a p electrode; and the Al ₂O₃ dielectric layer is provided with a through hole, and the metal layer is electrically connected with the P-conductive layer through a part extending into the through hole. Further, the red LED structure further comprises an Al ₂O₃ dielectric layer which is arranged on the n-conducting layer and serves as an antireflection film, wherein a patterned electrode channel is formed in the Al ₂O₃ dielectric layer, an n electrode is arranged in the patterned electrode channel, and the n electrode is electrically connected with the n-conducting layer.

In the above embodiment, by disposing the ODR structure on the p-conductive layer and disposing the antireflection film on the n-conductive layer, the light extraction efficiency and the device performance of the light emitting diode can be more effectively improved by the superposition of the two.

In the above embodiment, for the ODR structure and the antireflection film, according to the bragg reflector principle, the thickness of the Al ₂O₃ dielectric layer may be set to λ (2k+1)/4 n, where λ is the central emission wavelength of the LED; k is a natural number, and n is the refractive index of Al ₂O₃ at that wavelength. Further, red light with wavelength λ=650 nm can be selected, refractive index n=1.7 of Al ₂O₃, k=0, and thickness of the required Al ₂O₃ can be calculated: d=95.6 nm. By adopting the parameters, the LED can be ensured to obtain the maximum light extraction efficiency.

The method of manufacturing the red LED structure of the present invention is described below.

Fig. 1 is a flowchart of a method of manufacturing a red LED structure according to one embodiment of the present application. Referring to fig. 1, the method for manufacturing the red LED structure of this embodiment includes the following steps:

S11: epitaxial wafers were grown epitaxially on GaAs substrates. Specifically, MOCVD equipment can be adopted to sequentially epitaxially grow a corrosion stop layer or sacrificial layer, an n-conducting layer, an n-limiting layer, a multiple quantum well, a p-limiting layer, a current expansion layer, a p-conducting layer and a p-AlAs layer on a GaAs substrate;

S12: the p-AlAs layer is oxidized to a p-Al ₂O₃ layer by in situ oxidation. Specifically, the epitaxial wafer manufactured in the step S11 may be put into a wet oxygen furnace, oxidized by the wet oxygen furnace (put into an environment of oxygen and water vapor), and then the AlAs layer is completely oxidized into Al ₂O₃, which is used as a low refractive index dielectric material in an ODR structure;

S13: a plurality of vias are fabricated on the p-Al ₂O₃ layer. Specifically, a plurality of through holes can be prepared on the p-Al ₂O₃ layer by adopting photoetching and corrosion processes and used as conductive holes;

S14: a metal layer is deposited on the p-Al ₂O₃ layer formed with the via hole as a p-electrode. Specifically, a metal layer with high reflectivity such as Au, ag and the like can be deposited on the p-Al ₂O₃ layer through a magnetron sputtering process and the like; wherein, except depositing on the surface of p-Al ₂O₃ layer, a part of metal material fills the through hole in p-Al ₂O₃ layer and forms p-type ohmic contact with p-conductive layer; the metal layer at the non-conductive hole, the p-Al ₂O₃ layer and the p-conductive layer formed by the semiconductor material form an ODR structure, so that the light-emitting efficiency of the LED is improved;

S15: the epitaxial wafer portion of the etch stop layer or sacrificial layer is stripped from the GaAs substrate exposing the n-conductive layer. Specifically, a mixed solution of hydrogen peroxide and ammonia water can be adopted to finish removing the GaAs substrate, and then hydrochloric acid solution is used to corrode the stop layer to finish stripping the epitaxial layer from the substrate; or if a sacrificial layer is used, the epitaxial wafer is peeled from the GaAs substrate by selectively etching the sacrificial layer with a solution that etches the sacrificial layer.

S16: a patterned n-electrode is prepared on the n-conductive layer. Specifically, an electrode pattern can be obtained on the n-conductive layer through a photolithography process, a metal layer is sputtered while the photoresist is maintained, and then the photoresist is removed to obtain a patterned n-electrode, and the n-electrode is in metal-semiconductor contact with the n-conductive layer made of a semiconductor material.

According to the red light LED structure obtained by the method, the ODR structure can be arranged on the p-conducting layer, so that the full-angle incident light can be efficiently reflected, and the light extraction efficiency and the device performance of the light emitting diode are effectively improved.

Fig. 2 is a flowchart of a method of fabricating a red LED structure according to another embodiment of the present application. Referring to fig. 2, the method for manufacturing the red LED structure of this embodiment includes the following steps:

S21: epitaxial wafers were grown epitaxially on GaAs substrates. Specifically, MOCVD equipment can be adopted to sequentially epitaxially grow a corrosion stop layer or sacrificial layer, an n-AlAs layer, an n-conducting layer, an n-limiting layer, a multiple quantum well layer, a p-limiting layer, a current expansion layer and a p-conducting layer on a GaAs substrate;

S22: depositing a metal layer on the p-conductive layer to serve as a p electrode; specifically, a whole metal layer with high reflectivity can be sputtered on the p-conductive layer to serve as a p electrode and also serve as a reflecting layer;

s23: stripping the epitaxial wafer part of the corrosion-removing stop layer or the sacrificial layer from the GaAs substrate to expose the n-AlAs layer; specifically, a mixed solution of hydrogen peroxide and ammonia water can be adopted to finish removing the GaAs substrate, and then hydrochloric acid solution is used to corrode the stop layer to finish stripping the epitaxial layer from the substrate; or if a sacrificial layer is used, the epitaxial wafer is peeled from the GaAs substrate by selectively etching the sacrificial layer with a solution that etches the sacrificial layer.

S24: oxidizing the n-AlAs layer into an n-Al ₂O₃ layer by in-situ oxidation to serve as an antireflection film. Specifically, the epitaxial wafer manufactured in the step S23 can be placed into a wet oxygen furnace, and after the oxidation treatment of the wet oxygen furnace, the n-AlAs layer is completely oxidized into Al ₂O₃ to be used as an antireflection film;

S25: patterned electrode channels were fabricated on the n-Al ₂O₃ layer in accordance with the n-electrode pattern. Specifically, a patterning electrode channel can be prepared on the n-Al ₂O₃ layer by photolithography and etching processes;

S26: and depositing metal in the patterned electrode channel on the n-Al ₂O₃ layer to form a patterned n-electrode, and enabling the n-electrode to form metal-semiconductor contact with the n-conductive layer made of semiconductor material so as to be electrically connected with the n-conductive layer.

According to the red light LED structure obtained by the method, the antireflection film can be arranged on the n-conducting layer of the light emitting surface, and the light extraction efficiency and the device performance of the light emitting diode can be effectively improved.

Fig. 3 is a flowchart of a method of fabricating a red LED structure according to another embodiment of the present application. Referring to fig. 3, the method for preparing the red LED structure includes the following steps:

s31: epitaxial wafers were grown epitaxially on GaAs substrates. Specifically, MOCVD equipment can be adopted to sequentially epitaxially grow a corrosion stop layer or sacrificial layer, an n-AlAs layer, an n-conducting layer, an n-limiting layer, a multiple quantum well layer, a p-limiting layer, a current expansion layer, a p-conducting layer and a p-AlAs layer on a GaAs substrate;

S32: the p-AlAs layer is oxidized to a p-Al ₂O₃ layer by in situ oxidation. Specifically, the epitaxial wafer manufactured in the step S1 may be put into a wet oxygen furnace, oxidized by the wet oxygen furnace (put into an environment of oxygen and water vapor), and then the p-AlAs layer is completely oxidized into p-Al ₂O₃, which is used as a low refractive index dielectric material in the ODR structure;

S33: a plurality of vias are fabricated on the p-Al ₂O₃ layer. Specifically, a plurality of through holes can be prepared on the p-Al ₂O₃ layer by adopting photoetching and corrosion processes and used as conductive holes;

s34: a metal layer is deposited on the p-Al ₂O₃ layer formed with the via hole as a p-electrode. Specifically, a metal layer with high reflectivity such as Au, ag and the like can be deposited on the p-Al ₂O₃ layer through a magnetron sputtering process and the like; wherein, except depositing on the surface of p-Al ₂O₃ layer, a part of metal material fills the through hole in p-Al ₂O₃ layer and forms p-type ohmic contact with p-conductive layer; the metal layer at the non-conductive hole, the p-Al ₂O₃ layer and the p-conductive layer formed by the semiconductor material form an ODR structure, so that the light-emitting efficiency of the LED is improved;

S35: and stripping the epitaxial wafer part of the corrosion-removing stop layer or the sacrificial layer from the GaAs substrate to expose the n-AlAs layer. Specifically, a mixed solution of hydrogen peroxide and ammonia water can be adopted to finish removing the GaAs substrate, and then hydrochloric acid solution is used to corrode the stop layer to finish stripping the epitaxial layer from the substrate; or if a sacrificial layer is used, the epitaxial wafer is peeled from the GaAs substrate by selectively etching the sacrificial layer with a solution that etches the sacrificial layer.

S36: oxidizing the n-AlAs layer into an n-Al ₂O₃ layer by in-situ oxidation to serve as an antireflection film. Specifically, the epitaxial wafer manufactured in the step S35 can be placed into a wet oxygen furnace, and after the oxidation treatment of the wet oxygen furnace, the n-AlAs layer is completely oxidized into Al ₂O₃ to be used as an antireflection film;

S37: patterned electrode channels were fabricated on the n-Al ₂O₃ layer in accordance with the n-electrode pattern. Specifically, a patterning electrode channel can be prepared on the n-Al ₂O₃ layer by photolithography and etching processes;

S38: and depositing metal in the patterned electrode channel on the n-Al ₂O₃ layer to form a patterned n-electrode, and enabling the n-electrode to form metal-semiconductor contact with the n-conductive layer made of semiconductor material so as to be electrically connected with the n-conductive layer.

According to the red light LED structure obtained by the method, the ODR structure can be arranged on the p-conducting layer, and meanwhile, the anti-reflection film is arranged on the n-conducting layer, so that the light extraction efficiency and the device performance of the light emitting diode can be improved more effectively.

In the method for manufacturing the red LED of the above embodiment, for the ODR and the antireflection film, the thickness of Al ₂O₃ is set to λ (2k+1)/4 n according to the bragg mirror principle, where λ is the central emission wavelength of the LED; n is the refractive index of Al ₂O₃ at this wavelength, and k is a natural number.

Further, λ=650 nm, n=1.7, k=0 can be taken, so the thickness of the required Al ₂O₃ can be calculated: d=95.6 nm.

Compared with the traditional method, the preparation method of the red LED of the invention prepares the dielectric layer and/or the anti-reflection film of the ODR by an in-situ oxidation method, and Al ₂O₃ can be deposited on the surface of the epitaxial wafer without PECVD equipment, thereby simplifying the preparation process and reducing the cost. Meanwhile, as the AlAs is grown in an epitaxial growth mode, the growth quality of the AlAs is good, and then the AlAs is converted into Al ₂O₃ in situ, so that the problem of poor bonding force between Al ₂O₃ and an epitaxial wafer can be avoided, and the reliability of the LED is improved.

The technical scheme of the invention is further described in detail through specific embodiments with reference to the accompanying drawings.

Example 1:

the embodiment can be applied to a flip LED structure, al ₂O₃ is used as a low refractive index material of ODR, and the implementation process is as follows:

First, as shown in fig. 4, a flip-chip AlGaInP red LED epitaxial wafer is grown on GaAs substrate 100 using a MOVCD apparatus, and the epitaxial wafer growth materials are, in order, gaInP corrosion barrier layer 201, gaAs conductive layer 203, alInP n-plane confinement layer 204, MQW (multiple quantum well) active light-emitting layer 205, alInP p-plane confinement and current spreading layer 206, alGaAs conductive layer 207, and AlAs layer 208 (95.6 nm).

Next, as shown in fig. 5, after the grown epitaxial wafer is oxidized by a wet oxygen furnace (placed in an environment of oxygen and water vapor), the AlAs layer 208 is completely oxidized into an Al ₂O₃ layer 308, which is used as a low refractive index dielectric material in the ODR structure.

Oxidation reaction equation:

4AlAs+O₂＝2Al₂O₃+4As

2As+3H₂O＝H₃AsO₃+H₃AsO₄

the reaction product was removed by washing.

Then, a plurality of through holes 311 (6-8 μm diameter, 20-30 μm interval) are etched in the Al ₂O₃ layer 308 by photolithography as conductive holes, then a 3-4 μm Au metal layer 312 is evaporated, and part of the metal Au fills the through holes, wherein the metal Au forms p-type ohmic contact with the semiconductor (AlGaAs layer 207) at the conductive holes, and the Au metal layer 312 forms ODR with the Al ₂O₃ layer 308 and the semiconductor (AlGaAs layer 207) at the non-conductive holes, and then annealing is performed.

Then, the GaAs substrate 100 is removed by using a mixed solution of hydrogen peroxide and ammonia water, and then the GaInP barrier layer 201 is etched by hydrochloric acid, thereby peeling the epitaxial wafer from the substrate 100.

Finally, electrode patterns are obtained on the surface of the n-GaAs conductive layer 203 through photoetching, an Au metal layer with the thickness of 3-4 mu m is sputtered, photoresist is removed, and an n-surface patterned electrode 412 is obtained and is in metal-semiconductor contact with the n-GaAs conductive layer 203.

Example 2:

the embodiment can be applied to a flip LED structure, al ₂O₃ is used as an antireflection film, an ODR structure is not provided, and the specific implementation process is as follows:

As shown in fig. 6, a flip-chip AlGaInP red LED epitaxial wafer is grown on a GaAs substrate 100 using a MOVCD apparatus, and the epitaxial wafer growth materials are, in order, a GaInP corrosion barrier layer 201, an n-plane AlAs layer 202 (95.6 nm), a GaAs conductive layer 203, an AlInP n-plane confinement layer 204, an MQW active light-emitting layer 205, an AlInP p-plane confinement layer 206, and an AlGaAs conductive layer 207.

Then, the grown epitaxial wafer is subjected to removal of the GaAs substrate 100 by using a mixed solution of hydrogen peroxide and ammonia water, and then the GaInP barrier layer 201 is etched by hydrochloric acid, thereby completing the peeling of the epitaxial wafer from the substrate 100.

As shown in fig. 7, after the peeled epitaxial wafer is oxidized by a wet oxygen furnace (placed in an environment of oxygen and water vapor), the n-side AlAs layer 202 is completely oxidized into an n-Al ₂O₃ layer 402 as an antireflection film;

then, an Au metal layer 312 of 3-4 μm is sputtered on the p-side AlGaAs conductive layer 207 to form a metal-semiconductor contact.

Then, in the n-side Al ₂O₃ layer 402, a patterned electrode channel 411 is formed by photolithography and etching; then, 3-4 μm Au is sputtered, the photoresist is removed, a patterned n-electrode 412 is formed, and the patterned n-electrode 412 forms a gold semiconductor contact with the semiconductor (GaAs conductive layer 203).

Example 3:

The embodiment can be applied to a flip LED structure, al ₂O₃ is used as a low refractive index dielectric material and an antireflection film of an ODR, and the specific implementation process is as follows:

First, as shown in fig. 8, a flip-chip AlGaInP red LED epitaxial wafer is grown on GaAs substrate 100 using a MOVCD apparatus, and the epitaxial wafer growth materials are, in order, gaInP corrosion barrier layer 201, n-side AlAs layer 202 (95.6 nm), gaAs conductive layer 203, alInP n-side confinement layer 204, MQW active light-emitting layer 205, alInP p-side confinement and current spreading layer 206, alGaAs conductive layer 207, and p-side AlAs layer 208 (95.6 nm).

As shown in fig. 9, after the grown epitaxial wafer is oxidized by a wet oxygen furnace (placed in an environment of oxygen and water vapor), the p-surface AlAs layer 208 is completely oxidized into an Al ₂O₃ layer 308, which is used as a low refractive index material in the ODR structure;

Then, in the p-plane Al ₂O₃ layer 308, through holes 311 (6-8 μm diameter, 20-30 μm interval) are etched by photolithography, photoresist is remained, after sputtering 30-50nm Au/Zn/Au, photoresist is removed, and then 800-850nm Au is sputtered. The Au/Zn/Au is to form p-type ohmic contact with the semiconductor at the conductive hole, and the Au metal layer 312 at the non-conductive hole forms ODR with the Al ₂O₃ layer and the semiconductor (AlGaAs layer 207) and then is annealed.

Then, the GaAs substrate 100 is removed by using a mixed solution of hydrogen peroxide and ammonia water, and then the GaInP barrier layer 201 is etched by hydrochloric acid, thereby peeling the epitaxial wafer from the substrate 100.

The peeled epitaxial wafer is oxidized again by a wet oxygen furnace (placed in an environment of oxygen and water vapor), and then the n-side AlAs layer 202 is completely oxidized into an Al ₂O₃ layer 402 as an antireflection film.

Then, in the n-side Al ₂O₃ layer 402, a patterned electrode channel 411 is formed by photolithography and etching; subsequently, 3-4 μm Au is sputtered, the photoresist is removed, and a patterned n-electrode 412 is formed, forming a gold semiconductor contact with the semiconductor (GaAs conductive layer 203).

The red light LED structure and the preparation method thereof in each embodiment of the application have the following technical effects or advantages:

1. And growing an AlAs layer on the p-face and/or n-face conducting layer of the flip AlGaInP red LED structure, and oxidizing the AlAs layer into an Al ₂O₃ layer to prepare an Au/Al ₂O₃ ODR and/or Al ₂O₃ antireflection film, so that the light emitting rate of the LED is improved.

2. Al ₂O₃ medium layer is prepared by oxidizing epitaxially grown AlAs into Al ₂O₃, and an Al ₂O₃ layer can be deposited on the surface of an epitaxial wafer without PECVD or other evaporation equipment, so that the process for preparing the ODR and the anti-reflection film is simplified, and the cost is reduced.

Lattice constant of AlAs is close to that of GaAs, gaAs isAlAs is of AlxGa (1-x) As can grow lattice matched AlAs materials with better crystallization quality and stronger interface bonding force on GaAs or AlGaAs according to different components of Al, so that after the AlxGa (1-x) As is oxidized into Al ₂O₃, the bonding force between GaAs/AlGaAs and Al ₂O₃ is superior to the bonding force of directly evaporating Al ₂O₃, the problem of poor bonding between Al ₂O₃ and a semiconductor is solved, and the reliability of the LED is improved.

The foregoing embodiments are merely illustrative of the principles and configurations of the present application, and are not intended to be limiting, it will be appreciated by those skilled in the art that any changes and modifications may be made without departing from the general inventive concept. The protection scope of the present application should be defined as the scope of the claims of the present application.

Claims (12)

1. A red LED structure comprising:

The epitaxial wafer comprises an n-conducting layer, an n-limiting layer, a multiple quantum well layer, a p-limiting layer and a p-conducting layer which are stacked along the growth direction; and

The all-around reflector ODR structure is arranged on the p-conducting layer and sequentially comprises an Al ₂O₃ dielectric layer and a metal layer serving as a p electrode;

And the Al ₂O₃ dielectric layer is provided with a through hole, and the metal layer is electrically connected with the p-conducting layer through a part extending into the through hole.

2. The red LED structure of claim 1, further comprising:

And a patterned n-electrode disposed on the n-conductive layer.

3. The red LED structure of claim 1, further comprising:

the Al ₂O₃ dielectric layer is arranged on the n-conducting layer and used as an antireflection film, wherein a patterned electrode channel is formed in the Al ₂O₃ dielectric layer, an n electrode is arranged in the patterned electrode channel, and the n electrode is electrically connected with the n-conducting layer.

4. A red LED structure comprising:

The epitaxial wafer comprises an n-conducting layer, an n-limiting layer, a multiple quantum well layer, a p-limiting layer and a p-conducting layer which are stacked along the growth direction;

A metal layer as a p-electrode disposed on the p-conductive layer; and

The Al ₂O₃ dielectric layer is arranged on the n-conducting layer and used as an antireflection film, wherein a patterned electrode channel is formed in the Al ₂O₃ dielectric layer, an n electrode is arranged in the patterned electrode channel, and the n electrode is electrically connected with the n-conducting layer.

5. The red LED structure of any one of claims 1-4, wherein the Al ₂O₃ dielectric layer is obtained after in situ oxidation of an epitaxially grown AlAs layer on a p-or n-conducting layer.

6. The red LED structure of any one of claims 1-4, wherein the thickness of the Al ₂O₃ dielectric layers are each set to λ (2k+1)/4 n, where λ is the central emission wavelength of the LED; k is a natural number, and n is the refractive index of Al ₂O₃ at that wavelength.

7. The red LED structure of claim 6, wherein λ=650 nm, n=1.7, k=0, and the thickness d=95.6 nm of the al ₂O₃ dielectric layer.

8. The red LED structure of claim 1 wherein the p-conductive layer is an AlGaAs layer.

9. The red LED structure of claim 1 wherein the n-conductive layer is a GaAs layer.

10. A preparation method of a red light LED structure comprises the following steps:

Epitaxially growing an epitaxial wafer on a GaAs substrate, wherein the epitaxial wafer sequentially comprises a corrosion stop layer or a sacrificial layer, an n-conducting layer, an n-limiting layer, a multiple quantum well, a p-limiting layer, a p-conducting layer and a p-AlAs layer along the growth direction;

Oxidizing the p-AlAs layer into a p-Al ₂O₃ layer through in-situ oxidation;

Preparing a plurality of through holes on the p-Al ₂O₃ layer;

Depositing a metal layer on the P-Al ₂O₃ layer with the through hole as a P electrode, wherein the metal layer is electrically connected with the P-conductive layer through a part extending into the through hole, and the P-conductive layer, the P-Al ₂O₃ layer and the metal layer form an ODR structure;

Stripping the epitaxial wafer part of the corrosion-removing stop layer or the sacrificial layer from the GaAs substrate to expose the n-conducting layer;

A patterned n-electrode is prepared on the n-conductive layer.

11. A preparation method of a red light LED structure comprises the following steps:

Epitaxially growing an epitaxial wafer on a GaAs substrate, wherein the epitaxial wafer sequentially comprises a corrosion stop layer or a sacrificial layer, an n-AlAs layer, an n-conducting layer, an n-limiting layer, a multiple quantum well layer, a p-limiting layer and a p-conducting layer along the growth direction;

Depositing a metal layer on the p-conductive layer to serve as a p electrode;

Stripping the epitaxial wafer part of the corrosion-removing stop layer or the sacrificial layer from the GaAs substrate to expose the n-AlAs layer;

Oxidizing the n-AlAs layer into an n-Al ₂O₃ layer by in-situ oxidation to serve as an antireflection film;

Preparing a patterned electrode channel on the n-Al ₂O₃ layer according to an n-electrode pattern;

And depositing metal in the patterned electrode channel on the n-Al ₂O₃ layer to form a patterned n-electrode, wherein the n-electrode is electrically connected with the n-conductive layer.

12. A preparation method of a red light LED structure comprises the following steps:

epitaxially growing an epitaxial wafer on a GaAs substrate, wherein the epitaxial wafer sequentially comprises a corrosion stop layer or a sacrificial layer, an n-AlAs layer, an n-conducting layer, an n-limiting layer, a multiple quantum well layer, a p-limiting layer, a p-conducting layer and a p-AlAs layer along the growth direction;

Oxidizing the P-AlAs layer into a P-Al ₂O₃ layer through in-situ oxidation;

Preparing a plurality of through holes on the p-Al ₂O₃ layer;

Depositing a metal layer on the p-Al ₂O₃ layer with the through hole as a p electrode, wherein the metal layer is electrically connected with the p-conductive layer through a part extending into the through hole, and the p-conductive layer, the p-Al ₂O₃ layer and the metal layer form an ODR structure;

Stripping the epitaxial wafer part of the corrosion-removing stop layer or the sacrificial layer from the GaAs substrate to expose the n-AlAs layer;

Oxidizing the n-AlAs layer into an n-Al ₂O₃ layer by in-situ oxidation to serve as an antireflection film;

Preparing a patterned electrode channel on the n-Al ₂O₃ layer according to an n-electrode pattern;

And depositing metal in the patterned electrode channel on the n-Al ₂O₃ layer to form a patterned n-electrode, wherein the n-electrode is electrically connected with the n-conductive layer.