A p–i–n GaAs 0.75 P 0.19 N 0.06 structure lattice-matched to Si was realized on a 2-in. Si (001) substrate for monolithic tandem solar cells. The sample structure had mirror-like surfaces without any indication of pinholes or microcracks. X-ray diffraction results showed that all the layers were coherently grown on the Si substrate. Transmission electron microscopy results evidently showed that a dislocation-free device structure was grown on the Si substrate. Finally, current–voltage characteristics showed rectifying properties with low reverse saturation current, which was indicative of the high crystallinity of the device layer.