High luminous efficiency LED epitaxial wafer and preparation method thereof

Abstract

The present application provides a light emitting diode epitaxial wafer, which comprises a substrate, and a non-doped GaN layer, an N-type GaN layer, a multi-quantum well layer, a P-type AlGaN electron blocking layer and a P-type semiconductor layer which are sequentially stacked on the substrate. The P-type semiconductor layer comprises a P-type Ga 1‑a N a nanoparticle layer, an Al b Mg c N / In d Ga e N superlattice layer, a non-doped GaN layer, which can increase ionization of Mg in the P-type semiconductor layer, increase hole concentration and mobility, and increase light diffusion and light emitting efficiency.

Description

Technical Field

[0001] This invention relates to the field of light-emitting LEDs, and in particular to an LED epitaxial wafer capable of improving light emission quality and luminous efficiency. Background Technology

[0002] Currently, the concentration and mobility of holes in light-emitting diodes (LEDs) are lower than those of electrons, resulting in lower luminous quality and efficiency. This is particularly true for p-type GaN layers, which are typically Mg-doped GaN layers. Holes are generated by Mg replacing Ga lattice sites in GaN (i.e., ionization or activation). Because Mg has a high ionization energy in GaN, it is difficult to ionize Mg in GaN, resulting in a lower hole concentration in p-type GaN layers, making it difficult to achieve a hole concentration of 1×10⁻⁶. 18 cm -3 The above is true. Furthermore, the presence of unionized Mg in the p-type GaN layer causes scattering, resulting in low hole mobility within the p-type GaN, typically <10 cm⁻¹. 2 With a capacity of / V / s, the number of holes recombinating with electrons in a multi-quantum-well layer is limited, resulting in lower luminous efficiency for LEDs.

[0003] Existing technologies typically introduce electron blocking layer structures such as p-AlGaN, AlGaN / GaN short-period superlattices, or graded-component p-AlGaN between the quantum well light-emitting active region and the p-GaN drift region to block electron leakage. These electron blocking layers alleviate the sharp drop in efficiency to some extent, but still have a series of problems such as the large thickness leading to increased device operating voltage, more stringent epitaxial growth conditions, or complex fabrication processes. Summary of the Invention

[0004] To address the problem of low luminous efficiency in existing LED technologies, this invention provides a high-luminous-efficiency LED epitaxial wafer and its fabrication method.

[0005] The technical solution is as follows:

[0006] On one hand, the present invention provides a light-emitting diode epitaxial wafer, the light-emitting diode epitaxial wafer comprising a substrate 1, and an undoped GaN layer 2, an N-type GaN layer 3, a multiple quantum well layer 4, a P-type AlGaN electron blocking layer 5 and a P-type semiconductor layer 6 sequentially stacked on the substrate 1;

[0007] The P-type semiconductor layer 6 includes P-type GaN semiconductors sequentially stacked on the P-type AlGaN electron blocking layer 5. 1-a N a Nanoparticle layer 6, Al b Mg c N / In d Ga eN-type superlattice layer 7, undoped GaN layer 8, wherein 0.1≤a≤0.5, 0.1≤b≤0.5, 0.1≤c≤0.4, 0.1≤d≤0.3, 0.1≤e≤0.4. P-type Ga 1-a N a Nanoparticle layer 6 increases Al b Mg c N / In d Ga e The surface area of ​​the N superlattice layer can increase the hole concentration of the main quantum well layer, and the nanoparticles increase the diffuse reflection of light and increase the luminescence efficiency.

[0008] Preferably, P-type Ga 1-a N a Nanoparticle layer 6 contains 1-2 nm thick p-type Ga 1-a N a Buffer layer 6.1 and P-type Ga 1-a N a Particle layer 6.2.

[0009] The Al b Mg c N / In d Ga e The N-superlattice layer 7 covers the P-type Ga 1-a N a On nanoparticle layer 6, due to Al b Mg c N / In d Ga e The discontinuity between spontaneous polarization and piezoelectric polarization at the interface of the N heterojunction generates residual polarization charge, resulting in a high concentration of two-dimensional electron gas at the interface, which can significantly increase hole mobility. Al b Mg c Layer N 7.1 provides holes in In d Ga e After the In atoms diffuse in layer 7.2 of N, the activation energy of the Mg atoms is reduced, and the Al atoms are increased. b Mg c N / In d Ga e Hole concentration provided by N superlattice layer 7.

[0010] The undoped GaN layer 8 has a hole accumulation effect, which can increase the hole concentration in the P-type GaN layer. The undoped GaN layer is not affected by the scattering of Mg, which reduces the atomic activation energy, which is conducive to hole diffusion and increases the hole migration efficiency. In turn, it increases the number of holes recombine with electrons in the multi-quantum well layer and improves the luminous efficiency of LED.

[0011] Preferably, the Ga 1-aN a The density of nanoparticles in the nanoparticle layer is 10. 5 pcs / cm 2 -10 10 pcs / cm 2 The Ga 1-a N a The particle size of nanoparticles is 5nm-20nm. If the density and particle size of nanoparticles are too small, the effect on increasing the surface area is not obvious; if the density and particle size of nanoparticles are too large, the quality of the epitaxial layer will be affected.

[0012] Preferably, the P-type Ga 1-a N a The Mg doping concentration of the nanoparticle layer is 1×10⁻⁶. 15 atoms / cm 3 -1×10 18 atoms / cm 3 .

[0013] Preferably, the Al b Mg c N / In d Ga e The N superlattice layer consists of periodically alternating layers of Al b Mg c N layer 7.1 and In d Ga e N layers 7.2, with a stacking period of 2-8; the Al b Mg c The thickness of the N layer is 1nm-5nm; the In d Ga e The thickness of the N layer is 1nm-5nm.

[0014] Preferably, the thickness of the undoped GaN layer in the P-type layer can be 2–3 nm.

[0015] On the other hand, the present invention also provides a method for fabricating an epitaxial wafer of an external light-emitting diode, comprising the following steps:

[0016] S1. Prepare the substrate;

[0017] S2. An undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, and a P-type AlGaN electron blocking layer are sequentially placed on the substrate.

[0018] S3. Prepare a P-type semiconductor layer on the P-type AlGaN electron blocking layer;

[0019] Depositing a P-type semiconductor layer on the P-type AlGaN electron blocking layer includes the following steps:

[0020] S3.1, utilizing a circular void density of 10 5 pcs / cm 2 -10 10 pcs / cm 2 Metal mask for depositing P-type Ga on the P-type AlGaN electron blocking layer 1-a N a A nanoparticle layer, wherein 0.1 ≤ a ≤ 0.5, is used. The temperature of the reaction chamber is controlled at 950℃-1050℃, and the pressure is controlled at 100 torr-500 torr. A mixture of N2 and H2 is introduced as the carrier gas, and Ga and N sources are introduced to grow p-type Ga. 1-a N a After the nanoparticle layer is 5nm-20nm thick, the metal mask is removed.

[0021] S3.2. Control the temperature of the reaction chamber to 950℃-1050℃ and the pressure to 100 torr-500 torr. Introduce a mixture of N2 and H2 as the carrier gas, and introduce Al, Mg, and N sources to grow Al. b Mg c N-layer: Stop introducing Al and Mg sources, then introduce Ga, In, and N sources to grow In. d Ga e N layers, where 0.1≤b≤0.5, 0.1≤c≤0.4, 0.1≤d≤0.3, 0.1≤e≤0.4, are repeatedly stacked periodically 2-8 times. b Mg c N layers and In d Ga e N layers, to obtain the Al b Mg c N / In d Ga e N superlattice layer, wherein Al b Mg c The thickness of the N layer is 1nm-5nm; the In d Ga e The thickness of the N layer is 1nm-5nm;

[0022] S3.3, Control the temperature of the reaction chamber to 1100℃-1200℃, the pressure to 100 torr-500 torr, introduce N2 gas as the carrier gas, and introduce Ga and N sources. In the Al... b Mg c N / In d Ga e Undoped GaN layers are grown on N superlattice layers.

[0023] Preferably, step S3.1 involves depositing a P-type Ga on the P-type AlGaN electron blocking layer. 1-a Na After a buffer layer of 1-2 nm, a circular porosity of 10 is utilized. 5 pcs / cm 2 -10 10 pcs / cm 2 Metal mask for depositing P-type Ga on the P-type AlGaN electron blocking layer 1-a N a A nanoparticle layer, wherein 0.1 ≤ a ≤ 0.5, is used. The temperature of the reaction chamber is controlled at 950℃-1050℃, and the pressure is controlled at 100 torr-500 torr. A mixture of N2 and H2 is introduced as the carrier gas, and Ga and N sources are introduced to grow p-type Ga. 1-a N a After the nanoparticle layer is 5nm-100nm thick, the metal mask is removed.

[0024] On the other hand, the present invention also provides an LED, the LED comprising the light-emitting diode epitaxial wafer.

[0025] The beneficial effects of the technical solution of this invention are:

[0026] Using the P-type semiconductor layer with a specific structure and composition proposed in this invention, it is possible to increase the ionization of Mg in the P-type semiconductor layer, increase hole concentration and mobility, increase diffuse reflection of light, and increase luminous efficiency. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the structure of a light-emitting diode epitaxial wafer provided by the present invention;

[0029] Figure 2 This is a flowchart of a method for fabricating a light-emitting diode epitaxial wafer provided by the present invention. Detailed Implementation

[0030] This invention has been described by way of embodiments, but does not constitute a limitation thereof. Other variations of the disclosed embodiments, which are readily apparent to those skilled in the art, should fall within the scope of the claims of this invention, with reference to the description of this invention.

[0031] Example 1

[0032] A light-emitting diode epitaxial wafer, the light-emitting diode epitaxial wafer comprising a substrate, and an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, a P-type AlGaN electron blocking layer and a P-type semiconductor layer sequentially stacked on the substrate;

[0033] The P-type semiconductor layer includes P-type GaN semiconductors sequentially stacked on the P-type AlGaN electron blocking layer. 0.2 N 0.8 Nanoparticle layer, Al 0.1 Mg 0.3 N / In 0.2 Ga 0.4 N-superlattice layer, undoped GaN layer;

[0034] The P-type Ga 0.2 N 0.8 The Mg doping concentration of the nanoparticle layer is 1×10⁻⁶. 15 atoms / cm 3 .

[0035] The P-type Ga 0.2 N 0.8 Nanoparticle layer deposition, utilizing a circular porosity of 10 5 pcs / cm 2 A metal mask was used to prepare the reaction chamber at a temperature of 950°C and a pressure of 100 torr. A mixture of N2 and H2 was introduced as the carrier gas, along with Ga and N sources, to grow p-type Ga. 1-a N a After the nanoparticle layer reaches 10 nm, the metal mask is removed.

[0036] The Al 0.1 Mg 0.3 N / In 0.2 Ga 0.4 The N superlattice layer was prepared by controlling the temperature of the reaction chamber at 1050℃ and the pressure at 100 torr, using a mixture of N2 and H2 as the carrier gas, and introducing Al, Mg, and N sources to grow Al. 0.1 Mg 0.3 N-layer: Stop introducing Al and Mg sources, then introduce Ga, In, and N sources to grow In. 0.2 Ga 0.4 N layers, repeatedly stacked periodically 4 times, to obtain the Al. 0.1 Mg 0.3 N / In 0.2 Ga 0.4 N superlattice layer, wherein Al b Mg c The thickness of the N layer is 2 nm; the In d Ga e The thickness of the N layer is 3nm;

[0037] The undoped GaN layer was prepared by controlling the temperature of the reaction chamber at 1100℃ and the pressure at 100 torr, introducing N2 as a carrier gas, and introducing Ga and N sources to grow an undoped GaN layer of 2nm.

[0038] Comparative Example 1

[0039] The difference between this comparative example and Example 1 is that the P-type semiconductor layer is a P-type GaN layer with a Mg doping concentration of 1×10⁻⁶. 15 atoms / cm 3 Everything else is the same as in Example 1. Compared with Comparative Example 1, Example 1 showed a 14.3% increase in luminous efficiency. Experimental results demonstrate that using the P-type semiconductor layer with the specific structure and composition proposed in this invention can increase the ionization of Mg in the P-type semiconductor layer, increase hole concentration and mobility, increase diffuse reflection of light, and increase luminous efficiency.

Claims

1. A light-emitting diode epitaxial wafer, the light-emitting diode epitaxial wafer comprising a substrate (1) and an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, a P-type AlGaN electron blocking layer and a P-type semiconductor layer sequentially stacked on the substrate (1); The P-type semiconductor layer includes P-type GaN semiconductors sequentially stacked on the P-type AlGaN electron blocking layer. 1-a N a Nanoparticle layer (6), Al b Mg c N / In d Ga e N superlattice layer (7), undoped GaN layer (8), wherein, 0.1≤a≤0.5, 0.1≤b≤0.5, 0.1≤c≤0.4, 0.1≤d≤0.3, 0.1≤e≤0.4; P type Ga 1-a N a The nanoparticle layer (6) contains p-type Ga 1-a N a Buffer layer and P-type Ga 1-a N a Granular layer; The Al b Mg c N / In d Ga e The N-superlattice layer covers the P-type Ga 1-a N a On the nanoparticle layer, the undoped GaN layer has a hole accumulation effect; The Al b Mg c N / In d Ga e The N superlattice layer consists of periodically alternating layers of Al b Mg c N layers and In d Ga e N layers, with a stacking period of 2-8; The Al b Mg c The thickness of the N layer is 1nm-5nm; the In d Ga e The thickness of the N layer is 1nm-5nm.

2. The light-emitting diode epitaxial wafer according to claim 1, characterized in that, The P-type Ga 1-a N a The density of nanoparticles in the nanoparticle layer is 10. 5 pcs / cm 2 -10 10 pcs / cm 2 .

3. The light-emitting diode epitaxial wafer according to claim 2, characterized in that, The P-type Ga 1-a N a The particle size of the nanoparticles ranges from 5 nm to 20 nm.

4. A method for fabricating a light-emitting diode epitaxial wafer, wherein the epitaxial wafer is the epitaxial wafer according to any one of claims 1-3, comprising the following steps: S1. Prepare the substrate; S2. An undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, and a P-type AlGaN electron blocking layer are sequentially placed on the substrate. S3. Prepare a P-type semiconductor layer on the P-type AlGaN electron blocking layer; Depositing a P-type semiconductor layer on the P-type AlGaN electron blocking layer includes the following steps: S3.1, utilizing a circular void density of 10 5 pcs / cm 2 -10 10 pcs / cm 2 Metal mask for depositing P-type Ga on the P-type AlGaN electron blocking layer 1-a N a A nanoparticle layer, wherein 0.1 ≤ a ≤ 0.5, is used. The temperature of the reaction chamber is controlled at 950℃-1050℃, and the pressure is controlled at 100 torr-500 torr. A mixture of N2 and H2 is introduced as the carrier gas, and Ga and N sources are introduced to grow p-type Ga. 1-a N a After the nanoparticle layer is 5nm-20nm thick, the metal mask is removed. S3.

2. Control the temperature of the reaction chamber to 950℃-1050℃ and the pressure to 100 torr-500 torr. Introduce a mixture of N2 and H2 as the carrier gas, and introduce Al, Mg, and N sources to grow Al. b Mg c N-layer: Stop introducing Al and Mg sources, then introduce Ga, In, and N sources to grow In. d Ga e N layers, where 0.1≤b≤0.5, 0.1≤c≤0.4, 0.1≤d≤0.3, 0.1≤e≤0.4, are repeatedly stacked periodically 2-8 times. b Mg c N layers and In d Ga e N layers, to obtain the Al b Mg c N / In d Ga e N superlattice layer, wherein Al b Mg c The thickness of the N layer is 1nm-5nm; the In d Ga e The thickness of the N layer is 1nm-5nm; S3.3, Control the temperature of the reaction chamber to 1100℃-1200℃, the pressure to 100 torr-500 torr, introduce N2 gas as the carrier gas, and introduce Ga and N sources. In the Al... b Mg c N / In d Ga e Undoped GaN layers are grown on N superlattice layers.

5. The method for fabricating a light-emitting diode epitaxial wafer according to claim 4, characterized in that, Step S3.1: Deposit P-type Ga on the P-type AlGaN electron blocking layer. 1-a N a After a buffer layer of 1-2 nm, a circular porosity of 10 is utilized. 5 pcs / cm 2 -10 10 pcs / cm 2 Metal mask for depositing P-type Ga on the P-type AlGaN electron blocking layer 1-a N a A nanoparticle layer, wherein 0.1 ≤ a ≤ 0.5, is used. The temperature of the reaction chamber is controlled at 950℃-1050℃, and the pressure is controlled at 100 torr-500 torr. A mixture of N2 and H2 is introduced as the carrier gas, and Ga and N sources are introduced to grow p-type Ga. 1-a N a After the nanoparticle layer is 5nm-100nm thick, the metal mask is removed.

6. An LED comprising a light-emitting diode epitaxial wafer according to any one of claims 1-3.

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