# US 12,006,591 B2 · Method for preparing an aluminum doped silicon carbide crystal by providing a compound including aluminum and oxygen in a capsule comprised of a first and second material

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- Number: US 12,006,591 B2
- Document ID: US12006591B2
- Status: Granted
- Kind: B2
- Application number: 17/029,746
- Filed: 2020-09-23
- Published: 2021-09-02
- Granted: 2024-06-11
- Earliest claimed: 2020-03-02
- Assignees: II-Vi Advanced Materials, LLC
- Applicants: II-VI Delaware, Inc.
- Inventors: Ilya Zwieback; Varatharajan Rengarajan; Andrew E. Souzis; Gary E. Ruland
- Web page: https://patentgrep.com/patent/US12006591B2

## CPC

- C30B 23/00: Single-crystal growth by condensing evaporated or sublimed materials
- C30B 23/02: Epitaxial-layer growth
- C01B 32/956: Silicon carbide
- C04B 35/573: obtained by reaction sintering {or recrystallisation}
- C04B 35/65: Reaction sintering of free metal- or free silicon-containing compositions {(C04B35/573, C04B35/591 take precedence)}
- C30B 29/36: Carbides
- C04B 2235/3205: Alkaline earth oxides or oxide forming salts thereof, e.g. beryllium oxide
- C04B 2235/3826: Silicon carbides
- C04B 2235/3839: Refractory metal carbides
- C04B 2235/425: Graphite
- C04B 2235/722: Nitrogen content
- C04B 2235/76: Crystal structural characteristics, e.g. symmetry
- C04B 2235/9661: Colour
- G02F 1/0063: {Optical properties, e.g. absorption, reflection or birefringence (materials for non-linear optics G02F1/355)}
- H10D 62/60: Impurity distributions or concentrations
- C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

The present disclosure generally relates to silicon carbide crystals which may be used in optical applications, and to methods for producing the same. In one form, a composition includes an aluminum doped silicon carbide crystal having residual nitrogen and boron impurities. The concentration of aluminum in the silicon carbide crystal is greater than the combined concentrations of nitrogen and boron in the silicon carbide crystal, and the silicon carbide crystal includes an optical absorption coefficient of less than about 0.4 cm−1 at a wavelength in a range between about 400 nm to about 800 nm.

## Claims

### Claim 1

A method for preparing an aluminum doped silicon carbide crystal, comprising:
providing a silicon carbide source material and a silicon carbide monocrystalline seed in a growth crucible;
providing a solid aluminum dopant source material comprising a compound including aluminum and oxygen in a capsule; and
heating the growth crucible, with the capsule positioned therein, in a manner effective for producing silicon and carbon bearing vapors from the silicon carbide source material in the growth crucible and aluminum bearing vapors from the solid aluminum dopant source material in the capsule, and for precipitating the silicon and carbon bearing vapors and the aluminum bearing vapors on the silicon carbide monocrystalline seed to grow the aluminum doped silicon carbide crystal;
wherein the capsule includes a first material resistant to degradation from the aluminum dopant source and aluminum bearing vapors and a second material resistant to degradation from the silicon and carbon bearing vapors, the first material being different from the second material, and
wherein the capsule includes an inner component at least partially formed of the first material and an outer component disposed about the inner component and at least partially formed of the second material, wherein the outer component is in the form of an outer crucible, and wherein the inner component is in the form of an inner crucible positioned in the outer crucible.

### Claim 2 (depends on 1)

The method of claim 1, wherein the heating is further effective for creating solid aluminum oxide in the capsule and thereafter melting the solid aluminum oxide.

### Claim 3 (depends on 1)

The method of claim 1, wherein the first material includes a refractory metal selected from the group consisting of tantalum, molybdenum, tungsten, rhenium and alloys thereof.

### Claim 4 (depends on 3)

The method of claim 3, wherein the second material is graphite.

### Claim 5 (depends on 3)

The method of claim 3, wherein the second material is a refractory metal carbide.

### Claim 6 (depends on 5)

The method of claim 5, wherein the refractory metal carbide is tantalum carbide or niobium carbide.

### Claim 7 (depends on 1)

The method of claim 1, wherein the capsule includes a layer of refractory carbide.

### Claim 8 (depends on 1)

The method of claim 1, wherein the capsule further includes a capillary in gas phase communication with the aluminum dopant source material.

### Claim 9 (depends on 1)

The method of claim 1, wherein the aluminum dopant source material includes aluminum oxide.

### Claim 10 (depends on 1)

The method of claim 1, wherein the outer crucible includes a lid, wherein the inner crucible includes a lid, and wherein the lid of the outer crucible is removable to position the inner crucible in the outer crucible.

### Claim 11 (depends on 10)

The method of claim 10, further comprising providing a capillary channel through the lid of the outer crucible and the lid of the inner crucible, and releasing the aluminum bearing vapors from the capsule through the capillary channel.

### Claim 12 (depends on 10)

The method of claim 10, wherein the outer crucible includes the second material such that an external surface of the outer crucible is resistant to the degradation from the silicon and carbon bearing vapors, and wherein the inner crucible includes the first material such that an internal surface of the inner crucible is resistant to the degradation from the aluminum dopant source and the aluminum bearing vapors.

### Claim 13

A method for preparing an aluminum doped silicon carbide crystal, comprising:
providing a silicon carbide source material and a silicon carbide monocrystalline seed in a growth crucible;
providing a solid aluminum dopant source material comprising a compound including aluminum and oxygen in a capsule; and
heating the growth crucible, with the capsule positioned therein, in a manner effective for producing silicon and carbon bearing vapors from the silicon carbide source material in the growth crucible and aluminum bearing vapors from the solid aluminum dopant source material in the capsule, and for precipitating the silicon and carbon bearing vapors and the aluminum bearing vapors on the silicon carbide monocrystalline seed to grow the aluminum doped silicon carbide crystal;
wherein the capsule includes a first material resistant to degradation from the aluminum dopant source and aluminum bearing vapors and a second material resistant to degradation from the silicon and carbon bearing vapors, the first material being different from the second material, and
wherein the capsule includes an inner crucible at least partially formed of the first material and an outer crucible at least partially formed of the second material, and wherein the inner crucible of the capsule is positioned in the outer crucible of the capsule.