Narrow band algan filter

• US 5,182,670 A
• Filed: 08/30/1991
• Issued: 01/26/1993
• Est. Priority Date: 08/30/1991
• Status: Expired due to Term

• Current Assignee: APA Enterprises, Inc.
• Original Assignee: Clearfield, Inc
• Inventors: Kuznia, Jonathon N., Van Hove, James M., Khan, Muhammad A.
• Primary Examiner(s): Lerner, Martin
• Application Number:
  US07/755,510
• Time in Patent Office: 515 Days
• Field of Search: 357/30, 359/359, 359/361, 359/582, 359/578, 359/579, 359/586, 359/589, 252/588
• US Class Current: 359/359
• CPC Class Codes: G02B 5/285 comprising deposited thin solid films G02B5/281 - G02B5/289 take precedence; multilayered film filters for fibre optic multiplexing G02B6/29361
• CPC Class Codes: G02B 5/288 comprising at least one thin film resonant cavity, e.g. in bandpass filters
• CPC Class Codes: G02F 1/218 using semi-conducting materials
• CPC Class Codes: H01L 31/02165 using interference filters, e.g. multilayer dielectric filters interference filters G02B5/28
• CPC Class Codes: H01L 31/1852 comprising a growth substrate not being an AIIIBV compound
• CPC Class Codes: Y02E 10/544 Solar cells from Group III-V materials

Abstract

The invention is a filter device of at least two layers, the first layer of Al_x Ga.sub.(1-x) N and the second layer of Al_y Ga.sub.(1-y) N wherein x and y may have any value from 0 to 1. The invention may be used as a fixed wavelength or tunable wavelength filter or in ultraviolet detectors and laser devices, among other systems. Applications for the invention include detection of UV radiation in environments having a high level of incident infrared and visible radiation, as well as applications requiring detection of UV emission when no other radiation is present.

Claims

1. A filter device of at least two layers, said first layer comprising

View Dependent Claims (2, 3, 4, 5, 6, 7, 8)

2. The device of claim 1 wherein x ranges in value from about 0.5 to 1 and y ranges in value from about 0.5 to 1.

3. The device of claim 1 wherein said first layer has a refractive index ranging from about 2.2 to 2.5 and said second layer has a refractive index ranging from about 2.2 to 2.5.

4. The device of claim 1 wherein said first layer has a thickness ranging from about 200 to 10,000 Angstroms and said second layer has a thickness ranging from about 200 to

5. The device of claim 1 wherein said first layer has a dielectric constant ranging from about 2.2 to 2.8, and said second layer has a dielectric constant ranging from about 2.2 to 2.8.

6. The device of claim 1 wherein said device transmits light having a wavelength ranging from about 270 nanometers to 310 nanometers, and wherein x ranges from about 0.3 to 1, y ranges from about 0.3 to 1, the refractive index of said first layer ranges from about 2.2 to 2.8, the refractive index of said second layer ranges from about 2.2 to 2.8, the thickness of said first layer ranges from about 200 to 600 Å

, and the thickness of said second layer ranges from about 200 to 600 Å

.

7. The device of claim 1 wherein said first and second layers are formed in repeating alternating sequence.

8. The filter device of claim 7 wherein said filter allows transmission of wavelengths ranging from about 200 to about 10,000 nm.

9. A detector device comprising:

(a) an ultraviolet detector; and

(b) a filter device of at least two layers, said first layer comprising

space="preserve" listing-type="equation">Al.sub.y Ga.sub.(l-x) N

wherein x has a value ranging from about 0 to 1, and said device second layer comprising

space="preserve" listing-type="equation">Al.sub.y Ga.sub.(l-y) N

wherein y has a value ranging from about 0 to 1, said filter device having a band width determined by γ

/4=n₁ d₁ =n₂ d₂ wherein γ

is the wavelength of the energy to be transmitted through the filter, n₁ is the refractive index of said first layer, n₂ is the refractive index of said second layer, d₁ is the thickness of said first layer and d₂ is the thickness of said second layer.

10. The device of claim 9 wherein x ranges in value from about 0.5 to 1 and y ranges in value from about 0.5 to 1.

11. The device of claim 9 wherein said first layer has a refractive index ranging from about 2.2 to 2.8 and said second layer has a refractive index ranging from about 2.2 to 2.8.

12. The device of claim 9 wherein said first layer has a thickness ranging from about 200 to 10,000 Angstroms and said second layer has a thickness ranging from about 200 to 10,000 Angstroms.

13. The device of claim 9 wherein said first layer has a dielectric constant ranging from about 2.3 to 2.8, and said second layer has a dielectric constant ranging from about 2.3 to 2.8.

14. The device of claim 9 wherein said device transmits light having a wavelength ranging from about 270 nanometers to 310 nanometers, and wherein x ranges from about 0.3 to 1, y ranges from about 0.3 to 1, the refractive index of said first layer ranges from about 2.2 to 2.8, the refractive index of said second layer ranges from about 2.2 to 2.8, the thickness of said first layer ranges from about 200 to 600 Å

, and the thickness of said second layer ranges from about 200 to 600 Å

.

15. The device of claim 9 wherein said first and second layers are formed in repeating alternating sequence.

16. The filter device of claim 9 wherein said filter allows transmission of wavelengths ranging from about 200 to about 10,000 Å

.

17. A method of forming a filter device of at least two layers, said first layer comprising Al_x Ga.sub.(l-x) N wherein x has a value ranging from 0 to 1, said device second layer comprising Al_y Ga.sub.(l-y) N wherein y has a value ranging from about 0 to 1, said method comprising the step of determining the band width of a given layer by γ

/4=n₁ d₁ =n₂ d₂ wherein γ

is the wavelength of the energy to be transmitted through the filter, n₁ is the refractive index of said first layer and n₂ is the refractive index of said second layer, d₁ is the thickness of said first layer and d₂ is the thickness of said second layer.

18. The method of claim 17 wherein x ranges in value from about 0.5 to 1 and y ranges in value from about 0.5 to 1.

19. The method of claim 17 wherein said first layer has a refractive index ranging from about 2.2 to 2.5 and said second layer has a refractive index ranging from about 2.2 to 2.5.

20. The method of claim 17 wherein said first layer has a thickness ranging from about 200 to 10,000 Angstroms and said second layer has a thickness ranging from about 200 to 10,000 Angstroms.

21. The method of claim 17 wherein said first layer has a dielectric constant ranging from about 2.2 to 2.8, and said second layer has a dielectric constant ranging from about 2.2 to 2.8.

22. The method of claim 17 wherein said device transmits light having a wavelength ranging from about 270 nanometers to 310 nanometers, and wherein x ranges from about 0.3 to 1, y ranges from about 0.3 to 1, the refractive index of said first layer ranges from about 2.2 to 2.8, the refractive index of said second layer ranges from about 2.2 to 2.8, the thickness of said first layer ranges from about 200 to 600 Å

, and the thickness of said second layer ranges from about 200 to 600 Å

.

23. The method of claim 17 wherein said first and second layers are formed in repeating alternating sequence.

24. The method of claim 17 wherein said filter allows transmission of wavelengths ranging from about 200 to about 10,000 nm.