Thin silicon or germanium sheets and photovoltaics formed from thin sheets

Abstract

Thin semiconductor foils can be formed using light reactive deposition. These foils can have an average thickness of less than 100 microns. In some embodiments, the semiconductor foils can have a large surface area, such as greater than about 900 square centimeters. The foil can be free standing or releasably held on one surface. The semiconductor foil can comprise elemental silicon, elemental germanium, silicon carbide, doped forms thereof, alloys thereof or mixtures thereof. The foils can be formed using a release layer that can release the foil after its deposition. The foils can be patterned, cut and processed in other ways for the formation of devices. Suitable devices that can be formed form the foils include, for example, photovoltaic modules and display control circuits.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side perspective view of a reaction chamber for performing light reactive deposition at high production rates.

FIG. 2 is a schematic representation of a reactant delivery system for the delivery of vapor/gas reactants to a flowing reaction system, such as the reactor of FIG. 1.

FIG. 3 is a sectional side view of a reactant inlet nozzle with an aerosol generator for the delivery of aerosol and gas/vapor compositions into a reaction chamber, wherein the cross section is taken along line 3-3 of the insert. The insert shows a top view of an elongated reactant inlet.

FIG. 4 is a sectional side view of the reactant inlet nozzle of FIG. 3 taken along the line 44 of the insert in FIG. 3.

FIG. 5 is a schematic diagram of a light reactive dense deposition apparatus in which a dense coating is applied to a substrate within a reaction chamber.

FIG. 6 is a perspective view of a reactant nozzle delivering reactants to a reaction zone positioned near a substrate.

FIG. 7 is a sectional view of the apparatus of FIG. 6 taken along line 7-7.

FIG. 8 is a perspective view of an embodiment of a reaction chamber for performing light reactive dense deposition.

FIG. 9 is an expanded view of the reaction chamber of the light reactive deposition chamber of FIG. 8.

FIG. 10 is an expanded view of the substrate support of the reaction chamber of FIG. 8.

FIG. 11 is a perspective view of an alternative embodiment of an apparatus for performing light reactive dense deposition.

FIG. 12 is schematic diagram of the reactant delivery system of the apparatus in FIG. 11.

FIG. 13 is an expanded view of the reaction chamber of the apparatus of FIG. 11.

FIG. 14 is sectional view of the reaction chamber of FIG. 13 taken along line 14-14.

FIG. 15 is an alternative sectional view of the reaction chamber of FIG. 13 with the substrate holder portions removed and the baffle system visible.

FIG. 16 is a top view of the reactant inlet nozzle for the reaction chamber of FIG. 13.

FIG. 17 is a perspective view of a dual linear manipulator, which is part of the drive system for the nozzle of the reaction chamber of FIG. 13, where the dual linear manipulator is separated from the reaction chamber for separate viewing.

FIG. 18 is a schematic view of a light reactive deposition apparatus configured for transport of a large substrate.

FIG. 19 is a top view of a substrate with a powder coating covered in part with a mask.

FIG. 20 is a schematic perspective view of a layered structure with a release layer in which the arrow schematically depicts the separation of an overcoat layer from the layered structure.

FIG. 21 is schematic perspective view of a structured overcoat following removal from a release layer.

FIG. 22 is a fragmentary side view of layers of a layered overcoat structure.

FIG. 23 is a fragmentary side view of layers of an alternative embodiment of a layered overcoat structure.

FIG. 24 is a schematic perspective view of a large area layer with deposited islands patterned on the large area layer.

FIG. 25 is a top view of a transparent substrate with a plurality of semiconductor segments mounted on the transparent substrate for processing into photovoltaic cells.

FIG. 26 is a sectional side view of the structure in FIG. 25 taken along line 26-26 of FIG. 25.

FIG. 27 is a cut away side perspective view showing the interior of a light reactive deposition reaction chamber with a stage positioned to receive a produce flow from above.

FIG. 28 is a perspective view of the stage of FIG. 27 shown separated from the reaction chamber.

FIG. 29 is a photomicrograph of the top surface of the silicon foil as synthesized on a substrate by light reactive deposition.

FIG. 30 is a photomicrograph showing the edge where a fragment of silicon foil separated from the release layer and the remaining portion of the silicon foil is still attached.

FIG. 31 is a photograph showing a fragment of the silicon foil.

FIG. 32 is a photograph showing the opposite side of the silicon foil in FIG. 31 with the lighter color corresponding to remnants of the release layer.

Claims

1. A sheet comprising crystalline silicon, germanium, silicon carbide, silicon nitride, doped materials thereof or alloys thereof having an average thickness of no more than about 100 microns and a surface area of at least about 900 square centimeters, wherein the sheet is free or free along one surface while being releasably bound to a substrate along the opposite surface.

2. The sheet of claim 1 wherein the sheet comprises crystalline silicon.

3. The sheet of claim 2 wherein the crystalline silicon is polycrystalline.

4. The sheet of claim 1 wherein the sheet has an average thickness from about 20 nm to about 50 microns.

5. The sheet of claim 1 wherein the sheet has a standard deviation in thickness across the substrate of less than about 5 microns with a 1 centimeter edge exclusion.

6. The sheet of claim 1 wherein the sheet is a free structure.

7. The sheet of claim 1 wherein the sheet is releasably bound to a substrate with adhesive.

8. The sheet of claim 1 wherein the sheet has a minority carrier diffusion length of at least about 30 microns.

9. The sheet of claim 1 wherein the carriers have an electron mobility of at least about 5 cm2/Vs.

10. A method of forming a separable inorganic layer, the method comprising depositing an inorganic material from a reactive flow over an inorganic underlayer on a substrate wherein the underlayer material is soluble in a solvent that does not dissolve the inorganic material.

11. The method of claim 10 wherein the inorganic material comprises crystalline silicon, germanium, silicon carbide, silicon nitride, doped materials thereof or alloys thereof.

12. The method of claim 10 wherein the underlayer material is soluble in an aqueous liquid while the inorganic material is insoluble in the aqueous liquid.

13. The method of claim 10 wherein the underlayer material is soluble in an organic liquid while the inorganic material is insoluble in the organic liquid.

14. A method for forming a separable inorganic layer, the method comprising depositing an inorganic material over an underlayer material having a porosity of at least about 40 percent.

15. The method of claim 14 wherein the inorganic layer comprises silicon, gemanium, silicon carbide, doped materials thereof or alloys thereof.

16. The method of claim 15 wherein the underlayer material comprises silicon oxide, silicon nitride or silicon oxynitride.

17. A structure comprising a plurality of patterned islands of a first inorganic material with an average thickness of no more than about 100 microns, the patterned islands being located on top of a layer of a second inorganic material wherein the second inorganic material comprises a transparent substrate or a release layer.

18. The structure of claim 17 wherein the first inorganic material comprises silicon, germanium, silicon carbide, doped materials thereof or alloys thereof.

19. The structure of claim 17 wherein the second inorganic material comprises silica glass.

20. A method for forming a light receiving structure comprising depositing a semiconductor material onto a textured surface of a transparent substrate.

21. The method of claim 20 wherein the transparent substrate comprises an inorganic glass.

22. The method of claim 20 wherein deposition comprises directing a reactive flow having product compositions formed from the reaction of a reactive flow.

23. The method of claim 22 wherein the reaction is driven by absorption of light.

24. The method of claim 20 wherein the semiconductor material comprises silicon or doped silicon.

25. A method for forming discrete islands of a selected area and an average thickness of no more than about 100 microns, the method comprising cutting a larger sheet secured onto a substrate to form the islands with the selected area, wherein the sheet comprises a crystalline inorganic material.

26. A photovoltaic module comprising discrete islands formed by the method of claim 25 wherein the discrete islands comprise crystalline silicon, crystalline germanium or crystalline alloys thereof and wherein the substrate comprises a transparent inorganic glass.

27. A display comprising a control element and a plurality of light emitting elements with light emission of each element being under the control of the control element, the control element comprising a sheet of silicon/germanium-based semiconductor having an average thickness of no more than about 100 microns wherein the sheet is patterned with transistors operably interfacing with the sheet.