Silicon carbide crystals and methods for producing same

Patent metadata

Field	Value
Publication number	US-2021269937-A1
Application number	US-202017029746-A
Country	US
Kind code	A1
Filing date	Sep 23, 2020
Priority date	Mar 2, 2020
Publication date	Sep 2, 2021
Grant date	—

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.

First claim

What is claimed is:

1 . A composition, comprising an aluminum doped silicon carbide crystal having residual nitrogen and boron impurities, wherein the silicon carbide crystal includes aluminum at a concentration that is greater than a combined concentration 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.

2 . The composition of claim 1 , wherein the concentration of boron in the silicon carbide crystal is less than or equal to about 1·10 16 cm −3 .

3 . The composition of claim 1 , wherein the concentration of nitrogen in the silicon carbide crystal is less than or equal to about 1·10 16 cm −3 .

4 . The composition of claim 1 , wherein the concentration of aluminum in the silicon carbide crystal is less than about 5·10 17 cm −3 .

5 . The composition of claim 1 , wherein the silicon carbide crystal is substantially free of aluminum induced defects.

6 . The composition of claim 1 , wherein the silicon carbide crystal is a 4H polytype or a 6H polytype.

7 . The composition of claim 1 , wherein the silicon carbide crystal exhibits an absorption coefficient below about 0.4 cm −1 at a wavelength of about 450 nm.

8 . The composition of claim 1 , wherein the silicon carbide crystal exhibits an absorption coefficient below about 0.05 cm −1 at a wavelength of about 550 nm.

9 . The composition of claim 1 , wherein the silicon carbide crystal exhibits an absorption coefficient below about 0.01 cm −1 at a wavelength of 650 nm.

10 . 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.

11 . The method of claim 10 , wherein the heating is further effective for creating solid aluminum oxide in the capsule and thereafter melting the solid aluminum oxide.

12 . The method of claim 10 , 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.

13 . The method of claim 10 , wherein the capsule includes a first layer at least partially formed of the first material and a second layer at least partially formed of the second material.

14 . The method of claim 10 , wherein the first material includes a refractory metal selected from the group consisting of tantalum, molybdenum, tungsten, rhenium and alloys thereof.

15 . The method of claim 10 , wherein the second material is a refractory metal carbide.

16 . The method of claim 15 , wherein the refractory metal carbide is tantalum carbide or niobium carbide.

17 . The method of claim 10 , wherein the second material is graphite.

18 . The method of claim 10 , wherein the capsule further includes a layer of refractory carbide.

19 . The method of claim 10 , wherein the capsule further includes a capillary in gas phase communication with the aluminum dopant source material.

20 . The method of claim 10 , wherein the aluminum dopant source material includes aluminum oxide.

Assignees

• Ii Vi Delaware Inc

Inventors

• Zwieback Ilya
• Rengarajan Varatharajan
• Souzis Andrew N
• Ruland Gary E

Classifications

• G02B1/02 Primary

  made of crystals, e.g. rock-salt, semi-conductors (G02B1/08 takes precedence) · CPC title

• C30B29/66

  Crystals of complex geometrical shape, e.g. tubes, cylinders · CPC title

• C30B29/60

  characterised by shape · CPC title

• C30B23/02 Primary

  Epitaxial-layer growth · CPC title

• G02F1/0063

  Optical properties, e.g. absorption, reflection or birefringence (materials for non-linear optics G02F1/355) · CPC title