CN113540296B - Manufacturing method of LED epitaxial wafer suitable for small-space display screen - Google Patents

Abstract

The application discloses a manufacturing method of an LED epitaxial wafer suitable for a small-space display screen, which sequentially comprises the following steps: the method comprises the steps of processing a substrate, growing a low-temperature GaN buffer layer, growing an undoped GaN layer, growing an N-type GaN layer doped with Si, growing a multi-quantum well layer, growing an AlGaN electron blocking layer and growing a P-type GaN layer doped with Mg, and cooling, wherein the growing of the multi-quantum well layer sequentially comprises the steps of introducing a TMIn source, growing MQWs1 and growing MQWs2, the growing of the MQWs1 comprises the steps of sequentially growing an InGaN well layer and an In _xAl_yMg_(1‑x‑y) layer, and the growing of the MQWs2 comprises the steps of sequentially growing a GaO layer and a GaN barrier layer. The application reduces the blue shift of the wavelength and improves the brightness of the LED by adopting a novel manufacturing method of the LED epitaxial wafer, and is particularly suitable for manufacturing a small-space display screen.

Description

LED epitaxial wafer manufacturing method suitable for small pitch display screen

Technical Field

The invention belongs to the technical field of LEDs, and in particular relates to a method for manufacturing an LED epitaxial wafer suitable for a small-pitch display screen.

Background technique

Light-Emitting Diode (LED) is a semiconductor electronic device that converts electrical energy into light energy. When current flows through the LED, the electrons and holes in the LED recombine in its multi-quantum wells to emit monochromatic light. As a new type of efficient, environmentally friendly, green solid-state lighting source, LED is currently widely used for indoor and outdoor lighting, as well as traffic lights, car lights, indoor and outdoor lighting, and small-pitch display screens.

In the current LED quantum well growth method, the bandgap width of the material is limited, the ground state in the quantum well increases, and the LED's emission wavelength tends to move toward the short-wave direction, that is, blue shift occurs. When different currents are injected into the small-pitch display to change the luminous intensity, the amount of blue shift of the LED's emission wavelength will vary greatly, which cannot meet the application needs of small-pitch display screens.

In summary, it is urgent to develop new LED chip manufacturing methods to reduce wavelength blue shift and increase LED brightness to meet the application needs of small-pitch display screens.

Summary of the invention

The invention adopts a new method for manufacturing LED epitaxial wafers to reduce wavelength blue shift and improve the brightness of LEDs.

The method for manufacturing an LED epitaxial wafer suitable for a small pitch display screen of the present invention comprises the following steps: processing a substrate, growing a low-temperature GaN buffer layer, growing a non-doped GaN layer, growing a Si-doped N-type GaN layer, growing a multi-quantum well layer, growing an AlGaN electron blocking layer, growing a Mg-doped P-type GaN layer, and cooling the substrate.

The growing of the multi-quantum well layer includes: introducing a TMIn source, growing MQWs1 and growing MQWs2 in sequence; wherein,

The introduction of the TMIn source is specifically:

The reaction chamber pressure is controlled at 300-320 mbar, the reaction chamber temperature is controlled at 680-700°C, and 600-700 sccm of TMIn source is introduced for 10-20 seconds;

The growing of MQWs1 includes sequentially growing an InGaN _well layer and an _{InxAlyMg (1-xy)} layer, specifically:

The pressure in the reaction chamber remains unchanged, the temperature of the reaction chamber is increased to 900-950°C, NH ₃ , TMGa and TMIn are introduced, and the In source and Ga source are periodically interrupted to grow an InGaN well layer with a thickness of D _1. During the growth of the InGaN well layer, the time for TMIn to be interrupted and introduced into the reaction chamber is 6s and 3s respectively, and the time for TMGa to be interrupted and introduced into the reaction chamber is 10s and 15s respectively;

The reaction chamber pressure remains unchanged, the reaction chamber temperature is reduced to 700-720°C, TMIn, Cp ₂ Mg, TMAl and H ₂ are introduced, and an In _{x Aly} Mg _(1-xy) layer with a thickness of D ₂ is grown on the InGaN well layer, where the value range of x is 0.1-0.2 and the value range of y is 0.3-0.45;

The growing of MQWs2 includes sequentially growing a GaO layer and a GaN barrier layer, specifically:

Keeping the pressure of the reaction chamber unchanged, lowering the temperature of the reaction chamber to 620°C-640°C, introducing _N2 and _H2 as carrier gases, and introducing _NH3 , TMGa and _O2 at the same time for 18-28s, allowing TMGa and _O2 to be fully cracked, so that the cracked Ga and O atoms are combined on _{the InxAlyMg (1-xy)} layer to form a GaO layer with a thickness of _D3 , and the molar content of Ga atoms is increased from 20% to 40% during the cracking process, and the cracked H, N, and C atoms are transported to the tail pipe with the carrier gas to be discharged from the reaction chamber;

The temperature of the reaction chamber is increased to 800-820°C, the pressure of the reaction chamber is increased to 400-440 mbar, NH ₃ , TMGa and N ₂ are introduced, and the Ga source is periodically interrupted to grow a GaN barrier layer with a thickness of D ₄ on the GaO layer. During the growth of the GaN barrier layer, the time for TMGa to be interrupted and introduced into the reaction chamber is 8s and 4s respectively;

Wherein, D ₃ +D ₄ =1.5(D ₁ +D ₂ );

The steps of introducing TMIn source, growing MQWs1 and growing MQWs2 are performed periodically in sequence, and the number of cycles is 2-11.

Preferably, the specific process of processing the substrate is:

At a temperature of 1000° C. to 1100° C., 100-130 L/min of H ₂ is introduced, the pressure in the reaction chamber is maintained at 100-300 mbar, and the sapphire substrate is treated for 5-10 minutes.

Preferably, the specific process of growing the low-temperature GaN buffer layer is:

Cooling to 500-600°C, maintaining the reaction chamber pressure at 300-600 mbar, introducing 10000-20000 sccm of NH ₃ , 50-100 sccm of TMGa and 100-130 L/min of H ₂ , growing a low-temperature GaN buffer layer with a thickness of 20-40 nm on a sapphire substrate;

The temperature is raised to 1000-1100°C, the pressure of the reaction chamber is maintained at 300-600 mbar, NH ₃ with a flow rate of 30000-40000 sccm and H ₂ with a flow rate of 100-130 L/min are introduced, and the temperature is kept for 300-500 seconds to etch the low-temperature GaN buffer layer into irregular islands.

Preferably, the specific process of growing the undoped GaN layer is:

The temperature is raised to 1000-1200° C., the pressure of the reaction chamber is maintained at 300-600 mbar, NH ₃ at a flow rate of 30000-40000 sccm, TMGa at a flow rate of 200-400 sccm and H ₂ at a flow rate of 100-130 L/min are introduced, and a 2-4 μm non-doped GaN layer is continuously grown.

Preferably, the specific process of growing the Si-doped GaN layer is:

The reaction chamber pressure is maintained at 300-600 mbar, the temperature is maintained at 1000-1200°C, NH ₃ with a flow rate of 30000-60000 sccm, TMGa with a flow rate of 200-400 sccm, H ₂ with a flow rate of 100-130 L/min, and SiH ₄ with a flow rate of 20-50 sccm, and a 3m-4μm Si-doped N-type GaN layer is continuously grown, wherein the Si doping concentration is 5E18-5E19 atoms/cm ³ .

Preferably, the specific process of growing the AlGaN electron blocking layer is:

The AlGaN electron blocking layer is grown at a temperature of 900-950°C, a reaction chamber pressure of 200-400 mbar, and 50000-70000 sccm of NH ₃ , 30-60 sccm of TMGa, 100-130 L/min of H ₂ , 100-130 sccm of TMAl, and 1000-1300 sccm of Cp ₂ Mg are introduced. The thickness of the AlGaN layer is 40-60 nm, and the concentration of Mg doping is 1E19-1E20 atoms/cm ³ .

Preferably, the specific process of growing the Mg-doped P-type GaN layer is:

The reaction chamber pressure is maintained at 400-900 mbar and the temperature is maintained at 950-1000°C. 50000-70000 sccm of NH ₃ , 20-100 sccm of TMGa, 100-130 L/min of H ₂ and 1000-3000 sccm of Cp ₂ Mg are introduced to continuously grow a 50-200 nm Mg-doped P-type GaN layer, wherein the Mg doping concentration is 1E19-1E20 atoms/cm ³ .

Preferably, the specific process of cooling down is:

Cool down to 650-680℃, keep warm for 20-30min, turn off the heating system and gas supply system, and cool with the furnace.

Compared with the traditional growth method, the LED epitaxial wafer manufacturing method suitable for small pitch display screens in the present invention achieves the following effects:

1. The present invention introduces a TMIn source before growing the InGaN quantum well, which is beneficial to repairing the rough interface of the InGaN quantum well and inhibits the formation of defects such as V-shaped pits and In clusters in the InGaN quantum well, thereby improving the growth quality of the quantum well.

2. The present invention adopts a method of periodically interrupting the In source and the Ga source to grow the InGaN well layer, so that the luminous intensity of the LED is significantly improved. This can be explained by the fact that in the process of growing the InGaN quantum well by the traditional method, due to insufficient N source, In clusters, In droplets, etc. are easily formed on the growth interface. When the In source and the Ga source are turned off to interrupt the growth process, thermal decomposition and the continued supply of N source help to eliminate defects such as In clusters and In droplets on the surface, thereby improving the quality of the quantum well and enhancing the photoelectric performance of the LED.

3. The present invention adopts a cracking method to introduce a growing GaO layer in the quantum well layer, and controls the molar content of Ga atoms to increase from 20% to 40% during the cracking process, which can cause the center of mass of the Ga atom set and the N atom set in the multi-quantum well layer to coincide, thereby forming a dipole, generating spontaneous polarization inside the layer material, and forming a built-in electric field. The built-in electric field will promote the injection of carriers in the quantum well, reduce the quantum-confined Stark effect, make the energy band smooth, and thus reduce the wavelength blue shift.

4. The present invention inserts an In _{x Aly} Mg _(1-xy) layer after the InGaN well layer. Since Al atoms have a lower principal quantum number and a wider orbital energy gap than In atoms, due to the linear merging effect of atomic orbitals, Al atoms will form "Al-In" bonds (or "In-Mg-Al" bonds) in In _{x Aly} Mg _(1-xy) , which will increase the bandgap width of InGaN, cause the ground state in the quantum well to decrease, and reduce the light emitting wavelength of the LED to move toward the short-wave direction, thereby reducing the wavelength blue shift.

5. The present invention divides the active area quantum well structure into two groups, in which the thickness of MQWs2 is 1.5 times the thickness of MQWs1, which can improve the lattice periodicity of the epitaxial wafer material and the material interface characteristics, thereby improving the performance of the LED, and can also promote the overlap of the distribution center axes of holes and electrons in the multi-quantum wells, improve the efficiency of electron-to-hole transition, and thus improve the luminous efficiency of the LED chip.

6. The present invention adopts the method of periodically interrupting the Ga source to grow the GaN barrier layer, which can effectively reduce material growth defects and improve the crystal quality of the key luminescent MQWs2. This method can increase the brightness by about 1.5% compared with the traditional GaN barrier layer growth method.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

FIG1 is a schematic diagram of the structure of an LED epitaxially prepared by the method of the present invention;

FIG2 is a schematic diagram of the structure of an LED epitaxially prepared by an existing conventional method;

Among them, 1. sapphire substrate, 2. low-temperature GaN buffer layer, 3. undoped GaN layer, 4. N-type GaN layer, 5. multi-quantum well layer, 6. AlGaN electron blocking layer, 7. P-type GaN layer, 51. InGaN well layer, 52. In _{x AlyMg (1-xy)} layer, 53. GaO layer, 54. GaN barrier layer.

Detailed ways

For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different nouns to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criteria for distinction. As mentioned throughout the specification and claims, "including" is an open term, so it should be interpreted as "including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve the technical problem within a certain error range and basically achieve the technical effect. The subsequent description of the specification is a preferred embodiment of the present application, but the description is for the purpose of illustrating the general principles of the present application, and is not used to limit the scope of the present application. The scope of protection of the present application shall be determined by the attached claims.

In addition, this specification does not limit the components and method steps disclosed in the claims to the components and method steps of the embodiments. In particular, the size, material, shape, structural order and adjacent order, and manufacturing method of the structural components described in the embodiments are only illustrative examples unless specifically limited thereto, and the scope of the present invention is not limited thereto. The size and positional relationship of the structural components shown in the drawings are enlarged for the purpose of clear description.

The present application is further described in detail below in conjunction with the accompanying drawings, but is not intended to limit the present application.

Example 1

This embodiment adopts the method for manufacturing LED epitaxial wafers suitable for small-pitch display screens provided by the present invention, adopts MOCVD to grow GaN-based LED epitaxial wafers, adopts high-purity H ₂ or high-purity N ₂ or a mixture of high-purity H ₂ and high-purity N ₂ as carrier gas, high-purity NH ₃ as N source, metal organic source trimethyl gallium (TMGa) as gallium source, trimethyl indium (TMIn) as indium source, N-type dopant is silane (SiH ₄ ), trimethyl aluminum (TMAl) as aluminum source, P-type dopant is bis(cyclopentadienyl) magnesium (CP ₂ Mg), and the reaction pressure is between 70mbar and 600mbar. The specific growth method is as follows (please refer to Figure 1 for the epitaxial structure):

The method for manufacturing LED epitaxial wafers suitable for small-pitch display screens comprises: processing a sapphire substrate 1, growing a low-temperature GaN buffer layer 2, growing a non-doped GaN layer 3, growing a Si-doped N-type GaN layer 4, growing a multi-quantum well layer 5, growing an AlGaN electron barrier layer 6, growing a Mg-doped P-type GaN layer 7, and cooling down; wherein,

Step 1: Processing a sapphire substrate 1.

Specifically, the step 1 is further as follows:

The sapphire substrate is treated for 5-10 minutes at a temperature of 1000-1100°C, a reaction chamber pressure of 100-300 mbar, and a flow of 100-130 L/min of _H2 .

Step 2: growing a low-temperature GaN buffer layer 2 and forming irregular islands in the low-temperature GaN buffer layer 2 .

Specifically, the step 2 is further as follows:

Growing the low-temperature GaN buffer layer 2 on the sapphire substrate 1 at a temperature of 500-600° C., a reaction chamber pressure of 300-600 mbar, and introducing 10000-20000 sccm of NH ₃ , 50-100 sccm of TMGa, and 100-130 L/min of H ₂ , wherein the thickness of the low-temperature GaN buffer layer 2 is 20-40 nm;

Under the conditions of a temperature of 1000-1100° C., a reaction chamber pressure of 300-600 mbar, introduction of 30000-40000 sccm of NH ₃ and 100-130 L/min of H ₂ , and preservation for 300-500 seconds, the irregular islands are formed on the low-temperature GaN buffer layer 2 .

Step 3: growing a non-doped GaN layer 3.

Specifically, the step 3 is further as follows:

The undoped GaN layer 3 is grown at a temperature of 1000-1200° C., a reaction chamber pressure of 300-600 mbar, and 30000-40000 sccm of NH ₃ , 200-400 sccm of TMGa, and 100-130 L/min of H ₂ ; the thickness of the undoped GaN layer 3 is 2-4 μm.

Step 4: growing a Si-doped N-type GaN layer 4.

Specifically, the step 4 is further as follows:

The reaction chamber pressure is maintained at 300-600 mbar, the temperature is maintained at 1000-1200°C, NH ₃ with a flow rate of 30000-60000 sccm, TMGa with a flow rate of 200-400 sccm, H ₂ with a flow rate of 100-130 L/min, and SiH ₄ with a flow rate of 20-50 sccm, and a 3-4 μm Si-doped N-type GaN layer 4 is continuously grown, wherein the Si doping concentration is 5E18-1E19 atoms/cm ³ .

Step 5: growing a multi-quantum well layer 5.

The growing of the multi-quantum well layer includes: introducing a TMIn source, growing MQWs1 and growing MQWs2 in sequence; wherein,

The introduction of the TMIn source is specifically:

The reaction chamber pressure is controlled at 300-320 mbar, the reaction chamber temperature is controlled at 680-700°C, and 600-700 sccm of TMIn source is introduced for 10-20 seconds;

The growing of MQWs1 includes sequentially growing an InGaN well layer 51 and _{an InxAlyMg (1-xy)} layer 52, specifically:

The pressure in the reaction chamber remains unchanged, the temperature of the reaction chamber is increased to 900-950°C, NH ₃ , TMGa and TMIn are introduced, and the In source and Ga source are periodically interrupted to grow an InGaN well layer 51 with a thickness of D _1. During the growth of the InGaN well layer 51, the time for TMIn to be interrupted and introduced into the reaction chamber is 6s and 3s respectively, and the time for TMGa to be interrupted and introduced into the reaction chamber is 10s and 15s respectively;

The reaction chamber pressure remains unchanged, the reaction chamber temperature is reduced to 700-720°C, TMIn, Cp ₂ Mg, TMAl and H ₂ are introduced, and an In _{x Aly} Mg _(1-xy) layer 52 with a thickness of D ₂ is grown on the InGaN well layer 51, where the value range of x is 0.1-0.2, and the value range of y is 0.3-0.45;

The growing of MQWs2 includes sequentially growing a GaO layer 53 and a GaN barrier layer 54, specifically:

Keeping the pressure of the reaction chamber unchanged, lowering the temperature of the reaction chamber to 620°C-640°C, introducing _N2 and _H2 as carrier gases, and introducing _NH3 , TMGa and _O2 at the same time for 18-28s, allowing TMGa and _O2 to be fully cracked, so that the cracked Ga and O atoms are combined on _{the InxAlyMg (1-xy)} layer 52 to form a GaO layer 53 with a thickness of _D3 . During the cracking process, the molar content of Ga atoms is increased from 20% to 40%, and at the same time, the cracked H, N, and C atoms are transported to the tail pipe with the carrier gas to be discharged from the reaction chamber;

The temperature of the reaction chamber is increased to 800-820°C, the pressure of the reaction chamber is increased to 400-440 mbar, NH ₃ , TMGa and N ₂ are introduced, and the Ga source is periodically interrupted to grow a GaN barrier layer 54 with a thickness of D ₄ on the GaO layer 53. During the growth of the GaN barrier layer 54, the time for TMGa to be interrupted and introduced into the reaction chamber is 8s and 4s respectively;

Wherein, D3+D4=1.5(D1+D2);

The steps of introducing TMIn source, growing MQWs1 and growing MQWs2 are performed periodically in sequence, and the number of cycles is 2-11.

Step 6: growing an AlGaN electron blocking layer 6 .

Specifically, the step 6 is further as follows:

The AlGaN electron blocking layer 6 is grown at a temperature of 900-950°C, a reaction chamber pressure of 200-400 mbar, and 50000-70000 sccm of NH ₃ , 30-60 sccm of TMGa, 100-130 L/min of H ₂ , 100-130 sccm of TMAl, and 1000-1300 sccm of Cp ₂ Mg. The thickness of the AlGaN layer 6 is 40-60 nm, and the concentration of Mg doping is 1E19-1E20 atoms/cm ³ .

Step 7: growing a Mg-doped P-type GaN layer 7 .

Specifically, the step 7 is further as follows:

Under the conditions of 950-1000°C, 400-900mbar reaction chamber pressure, 50000-70000sccm _NH3 , 20-100sccm TMGa, 100-130L/min _H2 , 1000-3000sccm _Cp2Mg , a Mg-doped P-type GaN layer 7 with a thickness of 50-200nm is grown, and the Mg doping concentration is 1E19-1E20atoms/ ^cm3 .

Step 8: Keep the temperature at 650-680℃ for 20-30min, then turn off the heating system and the gas supply system, and cool with the furnace.

Example 2

The following is a comparative example, ie, a conventional method for growing an LED epitaxial structure (please refer to FIG. 2 for the epitaxial structure).

Step 1: Treat the sapphire substrate for 5-10 minutes at a temperature of 1000-1100°C, a reaction chamber pressure of 100-300 mbar, and a flow of 100-130 L/min of _H2 .

Step 2: growing a low-temperature GaN buffer layer 2 and forming irregular islands in the low-temperature GaN buffer layer 2 .

Specifically, the step 2 is further as follows:

Growing the low-temperature GaN buffer layer 2 on the sapphire substrate 1 at a temperature of 500-600° C., a reaction chamber pressure of 300-600 mbar, and introducing 10000-20000 sccm of NH ₃ , 50-100 sccm of TMGa, and 100-130 L/min of H ₂ , wherein the thickness of the low-temperature GaN buffer layer 2 is 20-40 nm;

The irregular islands are formed on the low-temperature GaN buffer layer 2 at a temperature of 1000-1100° C., a reaction chamber pressure of 300-600 mbar, and 30000-40000 sccm of NH ₃ and 100-130 L/min of H ₂ are introduced for 300-500 seconds.

Step 3: growing a non-doped GaN layer 3.

Specifically, the step 3 is further as follows:

The undoped GaN layer is grown at a temperature of 1000-1200° C., a reaction chamber pressure of 300-600 mbar, and 30000-40000 sccm of NH ₃ , 200-400 sccm of TMGa, and 100-130 L/min of H ₂ ; the thickness of the undoped GaN layer 3 is 2-4 μm.

Step 4: growing a Si-doped N-type GaN layer 4.

Specifically, the step 4 is further as follows:

Under the conditions of temperature of 1000-1200°C, reaction chamber pressure of 300-600mbar, introduction of 30000-60000sccm of NH ₃ , 200-400sccm of TMGa, 100-130L/min of H ₂ , and 20-50sccm of SiH ₄ , a Si-doped N-type GaN layer 4 is grown, wherein the thickness of the N-type GaN layer 4 is 3-4μm, and the Si doping concentration is 5E18-1E19atoms/cm ³ .

Step 5: growing an InGaN/GaN multi-quantum well layer 5 .

Specifically, the growing of the multi-quantum well layer 5 is further performed as follows:

The reaction chamber pressure is maintained at 300-400 mbar and the temperature is maintained at 720° C. NH ₃ with a flow rate of 50000-70000 sccm, TMGa with a flow rate of 20-40 sccm, TMIn with a flow rate of 10000-15000 sccm and N ₂ with a flow rate of 100-130 L/min is introduced to grow an InGaN well layer 51 doped with In with a thickness of 3 nm;

Raise the temperature to 800° C., maintain the reaction chamber pressure at 300-400 mbar, introduce 50000-70000 sccm of NH ₃ , 20-100 sccm of TMGa and 100-130 L/min of N ₂ , and grow a 10 nm GaN barrier layer 54;

The InGaN well layer 51 and the GaN barrier layer 54 are repeatedly grown alternately to obtain an InGaN/GaN multi-quantum well light-emitting layer, wherein the number of the alternate growth cycles of the InGaN well layer 51 and the GaN barrier layer 54 is 7-13.

Step 6: growing an AlGaN electron blocking layer 6 .

Specifically, the step 6 is further as follows:

The AlGaN electron blocking layer 6 is grown at a temperature of 900-950°C, a reaction chamber pressure of 200-400 mbar, and 50000-70000 sccm of NH ₃ , 30-60 sccm of TMGa, 100-130 L/min of H ₂ , 100-130 sccm of TMAl, and 1000-1300 sccm of Cp ₂ Mg. The thickness of the AlGaN layer 6 is 40-60 nm, and the concentration of Mg doping is 1E19-1E20 atoms/cm ³ .

Step 7: growing a Mg-doped P-type GaN layer 7 .

Specifically, the step 7 is further as follows:

Under the conditions of 950-1000°C, 400-900mbar reaction chamber pressure, 50000-70000sccm _NH3 , 20-100sccm TMGa, 100-130L/min _H2 , 1000-3000sccm _Cp2Mg , a Mg-doped P-type GaN layer 7 with a thickness of 50-200nm is grown, and the Mg doping concentration is 1E19-1E20atoms/ ^cm3 .

Step 8: Keep the temperature at 650-680℃ for 20-30min, then turn off the heating system and the gas supply system, and cool with the furnace.

According to the above-mentioned Example 1 and Example 2, Sample 1 and Sample 2 were prepared respectively. Sample 1 and Sample 2 were plated with an ITO layer of about 150nm under the same pre-process conditions, Cr/Pt/Au electrodes of about 1500nm under the same conditions, and a protective layer of SiO ₂ of about 100nm under the same conditions. Then, the samples were ground and cut into 635μm*635μm (25mil*25mil) chip particles under the same conditions. Then, 1000 grains were selected from Sample 1 and Sample 2 at the same position, and packaged into white light LEDs under the same packaging process. The photoelectric performance of Sample 1 and Sample 2 was tested using an integrating sphere under the condition of a driving current of 350mA.

Table 1 Comparison of electrical parameters of sample 1 and sample 2

The data obtained by the integrating sphere are analyzed and compared. It can be seen from Table 1 that the luminous efficiency of the LED (Sample 1) prepared by the LED chip manufacturing method provided by the present invention is significantly improved, and the wavelength blue shift is smaller, and other LED electrical parameters such as voltage, reverse voltage, and antistatic ability are also improved. This is because the patent adopts a new quantum well growth technology solution, which improves the luminous efficiency of the LED, reduces the wavelength blue shift, and improves other LED photoelectric properties.

The LED epitaxial wafer manufacturing method suitable for small pitch display screens of the present invention achieves the following effects:

1. The present invention introduces a TMIn source before growing the InGaN quantum well, which is beneficial to repairing the rough interface of the InGaN quantum well and inhibits the formation of defects such as V-shaped pits and In clusters in the InGaN quantum well, thereby improving the growth quality of the quantum well.

2. The present invention adopts a method of periodically interrupting the In source and the Ga source to grow the InGaN well layer, so that the luminous intensity of the LED is significantly improved. This can be explained by the fact that in the process of growing the InGaN quantum well by the traditional method, due to insufficient N source, In clusters, In droplets, etc. are easily formed on the growth interface. When the In source and the Ga source are turned off to interrupt the growth process, thermal decomposition and the continued supply of N source help to eliminate defects such as In clusters and In droplets on the surface, thereby improving the quality of the quantum well and enhancing the photoelectric performance of the LED.

3. The present invention adopts a cracking method to introduce a growing GaO layer in the quantum well layer, and controls the molar content of Ga atoms to increase from 20% to 40% during the cracking process, which can cause the center of mass of the Ga atom set and the N atom set in the multi-quantum well layer to coincide, thereby forming a dipole, generating spontaneous polarization inside the layer material, and forming a built-in electric field. The built-in electric field will promote the injection of carriers in the quantum well, reduce the quantum-confined Stark effect, make the energy band smooth, and thus reduce the wavelength blue shift.

4. The present invention inserts an In _{x Aly} Mg _(1-xy) layer after the InGaN well layer. Since Al atoms have a lower principal quantum number and a wider orbital energy gap than In atoms, due to the linear merging effect of atomic orbitals, Al atoms will form "Al-In" bonds (or "In-Mg-Al" bonds) in In _{x Aly} Mg _(1-xy) , which will increase the bandgap width of InGaN, cause the ground state in the quantum well to decrease, and reduce the light emitting wavelength of the LED to move toward the short-wave direction, thereby reducing the wavelength blue shift.

5. The present invention divides the active area quantum well structure into two groups, in which the thickness of MQWs2 is 1.5 times the thickness of MQWs1, which can improve the lattice periodicity of the epitaxial wafer material and the material interface characteristics, thereby improving the performance of the LED, and can also promote the overlap of the distribution center axes of holes and electrons in the multi-quantum wells, improve the efficiency of electron-to-hole transition, and thus improve the luminous efficiency of the LED chip.

6. The present invention adopts the method of periodically interrupting the Ga source to grow the GaN barrier layer, which can effectively reduce material growth defects and improve the crystal quality of the key luminescent MQWs2. This method can increase the brightness by about 1.5% compared with the traditional GaN barrier layer growth method.

Since the method part has described the embodiment of the present application in detail, the expanded description of the structure and method corresponding parts involved in the embodiment is omitted here and will not be repeated. For the description of the specific content in the structure, please refer to the content of the method embodiment, which is not specifically limited here.

The above description shows and describes several preferred embodiments of the present application, but as mentioned above, it should be understood that the present application is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the application concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not deviate from the spirit and scope of the present application, and should be within the scope of protection of the claims attached to the present application.

Claims (8)

1. The manufacturing method of the LED epitaxial wafer suitable for the small-space display screen is characterized by comprising the following steps of: treating a substrate, growing a low-temperature GaN buffer layer, growing an undoped GaN layer, growing an N-type GaN layer doped with Si, growing a multi-quantum well layer, growing an AlGaN electron blocking layer, growing a P-type GaN layer doped with Mg, cooling,

The growing multiple quantum well layer sequentially comprises: introducing TMIn source, growing MQWs1 and growing MQWs2; wherein,

The TMIn source is introduced, specifically:

Controlling the pressure of the reaction cavity at 300-320mbar, controlling the temperature of the reaction cavity at 680-700 ℃, and introducing a TMIn source of 600-700sccm for 10-20s;

The growing of the MQWs1 comprises the sequential growth of an InGaN well layer and an In _xAl_yMg_(1-x-y) layer, and specifically comprises the following steps:

The pressure of the reaction cavity is kept unchanged, the temperature of the reaction cavity is increased to 900-950 ℃, NH ₃, TMGa and TMIn are introduced, an InGaN well layer with the thickness of D ₁ is grown by periodically interrupting an In source and a Ga source, in the growth process of the InGaN well layer, the time for interrupting the TMIn and introducing the reaction cavity is 6s and 3s respectively, and the time for interrupting the TMGa and introducing the reaction cavity is 10s and 15s respectively;

The pressure of the reaction cavity is kept unchanged, the temperature of the reaction cavity is reduced to 700-720 ℃, TMIn, cp ₂ Mg, TMAL and H ₂ are introduced, an In _xAl_yMg_(1-x-y) layer with the thickness of D ₂ is grown on the InGaN well layer, the value range of x is 0.1-0.2, and the value range of y is 0.3-0.45;

the growing of the MQWs2 comprises the steps of sequentially growing a GaO layer and a GaN barrier layer, and specifically comprises the following steps:

Keeping the pressure of the reaction cavity unchanged, reducing the temperature of the reaction cavity to 620-640 ℃, introducing N ₂ and H ₂ as carrier gas, simultaneously introducing NH ₃, TMGa and O ₂ for 18-28s, cracking TMGa and O ₂, combining the cracked Ga and O atoms on the In _xAl_yMg_(1-x-y) layer to generate a GaO layer with the thickness of D ₃, increasing the molar content of Ga atoms from 20% to 40% In the cracking process, and simultaneously conveying the cracked H, N, C atoms to a tail pipe along with the carrier gas to be discharged out of the reaction chamber;

Raising the temperature of the reaction cavity to 800-820 ℃, raising the pressure of the reaction cavity to 400-440mbar, introducing NH ₃, TMGa and N ₂, periodically interrupting a Ga source to grow a GaN barrier layer with the thickness of D ₄ on the GaO layer, wherein in the growth process of the GaN barrier layer, the time for interrupting the TMGa and introducing the reaction cavity is 8s and 4s respectively;

wherein D ₃+D₄＝1.5(D₁+D₂);

the steps of feeding TMIn source, growing MQWs1 and growing MQWs2 are carried out periodically and sequentially, and the number of periods is 2-11.

2. The method for manufacturing the LED epitaxial wafer suitable for the small-space display screen, according to claim 1, is characterized in that at the temperature of 1000-1100 ℃, H ₂ with the concentration of 100-130L/min is introduced, the pressure of a reaction cavity is kept at 100-300mbar, and a sapphire substrate is processed for 5-10min.

3. The method for manufacturing the LED epitaxial wafer suitable for the small-pitch display screen according to claim 2, wherein the specific process of growing the low-temperature GaN buffer layer is as follows:

Cooling to 500-600 ℃, maintaining the pressure of the reaction cavity at 300-600mbar, introducing NH ₃ with the flow rate of 10000-20000sccm, TMGa with the flow rate of 50-100sccm and H ₂ with the flow rate of 100-130L/min, and growing a low-temperature GaN buffer layer with the thickness of 20-40nm on the sapphire substrate;

Raising the temperature to 1000-1100 ℃, maintaining the pressure of the reaction cavity at 300-600mbar, introducing NH ₃ with the flow rate of 30000-40000sccm and H ₂ with the flow rate of 100-130L/min, preserving heat for 300-500s, and corroding the low-temperature GaN buffer layer into an irregular island shape.

4. The method for manufacturing the LED epitaxial wafer suitable for the small-pitch display screen according to claim 1, wherein the specific process of growing the undoped GaN layer is as follows:

Raising the temperature to 1000-1200 ℃, keeping the pressure of the reaction cavity at 300-600mbar, introducing NH ₃ with the flow rate of 30000-40000sccm, TMGa with the flow rate of 200-400sccm and H ₂ with the flow rate of 100-130L/min, and continuously growing a 2-4 mu m undoped GaN layer.

5. The method for manufacturing the LED epitaxial wafer suitable for the small-pitch display screen according to claim 1, wherein the specific process of growing the Si-doped N-type GaN layer is as follows:

Maintaining the pressure of the reaction cavity at 300-600mbar, maintaining the temperature at 1000-1200 ℃, introducing NH ₃ with the flow rate of 30000-60000sccm, TMGa with the flow rate of 200-400sccm, H ₂ with the flow rate of 100-130L/min and SiH ₄ with the flow rate of 20-50sccm, and continuously growing an N-type GaN layer doped with Si with the doping concentration of 3-4 mu m, wherein the doping concentration of Si is 5E18-1E19atoms/cm ³.

6. The method for manufacturing the LED epitaxial wafer suitable for the small-space display screen according to claim 1, wherein the specific process of growing the AlGaN electron blocking layer is as follows:

and growing the AlGaN electron blocking layer under the conditions of the temperature of 900-950 ℃, the pressure of a reaction cavity of 200-400mbar, NH ₃ with the concentration of 50000-70000sccm, TMGa with the concentration of 30-60sccm, H ₂ with the concentration of 100-130L/min, TMAL with the concentration of 100-130sccm and Cp ₂ Mg with the concentration of 1000-1300sccm, wherein the thickness of the AlGaN layer is 40-60nm, and the doping concentration of Mg is 1E19-1E20atoms/cm ³.

7. The method for manufacturing the LED epitaxial wafer suitable for the small-pitch display screen according to claim 1, wherein the specific process of growing the Mg-doped P-type GaN layer is as follows:

Maintaining the pressure of the reaction cavity at 400-900mbar and the temperature at 950-1000 ℃, introducing NH ₃ with the flow rate of 50000-70000sccm, TMGa with the flow rate of 20-100sccm, H ₂ with the flow rate of 100-130L/min and Cp ₂ Mg with the flow rate of 1000-3000sccm, and continuously growing a 50-200nm P-type GaN layer doped with Mg, wherein the doping concentration of Mg is 1E19-1E20atoms/cm ³.

8. The method for manufacturing the LED epitaxial wafer suitable for the small-space display screen according to claim 1, wherein the specific process of cooling is as follows:

Cooling to 650-680 deg.C, maintaining the temperature for 20-30min, closing the heating system, closing the gas supply system, and cooling with furnace.