III-V semiconductor interface with graded GeSn on silicon

1. A method of depositing III-V solar collection materials on a GeSn template on a silicon substrate comprising the steps of:

providing a crystalline silicon substrate;

epitaxially growing a graded single crystal GeSn layer on the silicon substrate using a grading profile to grade Sn through the layer, the graded single crystal GeSn layer having a thickness in a range of approximately 3 μm to approximately 5 μm, and

epitaxially growing a layer of III-V solar collection material on the graded single crystal GeSn layer, the graded single crystal GeSn layer including Sn up to an interface with the layer of III-V solar collection material.

2. A method as claimed in claim 1 wherein the grading profile includes starting the Sn at or near zero with the Ge at zero, varying the percentage of Sn to a maximum mid-area, and reducing the percentage of SN as the growth progresses.

3. A method of fabricating a solar cell on a silicon substrate comprising the steps of:

providing a crystalline silicon substrate;

epitaxially growing a graded single crystal GeSn layer on the silicon substrate using a grading profile to grade Sn through the layer, the graded single crystal GeSn layer having a thickness in a range of approximately 3 μm to approximately 5 μm;

epitaxially growing a single crystal layer of Ge on the graded single crystal GeSn layer;

epitaxially growing a single crystal layer of GeSn on the single crystal Ge layer; and

epitaxially growing a layer of single crystal III-V solar collection material on the single crystal layer of GeSn.

4. III-V solar collection material on a GeSn template comprising;

a crystalline silicon substrate;

a single crystal graded GeSn layer epitaxially grown on the silicon substrate, the Sn being graded through the layer, and the graded single crystal GeSn layer having a thickness in a range of approximately 3 μm to approximately 5 μm; and

a layer of III-V solar collection material epitaxially grown on the graded single crystal GeSn layer, the graded single crystal GeSn layer including Sn up to an interface with the layer of III-V solar collection material.

5. III-V solar collection material on a GeSn template as claimed in claim 4 wherein the graded single crystal GeSn layer starts with the Sn at or near zero with the Ge at zero, and the percentage of Sn varies to a maximum mid-area with the percentage of SN reducing as the growth progresses.

6. A solar collection device on a silicon substrate comprising;

a crystalline silicon substrate;

a graded single crystal GeSn layer epitaxially grown on the silicon substrate, the Sn being graded through the layer, and the graded single crystal GeSn layer having a thickness in a range of approximately 3 μm to approximately 5 μm;

a single crystal Ge layer epitaxially grown on the graded single crystal GeSn layer;

a single crystal GeSn layer epitaxially grown on the single crystal Ge layer; and

a layer of III-V solar collection material epitaxially grown on the single crystal GeSn layer.

7. A solar collection device on a silicon substrate as claimed in claim 6 wherein the graded single crystal GeSn layer starts with the Sn at or near zero with the Ge at zero, and the percentage of Sn varies to a maximum mid-area with the percentage of SN reducing as the growth progresses.

8. A solar collection device on a silicon substrate as claimed in claim 6 wherein the layer of III-V solar collection material includes InGaP.