JP2008300517A - Method of manufacturing light-emitting diode using zinc oxide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a light-emitting diode using zinc oxide, by which a gallium nitride nuclei forming layer is formed on a lithium aluminate substrate using a zinc oxide buffer layer like a single-crystal film, defective concentration of the gallium nitride is reduced, excellent lattice matching and crystal interface quality can be obtained and light emission efficiency and finished element function are improved. <P>SOLUTION: The producing method has a step of selecting a lithium aluminate substrate, a step of epitaxially growing a zinc oxide buffer layer and a gallium nitride nuclei forming layer on the lithium aluminate substrate to obtain a gallium nitride having high mass by utilizing a wurtzite structure similar in the zinc oxide and the gallium nitride and growing a multiple quantum well and a first metal electrode layer in a GaN/ZnO/LiAlO<SB>2</SB>structure after epitaxial growth, a step of removing the lithium aluminate substrate and the zinc oxide buffer layer by etching, and a step of growing a second metal electrode layer below the gallium nitride nuclei forming layer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a method for manufacturing a light-emitting diode using zinc oxide, and in particular, using a zinc oxide (ZnO) buffer layer that is in the form of a single crystal film, a gallium nitride (GaN) nucleation layer is replaced with lithium aluminate (LiAlO _2). ) On a substrate that successfully grows and reduces the defect density of gallium nitride, resulting in lattice matching and excellent crystal interface quality, improving luminous efficiency and completed device function .

In a conventional method for manufacturing a light emitting diode structure, a sapphire is used as a substrate, and gallium nitride is epitaxially formed on the sapphire to form a light emitting diode structure.

7 to 9 are a conceptual diagram of a structure when MQW and p-type electrode layers are grown on a conventional substrate, a structural conceptual diagram of a conventional light emitting diode, and a conceptual diagram of conventional lattice mismatching, respectively. As shown in the figure, first, a sapphire substrate 31 is prepared, and a gallium nitride multiple quantum well 32 (Multiple Quantum Well, MQW) and a p-electrode layer 33 are sequentially formed on the sapphire substrate 31. Epitaxial growth is performed, and an n-type electrode layer 34 is grown above the gallium nitride multiple quantum well 32, whereby a light emitting diode structure is formed.

However, the electroluminescence spectrum is dominated by the center wavelength in the vicinity of the p-type electrode layer 33 quantum well, resulting in non-uniform white light. Since the hole mobility is much worse than that of the electrons, the light emitting quantum wells are concentrated on the p-type electrode layer 33, and the light emission efficiency of the quantum wells of other colors is extremely deteriorated.

In addition, if the number of lattice mismatches between the gallium nitride multiple quantum well 33 and the sapphire substrate 31 is too high, the equilibrium position of the lattice epitaxially formed by the gallium nitride multiple quantum well 33 is deteriorated (as shown in FIG. 9). Therefore, the crystal interface quality deteriorates, and the quality of the finished product element deteriorates.

In addition, a conventional single-crystal zinc oxide substrate is used as a substrate, and gallium nitride is epitaxially formed on the zinc oxide substrate, so that the gallium nitride and zinc oxide are utilized in a similar structure. It is possible to obtain the advantage of higher quality than directly growing gallium nitride on sapphire, but since the zinc oxide is expensive due to the slightly thick zinc oxide used as a substrate, there is a problem that it is difficult to mass-produce. From the point of view that the advantage can be obtained by thin zinc oxide, it is useless. Therefore, the conventional and conventional ones are not practical.

The main object of the present invention is to successfully grow a gallium nitride nucleation layer on a lithium aluminate substrate using only a zinc oxide buffer layer in the form of a single crystal film, and to reduce the defect density of the gallium nitride. The present invention provides a method for manufacturing a light emitting diode using zinc oxide, which provides excellent lattice matching and crystal interface quality, and improves light emission efficiency and completed device function.

In order to achieve the above object, the present invention selects a lithium aluminate substrate, and epitaxially grows a zinc oxide buffer layer and a gallium nitride nucleation layer on the lithium aluminate substrate in order, and the zinc oxide and nitride Using a structure similar to gallium, the gallium nitride having a high mass can be obtained, and a multi-quantum well and a first metal electrode layer are grown on the GaN / ZnO / LiAlO ₂ structure after being epitaxially grown. Then, the lithium aluminate substrate and the zinc oxide buffer layer are removed by etching, and a second metal electrode layer is grown below the gallium nitride nucleation layer. . As a result, the zinc oxide buffer layer in the form of a single crystal film has succeeded in growing the gallium nitride nucleation layer on the lithium aluminate substrate, the defect density of the gallium nitride is reduced, and excellent Lattice matching and crystal interface quality are obtained, and luminous efficiency and completed device function are improved.

FIGS. 1 to 5 are a conceptual diagram of a manufacturing flow of the present invention, a conceptual diagram of a lithium aluminate substrate of the present invention, a structural conceptual diagram after epitaxially in the order of the present invention, and a substrate and a buffer layer of the present invention. FIG. 2 is a structural conceptual diagram after etching and a structural conceptual diagram of a light emitting diode of the present invention. As shown in the figure, the present invention is a method for producing a light emitting diode using zinc oxide. At least (A) a lithium aluminate (Lithium Aluminum Oxide, LiAlO ₂ ) substrate is prepared. Step 11: As shown in FIG. Lithium oxide substrate 21 is selected, and the substrate 21 is composed of lithium gallate (Lithium Gallium Oxide, LiGaO ₂ ), lithium silicon oxide (Lithium Silicon Oxide, Li ₂ SiO ₃ ), lithium germanate (Lithium Germanium Oxide, LiGeO ₃ ). , Sodium Aluminum Oxide, NaAlO ₂ , Sodium Germanium Oxide, Na ₂ GeO ₃ , Sodium Silicon Oxide, Na ₂ SiO ₃ , Lithium Phosphor Oxide, Li ₃ PO _4), lithium arsenate _{(lithium arsenic Oxide, Li 3 AsO} 4), lithium vanadate _{(lithium vanadium Oxide, Li 3 VO} 4), germanium Lithium magnesium _{(Lithium Magnesium Germanium Oxide, Li 2} MgGeO 4), germanium lithium zinc _{(Lithium Zinc Germanium Oxide, Li 2} ZnGeO 4), lithium germanium cadmium _{(Lithium Cadmium Germanium Oxide, Li 2} CdGeO 4), lithium magnesium silicon acid (Lithium Magnesium Silicon Oxide, Li ₂ MgSiO ₄ ), Lithium Zinc Silicon Oxide, Li ₂ ZnSiO ₄ , Lithium Cadmium Silicon Oxide, Li ₂ CdSiO ₄ , Sodium Magnesium Germanate (Sodium) Magnesium Germanium Oxide, Na ₂ MgGeO ₄ ), Sodium Zinc Germanium Oxide (Na ₂ ZnGeO ₄ ) or Sodium Zinc Silicon Oxide (Na ₂ ZnSiO ₄ ) B) On the lithium aluminate substrate, epitaxial epitaxial layers are sequentially formed. Step 12: As shown in FIG. 3, a zinc oxide (ZnO) buffer layer 22 and a gallium nitride (GaN) nucleation layer 23, which are in the form of a single crystal, are grown on the lithium aluminate substrate 21 from bottom to top. The epitaxially grown GaN / ZnO / LiAlO ₂ structure has multiple quantum wells (Multiple Wells).
Quantum Well, MQW) 24 and first metal electrode layer 25 are grown, and the multiple quantum well is a quantum well having one or more different well widths and barrier widths, and (C) the lithium aluminate substrate and the Step 13 of removing the zinc oxide buffer layer by etching: Step of immersing the epitaxial structure in an acidic solution and etching away the lithium aluminate substrate 21 and the zinc oxide buffer layer 22 as shown in FIG. The solution is nitric acid (HNO ₃ ), hydrofluoric acid (HF), or acetic acid (CH ₃ COOH). (D) Step 2 of growing the second metal electrode layer: As shown in FIG. A second metal electrode layer 26 is grown below the gallium nitride nucleation layer 23 to form a light emitting diode structure.

Thus, not only the zinc oxide buffer layer 22 that is in the form of a single crystal film is used to successfully grow the gallium nitride nucleation layer 23 on the lithium aluminate substrate 21, Defect density is reduced, excellent lattice matching and crystal interface quality are obtained, and luminous efficiency and completed device function are improved, such as light emitting diodes, laser diodes and field effect transistors.

FIG. 6 is a conceptual diagram of the lattice matching structure of the present invention. As shown in the figure, when a zinc oxide buffer layer that is in the form of a single crystal film is formed on a lithium aluminate substrate, the film structure is converted into a hexagonal columnar structure, and is arranged regularly in a honeycomb shape. Since a high quality zinc oxide buffer layer is first grown on the lithium aluminate substrate, the number of lattice mismatches between the two is low, a better crystal interface quality is obtained, and the luminous efficiency is improved. The

As described above, the present invention is a method for producing a light emitting diode using zinc oxide, which can effectively improve the conventional defects, reduce the defect density of gallium nitride, and obtain excellent lattice matching and crystal interface quality. In addition, because the light emission efficiency and completed device function are improved, the present invention is more progressive and more practical, and claims are filed according to law.

The above is merely a better embodiment of the present invention, and the present invention is not limited thereby, and equivalent changes made based on the scope of the claims and the description of the present invention. All modifications are within the scope of the claims of the present invention.

Conceptual diagram of the manufacturing flow of the present invention Conceptual diagram of the lithium aluminate substrate of the present invention Structural conceptual diagram after epitaxial in the order of the present invention Structural conceptual diagram after etching the substrate and buffer layer of the present invention Structure conceptual diagram of light emitting diode of the present invention Structural conceptual diagram of lattice matching of the present invention Conceptual diagram of conventional structure for growing MQW and p-type electrode layers on a substrate Conventional light emitting diode structure concept Conceptual diagram of conventional lattice mismatching

Explanation of symbols

(Invention part)
11 to 14 Step 21 Lithium aluminate substrate 22 Zinc oxide buffer layer 23 Gallium nitride nucleation layer 24 Multiple quantum well 25 First metal electrode layer 26 Second metal electrode layer (conventional portion)
31 sapphire substrate 32 gallium nitride multiple quantum well 33 p-type electrode layer 34 n-type electrode layer

Claims (3)

At least (A) a step of preparing a lithium aluminate substrate; and (B) a zinc oxide buffer layer and a gallium nitride nucleation layer are sequentially grown on the lithium aluminate substrate, and Growing a multiple quantum well and a first metal electrode layer in a GaN / ZnO / LiAlO ₂ structure; and (C) immersing the grown structure in an acidic solution to form the lithium aluminate substrate and the oxidation And (D) forming a second metal electrode layer below the gallium nitride nucleation layer to form a structure of a light emitting device. A method for manufacturing a light emitting diode using zinc oxide. The lithium aluminate substrate is composed of lithium gallate, lithium siliconate, lithium germanate, sodium aluminate, sodium germanate, sodium siliconate, lithium phosphate, lithium arsenate, lithium vanadate, lithium magnesium germanate, germanate A substrate composed of lithium zinc, lithium cadmium germanate, lithium magnesium siliconate, lithium zinc siliconate, lithium cadmium siliconate, sodium magnesium germanate, sodium zinc germanate, or sodium zinc siliconate. Item 2. A method for manufacturing a light-emitting diode using zinc oxide according to Item 1. 2. The method of manufacturing a light emitting diode using zinc oxide according to claim 1, wherein the acidic solution is nitric acid, hydrofluoric acid, or acetic acid.