RGB FULL-COLOR InGaN-BASED LED AND METHOD FOR PREPARING THE SAME

Abstract

An RGB full-color InGaN-based LED, a substrate material is covered with a lattice-matched 2D material ultra-thin layer in a surface as an intermediate layer, and an InGaN-based material epitaxial layer is grown on the 2D material ultra-thin layer; the 2D material ultra-thin layer is formed by a single material or formed by stacking more than one material. It can realize high-quality and high In content In.sub.xGa.sub.1-xN epitaxy on the currently available substrate surface, such that high-efficiency direct green/red light emitting diodes can be achieved, and the epitaxy and assembly processes can be simplified.

Claims

1. A red, green and blue (RGB) full-color InGaN-based light-emitting diode (LED), wherein: a substrate material is covered with a lattice-matched two-dimensional (2D) material ultra-thin layer on a surface of the substrate material as an intermediate layer, an InGaN-based material epitaxial layer is grown on the lattice-matched 2D material ultra-thin layer, and the lattice-matched 2D material ultra-thin layer is formed by a single material or formed by stacking more than one material.

2. The RGB full-color InGaN-based LED according to claim 1, wherein a 2D material of the lattice-matched 2D material ultra-thin layer is hexagonal boron nitride (hBN), graphene, hBNC, WS.sub.2, WSe.sub.2, MoS.sub.2 or MoSe.sub.2.

3. The RGB full-color InGaN-based LED according to claim 1, wherein the lattice-matched 2D material ultra-thin layer has a thickness that ranges from 0.5 nm to 1000 nm.

4. The RGB full-color InGaN-based LED according to claim 1, wherein: the lattice-matched 2D material ultra-thin layer is a composite layer structure, a top layer of the composite layer structure is made of a 2D material that matches an InGaN lattice of the InGaN-based material epitaxial layer, and a bottom layer of the composite layer structure is made of a 2D material with a barrier effect.

5. The RGB full-color InGaN-based LED according to claim 1, wherein the substrate material is sapphire, zinc oxide (ZnO), monocrystalline silicon (Si), SiC, GaN, ceramic or glass.

6. The RGB full-color InGaN-based LED according to claim 1, wherein: a metal catalytic layer is added between the substrate material and the intermediate layer, the metal catalytic layer has a total thickness that ranges from 0.5 nm to 3000 nm, and the metal catalytic layer comprises Fe, Co, Ni, Au, Ag, Cu, W, Mo, Ru or Pt.

7. A method for preparing the RGB full-color InGaN-based LED according to claim 1, wherein epitaxial steps for the InGaN-based material epitaxial layer and the substrate material are as follows: Step 1, performing epitaxial growth grade polishing on the substrate material, and preparing for subsequent manufacturing procedures through a pre-treatment; Step 2, covering a lattice-matched 2D material on the surface of the substrate material as the intermediate layer for an epitaxial InGaN material of the InGaN-based material epitaxial layer by using van der Waals epitaxy or quasi-van der Waals epitaxy technology; and Step 3, growing an epitaxial layer of InGaN-based material on the intermediate layer using the van der Waals epitaxy or the quasi-van der Waals epitaxy technology.

8. The method for preparing the RGB full-color InGaN-based LED according to claim 7, wherein: in Step 2, a single layer or a composite layer 2D material is covered on the surface of the substrate material, and a total thickness of the single layer or the composite layer 2D material ranges from 0.5 nm to 1000 nm.

9. The method for preparing the RGB full-color InGaN-based LED according to claim 7, wherein: between Step 1 and Step 2, the method comprises adding a metal catalytic layer, a total thickness of the metal catalytic layer ranges from 0.5 nm to 3000 nm, and the metal catalytic layer is grown or deposited on the surface of the substrate material before Step 2.

10. The method for preparing the RGB full-color InGaN-based LED according to claim 7, wherein: between Step 2 and Step 3, the method comprises lithographically dividing intermediate layer formed in Step 2 into domains, and each of the domains has a size from 1*1 mm.sup.2 to 1000*1000 mm.sup.2.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0029] FIG. 1 is a graph illustrating a band gap energy-lattice constant-wavelength relationship of conventional indium gallium nitride;

[0030] FIG. 2 is a schematic diagram illustrating a conventional zinc oxide substrate being corroded during the epitaxy process;

[0031] FIG. 3 is a manufacturing process diagram illustrating a substrate developed by a conventional French company Soitec;

[0032] FIG. 4 is a schematic diagram illustrating a structure of a conventional two-dimensional material transition metal dichalcogenides (TMDs);

[0033] FIG. 5 is a schematic diagram illustrating a structure of the conventional two-dimensional material hexagonal Boron Nitride (hBN);

[0034] FIGS. 6a and 6b are schematic diagrams illustrating conventional mechanical composition laminations;

[0035] FIGS. 7a and 7b are schematic diagrams illustrating conventional physical or chemical vapor deposition;

[0036] FIG. 8 is a schematic diagram illustrating the structure of conventional gallium nitride/graphene/silicon carbide;

[0037] FIG. 9 is a schematic structural diagram illustrating Embodiment 1 of the present disclosure;

[0038] FIG. 10 is a schematic structural diagram illustrating Embodiment 2 of the present disclosure.

[0039] In the drawings:

[0040] 1, substrate; 2, epitaxial layer; 3, 2D material ultra-thin layer; 31, top layer; 32, bottom layer; 4, metal catalytic layer.

DESCRIPTION OF EMBODIMENTS

[0041] The present disclosure will be further described in detail below with reference to the drawings and specific embodiments.

[0042] As shown in FIG. 9 and FIG. 10, in terms of structure, the RGB full-color InGaN-based LED provided in the present disclosure may be covered with a lattice-matched 2D material ultra-thin layer 3 on the material surface of the substrate 1 as an intermediate layer for In.sub.xGa.sub.1-xN epitaxy, and the InGaN-based material epitaxial layer 2 grows on the 2D material ultra-thin layer 3, the 2D material ultra-thin layer 3 may be composed of a single material as shown in FIG. 9 or formed by laminating more than one material as shown in FIG. 10. The 2D material ultra-thin layer 3 and the InGaN-based material epitaxial layer 2 and the substrate 1 use lattice matching or van der Waals Epitaxy (VDWE) to achieve stress relaxation.

[0043] Among them, the substrate 1 of the present disclosure may be a single crystal substrate, including but not limited to single crystal materials such as sapphire, zinc oxide ZnO, single crystal silicon Si, SiC, GaN, etc. Alternatively, the substrate 1 may be a material such as ceramics or glass. The 2D material of the present disclosure can use hexagonal Boron Nitride (hBN), graphene, hBNC, WS.sub.2, WSe.sub.2, MoS.sub.2 or MoSe.sub.2. The thickness of the 2D material ultra-thin layer 3 may range from 0.5 nm to 1000 nm.

[0044] The 2D material ultra-thin layer 3 shown in FIG. 9 is a single material with good lattice matching, such as WSe.sub.2 or MoSe.sub.2.

[0045] The 2D material ultra-thin layer 3 shown in FIG. 10 is a composite intermediate layer. The top layer 31 may be made of a 2D material with good lattice matching with InGaN, such as WSe.sub.2 or MoSe.sub.2, and the bottom layer 32 may be made of a 2D material with good barrier effect, such as hexagonal Boron Nitride (hBN), graphene. The lattice constants of various materials may be shown in Table 2.

TABLE-US-00002 TABLE 2 Material Lattice constant a (nm) hexagonal Boron Nitride (hBN) 0.25 Graphene 0.246 WSe.sub.2 0.3297 MoSe.sub.2 0.3283

[0046] The 2D material ultra-thin layer of the bottom layer 32 acts as a barrier to prevent defects in the substrate material from causing damage to the quality of the epitaxial layer and component performance. The defects in the substrate may include point defects (such as oxygen ions or other impurities) and line defects (such as dislocations).

[0047] In order to obtain a better structure, the present disclosure can add a metal catalytic layer 4 on the surface of the 2D material covering the substrate 1. The metal catalytic layer 4 can include Fe, Co, Ni, Au, Ag, Cu, W, Mo, Ru or Pt, etc. The metal catalytic layer 4 may be grown or deposited on the surface of the substrate 1 first, and a heat treatment process may also be required. The total thickness of the metal catalytic layer 4 may range from 0.5 nm to 3000 nm.

[0048] The present disclosure also provides a method for preparing an RGB full-color InGaN-based LED, the epitaxy steps for InGaN-based materials and substrate may be as follows:

[0049] In Step 1, performing epitaxial-ready growth grade polishing on the substrate 1 (wafer) material, and preparing for subsequent manufacturing procedures through appropriate pre-treatment (including wafer cleaning).

[0050] After step 1 and before step 2, manufacturing processes such as the metal catalytic layer 4 can be added in due course according to the growth requirements of the 2D material. The growth or deposition process of the 2D material covering the surface of the substrate 1 may require a metal catalytic layer 4 including Fe, Co, Ni, Au, Ag, Cu, W, Mo, Ru, or Pt to be grown or deposited on the surface of the substrate 1 in advance, heat treatment process may also be needed. The total thickness of the metal catalytic layer 4 ranges from 0.5 nm to 3000 nm.

[0051] Step 2, covering a lattice-matched 2D material on the surface of the substrate material as an intermediate layer for the epitaxial InGaN material by using van der Waals Epitaxy or quasi-van der Waals Epitaxy technology. It can be covered by a single layer or a composite layer 2D material ultra-thin layer 3. The 2D material covering the surface of the substrate 1 can adopt existing processes, including growth, deposition, transfer, coating, etc., as well as related necessary pre-treatment and post-treatment processes. The total thickness of a single layer or multiple layers ranges from 0.5 nm to 1000 nm.

[0052] After step 2 and before step 3, according to the epitaxial quality requirements of step 3, the 2D material intermediate layer in step 2 can be divided into domains by photolithography and other processes to relieve the stress. The domain size can be 1*1 mm.sup.2 to 1000*1000 mm.sup.2.

[0053] Step 3, growing an epitaxial layer 2 of InGaN-based material on the intermediate layer using van der Waals Epitaxy or quasi-van der Waals Epitaxy technology.

[0054] When MoSe.sub.2 or WSe.sub.2 is adopted as the outermost layer of the 2D material of the present disclosure, the lattice constant can be as high as 0.3283 nm or 0.3297 nm, and is highly matched to the InGaN epitaxial layer in the red light emission range. In addition to ensuring the quality of the epitaxial layer, it has the opportunity to simplify the epitaxial and assembly processes, and will also make the selection of substrate materials more widely available.

[0055] In the present disclosure, when the substrate material has any chemical composition or micro-defects that may affect the quality of the epitaxy, the 2D material can adopt hetero-structures, and choose a material with strong chemical stability or diffusion barrier performance as the bottom layer, for example hBN, to be bonded to the substrate, and the surface layer is made of a material that matches well with the epitaxial layer.

[0056] The InGaN template epitaxial growth at the beginning of the InGaN template substrate manufacturing process of French Soitec company already includes the basic material and epitaxial process cost. This part of the cost evaluation is not less than the process cost of the method of the present disclosure; and its follow-up must go through two InGaN layer peeling-bonding processes, and includes stress relaxation lithography as a necessary process. Regardless of the impact of multiple processes on the yield rate, the related processes can significantly increase the manufacturing cost of the finished InGaN template substrate. However, according to the company's announcement, the current upper limit of the lattice constant of its InGaN temple substrate is only 0.3205 nanometers (nm). This lattice constant value is actually only slightly higher than that of GaN, but still significantly lower than the green and red InGaN light emitting range. Judging from the fact that it is still unable to successfully produce robust green light products using GaN directly as the substrate, the company's technical achievements show that increasing the substrate lattice constant has a clear help, but it is obvious that more complicated and longer epitaxial processes are still needed in the production of components to gradually transfer to the appropriate epitaxial active layer, such that the cost of the component manufacturing will be higher. The present disclosure adopts van der Waals Epitaxy or quasi van der Waals Epitaxy technology, and the mismatched stress or strain energy can be relieved to a certain extent. The lattice constant value of the top layer of the substrate can also reach about 0.329 nanometers (nm), which ideally matches the green and red InGaN range of FIG. 1, and it is conducive to a simpler and more robust green and red InGaN light-emitting component process.

[0057] The foregoing descriptions are only preferred embodiments of the present disclosure, and are not intended to limit the present disclosure. It should be pointed out that the equivalent changes made by those skilled in the art in accordance with the design ideas of the present disclosure after reading the present specification shall fall within the scope of protection of the present disclosure.