KR102756086B1 - The manufacturing method of the germanium doped gallium oxide using the alkali base - Google Patents

Abstract

The present invention relates to a method and a product for producing gallium oxide doped with a group 14 element using an alkaline base, and more specifically, to a method for producing a germanium-doped beta-gallium oxide single crystal, in which potassium hydroxide, which is an alkaline base, is added to gallium oxide, then a doping material is added, the mixture is stirred for a predetermined period of time, a hydrochloric acid solution is added to form a hydroxyl group (-OH), and the mixture is crystallized at a high temperature while removing moisture.

Description

{The manufacturing method of the germanium doped gallium oxide using the alkali base}

The present invention was made under the support of the Small and Medium Business Administration of the Republic of Korea under project number S3140590. The research management specialized institution of the project is the Small and Medium Business Technology Information Promotion Agency, the research project name is ‘Manufacturing of Gallium Oxide for High-Quality Single Crystal Growth’, the implementing institution is K1 Solution Co., Ltd., and the research period is September 26, 2022 to September 26, 2023.

The present invention relates to a method for manufacturing gallium oxide doped with germanium using an alkaline base, which is an ultra-wide bandgap semiconductor element. More specifically, the present invention relates to a method for manufacturing gallium oxide doped with germanium (or silicon) by adding potassium hydroxide, which is an alkaline base, to gallium oxide, then adding germanium oxide (or silicon), which is a doping material, and stirring the mixture for a certain period of time, followed by adding hydrochloric acid to crystallize the mixture.

Semiconductors can be divided into intrinsic semiconductors and impurity semiconductors, and impurity semiconductors are divided into N-type semiconductors and P-type semiconductors depending on the type of impurity.

Intrinsic semiconductors are single crystals of one element, such as silicon or germanium, and do not conduct electricity because the electrons bound to the nucleus cannot move.

Electrical conductivity can be controlled by adding specific impurities to an intrinsic semiconductor to increase the number of electrons or holes. Such a semiconductor is called an impurity semiconductor.

When nitrogen (N), phosphorus (P), arsenic (As), and antimony (Sb), which are elements of group 15 and have 5 outermost electrons, are added as impurities to a silicon single crystal, which is an element of group 14, the electrons remain after covalent bonding with the silicon atoms, that is, when voltage is applied to the silicon crystal, they become free electrons and current flows.

Semiconductors with added group 15 elements are called N-type, negative type semiconductors, according to the polarity of the electrons, because electrons act as charge carriers.

Additionally, P-type semiconductors are created by adding Group 13 elements such as boron (B), aluminum (Al), gallium (Ga), and indium (In) as impurities to Group 14 elements such as carbon (C), silicon (Si), germanium (Ge), and tin (Sn).

Silicon-based semiconductors have played a fundamental and essential role in semiconductor device electronics for the past several decades. However, with the rapid development of technology, silicon-based semiconductors have reached their performance limits, and semiconductors with faster speeds and higher performance are required. The performance of semiconductors is usually determined by the difference in the energy bands of the raw materials, and the larger the difference in the band gap, the higher the possibility of using them in power devices and switching devices.

To overcome the limitations of silicon, wide band gap (WBG) materials such as compound semiconductors silicon carbide (SiC) and gallium nitride (GaN) are attracting attention and are approaching the commercialization stage.

However, recently, a new category called ultra-wide bandgap (UWBG) has been receiving a lot of attention beyond wide bandgap, and they have characteristics such as high breakdown strength and fast switching speed due to the larger bandgap than existing wide bandgap semiconductors.

Among them, gallium oxide not only has a higher band gap (4.9 eV) than silicon carbide (3.3 eV) and gallium nitride (3.4 eV), but also has the advantage of being easily manufactured through the melting growth method, like existing silicon-based semiconductors.

In addition, a doping process is generally used to improve the electrical and chemical performance of semiconductors. In the case of gallium oxide, group 4 elements such as silicon (Si), germanium (Ge), and tin (Sn) are utilized as N-type dopants, and various synthesis methods and doping methods are being actively researched and developed.

Republic of Korea Patent Publication No. 10-2022-0036255 (March 22, 2022)

However, in the case of hydrothermal synthesis, it is difficult to theoretically predict the shape and size of the final product in doping methods such as hydrothermal synthesis of gallium oxide complexes (Ge doped) and metal organic chemical vapor deposition (MOCVD), because the mechanism of crystal growth is complex.

In addition, in the case of the metal organic chemical vapor deposition process, there is a disadvantage in that the materials and gases used during the process mainly use harmful toxic substances, which may cause problems to the human body, and defects may occur due to differences in lattice sizes during doping due to differences in thermal expansion coefficients between the substrate and the deposition material.

And due to limited synthesis conditions, large-scale synthesis is not easy due to equipment and environmental constraints.

To solve the above problems, we propose a new method for producing gallium oxide doped with a Group 14 element including germanium using an alkaline base rather than the existing hydrothermal synthesis and metal organic chemical vapor deposition processes.

The present invention is expected to have the advantage of a simple manufacturing process and large-scale synthesis and doping through the above-mentioned manufacturing method.

Figure 1 is a schematic diagram of the synthesis of germanium-doped beta-gallium oxide according to the present invention.
Figure 2 is a reaction formula suggesting germanium-doped gallium oxide from gallium oxide and germanium oxide according to the present invention.
Figure 3 shows the doped germanium, gallium, and oxygen atomic % according to the concentration of germanium oxide, a dopant according to the present invention.
Figure 4 is an image confirmed by field emission scanning electron microscope (FE-SEM) equipment according to the present invention.

Hereinafter, with reference to the attached drawings, preferred embodiments of the present invention will be described in detail so that those with ordinary skill in the art can easily implement the present invention. However, when describing preferred embodiments of the present invention in detail, if it is determined that a specific description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, the same reference numerals are used throughout the drawings for parts that perform similar functions and actions.

Figure 1 is a schematic diagram of the synthesis of germanium-doped beta-gallium oxide.

First, a mixed solution of gallium hydroxide salt and germanium hydroxide salt is prepared by adding gallium oxide and a certain amount of germanium oxide to a potassium hydroxide solution.

After stirring for a certain period of time, hydrochloric acid is added to synthesize gallium hydroxide and germanium hydroxide.

Next, heat is applied to produce germanium-doped beta-gallium oxide.

The detailed method is to add 5.12 g of gallium oxide ( _Ga2O3 ), 2.06 g of germanium oxide ( _GeO2 ), and 34 g of potassium hydroxide (KOH) to 100 _mL of distilled water and stir at 68–72°C for 7–8 hours.

A mixture of gallium oxide and germanium dioxide reacts with potassium hydroxide to produce gallium hydroxide salt (K ₄ Ga ₂ O ₅ ) and germanium hydroxide salt (K ₄ GeO ₄ ). (S110)

Next, add 6 mL of concentrated hydrochloric acid (HCl) to the mixed solution of gallium hydroxide salt (K ₄ Ga ₂ O ₅ ) and germanium hydroxide salt (K ₄ GeO ₄ ).

When a solid is formed, it is placed in a filter and washed several times with distilled water, after which gallium hydroxide (Ga ₂ O(OH) ₄ ) and germanium hydroxide (Ge(OH) ₄ ) are formed. (S120)

Gallium hydroxide (Ga ₂ O(OH) ₄ ) and germanium hydroxide (Ge(OH) ₄ ) are dried in an oven at 90–110°C for 11–13 hours to remove moisture inside the materials.

The powder from which moisture has been removed is calcined again at a temperature of 750 to 850°C for 3 to 5 hours to produce beta-gallium oxide doped with germanium. (S130)

Figure 2 proposes a reaction mechanism for producing germanium-doped gallium oxide from gallium oxide and germanium oxide.

In the first equation (S210), gallium oxide and germanium oxide undergo a nucleophilic reaction with potassium hydroxide (KOH), and the hydroxyl group (-OH) attacks gallium and germanium, breaking the double bond (i.e., pi bond) between gallium and germanium and oxygen, and potassium binds to oxygen, which dissolves in water in the form of a salt.

In the second formula (S220), hydrochloric acid (HCl) is added to form a hydroxyl group (-OH).

In the third formula (S230), a single crystal of germanium combined with gallium oxide is created by removing water ( _H2O ) by applying heat of 800 degrees.

Figure 3 shows the doped germanium, gallium, and oxygen atomic % according to the concentration of dopant germanium oxide. This is the result confirmed by scanning electron microscope/energy dispersive X-ray elemental analysis (SEM/EDX) equipment.

When the dopant germanium oxide is 5% (weight %), the gallium atoms are 37.35 atomic%, the germanium atoms are 2.94 atomic%, and the oxygen atoms are 59.71 atomic%.

When the dopant germanium oxide is 10% (weight %), the gallium atoms are 36.82 atomic%, the germanium atoms are 5.36 atomic%, and the oxygen atoms are 57.82 atomic%.

When the dopant germanium oxide is 15% (weight %), the gallium atoms are 39.57 atomic%, the germanium atoms are 9.50 atomic%, and the oxygen atoms are 50.93 atomic%.

When the dopant germanium oxide is 20% (weight %), the gallium atoms are 42.04 atomic%, the germanium atoms are 11.09 atomic%, and the oxygen atoms are 46.87 atomic%.

These results showed that as the concentration of the dopant, germanium oxide, increased, the doped germanium atoms increased from 2.94 at%, 5.36 at%, 9.50 at%, and 11.09 at%.

Figure 4 is an image confirmed by a field emission scanning electron microscope (FE-SEM). a) is an electron microscope photograph when the dopant content is 5% (weight %), b) is an electron microscope photograph when the dopant content is 10% (weight %), c) is an electron microscope photograph when the dopant content is 15% (weight %), and d) is an electron microscope photograph when the dopant content is 20% (weight %).

Meanwhile, in the above example, germanium oxide was used as a dopant to manufacture beta-gallium oxide doped with germanium.

A person skilled in the art can manufacture beta-gallium oxide using carbon (C), silicon (Si), and tin (Sn), which are Group 14 elements such as germanium (Ge), as impurities, in the same sequence as the synthetic schematic diagram of Fig. 1 and the chemical reaction formula of Fig. 2.

Claims (3)

A step of mixing gallium oxide (Ga ₂ O ₃ ) and germanium oxide (GeO ₂ ) in a potassium hydroxide (KOH) solution and stirring;
A step in which gallium hydroxide salt (K ₄ Ga ₂ O ₅ ) and germanium hydroxide salt (K ₄ GeO ₄ ) are formed;
A step of forming gallium hydroxide (Ga ₂ O(OH) ₄ ) and germanium hydroxide (Ge(OH) ₄ ) by adding hydrochloric acid;
A method for manufacturing gallium oxide, comprising the steps of: removing moisture inside a material through a drying process in an oven at 90 to 110°C for 11 to 13 hours; and then manufacturing germanium-doped beta-gallium oxide (β-Ga ₂ O ₃ ) through a calcination process at a temperature of 750 to 850°C for 3 to 5 hours on the powder from which moisture has been removed;
In the first paragraph,
A method for manufacturing gallium oxide using one element selected from the 14th group elements carbon (C), silicon (Si), and tin (Sn) as an impurity instead of germanium
Gallium oxide manufactured by the manufacturing method described in either of paragraphs 1 and 2