CN112054097A - Purple light LED epitaxial structure and manufacturing method - Google Patents

Abstract

An epitaxial structure of a purple light LED and a manufacturing method thereof are provided, wherein the method comprises the following steps of S100, sputtering an ALN film on a substrate; s102, growing an AlGaN buffer layer on the ALN film; s103, growing a non-doped aluminum gallium nitrogen layer on the aluminum gallium nitrogen buffer layer; s104, growing a layer of N-type AlGaN on the undoped AlGaN; the invention reduces the defect caused by larger mismatch between the substrate and the ALGaN material by sputtering the ALN buffer layer on the substrate, thereby improving the crystal of the whole epitaxial layerThe mass reduces dislocation and defect in the quantum well structure, reduces non-radiative recombination generated by the defect, improves internal quantum effect, and effectively limits the Stark effect QCS in the quantum well structure through the aluminum gallium nitrogen barrier layer, and simultaneously Mg in the circulating structure is doped with AL_xGa_(1‑x)N increases the two-dimensional electron gas of the material interface, thereby improving the capability of injecting holes into the luminous zone and improving the recombination efficiency of electrons and holes in the luminous zone.

Description

A kind of violet LED epitaxial structure and manufacturing method

technical field

The invention relates to a structure design and a manufacturing method in the manufacture of a light-emitting diode.

Background technique

A few days ago, the sterilization function of daily household products has gradually attracted the attention of consumers. Compared with traditional ultraviolet mercury lamps, ALGaN-based UVC-LEDs do not use mercury and do not require preheating. Therefore, they have the advantages of environmental protection and energy saving. A particularly great advantage. In the future, UVC-LEDs will enter a large number of commercial air-conditioning, surface sterilization and water purification applications, which will bring new increased demand for UVC-LEDs. However, the structure of UVC-LEDs requires aluminum gallium nitride with high AL composition. ALGaN materials, the current growth technology cannot obtain ALGaN materials with low defect density, and the ALGaN quantum well structure has large spontaneous polarization and piezoelectric polarization, resulting in energy band bending and the formation of Stark effect QCSE, which is affected by it. , the radiative recombination efficiency in the quantum well is very low, so by reducing the Stark effect QCSE in the ALGaN quantum well structure, increasing the radiative recombination efficiency, thereby improving the luminous efficiency has become a key technical issue.

The existing technology has the following problems: At present, the main method for reducing the QCSE of the Stark effect in ALGaN-based UVC-LEDs is to linearly optimize the ALGaN quantum barrier and the AL composition in the ALGaN barrier layer, thereby reducing the energy band bending of the quantum well, The purpose of limiting the Stark effect QCSE is achieved, thereby enhancing the recombination of electrons and holes and improving the recombination efficiency, but this method will reduce the injection efficiency of holes at the same time, so the improvement effect is limited. The prior art solution application number 201510300906 has proposed technical solutions for ALGaN and ALInGaN, and 201811468293 also has technical solutions for ALN and ALGaN. In view of the above situation, we want to design a deep ultraviolet epitaxial wafer preparation method including a novel barrier layer (N cycle structure: aluminum nitride/ALxGa(1-x)N/ALaInbGa(1-a-b)N), which can Effectively limit the Stark effect QCSE, and at the same time improve the hole injection effect.

SUMMARY OF THE INVENTION

Therefore, it is necessary to provide an epitaxial wafer that can improve the luminous efficiency of a violet LED, and solve the problem of insufficient electron migration in the prior art.

A method for fabricating an epitaxial structure of a violet LED, comprising the following steps:

S100, sputtering an ALN film on the substrate;

S102, growing an aluminum gallium nitride buffer layer on the ALN film;

S103 , growing an undoped aluminum gallium nitride layer on the aluminum gallium nitride buffer layer;

S104, growing a layer of N-type AlGaN on the undoped AlGaN;

S105, growing a stress release layer on the N-type AlGaN;

S106, growing a high temperature quantum well structure on the stress release layer;

S107, growing a light-emitting quantum well structure on the high temperature quantum well structure;

S108, growing a barrier layer on the light-emitting quantum well structure, where the barrier layer is an aluminum gallium nitride barrier layer, including multiple cycles of (AlN/AL _x Ga _(1-x) N/AL _a In _b Ga _(1-ab) N);

S109, growing a P-type AlGaN structure on the barrier layer structure;

S110 , growing heavily doped P-type ALGaN on the P-type AlGaN.

Further, after step S100, a further step is performed, using MOCVD to perform high temperature treatment on the ALN thin film buffer layer, the temperature is 1200-1300°C, the rotational speed is 1000-1200RPM, and the pressure is 200-750Torr;

Specifically, step S100 is specifically, using PECVD equipment to sputter an ALN film with a thickness of 10-25 nm on the sapphire substrate.

Specifically, the AlGaN barrier layer includes multiple cycles of (AlN/Mg-doped ALxGa(1- _{x )} N/ _ALaInbGa (1- _{ab )} N).

Further, the thickness of the heavily doped P-type ALGaN layer described in step S110 is 5-10 nm, the Mg doping concentration is 4E21, and the pressure is 400-800 Torr.

An epitaxial structure of a violet LED, comprising the following parts sequentially grown on a substrate 1:

ALN film 2;

AlGaN buffer layer 3;

undoped aluminum gallium nitride layer 4;

N-type aluminum gallium nitride layer 5;

stress release layer 6;

High temperature quantum well structure 7;

Light-emitting quantum well structure 8;

A barrier layer 9, the barrier layer is an AlGaN barrier layer, including a plurality of cycles (Aluminum Nitride/AL _x Ga _(1-x) N/AL _a In _b Ga _(1-ab) N);

P-type AlGaN structure 10;

Heavily doped P-type ALGaN 11.

Further, the substrate is a sapphire substrate.

Specifically, the AlGaN barrier layer includes multiple cycles of (AlN/Mg-doped ALxGa(1- _{x )} N/ _ALaInbGa (1- _{ab )} N).

Specifically, the thickness of the heavily doped P-type ALGaN layer is 5-10 nm, and the doping type is Mg doping.

By sputtering the ALN buffer layer on the sapphire, the invention reduces the defects caused by the large mismatch between the sapphire and the ALGaN material, thereby improving the crystal quality of the entire epitaxial layer, reducing dislocations and defects in the quantum well structure, and reducing defects caused by The resulting non-radiative recombination improves the internal quantum effect, and on the other hand also passes through the AlGaN barrier layer (containing AlN/Mg doped AL _x Ga(1-x)N/AL _a In _b Ga(1-ab) The N) structure can effectively confine the Stark effect QCS in the quantum well structure, while the Mg-doped AL _x Ga _(1-x) N in the cyclic structure increases the two-dimensional electron gas at the material interface, thereby enhancing hole injection into the light-emitting region The ability to improve the recombination efficiency of electrons and holes in the light-emitting region. Thereby, a high-quality ALGaN-based violet LED epitaxial wafer is obtained, which improves the violet LED epitaxial wafer by about 5-35%.

Description of drawings

1 is a schematic flowchart of a method for fabricating a UV epitaxial wafer according to the specific embodiment;

FIG. 2 is a schematic diagram of the structure of the ultraviolet epitaxial wafer according to the specific embodiment.

Description of reference numerals

1. Substrate:

2. ALN film;

3. AlGaN buffer layer;

4. Undoped AlGaN layer;

5. N-type aluminum gallium nitride layer;

6. Stress release layer;

7. High temperature quantum well structure;

8. Light-emitting quantum well structure;

9. Barrier layer;

10. P-type AlGaN structure;

11. Heavy doped P-type ALGaN.

Detailed ways

In order to describe in detail the technical content, structural features, achieved objects and effects of the technical solutions, the following detailed descriptions are given in conjunction with specific embodiments and in conjunction with the accompanying drawings.

Please refer to FIG. 1 , which is a method for fabricating an epitaxial structure of a violet LED, including the following steps:

A method for fabricating an epitaxial structure of a violet LED, comprising the following steps:

S100, sputtering an ALN film on the substrate;

S102, growing an aluminum gallium nitride buffer layer on the ALN film;

S103 , growing an undoped aluminum gallium nitride layer on the aluminum gallium nitride buffer layer;

S104, growing a layer of N-type AlGaN on the undoped AlGaN;

S105, growing a stress release layer on the N-type AlGaN;

S106, growing a high temperature quantum well structure on the stress release layer;

S107, growing a light-emitting quantum well structure on the high temperature quantum well structure;

S108, growing a barrier layer on the light-emitting quantum well structure, where the barrier layer is an aluminum gallium nitride barrier layer, including multiple cycles of (AlN/AL _x Ga _(1-x) N/AL _a In _b Ga _(1-ab) N);

S109, growing a P-type AlGaN structure on the barrier layer structure;

S110 , growing heavily doped P-type ALGaN on the growing P-type AlGaN.

The specific steps are described below through specific embodiments.

S100, using PECVD equipment to sputter a certain thickness of ALN film on the sapphire substrate, the specific thickness can be set between 10-25nm, the purpose is to reduce the stress and defects caused by lattice mismatch between the sapphire and ALGaN materials , thereby improving the crystal quality of the subsequently grown ALGaN material. In the above steps, the sputtering uses high-purity AL target material and plasma gas such as argon, oxygen, etc. as the reaction source, and performs magnetron sputtering. -22nm, preferably the thickness is 16nm, the oxygen flow rate is 0.5-3 sccm, preferably 3 sccm, the nitrogen dosage is 80-300 sccm, and the preferred dosage is 100 sccm.

S101. MOCVD can also be used to perform high temperature treatment on the grown ALN thin film buffer layer at a temperature of 1200-1300° C., a rotation speed of 1000-1200 RPM, a pressure of 200-750 Torr, and a H2 consumption of 120-400 slm. The temperature, rotation speed and pressure not mentioned in particular are the environment setting parameters of MOVCD, the same below. By sputtering the ALN thin film buffer layer in two stages and performing high-temperature treatment through the above steps, the defects caused by the large mismatch between the sapphire and ALGaN materials can be reduced, thereby improving the crystal quality of the entire epitaxial layer and reducing the number of defects in the quantum well structure. dislocations and defects, reduce the non-radiative recombination caused by defects, and improve the internal quantum effect.

S102. Using MOCVD, grow an AlGaN buffer layer on the ALN film, with a thickness of 10-15nm, a temperature of 550-850°C, a rotational speed of 500-600RPM, a pressure of 200-750Torr, the amount of H2 150-400slm, and the amount of N2 50 -150slm, ammonia consumption 50-200slm.

S103 , growing an undoped AlGaN layer on the AlGaN buffer layer with a thickness of 1.5-1.8um, a temperature of 1100-1150° C., a rotational speed of 800-1200 RPM, and a pressure of 50-750 Torr.

In a specific design example, the undoped ALGaN layer in step S103 is divided into a four-layer structure, the temperature of the first layer is 900-1050° C., the amount of TMGa (trimethyl gallium) is 800 sccm, and the amount of TMAL (trimethyl gallium) is 800 sccm. The temperature of the second layer is 1050-1100, the amount of TMGa is 1400sccm, and the amount of TMAL is 200sccm; the temperature of the third layer is 900-1050℃, the amount of TMGa is 800sccm, the amount of TMAL is 120sccm, and the temperature of the fourth layer is 1100-1150℃ , the amount of TMGa is 1800sccm, and the amount of TMAL is 300sccm.

S104, grow another layer of N-type AlGaN on the undoped AlGaN; the growth thickness is 1.5-2um, the temperature is 1000-1200°C, the rotation speed is 800-1200RPM, the pressure is 100-750Torr, and the Si doping concentration is about 1E19-1E20 .

S105 , growing a stress release layer on the N-type AlGaN; the thickness is 0.15-0.3um, the temperature is 700-1000° C., the rotational speed is 500-1200RPM, and the pressure is 100-750Torr.

S106, growing a high-temperature quantum well structure (InGaN/ALGaN quantum well structure) on the stress release layer, where the high-temperature quantum well structure consists of 3-7 periods, a thickness of 0.05-0.25um, a temperature of 850-900° C., and a rotational speed of 600- 800RPM, pressure 100-750Torr.

S107, on the high-temperature quantum well structure, a light-emitting quantum well structure (InGaN/ALGaN quantum well structure), consisting of 10-12 periods, a thickness of 0.1-1.0um, a temperature of 850-950°C, and a rotational speed of 600-800RPM, Pressure 100-750Torr. The two quantum wells set up in succession here, the former is high temperature and the latter is low temperature. The direct growth of low-temperature quantum wells in the reaction chamber after 1000 degrees will affect the quality of the quantum wells, so an MQW structure is added in the middle, and the temperature is about 850 degrees. The purpose is to reduce the temperature of the chamber slowly, so as to ensure Crystal quality of quantum well temperature in the light-emitting region.

S108, growing a novel barrier layer on the light-emitting quantum well structure, the barrier layer comprising a plurality of cycles of (AlN/AL _x Ga _(1-x) N/AL _a In _b Ga _(1-ab) N ), a specific embodiment may consist of 6-15 cycles, the thickness is 0.01-1.0um, the temperature is 850-900°C, the rotational speed is 600-800RPM, the pressure is 50-500Torr, and the reaction chamber is used. The above-mentioned barrier layer can effectively confine the Stark effect QCS in the quantum well structure. As a further embodiment, the composition of the AlGaN barrier layer is an (AlN/Mg-doped ALxGa(1- _{x )} N/ _ALaInbGa (1- _{ab )} N) structure. At the same time, the Mg-doped AL _x Ga _(1-x) N in the cyclic structure increases the two-dimensional electron gas at the material interface, thereby improving the ability of holes to be injected into the light-emitting region and improving the recombination efficiency of electrons and holes in the light-emitting region.

S109, growing a P-type AlGaN structure on the barrier layer structure, with a thickness of 20nm-100nm, and a Mg doping concentration of 1E20-5E20;

S110 , growing heavily doped P-type ALGaN on the growing P-type AlGaN, the purpose of adding heavily doped P-type ALGaN is to make a metal electrode on the ALGaN semiconductor material in the chip fabrication process, which can form a good gold half Contact, the layer thickness is 5-10nm, the Mg doping concentration is 4E21, and the pressure is 400-800Torr. When making such a heavily doped P-type ALGaN structure, in a preferred embodiment, the pressure can be selected to be 650 Torr. Under this condition, the doping efficiency of Mg in the ALGaN material is the best, which can be achieved by reducing the Mg source in the production process. Therefore, the incorporation of Mg-containing by-products into the ALGaN material can be reduced, thereby reducing the scattering of light by Mg by-products to a certain extent, thereby improving the light extraction efficiency.

Finally, the above-mentioned ALGaN material is annealed in the N2 environment to complete the growth of the violet LED epitaxial wafer.

In some further embodiments, the composition of the barrier layer is also modified to (Aluminum Nitride/MgNb doped ALxGa(1- _{x )} N/ _ALaInbGa (1- _{ab )} N), the intermediate layer Doping Mg and Nb elements can better improve the two-dimensional electron gas at the material interface, thereby improving the ability of holes to inject into the light-emitting region. Nb doping is one of the metal dopants selected by our company. Improve the doping conditions and add Nb element, the doping will affect the blocking effect, and the hole injection ability will be affected. After thousands of experiments in our scheme, it is concluded that a small amount of niobium and Mg doping can solve the hole injection ability. Compared with the LED with the ALN/ALGaN barrier layer in the prior art, the luminous capacity is improved by 5%-35%.

In the embodiment shown in Figure 2, the present solution also provides an epitaxial structure of a violet LED, comprising the following parts grown sequentially on the substrate 1:

ALN film 2;

AlGaN buffer layer 3;

undoped aluminum gallium nitride layer 4;

N-type aluminum gallium nitride layer 5;

stress release layer 6;

High temperature quantum well structure 7;

Light-emitting quantum well structure 8;

A barrier layer 9, the barrier layer is an AlGaN barrier layer, including a plurality of cycles (Aluminum Nitride/AL _x Ga _(1-x) N/AL _a In _b Ga _(1-ab) N);

P-type AlGaN structure 10;

Heavily doped P-type ALGaN 11.

The above epitaxial structure is designed by the ALN film, and the specific thickness can be set between 10-25nm, the purpose is to reduce the stress and defects caused by the lattice mismatch between the sapphire and the ALGaN material, thereby improving the crystal quality of the subsequently grown ALGaN material. . The Stark effect QCS in the quantum well structure can also be effectively limited by designing the AlGaN barrier layer (including AlN/AL _x Ga _(1-x) N/AL _a In _b Ga _(1-ab) N) structure , thereby improving the light efficiency of the violet LED epitaxial wafer.

In a further embodiment, the substrate of the structure is an M-type sapphire substrate.

Specifically, the AlGaN barrier layer includes multiple cycles of (AlN/Mg-doped ALxGa(1- _{x )} N/ _ALaInbGa (1- _{ab )} N).

Specifically, the thickness of the heavily doped P-type ALGaN layer is 5-10 nm, and the doping type is Mg doping. The doping efficiency of Mg in ALGaN materials is the best. By reducing the amount of Mg source used in the production process, the incorporation of Mg-containing by-products into ALGaN materials can be reduced, thereby reducing the scattering of light by Mg by-products to a certain extent. Thus, the light extraction efficiency is improved.

It should be noted that, although the above-mentioned embodiments have been described herein, it does not limit the scope of the patent protection of the present invention. Therefore, based on the innovative concept of the present invention, changes and modifications to the embodiments described herein, or equivalent structures or equivalent process transformations made by using the contents of the description and drawings of the present invention, directly or indirectly apply the above technical solutions In other related technical fields, all are included in the protection scope of the patent of the present invention.

Claims (9)

1. A method for manufacturing an epitaxial structure of a purple light LED is characterized by comprising the following steps,

s100, sputtering an ALN film on a substrate;

s102, growing an AlGaN buffer layer on the ALN film;

s103, growing a non-doped aluminum gallium nitrogen layer on the aluminum gallium nitrogen buffer layer;

s104, growing a layer of N-type AlGaN on the undoped AlGaN;

s105, growing a stress release layer on the N-type AlGaN;

s106, growing a high-temperature quantum well structure on the stress release layer;

s107, growing a light-emitting quantum well structure on the high-temperature quantum well structure;

s108, in the luminescent quantum wellStructurally growing a barrier layer, said barrier layer being an AlGaN barrier layer comprising a plurality of cycles (aluminum nitride/AL)_xGa_(1-x)N/AL_aIn_bGa_(1-a-b)N)；

S109, growing a P-type aluminum gallium nitrogen structure on the barrier layer structure;

and S110, growing heavily doped P-type ALGaN on the grown P-type AlGaN.

2. The method for fabricating an epitaxial structure of a violet LED according to claim 1, wherein the step S100 is followed by a step of performing a high temperature treatment on the ALN thin film buffer layer by MOCVD at a temperature of 1200 ℃ to 1300 ℃, a rotation speed of 1000 ℃ to 1200RPM, and a pressure of 200 ℃ to 750 Torr.

3. The method for fabricating an epitaxial structure of a violet LED according to claim 1,

step S100 is specifically to sputter an ALN film with the thickness of 10-25nm on the sapphire substrate by using PECVD equipment.

4. The method of claim 1, wherein the AlGaN barrier layer comprises multiple cycles of (aluminum nitride/Mg doped AL)_xGa_(1-x)N/AL_aIn_bGa_(1-a-b)N)。

5. The method as claimed in claim 1, wherein the heavily doped P-type ALGaN layer in step S110 has a thickness of 5-10nm, a Mg doping concentration of 4E21, and a pressure of 400-800 Torr.

6. An epitaxial structure of a purple light LED is characterized by comprising the following parts which are sequentially grown on a substrate:

an ALN film;

an AlGaN buffer layer;

an undoped aluminum gallium nitride layer;

an N-type AlGaN layer;

a stress release layer;

a high temperature quantum well structure;

a light emitting quantum well structure;

a barrier layer, the barrier layer being an AlGaN barrier layer comprising a plurality of cycles of (aluminum nitride/AL)_xGa_(1-x)N/AL_aIn_bGa_(1-a-b)N)；

A P-type AlGaN structure;

and heavily doping the P-type ALGaN.

7. The epitaxial structure of a violet LED of claim 6, wherein the substrate is a sapphire substrate.

8. Epitaxial structure for violet LED according to claim 6, characterized in that the aluminum gallium nitride barrier layer comprises multiple cycles (aluminum nitride/Mg doped AL)_xGa_(1-x)N/AL_aIn_bGa_(1-a-b)N)。

9. The epitaxial structure of a violet LED of claim 6, wherein the heavily doped P-type ALGaN layer is 5-10nm thick and the doping type is Mg doping.

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