A PGaN-improved LED epitaxial structure and its preparation method

Abstract

The present invention provides a PGaN-improved LED epitaxial structure and a preparation method thereof. The epitaxial structure sequentially includes a substrate, a buffer layer, an intrinsic GaN layer, an N-type GaN layer, a light-emitting quantum well layer, and a P-type GaN layer connected in sequence from bottom to top. Among them, the light-emitting quantum well layer includes multiple levels of GaN barrier layers and InGaN well layers arranged in a cyclic manner, and the P-type GaN layer includes multiple levels of GaN intrinsic layers or low-doped metal layers and high-doped metal layers arranged in a cyclic manner. The preparation method is to grow a buffer layer, an intrinsic GaN layer, an N-type GaN layer, a light-emitting quantum well layer, and a P-type GaN layer on the substrate in an H2 environment in sequence. The present invention can effectively solve the problem of poor crystal quality caused by high Mg doping in the P-type layer in the LED epitaxial structure, reduce the Pits extended from the dislocations in the active layer, and thus improve the quality of LED products.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor optoelectronic devices, and particularly relates to a PGaN-improved LED epitaxial structure and a preparation method thereof. Background Art

[0002] With the continuous development of LED technology, its advantages such as high luminous efficiency, small light decay, energy saving, and environmental protection have been widely applied, and higher requirements have been put forward for LEDs, especially in terms of brightness and reliability. In the traditional epitaxial growth method of LEDs, the growth of the P-type layer is the most difficult. The P-type layer needs to solve the problems of improving the Mg doping efficiency and hole concentration, covering the Pits extending from the active layer, and the crystal quality of the P-type layer grown by the traditional high-low Mg doping superposition growth method is not ideal. At the same time, it fails to well bend and eliminate the dislocations extending from the active layer, thereby reducing the hole injection efficiency of the P-type layer and the luminous efficiency of the LED.

[0003] In view of this, there is an urgent need to develop a new PGaN-improved LED epitaxial technology today to overcome the above-mentioned defects existing in the existing LED epitaxial technology. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the present invention aims to provide a PGaN-improved LED epitaxial structure and a preparation method thereof. This technology can effectively solve the poor crystal quality caused by high Mg doping in the P-type layer and reduce the Pits extending from the active layer dislocations, thereby improving the quality of LED products. The technical solution of the present invention is as follows:

[0005] In the first aspect, the present invention provides a PGaN-improved LED epitaxial structure, which includes a substrate, a buffer layer, an intrinsic GaN layer, an N-type GaN layer, a light-emitting quantum well layer, and a P-type GaN layer connected in sequence from bottom to top; wherein, the light-emitting quantum well layer includes multiple levels of GaN barrier layers and InGaN well layers arranged in a cyclic manner, and the P-type GaN layer includes multiple levels of GaN intrinsic layers or low-doped metal layers and high-doped metal layers arranged in a cyclic manner.

[0006] Optionally, the substrate is a material suitable for the growth of III-V group semiconductor materials, such as sapphire, sapphire AlN film, GaN, silicon, silicon carbide, etc.

[0007] Further, the thickness of the buffer layer is 300-1000 nm, and the material is one of GaN, AlGaN, InAlGaN, InGaN or a combination of several of them in a superlattice or alternating stacking manner.

[0008] Further, the thickness of the intrinsic GaN layer is 1.0 - 2.0 um, and the material is one of GaN, AlGaN, InAlGaN, InGaN or a combination of several of them in a superlattice or alternating stack manner.

[0009] Further, the N-type GaN layer is Si-doped GaN with a thickness of 1 - 4 um, and the Si doping concentration is 1E18 - 3E19.

[0010] Further, in the light-emitting quantum well layer, the thickness of the GaN barrier layer is 3.0 - 10.0 nm, the thickness of the InGaN well layer is 3.0 - 6.0 nm, and the mass percentage content of In in the light-emitting quantum well layer is 8% - 20%.

[0011] Preferably, the cycle period of the GaN barrier layer and the InGaN well layer in the light-emitting quantum well layer is 3 - 10.

[0012] Further, the total thickness of the P-type GaN layer is 50 - 200 nm. The thicknesses of the multi-stage cyclic GaN intrinsic layer or low-doped metal layer and high-doped metal layer gradually decrease, and the thickness of the GaN intrinsic layer or low-doped metal layer at the same stage is greater than that of the high-doped metal layer.

[0013] Preferably, the thickness of the GaN intrinsic layer or low-doped metal layer is 5 - 20 nm, and the thickness of the high-doped metal layer is 3 - 15 nm.

[0014] Preferably, the cycle period of the GaN intrinsic layer or low-doped metal layer and the high-doped metal layer is 3 - 10.

[0015] Preferably, the P-type doping sources of the low-doped metal layer and the high-doped metal layer are Mg or Zn, with a concentration of 5E17 - 1E18 in the low-doped metal layer and a concentration of 5E18 - 1E20 in the high-doped metal layer.

[0016] Optionally, a P-type electron blocking layer is further provided between the light-emitting quantum well layer and the P-type GaN layer.

[0017] Further, the thickness of the P-type electron blocking layer is 30 - 80 nm, the Mg doping concentration is 5E18 - 3.5E19, and the material is a single-layer lattice of pAlGaN, pAlInGaN, pInGaN or a combined lattice of several of them or a superlattice of several of them.

[0018] In a second aspect, the present invention provides a method for preparing the above-mentioned improved PGaN-based LED epitaxial structure, including the following steps:

[0019] In an H 2 environment, a buffer layer is grown on the substrate;

[0020] Then, an intrinsic GaN layer is grown on the buffer layer;

[0021] Continue to grow an N-type GaN layer on the intrinsic GaN layer;

[0022] Continue to grow a light-emitting quantum well layer on the N-type GaN layer;

[0023] Continue to grow a P-type GaN layer on the grown multi-period light-emitting layer.

[0024] Furthermore, the growth conditions of the buffer layer are: temperature 800 - 1050 °C, pressure 100 - 200 Torr.

[0025] Furthermore, the growth conditions of the intrinsic GaN layer and the N-type GaN layer are: temperature 1000 - 1200 °C, pressure 100 - 200 Torr.

[0026] Furthermore, the growth conditions of the light-emitting quantum well layer are: temperature 700 - 900 °C, pressure 200 - 400 Torr.

[0027] Furthermore, the growth conditions of the P-type GaN layer are: temperature 850 - 950 °C, pressure 300 - 600 Torr.

[0028] Furthermore, the preparation method further includes: growing a P-type electron blocking layer on the light-emitting quantum well layer before growing the P-type GaN layer, and the growth conditions of the blocking layer are: temperature 850 - 950 °C, pressure 100 - 200 Torr.

[0029] The beneficial effects of the present invention are: The present invention provides a novel PGaN-improved LED epitaxial structure and a preparation method thereof. This technology can effectively solve the poor crystal quality caused by high Mg doping in the P-type layer of the LED epitaxial structure, and solve the Pits extended from the dislocations in the active layer, thereby improving the quality of LED products. Description of the Drawings

[0030] Figure 1 It is a structural formation process diagram of the PGaN-improved LED epitaxial structure of the present invention. Among them, 1 - substrate, 2 - buffer layer, 3 - intrinsic GaN layer, 4 - N-type GaN layer, 5 - light-emitting quantum well layer, 6 - P-type electron blocking layer, 7 - P-type GaN layer. Detailed Embodiments

[0031] In the description of the present invention, it should be noted that for those not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following is an explanation of the present invention rather than a limitation.

[0033] Embodiment 1

[0034] Please refer to Figure 1 , this embodiment provides a PGaN-improved LED epitaxial structure and a preparation method thereof. The epitaxial structure includes a silicon substrate, a buffer layer, an intrinsic GaN layer, an N-type GaN layer, a light-emitting quantum well layer, a P-type electron blocking layer, and a P-type GaN layer that are sequentially connected from bottom to top. Among them, the light-emitting quantum well layer includes multiple levels of GaN barrier layers and InGaN well layers arranged in a cyclic manner, and the P-type GaN layer includes multiple levels of low-doped metal layers and high-doped metal layers arranged in a cyclic manner.

[0035] In this embodiment, the buffer layer has a thickness of 600 nm and the material is GaN.

[0036] In this embodiment, the intrinsic GaN layer has a thickness of 1.5 μm and the material is GaN.

[0037] In this embodiment, the N-type GaN layer is Si-doped GaN with a thickness of 2 μm, and the Si doping concentration is 1e19.

[0038] In this embodiment, in the light-emitting quantum well layer, the GaN barrier layer has a thickness of 5 nm, the InGaN well layer has a thickness of 3 nm, and the mass percentage content of In in the light-emitting quantum well layer is 12%. The cycle period of the GaN barrier layer and the InGaN well layer is 7.

[0039] In this embodiment, the P-type electron blocking layer has a thickness of 50 nm, the Mg doping concentration is 1E19, and the material is pAlGaN.

[0040] In this embodiment, the thicknesses of the multi-level cyclic low-doped PGaN layer (i.e., the low-doped metal layer) and the high-doped PgaN (i.e., the high-doped metal layer) in the P-type GaN layer are each decreased by 2 nm step by step, and the thickness of the former is greater than that of the latter in the same-level low-doped layer and high-doped PGaN layer. The thickness of the first-level low-doped PGaN layer is 15 nm, the thickness of the first-level high-doped PGaN layer is 10 nm, and the cycle period is 3.

[0041] In this embodiment, the doping sources of the low-doped and high-doped P-type GaN are Mg, the concentration in the low-doped layer is 7E17, and the concentration in the high-doped layer is 1E19.

[0042] The preparation method of the above PGaN-improved LED epitaxial structure includes the following steps:

[0043] (1) In an H 2 environment, a buffer layer is grown on the substrate at a growth temperature of 900 °C and a pressure of 200 Torr;

[0044] (2) Then, an intrinsic GaN layer is grown on the buffer layer at a growth temperature of 1100 °C and a pressure of 200 Torr;

[0045] (3) Continuously grow an N-type GaN layer on the intrinsic GaN layer at a growth temperature of 1050 °C and a pressure of 200 Torr;

[0046] (4) Continuously grow a light-emitting quantum well layer on the N-type GaN layer at a growth temperature of 800 °C and a pressure of 200 Torr;

[0047] (5) Continuously grow a P-type electron blocking layer on the light-emitting quantum well layer at a growth temperature of 890 °C and a pressure of 100 Torr;

[0048] (6) Continuously grow a P-type GaN layer on the P-type electron blocking layer at a growth temperature of 900 °C and a pressure of 450 Torr.

[0049] 33*33 COW data: Luminance 521 mW@453.7 nm, IR and ESD yields are 95.5% and 99% respectively, and the electrical properties are good. As shown in Table 1.

[0050] Table 1

[0051]

[0052]

[0053] Example 2

[0054] Please refer to Figure 1 , this embodiment provides a PGaN-improved LED epitaxial structure and a preparation method thereof. The epitaxial structure includes a silicon substrate, a buffer layer, an intrinsic GaN layer, an N-type GaN layer, a light-emitting quantum well layer, a P-type electron blocking layer, and a P-type GaN layer connected in sequence from bottom to top; wherein, the light-emitting quantum well layer includes multiple levels of GaN barrier layers and InGaN well layers arranged in a cycle, and the P-type GaN layer includes multiple levels of GaN intrinsic layers and highly doped metal layers arranged in a cycle.

[0055] In this embodiment, the thickness of the buffer layer is 300 nm, and the material is GaN.

[0056] In this embodiment, the thickness of the intrinsic GaN layer is 1.0 um, and the material is GaN.

[0057] In this embodiment, the N-type GaN layer is Si-doped N-type GaN with a thickness of 4 um, and the Si doping concentration is 3e19.

[0058] In this embodiment, in the light-emitting quantum well layer, the thickness of the GaN barrier layer is 5 nm, the thickness of the InGaN well layer is 3 nm, and the mass percentage of In in the light-emitting quantum well layer is 12%. The cycle period of the GaN barrier layer and the InGaN well layer is 7.

[0059] In this embodiment, the thickness of the P-type electron blocking layer is 80 nm, the Mg doping concentration is 3.5E19, and the material is pAlInGaN.

[0060] In this embodiment, the thicknesses of the multi-stage cyclic GaN intrinsic layer and the highly doped metal layer both decrease by 1 nm step by step, and in the same-stage GaN intrinsic layer and highly doped metal layer, the former thickness is greater than the latter. The thickness of the first-stage GaN intrinsic layer is 10 nm, the thickness of the first-stage highly doped metal layer is 5 nm, and the cycle period is 5.

[0061] In this embodiment, the P-type doping source of the GaN intrinsic layer and the highly doped metal layer is Mg, where the concentration of the GaN intrinsic layer is 5E17 and the concentration of the highly doped metal layer is 5E18.

[0062] The preparation method of the above-mentioned PGaN-improved LED epitaxial structure includes the following steps:

[0063] (1) In an H 2 environment, a buffer layer is grown on the substrate at a growth temperature of 1050 °C and a pressure of 200 Torr;

[0064] (2) Then, an intrinsic GaN layer is grown on the buffer layer at a growth temperature of 1200 °C and a pressure of 200 Torr;

[0065] (3) Continuously grow an N-type GaN layer on the intrinsic GaN layer at a growth temperature of 1000 °C and a pressure of 200 Torr;

[0066] (4) Continuously grow a light-emitting quantum well layer on the N-type GaN layer at a growth temperature of 700 °C and a pressure of 200 Torr;

[0067] (5) Continuously grow a P-type electron blocking layer on the light-emitting quantum well layer at a growth temperature of 900 and a pressure of 100 Torr;

[0068] (6) Continuously grow a P-type GaN layer on the P-type electron blocking layer at a growth temperature of 950 °C and a pressure of 400 Torr.

[0069] 33*33 COW data: Luminance 528 mW @ 455.8 nm, IR and ESD yields are 97.8% and 100% respectively, and the electrical properties are good. As shown in Table 2.

[0070] Table 2

[0071] Pattern Wavelength nm Brightness mW IR Yield ESD Yield Example 2 33*33 455.85 528.32 97.82％ 100％

[0072] Comparative Example 1

[0073] This comparative example provides a PGaN-improved LED epitaxial structure and its preparation method. The difference from Example 1 is that in the P-type GaN layer, the total thickness of this layer is 76 nm and the number of cycles is 2.

[0074] Comparative Example 2

[0075] This comparative example provides a PGaN-improved LED epitaxial structure and its preparation method. The difference from Example 2 is that the thickness of the GaN intrinsic layer is equal and equal to the thickness of the highly doped layer, and the number of cycles is 6.

[0076] Comparative Example 3

[0077] This comparative example provides a PGaN-improved LED epitaxial structure and its preparation method. The difference from Example 1 is that the PGaN is a traditional low-doping and high-doping combination structure with thicknesses of 30 nm and 25 nm respectively. The summary of the comparative example data is shown in Table 3:

[0078] Table 3

[0079] Pattern Wavelength nm Brightness mW IR Yield ESD Yield Example 1 33*33 453.75 521.15 95.49％ 99％ Example 2 33*33 455.85 528.32 97.82％ 100％ Comparative Example 1 33*33 453.41 520.37 91.62％ 99％ Comparative Example 2 33*33 454.88 523.69 91.47％ 98％ Comparative Example 3 33*33 454.26 513.42 90.74％ 96％

[0080] In summary, the present invention provides a novel PGaN-improved LED epitaxial structure and its preparation method. This technology can effectively solve the poor crystal quality caused by high Mg doping in the P-type layer of the LED epitaxial structure, and reduce the Pits extending from the dislocations in the active layer, thereby improving the quality of LED products.

[0081] The above embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be subject to the appended claims.

Claims

1. A PGaN-improved LED epitaxial structure, characterized in that: it includes a substrate, a buffer layer, an intrinsic GaN layer, an N-type GaN layer, a light-emitting quantum well layer, and a P-type GaN layer connected in sequence from bottom to top; wherein, the light-emitting quantum well layer includes multiple levels of GaN barrier layers and InGaN well layers arranged in a cyclic manner, and the P-type GaN layer includes multiple levels of GaN intrinsic layers or low-doped metal layers and high-doped metal layers arranged in a cyclic manner; the total thickness of the P-type GaN layer is 50 - 200 nm, the thicknesses of the multiple levels of GaN intrinsic layers or low-doped metal layers and high-doped metal layers gradually decrease, and in the same level of GaN intrinsic layer or low-doped metal layer and high-doped metal layer, the thickness of the GaN intrinsic layer or low-doped metal layer is greater than that of the high-doped metal layer; the cycle period of the GaN intrinsic layer or low-doped metal layer and the high-doped metal layer is 3 - 10; the P-type doping sources of the low-doped metal layer and the high-doped metal layer are Mg or Zn, and their concentrations in the low-doped metal layer are 5E17 - 1E18, and their concentrations in the high-doped metal layer are 5E18 - 1E20.

2. A PGaN-improved LED epitaxial structure according to claim 1, characterized in that: a P-type electron blocking layer is further provided between the light-emitting quantum well layer and the P-type GaN layer.

3. A PGaN-improved LED epitaxial structure according to claim 1, characterized in that: the thickness of the P-type electron blocking layer is 30 - 80 nm, the Mg doping concentration is 5E18 - 3.5E19, and the material is a single-layer lattice of pAlGaN, pAlInGaN, pInGaN, or a combined lattice of several of them, or a superlattice of several of them.

4. A preparation method of a PGaN-improved LED epitaxial structure according to any one of claims 1 - 3, characterized in that: it includes the following steps: On H 2 In the environment, a buffer layer is grown on the substrate; then grow an intrinsic GaN layer on the buffer layer; continuously grow an N-type GaN layer on the intrinsic GaN layer; continuously grow a light-emitting quantum well layer on the N-type GaN layer; continuously grow a P-type GaN layer on the grown light-emitting quantum well layer.

5. A preparation method of a PGaN-improved LED epitaxial structure according to claim 4, characterized in that: the growth conditions of the P-type GaN layer are: temperature 850 - 950 °C, pressure 300 - 600 Torr.

6. A preparation method of a PGaN-improved LED epitaxial structure according to claim 4 or 5, characterized in that: the preparation method further includes: growing a P-type electron blocking layer on the light-emitting quantum well layer before growing the P-type GaN layer.

7. A preparation method of a PGaN-improved LED epitaxial structure according to claim 6, characterized in that: the growth conditions of the P-type electron blocking layer are: temperature 850 - 950 °C, pressure 100 - 200 Torr.

Images