Aluminum nitride crystals having low urbach energy and high transparency to deep-ultraviolet wavelengths

Patent metadata

Field	Value
Publication number	US-11555256-B2
Application number	US-201916444147-A
Country	US
Kind code	B2
Filing date	Jun 18, 2019
Priority date	Jun 19, 2018
Publication date	Jan 17, 2023
Grant date	Jan 17, 2023

Abstract

In various embodiments, single-crystal aluminum nitride boules and substrates have low Urbach energies and/or absorption coefficients at deep-ultraviolet wavelengths. The single-crystal aluminum nitride may function as a platform for the fabrication of light-emitting devices such as light-emitting diodes and lasers.

First claim

The invention claimed is:

1. An AlN single crystal having an Urbach energy ranging from 0.2 eV to 1.8 eV within an incident photon energy range of 5.85 eV to 6.0 eV, the Urbach energy E u being defined by:
ln

α
=

ln
⁢

⁢

α
0

+

(

hv

E
U

)

wherein α is an absorption coefficient of the AlN single crystal at an incident photon energy hv, and α 0 is a constant corresponding to the absorption coefficient at zero photon energy, and
wherein the AlN single crystal is a substrate having a diameter of at least 25 mm and a thickness of at least 100 μm.

2. The AlN single crystal of claim 1 , wherein the Urbach energy ranges from 0.21 eV to 1.0 eV.

3. The AlN single crystal of claim 1 , wherein the diameter is at least 50 mm.

4. The AlN single crystal of claim 1 , wherein an ultraviolet (UV) absorption coefficient of the AlN single crystal is less than 10 cm −1 for an entire wavelength range of 220 nm to 280 nm.

5. The AlN single crystal of claim 4 , wherein the UV absorption coefficient is less than 10 cm −1 and is no less than 5 cm −1 for the entire wavelength range of 220 nm to 280 nm.

6. The AlN single crystal of claim 4 , wherein the UV absorption coefficient is constant within ±2 cm −1 for the entire wavelength range of 220 nm to 280 nm.

7. The AlN single crystal of claim 4 , wherein the UV absorption coefficient is constant within ±1 cm −1 for the entire wavelength range of 220 nm to 280 nm.

8. The AlN single crystal of claim 1 , wherein an ultraviolet (UV) absorption coefficient of the AlN single crystal is less than 30 cm −1 for an entire wavelength range of 210 nm to 220 nm.

9. The AlN single crystal of claim 8 , wherein the UV absorption coefficient is less than 30 cm −1 and is no less than 5 cm −1 for the entire wavelength range of 210 nm to 220 nm.

10. The AlN single crystal of claim 1 , wherein an ultraviolet (UV) absorption coefficient of the AlN single crystal is less than 8 cm −1 for an entire wavelength range of 240 nm to 280 nm.

11. The AlN single crystal of claim 10 , wherein the UV absorption coefficient is less than 8 cm −1 and is no less than 5 cm −1 for the entire wavelength range of 240 nm to 280 nm.

12. The AlN single crystal of claim 1 , wherein an ultraviolet (UV) absorption coefficient of the AlN single crystal is less than 20 cm −1 for an entire wavelength range of 215 nm to 220 nm.

13. The AlN single crystal of claim 12 , wherein the UV absorption coefficient is less than 15 cm −1 for a wavelength of 220 nm.

14. The AlN single crystal of claim 12 , wherein the UV absorption coefficient is less than 20 cm −1 and is no less than 5 cm −1 for the entire wavelength range of 215 nm to 220 nm.

15. The AlN single crystal of claim 12 , wherein the UV absorption coefficient is less than 20 cm −1 and is no less than 10 cm −1 for the entire wavelength range of 215 nm to 220 nm.

16. The AlN single crystal of claim 1 , wherein an ultraviolet (UV) absorption coefficient of the AlN single crystal is less than 15 cm −1 for an entire wavelength range of 220 nm to 240 nm.

17. The AlN single crystal of claim 16 , wherein the UV absorption coefficient is less than 10 cm −1 for a wavelength of 230 nm.

18. The AlN single crystal of claim 16 , wherein the UV absorption coefficient is no less than 15 cm −1 and is less than 5 cm −1 for the entire wavelength range of 220 nm to 240 nm.

19. The AlN single crystal of claim 1 , wherein an ultraviolet (UV) absorption coefficient of the AlN single crystal is less than 15 cm −1 for an entire wavelength range of 220 nm to 230 nm.

20. The AlN single crystal of claim 1 , further comprising a light-emitting device disposed thereover.

21. The AlN single crystal of claim 20 , wherein the light-emitting device (i) comprises a light-emitting diode or a laser and (ii) is configured to emit ultraviolet light.

22. The AlN single crystal of claim 1 , wherein the thickness of the substrate is at least 200 μm.

23. The AlN single crystal of claim 1 , wherein the thickness of the substrate is at most 1 mm.

Assignees

• Bondokov Robert T
• Grandusky James R
• Chen Jianfeng
• Wang Shichao
• Kimura Toru
• Miebach Thomas
• Yamaoka Keisuke
• Schowalter Leo J
• Crystal Is Inc

Inventors

• Bondokov Robert T
• Grandusky James R
• Chen Jianfeng
• Wang Shichao
• Kimura Toru
• Miebach Thomas
• Yamaoka Keisuke
• Schowalter Leo J

Classifications

• C01B21/072

  with aluminium · CPC title

• C30B23/00

  Single-crystal growth by condensing evaporated or sublimed materials · CPC title

• C30B29/403 Primary

  AIII-nitrides · CPC title

• C30B23/066

  Heating of the material to be evaporated · CPC title

• C01P2006/60

  Optical properties, e.g. expressed in CIELAB-values · CPC title