Light-emitting diode epitaxial wafer for improving reliability and preparation method thereof

Abstract

The present disclosure discloses a light-emitting diode epitaxial wafer for improving reliability and a preparation method thereof, belonging to the field of light-emitting diode fabrication. The p-type composite contact layer on the p-type GaN layer includes a first aluminum gallium nitride sublayer, a second aluminum gallium nitride sublayer, a third aluminum indium gallium nitride sublayer, a fourth aluminum indium gallium nitride sublayer, and a fifth indium gallium nitride sublayer that are sequentially stacked. The p-type composite contact layer with a relatively large thickness and several potential barrier changes avoids the occurrence of current breakdown. It can also make the carriers more evenly distributed in the P electrode region, effectively reduce the poor antistatic ability caused by uneven carrier distribution, and improve the reliability of the light-emitting diode light-emitting device. The doping concentrations of Mg in the first aluminum gallium nitride sublayer, the second aluminum gallium nitride sublayer, the third aluminum indium gallium nitride sublayer, the fourth aluminum indium gallium nitride sublayer, and the fifth indium gallium nitride sublayer increase in sequence, which may reduce the resistance, lower the working voltage, and reduce the probability of current breakdown, thereby improving the reliability of the light-emitting diode.

Description

Technical Field

[0001] The present disclosure relates to the field of light-emitting diode manufacturing, and particularly to a light-emitting diode epitaxial wafer for improving reliability and a method for preparing the same. Background Art

[0002] A light-emitting diode is a semiconductor electronic component that can emit light. As an efficient, environmentally friendly, and green new solid-state lighting source, it is being rapidly and widely applied, such as traffic signal lights, internal and external automotive lights, urban landscape lighting, mobile phone backlights, etc. Improving the light-emitting efficiency of chips is an ongoing goal for light-emitting diodes.

[0003] In the related art, the epitaxial wafer of a light-emitting diode generally includes a substrate and an n-type GaN layer, a multi-quantum well layer, a p-type GaN layer, and a p-type contact layer of gallium nitride material on the p-type GaN layer, which are sequentially grown on the substrate. In the related art, the multi-quantum well layer generally includes alternately stacked InGaN well layers and GaN barrier layers.

[0004] The thickness of the single-layer p-type contact layer of gallium nitride material is limited. After the p-type contact layer forms an ohmic contact with the electrode, problems such as current breakdown and uneven current distribution may occur in the p-type contact layer with limited thickness, affecting the use reliability of the light-emitting diode. Summary of the Invention

[0005] Embodiments of the present disclosure provide a light-emitting diode epitaxial wafer for improving reliability and a method for preparing the same, which can reduce the problems of current breakdown and uneven current distribution to improve the use reliability of the light-emitting diode. The technical solutions are as follows:

[0006] Embodiments of the present disclosure provide a light-emitting diode epitaxial wafer for improving reliability. The light-emitting diode epitaxial wafer for improving reliability includes an n-type GaN layer, a multi-quantum well layer, a p-type GaN layer, and a p-type composite contact layer that are sequentially stacked. The p-type composite contact layer includes a first aluminum gallium nitride sub-layer, a second aluminum gallium nitride sub-layer, a third aluminum indium gallium nitride sub-layer, a fourth aluminum indium gallium nitride sub-layer, and a fifth indium gallium nitride sub-layer that are sequentially stacked. The doping concentration of Mg in the first aluminum gallium nitride sub-layer, the second aluminum gallium nitride sub-layer, the third aluminum indium gallium nitride sub-layer, the fourth aluminum indium gallium nitride sub-layer, and the fifth indium gallium nitride sub-layer increases in sequence.

[0007] Optionally, the doping concentration of Mg in the second aluminum gallium nitride sub-layer is greater than 1×10 18 cm -3 and less than 1×10 19 cm -3 ; the doping concentration of Mg in the third aluminum indium gallium nitride sub-layer is greater than 1×10 19 cm -3 and less than 1×10 20 cm -3, the doping concentration of Mg in the fourth aluminum indium gallium nitride sub-layer is greater than 1×10 20 cm -3 and less than 1×10 21 cm -3 , the doping concentration of Mg in the fifth indium gallium nitride sub-layer is greater than 1×10 21 cm -3 and less than 1×10 22 cm -3 .

[0008] Optionally, the first aluminum gallium nitride sub-layer is an intrinsic aluminum gallium nitride material, the thickness of the second aluminum gallium nitride sub-layer is 1 nm to 20 nm, the thickness of the third aluminum indium gallium nitride sub-layer is 1 nm to 100 nm, the thickness of the fourth aluminum indium gallium nitride sub-layer is 1 nm to 100 nm, and the thickness of the fifth indium gallium nitride sub-layer is 1 nm to 100 nm.

[0009] Optionally, the Al component of the first aluminum gallium nitride sub-layer is greater than the Al component of the second aluminum gallium nitride sub-layer, the Al component in the third aluminum indium gallium nitride sub-layer is greater than the Al component in the fourth aluminum indium gallium nitride sub-layer, and the In component in the third aluminum indium gallium nitride sub-layer is less than the In component in the fourth aluminum indium gallium nitride sub-layer.

[0010] The embodiments of the present disclosure provide a method for preparing a light-emitting diode epitaxial wafer with improved reliability, and the preparation method includes:

[0011] Providing a substrate;

[0012] Growing an n-type GaN layer, a multi-quantum well layer, a p-type GaN layer and a p-type composite contact layer on the substrate in sequence, the p-type composite contact layer includes a first aluminum gallium nitride sub-layer, a second aluminum gallium nitride sub-layer, a third aluminum indium gallium nitride sub-layer, a fourth aluminum indium gallium nitride sub-layer and a fifth indium gallium nitride sub-layer stacked in sequence, and the doping concentration of Mg in the first aluminum gallium nitride sub-layer, the second aluminum gallium nitride sub-layer, the third aluminum indium gallium nitride sub-layer, the fourth aluminum indium gallium nitride sub-layer and the fifth indium gallium nitride sub-layer increases in sequence.

[0013] Optionally, the growth pressures of the first aluminum gallium nitride sub-layer, the second aluminum gallium nitride sub-layer, the third aluminum indium gallium nitride sub-layer, the fourth aluminum indium gallium nitride sub-layer and the fifth indium gallium nitride sub-layer are 50~200 torr, 100~250 torr, 200~350 torr, 300~450 torr and 400~600 torr respectively.

[0014] Optionally, the growth pressures of the first aluminum gallium nitride sub-layer, the second aluminum gallium nitride sub-layer, the third aluminum indium gallium nitride sub-layer, the fourth aluminum indium gallium nitride sub-layer and the fifth indium gallium nitride sub-layer increase in sequence.

[0015] Optionally, the growth temperatures of the first aluminum gallium nitride sub-layer, the second aluminum gallium nitride sub-layer, the third aluminum indium gallium nitride sub-layer, the fourth aluminum indium gallium nitride sub-layer, and the fifth indium gallium nitride sub-layer are 950 - 1000 degrees Celsius, 900 - 950 degrees Celsius, 850 - 900 degrees Celsius, 800 - 850 degrees Celsius, and 700 - 800 degrees Celsius, respectively.

[0016] Optionally, the growth temperatures of the first aluminum gallium nitride sub-layer, the second aluminum gallium nitride sub-layer, the third aluminum indium gallium nitride sub-layer, the fourth aluminum indium gallium nitride sub-layer, and the fifth indium gallium nitride sub-layer decrease in sequence.

[0017] Optionally, the growth temperatures of the first aluminum gallium nitride sub-layer, the second aluminum gallium nitride sub-layer, the third aluminum indium gallium nitride sub-layer, the fourth aluminum indium gallium nitride sub-layer, and the fifth indium gallium nitride sub-layer decrease by 50 - 80 degrees Celsius in sequence.

[0018] The beneficial effects brought by the technical solutions provided in the embodiments of the present disclosure are as follows:

[0019] The p-type composite contact layer on the p-type GaN layer includes a first aluminum gallium nitride sub-layer, a second aluminum gallium nitride sub-layer, a third aluminum indium gallium nitride sub-layer, a fourth aluminum indium gallium nitride sub-layer, and a fifth indium gallium nitride sub-layer stacked in sequence. The barrier is higher for the sub-layer with a higher aluminum content closer to the p-type GaN layer, and the barrier is lower for the sub-layer with a lower aluminum content and a higher indium content farther from the p-type GaN layer. The barrier is higher for the part of the p-type composite contact layer closer to the p-type GaN layer. A p-type composite contact layer with a larger thickness and several barrier changes can effectively prevent the current from breaking down. When the p-type composite contact layer is working, carriers flow from the low-barrier fifth indium gallium nitride sub-layer to the high-barrier first aluminum gallium nitride sub-layer ultimately. The carriers can be more easily spread out, thereby reducing the working voltage of the diode and reducing energy consumption. It can also make the carriers more evenly distributed in the P electrode region, effectively reducing the poor antistatic ability caused by uneven carrier distribution and improving the reliability of the light-emitting diode light-emitting device. The doping concentrations of Mg in the first aluminum gallium nitride sub-layer, the second aluminum gallium nitride sub-layer, the third aluminum indium gallium nitride sub-layer, the fourth aluminum indium gallium nitride sub-layer, and the fifth indium gallium nitride sub-layer increase in sequence, which can reduce the resistivity of the p-type composite contact layer in sequence, improve the ohmic contact characteristics between the p-type composite contact layer and the electrode, and can also play a certain role in reducing resistance, reducing the working voltage, and reducing the probability of current breakdown, improving the reliability of the light-emitting diode. Description of the Drawings

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present disclosure. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0021] Figure 1 It is a schematic structural diagram of a light-emitting diode epitaxial wafer for improving reliability provided by an embodiment of the present disclosure;

[0022] Figure 2 It is a schematic structural diagram of another light-emitting diode epitaxial wafer for improving reliability provided by an embodiment of the present disclosure;

[0023] Figure 3 It is a flowchart of a method for manufacturing a light-emitting diode epitaxial wafer for improving reliability provided by an embodiment of the present disclosure;

[0024] Figure 4 It is a flowchart of another method for manufacturing a light-emitting diode epitaxial wafer for improving reliability provided by an embodiment of the present disclosure. Detailed implementation manners

[0025] To make the objectives, technical solutions, and advantages of the present disclosure clearer, the following will further describe the embodiments of the present disclosure in detail with reference to the accompanying drawings.

[0026] Figure 1 It is a schematic structural diagram of a light-emitting diode epitaxial wafer for improving reliability provided by an embodiment of the present disclosure. Referring to Figure 1 it can be seen that the embodiment of the present disclosure provides a light-emitting diode epitaxial wafer for improving reliability. The light-emitting diode epitaxial wafer for improving reliability includes an n-type GaN layer 2, a multi-quantum well layer 3, a p-type GaN layer 4, and a p-type composite contact layer 5 stacked in sequence. The p-type composite contact layer 5 includes a first aluminum gallium nitride sub-layer 51, a second aluminum gallium nitride sub-layer 52, a third aluminum indium gallium nitride sub-layer 53, a fourth aluminum indium gallium nitride sub-layer 54, and a fifth indium gallium nitride sub-layer 55 stacked in sequence. The doping concentration of Mg in the first aluminum gallium nitride sub-layer 51, the second aluminum gallium nitride sub-layer 52, the third aluminum indium gallium nitride sub-layer 53, the fourth aluminum indium gallium nitride sub-layer 54, and the fifth indium gallium nitride sub-layer 55 increases in sequence.

[0027] The p-type composite contact layer 5 on the p-type GaN layer 4 includes a first aluminum gallium nitride sub-layer 51, a second aluminum gallium nitride sub-layer 52, a third aluminum indium gallium nitride sub-layer 53, a fourth aluminum indium gallium nitride sub-layer 54, and a fifth indium gallium nitride sub-layer 55 stacked in sequence. The barrier is higher for the sub-layers closer to the p-type GaN layer 4 with a higher aluminum content, and lower for the sub-layers farther from the p-type GaN layer 4 with a lower aluminum content and a higher indium content. The part of the p-type composite contact layer 5 closer to the p-type GaN layer 4 has a higher barrier. The p-type composite contact layer 5 with a larger thickness and several barrier changes can effectively avoid current breakdown. When the p-type composite contact layer 5 is working, carriers flow from the low-barrier fifth indium gallium nitride sub-layer 55 to the high-barrier first aluminum gallium nitride sub-layer 51 eventually, and the carriers can spread more easily, thereby reducing the working voltage of the diode and reducing energy consumption. It can also make the carriers more evenly distributed in the P electrode region, effectively reducing the poor antistatic ability caused by uneven carrier distribution and improving the reliability of the light-emitting diode light-emitting device. The doping concentrations of Mg in the first aluminum gallium nitride sub-layer 51, the second aluminum gallium nitride sub-layer 52, the third aluminum indium gallium nitride sub-layer 53, the fourth aluminum indium gallium nitride sub-layer 54, and the fifth indium gallium nitride sub-layer 55 increase in sequence, which can reduce the resistivity of the p-type composite contact layer 5 in sequence, improve the ohmic contact characteristics between the p-type composite contact layer 5 and the electrode, and can also play a role in reducing resistance, reducing working voltage and reducing the probability of current breakdown to improve the reliability of the light-emitting diode.

[0028] It should be noted that the p-type composite contact layer 5 needs to be connected to the p electrode, and the n-type GaN layer 2 needs to be connected to the n electrode, and the current is transmitted between the n electrode and the p electrode.

[0029] Optionally, the doping concentration of Mg in the second aluminum gallium nitride sub-layer 52 is greater than 1×10 18 cm -3 and less than 1×10 19 cm -3 , the doping concentration of Mg in the third aluminum indium gallium nitride sub-layer 53 is greater than 1×10 19 cm -3 and less than 1×10 20 cm -3 , the doping concentration of Mg in the fourth aluminum indium gallium nitride sub-layer 54 is greater than 1×10 20 cm -3 and less than 1×10 21 cm -3 , the doping concentration of Mg in the fifth indium gallium nitride sub-layer 55 is greater than 1×10 21 cm -3 and less than 1×10 22 cm -3 .

[0030] In the p-type composite contact layer 5, the first aluminum gallium nitride sub-layer 51 is an intrinsic material, that is, no impurity doping is performed in the first aluminum gallium nitride sub-layer 51, which can reduce the lattice mismatch between the first aluminum gallium nitride sub-layer 51 and the p-type GaN layer 4, improve the quality of the obtained first aluminum gallium nitride sub-layer 51, and thus improve the quality of the finally obtained p-type composite contact layer 5. Based on the first aluminum gallium nitride sub-layer 51, when the doping concentrations of Mg in the second aluminum gallium nitride sub-layer 52, the third aluminum indium gallium nitride sub-layer 53, the fourth aluminum indium gallium nitride sub-layer 54, and the fifth indium gallium nitride sub-layer 55 are respectively within the above ranges, it can ensure that the change in resistivity in the p-type composite contact layer 5 is relatively reasonable, ensure the uniform transfer of current, and is beneficial to reducing the resistance.

[0031] Exemplarily, the thickness of the p-type composite contact layer 5 can be 20 nm to 200 nm.

[0032] When the thickness of the p-type composite contact layer 5 is within the above range, the obtained p-type composite contact layer 5 has good quality and can also effectively reduce the possibility of current breakdown.

[0033] Optionally, the first aluminum gallium nitride sub-layer 51 is an intrinsic aluminum gallium nitride material, the thickness of the second aluminum gallium nitride sub-layer 52 is 1 nm to 20 nm, the thickness of the third aluminum indium gallium nitride sub-layer 53 is 1 nm to 100 nm, the thickness of the fourth aluminum indium gallium nitride sub-layer 54 is 1 nm to 100 nm, and the thickness of the fifth indium gallium nitride sub-layer 55 is 1 nm to 100 nm.

[0034] In the p-type composite contact layer 5, when the thicknesses of the sub-layers are within the above ranges, it can ensure the quality of the obtained p-type composite contact layer 5 while effectively controlling the manufacturing cost of the obtained p-type composite contact layer 5.

[0035] Exemplarily, the thicknesses of the first aluminum gallium nitride sub-layer 51, the second aluminum gallium nitride sub-layer 52, the third aluminum indium gallium nitride sub-layer 53, the fourth aluminum indium gallium nitride sub-layer 54, and the fifth indium gallium nitride sub-layer 55 can be equal. It can ensure good quality of the p-type composite contact layer 5 while effectively controlling the manufacturing cost of the p-type composite contact layer 5.

[0036] In an implementation provided by the present disclosure, the thicknesses of the first aluminum gallium nitride sub-layer 51, the second aluminum gallium nitride sub-layer 52, the third aluminum indium gallium nitride sub-layer 53, the fourth aluminum indium gallium nitride sub-layer 54, and the fifth indium gallium nitride sub-layer 55 can all be 2 to 10 nm. It can ensure the quality of the p-type composite contact layer 5 while effectively reducing the manufacturing cost of the p-type composite contact layer 5.

[0037] Optionally, the Al component of the first aluminum gallium nitride sub-layer 51 is greater than that of the second aluminum gallium nitride sub-layer 52, the Al component in the third aluminum indium gallium nitride sub-layer 53 is greater than that in the fourth aluminum indium gallium nitride sub-layer 54, and the In component in the third aluminum indium gallium nitride sub-layer 53 is less than that in the fourth aluminum indium gallium nitride sub-layer 54.

[0038] By respectively adopting the above changes in the Al components of the first aluminum gallium nitride sub-layer 51 and the second aluminum gallium nitride sub-layer 52, and the Al and In components in the third aluminum indium gallium nitride sub-layer 53 and the fourth aluminum indium gallium nitride sub-layer 54, the effective expansion of the resistivity and current in the p-type composite contact layer 5 can be ensured, and the current uniformity of the p-type composite contact layer 5 can be improved, so as to improve the reliability of the finally obtained light-emitting diode.

[0039] Exemplarily, the Al components of the first aluminum gallium nitride sub-layer 51 and the second aluminum gallium nitride sub-layer 52 can be 30wt% - 50wt% respectively, the Al components in the third aluminum indium gallium nitride sub-layer 53 and the fourth aluminum indium gallium nitride sub-layer 54 can be 20wt% - 30wt% respectively, and the In components in the third aluminum indium gallium nitride sub-layer 53 and the fourth aluminum indium gallium nitride sub-layer 54 can be 10wt% - 20wt% respectively.

[0040] When the component ranges of the sub-layers in the p-type composite contact layer 5 are within the above ranges, the obtained p-type composite contact layer 5 has better quality, can ensure the uniform transfer of current in the p-type composite contact layer 5, and the uniformity of the resistance in the p-type composite contact layer 5 is also relatively high.

[0041] Figure 2 It is a schematic structural diagram of another light-emitting diode epitaxial wafer with improved reliability provided by an embodiment of the present disclosure. Refer to Figure 2 It can be known that the embodiment of the present disclosure provides a light-emitting diode epitaxial wafer with improved reliability. The light-emitting diode epitaxial wafer with improved reliability includes a buffer layer 6, an undoped GaN layer 7, an n-type GaN layer 2, a multi-quantum well layer 3, an AlGaN electron blocking layer 8, a p-type GaN layer 4, and a p-type composite contact layer 5 stacked in sequence. The p-type composite contact layer 5 includes a first aluminum gallium nitride sub-layer 51, a second aluminum gallium nitride sub-layer 52, a third aluminum indium gallium nitride sub-layer 53, a fourth aluminum indium gallium nitride sub-layer 54, and a fifth indium gallium nitride sub-layer 55 stacked in sequence. The doping concentrations of Mg in the first aluminum gallium nitride sub-layer 51, the second aluminum gallium nitride sub-layer 52, the third aluminum indium gallium nitride sub-layer 53, the fourth aluminum indium gallium nitride sub-layer 54, and the fifth indium gallium nitride sub-layer 55 increase in sequence.

[0042] It should be noted that Figure 2 The p-type composite contact layer 5 shown in Figure 1 has the same structure as the p-type composite contact layer 5 shown in

[0043] Optionally, the substrate 1 can be a sapphire substrate 1, which is easy to fabricate and obtain.

[0044] Exemplarily, the buffer layer 6 can be an AlN buffer layer 6, which can ensure the crystal quality of the epitaxial thin film grown on the low-temperature buffer layer 6.

[0045] Optionally, the thickness of the buffer layer 6 can be 10 - 30 nm, which can reduce the lattice mismatch between the n-type GaN layer 2 and the substrate 1 and ensure the growth quality of the epitaxial layer.

[0046] Exemplarily, the thickness of the undoped GaN layer 7 can be 1 - 3.5 µm, and the quality of the obtained light-emitting diode epitaxial wafer is better at this time.

[0047] In an implementation provided by the present disclosure, the thickness of the undoped GaN layer 7 can also be 1 µm, and the present disclosure does not limit this.

[0048] Optionally, the doping element of the n-type GaN layer 2 can be Si, and the doping concentration of the Si element can be 1×10 18 ~ 1×10 19 cm -3 . The overall quality of the n-type GaN layer 2 is better.

[0049] Exemplarily, the thickness of the n-type GaN layer 2 can be 2 - 3 µm, and the overall quality of the obtained n-type GaN layer 2 is better.

[0050] In an implementation provided by the present disclosure, the thickness of the n-type GaN layer 2 can be 2 µm, and the present disclosure does not limit this.

[0051] Optionally, the multiple quantum well layer 3 includes alternately stacked InGaN well layers and GaN barrier layers, which can ensure the stable light emission of the light-emitting diode.

[0052] Optionally, the Al component in the AlGaN electron blocking layer 8 can be 0.15 - 0.25, and the effect of blocking electrons is better.

[0053] Optionally, the p-type GaN layer 4 can be doped with Mg, and the thickness of the p-type GaN layer 4 can be the same as that of the structure shown in Figure 1 , which will not be elaborated here.

[0054] It should be noted that Figure 2 compared with the epitaxial wafer structure shown in Figure 1 , a buffer layer 6 and an undoped GaN layer 7 for alleviating lattice mismatch are added between the buffer layer 6 and the n-type GaN layer 2. The quality and light emission efficiency of the obtained epitaxial wafer will be better.

[0055] Figure 3It is a flowchart of a method for preparing a light-emitting diode epitaxial wafer with improved reliability provided by an embodiment of the present disclosure. Refer to Figure 3 It can be seen that an embodiment of the present disclosure provides a method for preparing a light-emitting diode epitaxial wafer with improved reliability. The preparation method includes:

[0056] S101: Provide a substrate.

[0057] S102: Grow an n-type GaN layer, a multi-quantum well layer, a p-type GaN layer, and a p-type composite contact layer on the substrate in sequence. The p-type composite contact layer includes a first aluminum gallium nitride sub-layer, a second aluminum gallium nitride sub-layer, a third aluminum indium gallium nitride sub-layer, a fourth aluminum indium gallium nitride sub-layer, and a fifth indium gallium nitride sub-layer that are stacked in sequence. The doping concentration of Mg in the first aluminum gallium nitride sub-layer, the second aluminum gallium nitride sub-layer, the third aluminum indium gallium nitride sub-layer, the fourth aluminum indium gallium nitride sub-layer, and the fifth indium gallium nitride sub-layer increases in sequence.

[0058] Figure 3 For the technical effects of the method for preparing the light-emitting diode epitaxial wafer shown in Figure 1 For the corresponding technical effects of the light-emitting diode epitaxial wafer shown in Figure 1 .

[0059] Optionally, in step S102, when growing the p-type composite contact layer, the growth pressures of the first aluminum gallium nitride sub-layer, the second aluminum gallium nitride sub-layer, the third aluminum indium gallium nitride sub-layer, the fourth aluminum indium gallium nitride sub-layer, and the fifth indium gallium nitride sub-layer are 50-200 torr, 100-250 torr, 200-350 torr, 300-450 torr, and 400-600 torr respectively.

[0060] When the growth pressures of the first aluminum gallium nitride sub-layer, the second aluminum gallium nitride sub-layer, the third aluminum indium gallium nitride sub-layer, the fourth aluminum indium gallium nitride sub-layer, and the fifth indium gallium nitride sub-layer are within the above ranges respectively, and the growth pressures of each sub-layer increase gradually in sequence, it can ensure that in the sub-layer with more Al elements close to the p-type GaN layer, the pre-reaction of Al elements can be reduced at low pressure, ensuring the stable reaction between Al elements, nitrogen elements, and gallium elements, improving the uniformity of the finally obtained first aluminum gallium nitride sub-layer, and improving the crystal quality of the first aluminum gallium nitride sub-layer. In the sub-layers far from the p-type GaN layer, since there is less or no Al element, a higher pressure can be used to promote the rapid growth of the sub-layers, which can improve the quality of the obtained p-type composite contact layer and effectively shorten the preparation cycle of the epitaxial wafer.

[0061] Optionally, the growth pressures of the first aluminum gallium nitride sub-layer, the second aluminum gallium nitride sub-layer, the third aluminum indium gallium nitride sub-layer, the fourth aluminum indium gallium nitride sub-layer, and the fifth indium gallium nitride sub-layer increase in sequence. This can improve the quality of the obtained p-type composite contact layer while effectively shortening the preparation cycle of the epitaxial wafer.

[0062] Optionally, the growth temperatures of the first aluminum gallium nitride sub-layer, the second aluminum gallium nitride sub-layer, the third aluminum indium gallium nitride sub-layer, the fourth aluminum indium gallium nitride sub-layer, and the fifth indium gallium nitride sub-layer are 950 - 1000 °C, 900 - 950 °C, 850 - 900 °C, 800 - 850 °C, and 700 - 800 °C respectively.

[0063] The growth temperatures of each sub-layer decrease successively. This can ensure that in the sub-layers with more Al elements closer to the p-type GaN layer, the high temperature improves the crystal quality of the first aluminum gallium nitride sub-layer and the second aluminum gallium nitride sub-layer. In the sub-layers far from the p-type GaN layer, the high Mg doping concentration and high In composition require lower growth temperatures. The low temperature is beneficial to reducing the activation energy of Mg to effectively increase the Mg doping concentration, the low temperature is beneficial to reducing In precipitation to increase the In composition, and the high In composition can reduce the activation energy of Mg to effectively increase the Mg doping concentration. This can improve the effective doping of Mg in the obtained p-type composite contact layer and improve the crystal quality of the obtained p-type composite contact layer.

[0064] Optionally, the growth temperatures of the first aluminum gallium nitride sub-layer, the second aluminum gallium nitride sub-layer, the third aluminum indium gallium nitride sub-layer, the fourth aluminum indium gallium nitride sub-layer, and the fifth indium gallium nitride sub-layer decrease in sequence. This can improve the effective doping of Mg in the obtained p-type composite contact layer and improve the crystal quality of the obtained p-type composite contact layer.

[0065] Exemplarily, the growth temperatures of the first aluminum gallium nitride sub-layer, the second aluminum gallium nitride sub-layer, the third aluminum indium gallium nitride sub-layer, the fourth aluminum indium gallium nitride sub-layer, and the fifth indium gallium nitride sub-layer decrease by 50 - 80 °C in sequence. This can ensure the crystal quality of the obtained p-type composite contact layer and facilitate the preparation of the epitaxial wafer at the same time.

[0066] Figure 4 It is a flowchart of another method for preparing a light-emitting diode epitaxial wafer to improve reliability provided by an embodiment of the present disclosure. Referring to Figure 4 it can be seen that the method for preparing the light-emitting diode epitaxial wafer includes:

[0067] S201: Provide a substrate.

[0068] Among them, the substrate can be a sapphire substrate, which is easy to implement and fabricate.

[0069] Optionally, step S201 may further include: treating the surface of the substrate for growing the epitaxial layer for 5 - 6 min in a hydrogen atmosphere.

[0070] Exemplarily, when processing the surface of the substrate for growing the epitaxial layer, the temperature of the reaction chamber can be 1000 - 1100 °C, and the pressure of the reaction chamber can be 200 - 500 torr.

[0071] S202: Grow a buffer layer on the substrate.

[0072] The buffer layer can be an AlN buffer layer. The AlN layer can be obtained by magnetron sputtering.

[0073] Exemplarily, the deposition temperature of the AlN layer can be 400 - 800 °C, the sputtering power can be 3000 - 5000 W, and the pressure can be 2 - 20 mtorr. The obtained AlN layer has good quality.

[0074] S203: Grow an undoped GaN layer on the buffer layer.

[0075] The thickness of the undoped GaN layer can be 0.5 - 3 μm.

[0076] Exemplarily, the growth temperature of the undoped GaN layer can be 1000 - 1100 °C, and the growth pressure is controlled at 100 - 300 torr. The obtained undoped GaN layer has good quality.

[0077] S204: Grow an n-type GaN layer on the undoped GaN layer.

[0078] Optionally, the n-type GaN layer can be an n-type GaN layer, the growth temperature of the n-type GaN layer can be 1000 - 1100 °C, and the growth pressure of the n-type GaN layer can be 100 - 300 Torr.

[0079] Optionally, the thickness of the n-type GaN layer can be 0.5 - 3 μm.

[0080] S205: Grow a multi-quantum well layer on the n-type GaN layer.

[0081] In step S205, the multi-quantum well layer includes alternately stacked InGaN well layers and GaN barrier layers, and the alternately stacked InGaN well layers and GaN barrier layers can be obtained by alternately introducing different reaction materials into the reaction chamber.

[0082] S206: Grow an AlGaN electron blocking layer on the multi-quantum well layer.

[0083] The growth temperature of the AlGaN electron blocking layer can be 800 - 1000 °C, and the growth pressure of the AlGaN electron blocking layer can be 100 - 300 Torr. The AlGaN electron blocking layer grown under these conditions has good quality, which is beneficial to improving the light emission efficiency of the light-emitting diode.

[0084] S207: Grow a p-type GaN layer on the AlGaN electron blocking layer.

[0085] Optionally, the growth pressure of the p-type GaN layer can be 200-600 Torr, and the growth temperature of the p-type GaN layer can be 800-1000 °C.

[0086] S208: Grow a p-type contact layer on the p-type GaN layer.

[0087] Step S208 can refer to Figure 3 the step S102 shown in

[0088] It should be noted that Figure 4 the method for preparing a light-emitting diode epitaxial wafer shown in Figure 3 provides a more detailed growth method of the light-emitting diode epitaxial wafer compared to the method for preparing a light-emitting diode shown in

[0089] The structure of the light-emitting diode epitaxial wafer after performing step S208 can be seen in Figure 2 .

[0090] It should be noted that in the embodiments of the present disclosure, a Veeco K465i or C4 or RBMOCVD (Metal Organic Chemical Vapor Deposition) device is used to implement the growth method of the light-emitting diode. High-purity H2 (hydrogen) or high-purity N2 (nitrogen) or a mixed gas of high-purity H2 and high-purity N2 is used as the carrier gas, high-purity NH3 is used as the N source, trimethylgallium (TMGa) and triethylgallium (TEGa) are used as the gallium sources, trimethylindium (TMIn) is used as the indium source, silane (SiH4) is used as the N-type dopant, trimethylaluminum (TMAl) is used as the aluminum source, and bis(cyclopentadienyl)magnesium (CP2Mg) is used as the P-type dopant.

[0091] The above are only the preferred embodiments of the present disclosure, and are not intended to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A light-emitting diode epitaxial wafer, characterized in that, The light-emitting diode epitaxial wafer includes an n-type GaN layer, a multi-quantum well layer, a p-type GaN layer, and a p-type composite contact layer stacked in sequence. The p-type composite contact layer includes a first aluminum gallium nitride sub-layer, a second aluminum gallium nitride sub-layer, a third aluminum indium gallium nitride sub-layer, a fourth aluminum indium gallium nitride sub-layer, and a fifth indium gallium nitride sub-layer stacked in sequence. The doping concentration of Mg in the first aluminum gallium nitride sub-layer, the second aluminum gallium nitride sub-layer, the third aluminum indium gallium nitride sub-layer, the fourth aluminum indium gallium nitride sub-layer, and the fifth indium gallium nitride sub-layer increases in sequence.

2. The light-emitting diode epitaxial wafer according to claim 1, wherein The first aluminum gallium nitride sub-layer is an intrinsic aluminum gallium nitride material, and the doping concentration of Mg in the second aluminum gallium nitride sub-layer is greater than 1×10 18 cm -3 and less than 1×10 19 cm -3 , the doping concentration of Mg in the third aluminum indium gallium nitride sub-layer is greater than 1×10 19 cm -3 and less than 1×10 20 cm -3 , the doping concentration of Mg in the fourth aluminum indium gallium nitride sub-layer is greater than 1×10 20 cm -3 and less than 1×10 21 cm -3 , the doping concentration of Mg in the fifth indium gallium nitride sub-layer is greater than 1×10 21 cm -3 and less than 1×10 22 cm -3 .

3. The light-emitting diode epitaxial wafer according to claim 1, wherein The first aluminum gallium nitride sub-layer is an intrinsic aluminum gallium nitride material. The thickness of the second aluminum gallium nitride sub-layer is 1 nm to 20 nm. The thickness of the third aluminum indium gallium nitride sub-layer is 1 nm to 100 nm. The thickness of the fourth aluminum indium gallium nitride sub-layer is 1 nm to 100 nm. The thickness of the fifth indium gallium nitride sub-layer is 1 nm to 100 nm.

4. The light-emitting diode epitaxial wafer according to any one of claims 1 to 3, characterized in that, The Al component of the first aluminum gallium nitride sub-layer is greater than the Al component of the second aluminum gallium nitride sub-layer. The Al component in the third aluminum indium gallium nitride sub-layer is greater than the Al component in the fourth aluminum indium gallium nitride sub-layer. The In component in the third aluminum indium gallium nitride sub-layer is less than the In component in the fourth aluminum indium gallium nitride sub-layer.

5. A method for preparing a light-emitting diode epitaxial wafer, characterized in that, The preparation method includes: providing a substrate; successively growing an n-type GaN layer, a multi-quantum well layer, a p-type GaN layer, and a p-type composite contact layer on the substrate. The p-type composite contact layer includes a first aluminum gallium nitride sub-layer, a second aluminum gallium nitride sub-layer, a third aluminum indium gallium nitride sub-layer, a fourth aluminum indium gallium nitride sub-layer, and a fifth indium gallium nitride sub-layer stacked in sequence. The doping concentration of Mg in the first aluminum gallium nitride sub-layer, the second aluminum gallium nitride sub-layer, the third aluminum indium gallium nitride sub-layer, the fourth aluminum indium gallium nitride sub-layer, and the fifth indium gallium nitride sub-layer increases in sequence.

6. The preparation method according to claim 5, characterized in that, The growth pressures of the first aluminum gallium nitride sub-layer, the second aluminum gallium nitride sub-layer, the third aluminum indium gallium nitride sub-layer, the fourth aluminum indium gallium nitride sub-layer, and the fifth indium gallium nitride sub-layer are 50 to 200 torr, 100 to 250 torr, 200 to 350 torr, 300 to 450 torr, and 400 to 600 torr respectively.

7. The preparation method according to claim 5, characterized in that, The growth pressures of the first aluminum gallium nitride sub-layer, the second aluminum gallium nitride sub-layer, the third aluminum indium gallium nitride sub-layer, the fourth aluminum indium gallium nitride sub-layer, and the fifth indium gallium nitride sub-layer increase in sequence.

8. The preparation method according to claim 5, wherein The growth temperatures of the first aluminum gallium nitride sub-layer, the second aluminum gallium nitride sub-layer, the third aluminum indium gallium nitride sub-layer, the fourth aluminum indium gallium nitride sub-layer, and the fifth indium gallium nitride sub-layer are 950 to 1000 degrees Celsius, 900 to 950 degrees Celsius, 850 to 900 degrees Celsius, 800 to 850 degrees Celsius, and 700 to 800 degrees Celsius respectively.

9. The preparation method according to claim 8, characterized in that, The growth temperatures of the first aluminum gallium nitride sub-layer, the second aluminum gallium nitride sub-layer, the third aluminum indium gallium nitride sub-layer, the fourth aluminum indium gallium nitride sub-layer, and the fifth indium gallium nitride sub-layer decrease in sequence.

10. The preparation method according to claim 9, characterized in that, The growth temperatures of the first aluminum gallium nitride sub-layer, the second aluminum gallium nitride sub-layer, the third aluminum indium gallium nitride sub-layer, the fourth aluminum indium gallium nitride sub-layer, and the fifth indium gallium nitride sub-layer decrease by 50 to 80 degrees Celsius in sequence.

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