GaAs0.75P0.25 Directly Grown on Si Towards Cost-Effective High-Efficiency Multi-Junction Silicon Photovoltaics

The combination of III-V-based solar cells with a conventional silicon cell is a promising approach for the development of highly efficient and stable tandem photovoltaic devices. We present results from our ongoing efforts aimed at refining both the epitaxial process of nucleating GaP on Silicon and the GaAsxP1-x buffer structure that connect the silicon and GaAso, 75P0.25 cell. One focus is placed on the reduction of defects in the GaP nucleation layer with a stacking fault density of less than 2×105cm-2. To understand and reduce the formation of threading dislocations in the GaAsxP1-X buffer structure the defect density in the first layers is investigated and optimized. With the achieved improvements, a series of GaAso 75P0.25 cell structures has been grown on different buffer structures with a threading dislocation density of 7×106cm-2. Cells are processed with a novel low-cost mask and plate approach.