In this paper, we report on the conversion efficiency improvement in In0.50Ga0.50P/InxGa1-xAs tandem solar cells by employing metamorphic InGaAs bottom cell instead of lattice matched GaAs cell. In0.50Ga0.50P/In0.025Ga 0.975As and In0.50Ga0.50P/GaAs double junction solar cells were grown by low-pressure metalorganic chemical vapor deposition (LP-MOCVD) on GaAs substrates. High-resolution transmission electron microscopy (HR-TEM) measurement reveals the dislocation in the In0.025Ga 0 975As layer which is caused by the lattice mismatch between In 0.025Ga0.975As subcell and GaAs substrate. Conversion efficiencies of these cells were measured to be 24.37% and 25.11% (AM1.5, 1 sun, 25°C) for the Iri0.50Ga0.50P/GaAs and In 0.50Ga0.50P/In0.025Ga0.975As solar cells, respectively. The details about the solar cell characteristics will be discussed in the presentation.