Epitaxial wafer of light-emitting diode and preparation method thereof

Abstract

The present invention relates to the technical field of semiconductor materials and discloses an epitaxial wafer for a light-emitting diode and a method for preparing the same. The epitaxial wafer comprises a substrate, a buffer layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well layer, and a P-type combination layer sequentially stacked on the substrate; the P-type combination layer comprises an AlN / InN / P-type AlGaN superlattice layer and an AlGaN / P-type InGaN / P-type GaN superlattice layer. Implementation of the present invention can increase the activated Mg concentration, improve the hole concentration and hole injection efficiency, reduce the electron overflow effect, increase the electron-hole radiative recombination efficiency, and enhance the luminous efficiency and antistatic performance of the light-emitting diode.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor materials, and in particular to an epitaxial wafer of a light emitting diode and a preparation method thereof. Background Art

[0002] Due to its advantages of low heat generation efficiency, radiation resistance, high breakdown voltage, large electron saturation drift velocity, and small dielectric constant, GaN materials have been widely used in high-frequency, high-temperature, and high-voltage electronic devices, light-emitting diodes (LEDs), and semiconductor lasers (LDs), becoming a current research hotspot. Currently, GaN-based blue-green-violet LEDs are often grown on sapphire, silicon carbide, and silicon substrates using heteroepitaxial methods. The ohmic contact characteristics of LEDs have a significant impact on the luminous efficiency and operating voltage of LEDs. Due to the large work function of p-GaN materials (7.5 eV), there is no suitable metal to form an excellent ohmic contact. It is difficult to increase the hole concentration of Mg-doped p-GaN materials, making it difficult to form a p-type ohmic contact.

[0003] Nowadays, the commonly used solution structure for LEDs is a highly Mg-doped InGaN structure and a thicker P-type GaN layer. When the light emitted from the active layer passes through the P-type GaN layer, it will be absorbed and partially reflected by the P-type GaN layer, which will affect the luminous efficiency of the light-emitting diode. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an epitaxial wafer of a light-emitting diode and a preparation method thereof, thereby increasing the activated Mg concentration, improving the hole concentration and hole injection efficiency, reducing the electron overflow effect, improving the efficiency of electron and hole radiation recombination, and improving the luminous efficiency of the light-emitting diode.

[0005] In order to solve the above technical problems, the first aspect of the present invention provides an epitaxial wafer of a light-emitting diode, characterized in that it includes a substrate, a buffer layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well layer and a P-type combination layer stacked in sequence on the substrate;

[0006] The P-type combination layer includes an AlN / InN / P-type AlGaN superlattice layer and an AlGaN / P-type InGaN / P-type GaN superlattice layer.

[0007] As an improvement to the above solution, the AlN / InN / P-type AlGaN superlattice layer is a superlattice structure formed by alternating AlN layers, InN layers, and P-type AlGaN layers from bottom to top, with the alternating period number being 3 to 8;

[0008] The AlGaN / P-type InGaN / P-type GaN superlattice layer is a superlattice structure formed by alternately stacking AlGaN layers, P-type InGaN layers and P-type GaN layers from bottom to top, with the number of alternating periods being 5 to 20.

[0009] As an improvement to the above solution, the doping element in the P-type AlGaN layer is Mg, and the doping concentration of Mg is 1×10 18 atoms / cm 3 ~1×10 19 atoms / cm 3 ; The Al component is 0.01~0.1.

[0010] As an improvement to the above solution, the doping concentration of the P-type AlGaN layer decreases as the number of cycles increases.

[0011] As an improvement to the above solution, the Al composition in the AlGaN layer is 0.01 to 0.1;

[0012] In the P-type InGaN layer, the In component is 0.01-0.1; the doping element is Mg, and the doping concentration of Mg is 1×10 19 atoms / cm 3 ~1×10 21 atoms / cm 3 ;

[0013] The doping element in the P-type GaN layer is Mg, and the doping concentration of Mg is 1×10 19 atoms / cm 3 ~1×10 21 atoms / cm 3 .

[0014] As an improvement to the above solution, the Al component in the AlGaN layer increases with the increase of the number of cycles;

[0015] The doping concentration of the P-type InGaN layer increases with the increase of the period number; and the In component decreases with the increase of the period number.

[0016] The doping concentration of the P-type GaN layer increases with the increase of the number of cycles.

[0017] As an improvement to the above solution, the thickness of the AlN layer is 1 nm to 10 nm;

[0018] The thickness of the InN layer is 1 nm to 10 nm;

[0019] The thickness of the P-type AlGaN layer is 5nm to 10nm.

[0020] As an improvement to the above solution, the thickness of the AlGaN layer is 5nm to 10nm;

[0021] The thickness of the P-type InGaN layer is 1 nm to 10 nm;

[0022] The thickness of the P-type GaN layer is 5 nm to 10 nm.

[0023] As an improvement of the above solution, the growth temperature of the AlN / InN / P-type AlGaN superlattice layer is 800° C. to 900° C., and the growth pressure is 50 torr to 500 torr;

[0024] The growth temperature of the AlGaN / P-type InGaN / P-type GaN superlattice layer is 800° C. to 900° C., and the growth pressure is 50 torr to 500 torr.

[0025] A second aspect of the present invention further provides a method for preparing an epitaxial wafer of a light-emitting diode, comprising:

[0026] providing a substrate;

[0027] depositing a buffer layer on the substrate;

[0028] depositing an undoped GaN layer on the buffer layer;

[0029] depositing an N-type GaN layer on the undoped GaN layer;

[0030] depositing a multi-quantum well layer on the N-type GaN layer;

[0031] depositing a P-type combination layer on the multi-quantum well layer;

[0032] The P-type combination layer includes an AlN / InN / P-type AlGaN superlattice layer and an AlGaN / P-type InGaN / P-type GaN superlattice layer.

[0033] The implementation of the present invention has the following beneficial effects:

[0034] In the present invention, a P-type combination layer is provided on the multi-quantum well layer. The P-type combination layer includes an AlN / InN / P-type AlGaN superlattice layer and an AlGaN / P-type InGaN / P-type GaN superlattice layer. This can reduce the extension of underlying dislocations to the P-type GaN layer, improve the crystal quality of the P-type combination layer, reduce the dislocation density, reduce the absorption and reflection effects of the P-type combination layer on light emitted by the multi-quantum well layer, reduce the leakage of the light-emitting diode, reduce the electron overflow effect, and at the same time increase the activated Mg concentration, increase the hole concentration and hole injection efficiency, and increase the radiation recombination efficiency of electrons and holes, thereby improving the light output rate, luminous efficiency and antistatic performance of the light-emitting diode. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 : A schematic structural diagram of an epitaxial wafer of a light emitting diode in the present invention;

[0036] Figure 2 : Schematic diagram of the structure of the P-type combination layer in the present invention.

[0037] Reference numerals:

[0038] 100-substrate; 200-buffer layer; 300-undoped GaN layer; 400-N-type GaN layer; 500-multi-quantum well layer; 600-P-type combination layer; 610-AlN / InN / P-type AlGaN superlattice layer; 611-AlN layer; 612-InN layer; 613-P-type AlGaN layer; 620-AlGaN / P-type InGaN / P-type GaN superlattice layer; 621-AlGaN layer; 622-P-type InGaN layer; 623-P-type GaN layer. DETAILED DESCRIPTION

[0039] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail with reference to specific embodiments below.

[0040] In order to solve the above problems, the present invention provides a light emitting diode epitaxial wafer in a first aspect, such as Figure 1 As shown, it includes a substrate 100, a buffer layer 200, a non-doped GaN layer 300, an N-type GaN layer 400, a multi-quantum well layer 500 and a P-type combination layer 600 sequentially stacked on the substrate 100;

[0041] The P-type combination layer 600 includes an AlN / InN / P-type AlGaN superlattice layer 610 and an AlGaN / P-type InGaN / P-type GaN superlattice layer 620. Figure 2 shown.

[0042] In the present invention, providing a P-type combination layer 600 on the multi-quantum well layer 500 can reduce the electron overflow effect, improve the radiative recombination efficiency of electrons and holes, and thus improve the light extraction rate and luminous efficiency of the light-emitting diode. Among them, the AlN / InN / P-type AlGaN superlattice layer 610 can form an electron trap, reduce electron overflow, and improve electrostatic capacity, while the AlGaN / P-type InGaN / P-type GaN superlattice layer 620 can further reduce electron overflow, improve the surface smoothness of the AlGaN layer 621 and the P-type GaN layer 623, reduce the absorption and reflection of the light emitted by the multi-quantum well layer 500 by the P-type combination layer 600, reduce the leakage of the light-emitting diode, and improve the luminous efficiency of the light-emitting diode.

[0043] Preferably, the AlN / InN / P-type AlGaN superlattice layer 610 comprises a superlattice structure formed by alternating AlN layers 611, InN layers 612, and P-type AlGaN layers 613 from bottom to top. The P-type AlGaN layer 613 provides hole concentration, and the deposition of the AlN and InN layers 611 and 612 below it reduces the extension of underlying dislocations into the P-type GaN layer 623, thereby improving the crystal quality of the P-type combination layer 600 and reducing dislocation density. This reduces leakage current in the light-emitting diode and improves aging resistance and antistatic properties. The number of alternating periods in the AlN / InN / P-type AlGaN superlattice layer 610 is 3 to 8, with exemplary period numbers being 3, 4, 5, 6, 7, and 8.

[0044] Furthermore, the thickness of the AlN layer 611 is 1 nm to 10 nm, and exemplary thicknesses are 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, and 10 nm, but are not limited thereto.

[0045] Furthermore, the thickness of the InN layer 612 is 1 nm to 10 nm, and exemplary thicknesses are 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, and 10 nm, but are not limited thereto.

[0046] Furthermore, the thickness of the P-type AlGaN layer 613 is 5 nm to 10 nm, and exemplary thicknesses are 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, and 10 nm, but not limited thereto. The Al content in the P-type AlGaN layer 613 is 0.01 to 0.1, and exemplary Al content is 0.01, 0.03, 0.05, 0.07, 0.09, and 0.1, but not limited thereto; the doping element is Mg, and the Mg doping concentration is 1×10 18 atoms / cm 3 ~1×10 19 atoms / cm 3 , an exemplary doping concentration is 1×10 18 atoms / cm、3×10 18 atoms / cm、5×10 18 atoms / cm、7×10 18 atoms / cm、9×10 18 atoms / cm、1×10 19 atoms / cm, but not limited thereto.

[0047] Furthermore, the doping concentration of the P-type AlGaN layer 613 decreases with the increase of the number of cycles. The gradual decrease in doping concentration makes the holes evenly distributed on the surface, reduces the current congestion effect, improves the hole expansion efficiency, reduces the defect-trapped holes, and reduces non-radiative recombination.

[0048] Preferably, the AlGaN / P-type InGaN / P-type GaN superlattice layer 620 is a superlattice structure formed by alternating stacking of AlGaN layers 621, P-type InGaN layers 622 and P-type GaN layers 623 from bottom to top, with the number of alternating periods being 5 to 20, and exemplary period numbers being 5, 7, 9, 11, 13, 15, 17, 19, 2, but not limited thereto.

[0049] Furthermore, the Al component in the AlGaN layer 621 is 0.01 to 0.1, and the Al component is exemplarily 0.01, 0.03, 0.05, 0.07, 0.09, and 0.1, but not limited thereto; the thickness of the AlGaN layer 621 is 5 nm to 10 nm, and the exemplary thickness is 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, and 10 nm, but not limited thereto.

[0050] Furthermore, the Al component in the AlGaN layer 621 increases with the increase in the number of periods, thereby increasing the barrier height for preventing electron migration and helping to reduce the risk of electron overflow.

[0051] Furthermore, the thickness of the P-type InGaN layer 622 is 1 nm to 10 nm, and exemplary thicknesses are 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, and 10 nm, but not limited thereto. In the P-type InGaN layer 622, the In composition is 0.01 to 0.1, and exemplary In compositions are 0.01, 0.03, 0.05, 0.07, 0.09, and 0.1, but not limited thereto; the doping element is Mg, and the Mg doping concentration is 1×10 19 atoms / cm 3 ~1×10 21 atoms / cm 3 , the Mg doping concentration is 1×10 19 atoms / cm 3 , 2.5×10 19 atoms / cm 3 , 5×10 19 atoms / cm 3 , 7.5×10 19 atoms / cm 3 , 9×10 19 atoms / cm 3 , 1×10 20atoms / cm 3 , 2.5×10 20 atoms / cm 3 , 5×10 20 atoms / cm 3 , 7.5×10 20 atoms / cm 3 , 1×10 21 atoms / cm 3 , but not limited to this.

[0052] Furthermore, the doping concentration of the P-type InGaN layer 622 increases with the increase of the period number; the In component decreases with the increase of the period number; and the Mg doping concentration increases with the increase of the period number, which can provide sufficient holes for the light-emitting diode to emit light while reducing the resistance and the operating voltage. Combined with a small amount of In doping, it can effectively reduce the acceptor energy level of Mg, increase the activation rate of Mg, and increase the hole concentration.

[0053] Furthermore, the thickness of the P-type GaN layer 623 is 5 nm to 10 nm, and exemplary thicknesses are 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, and 10 nm, but not limited thereto. The doping element in the P-type GaN layer 623 is Mg, and the doping concentration of Mg is 1×10 19 atoms / cm 3 ~1×10 21 atoms / cm 3 , the Mg doping concentration is 1×10 19 atoms / cm 3 , 2.5×10 19 atoms / cm 3 , 5×10 19 atoms / cm 3 , 7.5×10 19 atoms / cm 3 , 9×10 19 atoms / cm 3 , 1×10 20 atoms / cm 3 , 2.5×10 20 atoms / cm 3 , 5×10 20 atoms / cm 3 , 7.5×10 20 atoms / cm 3 , 1×10 21 atoms / cm 3 , but not limited to this.

[0054] Furthermore, the doping concentration of the P-type GaN layer 623 increases with the number of cycles. Increasing the doping concentration of the P-type InGaN layer 622 with the number of cycles can further increase the hole concentration, thereby further reducing the resistance of the light-emitting diode and facilitating a reduction in the operating voltage.

[0055] It should be noted that the increasing and decreasing in the present invention are one of continuous change, gradient change or mixed gradient change.

[0056] Correspondingly, the present invention also provides a method for preparing the epitaxial wafer of the light-emitting diode, comprising:

[0057] (1) Providing a substrate 100;

[0058] Preferably, the substrate 100 can be one of a sapphire substrate, a SiO2 sapphire composite substrate, a silicon substrate, a silicon carbide substrate, a gallium nitride substrate, and a zinc oxide substrate; more preferably, it is a sapphire substrate. Sapphire is currently the most commonly used GaN-based LED substrate material. Sapphire substrates have mature preparation technology, low price, are easy to clean and handle, and have good stability at high temperatures.

[0059] (2) depositing a buffer layer 200 on the substrate 100;

[0060] Preferably, the buffer layer 200 is an AlN buffer layer. The AlN buffer layer provides a nucleation center with the same orientation as the substrate 100, releases the stress generated by the lattice mismatch between GaN and the substrate 100 and the thermal stress generated by the mismatch of thermal expansion coefficients, provides a flat nucleation surface for further growth, reduces the contact angle of its nucleation growth, and enables the island-like grown GaN grains to be connected into a surface within a smaller thickness, thereby transforming into two-dimensional epitaxial growth.

[0061] Furthermore, the buffer layer 200 is grown by PVD, and the thickness of the buffer layer 200 is 10 nm to 50 nm.

[0062] Furthermore, after the growth of the buffer layer 200 is completed, the substrate 100 coated with the buffer layer 200 can be transferred to MOCVD and pretreated in an H2 atmosphere for 1 minute to 10 minutes at a treatment temperature of 1000°C to 1200°C, and then nitridation treatment is continued to improve the crystal quality of the buffer layer 200 and effectively improve the crystal quality of the subsequently deposited GaN epitaxial layer.

[0063] (3) depositing a non-doped GaN layer 300 on the buffer layer 200;

[0064] Preferably, the thickness of the undoped GaN layer 300 is 1.0 μm to 5.0 μm; more preferably, 2.0 μm to 3.0 μm. The growth temperature of the undoped GaN layer 300 is high and the pressure is low, so the quality of the prepared GaN crystal is better. At the same time, as the thickness of GaN increases, the compressive stress will be released through stacking faults, line defects will be reduced, the crystal quality will be improved, and the reverse leakage will be reduced. However, increasing the thickness of the GaN layer consumes more Ga source material, which greatly increases the epitaxial cost of the LED. Therefore, at present, LED epitaxial wafers are usually grown with undoped GaN of 2.0 μm to 3.0 μm, which not only saves production costs, but also the GaN material has higher crystal quality.

[0065] Furthermore, in MOCVD, the growth temperature of the undoped GaN layer 300 is 1050° C. to 1200° C., and the growth pressure is 100 torr to 600 torr.

[0066] (4) depositing an N-type GaN layer 400 on the undoped GaN layer 300;

[0067] Preferably, the doping concentration of the N-type GaN layer 400 is 1×10 19 atoms / cm 3 ~5×10 19 atoms / cm 3 The N-type GaN layer 400 provides sufficient electrons for the LED to emit light, and the resistivity of the N-type GaN layer 400 is higher than that of the transparent electrode on the p-type GaN. Therefore, sufficient Si doping can effectively reduce the resistivity of the N-type GaN layer 400. Finally, sufficient thickness of n-type GaN can effectively release the stress and improve the luminous efficiency of the light-emitting diode.

[0068] Furthermore, the thickness of the N-type GaN layer 400 is 2.0 μm to 3.0 μm.

[0069] Furthermore, the growth temperature of the N-type GaN layer 400 is 1050° C. to 1200° C., and the growth pressure is 100 torr to 600 torr.

[0070] (5) depositing a multi-quantum well layer 500 on the N-type GaN layer 400;

[0071] Preferably, the multi-quantum well layer 500 is a periodic structure of alternating InGaN quantum well layers and AlGaN quantum barrier layers, with a stacking period of 6 to 12. Within a single period, the In composition of the InGaN quantum well layer is 0.1 to 0.5, and the thickness of the InGaN quantum well layer is 2 nm to 5 nm; the Al composition of the AlGaN quantum barrier layer is 0.01 to 0.1, and the thickness of the AlGaN quantum barrier layer is 8 nm to 20 nm.

[0072] Furthermore, the growth temperature of the InGaN quantum well layer is 790° C. to 810° C., and the growth pressure is 50 torr to 300 torr; the growth temperature of the AlGaN quantum barrier layer is 800° C. to 900° C., and the growth pressure is 50 torr to 300 torr.

[0073] (6) depositing a P-type combination layer 600 on the multi-quantum well layer 500;

[0074] The P-type combination layer 600 includes an AlN / InN / P-type AlGaN superlattice layer 610 and an AlGaN / P-type InGaN / P-type GaN superlattice layer 620 .

[0075] Preferably, the growth temperature of the AlN / InN / P-type AlGaN superlattice layer 610 is 800℃~900℃, and the growth pressure is 50torr~500torr; exemplary growth temperatures are 800℃, 820℃, 840℃, 860℃, 880℃, and 900℃, but are not limited to these; exemplary growth pressures are 50torr, 100torr, 150torr, 200torr, 250torr, 300torr, 30torr, 400torr, 450torr, and 500torr, but are not limited to these.

[0076] Preferably, the AlGaN / P-type InGaN / P-type GaN superlattice layer 620 is grown at a temperature of 800° C. to 900° C. and a growth pressure of 50 torr to 500 torr. Exemplary growth temperatures include, but are not limited to, 800° C., 820° C., 840° C., 860° C., 880° C., and 900° C.; exemplary growth pressures include, but are not limited to, 50 torr, 100 torr, 150 torr, 200 torr, 250 torr, 300 torr, 30 torr, 400 torr, 450 torr, and 500 torr.

[0077] Specifically, the growth temperature and growth pressure are adjusted, Al source and N source are introduced to grow the AlN layer 611, then the Al source is turned off, and the N source and In source are introduced to grow the InN layer 612. Finally, the In source is turned off, and the N source, Al source, Ga source and Mg source are introduced to grow the P-type AlGaN layer 613. At this time, one cycle of growth of the AlN / InN / P-type AlGaN superlattice layer 610 is completed, and then the AlN layer 611, InN layer 612 and P-type AlGaN layer 613 are repeatedly stacked and periodically grown until the number of cycles reaches the expected number.

[0078] Next, the growth temperature and growth pressure are adjusted, and the N source, Al source and Ga source are introduced to grow the AlGaN layer 621. Then, the Al source is introduced and turned off, and the In source, N source, Ga source and Mg source are introduced to grow the P-type InGaN layer 622. Finally, the In source is turned off, and the N source, Ga source and Mg source are continued to be introduced to grow the P-type GaN layer 623. At this time, one cycle of growth of the AlGaN / P-type InGaN / P-type GaN superlattice layer 620 is completed. Then, the AlGaN layer 621, the P-type InGaN layer 622 and the P-type GaN layer 623 are repeatedly stacked and periodically grown until the number of cycles reaches the expected number.

[0079] It should be noted that the present invention utilizes a Veeco C4 MOCVD (Metal Organic Chemical Vapor Deposition) device to achieve epitaxial wafer growth. High-purity H2 (hydrogen), high-purity N2 (nitrogen), or a mixture of high-purity H2 and high-purity N2 is used as the carrier gas. The N source is high-purity NH3, the Al source is TMAl (trimethylaluminum), the Ga source is TMGa (trimethylgallium), the In source is TMIn (trimethylindium), the Si source is SiH4, and the Mg source is CP2Mg.

[0080] The present invention will be further described below with specific embodiments:

[0081] Example 1

[0082] This embodiment provides an epitaxial wafer of a light-emitting diode, comprising a substrate, a buffer layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well layer, and a P-type combination layer stacked in sequence on the substrate;

[0083] The P-type combination layer includes an AlN / InN / P-type AlGaN superlattice layer and an AlGaN / P-type InGaN / P-type GaN superlattice layer.

[0084] The AlN / InN / P-type AlGaN superlattice layer is a superlattice structure formed by alternately stacking AlN layers, InN layers and P-type AlGaN layers from bottom to top, with the number of alternating periods being 6.

[0085] In each period, the thickness of the AlN layer is 5 nm; the thickness of the InN layer is 5 nm; the thickness of the P-type AlGaN layer is 7 nm, and the Al composition is 0.05.

[0086] The Mg doping concentration in the P-type AlGaN layer increases with the number of cycles from 1×10 19 atoms / cm 3 The gradient is reduced to 1×10 18 atoms / cm 3, that is, in the 1st to 6th cycles, the Mg doping concentration is 1×10 19 atoms / cm、9×10 18 atoms / cm、7×10 18 atoms / cm、5×10 18 atoms / cm、3×10 18 atoms / cm、1×10 18 atoms / cm.

[0087] The AlGaN / P-type InGaN / P-type GaN superlattice layer is a superlattice structure formed by alternately stacking AlGaN layers, P-type InGaN layers and P-type GaN layers from bottom to top, with the number of alternating periods being 12.

[0088] In each period, the thickness of the AlGaN layer is 8 nm; the thickness of the P-type InGaN layer is 6 nm; and the thickness of the P-type GaN layer is 7 nm.

[0089] The Al content in the AlGaN layer increases isogradiently from 0.1 to 0.01 as the number of cycles increases; the Mg doping concentration in the P-type InGaN layer increases from 1×10 19 atoms / cm 3 The gradient increases to 1×10 21 atoms / cm 3 The Mg doping concentration in the P-type GaN layer increases with the number of cycles from 1×10 19 atoms / cm 3 The gradient increases to 1×10 21 atoms / cm 3 .

[0090] It is prepared by the following preparation method:

[0091] (1) providing a substrate;

[0092] The substrate is a sapphire substrate.

[0093] (2) depositing a buffer layer on the substrate;

[0094] The buffer layer is an AlN buffer layer, which is grown in PVD and has a thickness of 30 nm.

[0095] After the buffer layer is grown, the substrate coated with the buffer layer can be transferred to MOCVD, pretreated in H2 atmosphere for 5 minutes at a treatment temperature of 1100°C, and then continued with nitridation treatment.

[0096] (3) depositing a non-doped GaN layer on the buffer layer;

[0097] The thickness of the non-doped GaN layer is 2.5 μm; the growth temperature is 1150° C., and the growth pressure is 300 Torr.

[0098] (4) depositing an N-type GaN layer on the undoped GaN layer;

[0099] The doping concentration of the N-type GaN layer is 2.5×10 19 atoms / cm 3 , thickness is 2.5μm; growth temperature is 1150℃, and growth pressure is 300torr.

[0100] (5) depositing a multi-quantum well layer on the N-type GaN layer;

[0101] The multi-quantum well layer is a periodic structure of alternating InGaN quantum well layers and AlGaN quantum barrier layers, with a stacking period of 10. Within a single period, the In composition of the InGaN quantum well layer is 0.22, and the thickness of the InGaN quantum well layer is 3.5nm; the Al composition of the AlGaN quantum barrier layer is 0.05, and the thickness is 9.8nm.

[0102] The growth temperature was adjusted to 795°C and the growth pressure was 200 torr. N source, Ga source and In source were introduced to grow the InGaN quantum well layer. Subsequently, the temperature of the reaction chamber was adjusted to 855°C, the In source was turned off, and Al source, Ga source and N source were introduced to grow the AlGaN quantum barrier layer. After completing one cycle of growth, the InGaN quantum well layer and the GaN quantum barrier layer were repeatedly stacked and grown periodically.

[0103] (6) depositing a P-type combination layer on the multi-quantum well layer;

[0104] The P-type combination layer includes an AlN / InN / P-type AlGaN superlattice layer and an AlGaN / P-type InGaN / P-type GaN superlattice layer.

[0105] The growth temperature of the AlN / InN / P-type AlGaN superlattice layer is 850° C. and the growth pressure is 250 Torr; the growth temperature of the AlGaN / P-type InGaN / P-type GaN superlattice layer is 850° C. and the growth pressure is 250 Torr.

[0106] Specifically, the growth temperature is adjusted to 850°C and the growth pressure is 250 torr. Al source and N source are introduced to grow the AlN layer. Then the Al source is turned off, and the N source and In source are introduced to grow the InN layer. Finally, the In source is turned off, and the N source, Al source, Ga source and Mg source are introduced to grow the P-type AlGaN layer. At this time, one cycle of growth of the AlN / InN / P-type AlGaN superlattice layer is completed. Then, the AlN layer, InN layer and P-type AlGaN layer are repeatedly stacked and grown periodically until the number of cycles reaches the expected number.

[0107] Next, N source, Al source and Ga source are introduced to grow the AlGaN layer, and then the Al source is introduced and turned off, and the In source, N source, Ga source and Mg source are introduced to grow the P-type InGaN layer. Finally, the In source is turned off, and the N source, Ga source and Mg source are continued to be introduced to grow the P-type GaN layer. At this time, one cycle of growth of the AlGaN / P-type InGaN / P-type GaN superlattice layer is completed. Subsequently, the AlGaN layer, P-type InGaN layer and P-type GaN layer are repeatedly stacked and grown periodically until the number of cycles reaches the expected number.

[0108] Example 2

[0109] This embodiment provides an epitaxial wafer of a light-emitting diode, which is basically the same as that of the first embodiment, except that:

[0110] The doping concentration of Mg in the P-type AlGaN layer is 5×10 18 atoms / cm 3 ;

[0111] The Al composition in the AlGaN layer is 0.05;

[0112] The doping concentration of Mg in the P-type InGaN layer is 1×10 20 atoms / cm 3 .

[0113] The doping concentration of Mg in the P-type GaN layer is 1×10 20 atoms / cm 3 .

[0114] Example 3

[0115] This embodiment provides an epitaxial wafer of a light-emitting diode, which is basically the same as that of the first embodiment, except that:

[0116] In each cycle, the Mg doping concentration in the P-type AlGaN layer is 5×10 18 atoms / cm 3 .

[0117] Example 4

[0118] This embodiment provides an epitaxial wafer of a light-emitting diode, which is basically the same as that of the first embodiment, except that:

[0119] In each period, the Al composition in the AlGaN layer is 0.05.

[0120] Example 5

[0121] This embodiment provides an epitaxial wafer of a light-emitting diode, which is basically the same as that of the first embodiment, except that:

[0122] In each cycle, the Mg doping concentration in the P-type InGaN layer is 1×10 20 atoms / cm 3 .

[0123] Example 6

[0124] This embodiment provides an epitaxial wafer of a light-emitting diode, which is basically the same as that of the first embodiment, except that:

[0125] In each cycle, the Mg doping concentration in the P-type GaN layer is 1×10 20 atoms / cm 3 .

[0126] Comparative Example 1

[0127] This comparative example provides an epitaxial wafer of a light-emitting diode, which is basically the same as that of Example 1, except that:

[0128] The epitaxial wafer comprises a substrate, a buffer layer, a non-doped GaN layer, an N-type GaN layer, a multi-quantum well layer and a P-type GaN layer which are sequentially stacked on the substrate.

[0129] Comparative Example 2

[0130] This comparative example provides an epitaxial wafer of a light-emitting diode, which is basically the same as that of Example 1, except that:

[0131] Wherein, the P-type combination layer includes an AlN / InN / P-type AlGaN superlattice layer and an AlGaN / P-type GaN superlattice layer.

[0132] The AlGaN / P-type GaN superlattice layer is a superlattice structure formed by alternately stacking AlGaN layers and P-type GaN layers from bottom to top, with the number of alternating periods being 12.

[0133] Performance Testing

[0134] The epitaxial wafers obtained in the embodiments and comparative examples were made into chips with a size of 10 mil*24 mil, and the photoelectric performance was tested. 300 LED chips were respectively extracted, and the luminous efficiency improvement, operating voltage and antistatic performance of the obtained chips were tested under 120 mA conditions. The luminous efficiency improvement was calculated based on comparative example 1; the operating voltage refers to the reduction in the operating voltage, which is specifically calculated based on comparative example 1.

[0135] Anti-static performance test (ESD): The anti-static performance of the base chip is tested using an electrostatic meter under the HBM (Human Body Model) model. The test chip can withstand the proportion of reverse 6kV static electricity. Specifically, it refers to the improvement rate of anti-static performance, which is calculated based on Comparative Example 1.

[0136] The performance test results are shown in Table 1.

[0137] Table 1 Performance test results of examples and comparative examples

[0138] Light efficiency improvement / % Working voltage / V ESD-6kV / % Example 1 3.3 -0.05 3.4 Example 2 2.6 -0.01 2.2 Example 3 3 -0.05 3.3 Example 4 2.9 -0.01 2.8 Example 5 2.7 -0.04 2.5 Example 6 2.7 -0.04 2.6 Comparative Example 1 0 0 0 Comparative Example 2 1.1 -0.02 1.2

[0139] From the above results, it can be seen that providing a P-type combination layer on the multi-quantum well layer, the P-type combination layer including the AlN / InN / P-type AlGaN superlattice layer and the AlGaN / P-type InGaN / P-type GaN superlattice layer, can reduce the extension of the underlying dislocations into the P-type GaN layer, improve the crystal quality of the P-type combination layer, reduce the leakage of the light-emitting diode, reduce the electron overflow effect, and at the same time improve the radiative recombination efficiency of electrons and holes, thereby improving the light output rate, luminous efficiency and antistatic performance of the light-emitting diode.

[0140] The above disclosure is only a preferred embodiment of the present invention and certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. An epitaxial wafer of a light emitting diode, characterized in that: The method comprises a substrate, a buffer layer, a non-doped GaN layer, an N-type GaN layer, a multi-quantum well layer and a P-type combination layer stacked in sequence on the substrate; Wherein, the P-type combination layer includes an AlN / InN / P-type AlGaN superlattice layer and an AlGaN / P-type InGaN / P-type GaN superlattice layer; The AlN / InN / P-type AlGaN superlattice layer is a superlattice structure formed by alternately stacking AlN layers, InN layers, and P-type AlGaN layers from bottom to top, with the number of alternating periods being 3 to 8; The AlGaN / P-type InGaN / P-type GaN superlattice layer is a superlattice structure formed by alternately stacking AlGaN layers, P-type InGaN layers and P-type GaN layers from bottom to top, with the number of alternating periods being 5 to 20.

2. The epitaxial wafer of a light emitting diode according to claim 1, wherein The doping element in the P-type AlGaN layer is Mg, and the doping concentration of Mg is 1×10 18 atoms / cm 3 ~1×10 19 atoms / cm 3 ; The Al component is 0.01~0.

1.

3. The epitaxial wafer of a light emitting diode according to claim 2, wherein: The doping concentration of the P-type AlGaN layer decreases as the number of cycles increases.

4. The epitaxial wafer of a light emitting diode according to claim 1, wherein The Al composition in the AlGaN layer is 0.01-0.1; In the P-type InGaN layer, the In component is 0.01-0.1; the doping element is Mg, and the doping concentration of Mg is 1×10 19 atoms / cm 3 ~1×10 21 atoms / cm 3 ; The doping element in the P-type GaN layer is Mg, and the doping concentration of Mg is 1×10 19 atoms / cm 3 ~1×10 21 atoms / cm 3 .

5. The epitaxial wafer of a light emitting diode according to claim 4, wherein: The Al component in the AlGaN layer increases with the increase of the number of periods; The doping concentration of the P-type InGaN layer increases with the increase of the number of cycles; the In component decreases with the increase of the number of cycles; The doping concentration of the P-type GaN layer increases with the increase of the number of cycles.

6. The epitaxial wafer of a light emitting diode according to claim 1 or 3, characterized in that: The thickness of the AlN layer is 1 nm to 10 nm; The thickness of the InN layer is 1 nm to 10 nm; The thickness of the P-type AlGaN layer is 5nm-10nm.

7. The epitaxial wafer of a light emitting diode according to claim 1 or 5, characterized in that: The thickness of the AlGaN layer is 5nm~10nm; The thickness of the P-type InGaN layer is 1 nm to 10 nm; The thickness of the P-type GaN layer is 5nm-10nm.

8. The epitaxial wafer of a light emitting diode according to claim 1, wherein: The growth temperature of the AlN / InN / P-type AlGaN superlattice layer is 800° C. to 900° C., and the growth pressure is 50 torr to 500 torr; The growth temperature of the AlGaN / P-type InGaN / P-type GaN superlattice layer is 800° C. to 900° C., and the growth pressure is 50 torr to 500 torr.

9. The method for preparing an epitaxial wafer of a light emitting diode according to any one of claims 1 to 8, wherein: include: providing a substrate; depositing a buffer layer on the substrate; depositing an undoped GaN layer on the buffer layer; depositing an N-type GaN layer on the undoped GaN layer; depositing a multi-quantum well layer on the N-type GaN layer; depositing a P-type combination layer on the multi-quantum well layer; The P-type combination layer includes an AlN / InN / P-type AlGaN superlattice layer and an AlGaN / P-type InGaN / P-type GaN superlattice layer.

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