Epitaxial lift off in inverted metamorphic multijunction solar cells
First Claim
1. A method for manufacturing a solar cell using a process for selectively freeing an epitaxial layer from a single crystal substrate upon which it was grown, comprising:
- providing a first substrate of gallium arsenide;
depositing a separation layer on said first substrate;
depositing on the separation layer a sequence of epitaxial layers of semiconductor material forming a solar cell including;
forming over the separation layer an upper first solar subcell having a first band gap and including a semiconductor contact layer;
forming over said first solar subcell a middle second solar subcell having a second band gap smaller than said first band gap;
forming a graded interlayer over said second solar subcell; and
forming over said graded interlayer a lower third solar subcell having a fourth band gap smaller than said second band gap such that said third subcell is lattice mismatched with respect to said second subcell;
mounting the first substrate and the sequence of epitaxial layers of semiconductor material on a flexible film;
mechanically holding said first substrate against a bottom support of an etching apparatus;
attaching a connecting link element that connects at least two opposed points on the periphery of the flexible film to an upper portion of the etching apparatus;
introducing said solar cell having said flexible film bonded thereon into an etchant environment in said etching apparatus;
etching said separation layer while applying mechanical tension to said connecting link element so as to remove said flexible film with said epitaxial layers from said first substrate;
attaching the flexible film directly to a surrogate substrate by an electrostatic technique;
depositing a contact metal layer over the semiconductor contact layer;
lithographically processing the contact metal layer to form grid lines;
attaching a cover glass over the grid lines; and
removing the surrogate substrate.
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Accused Products
Abstract
The present disclosure provides a process for manufacturing a solar cell by selectively freeing an epitaxial layer from a single crystal substrate upon which it was grown. In some embodiments the process includes, among other things, providing a first substrate; depositing a separation layer on said first substrate; depositing on said separation layer a sequence of layers of semiconductor material forming a solar cell; mounting and bonding a flexible support on top of the sequence of layers; etching said separation layer while applying an agitating action to the etchant solution so as to remove said flexible support with said epitaxial layer from said first substrate.
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Citations
20 Claims
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1. A method for manufacturing a solar cell using a process for selectively freeing an epitaxial layer from a single crystal substrate upon which it was grown, comprising:
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providing a first substrate of gallium arsenide; depositing a separation layer on said first substrate; depositing on the separation layer a sequence of epitaxial layers of semiconductor material forming a solar cell including;
forming over the separation layer an upper first solar subcell having a first band gap and including a semiconductor contact layer;
forming over said first solar subcell a middle second solar subcell having a second band gap smaller than said first band gap;
forming a graded interlayer over said second solar subcell; and
forming over said graded interlayer a lower third solar subcell having a fourth band gap smaller than said second band gap such that said third subcell is lattice mismatched with respect to said second subcell;mounting the first substrate and the sequence of epitaxial layers of semiconductor material on a flexible film; mechanically holding said first substrate against a bottom support of an etching apparatus; attaching a connecting link element that connects at least two opposed points on the periphery of the flexible film to an upper portion of the etching apparatus; introducing said solar cell having said flexible film bonded thereon into an etchant environment in said etching apparatus; etching said separation layer while applying mechanical tension to said connecting link element so as to remove said flexible film with said epitaxial layers from said first substrate; attaching the flexible film directly to a surrogate substrate by an electrostatic technique; depositing a contact metal layer over the semiconductor contact layer; lithographically processing the contact metal layer to form grid lines; attaching a cover glass over the grid lines; and removing the surrogate substrate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method for manufacturing a solar cell using a process for selectively freeing an epitaxial layer from a single crystal substrate upon which it was grown, comprising:
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providing a first substrate of gallium arsenide; depositing a separation layer having a thickness of approximately 50 Angstroms on said first substrate; depositing on the separation layer a sequence of epitaxial layers of semiconductor material forming a solar cell including; forming over the separation layer an upper first solar subcell composed of InGa(Al)P and having a first band gap and including a semiconductor contact layer; forming over said first solar subcell a middle second solar subcell composed of an GaAs, GaInP, GaInAs, GaAsSb, or GaInAsN emitter region and a GaAs, GaInAs, GaAsSb, or GaInAsN base region and having a second band gap smaller than said first band gap; forming a graded interlayer over said second solar subcell, wherein the graded interlayer is compositionally graded to lattice match the middle subcell on one side and the lower subcell on the other side, and is composed of (InxGa1-x)yAl1-yAs with x and y selected such that the band gap of the interlayer remains constant at approximately 1.5 eV throughout its thickness and greater than said second band gap; and forming over said graded interlayer a lower third solar subcell composed of an InGaAs base and emitter layer, or a InGaAs base layer and a InGaP emitter layer, and having a fourth band gap smaller than said second band gap such that said third subcell is lattice mismatched with respect to said second subcell; mounting the first substrate and the sequence of epitaxial layers of semiconductor material on a flexible film; mechanically holding said first substrate against a bottom support of an etching apparatus; attaching a connecting link element that connects at least two opposed points on the periphery of the flexible film to an upper portion of the etching apparatus; introducing said solar cell having said flexible film bonded thereon into an etchant environment with a liquid solution of hydrofluoric acid in said etching apparatus; etching said separation layer while applying mechanical tension to said connecting link element so as to remove said flexible film with said epitaxial layers from said first substrate, wherein the mechanical tension applied to said connecting link element allows said epitaxial layers and the surrogate substrate to curl upward, permitting the outdiffusion of reaction products of the etching process; attaching the flexible film directly to a surrogate substrate composed of GaAs, Ge, or Si by an electrostatic technique utilizing an electrostatic chuck; depositing a contact metal layer over the semiconductor contact layer; lithographically processing the contact metal layer to form grid lines; attaching a cover glass over the grid lines; and removing the surrogate substrate. - View Dependent Claims (16)
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17. A method for manufacturing a solar cell using a process for selectively freeing an epitaxial layer from a semiconductor substrate upon which it was grown, comprising:
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providing a first semiconductor substrate; depositing a separation layer on said first substrate; depositing a sequence of epitaxial layers of semiconductor material on the separation layer to form a multi junction solar cell; mounting the first substrate and the sequence of epitaxial layers of semiconductor material on a flexible film; mechanically holding said first substrate against a bottom support of an etching apparatus; attaching a connecting link element that connects at least two opposed points on the periphery of the flexible film to an upper portion of the etching apparatus; introducing said solar cell having said flexible film bonded thereon into an etchant environment in said etching apparatus; etching said separation layer while applying mechanical tension to said connecting link element so as to remove said flexible film with said epitaxial layers from said first substrate; attaching the flexible film directly to a surrogate substrate by an electrostatic technique; and removing the surrogate substrate. - View Dependent Claims (18, 19, 20)
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Specification