Lattice-matched GaP/SiGe virtual substrates for low-dislocation density GaInP/GaAsP/Si solar cells

Direct integration of GaP/Si must face a small, but non-negligible lattice constant mismatch, which due to thermal expansion differences between GaP and Si, reaches 0.5% at 900 K. This lattice mismatch results in the nucleation of misfit dislocations at the GaP/Si interface, requiring careful strain management and refinement of epitaxial processes. However, Si_0.88Ge_0.12 virtual substrates grown on Si provide a nearly ideal lattice-matched template for GaP epitaxy. This paper describes the successful heteroepitaxial integration of lattice-matched GaP/Si_0.88Ge_0.12/Si, based upon the previously-demonstrated methodology for successful GaP/Si integration, which provides a potential alternative pathway for low defect density III-V/Si multijunction photovoltaics, parallel to that of direct GaP/Si.