Method for making thin film semiconductor, solar cell, and light emitting diode

Claim 1

A method for making a thin film semi-conductor comprising the steps of: providing a semi-conductor substrate having a surface; anodizing the semi-conductor substrate to provide a first porous layer adjacent the surface having a first porosity; anodizing the semi-conductor substrate to provide at least one second porous layer adjacent the first porous layer opposite the surface, each said second porous layer having a second porosity greater than said first porosity; forming a semi-conductor film on the first porous layer; and separating the semi-conductor film from the semi-conductor substrate along a line of relative weakness defined in or adjacent one of said second porous layers.

Claim 2

A method for making a thin film semi-conductor comprising the steps of: providing a semi-conductor substrate having a surface; anodizing the semi-conductor substrate at a first current density to provide a first porous layer adjacent the surface having a first porosity; anodizing the semi-conductor substrate at a second current density higher than said first current density to provide a second porous layer adjacent the, first porous layer opposite the surface, the second porous layer having a second porosity greater than the first porosity; anodizing the semi-conductor substrate at a third current density higher than said second current density to provide a third porous layer in or adjacent the second porous layer, the third porous layer having a third porosity higher than said second porosity; forming at least one semi-conductor film on the surface and first porous layer; and separating the semi-conductor film from the semi-conductor substrate along a line of relative weakness defined in the third porous layer or at or adjacent an interface defined between said third porous layer and the second porous layer.

Claim 17

A method for making a solar cell comprising the steps of: providing a semi-conductor substrate having a surface; forming a porous structure adjacent the surface of the substrate including a first porous layer adjacent the surface having a first porosity, a second porous layer adjacent the first porous layer opposite the surface having a second porosity greater than said first porosity and a third porous layer in or adjacent to the second porous layer having a third porosity greater than said second porosity; forming an epitaxially grown thin film semi-conductor structure on the surface including at least one hetero junction; forming a SiO 2 insulating layer on an exposed surface of the thin film semi-conductor structure; patterning and etching the insulating layer to define holes; depositing a metal film on the insulating layer to form a metal film layer; patterning and etching the metal film layer to form electrodes disposed in the holes; attaching elongate conductors having at least one extending end portion to the electrodes; attaching a support substrate to the surface overlying the electrodes and conductors with a binder material; and thereafter, separating the thin film semi-conductor structure and support substrate from the semi-conductor substrate along a line of relative weakness defined in the third porous layer or at or adjacent an interface defined between said third porous layer and the second porous layer.

Claim 23

A method for making a light emitting diode, comprising the steps of: providing a single crystal semi-conductor substrate doped with a first type of impurity having a surface; introducing in second type of impurity into said surface to define a surface layer doped with a second type of impurity adjacent the surface anodizing the surface layer to define a first porous layer having a first porosity along a surface of the surface layer; anodizing the substrate to form a second porous layer adjacent the first porosity layer and traversing the surface layer, and having a second porosity less than said first porosity; anodizing the substrate to form a third porous layer in the second porous layer, the third porous layer having a third porosity greater than the second porosity; providing a plurality of parallel spaced electrodes on said first porous layer; attaching a transparent support substrate to the surface and electrodes with a transparent binder material; separating the second porous layer from the semi-conductor substrate along a line of weakness defined in the third porous layer or at or adjacent and interface defined between said second porous layer and the third porous layer to form a separated LED substrate; providing a like second plurality of parallel spaced electrodes on an exposed surface of said second porous layer opposite the surface layer; attaching a second transparent support substrate to the exposed surface and electrodes with a transparent binder material to form an LED assembly; and thereafter, subdividing the LED assembly between the spaced electrodes to define a plurality of LED devices.