CN115874268A

CN115874268A - Thermal field structure for inhibiting gallium oxide volatilization

Info

Publication number: CN115874268A
Application number: CN202211619076.3A
Authority: CN
Inventors: 潘明艳; 张璐; 齐红基; 孔文博
Original assignee: Shanghai Institute of Optics and Fine Mechanics of CAS
Current assignee: Shanghai Institute of Optics and Fine Mechanics of CAS
Priority date: 2022-12-15
Filing date: 2022-12-15
Publication date: 2023-03-31

Abstract

A thermal field structure for inhibiting gallium oxide volatilization comprises an iridium crucible, wherein a multi-layer heat preservation structure with a symmetrical central axis is adopted outside the iridium crucible and is called as a lower thermal field, the lower thermal field comprises heat preservation sand, an inner heat preservation barrel and an outer heat preservation barrel from inside to outside, and the bottoms of the inner heat preservation barrel and the outer heat preservation barrel are sealed; the upper part of the iridium crucible adopts a multi-layer heat preservation structure with axial symmetry, which is collectively called as an upper thermal field, the upper thermal field comprises an upper heat preservation body, a quartz cylinder and an outer quartz cylinder from inside to outside in sequence, and the upper heat preservation body is provided with an observation hole. The invention adopts the heat-insulating upper and lower thermal fields, the bottom of which is sealed, can greatly reduce the problems of volatilization and unstable airflow of the gallium oxide raw material at high temperature, improve the stability of the crystal growth process and provide important basis for large-scale high-quality gallium oxide single crystal preparation.

Description

Thermal field structure for inhibiting gallium oxide volatilization

Technical Field

The invention relates to the technical field of crystal growth, in particular to a thermal field structure for inhibiting volatilization of gallium oxide.

Background

Monoclinic gallium oxide (beta-Ga) ₂ O ₃ ) The forbidden band width is about 4.9eV, the breakdown field strength is as high as 8MV/cm, which is more than 20 times of Si and more than 2 times of SiC and GaN, and the Barley plus merit (epsilon mu E) thereof _g ³ Relative to Si) up to 3214.1, approximately 10 times that of SiC, 4 times that of GaN. Using beta-Ga ₂ O ₃ The developed device has smaller conduction loss and higher power conversion efficiency, is expected to have good application prospect in high-voltage and high-power scenes, and has great promotion effect on the national economy and national defense fields of new energy automobiles, high-speed rails, naval vessels and the like.

The mold-guiding method is that the beta-Ga is currently ₂ O ₃ The mainstream growth method of single crystal is to put a special mold with slits into beta-Ga ₂ O ₃ In the single crystal melt, the melt rises from the bottom to the top of the slit due to the siphon effect, the crystallization process is completed by controlling the temperature gradient at the top, and the shape of the mold surface determines the shape of the crystal. Since the crystallization process takes place at the top of the mold, the position of the mold in the temperature field is fixed. Therefore, the temperature gradient at the solid-liquid interface is not affected by the liquid level in the crucible, and a relatively constant state can be maintained. In addition, the convection of the melt in the slit is very weak, and thus the solid-liquid interface is stable.

Because gallium oxide crystals are volatile and decomposed at high temperature, partial decomposition products can be volatilized and rise and then are condensed, and then fall on the top of the mold, so that the stability of the growth process is influenced, and mixed crystals are generated. In addition, the gallium generated by decomposition and the iridium crucible can form gallium-iridium alloy, so that the crucible is seriously corroded, and more defects are generated in the crystal. The problem of volatilization is beta-Ga ₂ O ₃ One adverse factor in the growth process of single crystal, effective suppression of volatilization is the key to improve the quality of crystal and reduce the preparation cost.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a thermal field device for effectively inhibiting raw material volatilization in the process of growing gallium oxide single crystal by a guided mode method.

The technical scheme of the invention is as follows:

a thermal field structure for inhibiting gallium oxide volatilization comprises an iraurita crucible and is characterized in that a mold is arranged in the iraurita crucible, a copper coil is electrified to induce the iraurita crucible at the center to generate heat, so that a gallium oxide melt is melted, the melt rises to the top along a gap in the middle of the mold for crystal growth, a multi-layer heat preservation structure with symmetrical middle axes is adopted outside the iraurita crucible and is collectively called as a lower thermal field, the lower thermal field is composed of heat preservation sand, an inner heat preservation barrel and an outer heat preservation barrel in sequence from inside to outside, and the bottoms of the inner heat preservation barrel and the outer heat preservation barrel are sealed; the upper part of the iridium crucible adopts a multi-layer heat preservation structure with axial symmetry, which is collectively called as an upper thermal field, the upper thermal field comprises an upper heat preservation body, a quartz cylinder and an outer quartz cylinder from inside to outside in sequence, and the upper heat preservation body is provided with an observation hole.

The inner heat-insulating barrel and the outer heat-insulating barrel are made of heat-insulating materials such as zirconia or alumina.

The bottom thickness of the bottom parts of the inner heat-insulating barrel and the outer heat-insulating barrel is 10-30mm, the wall thickness is 5-30mm, and the height can be adjusted within the range of 100-400mm according to the height of the hearth and the coil.

Compared with the prior art, the invention has the beneficial effects that:

1) An upper thermal field and a lower thermal field for heat preservation are adopted; the upper thermal field adopts a double-layer quartz sleeve structure, and a zirconia thermal insulator is placed inside the upper thermal field, so that the stable control of airflow can be realized. The lower thermal field adopts a heat-insulating barrel with a sealed bottom (the material comprises heat-insulating materials such as zirconia, alumina and the like), zirconia sand is filled in the heat-insulating barrel, and an iraurita crucible is embedded in the center of the lower thermal field.

2) The bottom sealing heat-insulating barrel can effectively prevent harmful wind from entering the joint gap of the lower thermal field. Meanwhile, the double-layer quartz sleeve can reduce convection between the cavity and the outside. The combination of the two operations can greatly reduce the problems of volatilization and unstable airflow of the gallium oxide raw material at high temperature, improve the stability of the crystal growth process and provide important basis for large-scale high-quality gallium oxide single crystal preparation.

Drawings

FIG. 1 is a schematic diagram of the apparatus of the present invention;

FIG. 2 is a schematic view of a double-layered quartz cylinder according to the present invention;

FIG. 3 is a schematic view of the bottom-sealed heat-insulating barrel of the present invention;

FIG. 4 is a schematic view of a thermal field structure of a comparative example.

In the figure: 1-copper coil, 2-heat preservation sand, 3-outer heat preservation barrel, 4-inner heat preservation barrel, 5-iridium crucible, 6-mould, 7-upper heat preservation body, 8-quartz cylinder and 9-outer quartz cylinder.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be apparent to those skilled in the art that several modifications and improvements can be made without departing from the inventive concept. All falling within the scope of the present invention.

The invention is further illustrated by the following examples in conjunction with the accompanying drawings:

referring to fig. 1, a schematic diagram of a thermal field for gallium oxide growth is shown. The growth adopts an induction heating method, the copper coil 1 induces the iridium crucible 5 at the center to generate heat, so that the melt is melted, and the melt rises to the top along the gap in the middle of the die 6 and grows in a crystallization mode. The outer part of the crucible adopts a multi-layer heat preservation structure, and the structure is collectively called as a lower thermal field. Specifically, the heat-insulating sand 2 (made of zirconia), the inner heat-insulating barrel 4 and the outer heat-insulating barrel 3 (made of heat-insulating materials such as zirconia, alumina and the like) are respectively arranged from the inside to the outside. Referring to fig. 3, the bottoms of the heat-insulating

barrels

3 and 4 are sealed, the bottom thickness is 10-30mm, the wall thickness is 5-30mm, and the height can be adjusted within the range of 100-400mm according to the height of the hearth and the coil. The bottom sealing is better than the heat preservation sealing property and the heat preservation effect under the cylindrical shape, and can effectively prevent the phenomena of air leakage and the like, thereby inhibiting the volatilization of the gallium oxide raw material and improving the stability of the growth process.

The multilayer heat preservation structure on the upper part of the crucible is collectively called as an upper thermal field. The upper heat insulator 7 (made of zirconia), the inner quartz cylinder 8 and the outer quartz cylinder 9 are arranged in sequence from inside to outside. Because the upper heat insulator is provided with the observation hole, the quartz cylinder can effectively block the convection of gas inside and outside the heat insulation cavity while not influencing the observation visual field, thereby effectively inhibiting the gallium oxide raw material from continuously decomposing and volatilizing. The structure of the double-layer sleeve also enhances the sealing property and reduces the invasion of harmful wind. The diameter of the quartz cylinder is determined by the diameter of the upper heat insulator, the gap between the inner quartz cylinder and the upper heat insulator is 2-10mm, the wall thickness of the inner quartz cylinder and the wall thickness of the outer quartz cylinder are both 2-6mm, and the gap between the inner quartz cylinder and the outer quartz cylinder is 2-30mm.

When the thermal field of the embodiment is utilized to carry out crystal growth, no smog volatile matter can be seen in the whole process, the inner wall of the hearth is shiny without attachments, only a small amount of volatile matter is adhered to the inner wall of the heat preservation cavity, and the weight of the grown crystal is reduced by less than 5 g compared with the weight of the raw material put into the crucible. The thermal field structure effectively inhibits the generation of volatile matters and improves the stability of the growth process of the gallium oxide single crystal.

Comparative examples

The structure of the thermal field of the comparative example is schematically shown in fig. 4, and the difference from the example of the present invention is as follows:

(1) the lower thermal field adopts a cylindrical thermal insulator without a bottom, and the bottom adopts insulating bricks, insulating base plates and the like for heat preservation and support;

(2) a quartz cylinder is additionally arranged on the outer side of the upper heat-insulating body.

When the thermal field of the comparative example is used for crystal growth, the growth process is found to have more volatile matters in smoke form floating and rising in the thermal field, one part of the volatile matters is attached to the inner wall of the cavity of the thermal field, the other part of the volatile matters is attached to the seed rod, and the other part of the volatile matters is attached to the wall of the hearth, particularly in the overheating stage before inoculation. After the hearth is opened, a layer of white volatile matter is attached to the inner wall of the hearth, and the weight of the grown crystal is reduced by 10 g or more than that of the raw material put into the crucible. In addition, the problems of condensation, falling and the like of volatile matters also influence the stability of crystal growth, and are easy to cause the appearance of mixed crystals.

While the preferred embodiments of the present invention have been described in detail, it will be understood by those skilled in the art that the invention is not limited thereto, and that various changes and modifications may be made without departing from the spirit of the invention, and the scope of the appended claims is to be accorded the full scope of the invention.

Claims

1. A thermal field structure for inhibiting gallium oxide volatilization comprises an iraurita crucible (5) and is characterized in that a mold (6) is arranged in the iraurita crucible (4), the iraurita crucible (4) at the induction center is heated after a copper coil (1) is electrified, so that a gallium oxide melt is melted, the melt rises to the top along a gap in the middle of the mold (6) for crystal growth, a multi-layer heat preservation structure with axial symmetry is adopted outside the iraurita crucible (5) and is collectively called as a lower thermal field, the lower thermal field is composed of heat preservation sand (2), an inner heat preservation barrel (4) and an outer heat preservation barrel (3) from inside to outside in sequence, and the bottoms of the inner heat preservation barrel (4) and the outer heat preservation barrel (3) are sealed; the upper part of the iridium crucible (4) adopts a multi-layer heat preservation structure with a symmetrical central axis, which is collectively called as an upper thermal field, the upper thermal field comprises an upper heat preservation body (7), a quartz cylinder (8) and an outer quartz cylinder (9) from inside to outside in sequence, and the upper heat preservation body (7) is provided with an observation hole.

2. The thermal field structure for inhibiting gallium oxide volatilization according to claim 1, wherein the inner thermal insulation barrel (4) and the outer thermal insulation barrel (3) are made of thermal insulation materials such as zirconium oxide or aluminum oxide.

3. The thermal field structure for inhibiting gallium oxide volatilization according to claim 1, wherein the bottom thickness of the bottom of the inner heat-insulating barrel (4) and the bottom of the outer heat-insulating barrel (3) are 10-30mm, the wall thickness is 5-30mm, and the height can be adjusted within the range of 100-400mm according to the height of a hearth and a coil.