Method of producing large EMI shielded GaAs and GaP infrared windows

Abstract

A method of making GaP window slabs having largest dimensions of greater than 4 inches and GaAs IR window slabs having largest dimensions of greater than 8 inches, includes slicing and dicing at least one smaller GaAs or GaP single crystal boule, which can be a commercial boule, to form a plurality of rectangular slabs. The slabs are ground to have precisely perpendicular edges, which are polished to be ultra-flat and ultra-smooth, for example to a flatness of at least ?/10, and a roughness Ra of less than 10 nanometers. The slab edges are then aligned and fused via optical-contacting/bonding to create a large GaAs or GaP slab having negligible bond interface losses. A conductive, doped GaAs or GaP layer can be applied to the window for EMI shielding in a subsequent vacuum deposition step, followed by applying anti-reflection (AR) coatings to one or both of the slab faces.

Claims

1. An infrared window comprising a GaAs slab having a slab largest dimension that is greater than eight inches, or a GaP slab having a slab largest dimension that is greater than four inches, said slab being formed by grinding and polishing surrounding sides of a plurality of rectangular parallelepiped slabs, referred to herein as rectangular slabs, and then aligning and contacting the surrounding sides of the rectangular slabs so as to optically bond the rectangular slabs to each other, thereby forming a GaAs monolithic window slab having a largest dimension that is greater than eight inches or a GaP monolithic window slab having a largest dimension that is greater than four inches.

2. The infrared window of claim 1, wherein the monolithic window slab has a largest dimension that is greater than 12 inches.

3. The infrared window of claim 1, wherein the surrounding sides of each of the rectangular slabs surround largest faces of the rectangular slabs.

4. The infrared window of claim 1, wherein all of the rectangular slabs have a common size and shape.

5. The infrared window of claim 1, further comprising a conductive layer of doped GaAs or GaP applied to at least one face of the monolithic window slab.

6. The infrared window of claim 1, further comprising an anti-reflective coating applied to at least one face of the monolithic slab.

7. A method of making a GaAs slab having a largest dimension that is greater than eight inches or a GaP slab having a largest dimension that is greater than four inches, the slab being suitable for forming an infrared (IR) transparent window having a largest dimension that is greater than eight inches, the method comprising: obtaining a boule of GaAs or GaP; slicing the boule to form a plurality of rectangular parallelepiped slabs, referred to herein as rectangular slabs; grinding the rectangular slabs to have precisely perpendicular edges; polishing surrounding sides of each of the rectangular slabs to a high degree of flatness and smoothness; and aligning the surrounding sides of the rectangular slabs with each other and contacting the surrounding sides together so as to optically bond the rectangular slabs to each other, thereby forming a GaAs monolithic window slab having a largest dimension that is greater than eight inches, or a GaP monolithic window slab having a largest dimension that is greater than four inches.

8. The method of claim 7, wherein obtaining the boule includes obtaining the boule from a commercial source.

9. The method of claim 7, wherein polishing surrounding sides of each of the rectangular slabs to a high degree of flatness and smoothness includes polishing the surrounding sides to a flatness of better than ?/10 and to a smoothness with Ra less than 10 nanometers.

10. The method of claim 7, further comprising grinding faces of the monolithic window slab to remove bevels.

11. The method of claim 7, further comprising polishing faces of the monolithic window slab.

12. The method of claim 7, wherein the monolithic window slab has a largest dimension that is greater than 12 inches.

13. The method of claim 7, wherein the surrounding sides of each of the rectangular slabs surround largest faces of the rectangular slabs.

14. The method of claim 7, wherein all of the rectangular slabs have a common size and shape.

15. The method of claim 14, wherein grinding the rectangular slabs to have precisely perpendicular edges includes arranging the rectangular slabs in a stacked configuration, and grinding sides of the stack.

16. The method of claim 14, wherein polishing surrounding sides of each of the rectangular slabs to a high degree of flatness and smoothness includes arranging the rectangular slabs in a stacked configuration, and polishing sides of the stack.

17. The method of claim 16, wherein the sides of the stack are polished while the stack is mounted on a precision jig.

18. The method of claim 7, further comprising applying a conductive layer of doped GaAs or GaP to at least one face of the monolithic window slab.

19. The method of claim 18, wherein the conductive layer is applied using a vacuum deposition process.

20. The method of claim 7, further comprising applying an anti-reflective coating to at least one face of the monolithic slab.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A is a perspective view of a boule of GaAs or GaP showing the planes along which it is sliced and cut into rectangular tiles;

(2) FIG. 1B is a perspective view of the stack of tiles that result from the slicing and cutting of FIG. 1A;

(3) FIG. 1C illustrates the stack of tiles of FIG. 1B being ground to have precisely flat and perpendicular edges;

(4) FIG. 1D illustrates the sides of the stack of tiles of FIG. 1C being polished to nanometer-scale roughness while maintaining a high degree of flatness;

(5) FIG. 1E illustrates the alignment and optical bonding together of a plurality of tiles to form a monolithic slab;

(6) FIG. 1F illustrates the faces of the monolithic slab of FIG. 1E being ground to remove bevels and polished;

(7) FIG. 1G illustrates application of a conductive semiconductor layer to the monolithic slab of FIG. 1F by vacuum deposition; and

(8) FIG. 2 is a flow diagram illustrating a method embodiment of the present disclosure.

DETAILED DESCRIPTION

(9) The present disclosure is a method of making GaAs slabs having largest dimensions that are greater than 4 inches, and GaP slabs having largest dimensions that are greater than 8 inches, and preferably equal to 12 inches or more, wherein the slabs are sufficiently thick to be structurally competent when used as IR windows.

(10) With reference to FIG. 1A, the present disclosure teaches cutting slices 102 from GaAs or GaP single crystal boules 100 that are less than 12 inches in diameter, such as 6-inch GaAs boules, 8-Inch GaAs boules, or 3-inch GaP boules. In embodiments, the method includes obtaining the boules by purchasing them commercially.

(11) With reference to FIG. 1B, the slices 102 are then diced to form smaller rectangular parallelepiped slabs 104, referred to herein simply as rectangular slabs 104.

(12) With reference to FIG. 1C, in embodiments the rectangular slabs 104 are then beveled, stacked, and ground 108 such that they have precisely perpendicular edges. With reference to FIG. 1D, the stack is then mounted on a precision jig 106 and transformed into precursor slabs 110 by polishing 112 the surrounding, smaller sides of the rectangular slabs 104 to be ultra-flat and ultra-smooth. In embodiments, the sides of the precursor slabs 110 have a flatness of at least ?/10, and a roughness Ra of less than 10 nanometers.

(13) With reference to FIG. 1E, the smaller, surrounding sides of the precursor slabs 110 are then fused edge-to-edge via optical-contacting/bonding techniques to create a large GaAs or GaP window 114 having negligible bond interface losses. Finally, with reference to FIG. 1F, the faces 116 of the resulting GaAs or GaP window 114 are ground 118 to remove bevels, and polished.

(14) With reference to FIG. 1G, in some embodiments EMI shielded GaAs or GaP windows 116 are produced by subsequently applying a conductive, doped GaAs or GaP layer to the window 116, for example by placing the window 116 in a vacuum deposition apparatus 120 and applying the conductive layer by MOCVD, or by another vacuum deposition method, followed, in embodiments, by deposition of electrical contacts and/or single or double-side anti-reflection (AR) coatings.

(15) FIG. 2 is a flow diagram that illustrates an embodiment of the presently disclosed method in which EMI shielded IR windows are produced. The method begins by obtaining 200 a commercially produced boule 100 of GaAs or GaP, which is then sliced and diced 202 to form a plurality of rectangular slabs 104. The rectangular slabs are then ground 204 so that they have ultra-perpendicular edges, and the smaller sides of the slabs 104 that surround the largest sides are polished 206 so that they are ultra-flat and ultra-smooth.

(16) At this point, the rectangular slabs 104 are aligned and their smaller edges are brought together such that they are fused 208 by optical bonding to form a single, large window 116. The faces of the window 116 are then ground to remove bevels, and polished 210. Finally, a conductive layer of GaAs or GaP is applied 212 to at least one of the faces of the window 116, for example by vacuum deposition, after which anti-reflective coatings are applied 214.

(17) The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. Each and every page of this submission, and all contents thereon, however characterized, identified, or numbered, is considered a substantive part of this application for all purposes, irrespective of form or placement within the application. This specification is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of this disclosure.

(18) Although the present application is shown in a limited number of forms, the scope of the invention is not limited to just these forms, but is amenable to various changes and modifications. The disclosure presented herein does not explicitly disclose all possible combinations of features that fall within the scope of the invention. The features disclosed herein for the various embodiments can generally be interchanged and combined into any combinations that are not self-contradictory without departing from the scope of the invention. In particular, the limitations presented in dependent claims below can be combined with their corresponding independent claims in any number and in any order without departing from the scope of this disclosure, unless the dependent claims are logically incompatible with each other.